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Alexander Vilenkin

Publications and source records attributed to Alexander Vilenkin.

151 records · Page 9Linked to original sources
arXiv1994

The Impossibility of Steady-State Inflation

Inflation is known to be generically eternal to the future: the false vacuum is thermalized in some regions of space, while inflation continues in other regions. Here, we address the question of whether inflation can also be eternal to the past. We argue that such a steady-state picture is impossible and, therefore, that inflation must have had a beginning. First, it is shown that the old inflationary model is not past-eternal. Next, some necessary conditions are formulated for inflationary spacetimes to be past-eternal and future-eternal. It is then shown that these conditions cannot simultaneously hold in physically reasonable open universes.

gr-qc↗
arXiv1994

Approaches to Quantum Cosmology

Different proposals for the wave function of the universe are analyzed, with an emphasis on various forms of the tunneling proposal. The issues discussed include the equivalence of the Lorentzian path integral and outgoing-wave proposals, the definitions of the outgoing waves and of superspace boundaries, topology change and the corresponding modification of the Wheeler-DeWitt equation. Also discussed are the "generic" boundary conditions and the third quantization approach.

gr-qc↗
arXiv1994

Topological Inflation

Inflation can occur in the cores of topological defects, where the scalar field is forced to stay near the maximum of its potential. This topological inflation does not require fine-tuning of the initial conditions.

hep-th↗
arXiv1993

Quantum Cosmology

An elementary review of quantum cosmology. (Talk given at Texas/Pascos 1992 at Berkeley)

gr-qc↗
arXiv1992

Decay of Metastable Topological Defects

We systematically analyze the decay of metastable topological defects that arise from the spontaneous breakdown of gauge or global symmetries. Quantum-mechanical tunneling rates are estimated for a variety of decay processes. The decay rate for a global string, vortex, domain wall, or kink is typically suppressed compared to the decay rate for its gauged counterpart. We also discuss the decay of global texture, and of semilocal and electroweak strings.

hep-ph↗
arXiv1992

Black Holes from Nucleating Strings

We evaluate the probability that a loop of string that has spontaneously nucleated during inflation will form a black hole upon collapse, after the end of inflation. We then use the observational bounds on the density of primordial black holes to put constraints on the parameters of the model. Other constraints from the distortions of the microwave background and emission of gravitational radiation by the loops are considered. Also, observational constraints on domain wall nucleation and monopole pair production during inflation are briefly discussed.

hep-ph↗