We investigate cosmological evolution in models where the effective potential V (Ï†) may become negative for some values of the field Ï†. Phase portraits of such theories in space of variables (Ï†,â€¦ (More)

We consider the quasi-de Sitter geometry of the inflationary universe. We calculate the energy flux of the slowly rolling background scalar field through the quasi-de Sitter apparent horizon and setâ€¦ (More)

In this Letter, I point out that there is a curvature singularity problem appearing on the nonlinear level that generally plagues f(R) models that modify Einstein gravity in the infrared. It isâ€¦ (More)

A new class of non-Gaussian curvature fluctuations zeta(pr)(x) identical with deltaN(chi(i)) arises from the postinflation preheating behavior of a noninflaton field chi(i). Its billiardlike chaoticâ€¦ (More)

The intent of this letter is to point out that the accretion of a ghost condensate by black holes could be extremely efficient. We analyze steady-state spherically symmetric flows of the ghost fluidâ€¦ (More)

We study the dynamical equations for extra-dimensional dependence of a warp factor and a bulk scalar in 5d brane world scenarios with induced brane metric of constant curvature. These equations areâ€¦ (More)

We investigate scalar perturbations from inflation in braneworld cosmologies with extra dimensions. For this we calculate scalar metric fluctuations around five dimensional warped geometry with fourâ€¦ (More)

The semiclassical geometry of charged black holes is studied in the context of a two-dimensional dilaton gravity model where effects due to pair-creation of charged particles can be included in aâ€¦ (More)

We give a full nonlinear numerical treatment of time-dependent 5d braneworld geometry, which is determined self-consistently by potentials for the scalar field in the bulk and at two orbifold branes,â€¦ (More)

This paper studies the non-spherical perturbations of the continuously selfsimilar critical solution of the gravitational collapse of a massless scalar field (the Roberts solution). The exactâ€¦ (More)