Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

D3/D7 Brane Inflation and Semilocal Strings

Keshav Dasgupta, Jonathan P. Hsu, Renata Kallosh, Andrei Linde, Marco Zagermann

TL;DR

This work extends D3/D7 brane inflation to include richer global and local symmetries, transforming topologically stable ANO strings into semilocal strings that preserve 1/2 of the original supersymmetry in N=1 supergravity. The authors establish a detailed dictionary between the brane construction and the 4D P-term framework, analyze warp-factor effects, and demonstrate that semilocal strings can form without generating problematic large-scale CMB perturbations. They derive 1/2-BPS semilocal vortex solutions, show their thickness can vary without energy cost, and argue that these strings dissipate rather than survive as long cosmic filaments. The results relax the stringent requirement of an extremely small gauge coupling and improve the viability of fully realistic D3/D7 inflation models with moduli stabilization.

Abstract

Among the inflationary models based on string theory, the D3/D7 model has the advantage that the flatness of the inflaton potential can be protected even with moduli stabilization. However, the Abrikosov-Nielsen-Olesen BPS cosmic strings produced at the end of original D3/D7 inflation lead to an additional contribution to the CMB anisotropy. To make this contribution consistent with the WMAP results one needs an extremely small gauge coupling in the effective D-term inflation model. Such couplings may be difficult to justify in string theory. Here we develop a generalized version of the D3/D7 brane model, which leads to semilocal strings, instead of the topologically stable ANO cosmic strings. We show that the semilocal strings have unbroken supersymmetry when embedded into supergravity with FI terms. The energy of these strings is independent of their thickness. We confirm the existing arguments that strings of such type disappear soon after their formation and do not pose any cosmological problems, for any value of the gauge coupling. This should simplify the task of constructing fully realistic models of D3/D7 inflation.

D3/D7 Brane Inflation and Semilocal Strings

TL;DR

This work extends D3/D7 brane inflation to include richer global and local symmetries, transforming topologically stable ANO strings into semilocal strings that preserve 1/2 of the original supersymmetry in N=1 supergravity. The authors establish a detailed dictionary between the brane construction and the 4D P-term framework, analyze warp-factor effects, and demonstrate that semilocal strings can form without generating problematic large-scale CMB perturbations. They derive 1/2-BPS semilocal vortex solutions, show their thickness can vary without energy cost, and argue that these strings dissipate rather than survive as long cosmic filaments. The results relax the stringent requirement of an extremely small gauge coupling and improve the viability of fully realistic D3/D7 inflation models with moduli stabilization.

Abstract

Among the inflationary models based on string theory, the D3/D7 model has the advantage that the flatness of the inflaton potential can be protected even with moduli stabilization. However, the Abrikosov-Nielsen-Olesen BPS cosmic strings produced at the end of original D3/D7 inflation lead to an additional contribution to the CMB anisotropy. To make this contribution consistent with the WMAP results one needs an extremely small gauge coupling in the effective D-term inflation model. Such couplings may be difficult to justify in string theory. Here we develop a generalized version of the D3/D7 brane model, which leads to semilocal strings, instead of the topologically stable ANO cosmic strings. We show that the semilocal strings have unbroken supersymmetry when embedded into supergravity with FI terms. The energy of these strings is independent of their thickness. We confirm the existing arguments that strings of such type disappear soon after their formation and do not pose any cosmological problems, for any value of the gauge coupling. This should simplify the task of constructing fully realistic models of D3/D7 inflation.

Paper Structure

This paper contains 18 sections, 88 equations, 1 figure.

Table of Contents

  1. Introduction
  2. The $D3/D7$ model, P-term model and the volume modulus
  3. The D7 action
  4. The D3 and stretched strings
  5. P-term action
  6. Comparing the actions
  7. Generalized $D3/D7$ model with additional global or local symmetries
  8. Global symmetry from two $D7$ branes
  9. Enhancement of local symmetries
  10. Analysis of the warp factor
  11. Semilocal BPS-strings in supergravity
  12. The Lagrangian
  13. Semilocal vortices with unbroken supersymmetry
  14. Limiting cases
  15. Cosmology and semilocal strings
  16. ...and 3 more sections

Figures (1)

  • Figure 1: The hypermultiplets from two $D3$ branes and one $D7$ brane.