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The O(dd) story of massive supergravity
The low energy effective action describing the standard Kaluza-Klein reduction of heterotic string theory on a d-torus possesses a manifest O(d,d+16) symmetry. We consider generalized Scherk-Schwarz
String Axiverse
String theory suggests the simultaneous presence of many ultralight axions, possibly populating each decade of mass down to the Hubble scale 10−33eV. Conversely the presence of such a plenitude of
Duality beyond the first loop
In this article we give a calculation of the two-loop {sigma}-model corrections to the T-duality map in string theory. We use the effective action approach, and analyze two-loop corrections in a
A natural framework for chaotic inflation.
It is shown that inflation with a quadratic potential occurs naturally in theories where an axionlike field mixes with a 4-form, and the axion can roll slowly towards its minimum, as in the simplest version of chaotic inflation.
Bent domain walls as brane worlds
We consider domain walls embedded in curved backgrounds as an approximation for braneworld scenarios. We give a large class of new exact solutions, exhausting the possibilities for describing one and
McVittie's Legacy: Black Holes in an Expanding Universe
We prove that a class of solutions to Einstein's equations---originally discovered by McVittie in 1933---includes regular black holes embedded in Friedmann-Robertson-Walker cosmologies. If the
An ignoble approach to large field inflation
We study an inflationary model developed by Kaloper and Sorbo, in which the inflaton is an axion with a sub-Planckian decay constant, whose potential is generated by mixing with a topological 4-form
Initial Conditions for Inflation
Free scalar fields in de Sitter space have a one-parameter family of states invariant under the de Sitter group, including the standard thermal vacuum. We show that, except for the thermal vacuum,
Signatures of short distance physics in the cosmic microwave background
We systematically investigate the effect of short distance physics on the spectrum of temperature anistropies in the Cosmic Microwave Background produced during inflation. We present a general