Related papers: Why The Cosmological Constant is a Boundary Condit…
In this paper, motivated from the fact that a de Sitter cosmological boundary corresponds to a positive cosmological constant, we consider time variable cosmological constants, dubbed {\it horizon cosmological constants}. The horizon…
We show how the scalar field, a candidate of quintessence, in a proposed model of the scalar-tensor theories of gravity provides a way to understand a small but nonzero cosmological constant as indicated by recent observations. A particular…
The evolution of the wave function in quantum mechanics is deterministic like that of classical waves. Only when we bring in observers the fundamentally different quantum reality emerges. Similarly the introduction of observers changes the…
An speculative solution for the cosmological constant problem is proposed. It is argued that while the true quantum vacuum energy density is of the order of $M_P^4$, the observed classical vacuum energy density may be much smaller due to…
The nature of the cosmological constant is a mystery. We don't understand its quantum origin but we associate it with the actual acceleration of the universe because it is the simplest description we had until recently of the present…
The origins of the cosmological constant are discussed from the perspective of the imaginary-time field theory. The concept of the thermal time, which is related to the Tolman-Ehrehfest relation, and the conformal invariance of the actions…
The work shows that the associated Einstein like gravity for the Klein-Gordon field shows the spontaneous emergence of the cosmological pressure tensor density (CPTD) that in the classical limit leads to the cosmological constant (CC). Even…
In contrast to the phenomenon of nullification of the cosmological constant in the equilibrium vacuum, which is the general property of any quantum vacuum, there are many options in modifying the Einstein equation to allow the cosmological…
In the framework of a model of minimal of dilatonic gravity (MDG) with cosmological potential we consider: the relations of MDG with nonlinear gravity and string theory; natural cosmological units, defined by cosmological constant; the…
We regard the background of space-time as a physical system composed of discrete volume elements at the Planck scale and get the internal energy of space-time by Debye model. A temperature-dependent minimum energy limit of the particles is…
A finite quantum gravity theory is used to resolve the cosmological constant problem. A fundamental quantum gravity scale, \Lambda_G \leq 10^{-3} eV, is introduced above which the quantum corrections to the vacuum energy density coupled to…
Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Lambda; nowadays the concept is termed dark energy or quintessence. Physics also suggests the dark energy…
We trace the origin of the cosmological constant problem to the assumption that Newton's constant $G$ sets the scale for cosmology. And then we show that once this assumption is relaxed, the very same cosmic acceleration which has served to…
In the light of the proposal of hep-th/0207195, we discuss in detail the issue of the cosmological constant, explaining how can string theory naturally predict the value which is experimentally observed, without low-energy supersymmetry.
Under the hypothesis that the cosmological constant vanishes in the true ground state with lowest possible energy density, we argue that the observed small but finite vacuum-like energy density can be explained if we consider a theory with…
Among the various possibilities to probe the theory behind the recent accelerated expansion of the universe, the energy conditions (ECs) are of particular interest, since it is possible to confront and constrain the many models, including…
Most of the calculations done to obtain the value of the cosmological constant use methods of quantum gravity, a theory that has not been established as yet, and a variety of results are usually obtained. The numerical value of the…
Observational data in cosmology indicate a small, positive, and nonvanishing cosmological constant that dominates the energy budget of the present universe. The origin of the cosmological constant from a quantum perspective remains…
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…
The cosmological constant problem can be understood as the failure of the decoupling principle behind effective field theory, so that some quantities in the low-energy theory are extremely sensitive to the high-energy properties. While this…