Gibbons-Hawking Temperature Research Articles

A Converse Hawking-Unruh Effect and dS2/CFT Correspondence

Given a local quantum field theory net A on the de Sitter spacetime dS^d, where geodesic observers are thermalized at Gibbons-Hawking temperature, we look for observers that feel to be in a ground state, i.e. particle evolutions with positive generator, providing a sort of converse to the Hawking-Unruh effect. Such positive energy evolutions always exist as noncommutative flows, but have only a partial geometric meaning, yet they map localized observables into localized observables. We characterize the local conformal nets on dS^d. Only in this case our positive energy evolutions have a complete geometrical meaning. We show that each net has a unique maximal expected conformal subnet, where our evolutions are thus geometrical. In the two-dimensional case, we construct a holographic one-to-one correspondence between local nets A on dS^2 and local conformal non-isotonic families (pseudonets) B on S^1. The pseudonet B gives rise to two local conformal nets B(+/-) on S^1, that correspond to the H(+/-)-horizon components of A, and to the chiral components of the maximal conformal subnet of A. In particular, A is holographically reconstructed by a single horizon component, namely the pseudonet is a net, iff the translations on H(+/-) have positive energy and the translations on H(-/+) are trivial. This is the case iff the one-parameter unitary group implementing rotations on dS^2 has positive/negative generator.

Temperature at the first stage of reheating in in flationary cosmology without slow rolling

We consider statistical properties of massive non-relativistic bosons arising at the first stage of reheating as a result of quantum decay of a classical inflaton field. We use the cosmological model describing the dynamics of a transition from the inflationary stage to a quasi-dust stage without imposing the slow-rolling hypothesis. In this framework, we apply statistics and find that the process of emerging of massive non-relativistic bosons at the first stage of reheating looks like evaporation of a Bose condensate. They are described by the equation of state for an ideal quantum degenerate Bose gas which has the Gibbons-Hawking temperature related to the de Sitter event horizon.

EQUATION OF STATE AND TEMPERATURE OF MASSIVE NONRELATIVISTIC BOSONS ARISING IN THE UNIVERSE AT THE FIRST STAGE OF REHEATING

We consider heavy nonrelativistic bosons with masses M~MGUT which arise in the Universe during phase transitions with spontaneous symmetry breaking at the grand unification scale. In the frame of statistical mechanics approach with model-independent description of cosmological background we show that the process of emerging of massive GUT bosons looks like evaporation of a Bose condensate. First massive nonrelativistic bosons behave like ideal quantum degenerate Bose gas which has the Gibbons-Hawking temperature due to the presence of the de Sitter event horizon.

Tunneling in cosmology and isothermal inflation

The wave function for the universe, as proposed by Hartle and Hawking, experiences tunneling for small values of the radius of the universe. This induces thermal effects and so a hot big bang. We first give a detailed analysis of the observer accelerating in Minkowski space in terms of the tunneling of his wave function beyond his turning point. Applied to cosmology one finds a temperature at the big bang equal to the Gibbons-Hawking value. The residual thermal effects which result in an isothermal inflationary expansion give rise to a renormalized self-consistently determined Hubble constant (and hence Gibbons-Hawking temperature) through the trace anomaly. A thermodynamic interpretation is given. These results militate against phase transitions as a motor for inflation.

String-driven inflationary and deflationary cosmological models

A detailed study is made of inflationary universe driven by the quantum production of infinitely thin Witten strings on super-horizon scales in the very early universe. We show that these models are equivalent to the addition of an effective bulk viscosity to perfect fluid cosmological models with zero curvature. A large number of new exact solutions describing the effects of string creation upon isotropic universes are found. They exhibit either inflationary expansion to a de Sitter state from an initial Friedmann singularity or deflationary approach to the standard Friedmann universe from a de Sitter state at t= - ∞. We show that the deflationary models, which possess an initial string-dominated de Sitter phase with a maximum string temperature given by the Gibbons-Hawking temperature of the de Sitter event horizon, cease to exist in the presence of expansion anisotropies or the presence of further matter fields uncoupled from the string density. In both cases the initial string-dominated de Sitter era is replaced by an initial singularity at which the string density vanishes. We show that application of the generalized second law of black hole thermodynamics to the event horizons of the string-dominated models excludes some evolutionary behaviours. We give examples of globally static de Sitter universes which are not in local thermal equilibrium.

Stochastic gravity-wave background in inflationary-universe models.

The gravitational-wave-noise power spectrum P(\ensuremath{\omega}) is found for a simple cosmological model with an ``inflationary'' early stage of expansion. The source of the gravitational-wave noise is quantum fluctuations during the inflationary de Sitter stage, which are amplified by the subsequent expansion of the Universe. The resulting spectrum P(\ensuremath{\omega}) is compared to a naive estimate: a thermal spectrum at the (appropriately red-shifted) Gibbons-Hawking temperature. The two spectra are remarkably different. Unlike the thermal spectrum, P(\ensuremath{\omega}) increases at low frequencies. We show that the source of the corresponding long-wavelength perturbations is a global gravitational instability during the inflationary de Sitter stage of expansion. An interesting consequence of the low-frequency behavior of P(\ensuremath{\omega}) is that gravitational radiation contributes a constant fraction of the energy density of the Universe, even after the time of matter domination.

Gravitational particle creation and inflation.

Particle creation due to the changing spacetime metric at the end of an inflationary era in the early Universe is discussed. The Universe is assumed to make a transition from de Sitter space to either a radiation-dominated or matter-dominated universe. A perturbation approach is used to calculate the number density and energy density of massless, nonconformally coupled particles created by this transition. It is found that their energy density is typically of the order of ${\ensuremath{\rho}}_{v}$${\mathrm{}}^{2}$/${\ensuremath{\rho}}_{\mathrm{Pl}}$, where ${\ensuremath{\rho}}_{v}$ is the value of the cosmological constant in the de Sitter phase and ${\ensuremath{\rho}}_{\mathrm{Pl}}$ is the Planck energy density. This is approximately the energy density of a thermal bath at the Gibbons-Hawking temperature of de Sitter space. The possible applications of this effect to inflationary models is discussed. It is shown that gravitational particle creation is capable of reheating the Universe after inflation and of being the source of the matter in the Universe. This effect makes it possible to avoid the difficulty with reheating which inflationary models with weakly coupled scalar fields otherwise encounter.