I review the problem of dark energy focussing on cosmological constant as the candidate
and discuss what it tells us regarding the nature of gravity. Section 1 briefly overviews the …

We compare the different approaches presently available in literature to probe the vacuum
structure of quantum fields in classical electromagnetic and gravitational backgrounds. We …

Nearly seventy per cent of the energy density in the universe is unclustered and exerts
negative pressure. This conclusion--now supported by numerous observations--poses the …

Recent cosmological observations suggest that nearly seventy per cent of the energy
density in the universe is unclustered and has negative pressure. Several conceptual issues …

The energy density associated with the Planck length is ρ UV∝ L− 4 P while the energy
density associated with the Hubble length is ρ IR∝ L− 4 H, where LH= 1/H. The observed …

Unruh DeWitt (UDW) detectors are important constructs in studying the dynamics of quantum
fields in any geometric background. Curvature also plays an important role in setting up the …

The cosmological constant is the most economical candidate for dark energy. No other
approach really alleviates the difficulties faced by the cosmological constant because, in all …

Recent research has indicated that negative energy fluxes due to quantum coherence
effects obey uncertainty-principle-type inequalities of the form| Δ E| Δ τ≲ 1. Here| Δ E| is the …

Abstract We solve the Klein-Gordon equation for a scalar field, in the background geometry
of a dust cloud collapsing to form a black hole in the (1+ 1) spacetime. This has been …

In this paper we propose an alternative method for the computation of classical density
perturbations from a quantum field in an inflationary scenario. We compute the power …