Related papers: Variations on Birkhoff's theorem
Cosmology yields the most restrictive limits on neutrino masses and conversely, massive neutrinos would contribute to the cosmic dark-matter density and would play an important role for the formation of structure in the universe. Neutrino…
The role of global topology in the dynamics of the Universe is poorly understood. Along with observational programmes for determining the topology of the Universe, some small theoretical steps have recently been made. Heuristic…
It has been suggested that the Dark Energy Coincidence Problem could be interpreted as a possible link between the cosmological constant and a massive graviton. We show that by using that link and models for the graviton mass a dark energy…
A resultant gravitational force due to the current estimates of the virial mass of the Milky Way galaxy, dominated by dark matter, is estimated near the Sun and is described in two different analytical models yielding consistent results.…
The effect of bulk viscisity on the evolution of the homogeneous and isotropic cosmological models is considered. Solutions are found, with a barotropic equation of state, and a viscosity coefficient that is proportional to a power of the…
We investigate the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Considering that the dark matter obeys the collisional Boltzmann equation, we can obtain analytical solutions of the…
It is suggested that the recently observed size evolution of very massive compact galaxies in the early universe can be explained, if dark matter is in Bose Einstein condensate. In this model the size of the dark matter halos and galaxies…
Weinberg relation can be explained by Newton laws. It can also be transformed into a relation between a gravitational cross section area, associated to a gravitational mass m, and the product of two gravitational radii corresponding to the…
In this pedestrian approach I give my personal point of view on the various problems posed by dark matter in the universe. After a brief historical overview I discuss the various solutions stemming from high energy particle physics, and the…
It has been known for some time that the usual inference drawn from the observed near-flatness of the large-scale Universe - namely the existence of a cosmological "flatness problem", which is then taken as a partial, but key motivation for…
A general formulation of the basic conflict of the information problem is given, encapsulated in a "black hole theorem." This is framed in a more general context than the usual one of quantum field theory on a background, and is based on…
We present a comprehensive and technically rigorous analysis of the status of Birkhoff's theorem in Jackiw-Teitelboim (JT) gravity, a paradigmatic two-dimensional model for studying semiclassical gravitational dynamics. While Birkhoff's…
We investigate BBN in scalar-tensor theories of gravity with arbitrary matter couplings and self-interaction potentials. We first consider the case of a massless dilaton with a quadratic coupling to matter. We perform a full numerical…
The simplest gauge gravitation theory in Riemann-Cartan space-time leading to the solution of the problem of cosmological singularity and dark energy problem is investigated with purpose to solve the dark matter problem. It is shown that…
The success of the Lambda-CDM model on large scales does not extend down to galaxy scales. We list a dozen problems of the dark matter hypothesis, some of which arise in specific models for the formation of structure in the universe, while…
We clarify the conditions for Birkhoff's theorem, that is, time-independence in general relativity. We work primarily at the linearized level where guidance from electrodynamics is particularly useful. As a bonus, we also derive the…
The nature of the gravitational interaction between ordinary and dark matter is still open. Any deviation from universality or the Newtonian law also modifies the standard assumption of collisionless dark matter. On the other hand,…
Interactions within the cosmic medium modify its equation of state. We discuss implications of interacting dark energy models both for the spatially homogenous background and for the perturbation dynamics.
We review some of the well-known features of quantum cosmology, such as the factor ordering problem, the wave function and the density matrix, for a dark energy dominated universe, where analytical solutions can be obtained. For the…
The accelerating expansion of the universe presents an exciting, fundamental challenge to the standard models of particle physics and cosmology. I highlight some of the outstanding challenges in both developing theoretical models and…