Related papers: Everpresent Lambda
In this talk we present a model of the universe in which dark energy is modelled explicitely with both a dynamical quintessence field and a cosmological constant. Our results confirm the possibility of a collapsing universe (for a given…
Entropy bounds render quantum corrections to the cosmological constant $\Lambda$ finite. Under certain assumptions, the natural value of $\Lambda$ is of order the observed dark energy density $\sim 10^{-10} {\rm eV}^4$, thereby resolving…
Dark energy is one of the mysteries of modern science. It is unlike any known form of matter or energy and has been detected so far only by its gravitational effect of repulsion. Owing to its effects being discernible only at very very…
We investigate two simplified non-singular cyclic models with a negative time-varying cosmological constant to represent the non-conventional mechanism of negative cosmological constant expected to address the late-time cosmic acceleration.…
The cosmological constant problem is the principal obstacle in the attempt to interpret dark energy as the quantum vacuum energy. We suggest that the obstacle can be removed, i.e. that the cosmological constant problem can be resolved by…
We show that the cosmological constant appears as a Lagrange multiplier if nature is described by a canonical noncommutative spacetime. It is thus an arbitrary parameter unrelated to the action and thus to vacuum fluctuations. The…
It is well-known that in unimodular gravity the cosmological constant is not sourced by a constant energy density, but rather appears as some sort of integration constant. In this work we try to flesh this out by studying in some detail a…
We show that the description of the space-time of general relativity as a diagonal four dimensional submanifold immersed in an eight dimensional hypercomplex manifold, in torsionless case, leads to a geometrical origin of the cosmological…
Recent observations suggest that a large fraction of the energy density of the universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a scalar field slowly evolving down a potential.…
We show that the causal set approach to creating an ever-present cosmological 'constant' in the expanding universe is strongly constrained by the isotropy of the microwave background. Fluctuations generated by stochastic lambda generation…
This is an essay sketching the line of thinking which has led the present author to propose the constituent or atomic model of gravitation more than a decade ago. It turns out that viewing the problem of gravitation as a quantum many body…
We propose that the solution to the cosmological vacuum energy puzzle may come from the infrared sector of the effective theory of gravity, where the impact of the trace anomaly is of upmost relevance. We proceed by introducing two…
The cosmological constant problem is explained by a theory based on the discrete space-time hypothesis. The calculated cosmological constant value is of the order of 10^-52[m]^-2 or equivalent to about 0.7 of the critical mass density. It…
We investigate the possibility of replacing the cosmological constant with gradual condensation of a scalar field produced during the decay of a superheavy dark matter. The advantage of this class of models to the ordinary quintessence is…
We suggest an alternative framework for interpreting the current state of the visible universe. Our approach is based on a dynamical ``Cosmological Constant'' and the starting point is that a decaying vacuum produces matter. As we point…
The early cosmic inflation, when taken along with the recent observations that the universe is currently dominated by a low density vacuum energy, leads to at least two potential problems which modern cosmology must address. First, there is…
The fluctuations of the vacuum energy are treated as a non-equilibrium process and a stochastic model for the cosmological constant is presented, which yields a natural explanation for the smallness or zero value of the constant in the…
The cosmological constant $\Lambda$ is a measure of the energy density of the vacuum. Therefore properties of the energy of the system in the metastable vacuum state reflect properties of $\Lambda = \Lambda(t)$. We analyze properties of the…
The discovery that the expansion of the universe is accelerating in time is a major discovery which still awaits adequate explanation. It is generally agreed that this implies a cosmic repulsion as a result of the existence of a…
A six parameter cosmological model, involving a vacuum energy density that is extremely tiny compared to fundamental particle physics scales, describes a large body of increasingly accurate astronomical data. In a first part of this brief…