Filters








2,529 Hits in 10.4 sec

Impact of Collisional Matter on the Late-Time Dynamics of f(R,T) Gravity

M. Zubair, Muhammad Zeeshan, Syed Hasan, V. Oikonomou
2018 Symmetry  
Particularly, for a flat Friedmann–Lema i ^ tre–Robertson–Walker Universe, we study two non-minimally coupled f ( R , T ) gravity models and we focus our study on the late-time dynamical evolution of the  ...  We study the cosmic evolution of non-minimally coupled f ( R , T ) gravity in the presence of matter fluids consisting of collisional self-interacting dark matter and radiation.  ...  Conflicts of Interest: The authors declare no conflict of interest.  ... 
doi:10.3390/sym10100463 fatcat:4aopvetbn5eyfm3iiruhl7k23i

GRAVITY: getting to the event horizon of Sgr A* [article]

F. Eisenhauer, G. Perrin, W. Brandner, C. Straubmeier, A. Richichi, S. Gillessen, J.P. Berger, S. Hippler, A. Eckart, M. Schoeller, S. Rabien, F. Cassaing (+34 others)
2008 arXiv   pre-print
GRAVITY is specifically designed to observe highly relativistic motions of matter close to the event horizon of Sgr A*, the massive black hole at center of the Milky Way.  ...  We present the second-generation VLTI instrument GRAVITY, which currently is in the preliminary design phase.  ...  Currently, the partners work on the preliminary design and at the same time contracting with ESO is underway. Preliminary design review is foreseen for mid 2009.  ... 
arXiv:0808.0063v1 fatcat:mufrft3buvhvtfgyeuog6zefce

Modified gravity theories on a nutshell: Inflation, bounce and late-time evolution

S. Nojiri, S.D. Odintsov, V.K. Oikonomou
2017 Physics reports  
Particularly, we present the formalism of standard modified gravity theory representatives, like F(R), F(𝒢) and F(T) gravity theories, but also several alternative theoretical proposals which appeared  ...  We systematically review some standard issues and also the latest developments of modified gravity in cosmology, emphasizing on inflation, bouncing cosmology and late-time acceleration era.  ...  We also briefly present the formalism of inflationary dynamics in the context of F (T ) and one loop quantum gravity.  ... 
doi:10.1016/j.physrep.2017.06.001 fatcat:32fl4skhabc3fcgvvhw635jutu

Structure growth inf(R) theories of gravity with a dust equation of state

Kishore N Ananda, Sante Carloni, Peter K S Dunsby
2009 Classical and quantum gravity  
The evolution equations for scalar perturbation are derived using the covariant and gauge invariant approach and applied to two widely studied f(R) gravity models.  ...  The structure of the general fourth order perturbation equations and the analysis of scalar perturbations lead to the discovery of a characteristic signature of fourth order gravity in the matter power  ...  Acknowledgements: The authors wish to thank Dr J. Larena for useful discussion and suggestions. SC wish to thanks J Donkers for useful discussion and support during the development of this paper.  ... 
doi:10.1088/0264-9381/26/23/235018 fatcat:z5fxbifc4zdk7fwiu4fkdzk7hq

Tests of Gravity with Galaxy Clusters [chapter]

Matteo Cataneo, David Rapetti
2019 Modified Gravity  
Changes in the law of gravity have far-reaching implications for the formation and evolution of galaxy clusters, and appear as peculiar signatures in their mass-observable relations, structural properties  ...  , internal dynamics, and abundance.  ...  Acknowledgments We thank Adam Mantz for helpful comments on section 2 of this manuscript, and Yan Chuan Cai, Shadab Alam and Tilman Tröster for useful discussions that greatly improved the clarity of this  ... 
doi:10.1142/9789813274006_0006 fatcat:r4cdmbrxozaydlinxawkqwufna

Cosmology in Conformal Dilatonic Gravity [article]

Meir Shimon
2017 arXiv   pre-print
An interplay between the positive energy density associated with relativistic matter (and possibly with negative spatial curvature) and the negative energy associated with dynamical dilaton phase results  ...  The (logarithmic) time-derivative of the field modulus is degenerate with the Hubble function, and all cosmological epochs of the standard model are unchanged except at the very early universe.  ...  Acknowledgments The author is indebted to Yoel Rephaeli for numerous constructive, critical, and thought-provoking discussions which were invaluable for this work.  ... 
arXiv:1702.08472v3 fatcat:n2rnsedqh5bm5ox2gmjhmd2xea

Tests of Gravity with Galaxy Clusters

Matteo Cataneo, David Rapetti
2018 International Journal of Modern Physics D  
Changes in the law of gravity have far-reaching implications for the formation and evolution of galaxy clusters, and appear as peculiar signatures in their mass-observable relations, structural properties  ...  , internal dynamics, and abundance.  ...  GR in the context of f (R) gravity.  ... 
doi:10.1142/s0218271818480061 fatcat:gchwywumvrbu5b2qg6qwxi7vte

Emergent gravity: the BEC paradigm [article]

Gil Jannes
2009 arXiv   pre-print
We end with some considerations related to the possibility of constructing a serious toy model for Planck-scale gravity understood as an emergent phenomenon, based on the condensed matter analogy.  ...  We first review the basic ideas and formalism of analogue gravity in BECs, with particular emphasis on the possibility of simulating black holes.  ...  In order to linearise the eqs. (2.3), we write n(r, t) = n 0 (r) + g −1 n 1 (r, t) , (2.4.1) θ(r, t) = θ 0 (r) + θ 1 (r, t) , (2.4.2) where n 1 and θ 1 are small perturbations of the density and phase  ... 
arXiv:0907.2839v1 fatcat:jykkofbcnnauzhghjb6kzsx6pa

Impact disruption of gravity-dominated bodies: New simulation data and scaling

N. Movshovitz, F. Nimmo, D.G. Korycansky, E. Asphaug, J.M. Owen
2016 Icarus (New York, N.Y. 1962)  
For a target radius 100 ≤ R T ≤ 10 0 0km and a mass M T and a projectile radius r p ≤ R T and mass m p we find that a head-on impact with velocity magnitude v is catastrophic if the kinetic energy of the  ...  We find significant divergence between predictions where in general our results suggest a lower threshold for disruption except for highly oblique impacts with r p R T .  ...  Head-on impacts K * = 1 2 m p M T m p + M T v * 2 , (6) the kinetic energy of impact in the center of mass frame, against the variable U = 3 GM 2 T 5 R T + 3 Gm 2 p 5 r p + GM T m p R T + r p , (7) the  ... 
doi:10.1016/j.icarus.2016.04.018 fatcat:2ss7bmidxndw3o3ely4fftuej4

The Gravity of Classical Fields: And Its Effect on the Dynamics of Gravitational Systems [article]

Rodrigo Vicente
2021 arXiv   pre-print
In this thesis, we study the dynamical response of such confined bosonic structures when excited by external matter (stars, planets or black holes) in their vicinities.  ...  This thesis also deals with several classical field environmental effects on the motion (or, ultimately, the survival) of compact objects, like black holes.  ...  Late-time dynamical friction acting on a supersonic particle with finite size r min /L = 10 −2 (black dots).  ... 
arXiv:2110.07620v1 fatcat:qafenofylzhvznixgn2uxxypdi

Possible Resolution of the Hubble Tension with Weyl Invariant Gravity [article]

Meir Shimon
2022 arXiv   pre-print
Assuming vanishing spatial curvature, either one of the Planck 2018 (P18) or dark energy survey (DES) yr1 data sets subject to the SH0ES prior imply that γ^-1 is O(100) times larger than the Hubble scale  ...  Specifically, we consider a cosmological model in this framework that is dynamically identical to the standard model (SM) of cosmology.  ...  Acknowledgments The author thanks Yoel Rephaeli for numerous constructive and useful discussions. Anonymous referee of this work is also acknowledged for useful comments.  ... 
arXiv:2012.10879v3 fatcat:33b7p52b4zd4hcue7jgz23l3du

Exploring the liminality: properties of haloes and subhaloes in borderlinef(R) gravity

Difu Shi, Baojiu Li, Jiaxin Han, Liang Gao, Wojciech A. Hellwing
2015 Monthly notices of the Royal Astronomical Society  
We investigate the properties of dark matter haloes and subhaloes in an f(R) gravity model with |f_R0|=10^-6, using a very high-resolution N-body simulation.  ...  Contrary to the naive expectation, the halo formation time z_f is later for low-mass haloes in this model, a consequence of these haloes growing faster than their counterparts in ΛCDM at late times and  ...  P RO P E RT I E S O F DA R K M AT T E R H A L O E S In this section we will concentrate on the properties of dark matter haloes measured from our simulations.  ... 
doi:10.1093/mnras/stv1549 fatcat:b3ytswvtyjhx7lnou4l5626xmu

The tune of the universe: the role of plasma in tests of strong-field gravity [article]

Vitor Cardoso, Wen-di Guo, Caio F. B. Macedo, Paolo Pani
2020 arXiv   pre-print
The last two effects are relevant also in the case of massive fields that propagate in vacuum and can jeopardize tests of modified theories of gravity containing massive degrees of freedom.  ...  Some of these tests are based on electromagnetic probes or electrically charged bodies, and assume an empty universe.  ...  Since the change in the momentum of one electron over a timet is ∆P = Ft, we get the critical electric field for this to happen E rel = m e c/(e∆τ ) with ∆τ the mean collision time between electrons  ... 
arXiv:2009.07287v2 fatcat:55jxdvdckndxjkbzd2qjvsbakq

The isotropy of compact universes

John D Barrow, Hideo Kodama
2001 Classical and quantum gravity  
In the flat case we calculate the dynamical degrees of freedom of Bianchi-type I and VII_0 universes with compact 3-spaces and show that type VII_0 solutions are more general than type I solutions for  ...  We discuss the problem of the stability of the isotropy of the universe in the space of ever-expanding spatially homogeneous universes with a compact spatial topology.  ...  JDB acknowledges support from the Royal Society, the PPARC, and the University of New South Wales. HK was supported by the Grant-In-Aid for the Scientific Research (C2) of the Ministry of Educa-  ... 
doi:10.1088/0264-9381/18/9/310 fatcat:2mfwgbyjxraodeylcoy4y3x3da

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity [article]

Indranil Banik, Hongsheng Zhao
2022 arXiv   pre-print
This missing gravity problem may indicate a breakdown of GR at low accelerations, as postulated by Milgromian dynamics (MOND).  ...  understanding of gravity, Einstein's General theory of Relativity (GR).  ...  IB acknowledges support from a "Pathways to Research" fellowship from the University of Bonn.  ... 
arXiv:2110.06936v8 fatcat:nmfp7vjb3ndsng27tucaujfkim
« Previous Showing results 1 — 15 out of 2,529 results