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Soft branes in supersymmetry-breaking backgrounds

Paul McGuirk, Gary Shiu, Fang Ye

TL;DR

The paper argues that non-supersymmetric perturbations to GKP-type flux compactifications, especially the backreaction of a small number of $\ar{D}3$-branes, induce soft supersymmetry breaking in the low-energy EFT on D3-branes. By computing both bosonic and fermionic open-string actions to leading order in the string length $\ell_s$, the authors show that marginal operators are controlled by the perturbed internal metric and fluxes, allowing a field-redefinition to cast the theory in a softly broken ($\mathcal{N}_{4}=1$) form; this supports the view that SUSY breaking may be spontaneous rather than explicit. They identify a goldstino candidate on the anti-brane and connect the soft-breaking structure to Akulov-Volkov dynamics, suggesting a consistent non-linear realization of SUSY and a potential super-Higgs mechanism in these backgrounds. The results have implications for understanding KKLT-type constructions and the nature of SUSY breaking in warped flux geometries, while highlighting open questions about higher-order terms and global realizability of the non-linear symmetry.

Abstract

We revisit the analysis of effective field theories resulting from non-supersymmetric perturbations to supersymmetric flux compactifications of the type-IIB superstring with an eye towards those resulting from the backreaction of a small number of anti-D3-branes. Independently of the background, we show that the low-energy Lagrangian describing the fluctuations of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite perturbations to marginal operators that were not fully considered in some previous treatments. We take this as an indication that the breaking of supersymmetry by anti-D3-branes or other sources may be spontaneous rather than explicit. In support of this, we consider the action of an anti-D3-brane probing an otherwise supersymmetric configuration and identify a candidate for the corresponding goldstino.

Soft branes in supersymmetry-breaking backgrounds

TL;DR

The paper argues that non-supersymmetric perturbations to GKP-type flux compactifications, especially the backreaction of a small number of -branes, induce soft supersymmetry breaking in the low-energy EFT on D3-branes. By computing both bosonic and fermionic open-string actions to leading order in the string length , the authors show that marginal operators are controlled by the perturbed internal metric and fluxes, allowing a field-redefinition to cast the theory in a softly broken () form; this supports the view that SUSY breaking may be spontaneous rather than explicit. They identify a goldstino candidate on the anti-brane and connect the soft-breaking structure to Akulov-Volkov dynamics, suggesting a consistent non-linear realization of SUSY and a potential super-Higgs mechanism in these backgrounds. The results have implications for understanding KKLT-type constructions and the nature of SUSY breaking in warped flux geometries, while highlighting open questions about higher-order terms and global realizability of the non-linear symmetry.

Abstract

We revisit the analysis of effective field theories resulting from non-supersymmetric perturbations to supersymmetric flux compactifications of the type-IIB superstring with an eye towards those resulting from the backreaction of a small number of anti-D3-branes. Independently of the background, we show that the low-energy Lagrangian describing the fluctuations of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite perturbations to marginal operators that were not fully considered in some previous treatments. We take this as an indication that the breaking of supersymmetry by anti-D3-branes or other sources may be spontaneous rather than explicit. In support of this, we consider the action of an anti-D3-brane probing an otherwise supersymmetric configuration and identify a candidate for the corresponding goldstino.

Paper Structure

This paper contains 11 sections, 160 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Non-supersymmetric perturbations to GKP compactifications
  3. Effective action for D3s
  4. Bosonic action
  5. Fermionic action
  6. Abelian case
  7. Non-Abelian case
  8. The soft Lagrangian
  9. An anti-brane goldstino
  10. Discussion and concluding remarks
  11. Conventions

Figures (1)

  • Figure 1: A Feynman diagram demonstrating hard breaking of supersymmetry. Integration over the internal momentum gives rise to quadratic dependence on the UV regulator. However, if $\varphi^{i}$ is not a gauge singlet, then gauge invariance forces this diagram to vanish. Note that the holomorphic $a$-terms do not give rise to such hard breaking since kinetic terms, schematically represented by the insertion in the loop, do not mix holomorphic with holomorphic fields.