The phenomenology of squeezing and its status in non-inflationary theories

Abstract

In this paper we skim the true phenomenological requirements behind the concept of inflationary squeezing. We argue that all that is required is that at horizon re-entry the fluctuations form standing waves with the correct temporal phase (specifically, sine waves). We quantify this requirement and relate it to the initial conditions fed into the radiation dominated epoch by whatever phase of the Universe produced the fluctuations. The only relevant quantity turns out to be the degree of suppression of the momentum, $p$, of the fluctuations, $y$, which we measure by $\sigma \sim {\omega }^2|y{|}^2/|p{|}^2$. Even though $\sigma$ equals the squeezing parameter, $s$, in the case of inflation and bimetric varying speed of light scenarios, this is not true in general, specifically in some bouncing Universe models. It is also not necessary to produce a large $\sigma$ at the end of the primordial phase: it is enough that $\sigma$ be not too small. This is the case with scenarios based on modified dispersion relations (MDR) emulating the dispersion relations of Horava-Lifshitz theory, which produce $\sigma \sim 1$, enough to comply with the observational requirements. Scenarios based on MDR leading to a slightly red spectrum are also examined, and shown to satisfy the observational constraints.

arXiv commentv2: Typos corrected. Matches the accepted version on JCAP

References in corpus (19)

• Quantum Gravity at a Lifshitz Point
• On the Generation of a Scale-Invariant Spectrum of Adiabatic Fluctuations in Cosmological Models with a Contracting Phase
• Inflation and squeezed quantum states
• Producing a Scale-Invariant Spectrum of Perturbations in a Hagedorn Phase of String Cosmology
• Quantum-to-classical transition for fluctuations in the early Universe
• Quantum Discord of Cosmic Inflation: Can we Show that CMB Anisotropies are of Quantum-Mechanical Origin?
• Cosmological Inflation and the Quantum Measurement Problem
• Causality, randomness, and the microwave background
• Cosmological Perturbations of Quantum-Mechanical Origin and Anisotropy of the Microwave Background
• Bimetric varying speed of light theories and primordial fluctuations
• Speedy sound and cosmic structure
• Rainbow gravity and scale-invariant fluctuations
• Dimensional reduction in the sky
• Bimetric structure formation: non-Gaussian predictions
• The critical geometry of a thermal big bang
• DSR as an explanation of cosmological structure
• Gravity as the breakdown of conformal invariance
• Inflation and the Measurement Problem
• Thermal Tachyacoustic Cosmology

Cited by in corpus (6)

• Unsqueezing of standing waves due to inflationary domain structure
• Life of cosmological perturbations in MDR models, and the prospect of travelling primordial gravitational waves
• Squeezing of scalar and tensor primordial perturbations generated by modified dispersion relations
• Cosmological Geometric Phase From Pure Quantum States: A study without/with having Bell's inequality violation
• Primordial standing waves
• Antipodal Angular Correlations of Inflationary Stochastic Gravitational Wave Background