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We study, for the first time, how shear and angular momentum modify typical parameters of the spherical collapse model, in dark energy dominated universes. In particular, we study the linear density threshold for collapse…

Cosmology and Nongalactic Astrophysics · Physics 2014-02-04 A. Del Popolo , F. Pace , J. A. S. Lima

Cold dark matter simulations appear to disagree with the observations on small distance scales. Here we consider a modified description of CDM particles which is implied by a new fundamental theory: In this picture, the dark matter is…

Astrophysics · Physics 2007-05-23 Antonio R. Mondragon , Roland E. Allen

The quantum model of the homogeneous, isotropic, and spatially closed universe predicts an existence of two types of collective quantum states in the universe. The states of one type characterize a gravitational field, the others describe a…

Astrophysics · Physics 2007-05-23 V. E. Kuzmichev , V. V. Kuzmichev

We investigate the impact of dark matter on neutron star properties using the relativistic mean-field theory. By incorporating the dark matter model, we explore how dark matter parameters, specifically dark matter mass and Fermi momentum,…

High Energy Astrophysical Phenomena · Physics 2024-08-29 Ankit Kumar , Hajime Sotani

A widely employed method for estimating the mass of stellar systems with apparent spherical symmetry is dynamical modelling using the spherically symmetric Jeans equation. Unfortunately this approach suffers from a degeneracy between the…

Astrophysics of Galaxies · Physics 2015-06-19 Foivos I. Diakogiannis , Geraint F. Lewis , Rodrigo A. Ibata

We present updated constraints on an interacting dark energy - dark matter model with pure momentum transfer, where dark energy is in the form of a quintessence scalar field with an exponential potential. We run a suite of MCMC analyses…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-09 Alkistis Pourtsidou

The annihilation of dark matter particles in the halo of galaxies may end up into gamma rays, which travel almost unperturbed till to their detection at Earth. This annihilation signal can exhibit an anisotropic behavior quantified by the…

High Energy Astrophysical Phenomena · Physics 2014-06-19 F. Calore , V. De Romeri , M. Di Mauro , F. Donato , J. Herpich , A. V. Maccio' , L. Maccione

(Abridged) Present cosmological constraints and the absence of a direct detection and identification of any dark matter particle candidate leave room to the possibility that the dark sector of the Universe be actually more complex than it…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Marco Baldi

We present a simple and efficient anisotropic generalization of the semi-isotropic (two-integral) axisymmetric Jeans formalism which is used to model the stellar kinematics of galaxies. The following is assumed: (i) a constant mass-to-light…

Astrophysics · Physics 2008-12-06 Michele Cappellari

Models with dark energy decaying into dark matter have been proposed to solve the coincidence problem in cosmology. We study the effect of such coupling in the matter power spectrum. Due to the interaction, the growth of matter density…

Astrophysics · Physics 2008-11-26 G. Olivares , F. Atrio-Barandela , D. Pavon

Dark energy is frequently modelled as an additional dynamical scalar field component in the Universe, referred to as "quintessence", which drives the late-time acceleration. Furthermore, the quintessence field may be coupled to dark matter…

Cosmology and Nongalactic Astrophysics · Physics 2023-09-12 Daniela Palma , Graeme N. Candlish

We show that a metastable dark matter candidate arises naturally from the conformal transformation between the Einstein metric, where gravitons are normalised states, and the Jordan metric dictating the coupling between gravity and matter.…

High Energy Physics - Phenomenology · Physics 2021-06-23 Philippe Brax , Kunio Kaneta , Yann Mambrini , Mathias Pierre

As a deformed matter bounce scenario with a dark energy component we propose a deformed one with running vacuum model (RVM) in which the dark energy density is written as a power series of $H^2$ and $\dot H$ with a constant equation of…

General Relativity and Quantum Cosmology · Physics 2018-04-18 M. Arab , A. Khodam-Mohammadi

Axions as dark matter is an increasingly important subject in astrophysics and cosmology. Experimental and observational searches are mounting across the mass spectrum of axion-like particles, many of which require detailed knowledge of…

Cosmology and Nongalactic Astrophysics · Physics 2019-03-13 Erik W. Lentz , Thomas R. Quinn , Leslie J Rosenberg

Modified Dark Matter (MDM) is a phenomenological model of dark matter, inspired by gravitational thermodynamics, that naturally accounts for the universal acceleration constant observed in galactic rotation curve data; a critical…

Cosmology and Nongalactic Astrophysics · Physics 2018-01-03 Douglas Edmonds , Duncan Farrah , Djordje Minic , Y. Jack Ng , Tatsu Takeuchi

Anisotropies in the electromagnetic emission produced by dark matter annihilation or decay in the extragalactic sky are a recent tool in the quest for a particle dark matter evidence. We review the formalism to compute the two-point angular…

Cosmology and Nongalactic Astrophysics · Physics 2014-01-28 Nicolao Fornengo , Marco Regis

We consider a cosmological model with an interaction between dark matter and dark energy which leaves the background cosmology unaffected and only affects the evolution of the perturbations. This is achieved by introducing a coupling given…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-21 Mahnaz Asghari , Jose Beltran Jimenez , Shahram Khosravi , David F. Mota

Assuming the validity of the general relativistic description of gravitation on astrophysical and cosmological length scales, we analytically infer that the Friedmann-Robertson-Walker cosmology with Einsteinian cosmological constant, and a…

Astrophysics · Physics 2008-11-26 D. V. Ahluwalia-Khalilova

In a recent article, Kleidis and Spyrou (2015) proposed that both dark matter (DM) and dark energy (DE) can be treated as a single component, if accommodated in the context of a polytropic DM fluid with thermodynamical content. Depending…

Cosmology and Nongalactic Astrophysics · Physics 2017-10-25 Kostas Kleidis , Nikolaos K. Spyrou

The main purpose of this paper is to advance a unified theory of dark matter, dark energy, and inflation first formulated in 2008. Our minimal affine extension of the GR has geodesics coinciding with the pseudo Riemannian ones, up to…

General Relativity and Quantum Cosmology · Physics 2019-07-02 Alexandre T. Filippov