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  • 101. Chen, Hui-Huang
    et al.
    Ouyang, Hao
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Wu, Jun-Bao
    Open spin chains from determinant like operators in ABJM theory2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 10, article id 106012Article in journal (Refereed)
    Abstract [en]

    We study the mixing problem of the determinantlike operators in ABJM theory to two-loop order in the scalar sector. The gravity duals of these operators are open strings attached to the maximal giant graviton, which is a D4-brane wrapping a CP2 inside CP3 in our case. The anomalous dimension matrix of these operators can be regarded as an open spin chain Hamiltonian. We provide strong evidence of its integrability based on coordinate Bethe ansatz method and boundary Yang-Baxter equations.

  • 102. Davison, Richard A.
    et al.
    Gentle, Simon A.
    Goutéraux, Blaise
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Université Paris-Saclay, France.
    Impact of irrelevant deformations on thermodynamics and transport in holographic quantum critical states2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 8, article id 086020Article in journal (Refereed)
    Abstract [en]

    We study thermodynamic and transport observables of quantum critical states that arise in the infrared limit of holographic renormalization group flows. Although these observables are expected to exhibit quantum critical scaling, there are a number of cases in which their frequency and temperature dependences are in apparent contradiction with scaling theories. We study two different classes of examples and show in both cases that the apparent breakdown of scaling is a consequence of the dependence of observables on an irrelevant deformation of the quantum critical state. By assigning scaling dimensions to the near-horizon observables, we formulate improved scaling theories that are completely consistent with all explicit holographic results once the dependence on the dangerously irrelevant coupling is properly accounted for. In addition to governing thermodynamic and transport phenomena in these states, we show that the dangerously irrelevant coupling also controls late-time equilibration, which occurs at a rate parametrically slower than the temperature 1/tau(eq) << T. At very late times, transport is diffusion-dominated, with a diffusivity that can be written simply in terms of tau(eq) and the butterfly velocity, D similar to v(B)(2)tau(eq). We conjecture that in such cases there exists a long-lived, propagating collective mode with velocity v, and in this case the relation D = v(s)(2)tau(eq) holds exactly in the limit tau T-eq >> 1.

  • 103. De Jonckheere, Tim
    et al.
    Lindgren, Jonathan
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Entanglement entropy in inhomogeneous quenches in AdS(3)/CFT22018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 10, article id 106006Article in journal (Refereed)
    Abstract [en]

    We compute entanglement entropy and differential entropy in inhomogeneous holographic quenches in AdS(3)/CFT2. The quenches are arbitrarily inhomogeneous and modeled by an infalling shell of massless nonrotating matter where the final state is not dual to a static black hole but rather to a black hole with time-dependent stress-energy tensor modes. We study the entanglement entropy of an interval and differential entropy of a family of intervals analytically when the inhomogeneities have a perturbative amplitude and numerically for nonperturbative inhomogeneities. While we are in principle able to study these quantities for any inhomogeneities, we discuss two concrete examples: an oscillatory quench and a bilocal quench. Both cases display saturation towards a steady state but do not fully thermalize. Depending on the location and size of the interval, the entanglement entropy displays a variety of interesting phenomena such as plateau phases, bumps, and discontinuities in its first derivative with respect to time.

  • 104. de Rham, Claudia
    et al.
    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).
    Ribeiro, Raquel H.
    Ghosts and matter couplings in massive gravity, bigravity and multigravity2014In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 90, no 12, article id 124042Article in journal (Refereed)
    Abstract [en]

    Recently, several works have investigated the coupling to matter in ghost-free massive bigravity and multigravity and a new effective coupling to matter has been proposed. In this paper we clarify some confusion on the existence and the implications of a ghost above the strong coupling scale. We confirm that the standard constraint which is otherwise typically present in this type of theories disappears on generic backgrounds as soon as this new coupling is considered. This implies the reemergence of the BoulwareDeser ghost. Nevertheless the absence of ghost in the decoupling limit implies that the cutoff scale (if identified with the scale at which the ghost enters) is higher than the strong coupling scale. Therefore there is a valid interesting region of applicability for these couplings at scales below the cutoff.

  • 105. Deaton, M. Brett
    et al.
    O'Connor, Evan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). North Carolina State University, USA.
    Zhu, Y. L.
    Bohn, Andy
    Jesse, Jerred
    Foucart, Francois
    Duez, Matthew D.
    McLaughlin, G. C.
    Elastic scattering in general relativistic ray tracing for neutrinos2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 10, article id 103014Article in journal (Refereed)
    Abstract [en]

    We present a covariant ray tracing algorithm for computing high-resolution neutrino distributions in general relativistic numerical spacetimes with hydrodynamical sources. Our formulation treats the very important effect of elastic scattering of neutrinos off of nuclei and nucleons (changing the neutrino's direction but not energy) by incorporating estimates of the background neutrino fields. Background fields provide information about the spectra and intensities of the neutrinos scattered into each ray. These background fields may be taken from a low-order moment simulation or be ignored, in which case the method reduces to a standard state-of-the-art ray tracing formulation. The method handles radiation in regimes spanning optically thick to optically thin. We test the new code, highlight its strengths and weaknesses, and apply it to a simulation of a neutron-star merger to compute neutrino fluxes and spectra, and to demonstrate a neutrino flavor oscillation calculation. In that environment, we find qualitatively different fluxes, spectra, and oscillation behaviors when elastic scattering is included.

  • 106. Desmond, Harry
    et al.
    Ferreira, Pedro G.
    Lavaux, Guilhem
    Jasche, Jens
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Technische Universität München, Germany.
    Fifth force constraints from galaxy warps2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 8, article id 083010Article in journal (Refereed)
    Abstract [en]

    Intragalaxy signals contain a wealth of information on fundamental physics, both the dark sector and the nature of gravity. While so far largely unexplored, such probes are set to rise dramatically in importance as upcoming surveys provide data of unprecedented quantity and quality on galaxy structure and dynamics. In this paper, we use warping of stellar disks to test the chameleon-or symmetron-screened fifth forces which generically arise when new fields couple to matter. We take r-band images of mostly late-type galaxies from the Nasa Sloan Atlas and develop an automated algorithm to quantify the degree of U-shaped warping they exhibit. We then forward model the warp signal as a function of fifth-force strength, Delta G/G(N), and range, lambda(C), and the gravitational environments and internal properties of the galaxies, including full propagation of the non-Gaussian uncertainties. Convolving this fifth-force likelihood function with a Gaussian describing astrophysical and observational noise and then constraining Delta G/G(N) and lambda(C) by Markov chain Monte Carlo, we find the overall likelihood to be significantly increased (Delta log (L) similar or equal to 20) by adding a screened fifth force with lambda(C) similar or equal to 2 Mpc and Delta G/G(N) similar or equal to 0.01. The variation of Delta log (L) with lambda(C) is quantitatively as expected from the correlation of the magnitude of the fifth-force field with the force's range, and a similar model without screening achieves no increase in likelihood over the General Relativistic case Delta G = 0. Although these results are in good agreement with a previous analysis of the same model using offsets between galaxies' stellar and gas mass centroids [H. Desmond et al., Phys. Rev. D 98, 064015 (2018).], we caution that the effects of confounding baryonic and dark matter physics must be thoroughly investigated for the results of the inference to be unambiguous.

  • 107. Desmond, Harry
    et al.
    Ferreira, Pedro G.
    Lavaux, Guilhem
    Jasche, Jens
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Technische Universität München, Germany.
    Fifth force constraints from the separation of galaxy mass components2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 6, article id 064015Article in journal (Refereed)
    Abstract [en]

    One of the most common consequences of extensions to the standard models of particle physics or cosmology is the emergence of a fifth force. While generic fifth forces are tightly constrained at Solar System scales and below, they may escape detection by means of a screening mechanism which effectively removes them in dense environments. We constrain the strength Delta G/G(N) and range lambda(C) of a fifth force with Yukawa coupling arising from a chameleon-or symmetron-screened scalar field-as well as an unscreened fifth force with differential coupling to galactic mass components-by searching for the displacement it predicts between galaxies' stellar and gas mass centroids. Taking data from the Alfalfa survey of neutral atomic hydrogen (HI), identifying galaxies' gravitational environments with the maps of [H. Desmond, P.G. Ferreira, G. Lavaux, and J. Jasche, Mon. Not. R. Astron. Soc. 474, 3152 (2018)] and forward modeling with a Bayesian likelihood framework, we find, with screening included, 6.6 sigma evidence for Delta G > 0 at lambda(C) greater than or similar to 2 Mpc. The maximum-likelihood Delta G/G(N) is 0.025. A similar fifth force model without screening gives no increase in likelihood over the case Delta G = 0 for any lambda(C). Although we validate this result by several methods, we do not claim screened modified gravity to provide the only possible explanation for the data: this conclusion would require knowing that the signal could not be produced by galaxy formation physics. We show also the results of a more conservative-though less well-motivated-noise model which yields only upper limits on Delta G/G(N), ranging from similar to 10(-1) for lambda(C) similar or equal to 0.5 Mpc to similar to few x 10(-4) at lambda(C) similar or equal to 50 Mpc. Corresponding models without screening receive the somewhat stronger bounds similar to few x 10(-3) and similar to few x 10(-4) respectively. We show how these constraints may be improved by future galaxy surveys and identify the key features of an observational program for directly constraining fifth forces on scales beyond the Solar System. This paper provides a complete description of the analysis summarized in [H. Desmond, P.G. Ferreira, G. Lavaux, and J. Jasche, arXiv:1802.07206].

  • 108.
    Di Vecchia, Paolo
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    Multiloop soft theorem of the dilaton in the bosonic string2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 4, article id 041902Article in journal (Refereed)
    Abstract [en]

    We show that by fixing the multiloop Green function in the closed bosonic string to be Arakelov's Green function, one obtains factorization of scattering amplitudes with a softly emitted dilaton to the same level as with a graviton to all loop order. This extends our previous analysis at one loop to all loop orders and confirms that some high-energy quantum symmetry in the bosonic string protects the factorization of amplitudes with softly emitted dilatons.

  • 109. Dienes, Keith R.
    et al.
    Kumar, Jason
    Stengel, Patrick
    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.
    Thomas, Brooks
    Cosmological constraints on unstable particles: Numerical bounds and analytic approximations2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, no 4, article id 043513Article in journal (Refereed)
    Abstract [en]

    Many extensions of the Standard Model predict large numbers of additional unstable particles whose decays in the early universe are tightly constrained by observational data. For example, the decays of such particles can alter the ratios of light-element abundances, give rise to distortions in the cosmic microwave background, alter the ionization history of the Universe, and contribute to the diffuse photon flux. Constraints on new physics from such considerations are typically derived for a single unstable particle species with a single well-defined mass and characteristic lifetime. In this paper, by contrast, we investigate the cosmological constraints on theories involving entire ensembles of decaying particles-ensembles which span potentially broad ranges of masses and lifetimes. In addition to providing a detailed numerical analysis of these constraints, we also formulate a set of simple analytic approximations for these constraints which may be applied to generic ensembles of unstable particles which decay into electromagnetically interacting final states. We then illustrate how these analytic approximations can be used to constrain a variety of toy scenarios for physics beyond the Standard Model. For ease of reference, we also compile our results in the form of a table which can be consulted independently of the rest of the paper. It is thus our hope that this work might serve as a useful reference for future model-builders concerned with cosmological constraints on decaying particles, regardless of the particular model under study.

  • 110.
    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.

  • 111. 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.

  • 112. Handley, Will J.
    et al.
    Lasenby, Anthony N.
    Peiris, Hiranya V.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University College London, United Kingdom.
    Hobson, Michael P.
    Bayesian inflationary reconstructions from Planck 2018 data2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 10, article id 103511Article in journal (Refereed)
    Abstract [en]

    We present three nonparametric Bayesian primordial reconstructions using Planck 2018 polarization data: linear spline primordial power spectrum reconstructions, cubic spline inflationary potential reconstructions, and sharp-featured primordial power spectrum reconstructions. All three methods conditionally show hints of an oscillatory feature in the primordial power spectrum in the multipole range l similar to 20 to l similar to 50, which is to some extent preserved upon marginalization. We find no evidence for deviations from a pure power law across a broad observable window (50 less than or similar to l less than or similar to 2000), but find that parametrizations are preferred which are able to account for lack of resolution at large angular scales due to cosmic variance, and at small angular scales due to Planck instrument noise. Furthermore, the late-time cosmological parameters are unperturbed by these extensions to the primordial power spectrum. This work is intended to provide a background and give more details of the Bayesian primordial reconstruction work found in the Planck 2018 papers.

  • 113. Harko, Tiberiu
    et al.
    Koivisto, Tomi S.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Lobo, Francisco S. N.
    Olmo, Gonzalo J.
    Rubiera-Garcia, Diego
    Coupling matter in modified Q gravity2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 8, article id 084043Article in journal (Refereed)
    Abstract [en]

    We present a novel theory of gravity by considering an extension of symmetric teleparallel gravity. This is done by introducing, in the framework of the metric-affine formalism, a new class of theories where the nonmetricity Q is nonminimally coupled to the matter Lagrangian. More specifically, we consider a Lagrangian of the form L similar to f(1)(Q) + f(2)(Q)L-M, where f(1) and f(2) are generic functions of Q, and L-M is the matter Lagrangian. This nonminimal coupling entails the nonconservation of the energy-momentum tensor, and consequently the appearance of an extra force. The formulation of the gravity sector in terms of the Q instead of the curvature may result in subtle improvements of the theory. In the context of nonminimal matter couplings, we are therefore motivated to explore whether the new geometrical formulation in terms of the Q, when implemented also in the matter sector, would allow more universally consistent and viable realizations of the nonminimal coupling. Furthermore, we consider several cosmological applications by presenting the evolution equations and imposing specific functional forms of the functions f(1)(Q) and f(2)(Q), such as power-law and exponential dependencies of the nonminimal couplings. Cosmological solutions are considered in two general classes of models, and found to feature accelerating expansion at late times.

  • 114.
    Hossenfelder, Sabine
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Frankfurt Institute for Advanced Studies, Germany.
    Zingg, Tobias
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Helsinki, Finland.
    Analog models for holographic transport2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 5, article id 056015Article in journal (Refereed)
    Abstract [en]

    The gauge-gravity duality and analog gravity both relate a condensed matter system to a gravitational theory. This makes it possible to use gravity as an intermediary to establish a relation between two different condensed matter systems: the strongly coupled system from the gauge-gravity duality and the weakly coupled gravitational analog. We here offer some examples for relations between observables in the two different condensed matter systems. In particular, we show how the equations characterizing Green functions and fast order transport coefficients in holographic models can be mapped to those describing phenomena in an analog gravitational system, which allows, in principle, to obtain the former by measuring the latter.

  • 115. 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.

  • 116. 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.

  • 117. Kane, Gordon
    et al.
    Winkler, Martin Wolfgang
    Stockholm Univ, Oskar Klein Ctr Cosmoparticle Phys, Dept Phys, S-10691 Stockholm, Sweden.
    Deriving the inflaton in compactified M-theory with a de Sitter vacuum2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 6, article id 066005Article in journal (Refereed)
    Abstract [en]

    Compactifying M-theory on a manifold of G(2) holonomy gives a UV complete 4D theory. It is supersymmetric, with soft supersymmetry breaking via gaugino condensation that simultaneously stabilizes all moduli and generates a hierarchy between the Planck and the Fermi scale. It generically has gauge matter, chiral fermions, and several other important features of our world. Here we show that the theory also contains a successful inflaton, which is a linear combination of moduli closely aligned with the overall volume modulus of the compactified G(2) manifold. The scheme does not rely on ad hoc assumptions, but derives from an effective quantum theory of gravity. Inflation arises near an inflection point in the potential which can be deformed into a local minimum. This implies that a de Sitter vacuum can occur in the moduli potential even without uplifting. Generically present charged hidden sector matter generates a de Sitter vacuum as well.

  • 118. Koemans Collado, Arnau
    et al.
    Di Vecchia, Paolo
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Copenhagen, Denmark.
    Russo, Rodolfo
    Revisiting the second post-Minkowskian eikonal and the dynamics of binary black holes2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 6, article id 066028Article in journal (Refereed)
    Abstract [en]

    In this paper we study the two-body gravitational scattering of massive scalars with different masses in general spacetime dimensions. We focus on the Regge limit (eikonal regime) of the resulting scattering amplitudes and discuss how to extract the classical information representing the scattering of two black holes. We derive the leading eikonal and explicitly show the resummation of the first leading energy contribution up to second order in Newton's gravitational constant. We also calculate the subleading eikonal showing that in general spacetime dimensions it receives a nontrivial contribution from the box integral. From the eikonal we extract the two-body classical scattering angle between the two black holes up to the second post-Minkowskian order. Taking various probe-limits of the two-body scattering angles we are able to show agreement between our results and various results in the literature. We highlight that the box integral also has a log-divergent (in energy) contribution at subsubleading order which violates perturbative unitarity in the ultrarelativistic limit. We expect this term to play a role in the calculation of the eikonal at the third post-Minkowskian order.

  • 119.
    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.

  • 120.
    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.

  • 121. 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.

  • 122.
    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.

  • 123.
    Mortlock, Daniel J.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Imperial College London, United Kingdom.
    Feeney, Stephen M.
    Peiris, Hiranya V.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). University College London, United Kingdom.
    Williamson, Andrew R.
    Nissanke, Samaya M.
    Unbiased Hubble constant estimation from binary neutron star mergers2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 10, article id 103523Article in journal (Refereed)
    Abstract [en]

    Gravitational-wave (GW) observations of binary neutron star (BNS) mergers can be used to measure luminosity distances and hence, when coupled with estimates for the mergers' host redshifts, infer the Hubble constant H-0. These observations are, however, affected by GW measurement noise, uncertainties in host redshifts and peculiar velocities, and are potentially biased by selection effects and the misspecification of the cosmological model or the BNS population. The estimation of H-0 from samples of BNS mergers with optical counterparts is tested here by using a phenomenological model for the GW strains that captures both the data-driven event selection and the distance-inclination degeneracy, while being simple enough to facilitate large numbers of simulations. A rigorous Bayesian approach to analyzing the data from such simulated BNS merger samples is shown to yield results that are unbiased, have the appropriate uncertainties, and arc robust to model misspecification. Applying such methods to a sample of N similar or equal to 50 BNS merger events, as LIGO + Virgo could produce in the next similar to 5 years, should yield robust and accurate Hubble constant estimates that are precise to a level of less than or similar to 2 km s(-1) Mpc(-1), sufficient to reliably resolve the current tension between local and cosmological measurements of H-0.

  • 124. 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.

  • 125. 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.

  • 126.
    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.

  • 127. 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.

  • 128. 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.

  • 129. 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.

  • 130.
    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.

  • 131. 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.

  • 132. 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.

  • 133.
    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.

  • 134.
    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.

  • 135.
    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.

  • 136.
    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.

  • 137.
    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.

  • 138.
    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.

  • 139.
    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.

  • 140.
    Visinelli, Luca
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden; University of Amsterdam, Netherlands.
    Redondo, Javier
    Axion miniclusters in modified cosmological histories2020In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, no 2, article id 023008Article in journal (Refereed)
    Abstract [en]

    If the symmetry breaking leading to the origin of the axion dark matter field occurs after the end of inflation and is never restored, then overdensities in the axion field collapse to form dense objects known in the literature as axion miniclusters. The estimates of the typical minicluster mass and radius strongly depend on the details of the cosmology at which the onset of axion oscillations begin. In this work we study the properties and phenomenology of miniclusters in alternative cosmological histories and find that they can change by many orders of magnitude. Our findings have direct implications on current and future experimental searches and, in the case of discovery, could be used to learn something about the universe expansion prior to big bang nucleosynthesis.

  • 141.
    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.

  • 142. Westernacher-Schneider, John Ryan
    et al.
    O'Connor, Evan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    O'Sullivan, Erin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Tamborra, Irene
    Wu, Meng-Ru
    Couch, Sean M.
    Malmenbeck, Felix
    Multimessenger asteroseismology of core-collapse supernovae2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 12, article id 123009Article in journal (Refereed)
    Abstract [en]

    We investigate correlated gravitational wave and neutrino signals from rotating core-collapse supernovae with simulations. Using an improved mode identification procedure based on mode function matching, we show that a linear quadrupolar mode of the core produces a dual imprint on gravitational waves and neutrinos in the early post-bounce phase of the supernova. The angular harmonics of the neutrino emission are consistent with the mode energy around the neutrinospheres, which points to a mechanism for the imprint on neutrinos. Thus, neutrinos carry information about the mode amplitude in the outer region of the core, whereas gravitational waves probe deeper in. We also find that the best-fit mode function has a frequency bounded above by similar to 420 Hz, and yet the mode's frequency in our simulations is similar to 15% higher, due to the use of Newtonian hydrodynamics and a widely used pseudo-Newtonian gravity approximation. This overestimation is particularly important for the analysis of gravitational wave detectability and asteroseismology, pointing to limitations of pseudo-Newtonian approaches for these purposes, possibly even resulting in excitation of incorrect modes. In addition, mode frequency matching (as opposed to mode function matching) could be resulting in mode misidentification in recent work. Lastly, we evaluate the prospects of a multimessenger detection of the mode using current technology. The detection of the imprint on neutrinos is most challenging, with a maximum detection distance of similar to 1 kpc using the IceCube Neutrino Observatory. The maximum distance for detecting the complementary gravitational wave imprint is similar to 5 kpc using Advanced LIGO at design sensitivity.

  • 143.
    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.

123 101 - 143 of 143
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