Mirror Mediation

TL;DR

The paper identifies a set of sufficient conditions—collectively called mirror mediation—under which gravity mediation yields flavour-universal, CP-preserving soft terms. It then shows how Type II string compactifications naturally realise these conditions: the hidden sector factorises into two moduli sectors (Kähler and complex structure), with Yukawas and gauge couplings controlled by complementary sectors and matter metrics that factorise accordingly. In concrete string constructions (notably GKP flux vacua and Large Volume scenarios), SUSY breaking is predominantly in the mirror sector, yielding a predictable pattern of soft terms with suppressed flavour/CP violation. The framework provides a robust bridge between moduli stabilisation, SUSY breaking, and MSSM flavour structure, while highlighting subleading corrections that could marginally affect universality at finite volume or with loops.

Abstract

I show that the effective action of string compactifications has a structure that can naturally solve the supersymmetric flavour and CP problems. At leading order in the g_s and α' expansions, the hidden sector factorises. The moduli space splits into two mirror parts that depend on Kahler and complex structure moduli. Holomorphy implies the flavour structure of the Yukawa couplings arises in only one part. In type IIA string theory flavour arises through the Kahler moduli sector and in type IIB flavour arises through the complex structure moduli sector. This factorisation gives a simple solution to the supersymmetric flavour and CP problems: flavour physics is generated in one sector while supersymmetry is broken in the mirror sector. This mechanism does not require the presence of gauge, gaugino or anomaly mediation and is explicitly realised by phenomenological models of IIB flux compactifications.