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  • 101. Ioannidou, Theodora
    et al.
    Niemi, Antti J.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden; Far Eastern Federal University, Russia; Beijing Institute of Technology, People’s Republic of China.
    Relation between discrete Frenet frames and the bi- Hamiltonian structure of the discrete nonlinear Schrodinger equation2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 8, article id 085003Article in journal (Refereed)
    Abstract [en]

    The discrete Frenet equation entails a local framing of a discrete, piecewise linear polygonal chain in terms of its bond and torsion angles. In particular, the tangent vector of a segment is akin to the classical O(3) spin variable. Thus there is a relation to the lattice Heisenberg model that can be used to model physical properties of the chain. On the other hand, the Heisenberg model is closely related to the discrete nonlinear Schrodinger equation. Here we apply these interrelations to develop a perspective on discrete chains dynamics: We employ the properties of a discrete chain in terms of a spinorial representation of the discrete Frenet equation, to introduce a bi-Hamiltonian structure for the discrete nonlinear Schrodinger equation, which we then use to produce integrable chain dynamics.

  • 102. Kahniashvili, Tina
    et al.
    Kar, Arjun
    Lavrelashvili, George
    Agarwal, Nishant
    Heisenberg, Lavinia
    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).
    Kosowsky, Arthur
    Cosmic expansion in extended quasidilaton massive gravity2015In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 91, no 4, article id 041301Article in journal (Refereed)
    Abstract [en]

    Quasidilaton massive gravity offers a physically well-defined gravitational theory with nonzero graviton mass. We present the full set of dynamical equations governing the expansion history of the Universe, valid during radiation domination, matter domination, and a late-time self-accelerating epoch related to the graviton mass. The existence of self-consistent solutions constrains the amplitude of the quasidilaton field and the graviton mass, as well as other model parameters. We point out that the effective mass of gravitational waves can be significantly larger than the graviton mass, opening the possibility that a single theory can explain both the late-time acceleration of cosmic expansion and modifications of structure growth leading to the suppression of large-angle correlations observed in the cosmic microwave background.

  • 103.
    Kühnel, Florian
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). KTH Royal Institute of Technology, Sweden.
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University of Michigan, USA.
    Constraints on primordial black holes with extended mass functions2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 8, article id 083508Article in journal (Refereed)
    Abstract [en]

    Constraints on primordial black holes in the range 10(-18) M circle dot to 10(3) M circle dot are reevaluated for a general class of extended mass functions. Whereas previous work has assumed that PBHs are produced with one single mass, instead there is expected to be a range of masses even in the case of production from a single mechanism; constraints therefore change from previous literature. Although tightly constrained in the majority of cases, it is shown that, even under conservative assumptions, primordial black holes in the mass range 10(-10) M circle dot to 10(-8) M circle dot could still constitute the entirety of the dark matter. This stresses both the importance for a comprehensive reevaluation of all respective constraints that have previously been evaluated only for a monochromatic mass function and the need to obtain more constraints in the allowed mass range.

  • 104.
    Makonyi, Karoly
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Preston, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Tegnér, Per-Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Wölbing, Dirk
    Stockholm University, Faculty of Science, Department of Physics. Stockholm Univ, Stockholm, Sweden.
    Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 3, article id 032003Article in journal (Refereed)
    Abstract [en]

    The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.

  • 105. María Ezquiaga, Jose
    et al.
    García-Bellido, Juan
    Zumalacárregui, Miguel
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Berkeley Center for Cosmological Physics and University of California at Berkeley, USA.
    Field redefinitions in theories beyond Einstein gravity using the language of differential forms2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 8, article id 084039Article in journal (Refereed)
    Abstract [en]

    We study the role of field redefinitions in general scalar-tensor theories. In particular, we first focus on the class of field redefinitions linear in the spin-2 field and involving derivatives of the spin-0 mode, generically known as disformal transformations. We start by defining the action of a disformal transformation in the tangent space. Then, we take advantage of the great economy of means of the language of differential forms to compute the full transformation of Horndeski's theory under general disformal transformations. We obtain that Horndeski's action maps onto itself modulo a reduced set of non-Horndeski Lagrangians. These new Lagrangians are found to be invariant under disformal transformation that depend only in the first derivatives of the scalar. Moreover, these combinations of Lagrangians precisely appear when expressing in our basis the constraints of the recently proposed extended scalar-tensor theories. These results allow us to classify the different orbits of scalar-tensor theories invariant under particular disformal transformations, namely, the special disformal, kinetic disformal, and disformal Horndeski orbits. In addition, we consider generalizations of this framework. We find that there are possible well-defined extended disformal transformations that have not been considered in the literature. However, they generically cannot link Horndeski theory with extended scalar-tensor theories. Finally, we study further generalizations in which extra fields with different spin are included. These field redefinitions can be used to connect different gravity theories such as multiscalar-tensor theories, generalized Proca theories, and bigravity. We discuss how the formalism of differential forms could be useful for future developments in these lines.

  • 106.
    Millar, Alexander
    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).
    Raffelt, Georg
    Stodolsky, Leo
    Vitagliano, Edoardo
    Neutrino mass from bremsstrahlung endpoint in coherent scattering on nuclei2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 12, article id 123006Article in journal (Refereed)
    Abstract [en]

    We calculate the coherent bremsstrahlung process nu + N -> N + nu + gamma off a nucleus H with the aim of revealing the neutrino mass via the photon endpoint spectrum. Unfortunately, the large required power of a monochromatic neutrino source and/or large detector mass make it difficult to compete with traditional electron-spectrum endpoint measurements in nuclear beta decay. Our neutral-current process distinguishes between Dirac and Majorana neutrinos, but the change of the photon spectrum is of the order of m(nu)/E-nu and thus very small, despite the final-state neutrino coming to rest at the photon endpoint. So the Dirac-Majorana confusion theorem remains intact even if E-nu >> m(nu) my applies only for the initial state.

  • 107. Mushtukov, Alexander A.
    et al.
    Nagirner, Dmitrij I.
    Poutanen, Juri
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Turku, Finland.
    Compton scattering S matrix and cross section in strong magnetic field2016In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 93, no 10, article id 105003Article in journal (Refereed)
    Abstract [en]

    Compton scattering of polarized radiation in a strong magnetic field is considered. The recipe for calculation of the scattering matrix elements, the differential and total cross sections based on quantum electrodynamic second-order perturbation theory is presented for the case of arbitrary initial and final Landau level, electron momentum along the field and photon momentum. Photon polarization and electron spin state are taken into account. The correct dependence of natural Landau level width on the electron spin state is taken into account in a general case of arbitrary initial photon momentum for the first time. A number of steps in the calculations were simplified analytically making the presented recipe easy to use. The redistribution functions over the photon energy, momentum and polarization states are presented and discussed. The paper generalizes already known results and offers a basis for the accurate calculation of radiation transfer in a strong B field, for example, in strongly magnetized neutron stars.

  • 108. Nersisyan, Henrik
    et al.
    Akrami, Yashar
    Amendola, Luca
    Koivisto, Tomi S.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Rubio, Javier
    Solomon, Adam R.
    Instabilities in tensorial nonlocal gravity2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 4, article id 043539Article in journal (Refereed)
    Abstract [en]

    We discuss the cosmological implications of nonlocal modifications of general relativity containing tensorial structures. Assuming the presence of standard radiation-and matter-dominated eras, we show that, except in very particular cases, the nonlocal terms contribute a rapidly growing energy density. These models therefore generically do not have a stable cosmological evolution.

  • 109.
    Ong, Yen Chin
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Yangzhou University, China.
    Yao, Yuan
    Generalized uncertainty principle and white dwarfs redux: How the cosmological constant protects the Chandrasekhar limit2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 12, article id 126018Article in journal (Refereed)
    Abstract [en]

    It was previously argued that generalized uncertainty principle (GUP) with a positive parameter removes the Chandrasekhar limit. One way to restore the limit is by taking the GUP parameter to be negative. In this work we discuss an alternative method that achieves the same effect: by including a cosmological constant term in the GUP (known as extended GUP in the literature). We show that an arbitrarily small but nonzero cosmological constant can restore the Chandrasekhar limit. We also remark that if the extended GUP is correct, then the existence of white dwarfs gives an upper bound for the cosmological constant, which-while still large compared to observation-is approximately 86 orders of magnitude smaller than the natural scale.

  • 110. Porter, T. A.
    et al.
    Rowell, G. P.
    Jóhannesson, Guðlaugur
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Iceland, Iceland.
    Moskalenko, I. V.
    Galactic PeVatrons and helping to find them: Effects of galactic absorption on the observed spectra of very high energy gamma-ray sources2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 4, article id 041302Article in journal (Refereed)
    Abstract [en]

    Identification of the cosmic-ray (CR) PeVatrons, which are sources capable of accelerating particles to similar to 10(15) eV energies and higher, may lead to resolving the long-standing question of the origin of the spectral feature in the all-particle CR spectrum known as the knee. Because CRs with these energies are deflected by interstellar magnetic fields identification of individual sources and determination of their spectral characteristics is more likely via very high energy gamma-ray emissions, which provide the necessary directional information. However, pair production on the interstellar radiation field (ISRF) and cosmic microwave background (CMB) leads to steepening of the high energy tails of gamma-ray spectra, and should be corrected for to enable true properties of the spectrum at the source to be recovered. Employing recently developed three-dimensional ISRF models this paper quantifies the pair-absorption effect on spectra for sources in the Galactic center (GC) direction at 8.5 and 23.5 kpc distances, with the latter corresponding to the far side of the Galactic stellar disc where it is expected that discrimination of spectral features >10 TeV is possible by the forthcoming Cherenkov Telescope Array (CTA). The estimates made suggest spectral cutoffs could be underestimated by factors of a few in the energy range so far sampled by TeV gamma-ray telescopes. As an example to illustrate this, the recent HESS measurements of diffuse gamma-ray emissions possibly associated with injection of CRs nearby Sgr A* are ISRF corrected, and estimates of the spectral cutoff are reevaluated. It is found that it could be higher by up to a factor of similar to 2, indicating that these emissions may be consistent with a CR accelerator with a spectral cutoff of at least 1 PeV at the 95% confidence level.

  • 111. Ramberg, Nicklas
    et al.
    Visinelli, Luca
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden.
    Probing the early Universe with axion physics and gravitational waves2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, no 12, article id 123513Article in journal (Refereed)
    Abstract [en]

    We show results for the expected reach of the network of experiments that is being set up globally with the aim of detecting the invisible axion, in light of a nonstandard thermal history of the universe. Assuming that the axion is the dark matter, we discuss the reach of a successful detection by a given experimental setup in a particular axion mass window for different modifications of the cosmological background before primordial nucleosynthesis occurred. Results are presented both in the case where the present energy budget in cold axions is produced through the vacuum realignment mechanism alone, or in the case in which axionic strings also provide with additional contributions to the axion energy density. We also show that in some cosmological models, the spectrum of gravitational waves from the axionic string network would be within reach of the future network of detectors like LISA and DECIGO-BBO. We conclude that some scenarios describing the early universe can be probed jointly by the experimental efforts on axion detection and by gravity wave multimessenger astronomy.

  • 112. Reig, Mario
    et al.
    Valle, José W. F.
    Wilczek, Frank
    Stockholm University, Faculty of Science, Department of Physics. Massachusetts Institute of Technology, USA; Tsung-Dao Lee Institute and Wilczek Quantum Center, China; Arizona State University, USA.
    SO(3) family symmetry and axions2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 9, article id 095008Article in journal (Refereed)
    Abstract [en]

    Motivated by the idea of comprehensive unification, we study a gauged SO(3) flavor extension of the extended Standard Model, including right-handed neutrinos and a Peccei-Quinn symmetry with simple charge assignments. The model accommodates the observed fermion masses and mixings and yields a characteristic, successful relation among them. The Peccei-Quinn symmetry is an essential ingredient.

  • 113.
    Rosquist, Kjell
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bini, Donato
    Mashhoon, Bahram
    Twisted gravitational waves of Petrov type D2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 6, article id 064039Article in journal (Refereed)
    Abstract [en]

    Twisted gravitational waves (TGWs) are nonplanar unidirectional Ricci-flat solutions of general relativity. Thus far only TGWs of Petrov type II are implicitly known that depend on a solution of a partial differential equation and have wave fronts with negative Gaussian curvature. A special Petrov type D class of such solutions that depends on an arbitrary function is explicitly studied in this paper and its Killing vectors are worked out. Moreover, we concentrate on two solutions of this class, namely, the Harrison solution and a simpler solution we call the w-metric and determine their Penrose plane-wave limits. The corresponding transition from a nonplanar TGW to a plane gravitational wave is elucidated.

  • 114. Scaffidi, Andre
    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.
    Li, Jinmian
    Savage, Christopher
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    White, Martin
    Williams, Anthony G.
    Gamma rays from muons from WIMPs: Implementation of radiative muon decays for dark matter analyses2016In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 93, no 11, article id 115024Article in journal (Refereed)
    Abstract [en]

    Dark matter searches in gamma ray final states often make use of the fact that photons can be produced from final state muons. Modern Monte Carlo generators and dark matter codes include the effects of final state radiation from muons produced in the dark matter annihilation process itself, but neglect the O(1%) radiative correction that arises from the subsequent muon decay. After implementing this correction we demonstrate the effect that it can have on dark matter phenomenology by considering the case of dark matter annihilation to four muons via scalar mediator production. We first show that the AMS-02 positron excess can no longer easily be made consistent with this final state once the Fermi-LAT dwarf limits are calculated with the inclusion of radiative muon decays, and we next show that the Fermi-LAT galactic center gamma excess can be improved with this final state after inclusion of the same effect. We provide code and tables for the implementation of this effect in the popular dark matter code micrOMEGAs, providing a solution for any model producing final state muons.

  • 115. Taylor, Peter L.
    et al.
    Kitching, Thomas D.
    Alsing, Justin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Imperial College London, United Kingdom.
    Wandelt, Benjamin D.
    Feeney, Stephen M.
    McEwen, Jason D.
    Cosmic shear: Inference from forward models2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 2, article id 023519Article in journal (Refereed)
    Abstract [en]

    Density-estimation likelihood-free inference (DELFI) has recently been proposed as an efficient method for simulation-based cosmological parameter inference. Compared to the standard likelihood-based Markov chain Monte Carlo (MCMC) approach, DELFI has several advantages: it is highly parallelizable, there is no need to assume a possibly incorrect functional form for the likelihood, and complicated effects (e.g., the mask and detector systematics) are easier to handle with forward models. In light of this, we present two DELFI pipelines to perform weak lensing parameter inference with log-normal realizations of the tomographic shear field-using the C-l summary statistic. The first pipeline accounts for the non-Gaussianities of the shear field, intrinsic alignments, and photometric-redshift error. We validate that it is accurate enough for Stage III experiments and estimate that O(1000) simulations are needed to perform inference on Stage IV data. By comparing the second DELFI pipeline, which makes no assumption about the functional form of the likelihood, with the standard MCMC approach, which assumes a Gaussian likelihood, we test the impact of the Gaussian likelihood approximation in the MCMC analysis. We find it has a negligible impact on Stage IV parameter constraints. Our pipeline is a step towards seamlessly propagating all data-processing, instrumental, theoretical, and astrophysical systematics through to the final parameter constraints.

  • 116.
    Torsello, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kocic, Mikica
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Högås, Marcus
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Spacetime symmetries and topology in bimetric relativity2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, no 8, article id 084022Article in journal (Refereed)
    Abstract [en]

    We explore spacetime symmetries and topologies of the two metric sectors in Hassan-Rosen bimetric theory. We show that, in vacuum, the two sectors can either share or have separate spacetime symmetries. If stress-energy tensors are present, a third case can arise, with different spacetime symmetries within the same sector. This raises the question of the best definition of spacetime symmetry in Hassan-Rosen bimetric theory. We emphasize the possibility of imposing ansatzes and looking for solutions having different Killing vector fields or different isometries in the two sectors, which has gained little attention so far. We also point out that the topology of spacetime imposes a constraint on possible metric combinations.

  • 117.
    Torsello, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kocic, Mikica
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Classification and asymptotic structure of black holes in bimetric theory2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 96, no 6, article id 064003Article in journal (Refereed)
    Abstract [en]

    We study general properties of static and spherically symmetric bidiagonal black holes in Hassan-Rosen bimetric theory by means of a new method. In particular, we explore the behavior of the black hole solutions both at the common Killing horizon and at the large radii. The former study was never done before and leads to a new classification for black holes within the bidiagonal ansatz. The latter study shows that, among the great variety of the black hole solutions, the only solutions converging to Minkowski, anti-de Sitter, and de Sitter spacetimes at large radii are those of general relativity, i.e., the Schwarzschild, Schwarzschild-anti-de Sitter and Schwarzschild-de Sitter solutions. Moreover, we present a proposition, whose validity is not limited to black hole solutions, which establishes the relation between the curvature singularities of the two metrics and the invertibility of their interaction potential.

  • 118.
    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.

  • 119.
    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.

  • 120.
    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.

  • 121.
    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 Helsinki, Finland.
    Light axion-like dark matter must be present during inflation2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 96, no 2, article id 023013Article in journal (Refereed)
    Abstract [en]

    Axion-like particles (ALPs) might constitute the totality of the cold dark matter (CDM) observed. The parameter space of ALPs depends on the mass of the particle In and on the energy scale of inflation Hi, the latter being hound by the nondetection of primordial gravitational waves. We show that the hound on H-I implies the existence of a mass scale (m) over bar (chi) = 10 neV-0.5 peV, depending on the ALP susceptibility 7, such that the energy density of ALPs of mass smaller than (m) over bar (chi) is too low to explain the present CDIVI. budget, if the ALP field has originated after the end of inflation. This bound affects ultra-light axions (ULAs), which have recently regained popularity as CDM candidates. Light On (m < m(chi)) ALPs can then be CDM candidates only if the ALP field has already originated during the inflationary period, in which case the parameter space is constrained by the nondetection of axion isocurvature fluctuations. We comment on the effects on these bounds from additional physics beyond the standard model, besides ALPs.

  • 122.
    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.

  • 123.
    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.

  • 124.
    Winkler, Martin Wolfgang
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Decay and detection of a light scalar boson mixing with the Higgs boson2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, no 1, article id 015018Article in journal (Refereed)
    Abstract [en]

    The simplest extension of the standard model consists in adding one singlet scalar field which mixes with the Higgs boson. O(GeV) masses of the new scalar carry strong motivation from relaxion, dark matter and inflation models. The decay of a GeV scalar is, however, notoriously difficult to address since, at this mass scale, the chiral expansion breaks down and perturbative QCD does not apply. Existing estimates of the GeV scalar decay rate disagree by several orders of magnitude. In this work, we perform a new dispersive analysis in order to strongly reduce these uncertainties and to address discrepancies in earlier results. We will update existing limits on light scalars and future experimental sensitivities which are in some cases strongly affected by the new-found decay rates. The meson form factors provided in this work, can be used to generalize our findings to non-universally coupled light scalars.

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