Search Publications
Fifth force induced by a chameleon field on nested cylinders
Bergé, Joel; Pernot-Borràs, Martin; Uzan, Jean-Philippe +1 more
This article investigates the properties of a scalar fifth force that arises in a scalar tensor-theory with a chameleon screening mechanism in the context of gravity space missions like the MICROSCOPE experiment. In such an experiment, the propagation of the chameleon field inside the nested cylinders of the experiment causes a fifth force when th…
Testing the Keplerian disk hypothesis using x-ray reflection spectroscopy
Tripathi, Ashutosh; Zhou, Biao; Abdikamalov, Askar B. +3 more
The Novikov-Thorne model is the standard framework for the description of geometrically thin and optically thick accretion disks around black holes and is widely used to study the electromagnetic spectra of accreting black holes. One of the assumptions of the model is that the particles of the gas move on nearly geodesic circular orbits on the equ…
Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect dark matter searches
Petač, Mihael
We for the first time provide self-consistent axisymmetric phase-space distribution models for the Milky Way's dark matter (DM) halo which are carefully matched against the latest kinematic measurements through Bayesian analysis. By using broad priors on the individual galactic components, we derive conservative estimates for the astrophysical fac…
Dark Energy Survey year 1 results: Constraints on extended cosmological models from galaxy clustering and weak lensing
Bechtol, K.; Smith, M.; Nichol, R. C. +112 more
We present constraints on extensions of the minimal cosmological models dominated by dark matter and dark energy, Λ CDM and w CDM , by using a combined analysis of galaxy clustering and weak gravitational lensing from the first-year data of the Dark Energy Survey (DES Y1) in combination with external data. We consider four extensions of the minima…
Primordial black holes from inflation with nonminimal derivative coupling
Wu, Puxun; Yu, Hongwei; Fu, Chengjie
We propose a novel enhancement mechanism of the curvature perturbations in the nonminimal derivative coupling inflation model with a coupling parameter related to the inflaton field. By considering a special form of the coupling parameter as a function of the inflaton, a period of ultra-slow-roll inflation can be realized due to the gravitationall…
Refinement of the standard halo model for dark matter searches in light of the Gaia Sausage
Evans, N. Wyn; McCabe, Christopher; O'Hare, Ciaran A. J.
Predicting signals in experiments to directly detect dark matter (DM) requires a form for the local DM velocity distribution. Hitherto, the standard halo model (SHM), in which velocities are isotropic and follow a truncated Gaussian law, has performed this job. New data, however, suggest that a substantial fraction of our stellar halo lies in a st…
New constraints on sterile neutrino dark matter from NuSTAR M31 observations
Wik, Daniel R.; Krivonos, Roman; Beacom, John F. +4 more
We use a combined 1.2 Ms of NuSTAR observations of M31 to search for x-ray lines from sterile neutrino dark matter decay. For the first time in a NuSTAR analysis, we consistently take into account the signal contribution from both the focused and unfocused fields of view. We also reduce the modeling systematic uncertainty by performing spectral fi…
Constraints on a Bianchi type I spacetime extension of the standard Λ CDM model
Kumar, Suresh; Akarsu, Özgür; Sharma, Shivani +1 more
We consider the simplest anisotropic generalization, as a correction, to the standard Λ CDM model, by replacing the spatially flat Robertson-Walker metric by the Bianchi type-I metric, which brings in a new term Ωσ 0a-6 (mimicking the stiff fluid) in the average expansion rate H (a ) of the Universe. From Hubble and Pantheon …
Cosmological constraints on neutrino self-interactions with a light mediator
Lattanzi, Massimiliano; Natoli, Paolo; Forastieri, Francesco
If active neutrinos undergo nonstandard ("secret") interactions (NS ν Is ), the cosmological evolution of the neutrino fluid might be altered, leaving an imprint in cosmological observables. We use the latest publicly available CMB data from Planck to constrain NS ν Is inducing ν -ν scattering, under the assumption that the mediator ϕ of the secre…
Cosmological constraints on post-Newtonian parameters in effectively massless scalar-tensor theories of gravity
Rossi, Massimo; Ballardini, Mario; Braglia, Matteo +4 more
We study the cosmological constraints on the variation of Newton's constant and on post-Newtonian parameters for simple models of the scalar-tensor theory of gravity beyond the extended Jordan-Brans-Dicke theory. We restrict ourselves to an effectively massless scalar field with a potential V ∝F2, where F (σ )=Npl2…