Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Primordial Features as Evidence for Inflation

Xingang Chen

TL;DR

The paper addresses how to obtain unambiguous evidence for inflation (vs. alternatives) by identifying standard clocks in the primordial universe. It develops a two-field formalism in which massive spectator fields with $m_\sigma \gg H$ can be excited and act as clocks, imprinting both sinusoidal and resonant running in the primordial power spectrum $P_\zeta$ and bispectrum $S(k_1,k_2,k_3)$. Through analyses of sharp features and resonant running, the work derives explicit, robust signatures—CEL-like oscillations in $K$-space and in the logarithmic scaling of momenta—that encode the background scale-factor evolution. In the inflationary limit, the resulting expressions predict characteristic oscillatory patterns with amplitudes tied to the clock's energy and mass, offering concrete observables to distinguish inflationary dynamics from alternatives and to constrain the microphysics of the early universe.

Abstract

In the primordial universe, fields with mass much larger than the mass-scale of the event-horizon (such as the Hubble parameter in inflation) exist ubiquitously, and can be excited from time to time and oscillate quickly around their minima. These excitations can induce specific patterns in density perturbations, which record the time dependence of the scale factor of the primordial universe, thus provide direct evidence for the inflation paradigm or its alternatives. Such effects are conventionally averaged out in theoretical and data analyses, but can be accessible for experiments targeting on density perturbations with high multipoles.

Primordial Features as Evidence for Inflation

TL;DR

The paper addresses how to obtain unambiguous evidence for inflation (vs. alternatives) by identifying standard clocks in the primordial universe. It develops a two-field formalism in which massive spectator fields with can be excited and act as clocks, imprinting both sinusoidal and resonant running in the primordial power spectrum and bispectrum . Through analyses of sharp features and resonant running, the work derives explicit, robust signatures—CEL-like oscillations in -space and in the logarithmic scaling of momenta—that encode the background scale-factor evolution. In the inflationary limit, the resulting expressions predict characteristic oscillatory patterns with amplitudes tied to the clock's energy and mass, offering concrete observables to distinguish inflationary dynamics from alternatives and to constrain the microphysics of the early universe.

Abstract

In the primordial universe, fields with mass much larger than the mass-scale of the event-horizon (such as the Hubble parameter in inflation) exist ubiquitously, and can be excited from time to time and oscillate quickly around their minima. These excitations can induce specific patterns in density perturbations, which record the time dependence of the scale factor of the primordial universe, thus provide direct evidence for the inflation paradigm or its alternatives. Such effects are conventionally averaged out in theoretical and data analyses, but can be accessible for experiments targeting on density perturbations with high multipoles.

Paper Structure

This paper contains 6 sections, 37 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Bunch-Davies vacuum and resonance mechanism
  3. Spectator massive fields as standard clock
  4. Model and formalism
  5. Sinusoidal running as trigger
  6. Resonant running as evidence

Figures (3)

  • Figure 1: A turning trajectory that excites the oscillation of massive fields. Dashed line indicates the potential valley. The massive field tends to settle down in the valley along the incoming and outgoing straight lines. But during the turning, the centrifugal force makes it deviate from the minimum. This induces the small oscillation.
  • Figure 2: Examples of Feynman diagrams used to perturbatively compute the power spectra and bispectra in feature models.
  • Figure :