A new world sheet field theory

World-Sheet Formulation of M Theory

We first review the interpretation of world-sheet defects as D branes described by a critical theory in 11 dimensions, that we interpret asM theory. We then show thatD-brane recoil induces dynamically an anti-de-Sitter (AdS) space-time background, with criticality restored by a twelfth time-like dimension described by a Liouville field. Local physics in the bulk of this AdS11 may be described b...

Quantum Field Theory Example Sheet , Michælmas

String Theory and the CPT Theorem on the World-Sheet

We study the CPT theorem for a two-dimensional conformal field theory on an arbitrary Riemann surface. On the sphere the theorem follows from the assumption that the correlation functions have standard hermiticity properties and are invariant under the transformation z → 1/z. The theorem can then be extended to higher genus surfaces by sewing. We show that, as a consequence of the CPT theorem o...

Old World Econometrics and New World Theory

This paper summarizes recent work on the econometrics of identification in rational expectations models by myself and Andreas Beyer. In this work, we discuss the relationship between structure and reduced form in linear rational expectations models and we apply our analysis to a class of new Keynesian models that are frequently used to inform the policy debate. We argue that the identifying ass...

Twisted World-Sheet Gravities

This is the first in a series of papers in which I investigate the orbifolds of permutation-type as candidates for new physical string systems at multiples of critical closed-string central charges. Examples include the bosonic orientation orbifolds, the bosonic permutation orbifolds and others, as well as superstring extensions. In this paper I use the extended (twisted) Virasoro algebras of t...