[Paper Review] Brane World Susy Breaking

Alexey Anisimov, Michael Dine+2 more|arXiv (Cornell University)|Nov 26, 2001

Black Holes and Theoretical Physics4 citations

TL;DR

This paper demonstrates that in brane world models of supersymmetry breaking, the Kahler potential does not take the sequestered no-scale form due to bulk supergravity exchange and geometric warping, leading to tree-level non-universal squark and slepton masses. Contrary to expectations, this results in significant flavor-violating contributions, undermining the viability of anomaly-mediated supersymmetry breaking as a generic solution to the flavor problem.

ABSTRACT

In brane world models of nature, supersymmetry breaking is often isolated on a distant brane in a higher dimensional space. The form of the Kahler potential in generic string and M-theory brane world backgrounds is shown to give rise to tree-level non-universal squark and slepton masses. This results from the exchange of bulk supergravity fields and warping of the internal geometry. This is contrary to the notion that bulk locality gives rise to a sequestered no-scale form of the Kahler potential with vanishing tree-level masses and solves the supersymmetric flavor problem. As a result, a radiatively generated anomaly mediated superpartner spectrum is not a generic outcome of these theories.

Motivation & Objective

• To investigate whether brane world supersymmetry breaking (BWSB) models generically yield a sequestered no-scale Kahler potential that suppresses tree-level scalar masses.
• To determine the origin of non-universal soft masses in BWSB scenarios within string/M-theory backgrounds.
• To assess whether the standard assumption of anomaly-mediated spectra is valid in generic BWSB models.
• To evaluate the role of bulk supergravity exchange and geometric warping in generating tree-level scalar masses.
• To challenge the prevailing notion that physical separation of branes alone ensures flavor protection in supersymmetric models.

Proposed method

• Analyzes the four-dimensional effective Kahler potential derived from higher-dimensional supergravity actions in Type I′, Type IIB, and heterotic M-theory compactifications.
• Applies macroscopic supergravity techniques to derive the leading form of the Kahler potential in BWSB backgrounds with separated visible and hidden sector branes.
• Identifies that non-derivative brane-brane couplings arise from exchange of bulk supergravity multiplets, breaking the sequestered structure.
• Evaluates corrections due to warping of the internal geometry, showing that non-uniform zero-mode wave functions on Calabi-Yau manifolds break universality.
• Uses the supergravity frame formalism, relating the Kahler potential to the function f in the supergravity action, and computes f_{i\bar{j}} to detect off-diagonal couplings.
• Considers the role of moduli stabilization and flux compactifications in potentially preserving or breaking the no-scale form.

Experimental results

Research questions

• RQ1 Does the separation of visible and hidden sectors on distant branes in a higher-dimensional space lead to a sequestered no-scale Kahler potential with vanishing tree-level scalar masses?
• RQ2 What is the microscopic origin of tree-level non-universal scalar masses in brane world models of supersymmetry breaking?
• RQ3 How do bulk supergravity exchanges and geometric warping affect the universality of squark and slepton masses in BWSB scenarios?
• RQ4 To what extent do corrections from warped compactifications invalidate the assumption of anomaly-mediated spectra in generic BWSB models?
• RQ5 Under what conditions might the no-scale form of the Kahler potential still emerge in BWSB backgrounds?

Key findings

• The Kahler potential in generic string and M-theory brane world backgrounds is not of the sequestered no-scale form, contrary to prior assumptions.
• Tree-level scalar masses for squarks and sleptons are generated and are of order the four-dimensional gravitino mass, breaking universality.
• These non-universal masses arise from the exchange of bulk supergravity fields between separated branes.
• Geometric warping of the internal compact space further induces non-universal corrections to the scalar masses through T-dependent kinetic terms.
• The corrections from warping are not necessarily small, especially in strongly coupled limits such as Horava-Witten theory, and can be substantial (e.g., ε ~ 1/3).
• The results imply that anomaly-mediated spectra are not a generic outcome of BWSB models, and the flavor problem remains unsolved without additional assumptions.