Related papers: Issues on the cosmological constant
We use data from observational cosmology to put constraints on higher-dimensional extensions of general relativity in which the effective four-dimensional dark-energy density (or cosmological "constant") decays with time. In particular we…
If the observed dark energy is a cosmological constant, the canonical state of the universe is de Sitter spacetime. In such a spacetime, quantum fluctuations that violate the null energy condition will create islands of matter that, if…
It has recently been proposed by Mersini et al. 01, Bastero-Gil and Mersini 02 that the dark energy could be attributed to the cosmological properties of a scalar field with a non-standard dispersion relation that decreases exponentially at…
There is now strong evidence that the main contribution to the cosmic energy density is not due to matter, but to another component with negative pressure. Its nature is still unknown: it could be the vacuum energy, manifesting itself as a…
The concordance model of cosmology suffers from the major theoretical problems surrounding the observed value and recent emergence of a cosmological constant. In this paper we present a novel approach, which explains more naturally its…
Many candidate models for dark energy are based on the existence of a classical scalar field. In the context of Quantum Field Theory (QFT), we briefly discus the condensation of such a field from a light quantum scalar field produced by…
In this thesis the cosmological constant is investigated from two points of view. First, we study the influence of a time-dependent cosmological constant on the late-time expansion of the universe. Thereby, we consider several combinations…
We show that quantum decoherence, in the context of observational cosmology, can be connected to the cosmic dark energy. The decoherence signature could be characterized by the existence of quantum entanglement between cosmological eras. As…
I consider a scenario proposed by Fardon, Nelson and Weiner where dark energy and neutrinos are connected. As a result, neutrino masses are not constant but depend on the neutrino number density. By examining the full equation of state for…
This paper continues the development of a discrete space-time concept that is recently used in the explanation of the cosmological constant. Instead of order estimation, a more theoretical treatment of the theory is introduced. Based on the…
We explore local consequences of a non-zero cosmological constant on astrophysical structures. We find that the effects are not only sensitive to the density of the configurations but also to the geometry. For non-homogeneous…
Recent cosmological observations strongly suggest that the universe is dominated by an unknown form of energy with negative pressure. Why is this dark energy density of order the critical density today? We propose that the dark energy has…
We review the current status of cosmological parameters, dark energy and large-scale structure, from a theoretical and observational perspective. We first present the basic cosmological parameters and discuss how they are measured with…
The introduction of an interaction for dark energy to the standard cosmology offers a potential solution to the cosmic coincidence problem. We examine the conditions on the dark energy density that must be satisfied for this scenario to be…
The cosmological constant problem is a fundamental issue that has puzzled researchers in the fields of theoretical physics and cosmology for a long time. It arises from the discrepancy between the observed value of the cosmological constant…
We consider a possibility that the formally infinite vacuum energy of the quantized matter fields could be stored into Planck-size quantum black holes acting as the fundamental constituents of space and time. Using the recently proposed…
We present a prototype model that resolves the cosmological constant problem using matter alone, i.e., without modifying gravity. Its generic cosmological solutions adjust an arbitrarily large, negative dark energy to a positive value…
These lectures have been given to particle physicists, mostly experimentalists and very briefly and at a pedestrian level review the problems of dark matter. The content of the lectures is the following: 1. Introduction. 2. Cosmological…
We consider the fate of the observable universe in the light of the discovery of a dark energy component to the cosmic energy budget. We extend results for a cosmological constant to a general dark energy component and examine the…
This review on dark energy is intended for a wider audience, beginners as well as experts. It contains important notes on various aspects of dark energy and its alternatives. The section on Newtonian cosmology followed by heuristic…