Squeezed States in the de Sitter Vacuum

TL;DR

This paper analyzes squeezed states in de Sitter space, highlighting their consistency in interacting theories and implications for cosmological inflation, contrasting them with alpha-vacua.

Contribution

It clarifies the treatment of squeezed states as physical excitations in de Sitter space and demonstrates their renormalizability and consistency in interacting theories.

Findings

Squeezed states are consistent excitations in de Sitter space.

Alpha-vacua are inconsistent at the interacting level.

Squeezed states can be renormalized with standard counterterms.

Abstract

We discuss the treatment of squeezed states as excitations in the Euclidean vacuum of de Sitter space. A comparison with the treatment of these states as candidate no-particle states, or alpha-vacua, shows important differences already in the free theory. At the interacting level alpha-vacua are inconsistent, but squeezed state excitations seem perfectly acceptable. Indeed, matrix elements can be renormalized in the excited states using precisely the standard local counterterms of the Euclidean vacuum. Implications for inflationary scenarios in cosmology are discussed.