Asymptotic Behavior of Perturbations in Randall-Sundrum Brane-World

The asymptotic behavior of metric perturbations in Randall-Sundrum infinite brane world is carefully investigated. Perturbations generated by matter fields on the brane are shown to be regular even at the future Cauchy horizon.Comment: 5 page

Decoherence on Quantum Tunneling in the Multi-Dimensional Wave Function Approach

We consider fundamental problems on the understanding of the tunneling phenomena in the context of the multi-dimensional wave function. In this paper, we reconsider the quantum state after tunneling and extend our previous formalism to the case when the quantum state before tunneling is in a squeezed state. Through considering this problem, we reveal that the quantum decoherence plays a crucial role to allow us of the concise description of the quantum state after tunneling.Comment: 27 pages revtex file, uuencoded postscript figure file is avilable from [email protected] upon request, KUNS129

Implication of Classical Black Hole Evaporation Conjecture to Floating Black Holes

In Randall-Sundrum single-brane (RS-II) model, it was conjectured that there is no static large black hole localized on the brane based on adS/CFT correspondence. Here we consider the phase diagram of black objects in the models extended from the RS-II model. We propose a scenario for the phase diagram consistent with the classical black hole evaporation conjecture. The proposed scenario indicates the existence of a rich variety of the families of black objects.Comment: 4 pages, 4 figures, Removed ambiguous discussions and corrected errors. Added reference

Bigravity from gradient expansion

We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.Comment: 16 page

QFT in the flat chart of de Sitter space

We study the correlators for interacting quantum field theory in the flat chart of de Sitter space at all orders in perturbation. The correlators are calculated in the in-in formalism which are often applied to the calculations in the cosmological perturbation. It is shown that these correlators are de Sitter invariant. They are compared with the correlators calculated based on the Euclidean field theory. We then find that these two correlators are identical. This correspondence has been already shown graph by graph but we give an alternative proof of it by direct calculation.Comment: 24 pages, 7 figures. References added with some minor corrections. To appear in Phys. Rev.

Conservation of ζ\zeta with radiative corrections from heavy field

In this paper, we address a possible impact of radiative corrections from a heavy scalar field $\chi$ on the curvature perturbation $\zeta$. Integrating out $\chi$, we derive the effective action for $\zeta$, which includes the loop corrections of the heavy field $\chi$. When the mass of $\chi$ is much larger than the Hubble scale $H$, the loop corrections of $\chi$ only yield a local contribution to the effective action and hence the effective action simply gives an action for $\zeta$ in a single field model, where, as is widely known, $\zeta$ is conserved in time after the Hubble crossing time. Meanwhile, when the mass of $\chi$ is comparable to $H$, the loop corrections of $\chi$ can give a non-local contribution to the effective action. Because of the non-local contribution from $\chi$, in general, $\zeta$ may not be conserved, even if the classical background trajectory is determined only by the evolution of the inflaton. In this paper, we derive the condition that $\zeta$ is conserved in time in the presence of the radiative corrections from $\chi$. Namely, we show that when the scaling symmetry, which is a part of the diffeomorphism invariance, is preserved at the quantum level, the loop corrections of the massive field $\chi$ do not disturb the constant evolution of $\zeta$ at super Hubble scales. In this discussion, we show the Ward-Takahashi identity for the scaling symmetry, which yields a consistency relation for the correlation functions of the massive field $\chi$.Comment: 27 pages, 1 figure; v2: updated references and minor revision