相关论文: A Note on Acceleration from Product Space Compacti…
A model of inflation is proposed in which compact extra dimensions allow a graceful exit without recourse to flat potentials or super-Planckian field values. Though bubbles of true vacuum are too sparse to uniformly reheat the Universe by…
We extend to multidimensional cosmology Vilenkin's prescription of tunnelling from nothing for the quantum origin of the observable Universe. Our model consists of a $D+4$-dimensional spacetime of topology ${\cal R}\times {\cal S}^3…
Cosmological inflation is discussed in the realm of Einstein-Cartan-Brans-Dicke (ECBD) gravity by constructing an effective inflaton potential and computing the number of e-folds.It is shown that spin-torsion density contributes to a…
The effective equation of state of normal matter is changed in theories where the size of the compact space depends upon the local energy density. In particular we show how the dilution of a fluid due to the expansion of the universe can be…
We investigate cosmological solutions of eleven dimensional supergravity compactified on a squashed seven manifold. The effective action for the four dimensional theory contains scalar fields describing the size and squashing of the…
We show how to derive several families of accelerating universe solutions to an Einstein-Aether gravity theory. These solutions provide possible descriptions of inflationary behaviour in the early universe and late-time cosmological…
We consider the cosmological role of the scalar fields generated by the compactification of 11-dimensional Einstein gravity on a 7D elliptic twisted torus, which has the attractive features of giving rise to a positive semi-definite…
We study the possibility that the vacuum energy density of scalar and internal-space gauge fields arising from the process of dimensional reduction of higher dimensional gravity theories plays the role of quintessence. We show that, for the…
We consider vacuum quantum effects in the Early Universe, which may lead to inflation. The inflation is a direct consequence of the supposition that, at high energies, all the particles can be described by the weakly interacting, massless,…
The trace-free version of the Einstein Gravitational equations, essentially equivalent to unimodular gravity, can solve the troubling issue of the huge discrepancy between quantum field theory estimates of the vacuum energy density and the…
The lore paradigm for solving so-called horizon and flatness problems in cosmology is the primordial inflation. Plethora of inflationary models have been built in last decades and first experimental probes seem to appear in favor of the…
We investigate the dynamics of the recently proposed model of assisted inflation. In this model an arbitrary number of scalar fields with exponential potentials evolve towards an inflationary scaling solution, even if each of the individual…
We study multidimensional gravitational models with scalar curvature nonlinearity of the type 1/R and with form-fields (fluxes) as a matter source. It is assumed that the higher dimensional space-time undergoes Freund-Rubin-like spontaneous…
We study cosmological inflation within a recently proposed framework of perturbative moduli stabilisation in type IIB/F theory compactifications on Calabi-Yau threefolds. The stabilisation mechanism utilises three stacks of magnetised…
Inflation is often described through the dynamics of a scalar field, slow-rolling in a suitable potential. Ultimately, this inflaton must be identified as the expectation value of a quantum field, evolving in a quantum effective potential.…
We consider how accelerated expansion, whether due to inflation or dark energy, imposes strong constraints on fundamental theories obtained by compactification from higher dimensions. For theories that obey the null energy condition (NEC),…
We show that cosmic acceleration can arise due to very tiny corrections to the usual gravitational action of General Relativity of the form $R^n$, with $n<0$. This eliminates the need for dark energy, though it does not address the…
By using the formulation of the reconstruction, we explicitly construct models of $k$-essence, which unify the inflation in the early universe and the late accelerating expansion of the present universe by a single scalar field. Due to the…
New exact inflationary solutions are presented in the scalar field theory, minimally coupled to gravity, with a potential term. No use is made of the slow rollover approximation. The scale factors are completely nonsingular and the…
Within the framework of the scalar-tensor theory we consider a hill-climbing inflation, in which the effective Planck mass increases in time. We obtain the Einstein frame potential with infinitely long and flat plateau as we approach…