A new vacuum state in de Sitter space

We present a new vacuum state which can be defined in a region of de Sitter space. This region corresponds to a K=?1 Robertson-Walker coordinatization of de Sitter space. The renormalized expectation value of the stress tensor for the conformally invariant massless scalar field in this vacuum is evaluated, and is found to differ from the corresponding result in the usual de Sitter-invariant vacuum by the absence of a pure radiation term. We also indicate that this can be accounted for by regarding the de Sitter-invariant vacuum as a thermal state relative to the new vacuum.     

Casimir Effect for Moving Branes in Static dS4+1 Bulk

In this paper we study the Casimir effect for conformally coupled massless scalar fields on background of Static dS₄₊₁ spacetime. We will consider the general plane–symmetric solutions of the gravitational field equations and boundary conditions of the Dirichlet type on the branes. Then we calculate the vacuum energy-momentum tensor in a configuration in which the boundary branes are moving by uniform proper acceleration in static de Sitter background. Static de Sitter space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energy-momentum tensor for conformally invariant field in static de Sitter space from the corresponding Rindler counterpart by the conformal transformation.     

Dynamics of superhorizon photons during inflation with vacuum polarization

We study asymptotic dynamics of photons propagating in the polarized vacuum of a locally de Sitter Universe. The origin of the vacuum polarization is fluctuations of a massless, minimally coupled, scalar, which we model by the one-loop vacuum polarization tensor of scalar electrodynamics. We show that late time dynamics of the electric field on superhorizon scales approaches that of an Airy oscillator. The magnetic field amplitude, on the other hand, asymptotically approaches a nonvanishing constant (plus an exponentially small oscillatory component), which is suppressed with respect to the initial (vacuum) amplitude. This implies that the asymptotic photon dynamics is more intricate than that of a massive photon obeying the local Proca equation.     

Quantum effects in cosmological models with singularities

The vacuum expectation values of the energy-momentum tensor of quantized scalar and spinor fields in a de Sitter space of the first kind are calculated. Limiting cases of the obtained exact expressions are considered. It is noted that the de Sitter space is a self-consistent solution of the Einstein equations with allowance for quantum vacuum fluctuations of massless fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 67–70, January, 1981.I thank V. M. Mostepanenko and B. N. Sharapov for numerous helpful discussions.     

Gravitational radiation in asymptotic de Sitter space

A solution of the gravitational field equations is found by using an axially symmetric metric which is asymptotically a de Sitter space metric. We use the general approach of Bondi, van der Burg, and Metzner as applied to the asymptotic flat-space case and search for the necessary conditions for gravitational radiation in asymptotic de Sitter space. We find that the character of the gravitational radiation, if it exists at all, is considerably different from that obtained in the case of asymptotic flat space.     

Hawking-de Sitter Thermalization of Quasi-Minkowskian Massless Scalaron Production,Energy Density Content and Back-Reaction

Projecting the closed form expression of the de Sitter scalar field operator onto the Minkowskian positive frequency massless modes, we compute the corresponding Bogolubov coefficient which is associated to the (massless) quasiparticle creation during the stationary quasi-de Sitter stage of the Universe. Thereafter, we derive the expression of the thermalized energy density which reveals an interesting mixture of de Sitter false vacuum and dark-radiation, exotic dust and black body radiation. Setting the temperature to the value of the Hawking one for the de Sitter spacetime, we finally analyze the (straightforward) back-reaction of the newly created “matter” on the scale function. It basically points out three stages of highly continuous evolution represented by an initially short radiation-like era, a somewhat long-lasting connecting phase made of coherent massless oscillations, in its beginnings, ended up by the dark-radiation (i.e. curvature-like term) contribution and, finally, a much slower exponential expansion than the initial de Sitter one.     

Inflationary fluctuations,entropy generation and baryogenesis in a cold universe

We study the implications of a generic inflationary model for scenarios of baryogenesis based on the decays of coherent oscillations of squark and slepton fields. We consider the effects of de Sitter fluctuations on the magnitudes of the coherent oscillations of squarks and sleptons. We see that the largest contribution to the entropy density is due to inflaton decays which together with the value of the oscillation amplitude determined by the de Sitter fluctations leads to a baryon to entropy ratio O(10⁻¹⁰). The isothermal density fluctuations produced by the coherent oscillations are found to be negligible compared with the adiabatic fluctuations produced during inflation     

A gauge field theory of spacetime based on the de Sitter group

A new theory of spacetime is proposed in which translations are considered as a part of the de Sitter gauge group. The theory is built along the general principles of classical gauge field theories, which are outlined. Applications of gauge principles to linear and affine connections are also given in order to make the presentation self-sufficient. A de Sitter invariant Lagrangian is constructed, which yields approximately Einstein's vacuum equations when it is subjected to variation with respect to gauge potentials and the result expressed in a specific gauge class. As a difference from the usual use of de Sitter groups, the radius of its translations must be small in the present approach, which probably has the meaning of an elementary subatomic length. The solution of the equations describing flat spacetime is not the trivial zero-curvature connection of the conventional approach.     

Quantum Linear Gravity in de Sitter Universe on Gupta-Bleuler Vacuum State

Application of Krein space quantization to the linear gravity in de Sitter space-time have constructed on Gupta-Bleuler vacuum state, resulting in removal of infrared divergence and preserving de Sitter covariant. By pursuing this path, the non uniqueness of vacuum expectation value of the product of field operators in curved space-time disappears as well. Then the vacuum expectation value of the product of field operators can be defined properly and uniquely.     

Neutrino Tunneling from NUT Kerr Newman de Sitter Black Hole

In this paper, the method of semi-classical is applied to explore the Hawking radiation of a NUT-Kerr-Newman de Sitter Black Hole from tunneling point of view. The Hamilton-Jacobi equation in NUT-Kerr-Newman de Sitter space time is derived by the method presented by Lin and Yang (Chin. Phys. B, 20:110403, 2011). We obtain the Hawking temperatures at the event horizon and cosmological horizon and we also obtain the tunneling probability of neutrino following the semi-classical quantum equation. The results show the common features of NUT-Kerr-Newman de Sitter Black Hole.     

Gravitational waves generated during inflation from a 5D vacuum theory of gravity in a de Sitter expansion

In this Letter we study the generation of gravitational waves during inflation from a 5D vacuum theory of gravity. Within this formalism, on an effective 4D de Sitter background, we recover the typical results obtained with 4D inflationary theory in general relativity, for the amplitude of gravitational waves generated during inflation. We also obtain a range of values for the amplitude of tensor to scalar ratio which is in agreement with COBE observations.     

Thermal instability of the de Sitter vacuum

Assuming thermal equilibrium between the hot de Sitter vacuum and thermal radiation we obtain the second moments in the fluctuations of the energy around that equilibrium. Its stability imposes an upper limit on the temperature of this vacuum.     

Semiclassical gravitoelectromagnetic inflation in a Lorentz gauge: Seminal inflaton fluctuations and electromagnetic fields from a 5D vacuum state

Using a semiclassical approach to Gravitoelectromagnetic Inflation (GEMI), we study the origin and evolution of seminal inflaton and electromagnetic fields in the early inflationary universe from a 5D vacuum state. The difference with other previous works is that in this one we use a Lorentz gauge. Our formalism is naturally not conformal invariant on the effective 4D de Sitter metric, which make possible the super adiabatic amplification of magnetic field modes during the early inflationary epoch of the universe on cosmological scales.     

Adiabatic invariants and scalar fields in a de Sitter space-time

The method of adiabatic invariants for time dependent Hamiltonians is applied to a massive scalar field in a de Sitter space-time. The scalar field ground state, its Fock space and coherent states are constructed and related to the particle states. Diverse quantities of physical interest are illustrated and compared with previous results.     

From unstable Minkowski space to the inflationary universe

It is shown that Minkowski space is unstable in the context of semiclassical gravity. There exists a threshold mass, of the quantized matter field, which marks the dividing line between stable and unstable vacuum fluctuations of matter in flat space-time. The Minkowski vacuum gravitational-matter system undergoes a phase transition above this critical point, the new phase being a self-consistently generated de Sitter Euclidean cosmology. Its total energy is degenerate with respect to that of empty Minkowski space-time. It represents an appropriate candidate for the primeval configuration of an inflationarylike universe.This essay received the fourth award from the Gravity Research Foundation for the year 1983 [Ed.].     

Populating the whole landscape

Every de Sitter vacuum can transition to every other de Sitter vacuum despite any obstacle, despite intervening anti-de Sitter sinks, despite not being connected by an instanton. Eternal inflation populates the whole landscape.     

Hawking Radiation from the Higher-Dimensional Schwarzschild de Sitter and Anti-de Sitter Black Holes via Covariant Anomaly

Very recently, a conceptually clean and economical anomaly cancellation method, based on the initial work of Robinson and Wilczek, on Hawking radiation was proposed. On the basis of this formalism, we investigate Hawking radiation from the higher dimensional Schwarzschild de Sitter and Anti-de Sitter black holes. To describe the observable physics in de Sitter space, we construct the effective field theory between the event horizon and cosmological horizon. Our result shows that when the underlying diffeomorphism symmetries are saved at the quantum level, Hawking radiation, from not only the event horizon but also the cosmological horizon in the higher dimensional space time, can be determined by the covariant compensating fluxes of energy momentum tensor. Meanwhile, we also discuss the exact radiation spectrum by incorporating the self-gravitational interaction and back reaction of the outgoing modes.     

New solutions of the Einstein equations taking into account the vacuum effects of quantized fields

The Einstein equations are solved, whose right-hand sides involve both the background matter and the vacuum effects of quantized fields. It is shown that the de Sitter model is stable with respect to perturbations due to the vacuum corrections. For all other homogeneous isotropic models, taking the vacuum polarization into account makes the singularity occur earlier.