Related papers: Holography and Variable Cosmological Constant
We consider a static spherically symmetric charged anisotropic fluid source of finite physical radius (\sim 10^{-16} cm) by introducing a scalar variable \Lambda dependent on the radial coordinate r under general relativity. From the…
In this paper we consider the nature of the cosmological constant as due by quantum fluctuations. Quantum fluctuations are generated at Planckian scales by noncommutative effects and watered down at larger scales up to a decoherence scale…
Light scalar fields very naturally appear in modern cosmological models, affecting such parameters of Standard Model as electromagnetic fine structure constant $\alpha$, dimensionless ratios of electron or quark mass to the QCD scale,…
Within the quantum mechanical treatment of the decay problem one finds that at late times $t$ the survival probability of an unstable state cannot have the form of an exponentially decreasing function of time $t$ but it has an inverse…
We argue that, when a theory of gravity and matter is endowed with (classical) conformal symmetry, the fine tuning required to obtain the cosmological constant at its observed value can be significantly reduced. Once tuned, the cosmological…
We study the quantum contributions to the classical cosmological constant in a quantum gravity theory for GR with matter on a piecewise linear spacetime corresponding to a triangulation of a smooth manifold. We use the effective action…
We propose several covariant models which may solve one of the problems in the cosmological constant. One of the model can be regarded as an extension of sequestering model. Other models could be regarded as extensions of the covariant…
We present a model that naturally tunes a large positive cosmological constant to a small cosmological constant. A slowly rolling scalar field decreases the cosmological constant to a small negative value, causing the universe to contract,…
It is believed that a primary principle of the theory of quantum gravity is the Holographic Principle according to which a physical system can be described only by degrees of freedom living on its boundary. The generalized covariant…
We explore the effects of a positive cosmological constant on astrophysical and cosmological configurations described by a polytropic equation of state. We derive the conditions for equilibrium and stability of such configurations and…
One of the most disturbing difficulties in thinking about the cosmological constant is that it is not stable under radiative corrections. The feedback mechanism proposed in [hep-th/0306108] is a dynamical way to protect a zero or small…
We discuss a spacetime having the topology of $S^{3}\times\mathbb{R}$ but with a different smoothness structure. The initial state of the cosmos in our model is identified with a wildly embedded 3-sphere (or a fractal space). In previous…
Motivated by the cosmological constant and the coincidence problems, we consider a cosmological model where the cosmological constant $\Lambda_0$ is replaced by a cosmological term $\Lambda(t)$ which is allowed to vary in time. More…
We discuss predictions for cosmology which result from the scaling solution of functional flow equations for a quantum field theory of gravity. A scaling solution is necessary to render quantum gravity renormalizable. Our scaling solution…
The idea that the cosmological term, Lambda, should be a time dependent quantity in cosmology is a most natural one. It is difficult to conceive an expanding universe with a strictly constant vacuum energy density, namely one that has…
The incorporation of a small cosmological constant within radiatively-broken scale-invariant models is discussed. We show that phenomenologically consistent scale-invariant models can be constructed which allow a small positive cosmological…
In this work, we compute the universe temperature for the cosmological horizon for the FLRW metric. For this purpose, we consider a scalar field on the cosmological horizon. This scalar field satisfies the Klein-Gordon equation in a curved…
The value of the cosmological constant arising from a crystalline model for vacuum cosmic space with lattice parameter of the order of the neutron radius [1] has been calculated. The model allows to solve, in an easy way, the problem of the…
We point out that for a large class of universes, holography implies that the most probable value of the cosmological constant is zero. In four spacetime dimensions, the probability distribution takes the Baum-Hawking form,…
We study the effects of a generalized uncertainty principle on the classical and quantum cosmology of a closed Friedmann Universe whose matter content is either a dust or a radiation fluid. More concretely, assuming the existence of a…