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  • 1. Ade, Peter
    et al.
    Aguirre, James
    Ahmed, Zeeshan
    Aiola, Simone
    Ali, Aamir
    Alonso, David
    Alvarez, Marcelo A.
    Arnold, Kam
    Ashton, Peter
    Austermann, Jason
    Awan, Humna
    Baccigalupi, Carlo
    Baildon, Taylor
    Barron, Darcy
    Battaglia, Nick
    Battye, Richard
    Baxter, Eric
    Bazarko, Andrew
    Beall, James A.
    Bean, Rachel
    Beck, Dominic
    Beckman, Shawn
    Beringue, Benjamin
    Bianchini, Federico
    Boada, Steven
    Boettger, David
    Bond, J. Richard
    Borrill, Julian
    Brown, Michael L.
    Bruno, Sarah Marie
    Bryan, Sean
    Calabrese, Erminia
    Calafut, Victoria
    Calisse, Paolo
    Carron, Julien
    Challinor, Anthony
    Chesmore, Grace
    Chinone, Yuji
    Chluba, Jens
    Cho, Hsiao-Mei Sherry
    Choi, Steve
    Coppi, Gabriele
    Cothard, Nicholas F.
    Coughlin, Kevin
    Crichton, Devin
    Crowley, Kevin D.
    Crowley, Kevin T.
    Cukierman, Ari
    D'Ewart, John M.
    Dunner, Rolando
    de Haan, Tijmen
    Devlin, Mark
    Dicker, Simon
    Didier, Joy
    Dobbs, Matt
    Dober, Bradley
    Duell, Cody J.
    Duff, Shannon
    Duivenvoorden, Adri
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dunkley, Jo
    Dusatko, John
    Errard, Josquin
    Fabbian, Giulio
    Feeney, Stephen
    Ferraro, Simone
    Fluxa, Pedro
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Michigan, U.S.A..
    Frisch, Josef C.
    Frolov, Andrei
    Fuller, George
    Fuzia, Brittany
    Galitzki, Nicholas
    Gallardo, Patricio A.
    Ghersi, Jose Tomas Galvez
    Gao, Jiansong
    Gawiser, Eric
    Gerbino, Martina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gluscevic, Vera
    Goeckner-Wald, Neil
    Golec, Joseph
    Gordon, Sam
    Gralla, Megan
    Green, Daniel
    Grigorian, Arpi
    Groh, John
    Groppi, Chris
    Guan, Yilun
    Gudmundsson, Jon E.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Han, Dongwon
    Hargrave, Peter
    Hasegawa, Masaya
    Hasselfield, Matthew
    Hattori, Makoto
    Haynes, Victor
    Hazumi, Masashi
    He, Yizhou
    Healy, Erin
    Henderson, Shawn W.
    Hervias-Caimapo, Carlos
    Hill, Charles A.
    Hill, J. Colin
    Hilton, Gene
    Hilton, Matt
    Hincks, Adam D.
    Hinshaw, Gary
    Hlozek, Renee
    Ho, Shirley
    Ho, Shuay-Pwu Patty
    Howe, Logan
    Huang, Zhiqi
    Hubmayr, Johannes
    Huffenberger, Kevin
    Hughes, John P.
    Ijjas, Anna
    Ikape, Margaret
    Irwin, Kent
    Jaffe, Andrew H.
    Jain, Bhuvnesh
    Jeong, Oliver
    Kaneko, Daisuke
    Karpel, Ethan D.
    Katayama, Nobuhiko
    Keating, Brian
    Kernasovskiy, Sarah S.
    Keskitalo, Reijo
    Kisner, Theodore
    Kiuchi, Kenji
    Klein, Jeff
    Knowles, Kenda
    Koopman, Brian
    Kosowsky, Arthur
    Krachmalnicoff, Nicoletta
    Kuenstner, Stephen E.
    Kuo, Chao-Lin
    Kusaka, Akito
    Lashner, Jacob
    Lee, Adrian
    Lee, Eunseong
    Leon, David
    Leung, Jason S-Y
    Lewis, Antony
    Li, Yaqiong
    Li, Zack
    Limon, Michele
    Linder, Eric
    Lopez-Caraballo, Carlos
    Louis, Thibaut
    Lowry, Lindsay
    Lungu, Marius
    Madhavacheril, Mathew
    Mak, Daisy
    Maldonado, Felipe
    Mani, Hamdi
    Mates, Ben
    Matsuda, Frederick
    Maurin, Loic
    Mauskopf, Phil
    May, Andrew
    McCallum, Nialh
    McKenney, Chris
    McMahon, Jeff
    Meerburg, P. Daniel
    Meyers, Joel
    Miller, Amber
    Mirmelstein, Mark
    Moodley, Kavilan
    Munchmeyer, Moritz
    Munson, Charles
    Naess, Sigurd
    Nati, Federico
    Navaroli, Martin
    Newburgh, Laura
    Ho, Nam
    Niemack, Michael
    Nishino, Haruki
    Orlowski-Scherer, John
    Page, Lyman
    Partridge, Bruce
    Peloton, Julien
    Perrotta, Francesca
    Piccirillo, Lucio
    Pisano, Giampaolo
    Poletti, Davide
    Puddu, Roberto
    Puglisi, Giuseppe
    Raum, Chris
    Reichardt, Christian L.
    Remazeilles, Mathieu
    Rephaeli, Yoel
    Riechers, Dominik
    Rojas, Felipe
    Roy, Anirban
    Sadeh, Sharon
    Sakurail, Yuki
    Salatino, Maria
    Rao, Mayuri Sathyanarayana
    Schaan, Emmanuel
    Schmittfull, Marcel
    Sehgal, Neelima
    Seibert, Joseph
    Seljak, Uros
    Sherwin, Blake
    Shimon, Meir
    Sierra, Carlos
    Sievers, Jonathan
    Sikhosana, Precious
    Silva-Feaver, Maximiliano
    Simon, Sara M.
    Sinclair, Adrian
    Siritanasak, Praween
    Smith, Kendrick
    Smith, Stephen R.
    Spergel, David
    Staggs, Suzanne T.
    Stein, George
    Stevens, Jason R.
    Stompor, Radek
    Suzuki, Aritoki
    Tajima, Osamu
    Takakura, Satoru
    Teply, Grant
    Thomas, Daniel B.
    Thorne, Ben
    Thornton, Robert
    Trac, Hy
    Tsai, Calvin
    Tucker, Carole
    Ullom, Joel
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    van Engelen, Alexander
    Van Lanen, Jeff
    Van Winkle, Daniel D.
    Vavagiakis, Eve M.
    Verges, Clara
    Vissers, Michael
    Wagoner, Kasey
    Walker, Samantha
    Ward, Jon
    Westbrook, Ben
    Whitehorn, Nathan
    Williams, Jason
    Williams, Joel
    Wollack, Edward J.
    Xu, Zhilei
    Yu, Byeonghee
    Yu, Cyndia
    Zago, Fernando
    Zhang, Hezi
    Zhu, Ningfeng
    The Simons Observatory: science goals and forecasts2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 2, article id 056Article in journal (Refereed)
    Abstract [en]

    The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.

  • 2. Bambi, Cosimo
    et al.
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Cambridge, United Kingdom.
    Visinelli, Luca
    Testing the rotational nature of the supermassive object M87*from the circularity and size of its first image2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 4, article id 044057Article in journal (Refereed)
    Abstract [en]

    The Event Horizon Telescope (EHT) collaboration has recently released the first image of a black hole (BH), opening a new window onto tests of general relativity in the strong field regime. In this paper, we derive constraints on the nature of M87* (the supermassive object at the center of the galaxy M87), exploiting the fact that its shadow appears to be highly circular, and using measurements of its angular size. We first consider the simple case where M87* is assumed to be a Kerr BH. We find that the inferred circularity of M87* excludes Kerr BHs with observation angle theta(obs) greater than or similar to 45 degrees for dimensionless rotational parameter 0.95 less than or similar to a(*) <= 1 whereas the observation angle is unbounded for a(*) less than or similar to 0.9. We then consider the possibility that M87* might be a superspinar, i.e., an object described by the Kerr solution and spinning so fast that it violates the Kerr bound by having vertical bar a(*)vertical bar > 1. We find that, within certain regions of parameter space, the inferred circularity and size of the shadow of M87* do not exclude the possibility that this object might be a superspinar.

  • 3. Casalino, Alessandro
    et al.
    Rinaldi, Massimiliano
    Sebastiani, Lorenzo
    Vagnozzi, Sunny
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Alive and well: mimetic gravity and a higher-order extension in light of GW1708172019In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 36, no 1, article id 017001Article in journal (Refereed)
    Abstract [en]

    The near-simultaneous multi-messenger detection of the gravitational wave (GW) event GW170817 and its optical counterpart, the short gamma-ray burst GRB170817A, implies that deviations of the GW speed from the speed of light are restricted to being of Omicron(10(-15)). In this note, we study the implications of this bound for mimetic gravity and confirm that in the original setting of the theory, GWs propagate at the speed of light, hence ensuring agreement with the recent multi-messenger detection. A higher-order extension of the original mimetic theory, appearing in the low-energy limit of projectable Horava-Lifshitz gravity, is then considered. Performing a Bayesian statistical analysis where we compare the predictions of the higher-order mimetic model for the speed of GWs against the observational bound from GW170817/GRB170817A, we derive constraints on the three free parameters of the theory. Imposing the absence of both ghost instabilities and superluminal propagation of scalar and tensor perturbations, we find very stringent 95% confidence level upper limits of similar to 7 x 10(-15) and similar to 4 x 10(-15)on the coupling strengths of Lagrangian terms of the form del(mu)del(nu)phi del(mu)del(nu)phi and (square phi)(2) respectively, with phi the mimetic field. We discuss implications of the obtained bounds for mimetic theories. This work presents the first ever robust comparison of a mimetic theory to observational data.

  • 4. Casalino, Alessandro
    et al.
    Rinaldi, Massimiliano
    Sebastiani, Lorenzo
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mimicking dark matter and dark energy in a mimetic model compatible with GW1708172018In: Physics of the Dark Universe, ISSN 0953-8585, E-ISSN 2212-6864, Vol. 22, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The recent observation of the gravitational wave event GW170817 and of its electromagnetic counterpart GRB170817A, from a binary neutron star merger, has established that the speed of gravitational waves deviates from the speed of light by less than one part in 10(15). As a consequence, many extensions of General Relativity are inevitably ruled out. Among these we find the most relevant sectors of Horndeski gravity. In its original formulation, mimetic gravity is able to mimic cosmological dark matter, has tensorial perturbations that travel exactly at the speed of light but has vanishing scalar perturbations and this fact persists if we combine mimetic with Horndeski gravity. In this work, we show that implementing the mimetic gravity action with higher-order terms that break the Horndeski structure yields a cosmological model that satisfies the constraint on the speed of gravitational waves and mimics both dark energy and dark matter with a non-vanishing speed of sound. In this way, we are able to reproduce the Lambda CDM cosmological model without introducing particle cold dark matter.

  • 5. Cognola, Guido
    et al.
    Myrzakulov, Ratbay
    Sebastiani, Lorenzo
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Zerbini, Sergio
    Covariant Horava-like and mimetic Horndeski gravity: cosmological solutions and perturbations2016In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 33, no 22, article id 225014Article in journal (Refereed)
    Abstract [en]

    We consider a variant of the Nojiri-Odintsov covariant Horava-like gravitational model, where diffeomorphism invariance is broken dynamically via a non-standard coupling to a perfect fluid. The theory allows one to address some of the potential instability problems present in Horava-Lifshitz gravity due to explicit diffeomorphism invariance breaking. The fluid is instead constructed from a scalar field constrained by a Lagrange multiplier. In fact, the Lagrange multiplier construction allows for an extension of the Horavalike model to include the scalar field of mimetic gravity, an extension which we thoroughly explore. By adding a potential for the scalar field, we show how one can reproduce a number of interesting cosmological scenarios. We then turn to the study of perturbations around a flat FLRW background, showing that the fluid in question behaves as an irrotational fluid, with zero sound speed. To address this problem, we consider a modified version of the theory, adding higher derivative terms in a way which brings us beyond the Horndeski framework. We compute the sound speed in this modified higher order mimetic Horava-like model and show that it is non-zero, which means that perturbations therein can be sensibly defined. Caveats to our analysis, as well as comparisons to projectable Horava-Lifshitz gravity, are also discussed. In conclusion, we present a theory of gravity which preserves diffeomorphism invariance at the level of the action but breaks it dynamically in the UV, reduces to General Relativity (GR) in the IR, allows the realization of a number of interesting cosmological scenarios, is well defined when considering perturbations around a flat FLRW background, and features cosmological dark matter emerging as an integration constant.

  • 6. Dutta, Jibitesh
    et al.
    Khyllep, Wompherdeiki
    Saridakis, Emmanuel N.
    Tamanini, Nicola
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Cosmological dynamics of mimetic gravity2018In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 2, article id 041Article in journal (Refereed)
    Abstract [en]

    We present a detailed investigation of the dynamical behavior of mimetic gravity with a general potential for the mimetic scalar field. Performing a phase-space and stability analysis, we show that the scenario at hand can successfully describe the thermal history of the universe, namely the successive sequence of radiation, matter, and dark-energy eras. Additionally, at late times the universe can either approach a de Sitter solution, or a scaling accelerated attractor where the dark-matter and dark-energy density parameters are of the same order, thus offering an alleviation of the cosmic coincidence problem. Applying our general analysis to various specific potential choices, including the power-law and the exponential ones, we show that mimetic gravity can be brought into good agreement with the observed behavior of the universe. Moreover, with an inverse square potential we find that mimetic gravity offers an appealing unified cosmological scenario where both dark energy and dark matter are characterized by a single scalar field, and where the cosmic coincidence problem is alleviated.

  • 7. Foot, Robert
    et al.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Solving the small-scale structure puzzles with dissipative dark matter2016In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 013Article in journal (Refereed)
    Abstract [en]

    Small-scale structure is studied in the context of dissipative dark matter, arising for instance in models with a hidden unbroken Abelian sector, so that dark matter couples to a massless dark photon. The dark sector interacts with ordinary matter via gravity and photon-dark photon kinetic mixing. Mirror dark matter is a theoretically constrained special case where all parameters are fixed except for the kinetic mixing strength, epsilon. In these models, the dark matter halo around spiral and irregular galaxies takes the form of a dissipative plasma which evolves in response to various heating and cooling processes. It has been argued previously that such dynamics can account for the inferred cored density profiles of galaxies and other related structural features. Here we focus on the apparent deficit of nearby small galaxies (missing satellite problem), which these dissipative models have the potential to address through srnall-scale power suppression by acoustic and diffusion damping. Using a variant of the extended Press-Schechter formalism, we evaluate the halo mass function for the special case of mirror dark matter. Considering a simplified model where M-baryons proportional to M-halo, we relate the halo mass function to more directly observable quantities, and find that for epsilon approximate to 2 x 10(-10) such a simplified description is compatible with the measured galaxy luminosity and velocity functions. On scales Mhalo less than or similar to 10(8) M-circle dot, diffusion damping exponentially suppresses the halo mass function, suggesting a nonprimordial origin for dwarf spheroidal satellite galaxies, which we speculate were formed via a top-down fragmentation process as the result of nonlinear dissipative collapse of larger density perturbations. This could explain the planar orientation of satellite galaxies around Andromeda and the Milky Way.

  • 8.
    Gerbino, Martina
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Lattanzi, Massimiliano
    Mena, Olga
    Giusarma, Elena
    Ho, Shirley
    Impact of neutrino properties on the estimation of inflationary parameters from current and future observations2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 4, article id 043512Article in journal (Refereed)
    Abstract [en]

    We study the impact of assumptions about neutrino properties on the estimation of inflationary parameters from cosmological data, with a specific focus on the allowed contours in the n(s)/r plane, where n(s) is the scalar spectral index and r is the tensor-to-scalar ratio. We study the following neutrino properties: (i) the total neutrino mass M-i = Sigma(i)m(i) (where the index i = 1, 2, 3 runs over the three neutrino mass eigenstates); (ii) the number of relativistic degrees of freedom N-eff at the time of recombination; and (iii) the neutrino hierarchy. Whereas previous literature assumed three degenerate neutrino masses or two massless neutrino species (approximations that clearly do not match neutrino oscillation data), we study the cases of normal and inverted hierarchy. Our basic result is that these three neutrino properties induce < 1 sigma shift of the probability contours in the n(s)/r plane with both current or upcoming data. We find that the choice of neutrino hierarchy (normal, inverted, or degenerate) has a negligible impact. However, the minimal cutoff on the total neutrino mass M-v,M-min = 0 that accompanies previous works using the degenerate hierarchy does introduce biases in the n(s)/r plane and should be replaced by M-v,M-min = 0.059 eV as required by oscillation data. Using current cosmic microwave background (CMB) data from Planck and Bicep/Keck, marginalizing over the total neutrino mass M-v and over r can lead to a shift in the mean value of ns of similar to 0.3 sigma toward lower values. However, once baryon acoustic oscillation measurements are included, the standard contours in the n(s)/r plane are basically reproduced. Larger shifts of the contours in the n(s)/r plane (up to 0.8 sigma) arise for nonstandard values of N-eff. We also provide forecasts for the future CMB experiments Cosmic Origins Explorer (COrE, satellite) and Stage-IV (ground-based) and show that the incomplete knowledge of neutrino properties, taken into account by a marginalization over M-v, could induce a shift of similar to 0.4 sigma toward lower values in the determination of ns (or a similar to 0.8 sigma shift if one marginalizes over N-eff). Comparison to specific inflationary models is shown. Imperfect knowledge of neutrino properties must be taken into account properly, given the desired precision in determining whether or not inflationary models match the future data.

  • 9. Giusarma, Elena
    et al.
    Gerbino, Martina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mena, Olga
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Ho, Shirley
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Improvement of cosmological neutrino mass bounds2016In: Physical Review D, ISSN 2470-0010, Vol. 94, no 8, article id 083522Article in journal (Refereed)
    Abstract [en]

    The most recent measurements of the temperature and low-multipole polarization anisotropies of the cosmic microwave background from the Planck satellite, when combined with galaxy clustering data from the Baryon Oscillation Spectroscopic Survey in the form of the full shape of the power spectrum, and with baryon acoustic oscillation measurements, provide a 95% confidence level (C.L.) upper bound on the sum of the three active neutrinos Sigma m(nu) < 0.183 eV, among the tightest neutrino mass bounds in the literature, to date, when the same data sets are taken into account. This very same data combination is able to set, at similar to 70% C.L., an upper limit on Sigma m(nu) of 0.0968 eV, a value that approximately corresponds to the minimal mass expected in the inverted neutrino mass hierarchy scenario. If high-multipole polarization data from Planck is also considered, the 95% C.L. upper bound is tightened to Sigma m(nu) < 0.176 eV. Further improvements are obtained by considering recent measurements of the Hubble parameter. These limits are obtained assuming a specific nondegenerate neutrino mass spectrum; they slightly worsen when considering other degenerate neutrino mass schemes. Low-redshift quantities, such as the Hubble constant or the reionization optical depth, play a very important role when setting the neutrino mass constraints. We also comment on the eventual shifts in the cosmological bounds on Sigma m(nu) when possible variations in the former two quantities are addressed.

  • 10. Giusarma, Elena
    et al.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Ho, Shirley
    Ferraro, Simone
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Kamen-Rubio, Rocky
    Luk, Kam-Biu
    Scale-dependent galaxy bias, CMB lensing-galaxy cross-correlation, and neutrino masses2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 12, article id 123526Article in journal (Refereed)
    Abstract [en]

    One of the most powerful cosmological data sets when it comes to constraining neutrino masses is represented by galaxy power spectrum measurements, P-gg(k). The constraining power of P-gg(k) is however severely limited by uncertainties in the modeling of the scale-dependent galaxy bias b(k). In this work we present a new proof-of-principle for a method to constrain b(k) by using the cross-correlation between the cosmic microwave background (CMB) lensing signal and galaxy maps (C-l(kappa g)) using a simple but theoretically well-motivated parametrization for b(k). We apply the method using C-l(kappa g) measured by cross-correlating Planck lensing maps and the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 (DR11) CMASS galaxy sample, and P-gg(k) measured from the BOSS DR12 CMASS sample. We detect a nonzero scale-dependence at moderate significance, which suggests that a proper modeling of b(k) is necessary in order to reduce the impact of nonlinearities and minimize the corresponding systematics. The accomplished increase in constraining power of P-gg(k) is demonstrated by determining a 95% confidence level upper bound on the sum of the three active neutrino masses M-nu of M-nu < 0.19 eV. This limit represents a significant improvement over previous bounds with comparable data sets. Our method will prove especially powerful and important as future large-scale structure surveys will overlap more significantly with the CMB lensing kernel providing a large cross-correlation signal.

  • 11.
    Kinney, William H.
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University at Buffalo, United States of America.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Visinelli, Luca
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Uppsala, Sweden.
    The zoo plot meets the swampland: mutual (in)consistency of single-field inflation, string conjectures, and cosmological data2019In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 36, no 11, article id 117001Article in journal (Refereed)
    Abstract [en]

    We consider single-field inflation in light of string-motivated 'swampland' conjectures suggesting that effective scalar field theories with a consistent UV completion must have field excursion Delta(phi) less than or similar to M-Pl, in combination with a sufficiently steep potential, MPlV phi/V greater than or similar to O(1). Here, we show that the swampland conjectures are inconsistent with existing observational constraints on single-field inflation. Focusing on the observationally favoured class of concave potentials, we map the allowed swampland region onto the n(S)-r 'zoo plot' of inflationary models, and find that consistency with the Planck satellite and BICEP2/Keck Array requires MPlV phi/V less than or similar to 0.1 and -0.02 less than or similar to M-Pl(2)/V-phi phi < 0, in strong tension with swampland conjectures. Extension to non-canonical models such as DBI Inflation does not significantly weaken the bound.

  • 12. Myrzakulov, R.
    et al.
    Sebastiani, L.
    Vagnozzi, Sunny
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Copenhagen, Denmark; University of Melbourne, Australia.
    Inflation in f (R, phi)-theories and mimetic gravity scenario2015In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, no 9, article id 444Article in journal (Refereed)
    Abstract [en]

    We investigate inflation within f (R, phi)-theories, where a dynamical scalar field is coupled to gravity. A class of models which can support early-time acceleration with the emerging of an effective cosmological constant at high curvature is studied. The dynamics of the field allow for exit from inflation leading to the correct amount of inflation in agreement with cosmological data. Furthermore, the spectral index and tensor-to-scalar ratio of the models are carefully analyzed. A generalization of the theory to incorporate dark matter in the context of mimetic gravity, and further extensions of the latter, are also discussed.

  • 13. Myrzakulov, Ratbay
    et al.
    Sebastiani, Lorenzo
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Zerbini, Sergio
    Static spherically symmetric solutions in mimetic gravity: rotation curves and wormholes2016In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 33, no 12, article id 125005Article in journal (Refereed)
    Abstract [en]

    In this work, we analyse static spherically symmetric solutions in the framework of mimetic gravity, an extension of general relativity where the con-formal degree of freedom of gravity is isolated in a covariant fashion. Here we extend previous works by considering, in addition, a potential for the mimetic field. An appropriate choice of such a potential allows for the reconstruction of a number of interesting cosmological and astrophysical scenarios. We explicitly show how to reconstruct such a potential for a general static spherically symmetric space-time. A number of applications and scenarios are then explored, among which are traversable wormholes. Finally, we analytically reconstruct potentials, which leads to solutions to the equations of motion featuring polynomial corrections to the Schwarzschild space-time. Accurate choices for such corrections could provide an explanation for the inferred flat rotation curves of spiral galaxies within the mimetic gravity framework, without the need for particle dark matter.

  • 14.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    New Solar Metallicity Measurements2019In: Atoms, ISSN 2218-2004, Vol. 7, no 2, article id 41Article in journal (Refereed)
    Abstract [en]

    In the past years, a systematic downward revision of the metallicity of the Sun has led to the solar modeling problem, namely the disagreement between predictions of standard solar models and inferences from helioseismology. Recent solar wind measurements of the metallicity of the Sun, however, provide once more an indication of a high-metallicity Sun. Because of the effects of possible residual fractionation, the derived value of the metallicity <mml:semantics>Z circle dot=0.0196 +/- 0.0014</mml:semantics> actually represents a lower limit to the true metallicity of the Sun. However, when compared with helioseismological measurements, solar models computed using these new abundances fail to restore agreement, owing to the implausibly high abundance of refractory (Mg, Si, S, Fe) elements, which correlates with a higher core temperature and hence an overproduction of solar neutrinos. Moreover, the robustness of these measurements is challenged by possible first ionization potential fractionation processes. I will discuss these solar wind measurements, which leave the solar modeling problem unsolved.

  • 15.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Recovering a MOND-like acceleration law in mimetic gravity2017In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 34, no 18, article id 185006Article in journal (Refereed)
    Abstract [en]

    We reconsider the recently proposed mimetic gravity, focusing in particular on whether the theory is able to reproduce the inferred flat rotation curves of galaxies. We extend the theory by adding a non-minimal coupling between matter and mimetic field. Such coupling leads to the appearance of an extra force which renders the motion of test particles non-geodesic. By studying the weak field limit of the resulting equations of motion, we demonstrate that in the Newtonian limit the acceleration law induced by the non-minimal coupling reduces to a modified Newtonian dynamics (MOND)-like one. In this way, it is possible to reproduce the successes of MOND, namely the explanation for the flat galactic rotation curves and the Tully-Fisher relation, within the framework of mimetic gravity, without the need for particle dark matter. The scale-dependence of the recovered acceleration scale opens up the possibility of addressing the missing mass problem not only on galactic but also on cluster scales: we defer a full study of this issue, together with a complete analysis of fits to spiral galaxy rotation curves, to an upcoming companion paper.

  • 16.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics.
    Weigh them all!: Cosmological searches for the neutrino mass scale and mass ordering2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The elusive neutrinos are among the most intriguing constituents of the particle zoo. The observation of neutrino flavour oscillations, indicating that neutrinos are massive, provides the only direct evidence for physics beyond the Standard Model. Neutrinos imprint peculiar signatures in the Cosmic Microwave Background (CMB) and in the distribution of Large-Scale Structure (LSS) in the Universe, making cosmology a very promising arena for probing neutrino properties. A detection of neutrino masses is avowedly among the key goals of several upcoming CMB and LSS surveys. For such a promise to be robustly realized, a number of issues need to be addressed, particularly on the LSS side. In this thesis, I describe a number of recent important developments in neutrino cosmology on three fronts.

    Firstly, focusing on LSS data, I will show that current cosmological probes (and particularly galaxy power spectrum data) contain a wealth of information on the sum of the neutrino masses. I will report on the analysis leading to the currently best upper limit on the sum of the neutrino masses of 0.12 eV. I show how cosmological data exhibits a weak preference for the normal neutrino mass ordering because of parameter space volume effects, and propose a simple method to quantify this preference.

    Secondly, I will discuss how galaxy bias represents a severe limitation towards fully capitalizing on the neutrino information hidden in LSS data. I propose a method for calibrating the scale-dependent galaxy bias using CMB lensing-galaxy cross-correlations. Another crucial issue in this direction is represented by how the bias is defined in first place. In the presence of massive neutrinos, the usual definition of bias becomes inadequate, as it leads to a scale-dependence on large scales which has never been accounted for. I show that failure to define the bias appropriately will be a problem for future LSS surveys, leading to incorrectly estimated cosmological parameters. In doing so, I propose a simple recipe to account for the effect of massive neutrinos on galaxy bias.

    Finally, I take on a different angle and discuss implications of correlations between neutrino parameters and other cosmological parameters. I show how, in non-phantom dynamical dark energy models (which include quintessence), the upper limit on the sum of the neutrino masses becomes tighter than the ΛCDM limit. Therefore, such models exhibit an even stronger preference for the normal ordering, and their viability could be jeopardized should near-future laboratory experiments determine that the mass ordering is inverted. I then discuss correlations between neutrino and inflationary parameters. I find that our determination of inflationary parameters is relatively stable against reasonable assumptions about the neutrino sector, and thus that neutrino unknowns do not represent an important nuisance for our understanding of inflation and the initial conditions of the Universe.

    The findings reported in this thesis answer a number of important open questions whose addressing is necessary to ensure a robust detection of neutrino masses (and possibly of the neutrino mass ordering) from future cosmological data, opening the door towards physics beyond the Standard Model.

  • 17.
    Vagnozzi, Sunny
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Brinckmann, Thejs
    Archidiacono, Maria
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Gerbino, Martina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lesgourgues, Julien
    Sprenger, Tim
    Bias due to neutrinos must not uncorrect'd go2018In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 9, article id 001Article in journal (Refereed)
    Abstract [en]

    It is a well known fact that galaxies are biased tracers of the distribution of matter in the Universe. The galaxy bias is usually factored as a function of redshift and scale, and approximated as being scale-independent on large, linear scales. In cosmologies with massive neutrinos, the galaxy bias defined with respect to the total matter field (cold dark matter, baryons, and non-relativistic neutrinos) also depends on the sum of the neutrino masses M-nu, and becomes scale-dependent even on large scales. This effect has been usually neglected given the sensitivity of current surveys. However, it becomes a severe systematic for future surveys aiming to provide the first detection of non-zero M-nu. The effect can be corrected for by defining the bias with respect to the density field of cold dark matter and baryons, rather than the total matter field. In this work, we provide a simple prescription for correctly mitigating the neutrino-induced scale-dependent bias effect in a practical way. We clarify a number of subtleties regarding how to properly implement this correction in the presence of redshift-space distortions and non-linear evolution of perturbations. We perform a Markov Chain Monte Carlo analysis on simulated galaxy clustering data that match the expected sensitivity of the Euclid survey. We find that the neutrino-induced scale-dependent bias can lead to important shifts in both the inferred mean value of M-nu, as well as its uncertainty, and provide an analytical explanation for the magnitude of the shifts. We show how these shifts propagate to the inferred values of other cosmological parameters correlated with M-nu, such as the cold dark matter physical density Omega(cdm)h(2) and the scalar spectral index n(s). In conclusion, we find that correctly accounting for the neutrino-induced scale-dependent bias will be of crucial importance for future galaxy clustering analyses. We encourage the cosmology community to correctly account for this effect using the simple prescription we present in our work. The tools necessary to easily correct for the neutrino-induced scale-dependent bias will be made publicly available in an upcoming release of the Boltzmann solver CLASS.

  • 18.
    Vagnozzi, Sunny
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Dhawan, Suhail
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gerbino, Martina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mena, Olga
    Constraints on the sum of the neutrino masses in dynamical dark energy models with w(z) >=-1 are tighter than those obtained in Lambda CDM2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 8, article id 083501Article in journal (Refereed)
    Abstract [en]

    We explore cosmological constraints on the sum of the three active neutrino masses M-v in the context of dynamical dark energy (DDE) models with equation of state (EoS) parametrized as a function of redshift z by w(z) = w(0) + w(a)z/ (1 + z), and satisfying w(z) >= -1 for all z. We make use of cosmic microwave background data from the Planck satellite, baryon acoustic oscillation measurements, and supernovae la luminosity distance measurements, and perform a Bayesian analysis. We show that, within these models, the bounds on M-v do not degrade with respect to those obtained in the Lambda CDM case; in fact, the bounds arc slightly tighter, despite the enlarged parameter space. We explain our results based on the observation that, for fixed choices of w(0), w(a) such that w(z) >= -1 (but not w = -1 for all z), the upper limit on M-v is tighter than the Lambda CDM limit because of the well-known degeneracy between w and M-v. The Bayesian analysis we have carried out then integrates over the possible values of w(0)-w(a) such that w(z) >= -1, all of which correspond to tighter limits on M-v than the Lambda CDM limit. We find a 95% credible interval (C.I.) upper bound of M-v < 0.13 eV. This bound can be compared with the 95% C.I. upper bounds of M-v < 0.16 eV, obtained within the Lambda CDM model, and M-v < 0.41 eV, obtained in a DDE model with arbitrary EoS (which allows values of w < -1). Contrary to the results derived for DDE models with arbitrary EoS, we find that a dark energy component with w(z) >= -1 is unable to alleviate the tension between high-redshift observables and direct measurements of the Hubble constant H o . Finally, in light of the results of this analysis, we also discuss the implications for DDE models of a possible determination of the neutrino mass ordering by laboratory searches.

  • 19.
    Vagnozzi, Sunny
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Michigan, USA.
    Zurbuchen, Thomas H.
    Solar Models in Light of New High Metallicity Measurements from Solar Wind Data2017In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 839, no 1, article id 55Article in journal (Refereed)
    Abstract [en]

    We study the impact of new metallicity measurements, from solar wind data, on the solar model. The solar modeling problem refers to the persisting discrepancy between helioseismological observations and predictions of solar models computed implementing state-of-the-art photospheric abundances. We critically reassess the problem, in particular considering the new set of abundances of von Steiger & Zurbuchen, determined through the in situ collection of solar wind samples from polar coronal holes. This new set of abundances indicates a solar metallicity Z(circle dot) >= 0.0196 +/- 0.0014, significantly higher than the currently established value. The new values hint at an abundance of volatile elements (i.e., C, N, O, Ne) close to previous results of Grevesse and Sauval, whereas the abundance of refractory elements (i.e., Mg, Si, S, Fe) is considerably increased. Using the Linear Solar Model formalism, we determine the variation of helioseismological observables in response to the changes in elemental abundances, in order to explore the consistency of these new measurements with constraints from helioseismology. We find that for observables that are particularly sensitive to the abundance of volatile elements, in particular the radius of the convective zone boundary (CZB) and the sound speed around the radius of CZB, improved agreement over previous models is obtained. Conversely, the high abundance of refractories correlates with a higher core temperature, resulting in an overproduction of neutrinos and a huge increase in the surface helium abundance. We conclude that the solar modeling problem remains unsolved.

  • 20.
    Vagnozzi, Sunny
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Giusarma, Elena
    Mena, Olga
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Michigan, USA.
    Gerbino, Martina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ho, Shirley
    Lattanzi, Massimiliano
    Unveiling nu secrets with cosmological data: Neutrino masses and mass hierarchy2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 96, no 12, article id 123503Article in journal (Refereed)
    Abstract [en]

    Using some of the latest cosmological data sets publicly available, we derive the strongest bounds in the literature on the sum of the three active neutrino masses, M-nu, within the assumption of a background flat Lambda CDM cosmology. In the most conservative scheme, combining Planck cosmic microwave background temperature anisotropies and baryon acoustic oscillations (BAO) data, as well as the up-to-date constraint on the optical depth to reionization (tau), the tightest 95% confidence level upper bound we find is M-nu < 0.151 eV. The addition of Planck high-l polarization data, which, however, might still be contaminated by systematics, further tightens the bound to M-nu < 0.118 eV. A proper model comparison treatment shows that the two aforementioned combinations disfavor the inverted hierarchy at similar to 64% C.L. and similar to 71% C.L., respectively. In addition, we compare the constraining power of measurements of the full- shape galaxy power spectrum versus the BAO signature, from the BOSS survey. Even though the latest BOSS full-shape measurements cover a larger volume and benefit from smaller error bars compared to previous similar measurements, the analysis method commonly adopted results in their constraining power still being less powerful than that of the extracted BAO signal. Our work uses only cosmological data; imposing the constraint M-nu > 0.06 eV from oscillations data would raise the quoted upper bounds by O(0.1 sigma) and would not affect our conclusions.

  • 21.
    Vagnozzi, Sunny
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Cambridge, United Kingdom.
    Visinelli, Luca
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden; University of Amsterdam, The Netherlands.
    Hunting for extra dimensions in the shadow of M872019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 2, article id 024020Article in journal (Refereed)
    Abstract [en]

    The Event Horizon Telescope has recently provided the first image of the dark shadow around the supermassive black hole M87*. The observation of a highly circular shadow provides strong limits on deviations of M87*'s quadrupole moment from the Kerr value. We show that the absence of such a deviation can be used to constrain the physics of extra dimensions of spacetime. Focusing on the Randall-Sundrum AdS(5) brane-world scenario, we show that the observation of M87*'s dark shadow sets the limit l less than or similar to 170 AU, where l is the AdS(5) curvature radius. This limit is among the first quantitative constraints on exotic physics obtained from the extraordinary first ever image of the dark shadow of a black hole.

  • 22.
    Visinelli, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Bolis, Nadia
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Brane-world extra dimensions in light of GW1708172018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, no 6, article id 064039Article in journal (Refereed)
    Abstract [en]

    The search for extra dimensions is a challenging endeavor to probe physics beyond the Standard Model. The joint detection of gravitational waves (GW) and electromagnetic (EM) signals from the merging of a binary system of compact objects like neutron stars can help constrain the geometry of extra dimensions beyond our 3 + 1 spacetime ones. A theoretically well-motivated possibility is that our observable Universe is a 3 + 1-dimensional hypersurface, or brane, embedded in a higher 4 + 1-dimensional antide Sitter (AdS(5)) spacetime, in which gravity is the only force which propagates through the infinite bulk space, while other forces are confined to the brane. In these types of brane-world models, GW and EM signals between two points on the brane would, in general, travel different paths. This would result in a time lag between the detection of GW and EM signals emitted simultaneously from the same source. We consider the recent near-simultaneous detection of the GW event GW170817 from the LIGO/Virgo collaboration, and its EM counterpart, the short gamma-ray burst GRB170817A detected by the Fermi Gamma-ray Burst Monitor and the International Gamma-Ray Astrophysics Laboratory Anti-Coincidence Shield spectrometer. Assuming the standard.-cold dark matter scenario and performing a likelihood analysis which takes into account astrophysical uncertainties associated to the measured time lag, we set an upper limit of l less than or similar to 0.535 Mpc at 68% confidence level on the AdS(5) radius of curvature l. Although the bound is not competitive with current Solar System constraints, it is the first time that data from a multimessenger GW-EM measurement is used to constrain extra-dimensional models. Thus, our work provides a proof of principle for the possibility of using multimessenger astronomy for probing the geometry of our space-time.

  • 23.
    Visinelli, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Cosmological window onto the string axiverse and the supersymmetry breaking scale2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, no 6, article id 063517Article in journal (Refereed)
    Abstract [en]

    In the simplest picture, the masses of string axions populating the axiverse depend on two parameters: the supersymmetry-breaking scale M-susy and the action S of the string instantons responsible for breaking the axion shift symmetry. In this work, we explore whether cosmological data can be used to probe these two parameters. Adopting string-inspired flat priors on log(10) M-susy and S and imposing that M-susy be sub-Planckian, we find S = 198 +/- 28. These bounds suggest that cosmological data complemented with string-inspired priors select a quite narrow axion mass range within the axiverse, log(10)(m(a)/eV) = -21.5(-2.3)(+1.3). We find that M-susy remains unconstrained due to a fundamental parameter degeneracy with S. We explore the significant impact of other choices of priors on the results, and we comment on similar findings in recent previous literature.

  • 24.
    Visinelli, Luca
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden.
    Vagnozzi, Sunny
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Cambridge, UK.
    Danielsson, Ulf
    Revisiting a Negative Cosmological Constant from Low-Redshift Data2019In: Symmetry, ISSN 2073-8994, E-ISSN 2073-8994, Vol. 11, no 8, article id 1035Article in journal (Refereed)
    Abstract [en]

    Persisting tensions between high-redshift and low-redshift cosmological observations suggest the dark energy sector of the Universe might be more complex than the positive cosmological constant of the ?CDM model. Motivated by string theory, wherein symmetry considerations make consistent AdS backgrounds (i.e., maximally-symmetric spacetimes with a negative cosmological constant) ubiquitous, we explore a scenario where the dark energy sector consists of two components: a negative cosmological constant, with a dark energy component with equation of state w phi on top. We test the consistency of the model against low-redshift baryon acoustic oscillation and Type Ia supernovae distance measurements, assessing two alternative choices of distance anchors: the sound horizon at baryon drag determined by the Planck collaboration and the Hubble constant determined by the SH0ES program. We find no evidence for a negative cosmological constant and mild indications for an effective phantom dark energy component on top. A model comparison analysis reveals that the ?CDM model is favoured over our negative cosmological constant model. While our results are inconclusive, should low-redshift tensions persist with future data, it would be worth reconsidering and further refining our toy negative cosmological constant model by considering realistic string constructions.

  • 25. Yang, Weiqiang
    et al.
    Pan, Supriya
    Di Valentino, Eleonora
    Nunes, Rafael C.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mota, David F.
    Tale of stable interacting dark energy, observational signatures, and the H-0 tension2018In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 9, article id 019Article in journal (Refereed)
    Abstract [en]

    We investigate the observational consequences of a novel class of stable interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE). In the first part of our work, we start by considering two IDE models which are known to present early-time linear perturbation instabilities. Applying a transformation depending on the dark energy equation of state (EoS) to the DM-DE coupling, we then obtain two novel stable IDE models. Subsequently, we derive robust and accurate constraints on the parameters of these models, assuming a constant EoS w(x) for the DE fluid, in light of some of the most recent publicly available cosmological data. These include Cosmic Microwave Background (CMB) temperature and polarization anisotropy measurements from the Planck satellite, a selection of Baryon Acoustic Oscillation measurements, Supernovae Type-Ia luminosity distance measurements from the JLA sample, and measurements of the Hubble parameter up to redshift 2 from cosmic chronometers. Our analysis displays a mild preference for the DE fluid residing in the phantom region (w(x) < -1), with significance up to 95% confidence level, while we obtain new upper limits on the coupling parameter between the dark components. The preference for a phantom DE suggests a coupling function Q < 0, thus a scenario where energy flows from the DE to the DM. We also examine the possibility of addressing the H-0 and sigma(8) tensions, finding that only the former can be partially alleviated. Finally, we perform a Bayesian model comparison analysis to quantify the possible preference for the two IDE models against the standard concordance ACDM model, finding that the latter is always preferred with the strength of the evidence ranging from positive to very strong.

  • 26. Yang, Weiqiang
    et al.
    Vagnozzi, Sunny
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Cambridge, United Kingdom.
    Di Valentino, Eleonora
    Nunes, Rafael C.
    Pang, Supriya
    Mota, David F.
    Listening to the sound of dark sector interactions with gravitational wave standard sirens2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 037Article in journal (Refereed)
    Abstract [en]

    We consider two stable Interacting Dark Matter-Dark Energy models and confront them against current Cosmic Microwave Background data from the Planck satellite. We then generate luminosity distance measurements from O(10(3)) mock Gravitational Wave events matching the expected sensitivity of the proposed Einstein Telescope. We use these to forecast how the addition of Gravitational Wave standard sirens data can improve current limits on the Dark Matter-Dark Energy coupling strength (xi). We find that the addition of Gravitational Waves data can reduce the current uncertainty by a factor of 5. Moreover, if the underlying cosmological model truly features Dark Matter-Dark Energy interactions with a value of xi within the currently allowed 1 sigma upper limit, the addition of Gravitational Wave data would help disentangle such an interaction from the standard case of no interaction at a significance of more than 3 sigma.

1 - 26 of 26
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