The Super-Stückelberg procedure and dS in pure supergravity.

Understanding de Sitter space in supergravity-and string theory-has led to an intense amount of work for more than two decades, largely motivated by the discovery of the accelerated expansion of the Universe in 1998. In this paper, we consider a non-trivial generalization of unimodular gravity to minimal N = 1 supergravity, which allows for de Sitter solutions without the need of introducing any matter. We formulate a superspace version of the Stückelberg procedure, which restores diffeomorphism and local supersymmetry invariance. This introduces the goldstino associated with spontaneous breaking of supersymmetry in a natural way. The cosmological constant and gravitino mass are related to the vacuum expectation value of the components of a Lagrange multiplier imposing a super-unimodularity condition.

Effect of extra dimensions on gravitational waves from cosmic strings.

We show how the motion of cosmic superstrings in extra dimensions can modify the gravitational wave signal from cusps. Additional dimensions both round off cusps, as well as reducing the probability of their formation, and thus give a significant dimension dependent damping of the gravitational waves. We look at the implication of this effect for LIGO and LISA, as well as commenting on more general frequency bands.