R symmetries in the landscape

Abstract

In the landscape, states with R symmetries at the classical level form a distinct branch, with a potentially interesting phenomenology. Some preliminary analyses suggested that the population of these states would be significantly suppressed. We survey orientifolds of IIB theories compactified on Calabi-Yau spaces based on vanishing polynomials in weighted projective spaces, and find that the suppression is quite substantial. On the other hand, we find that a Z 2 R-parity is a common feature in the landscape. We discuss whether the cosmological constant and proton decay or cosmology might select the low energy branch. We include also some remarks on split supersymmetry.

Supersymmetry breaking and the cosmological constant

“…Extra discrete symmetries are rare in the String Landscape [21], so one cannot justify the use of symmetry arguments to eliminate these terms, without proving that the probability distribution for meta-stable states is highly peaked on symmetric points. No such argument is known.…”

“…In the equations of specific SUGRA compactifications, the condition of discrete R symmetry has many fewer solutions than the equations D i W = 0 [21], essentially because most of the fluxes that give rise to the huge multiplicity of solutions, also break R symmetry. Furthermore, all known solutions of this type have moduli, at least the parameter that justifies the classical approximation.…”

The Nelson-Seiberg theorem revised

“…One may identify a discrete R-symmetry to one of the geometrical symmetries of the compact manifold when compactifying string theory from 10 to 4 dimensions. In the framework of flux compactifications, N X ≤ N Y can be easily arranged in many models with a low energy effective SUGRA description, producing a huge landscape of SUSY vacua with zero cosmological constants at tree level [21]. SUSY is then broken dynamically on these vacua through non-perturbative corrections to generate an exponentially small scale.…”

Symmetric points in the landscape as cosmological attractors

“…Such symmetries often arise at special points in the moduli spaces of critical string constructions. But in the framework of the flux landscape, discrete symmetries would seem to be rare [14]. The problem is that the vast number of states purported to exist within the landscape arise because of the existence of a large number of fluxes which can take a large number of values.…”