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$D$-term inflation, cosmic strings, and consistency with cosmic microwave background measurement

Jonathan Rocher, Mairi Sakellariadou

TL;DR

The paper investigates whether standard D-term inflation, embedded in $N=1$ supergravity, can be consistent with CMB observations despite producing cosmic strings. Using one-loop radiative corrections and minimal supergravity, it expresses the CMB contributions from inflaton and cosmic strings as functions of $g$, $\lambda$, and $\xi$, employing $N_Q=60$ e-foldings and the Lambert $W$ function. The main finding is that the cosmic strings contribution is not constant or universally dominant, yielding constraints such as $\sqrt{\xi} \lesssim 2\times 10^{15}$ GeV and $\lambda \lesssim 3\times 10^{-5}$ for small $g$, though the curvaton mechanism can relax these bounds. Overall, the simplest D-term inflation remains viable under current data, with tighter parameter limits but no need for extra new physics, and curvaton dynamics offering a path to broader compatibility.

Abstract

Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings, however it can still be compatible with CMB measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained.

$D$-term inflation, cosmic strings, and consistency with cosmic microwave background measurement

TL;DR

The paper investigates whether standard D-term inflation, embedded in supergravity, can be consistent with CMB observations despite producing cosmic strings. Using one-loop radiative corrections and minimal supergravity, it expresses the CMB contributions from inflaton and cosmic strings as functions of , , and , employing e-foldings and the Lambert function. The main finding is that the cosmic strings contribution is not constant or universally dominant, yielding constraints such as GeV and for small , though the curvaton mechanism can relax these bounds. Overall, the simplest D-term inflation remains viable under current data, with tighter parameter limits but no need for extra new physics, and curvaton dynamics offering a path to broader compatibility.

Abstract

Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings, however it can still be compatible with CMB measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained.

Paper Structure

This paper contains 3 sections, 10 equations, 3 figures.

Table of Contents

  1. Introduction
  2. D-term inflation
  3. Conclusions

Figures (3)

  • Figure 1: The cosmic strings contribution to the CMB data, as a function of the mass scale $\sqrt{\xi}$ in units of $10^{15}$ GeV.
  • Figure 2: Cosmic strings contribution to the CMB temperature anisotropies as a function of the superpotential coupling $\lambda$ for different values of the gauge coupling $g$. The maximal contribution allowed by WMAP is represented by a dotted line.
  • Figure 3: The cosmic strings (dark gray), curvaton (light gray) and inflaton (gray) contributions to the CMB temperature anisotropies as a function of the the initial value of the curvaton field ${\cal\psi}_{\rm init}$, for $\lambda=10^{-1}$ and $g=10^{-1}$.