Non-supersymmetric string theory

Abstract

A class of non-supersymmetric string backgrounds can be constructed using twists that involve space-time fermion parity. We propose a non-perturbative definition of string theory in these backgrounds via gauge theories with supersymmetry softly broken by twisted boundary conditions. The perturbative string spectrum is reproduced, and qualitative effects of the interactions are discussed. Along the way, we find an interesting mechanism for inflation. The end state of closed string tachyon condensation is a highly excited state in the gauge theory which, in all likelihood, does not have a geometric interpretation.

Matrix Models Techniques and 2d Causal Quantum Gravity

“…Accordingly, the partition function of 2D gravity can be expressed as the free energy of a hermitian matrix model. The important fact about this connection is that it agrees with the results obtained in Liouville gravity [50,51,52]. There is also the possibility to take into account topology change in the theory (see [53] for a detailed analysis of topology change).…”

“…Furthermore, we showed how to encounter the Painlevé differential equation in the double scaling limit and by this means obtaining an agreement between continuum and discrete approaches regarding the topological expansion. A open problem consists in finding a rigorous proof of the equivalence of continuum and discrete approaches, although there is evidence to believe they are perfectly compatible [52,86]. An important next step would be the study of the continuum matrix model of CDT (see [39]).…”