R. Brout

The Creation of the Universe as a Quantum Phenomenon

Quantum creation of massy particles can occur in the cosmological context without cost of energy. This fact is seized upon to construct a causal open homogeneous isotropic cosmology. The universe is conceived as the response of matter and the gravitational field to a spontaneous pointlike disturbance. Its history unfolds in two stages, creation and free expansion. The first stage gives rise to a “fireball.” The free expansion is extrapolated back to the “fireball.” The latter thus replaces the “big-bang,” thereby avoiding an initial singularity. Though not intrinsic to the theory it does suggest the interpretation of the cosmological part of the gravitational field as the scalar dilaton that is encountered in the dynamical generation of mass in conformally invariant theory.

A Primer for black hole quantum physics

Abstract The mechanisms which give rise to Hawking radiation are revealed by analyzing in detail pair production in the presence of horizons. In preparation for the black hole problem, three preparatory problems are dwelt with at length: pair production in an external electric field, thermalization of a uniformly accelerated detector and accelerated mirrors. In the light of these examples, the black hole evaporation problem is then presented. The leitmotif is the singular behavior of modes on the horizon which gives rise to a steady rate of production. Special emphasis is put on how each produced particle contributes to the mean albeit arising from a particular vacuum fluctuation. It is the mean which drives the semiclassical back reaction. This aspect is analyzed in more detail than heretofore and in particular its drawbacks are emphasized. It is the semiclassical theory which gives rise to Hawkings famous equation for the loss of mass of the black hole due to evaporation d M d t − −1 M 2 . Black hole thermodynamics is derived from the evaporation process whereupon the reservoir character of the black hole is manifest. The relation to the thermodynamics of the eternal black hole through the Hartle-Hawking vacuum and the Killing identity are displayed. It is through the analysis of the fluctuations of the field configurations which give rise to a particular Hawking photon that the dubious character of the semiclassical theory is manifest. The present frontier of research revolves around this problem and is principally concerned with the fact that one calls upon energy scales that are greater than Planckian and the possibility of a non unitary evolution as well. These last subjects are presented in qualitative fashion only, so that this review stops at the threshold of quantum gravity.

Chiral symmetry breaking in the action formulation of lattice gauge theory

Abstract We show, in the euclidean path-integral formulation of strong-coupling lattice gauge theory, that continuous chiral symmetry is dynamically broken, and obtain the standard current algebra result that m pseudo-Goldstone 2 ∼ m quark 〈 ψ ψ〉 . We also remark that the center of the gauge group does not seem very relevant for this result; chiral symmetry breaking is a property of strong-coupling lattice theories both in the case where quark color is confined, and also in the case where it is screened by gauge field fluctuations.

The causal universe

Creation of matter is possible in the cosmological context, without cost of energy. This creation is regulated by the laws of quantum mechanics and general relativity. These elements are used to conceive a singularity-free causal open homogeneous isotropic cosmology. The history of the universe unfolds in two stages: the “fireball” production stage, which occurs as the response to a spontaneous local disturbance, is followed by free expansion. The latter extrapolates back to the former to avoid the initial “big-bang” singularity.

Rotational Energy Transfer in H2

Rotational energy deactivation probabilities have been calculated for H2 using the quantum‐mechanical method of distorted waves. Approximate procedures have been indicated for further extensions of these calculations to other symmetric diatomic molecules. Comparison with data from sound dispersion measurements shows good agreement between theory and experiment.

Cosmogenesis and the origin of the fundamental length scale

The creation of the universe is regarded as a self-consistent process in which matter is engendered by the space-time varying cosmological gravitational field and vice versa. Abundant production can occur only if the mass of the particles so created is of the order of the Planck mass (= κ−12. We conjecture that this is the origin of the fundamental length scale in field theory, as it is encountered, for example, in present efforts towards grandunification. The region of particle production is steady state in character. It ceases when the produced particles decay. The geometry of this steady state is characteristic of a de Sitter space. It permits one to estimate the number of ordinary particles presently observed, N. We find log N = O (mτdecay) = O(g−2) = O(102), with the usual estimate of g = O(10− at the Planck length scale. This is not inconsistent with the experimental estimate N ⋍ O(1090). After production, cosmological history gives way to the more conventional scheme of free expansion. The present paper is a self-contained account of our view of cosmological history and the production of matter in a varying gravitational field. Special care has been taken to describe the vacuum correctly in the present context and to perform the necessary subtractions of zero-point effects.

On the onset of time and temperature in cosmology

It is shown how the evolution of matter is parametrized by classical time in cosmological configurations that propagate. But behind the horizon, this time becomes imaginary. In a simple model, it is shown that in this classically inaccessible region, the imaginary time gives rise to a heating-up of the matter.

On the problem of the uniformly accelerated oscillator

The particle detector model consisting of a harmonic oscillator coupled to a scalar field in 1+1 dimensions is investigated in the inertial case. The same approach is then used in the accelerating case. The absence of radiation from a uniformly accelerated detector in a stationary state is discussed and clarified.

Thermal properties of pairs produced by an electric field: A tunneling approach

Abstract It is well known that the presence of a constant electric field in Minkowski space induces pair production from vacuum. The population ratios of pairs of different mass so produced is Boltzmann in character, the temperature being a /2 π ; where a is the acceleration due to the field. These ratios are maintained subsequent to production when the interaction of the charged particles with the vacuum of neutral radiation is taken into account, i.e. particles are born in a thermal equilibrium which is maintained dynamically. We attempt to explain this consistency in terms of the tunneling of the wave function behind the classical turning point.

Chiral symmetry and linear trajectories

Abstract It is shown that chiral symmetry (μ2π = 0), absence of I = 2 resonances and single particle saturation imply that the π and ϱ trajectories rise linearly and differ in intercept by 1 2 .