Related papers: The CMB in a Causal Set Universe
Using the recently obtained holographic cosmic duality, we reached a reasonable quantitative agreement between predictions of the Cosmic Microwave Background Radiation at small l and the WMAP observations, showing the power of the…
This brief article sums up the possible imprints of loop quantum gravity effects on the cosmological microwave background. We focus on semi-classical terms and show that "Big Bounce" corrections, together with the "pre Big Bounce" state,…
This thesis investigates late-time cosmic acceleration using modified gravity theories with a focus on $f(Q)$ gravity, as an alternative to the $\Lambda$CDM model. The standard cosmological model attributes the acceleration to a…
The acceleration of the universe can be explained either through dark energy or through the modification of gravity on large scales. In this paper we investigate modified gravity models and compare their observable predictions with dark…
Taking up four model universes we study the behaviour and contribution of dark energy to the accelerated expansion of the universe, in the modified scale covariant theory of gravitation. Here, it is seen that though this modified theory may…
We consider a modified gravity theory, f(R)=R-a/R^n+bR^m, in the metric formulation, which has been suggested to produce late time acceleration in the Universe, whilst satisfying local fifth-force constraints. We investigate the parameter…
Over the last decade, cosmological observations have attained a level of precision which allows for very detailed comparison with theoretical predictions. We are beginning to learn the answers to some fundamental questions, using…
We apply the causal interpretation of quantum mechanics to homogeneous quantum cosmology and show that the quantum theory is independent of any time-gauge choice and there is no issue of time. We exemplify this result by studying a…
We use here a family of scaling transformations, that scale key rates in the evolution equations, to analytically understand constraints on light relics from cosmic microwave background (CMB) maps, given cosmological models of varying…
In this paper, we investigate a scenario in which late time cosmic acceleration might arise due to coupling between dark matter and baryonic matter without resorting to dark energy or large scale modification of gravity associated with…
The Cosmic Microwave Background (CMB), which permeates the entire Universe, is the radiation left over from just 380,000 years after the Big Bang. On very large scales, the CMB radiation field is smooth and isotropic, but the existence of…
We derive causality constraints on the simplest scalar-tensor theories in which black holes differ from what General Relativity predicts, a scalar coupled to the Gauss-Bonnet or the Chern-Simons terms. Demanding that time advances are…
A modified gravity involving a critical acceleration, as empirically established at galactic scales and successfully tested by data on supernovae of type Ia, can fit the measured multipole spectrum of anisotropy in the cosmic microwave…
Quantum field theory (QFT) in classical spacetime has revealed interesting and puzzling aspects about gravitational systems, in particular black hole thermodynamics and its information processing. Although quantum gravitational effects may…
Perturbations from inflation evolve into large scale structure of the late universe, and encode abundant cosmic structure formation physics. We allow freedom in the primordial power spectrum, rather than assuming a power law scale…
We have investigated the cosmic microwave background (CMB) anisotropy in closed multiply connected universes (flat and hyperbolic) with low matter density. We show that the COBE constraints on these low matter density models with…
General Relativity traces the evolution of our Universe back to a Big Bang singularity. To probe physics before the singularity -- if indeed there is a ``before'' -- we must turn to quantum gravity. The Causal Set approach to quantum…
Our Universe has multiple examples of unexplained gravitational losses in black holes and neutron stars. As all of the space is squeezed out, nucleons are not easily compressible further. Gravitational loss will allow galactic black holes…
In these lectures we review the constraints on particle physics models arising from cosmic defects. This includes constraints on theories where stable cosmic string loops, or vortons result. These can arise in supersymmetric theories. We…
One of the most powerful tools to probe the existence of cosmic defects in the early universe is through the Cosmic Microwave Background (CMB) radiation. It is well known that computations with causal sources are more involved than the…