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  • 1. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    D-Egg: a dual PMT optical module for IceCube2023In: Journal of Instrumentation, E-ISSN 1748-0221, Vol. 18, no 4, article id P04014Article in journal (Refereed)
    Abstract [en]

    The D-Egg, an acronym for Dual optical sensors in an Ellipsoid Glass for Gen2, is one of the optical modules designed for future extensions of the IceCube experiment at the South Pole. The D-Egg has an elongated-sphere shape to maximize the photon-sensitive effective area while maintaining a narrow diameter to reduce the cost and the time needed for drilling of the deployment holes in the glacial ice for the optical modules at depths up to 2700 m. The D-Egg design is utilized for the IceCube Upgrade, the next stage of the IceCube project also known as IceCube-Gen2 Phase 1, where nearly half of the optical sensors to be deployed are D-Eggs. With two 8-inch high-quantum efficiency photomultiplier tubes (PMTs) per module, D-Eggs offer an increased effective area while retaining the successful design of the IceCube digital optical module (DOM). The convolution of the wavelength-dependent effective area and the Cherenkov emission spectrum provides an effective photodetection sensitivity that is 2.8 times larger than that of IceCube DOMs. The signal of each of the two PMTs is digitized using ultra-low-power 14-bit analog-to-digital converters with a sampling frequency of 240 MSPS, enabling a flexible event triggering, as well as seamless and lossless event recording of single-photon signals to multi-photons exceeding 200 photoelectrons within 10 ns. Mass production of D-Eggs has been completed, with 277 out of the 310 D-Eggs produced to be used in the IceCube Upgrade. In this paper, we report the design of the D-Eggs, as well as the sensitivity and the single to multi-photon detection performance of mass-produced D-Eggs measured in a laboratory using the built-in data acquisition system in each D-Egg optical sensor module.

  • 2. Abbasi, Rasha
    et al.
    Deoskar, Kunar
    Stockholm Univ, Oskar Klein Ctr, SE-10691 Stockholm, Sweden.
    Finley, Chad
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Limits on Neutrino Emission from GRB 221009A from MeV to PeV Using the IceCube Neutrino Observatory2023In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 946, no 1, article id L26Article in journal (Refereed)
    Abstract [en]

    Gamma-ray bursts (GRBs) have long been considered a possible source of high-energy neutrinos. While no correlations have yet been detected between high-energy neutrinos and GRBs, the recent observation of GRB 221009A-the brightest GRB observed by Fermi-GBM to date and the first one to be observed above an energy of 10 TeV-provides a unique opportunity to test for hadronic emission. In this paper, we leverage the wide energy range of the IceCube Neutrino Observatory to search for neutrinos from GRB 221009A. We find no significant deviation from background expectation across event samples ranging from MeV to PeV energies, placing stringent upper limits on the neutrino emission from this source.

  • 3.
    Abedi-Valugerdi, Manuchehr
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Mercury and silver induce B cell activation and anti-nucleolar autoantibody production in outbred mouse stocks: are environmental factors more important than the susceptibility genes in connection with autoimmunity?2009In: Clinical and Experimental Immunology, ISSN 0009-9104, E-ISSN 1365-2249, Vol. 155, no 1, p. 117-124Article in journal (Refereed)
    Abstract [en]

    Environmental and predisposing genetic factors are known to play a crucial role in the development of systemic autoimmune diseases. With respect to the role of environmental factors, it is not known how and to what extent they contribute to the initiation and exacerbation of systemic autoimmunity. In the present study, I considered this issue and asked if environmental factors can induce autoimmunity in the absence of specific susceptible genes. The development of genetically controlled mercury- and silver-induced B cell activation and anti-nucleolar autoantibodies (ANolA) production in genetically heterozygous outbred Institute of Cancer Research (ICR), Naval Medical Research Institute (NMRI) and Black Swiss mouse stocks were analysed. Four weeks of treatment with both mercury and silver induced a strong B cell activation characterized by increased numbers of splenic antibody-secreting cells of at least one or more immunoglobulin (Ig) isotype(s) in all treated stocks. The three stocks also exhibited a marked increase in the serum IgE levels in response to mercury, but not silver. More importantly, in response to mercury a large numbers of ICR (88%), NMRI (96%) and Black Swiss (100%) mice produced different levels of IgG1 and IgG2a ANolA (a characteristic which is linked strictly to the H-2 genes). Similarly, but at lower magnitudes, treatment with silver also induced the production of IgG1 and IgG2a ANolA in 60% of ICR, 75% of NMRI and 100% of Black Swiss mice. Thus, the findings of this study suggest that long-term exposure to certain environmental factors can activate the immune system to produce autoimmunity per se, without requiring specific susceptible genes.

  • 4.
    Agrawal, Vipin
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Physics.
    Pandey, Vikash
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Active buckling of pressurized spherical shells: Monte Carlo simulation2023In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 108, no 3, article id L032601Article in journal (Refereed)
    Abstract [en]

    We study the buckling of pressurized spherical shells by Monte Carlo simulations in which the detailed balance is explicitly broken—thereby driving the shell to be active, out of thermal equilibrium. Such a shell typically has either higher (active) or lower (sedate) fluctuations compared to one in thermal equilibrium depending on how the detailed balance is broken. We show that, for the same set of elastic parameters, a shell that is not buckled in thermal equilibrium can be buckled if turned active. Similarly a shell that is buckled in thermal equilibrium can unbuckle if sedated. Based on this result, we suggest that it is possible to experimentally design microscopic elastic shells whose buckling can be optically controlled.

  • 5. Ahari, Mostafa Tanhayi
    et al.
    Bandyopadhyay, Sumanta
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Washington University in St. Louis, USA.
    Nussinov, Zohar
    Seidel, Alexander
    Ortiz, Gerardo
    Partons as unique ground states of quantum Hall parent Hamiltonians: The case of Fibonacci anyons2023In: SciPost Physics, E-ISSN 2542-4653, Vol. 15, no 2, article id 043Article in journal (Refereed)
    Abstract [en]

    We present microscopic, multiple Landau level, (frustration-free and positive semi-definite) parent Hamiltonians whose ground states, realizing different quantum Hall fluids, are parton-like and whose excitations display either Abelian or non-Abelian braiding statistics. We prove ground state energy monotonicity theorems for systems with different particle numbers in multiple Landau levels, demonstrate S-duality in the case of toroidal geometry, and establish complete sets of zero modes of special Hamiltonians stabilizing parton-like states, specifically at filling factor ν=2/3. The emergent Entangled Pauli Principle (EPP), introduced in [Phys. Rev. B 98, 161118(R) (2018)] and which defines the "DNA" of the quantum Hall fluid, is behind the exact determination of the topological characteristics of the fluid, including charge and braiding statistics of excitations, and effective edge theory descriptions. When the closed-shell condition is satisfied, the densest (i.e., the highest density and lowest total angular momentum) zero-energy mode is a unique parton state. We conjecture that parton-like states generally span the subspace of many-body wave functions with the two-body M-clustering property within any given number of Landau levels, that is, wave functions with Mth-order coincidence plane zeroes and both holomorphic and anti-holomorphic dependence on variables. General arguments are supplemented by rigorous considerations for the M=3 case of fermions in four Landau levels. For this case, we establish that the zero mode counting can be done by enumerating certain patterns consistent with an underlying EPP. We apply the coherent state approach of [Phys. Rev. X 1, 021015 (2011)] to show that the elementary (localized) bulk excitations are Fibonacci anyons. This demonstrates that the DNA associated with fractional quantum Hall states encodes all universal properties. Specifically, for parton-like states, we establish a link with tensor network structures of finite bond dimension that emerge via root level entanglement.

  • 6.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    A Social Semiotic Approach to Teaching and Learning Science2018Conference paper (Other academic)
    Abstract [en]

    In this presentation I will discuss the application of social semiotics to the teaching and learning of university science. Science disciplines leverage a wide range of semiotic resources such as graphs, diagrams, mathematical representations, hands on work with apparatus, language, gestures etc. In my work I study how students learn to integrate these resources to do physics and what teachers can do to help them in this process. Over the years, a number of theoretical constructs have been developed within the Physics Education Research Group in Uppsala to help us to better understand the different roles semiotic resources play in learning university physics. In this presentation I will explain some of these terms and give examples of their usefulness for teasing out how learning is taking place.

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  • 7.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education.
    Building on higher education research - How can we take a scholarly approach to teaching and learning2018Conference paper (Other academic)
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  • 8.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Disciplinary Affordance vs Pedagogical Affordance: Teaching the Multimodal Discourse of University Science2017Conference paper (Other academic)
    Abstract [en]

    The natural sciences have been extremely successful in modeling some specific aspects of the world around us. This success is in no small part due to the creation of generally accepted, paradigmatic ways of representing the world through a range of semiotic resources. The discourse of science is of necessity multimodal (see for example Lemke, 1998) and it is therefore important for undergraduate science students to learn to master this multimodal discourse (Airey & Linder, 2009). In this paper, I approach the teaching of multimodal science discourse via the concept of affordance. Since its introduction by Gibson (1979) the concept of affordance has been debated by a number of researchers. Most famous, perhaps is the disagreement between Gibson and Norman (1988) about whether affordances are inherent properties of objects or are only present when perceived by an organism. More recently, affordance has been drawn on in the educational arena, particularly with respect to multimodality (see Fredlund, 2015 for a recent example). Here, Kress et al (2001) have claimed that different modes have different specialized affordances. In the presentation the interrelated concepts of disciplinary affordance and pedagogical affordance will be presented. Both concepts make a radical break with the views of both Gibson and Norman in that rather than focusing on the perception of an individual, they refer to the disciplinary community as a whole. Disciplinary affordance is "the agreed meaning making functions that a semiotic resource fulfills for a disciplinary community". Similarly, pedagogical affordance is "the aptness of a semiotic resource for the teaching and learning of some particular educational content" (Airey, 2015). As such, in a teaching situation the question of whether these affordances are inherent or perceived becomes moot. Rather, the issue is the process through which students come to use semiotic resources in a way that is accepted within the discipline. In this characterization then, learning can be framed in terms of coming to perceive and leverage the disciplinary affordances of semiotic resources. In this paper, I will discuss: the disciplinary affordances of individual semiotic resources, how these affordances can be made “visible” to students and how the disciplinary affordances of semiotic resources are ultimately leveraged and coordinated in order to make science meanings.

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  • 9.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    EMI, CLIL, EAP: What’s the difference?2018Conference paper (Other academic)
    Abstract [en]

    In this presentation I will examine the differences between the terms EMI (English Medium Instruction, CLIL (Content and Language Integrated Learning and EAP (English for Academic Purposes). I will also discuss what it means to become disciplinary literate in a first, second and third language.

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  • 10.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Learning and Sharing Disciplinary Knowledge: The Role of Representations2017Conference paper (Other academic)
    Abstract [en]

    In recent years there has been a large amount of interest in the roles that different representations (graphs, algebra, diagrams, sketches, physical models, gesture, etc.) play in student learning. In the literature two distinct but interrelated ways of thinking about such representations can be identified. The first tradition draws on the principles of constructivism emphasizing that students need to build knowledge for themselves. Here students are encouraged to create their own representations by working with materials of various kinds and it is in this hands-on representational process that students come to develop their understanding.

    The second tradition holds that there are a number of paradigmatic ways of representing disciplinary knowledge that have been created and refined over time. These paradigmatic disciplinary representations need to be mastered in order for students to be able to both understand and effectively communicate knowledge within a given discipline.

    In this session I would like to open up a discussion about how these two ways of viewing representations might be brought together. To do this I will first present some of the theoretical and empirical work we have been doing in Sweden over the last fifteen years. In particular there are three concepts that I would like to introduce for our discussion: critical constellations of representations, the disciplinary affordance of representations and the pedagogical affordance of representations.

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  • 11.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Research on physics teaching and learning, physics teacher education, and physics culture at Uppsala University2017Conference paper (Other academic)
    Abstract [en]

    This project compares the affordances and constraints for physics teachers’ professional identity building across four countries. The results of the study will be related to the potential consequences of this identity building for pupils’ science performance in school. The training of future physics teachers typically occurs across three environments, the physics department, the education department and school (during teaching practice). As they move through these three environments, trainees are in the process of building their professional identity. However, what is signalled as valuable for a future physics teacher differs considerably in different parts of the education. In educational research, professional identity has been used in a variety of ways (See for example overviews of the concept in Beauchamp & Thomas, 2009; and Beijaard, Meijer, & Verloop, 2004). In this project we draw on the work of Sfard and Pruzak (2005) who have defined identity as an analytical category for use in educational research. The project leverages this concept of identity as an analytical tool to understand how the value-systems present in teacher training environments and society as a whole potentially affect the future practice of trainee physics teachers. For identities to be recognized as professional they must fit into accepted discourses. Thus the project endeavours to identify discourse models that tacitly steer the professional identity formation of future physics teachers. Interviews will be carried out with trainee physics teachers and the various training staff that they meet during their education (physics lecturers, education lecturers, school mentors). It has been suggested that the perceived status of the teaching profession in society has a major bearing on the type of professional identity teachers can enact. Thus, in this project research interviews will be carried out in parallel across four countries with varying teacher status and PISA science scores: Sweden, Finland, Singapore and England. These interviews will be analysed following the design developed in a pilot study that has already carried out by the project group in Sweden. The research questions for the project are as follows: In four countries where the societal status of the teaching profession differs widely: What discourse models are enacted in the educational environments trainee physics teachers meet? What are the potential affordances and constraints of these discourse models for the constitution of physics teacher professional identities? In what ways do perceptions of the status assigned by society to the teaching profession potentially affect this professional identity building? What are the potential consequences of the answers to the above questions for the view of science communicated to pupils in school? In an extensive Swedish pilot study, four potentially competing discourse models were identified: these are: the critically reflective teacher, the practically well-equipped teacher, the syllabus implementer and the physics expert. Of these, the physics expert discourse model was found to dominate in both the physics department and amongst mentors in schools. In the physics expert discourse model the values of the discipline of physics dominate. Thus, the overarching goal of physics teaching is to create future physicists. In this model, the latest research in physics is seen as interesting and motivating, whereas secondary school subject matter is viewed as inherently unsophisticated and boring—something that needs to be made interesting. The model co-exists with the three other discourse models, which were more likely to be enacted in the education department. These other models value quite different goals such as the development of practical skills, reflective practice, critical thinking and citizenship. We claim that knowledge of the different discourse models at work in four countries with quite different outcomes on PISA science will useful in a number of ways. For teacher trainers, a better understanding of these models would allow informed decisions to be taken about the coordination of teacher education. For prospective teachers, knowledge of the discourse models at work during their education empowers them to question the kind of teacher they want to become.

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  • 12.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Semiotic Resources and Disciplinary Literacy2017Conference paper (Other academic)
    Abstract [en]

    In this research project we focused on the different semiotic resources used in physics (e.g. graphs, diagrams, language, mathematics, apparatus, etc.). We were interested in the ways in which undergraduate physics students learn to combine the different resources used in physics in order to become “disciplinary literate” and what university lecturers do to help their students in this process. Comparative data on the disciplinary literacy goals of physics lecturers for their students was collected at five universities in South Africa and four universities in Sweden.

    One of the main contributions of the project concerned what we termed the disciplinary affordance of a semiotic resource, that is, the specific meaning-making functions a particular resource plays for the discipline. We contrasted these meaning-making functions with the way that students initially viewed the same resource.

    We proposed two ways that lecturers can direct their students’ attention towards the disciplinary affordances of a given resource. The first involves unpacking the disciplinary affordance in order to create a new resource with higher pedagogical affordance. Our second proposal involved the use of systematic variation in order to help students notice the disciplinary relevant aspects of a given resource. A total of 19 articles/book chapters were published as a direct result of this funding.

  • 13.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Teaching and Learning with Disciplinary Resources2020Conference paper (Other academic)
    Abstract [en]

    In the creation and dissemination of knowledge, science disciplines use a wide range of disciplinary-specific resources such as graphs, diagrams, mathematical representations, hands on work with apparatus, technical language, etc. In my work I study how students experience such specialized resources and come to view them in the same way as experts in the field. In particular, I am interested in what we as university teachers can do to help students in this process. 

    In this presentation will use some examples from astronomy to illustrate a number of educational issues that can arise when teaching undergraduates using disciplinary-specific resources and discuss potential ways in which these issues can be addressed.

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  • 14.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    The Concept of Affordance in the Teaching and Learning of Undergraduate Science2018Conference paper (Other academic)
    Abstract [en]

    Since its introduction by Gibson (1979) the concept of affordance has been debated by a number of researchers. Most famous, perhaps is the disagreement between Gibson and Norman(1988) about whether affordances are inherent properties of objects or are only present when perceived by an organism. More recently, affordance has been drawn on in the educational arena, particularly with respect to multimodality (see Fredlund, 2015 for a recent example). 

    In the presentation the interrelated concepts of disciplinary affordance and pedagogical affordance will be presented. Both concepts make a radical break with the views of both Gibson and Norman in that rather than focusing on the perception of an individual, they refer to the disciplinary community as a whole. Disciplinary affordance is "the agreed meaning making functions that a semiotic resource fulfills for a disciplinary community". Similarly, pedagogical affordance is "the aptness of a semiotic resource for the teaching and learning of some particular educational content" (Airey, 2015). As such, in a teaching situation the question of whether these affordances are inherent or perceived becomes moot. Rather, the issue is the process through which students come to use semiotic resources in a way that is accepted within the discipline. In this characterization then, learning can be framed in terms of coming to perceive and leverage the disciplinary affordances of semiotic resources. 

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  • 15.
    Airey, John
    Stockholm University, Faculty of Humanities, Department of Teaching and Learning. Uppsala universitet, Fysikundervisningens didaktik.
    Thinking About English-Medium Instruction: Do We Need Everything Everywhere All at Once?2023Conference paper (Refereed)
    Abstract [en]

    Thinking About English-Medium Instruction: Do We Need Everything Everywhere All at Once? 

    Around the world, more and more university courses are being taught in English. Although there are sound economic, social and political reasons for this trend, many questions remain about the pedagogical effects of EMI at university level: How can teachers be prepared for EMI teaching? Will students cope? Are some forms of teaching less suited to EMI? Do different disciplines have different needs? Etc. etc.  In this workshop, I present some of the research I have carried out in Sweden that addresses these questions and make a number of recommendations.  I finish the workshop by proposing a disciplinary literacy discussion matrix (Airey, 2011) as a tool for carrying out disciplinary needs analysis for EMI.  

    References

    Airey, J. (2011). The disciplinary literacy discussion matrix: A heuristic tool for initiating collaboration in higher education. Across the disciplines, 8(3), 1-9.

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  • 16.
    Airey, John
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Using variation and unpacking to help students decode disciplinary-specific semiotic resources2018Conference paper (Other academic)
    Abstract [en]

    In this presentation I will describe a social semiotic approach (Halliday 1978; van Leeuwen 2005) to the multimodal teaching and learning of a discipline that takes variation theory (Marton & Booth 1997; Runesson 2005) as its theoretical framing. Following Airey and Linder (2017:95) I define social semiotics as “the study of the development and reproduction of specialized systems of meaning making in particular sections of society”

    Learning at university level involves coming to understand the ways in which disciplinary-specific semiotic resources can be coordinated to make appropriate disciplinary meanings (Airey & Linder 2009). Nowhere is this more true than in undergraduate physics where a particularly wide range of semiotic resources such as graphs, diagrams, mathematics and language are essential for meaning making.  In order to learn to make these disciplinary meanings, students need to discover the disciplinary affordances(Fredlund et al. 2012, 2014; Airey & Linder 2017) of the semiotic resources used in their discipline. 

    Fredlund et al. (2015) propose a three-stage process that lecturers can use to help their students:  

    1. Identify the disciplinary relevant aspects needed for a particular task. 

    2. Select semiotic resources that showcase these aspects. 

    3. Create structured variation within these semiotic resources to help students notice the disciplinary relevant aspects and their relationships to each other.

    However, many disciplinary specific semiotic resources have been rationalized to create a kind of disciplinary shorthand(Airey 2009). In such cases the disciplinary relevant aspects needed may no longer be present in resources used, but are rather implied. In such cases the resources will need to be unpacked for students (Fredlund et al. 2014).  Such unpacking increases the pedagogical affordance of semiotic resources but simultaneously decreases their disciplinary affordance. 

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  • 17.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Grundström Lindqvist, Josefine
    Kung, Rebecca
    What does it mean to understand a physics equation?: A study of undergraduate answers in three countries2017Conference paper (Other academic)
    Abstract [en]

    In this paper we are interested in how undergraduate students in the US, Australia and Sweden experience the physics equations they meet in their education. We asked over 350 students the same simple question: How do you know when you understand a physics equation? Students wrote free-text answers to this question and these were transcribed and coded. The analysis resulted in eight themes (significance, origin, describe, predict, parts, relationships, calculate and explain). Each of these themes represents a different disciplinary aspect of student understanding of physics equations. We argue that together the different aspects we find represent a more holistic view of physics equations that we would like all our students to experience. Based on this work we wondered how best to highlight this more holistic view of equations. This prompted us to write a set of questions that reflect the original data with respect to the eight themes. We suggest that when students are working with problem solving they may ask themselves these questions in order to check their holistic understanding of what the physics equations they are using represent. In continuing work we are asking the same question to a cohort of physics lecturers. We are also trialling the themes and related questions that we generated in teaching situations. Here we are interested in whether students perceive the questions as helpful in their learning.

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  • 18.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Grundström Lindqvist, Josefine
    Lippman Kung, Rebecca
    What Does It Mean to Understand a Physics Equation? A Study of Undergraduate Answers in Three Countries2019In: Bridging Research and Practice in Science Education: Selected Papers from the ESERA 2017 Conference / [ed] Eilish McLoughlin, Odilla E. Finlayson, Sibel Erduran, Peter E. Childs, Cham: Springer Nature, 2019, p. 225-239Chapter in book (Refereed)
    Abstract [en]

    As a discipline, physics is concerned with describing the world by constructing models, the end product of this modelling process often being an equation. As such, physics equations represent much more than a finalized, ready-to-use calculation package – to physicists they are the culmination of a whole range of actions, assump- tions, approximations and historical discoveries. Moreover, physics equations are not simply stand-alone entities, rather they are intimately bound up with other equa- tions. Together, this web of equations represents an integrated, coherent whole that signals the way the community of physicists view the world.

    Clearly, such a nuanced, expert-like understanding of physics equations is not spontaneously available to undergraduate physics students when they meet an equa- tion for the first time. In this respect, research suggests that we should not expect students to display conceptually coherent understanding across settings. Rather it has been suggested that understanding is built up from context-dependent knowl- edge in pieces (diSessa 1993, 2018). In this characterization, different aspects, or ways of viewing the same phenomenon, are leveraged in different settings. Students gradually develop their understanding in two ways: by forging links between these separate ‘pieces of knowledge’ and by coming to appreciate the usefulness of a given ‘piece of knowledge’ for a given task. Educationally then, we are interested in identifying these pieces of knowledge – in our case the range of ways that students understand equations. What are students’ default positions with respect to equa- tions? Which aspects of equations do students tend to focus on and which aspects tend to go unnoticed? Once we have documented the range of ways of understand- ing, the next task concerns how to help students discern other aspects of equations than those they may initially notice. Do the tasks that students are presented with in their undergraduate education encourage them to move towards a more nuanced, coherent, holistic understanding of physics equations?

  • 19.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden; Linnaeus University, Sweden.
    Larsson, Johanna
    Developing Students’ Disciplinary Literacy? The Case of University Physics2018In: Global Developments in Literacy Research for Science Education / [ed] Kok-Sing Tang, Kristina Danielsson, Springer, 2018, p. 357-376Chapter in book (Refereed)
    Abstract [en]

    In this chapter we use the concept of disciplinary literacy (Airey, 2011a, 2013) to analyze the goals of university physics lecturers. Disciplinary literacy refers to a particular mix of disciplinary-specific communicative practices developed for three specific sites: the academy, the workplace and society. It has been suggested that the development of disciplinary literacy may be seen as one of the primary goals of university studies (Airey, 2011a).

    The main data set used in this chapter comes from a comparative study of physics lecturers in Sweden and South Africa (Airey, 2012, 2013; Linder, Airey, Mayaba, & Webb, 2014). Semi-structured interviews were carried out using a disciplinary literacy discussion matrix (Airey, 2011b), which enabled us to probe the lecturers’ disciplinary literacy goals in the various semiotic resource systems used in undergraduate physics (i.e. graphs, diagrams, mathematics, language).

    The findings suggest that whilst physics lecturers have strikingly similar disciplinary literacy goals for their students, regardless of setting, they have very different ideas about whether they themselves should teach students to handle these disciplinary-specific semiotic resources. It is suggested that the similarity in physics lecturers’ disciplinary literacy goals across highly disparate settings may be related to the hierarchical, singular nature of the discipline of physics (Bernstein, 1999, 2000).

    In the final section of the chapter some preliminary evidence about the disciplinary literacy goals of those involved in physics teacher training is presented. Using Bernstein’s constructs, a potential conflict between the hierarchical singular of physics and the horizontal region of teacher training is noticeable.

    Going forward it would be interesting to apply the concept of disciplinary literacy to the analysis of other disciplines—particularly those with different combinations of Bernstein’s classifications of hierarchical/horizontal and singular/region.

  • 20.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Larsson, Johanna
    Linder, Anne
    Investigating Undergraduate Physics Lecturers’ Disciplinary Literacy Goals For Their Students2017Conference paper (Other academic)
    Abstract [en]

    In this presentation we use the concept of disciplinary literacy (Airey, 2011a; 2013) to analyse the expressed learning goals of university physics lecturers for their students. We define disciplinary literacy in terms of learning to control a particular set of multimodal communicative practices. We believe it is important to document the expressed intentions of lecturers in this way, since it has previously been suggested that the development of such disciplinary literacy may be seen as one of the primary goals of university studies (Airey, 2011a).

    The main data set used in this presentation comes from a comparative study of 30 physics lecturers from Sweden and South Africa. (Airey, 2012, 2013; Linder et al, 2014). Semi-structured interviews were carried out using a disciplinary literacy discussion matrix (Airey, 2011b), which enabled us to probe the lecturers’ disciplinary literacy goals in the various semiotic resource systems used in undergraduate physics (e.g. graphs, diagrams, mathematics, spoken and written languages, etc.).

    The findings suggest that physics lecturers in both countries have strikingly similar disciplinary literacy goals for their students and hold similar beliefs about disciplinary semiotic resources. The lecturers also agree that teaching disciplinary literacy ought not to be their job. Here though, there were differences in whether the lecturers teach students to handle disciplinary-specific semiotic resources. These differences appear to be based on individual decisions, rather than being specific to a particular country or institution.

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  • 21.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Linder, Cedric
    Social Semiotics in University Physics Education2017In: Multiple Representations in Physics Education / [ed] David F. Treagust, Reinders Duit, Hans E. Fischer, Springer, 2017, p. 95-122Chapter in book (Refereed)
    Abstract [en]

    In this chapter we discuss the application of social semiotics to the teaching and learning of university physics. Social semiotics is a broad construct where all communication in a particular social group is realized through the use of semiotic resources. In the discipline of physics, examples of such semiotic resources are graphs, diagrams, mathematics, spoken and written language, and laboratory apparatus. In physics education research it is usual to refer to most of these semiotic resources as representations. In social semiotics, then, disciplinary learning can be viewed as coming to interpret and use the meaning potential of disciplinary-specific semiotic resources (representations) that has been assigned by the discipline. We use this complementary depiction of representations to build theory with respect to the construction and sharing of disciplinary knowledge in the teaching and learning of university physics. To facilitate both scholarly discussion and future research in the area, a number of theoretical constructs have been developed. These constructs take their point of departure in empirical studies of teaching and learning in undergraduate physics. In the chapter we present each of these constructs in turn and examine their usefulness for problematizing teaching and learning with multiple representations in university physics.

  • 22.
    Airey, John
    et al.
    Stockholm University, Faculty of Humanities, Department of Teaching and Learning.
    Patron, Emelie
    Linnéuniversitet.
    Wikman, Susanne
    Linnéuniversitet.
    Making the Invisible Visible: The role of undergraduate textbooks in the teaching and learning of physics and chemistry2023Conference paper (Refereed)
    Abstract [en]

    As disciplines, undergraduate physics and chemistry leverage a particularly wide range of semiotic systems (modes) in order to create and communicate their scientific meanings. Examples of the different semiotic systems employed are: spoken and written language, mathematics, chemical formulae, graphs, diagrams, sketches, computer simulations, hands-on work with experimental apparatus, computer simulations, etc. Individual semiotic resources within this range of semiotic systems are coordinated in specific constellations (Airey & Linder, 2009) in order to mediate scientific knowledge. In this Swedish Research Council project, we are interested in the representation of scientific phenomena that cannot be seen. The question we pose is: How is scientific knowledge mediated when we cannot directly interact with the phenomena in question through our senses?  We adopt a social semiotic approach (Airey & Linder, 2017; van Leeuwen, 2005), to investigate the ways in which two phenomena—electromagnetic fields and chemical bonds—are presented in undergraduate textbooks. To do this we carried out a semiotic audit (Airey & Erikson, 2019) of eight textbooks (four in each discipline). We note that the individual resources used have a mixture of affordances—whilst the majority retain high disciplinary affordance, others are unpacked (Patron et al. 2021) providing higher pedagogical affordance. We discuss the ways in which the resources have been combined and orchestrated (Bezemer & Jewitt, 2010) in order to attempt to make visible that which is invisible, and identify a number of potential problems. In earlier work, Volkwyn et al. (2019) demonstrated how experimental work with physics devices can make the Earth’s magnetic field accessible to students through chains of transduction. Thus, we propose that encouraging transductions across the semiotic resource systems provided in textbooks may help students to experience the invisible.

    References

    Airey, J. (2006). Physics students' experiences of the disciplinary discourse encountered in lectures in English and Swedish (Licentiate dissertation, Department of Physics, Uppsala University).

    Airey, J. (2009). Science, language, and literacy: Case studies of learning in Swedish university physics (Doctoral dissertation, Acta Universitatis Upsaliensis).

    Airey, J. (2015). Social Semiotics in Higher Education: Examples from teaching and learning in undergraduate physics. In In: SACF Singapore-Sweden Excellence Seminars, Swedish Foundation for International Cooperation in Research in   Higher Education (STINT) , 2015 (pp. 103). 

    Airey, J., & Eriksson, U. (2019). Unpacking the Hertzsprung-Russell diagram: A social semiotic analysis of the disciplinary and pedagogical affordances of a central resource in astronomy. Designs for Learning, 11(1), 99-107.

    Goodwin, C. (2015). Professional vision. In Aufmerksamkeit: Geschichte-Theorie-Empirie (pp. 387-425). Wiesbaden: Springer Fachmedien Wiesbaden.

    O’Halloran, K. (2007). Mathematical and scientific forms of knowledge: A systemic functional multimodal grammatical approach. language, Knowledge and pedagogy: functional linguistic and sociological perspective, 205-236.

    Patron, E. (2022). Exploring the role that visual representations play when teaching and learning chemical bonding: An approach built on social semiotics and phenomenography(Doctoral dissertation, Linnaeus University Press).

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  • 23.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Simpson, Zachary
    Multimodal Science and Engineering Teaching: Perspectives from 8ICOM2018Conference paper (Other academic)
    Abstract [en]

    The previous international conference on multimodality – 8ICOM – featured two sessions devoted to multimodal, social semiotic approaches to science teaching and learning (c.f. Halliday1978; van Leeuwen 2005, Airey & Linder 2017). What the papers in these sessions shared was the argument that such perspectives on science, and science teaching, can, at least in part, respond to calls to ‘democratize’ science education by recognising diverse sets of semiotic resources and, in so doing, seeking to address impediments to equal participation (Burke et al., 2017). 

    The 8ICOM science sessions were particularly noteworthy given the backdrop against which 8ICOM had been organised. In the months leading up to the conference, South Africa (and Cape Town, in particular) had experienced campus unrest aimed at ‘decolonizing’ higher education in that country. As part of this movement, the phrase #ScienceMustFall briefly trended on social media. This emanated from the claim that ‘science’ is a western, colonial construct that needs to be dismantled and replaced with the teaching of indigenous, African knowledge. Although the #ScienceMustFall slogan has since departed from the wider public consciousness, the questions it raises nonetheless remain: why, and how, should science be taught?  Is science more than just a western colonial construction and, if so, why? And, what can the concept of multimodality offer by way of answering these questions? 

    In this paper, we offer an overview of the multimodal science papers presented in the two sessions at 8ICOM in the light of these questions. This is done with a view to assessing where the multimodality community finds itself regarding science education, and how it might address questions of the legitimacy of western science in the future. It is thus an attempt, as the conference theme suggests, to ‘move the theory forward’.      

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  • 24.
    Allan, Dan
    Stockholm University, Faculty of Science, Department of Physics.
    Time-Optimal Charging Processes for Quantum Batteries2020Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    We examine time-optimal processes of charging a quantum battery from an initial state to a maximally energetic state through unitary dynamics. We assume that the dynamics are restricted by one of two constraints, the bounded bandwidth or bounded variance constraints. We calculate lower bounds on the charging time for both constraints in the form of quantum speed limits. For the bounded bandwidth constraint we also find the minimal charging time for a large class of systems. In the bounded variance case we present current results in terms of properties of the dynamics. Lastly we examine how time-optimal processes are influenced when multiple batteries are allowed to interact and correlate. We explicitly calculate the charging time for a certain class of systems, and we find that it is decreased if we allow correlation between batteries.

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  • 25.
    Almhagen, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Development and validation of a scanned proton beam model for dose distribution verification using Monte Carlo2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
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  • 26.
    Almhagen, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Development and validation of a scanned proton beam model for dose distribution verification using Monte Carlo2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background and purpose: Although proton therapy is becoming increasingly common as a radiotherapy modality, facilities offering proton therapy are still scarce in comparison to photon therapy. Sweden's new proton therapy facility, Skandionkliniken, is scheduled to being operation during August 2015, employing the pencil beam scanning technique. Given Skandionklinikens unique stance as the only facility offering proton therapy in Sweden as of this writing, it is important to minimize the need for measurements during quality assurance to free up beam time for patients and other endeavors. It is the purpose of this work to create a foundation for a method whereby dose distribution verification is done via Monte Carlo simulation by developing and performing simple validation of a beam model. As input for simulating a dose distribution, log files storing a wide variety of data on how the dose distribution was delivered were used.

    Method: GATE, an open source Monte Carlo code and built on top of Geant4, was used for all simulations. A beam model parameterizing phase space at the nozzle exit was developed. The beam model development process made use of the beam data library and log file data. Using an in house developed code to convert log file data to treatment plans readable by GATE allowed simulation of delivered dose distributions. For validation, gamma index tests were performed comparing measured and simulated dose distributions.

    Results: The beam model was found able to predict the spot size in almost all cases within 0.2 mm. Likewise, the beam model was able to predict the proton range within 0.2 mm. The energy spread was found to be more difficult to estimate; comparisons of simulated and measured curves for at six points around the Bragg peak yielded a maximum deviation of 0.86 mm. Several difficulties prevented easy interpretation of the results of the gamma index tests. If allowance is made for certain data manipulation, pass rates of 90% or above using the global method can be achieved for all depths and for both treatment plans scanned.

    Conclusion: Although some complications arose during validation, the beam model performance appears capable of producing accurate results. To produce a full product suitable for routine patient specific quality assurance, further work will be necessary. Significant computing power would also be mandatory for routine use, necessitating the acquisition of a dedicated computer cluster or using GPUs.

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  • 27.
    Alpsten, Freja
    Stockholm University, Faculty of Science, Department of Physics.
    Investigation of a Collapsed Cone Superposition Algorithm for dosimetry in brachytherapy2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background & Purpose: The current standard dosimetry in brachytherapy treatment planning, the TG-43 formalism, ignore the presence of non-water media and finite patient dimensions. This can cause clinically relevant errors in dose estimates. To over- come the limitations of the TG-43 formalism, Model-Based Dose Calculation Algorithms (MBDCAs) have evolved. One of the commercial available MBDCAs is the Advanced Collapsed cone Engine (ACE) by Elekta. In ACE, the total dose is divided into three components, the primary, the first-scattered and the multiple-scattered dose, where the two last mentioned are calculated by the means of the Collapsed Cone Algorithm.

    In this study the performance of ACE has been investigated. The study has been di- vided into 2 parts, where the aim of part 1 was to analyze the relationship between the so called discretization artifacts, caused by the collapsed cone approximation, and the number of dwell positions. The severeness of the artifact is thought to decrease as the number of dwell positions are increased. The second part focus on ACE’s behavior in cortical bone, with the aim to form a hypothesis (explanation and solution) to the previously observed dose underestimation of the dose to bone made by ACE.

    Materials and Methods: The generic 192Ir source, the Oncentra Brachy (OcB) treatment planning system (TPS) and the Monte Carlo (MC) platform ALGEBRA have been utilized. In the first part of the study, six source configurations, all with a different number of dwell positions, were created and placed in the center of large water phantoms, i.e. under TG-43 conditions in which the TG-43 formalism can be assumed to yield a high accuracy of the estimated dose. The accuracy of ACE has been judged by its’ deviation from TG-43.

    In the second part of the study, a cubic source configuration, of 27 dwell positions, was positioned at the center of a cubic water phantom. Three cases where constructed, with a small cortical bone heterogeneity positioned at different distances from the source configu- ration. The ACE calculated dose distribution has been divided into its’ three constituents. The accuracy of ACE and TG-43 has been judged by its’ deviation from MC.

    Results: Part 1 showed that increasing the number of dwell positions does not guar- antee an improved accuracy of ACE. Local dose difference ratios of > 2%, caused by the artifacts, were mainly located outside the 5% isodose line. A general dose underestima- tion was observed in ACE, with an increased magnitude as the dose level decreased. The majority of local dose difference ratios below -4% were found where the multi-resolution voxelization grid of ACE has a voxel size of ≥23 mm3, that is at a distance of ≥8 cm from the closest dwell position when using the ACE standard accuracy level.

    In part 2, ACE underestimated the dose to cortical bone, with an increased magnitude as the bone was positioned farther away from the source configuration. The TG-43 formalism gave slightly better estimates of the mean dose to bone than ACE, especially at higher dose levels. For a mean dose to the cortical bone heterogeneity equal to 45% of the prescribed dose, TG-43 and ACE underestimated the mean dose with 1% and 4%, respectively. The estimated mean dose to a volume located directly behind the heterogeneity agreed within 1% between ACE and MC. However, an increased amount of positive local dose difference ratios were observed in this volume.

    Conclusions: Increasing the number of dwell positions cause a ”blurring” effect of the artifact, but may also increase the fluence gradient. In such situations the severeness of the artifact may not be improved. In patient cases the dwell positions are usually added in a more random manner which may favor the ”blurring effect”.

    The underestimations observed in ACE are thought to be caused by both the multiple- resolution voxelization grid of ACE and the relationship between the dimensions of the phantom in which the multiple-scattered kernel has been generated and the current calcu- lation volume.

    ACE was unsuccessful to predict the dose to cortical bone, and should hence be used with caution when cortical bone is an organ at risk, as long as the problem remains. The results indicates that the error in ACE is located in the scatter dose calculations and that the heterogeneity cause ACE to displace the dose.

    The error is thought to be located in the multiple-scattered dose component, which was also shown by Terribilni et al.. A hypothesis is that the problem is caused by the neglected effect of media dependent absorption coefficients in the multiple-scattered dose calculation. A suggested solution, left to be proven, is to use effective attenuation scaling factors.

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  • 28.
    Amann, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Degerman, David
    Stockholm University, Faculty of Science, Department of Physics.
    Lee, Ming-Tao
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Shipilin, Mikhail
    Stockholm University, Faculty of Science, Department of Physics.
    Wang, Hsin-Yi
    Stockholm University, Faculty of Science, Department of Physics.
    Cavalca, Filippo
    Weston, Matthew
    Stockholm University, Faculty of Science, Department of Physics.
    Gladh, Jörgen
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Schlueter, Christoph
    Drube, Wofgang
    Lömker, Patrick
    Ederer, Katrin
    Noei, Heshmat
    Zehetner, Johann
    Wentzel, Henrik
    Åhlund, John
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    A dedicated photoelectron spectroscopy instrument for studies of catalytic reactions at pressures exceeding 1 barManuscript (preprint) (Other academic)
    Abstract [en]

    Here, we present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures exceeding 1 bar. The instrument builds around the concept of a “virtual cell” in which a gasflow is directed onto the sample surface creating a local high pressure on top of the sample. This allows the instrument to maintain a low pressure of a few mbars in the main chamber, while simultaneously keeping a local pressure of around 1 bar. Synchrotron radiation based grazing incidence photoemission within ± 5° is used to enhance the surface sensitivity in the experiment. The aperture, separating the high-pressure region from the differential pumping of the electron spectrometer, consists of multiple, evenly spaced, mm sized holes matching the footprint of the x-ray beam on the sample surface. As the photo-emitted electrons are subject to strong scattering in the gas phase and the resulting signal is therefore highly dependent on the sample to aperture distance, the latter is controlled with high precision using a fully integrated manipulator that allows for sample movement with step sizes of 10 nm between 0 and –5 mm with very low vibrational amplitude. The instrumental features allows acquisition of metallic bulk spectra at He pressures up to 2.5 bar and also allows for following C1s spectra under realistic gas mixtures of CO + H2with various temperatures up to 500°C. This capability opens for studies of catalytic reactions in operandi.

  • 29. Anderson, E. K.
    et al.
    Bertsche, W.
    Fajans, J.
    Hangst, J. S.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Wurtele, J. S.
    Observation of the effect of gravity on the motion of antimatter2023In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 621, no 7980, p. 716-722Article in journal (Refereed)
    Abstract [en]

    Einstein’s general theory of relativity from 1915 remains the most successful description of gravitation. From the 1919 solar eclipse to the observation of gravitational waves, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac’s theory appeared in 1928; the positron was observed in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive ‘antigravity’ is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

  • 30.
    Andersson, David
    Stockholm University, Faculty of Science, Department of Physics.
    On the Evolving Friction of Layered Materials and the Prospect of Their Image Reconstruction2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The scope of this licentiate thesis is twofold: 1. Investigate the frictional properties of systems with layered materials; 2. Employing image recognition algorithms to find the substrates in AFM experiments. As of today, there is a clear dichotomy separating these projects, however, it is the long term goal that they should coalesce in a not too distance future. The friction in layered materials projects is already finished, in this project we expanded the venerated Prandtl-Tomlison model to incorporate atomically thin layered materials such as graphene. This project has proved successful beyond our expectations, and a score of experimental results and conflicts in the field can be explained and resolved using our model. The image reconstruction project however, is still on a basic level. So far we have compared a standard model – Histogram Analysis Method– for image reconstruction on the nano-level with a popular image reconstruction algorithm –Lucy Richardson Deconvolution – from astronomy and shown that the latter is more suitable for these kind of systems. However, this project is far from finished, and the results in this part should be regarded as both partial and preliminary.

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  • 31.
    Andersson, Ole
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Badziąg, Piotr
    Stockholm University, Faculty of Science, Department of Physics.
    Dumitru, Irina
    Stockholm University, Faculty of Science, Department of Physics.
    Cabello, Adán
    Device-independent certification of two bits of randomness from one entangled bit and Gisin's elegant Bell inequality2018In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 97, no 1, article id 012314Article in journal (Refereed)
    Abstract [en]

    We prove that as conjectured by Acín et al. [Phys. Rev. A 93, 040102(R) (2016)], two bits of randomness can be certified in a device-independent way from one bit of entanglement using the maximal quantum violation of Gisin's elegant Bell inequality. This suggests a surprising connection between maximal entanglement, complete sets of mutually unbiased bases, and elements of symmetric informationally complete positive operator-valued measures, on one side, and the optimal way of certifying maximal randomness, on the other.

  • 32.
    Andisheh, Bahram
    Stockholm University, Faculty of Science, Department of Physics.
    Improving the therapeutic ratio of stereotactic radiosurgery and radiotherapy2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    New methods of high dose delivery, such as intensity modulated radiation therapy (IMRT), stereotactic radiation therapy (SRT) or stereotactic radiosurgery (SRS), hadron therapy, tomotherapy, etc., all make use of a few large fractions. To improve these treatments, there are three main directions: (i) improving physical dose distribution, (ii) optimizing radiosurgery dose-time scheme and (iii) modifying dose response of tumors or normal tissues.

    Different radiation modalities and systems have been developed to deliver the best possible physical dose to the target while keeping radiation to normal tissue minimum. Although applications of radiobiological findings to clinical practice are still at an early stage, many studies have shown that   sublethal radiation damage repair kinetics plays an important role in tissue response to radiation.

    The purpose of the present thesis is to show how the above-mentioned directions could be used to improve treatment outcomes with special interest in radiation modalities and dose-time scheme, as well as radiobiological modeling. Also for arteriovenous malformations (AVM), the possible impact of AVM network angiostructure in radiation response was studied.

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  • 33.
    Ardenfors, Oscar
    Stockholm University, Faculty of Science, Department of Physics.
    Out-of-field doses from proton therapy and doses from CBCT imaging: Risk of radiation-induced second cancer from modern radiotherapy2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of ionizing radiation for treatment of cancer diseases is continuously increasing as patient survival is improving and new treatment techniques are emerging. While this development is beneficial for curing primary tumors, concerns have been raised regarding the unwanted dose contribution to healthy tissues of patients and the associated risk of radiation-induced second cancer (RISC). This is especially important for younger patients receiving radiotherapy more often than before and for whom the risk of developing RISC is elevated in comparison to the typical adult radiotherapy patient. In order to estimate the risk of RISC associated with modern radiotherapy and imaging, the associated radiation doses must be determined.

    Patients undergoing radiotherapy receive in-field doses from the primary beam but also out-of-field doses originating from secondary radiation produced in the beamline and within the patient. Over the last years, the use of proton pencil beam scanning (PBS) therapy has rapidly increased due to its potential to reduce the in-field doses to healthy tissues in comparison to photon therapy. One of the drawbacks with proton therapy is the production of neutrons capable of travelling large distances and depositing out-of-field doses to organs located far from the primary treatment field. The dose reduction associated with proton PBS therapy could consequently be affected by the out-of-field doses originating from secondary radiation.

    The sharp dose gradients associated with modern treatment techniques, such as photon intensity-modulated radiotherapy (IMRT) and proton PBS therapy require more frequent and accurate patient imaging in comparison to conventional treatment techniques such as three-dimensional conformal radiotherapy (CRT). Setup verification images could be acquired with cone-beam computed tomography (CBCT) producing three-dimensional patient images at the cost of an increased patient dose in comparison to planar x-ray imaging. Concerns have been raised regarding the cumulative patient doses from repeated CBCT imaging versus the dose-saving benefits associated with modern radiotherapy techniques like IMRT and proton PBS.

    In this thesis, a study on the in-field and out-of-field doses to healthy tissues from photon IMRT and CRT treatments of head and neck tumors showed that the risk of RISC was unaffected by the employed treatment technique and indicated that the lifetime risk of cancer induction was of the order of 1-2%.

    Results from measurements and Monte Carlo simulations showed that the out-of-field absorbed doses and equivalent doses associated with proton PBS treatments of brain tumors were up to 60 µGy/Gy and 150 µSv/Gy, respectively. The risk of RISC associated with these out-of-field doses was in the range of approximately one induced cancer in ten thousand treated patients. A simulation study on the doses from a proton gantry-mounted CBCT system showed that repeated CBCT imaging could result in cumulative organ doses of almost 2 Gy. The conclusion from these studies is that the dose-sparing effects of proton PBS therapy are not overshadowed by the out-of-field doses originating from secondary radiation for brain tumor treatments, but that the cumulative doses from repeated CBCT imaging could have a relevant impact on the overall dose reduction.

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    Out-of-field doses from proton therapy and doses from CBCT imaging
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  • 34.
    Ardenfors, Oscar
    Stockholm University, Faculty of Science, Department of Physics.
    Secondary doses to healthy tissues from radiotherapy and modern imaging techniques2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of ionizing radiation for treatment of cancer diseases is continuously increasing giving rise to several new questions and concerns. One of the most important aspects of this is the associated dose imparted to healthy tissues. This unwanted dose contribution is a result of both radiotherapy procedures and diagnostic imaging. The dose deposition in healthy tissues from external radiotherapy mainly originates from the incident primary beam. However, the patient also receives non-negligible organ doses originating from secondary radiation produced in the treatment machine and within the patient. This secondary radiation, especially neutrons, can travel large distances and consequently deposit doses to organs located far from the primary treatment field. The dose contribution to healthy organs from diagnostic procedures is growing due to the increase in repeated imaging performed in conjunction with radiotherapy. Also, patients undergoing both external radiotherapy and radionuclide therapy with radioactive isotopes could receive a high combined dose burden to healthy tissues.

    The need to quantify the secondary dose contribution and the associated risk of radiation-induced cancer is a relevant matter as new techniques are continuously emerging both in the field of radiotherapy and imaging. The technical advances in modern treatment techniques such as intensity modulated radiotherapy, rotational therapy and ion therapy have contributed to the overall increase in patient survival. A parallel development in medical imaging has caused an increase in the use of cone-beam computed tomography for repeated image-guidance imaging providing better tumor localization and a reduction in high doses deposited in adjacent healthy tissues.

    The most accurate way of estimating the risk of radiation-induced secondary cancers is to conduct comprehensive epidemiological studies on an exposed population stretching over several decades. This has been done in the past using cohorts of survivors of the atomic bombings and other nuclear accidents and medical exposures. However, the implementation of these epidemiological data is complex as the types of exposure differ greatly from modern radiotherapy procedures. Also, the long latency associated with radiation-induced secondary cancers further complicate the use of epidemiological data.

    Thus, the goal of achieving a dose-response relationship for secondary cancers is not only a matter of assessing the dose to the patient but also on how this data should be analyzed. Today, the most popular way of achieving this is through theoretical risk models using patient-specific parameters including dose distributions and risk coefficients obtained for populations from epidemiological studies.

    Due to the difficulties associated with performing measurements of radiation-induced organ doses from treatment and imaging, the dose is often calculated either analytically using an algorithm employed in the clinical treatment planning system or through Monte Carlo simulations that offer the most accurate tool for such calculations. To allow for accurate Monte Carlo simulations of secondary radiation from external radiotherapy the beam model should be validated against measurements with regard to both the primary beam and the out-of-field secondary radiation.

    These aspects have been investigated in individual studies that make the object of the articles included in this thesis. Paper I presents a literature review of secondary doses from different treatment and imaging modalities. Paper II shows a comparison between the risks of radiation-induced cancer for patients treated for head and neck cancer using two different treatment techniques. Paper III deals with Monte Carlo simulations of doses to healthy tissues from radionuclide therapy given in conjunction with external radiotherapy. Paper IV presents the validation of a proton spot scanning Monte Carlo model.

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  • 35.
    Ardenfors, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Dasu, Alexandru
    Kopeć, Mariusz
    Gudowska, Irena
    Stockholm University, Faculty of Science, Department of Physics.
    Modelling of a proton spot scanning system using MCNP62017In: International Nuclear Science and Technology Conference, Institute of Physics (IOP), 2017, article id 012025Conference paper (Refereed)
    Abstract [en]

    The aim of this work was to model the characteristics of a clinical proton spot scanning beam using Monte Carlo simulations with the code MCNP6. The proton beam was defined using parameters obtained from beam commissioning at the Skandion Clinic, Uppsala, Sweden. Simulations were evaluated against measurements for proton energies between 60 and 226 MeV with regard to range in water, lateral spot sizes in air and absorbed dose depth profiles in water. The model was also used to evaluate the experimental impact of lateral signal losses in an ionization chamber through simulations using different detector radii. Simulated and measured distal ranges agreed within 0.1 mm for R90 and R80 , and within 0.2 mm for R50 . The average absolute difference of all spot sizes was 0.1 mm. The average agreement of absorbed dose integrals and Bragg-peak heights was 0.9%. Lateral signal losses increased with incident proton energy with a maximum signal loss of 7% for 226 MeV protons. The good agreement between simulations and measurements supports the assumptions and parameters employed in the presented Monte Carlo model. The characteristics of the proton spot scanning beam were accurately reproduced and the model will prove useful in future studies on secondary neutrons.

  • 36. Arun, K. G.
    et al.
    Belgacem, Enis
    Benkel, Robert
    Bernard, Laura
    Berti, Emanuele
    Bertone, Gianfranco
    Besancon, Marc
    Blas, Diego
    Böhmer, Christian G.
    Brito, Richard
    Calcagni, Gianluca
    Cardenas-Avendaño, Alejandro
    Clough, Katy
    Crisostomi, Marco
    De Luca, Valerio
    Doneva, Daniela
    Escoffier, Stephanie
    Ezquiaga, José María
    Ferreira, Pedro G.
    Fleury, Pierre
    Foffa, Stefano
    Franciolini, Gabriele
    Frusciante, Noemi
    García-Bellido, Juan
    Herdeiro, Carlos
    Hertog, Thomas
    Hinderer, Tanja
    Jetzer, Philippe
    Lombriser, Lucas
    Maggio, Elisa
    Maggiore, Michele
    Mancarella, Michele
    Maselli, Andrea
    Nampalliwar, Sourabh
    Nichols, David
    Okounkova, Maria
    Pani, Paolo
    Paschalidis, Vasileios
    Raccanelli, Alvise
    Randall, Lisa
    Renaux-Petel, Sébastien
    Riotto, Antonio
    Ruiz, Milton
    Saffer, Alexander
    Sakellariadou, Mairi
    Saltas, Ippocratis D.
    Sathyaprakash, B. S.
    Shao, Lijing
    Sopuerta, Carlos F.
    Sotiriou, Thomas P.
    Stergioulas, Nikolaos
    Tamanini, Nicola
    Vernizzi, Filippo
    Witek, Helvi
    Wu, Kinwah
    Yagi, Kent
    Yazadjiev, Stoytcho
    Yunes, Nicolás
    Zilhão, Miguel
    Afshordi, Niayesh
    Angonin, Marie-Christine
    Baibhav, Vishal
    Barausse, Enrico
    Barreiro, Tiago
    Bartolo, Nicola
    Bellomo, Nicola
    Ben-Dayan, Ido
    Bergshoeff, Eric A.
    Bernuzzi, Sebastiano
    Bertacca, Daniele
    Bhagwat, Swetha
    Bonga, Béatrice
    Burko, Lior M.
    Compére, Geoffrey
    Cusin, Giulia
    da Silva, Antonio
    Das, Saurya
    de Rham, Claudia
    Destounis, Kyriakos
    Dimastrogiovanni, Ema
    Duque, Francisco
    Easther, Richard
    Farmer, Hontas
    Fasiello, Matteo
    Fisenko, Stanislav
    Fransen, Kwinten
    Frauendiener, Jörg
    Gair, Jonathan
    Gergely, László Árpád
    Gerosa, Davide
    Gualtieri, Leonardo
    Han, Wen-Biao
    Hees, Aurelien
    Helfer, Thomas
    Hennig, Jörg
    Jenkins, Alexander C.
    Kajfasz, Eric
    Kaloper, Nemanja
    Karas, Vladimír
    Kavanagh, Bradley J.
    Klioner, Sergei A.
    Koushiappas, Savvas M.
    Lagos, Macarena
    Le Poncin-Lafitte, Christophe
    Lobo, Francisco S. N.
    Markakis, Charalampos
    Martín-Moruno, Prado
    Martins, C. J. A. P.
    Matarrese, Sabino
    Mayerson, Daniel R.
    Mimoso, José P.
    Noller, Johannes
    Nunes, Nelson J.
    Stockholm University, Faculty of Science, Department of Physics.
    Oliveri, Roberto
    Orlando, Giorgio
    Pappas, George
    Pikovski, Igor
    Stockholm University, Faculty of Science, Department of Physics.
    Pilo, Luigi
    Podolský, Jiří
    Pratten, Geraint
    Prokopec, Tomislav
    Qi, Hong
    Rastgoo, Saeed
    Ricciardone, Angelo
    Rollo, Rocco
    Rubiera-Garcia, Diego
    Sergijenko, Olga
    Shapiro, Stuart
    Shoemaker, Deirdre
    Spallicci, Alessandro
    Stashko, Oleksandr
    Stein, Leo C.
    Tasinato, Gianmassimo
    Tolley, Andrew J.
    Vagenas, Elias C.
    Vandoren, Stefan
    Vernieri, Daniele
    Vicente, Rodrigo
    Wiseman, Toby
    Zhdanov, Valery
    Zumalacárregui, Miguel
    New horizons for fundamental physics with LISA2022In: Living Reviews in Relativity, E-ISSN 1433-8351, Vol. 25, no 1, article id 4Article, review/survey (Refereed)
    Abstract [en]

    The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of gravitational waves can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.

  • 37.
    Azzouz, Hatim
    Stockholm University, Faculty of Science, Department of Physics.
    Creation and Detection of Single Photons2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A growing number of technologies employ quantum properties in order to produce solutions that surpass the performance of conventional devices, or to execute operations that are fundamentally impossible with classical systems alone. In the field of optical quantum information science, photons are utilized to encode, communicate and manipulate information, making them vitally important. While photon production always constitutes the first step in any optical experiment, in the field of quantum information science, the recording of data through the process of photon detection is an equally crucial final step.

    This thesis deals with both the single photons generation (based on diamond color defects) and their detection, utilizing a novel type of superconducting detectors. In particular, part one of this thesis is devoted to the construction of custom designed microscope setup, and the development of laboratory experiments, to enable the generation of single photons as well as the investigation of the optical and spin properties of diamond color centers. Confocal microscopy is used for this purpose, as it allows for the identification and addressing of individual color centers that emit only single photons. This microscope also feature an integrated self-built microwave and magnetic hardware setup, which allows for a wide range of spin environment spectroscopy studies. Single photon emission is demonstrated through both photon anti-bunching and Rabi oscillations at room temperature.

    The second part of the thesis offers an exploration of superconducting single photon detectors through experiment. Since electronics are an essential part of these detectors, the possibility of using a novel alternative scheme based on capacitive readout combined with fast gating to enable simplified readout is demonstrated. This scheme overcomes the limitations of conventional readout schemes, which require large bandwidth amplification and complex counting electronics. Besides photon detection, the capabilities of these detectors are also expanded to include high-energy particles in the MeV energy range, and the detectors are demonstrated to not only detect single α- and β-particles, but to do so with near unity efficiency. Finally, a multipurpose testing station for superconducting detectors is demonstrated with a central objective of optimizing the coupling efficiency of light to the active area of the detector, as well as to allow for a fast exchange of the optical fiber, thereby facilitating an efficient characterization of the detector. The optimization of this coupling efficiency was demonstrated through proof-of-principle experiments.

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  • 38. Balducci, Federico
    et al.
    Beau, Mathieu
    Yang, Jing
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Luxembourg, Grand Duchy of Luxembourg.
    Gambassi, Andrea
    del Campo, Adolfo
    Large Deviations beyond the Kibble-Zurek Mechanism2023In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 131, no 23, article id 230401Article in journal (Refereed)
    Abstract [en]

    The Kibble-Zurek mechanism (KZM) predicts that the average number of topological defects generated upon crossing a continuous or quantum phase transition obeys a universal scaling law with the quench time. Fluctuations in the defect number near equilibrium are approximately of Gaussian form, in agreement with the central limit theorem. Using large deviations theory, we characterize the universality of fluctuations beyond the KZM and report the exact form of the rate function in the transverse-field quantum Ising model. In addition, we characterize the scaling of large deviations in an arbitrary continuous phase transition, building on recent evidence establishing the universality of the defect number distribution.

  • 39. Baldwin, Lydia
    et al.
    Jones, Emily J.
    Iles, Alexander
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carding, Simon R.
    Pamme, Nicole
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dyer, Charlotte E.
    Greenman, John
    Development of a dual-flow tissue perfusion device for modeling the gastrointestinal tract-brain axis2023In: Biomicrofluidics, E-ISSN 1932-1058, Vol. 17, no 5, article id 054104Article in journal (Refereed)
    Abstract [en]

    Despite the large number of microfluidic devices that have been described over the past decade for the study of tissues and organs, few have become widely adopted. There are many reasons for this lack of adoption, primarily that devices are constructed for a single purpose or because they are highly complex and require relatively expensive investment in facilities and training. Here, we describe a microphysiological system (MPS) that is simple to use and provides fluid channels above and below cells, or tissue biopsies, maintained on a disposable, poly(methyl methacrylate), carrier held between polycarbonate outer plates. All other fittings are standard Luer sizes for ease of adoption. The carrier can be coated with cells on both sides to generate membrane barriers, and the devices can be established in series to allow medium to flow from one cell layer to another. Furthermore, the carrier containing cells can be easily removed after treatment on the device and the cells can be visualized or recovered for additional off-chip analysis. A 0.4 mu m membrane with cell monolayers proved most effective in maintaining separate fluid flows, allowing apical and basal surfaces to be perfused independently. A panel of different cell lines (Caco-2, HT29-MTX-E12, SH-SY5Y, and HUVEC) were successfully maintained in the MPS for up to 7 days, either alone or on devices connected in series. The presence of tight junctions and mucin was expressed as expected by Caco-2 and HT-29-MTX-E12, with Concanavalin A showing uniform staining. Addition of Annexin V and PI showed viability of these cells to be >80% at 7 days. Bacterial extracellular vesicles (BEVs) produced by Bacteroides thetaiotaomicron and labeled with 1,1 '-dioctadecyl-3,3,3 ',3 '-tetramethylindocarbo-cyanine perchlorate (DiD) were used as a model component of the human colonic microbiota and were visualized translocating from an apical surface containing Caco-2 cells to differentiated SH-SY5Y neuronal cells cultured on the basal surface of connected devices. The newly described MPS can be easily adapted, by changing the carrier to maintain spheroids, pieces, or slices of biopsy tissue and joined in series to study a variety of cell and tissue processes. The cell layers can be made more complex through the addition of multiple cell types and/or different patterning of extracellular matrix and the ability to culture cells adjacent to one another to allow study of cell:cell transfer, e.g., passive or active drug transfer, virus or bacterial entry or BEV uptake and transfer.

  • 40. Banacki, Michał
    et al.
    Mironowicz, Piotr
    Stockholm University, Faculty of Science, Department of Physics. University of Gdansk, Poland; Gdansk University of Technology, Poland.
    Ramanathan, Ravishankar
    Horodecki, Paweł
    Hybrid no-signaling-quantum correlations2022In: New Journal of Physics, E-ISSN 1367-2630, Vol. 24, no 8, article id 083003Article in journal (Refereed)
    Abstract [en]

    Fundamental investigations in non-locality have shown that while the no-signaling principle alone is not sufficient to single out the set of quantum non-local correlations, local quantum mechanics and no-signaling together exactly reproduce the set of quantum correlations in the two-party Bell scenario. Here, we introduce and study an intermediate hybrid no-signaling quantum set of non-local correlations that we term HNSQ in the multi-party Bell scenario where some subsystems are locally quantum while the remaining subsystems are only constrained by the no-signaling principle. Specifically, the set HNSQ is a super-quantum set of correlations derived from no-signaling assemblages by performing quantum measurements on the trusted subsystems. We show that in contrast to the set NS of no-signaling behaviors, there exist extreme points of HNSQ in the tripartite Bell scenario that admit quantum realization. As a tool for optimization over the set HNSQ, we introduce an outer hierarchy of semi-definite programming approximations to the set following an approach put forward by Doherty–Parrilo–Spedalieri. We perform an extensive numerical analysis of the maximal violation of the facet Bell inequalities in the three-party binary input–output scenario and study the corresponding self-testing properties. In contrast to the usual no-signaling correlations, the new set allows for simple security proofs of (one-sided)-device-independent applications against super-quantum adversaries.

  • 41. Baym, Gordons
    et al.
    Pethick, Christopher J.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Copenhagen, Denmark.
    Ben Mottelson: Codeveloper of the unified theory of the structure and dynamics of atomic nuclei2022In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 119, no 40, article id e2214052119Article in journal (Other academic)
  • 42. Begam, Nafisa
    et al.
    Timmermann, Sonja
    Ragulskaya, Anastasia
    Girelli, Anita
    Senft, Maximilian D.
    Retzbach, Sebastian
    Anthuparambil, Nimmi Das
    Akhundzadeh, Mohammad Sayed
    Kowalski, Marvin
    Reiser, Mario
    Stockholm University, Faculty of Science, Department of Physics.
    Westermeier, Fabian
    Sprung, Michael
    Zhang, Fajun
    Gutt, Christian
    Schreiber, Frank
    Effects of temperature and ionic strength on the microscopic structure and dynamics of egg white gels2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 158, no 7, article id 074903Article in journal (Refereed)
    Abstract [en]

    We investigate the thermal gelation of egg white proteins at different temperatures with varying salt concentrations using x-ray photon correlation spectroscopy in the geometry of ultra-small angle x-ray scattering. Temperature-dependent structural investigation suggests a faster network formation with increasing temperature, and the gel adopts a more compact network, which is inconsistent with the conventional understanding of thermal aggregation. The resulting gel network shows a fractal dimension δ, ranging from 1.5 to 2.2. The values of δ display a non-monotonic behavior with increasing amount of salt. The corresponding dynamics in the q range of 0.002–0.1 nm−1 is observable after major change of the gel structure. The extracted relaxation time exhibits a two-step power law growth in dynamics as a function of waiting time. In the first regime, the dynamics is associated with structural growth, whereas the second regime is associated with the aging of the gel, which is directly linked with its compactness, as quantified by the fractal dimension. The gel dynamics is characterized by a compressed exponential relaxation with a ballistic-type of motion. The addition of salt gradually makes the early stage dynamics faster. Both gelation kinetics and microscopic dynamics show that the activation energy barrier in the system systematically decreases with increasing salt concentration.

  • 43.
    Bengtsson, Ingemar
    Stockholm University, Faculty of Science, Department of Physics.
    A Kochen-Specker Inequality2009In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1101, p. 241-245Article in journal (Other academic)
    Abstract [en]

    I review a paper by Klyachko, Can, Binicioğlu, and Shumovsky, and explain a little of the background as I see it

  • 44.
    Bengtsson, Ingemar
    Stockholm University, Faculty of Science, Department of Physics.
    SICs: Some explanations2020In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 50, no 12, p. 1794-1808Article in journal (Refereed)
    Abstract [en]

    The problem of constructing maximal equiangular tight frames or SICs was raised by Zauner in 1998. Four years ago it was realized that the problem is closely connected to a major open problem in number theory. We discuss why such a connection was perhaps to be expected, and give a simplified sketch of some developments that have taken place in the past 4 years. The aim, so far unfulfilled, is to prove existence of SICs in an infinite sequence of dimensions. 

  • 45.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Badziag, Piotr
    Stockholm University, Faculty of Science, Department of Physics.
    Cabello, Adan
    Pitowsky, Itamar
    Universality of State-Independent Violation of Correlation Inequalities for Non-Contextual Theories2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 5, p. 050401-Article in journal (Refereed)
    Abstract [en]

    We show that the state-independent violation of inequalities for noncontextual hidden variable theories introduced in [Phys. Rev. Lett. 101, 210401 (2008)] is universal, i.e., occurs for any quantum mechanical system in which noncontextuality is meaningful. We describe a method to obtain state-independent violations for any system of dimension d >= 3. This universality proves that, according to quantum mechanics, there are no "classical'' states.

  • 46.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holst, Sören
    Stockholm University, Faculty of Science, Department of Physics.
    Jakobsson, Emma
    Stockholm University, Faculty of Science, Department of Physics.
    Classics illustrated: limits of spacetimes2014In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 31, no 20, article id 205008Article in journal (Refereed)
    Abstract [en]

    We carefully study the em and e→0 limits of the Reissner-Nordström spacetime using Geroch's definition of limits of spacetimes. This is implemented by embedding the one-parameter family of spacetimes in anti-de Sitter space, and as a result we obtain metrically correct Penrose diagrams. For em two distinct limits are studied.

  • 47.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Jakobsson, Emma
    Stockholm University, Faculty of Science, Department of Physics.
    A Toy Penrose Inequality and Its Proof2016In: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532, Vol. 48, no 12, article id 156Article in journal (Refereed)
    Abstract [en]

    We formulate and prove a toy version of the Penrose inequality. The formulation mimics the original Penrose inequality in which the scenario is the following: A shell of null dust collapses in Minkowski space and a marginally trapped surface forms on it. Through a series of arguments relying on established assumptions, an inequality relating the area of this surface to the total energy of the shell is formulated. Then a further reformulation turns the inequality into a statement relating the area and the outer null expansion of a class of surfaces in Minkowski space itself. The inequality has been proven to hold true in many special cases, but there is no proof in general. In the toy version here presented, an analogous inequality in (2+1)-dimensional anti-de Sitter space turns out to hold true.

  • 48.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Jakobsson, Emma
    Stockholm University, Faculty of Science, Department of Physics.
    Black holes: Their large interiors2015In: Modern Physics Letters A, ISSN 0217-7323, E-ISSN 1793-6632, Vol. 30, no 21, article id 1550103Article in journal (Refereed)
    Abstract [en]

    Christodoulou and Rovelli (CR) have remarked on the large interiors possessed by static black holes. We amplify their remarks, and extend them to the spinning case.

  • 49.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Jakobsson, Emma
    Stockholm University, Faculty of Science, Department of Physics.
    Senovilla, José M. M.
    Trapped surfaces in Oppenheimer-Snyder black holes2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, no 6, article id 064012Article in journal (Refereed)
    Abstract [en]

    The Oppenheimer-Snyder solution models a homogeneous round dust of cloud collapsing to a black hole. Inside its event horizon there is a region through which trapped surfaces pass. We try to determine exactly where the boundary of this region meets the center of the cloud. We present explicit examples of the relevant trapped (topological) spheres; they extend into the exterior vacuum region, and are carefully matched at the junction between the cloud and the vacuum.

  • 50.
    Bengtsson, Ingemar
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Jose M M Senovilla,
    A Note on Trapped Surfaces in the Vaidya Solution2009In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 79, no 2, p. 024027-Article in journal (Refereed)
    Abstract [en]

    The Vaidya solution describes the gravitational collapse of a finite shell of incoherent radiation falling into flat spacetime and giving rise to a Schwarzschild black hole. There has been a question whether closed trapped surfaces can extend into the flat region (whereas closed outer trapped surfaces certainly can). For the special case of self-similar collapse we show that the answer is yes, if and only if the mass function rises fast enough.

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