相关论文: A Toy Model for the Dynamical Discrepancies on Gal…

High resolution cosmological N-body simulations of four galaxy-scale dark matter halos are compared to corresponding N-body/hydrodynamical simulations containing dark matter, stars and gas. The simulations without baryons share features…

Low-scale supersymmetry breaking in string motivated theories implies the presence of O(100) TeV scale moduli, which generically lead to a significant modification of the history of the universe prior to Big Bang Nucleosynthesis. Such an…

A possible solution to the dark energy problem is that Einstein's theory of general relativity is modified. A suite of models have been proposed that, in general, are unable to predict the correct amount of large scale structure in the…

Most rotationally-supported galaxies strictly follow the Baryonic Tully-Fisher Relation (BFTR) linking circular velocity with baryon content. This firmly established empirical relationship is currently thought to have origins in either…

We compare six models (including the baryonic model, two dark matter models, two modified Newtonian dynamics models and one modified gravity model) in accounting for the galaxy rotation curves. For the dark matter models, we assume NFW…

Modelling gravity is a fundamental problem that must be tackled in N-body simulations of stellar systems, and satisfactory solutions require a deep understanding of the dynamical effects of softening. In a previous paper (Romeo 1997), we…

We use cosmological hydrodynamical simulations of the APOSTLE project along with high-quality rotation curve observations to examine the fraction of baryons in {\Lambda}CDM haloes that collect into galaxies. This 'galaxy formation…

After summarizing the respective merits of the Cold Dark Matter (CDM) and Modified Newtonian Dynamics (MOND) paradigms in various stellar systems, we investigate the possibility that a non-standard interaction between baryonic and dark…

Dark energy and dark matter constitute 95% of the observable Universe. Yet the physical nature of these two phenomena remains a mystery. Einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive…

Purely baryonic dark matter dominated models like MOND based on modification of Newtonian gravity have been successfully in reproducing some dynamical properties of galaxies. More recently, a relativistic formulation of MOND proposed by…

In this paper, I study spherically symmetric solutions in a simple class of geometric sigma models of the Universe. This class of models is a subclass of the wider class of scalar-tensor theories of gravity. The purpose of this work is to…

We discuss the various resolutions which have been suggested in the literature for the way that the equivalence theorem can be satisfied in theories with global anomalies. We provide a model-independent proof for the resolution originally…

The hypothesis of the scale invariance of the macroscopic empty space, which intervenes through the cosmological constant, has led to new cosmological models. They show an accelerated cosmic expansion and satisfy several major cosmological…

Square-torsion gravity is applied to the long standing dark matter problem. In this context the theory reduces to General Relativity complemented by a dark stress-energy tensor due to the torsion of spacetime and is studied under the…

In a scalar-vector-gravity theory with the vector sector described by nonlinear electrodynamics, the field equations are integrated using the well-known gravitational decoupling method. The resulting spacetime corresponds to a spherically…

We provide a holographic dual description of Milgrom's scaling associated with galactic rotation curves. Our argument is based on the recent entropic reinterpretation of Newton's laws of motion. We propose a duality between cold dark matter…

Recently, the Cubic Galileon Gravity (CGG) model has been suggested as an alternative gravity theory to General Relativity. The model consists of an extra field potential term which can serve as the `fifth-force'. In this article, we…

It is already known that a simple nonlocal de Sitter gravity model, which we denote as $\sqrt{dS}$ gravity, contains an exact vacuum cosmological solution which mimics dark energy and dark matter and is in very good agreement with the…

This article shows that the compactified Milne universe geometry, a toy model for the big crunch/big bang transition, can be realized in hyperbolic metamaterials, a new class of nanoengineered systems which have recently found its way as an…

Observations are studied in toy-models constituting exact cosmological solutions to the Einstein equation which are statistically homogeneous but locally inhomogeneous, without an a priori introduced FLRW background and with "structures"…