Cosmological Particle Production Research Articles

On the dynamics of cosmological particle production

The time evolution of the particle number density and spectrum of massive scalar particles, coupled conformally to a classical Friedman-Robertson-Walker gravitational field is followed numerically. Not only for a pure radiation cosmos, but also for one with an inflationary interlude, the density of particles produced remains constant in time. This results in a constant equivalent “temperature” scale up to the Compton time of the massive particles, and opens the possibility that during a sufficiently long inflation the energy density of the particles produced can exceed that of the radiation background.

Canonical quantization and cosmological particle production in non-abelian gauge theories

A canonical quantization scheme for non-abelian gauge fields in an external, classical gravitational field is formulated and applied to the problem of cosmological Higgs and gauge boson production. Via interaction, the mass of the Higgs field not only leads to additional Higgs production, but also enables the production of massless gauge bosons.

Classical fluctuations in dissipative quantum systems.

Dissipative quantum systems such as an unstable field, thermal field, and cosmological particle production are investigated. Equations of motion for each appropriate mean field are revealed to be Langevin type. The derived correlation of the random field turns out not to be Gaussian nor white in general. A relation between a popular quantum average and the statistical correlation is also clarified.

Quantum dissipative processes and gravitational entropy of the universe

We discuss the meaning of gravitational entropy of the universe when quantum dissipative processes like cosmological particle production are important and propose to use the entropy generated in these processes as a measure of the change in gravitational entropy of the spacetime dynamics. Penrose's Weyl Curvature Hypothesis is re-examined in this generalized context. It is shown that gravitational entropy defined as such can actually decrease in the quantum regime by the action of vacuum viscosity. The theoretical and cosmological implications of this postulate is discussed.

An observational test of cosmological particle production theories

It is shown that, although cosmological particle production is too small to be seen directly, the production of particles which decay through the emission of photons leads to an isotropic X-ray/gamma-ray background which is observable. An approximate expression for part of the differential photon flux spectrum is derived. This expression is evaluated for several examples and compared to observations.

Spectral asymmetry and quantum field theory in curved spacetime

I discuss cosmological particle production in spaces with spectral asymmetry. A change in the amount of spectral symmetry sufficient to produce a level crossing will result in the creation of neutrino pairs rather than neutrino, antineutrino pairs; the net excess of fermions being given by the number of level crossing. A symmetric Bianchi IX model is treated in detail and for large initial anisotropy the number of neutrinos produced is ( 1 256 ) exp 12 β + where β + is a measure of the initial anisotropy. The relation of this phenomenon to chiral anomalies and to the Atiyah-Patodi-Singer index theorem for manifolds with boundary is described. The effect of spectral asymmetry on photons is discussed and it is shewn that no level crossing can occur.

Cosmological particle creation

We present a simple alternative derivation of cosmological particle production in models with an initial singularity using the Lewis invariant for the time-dependent harmonic oscillator.

Path-integral quantization and cosmological particle production: An example

The Feynman path-integral method is applied to the quantization of a scalar field moving in a cosmological background spacetime. The method is illustrated by computing particle production from the vacuum in a spatially flat, Robertson-Walker spacetime with scale factor $R(t)=t$. The result is a distribution of produced particle pairs which at large energies becomes a thermal distribution with a temperature $T=\frac{\ensuremath{\hbar}c}{\ensuremath{\pi}{k}_{B}R(t)}$. The relation to other methods of quantization is discussed.

Quantum field theory in curved space–time

Recent theoretical developments indicate that the presence of gravity (curved space–time) can give rise to important new quantum effects, such as cosmological particle production and black-hole evaporation. These processes hint at intriguing new relations between quantum theory, thermodynamics and space–time structure and encourage the hope that a better understanding of a full quantum theory of gravity may emerge from this approach.