Double field theory describes a massless subsector of closed string theory with both momentum and winding excitations. The gauge algebra is governed by the Courant bracket in certain subsectors of this double field theory. We construct the associated nonlinear background-independent action that is T-duality invariant and realizes the Courant gauge algebra. The action is the sum of a standard action for gravity, antisymmetric tensor, and dilaton fields written with ordinary derivatives, a similar action for dual fields with dual derivatives, and a mixed term that is needed for gauge invariance.

http://dspace.mit.edu/openaccess-disseminate/1721.1/63176

Background independent action for double field theory

New regular black hole solution from nonlinear electrodynamics

We review and elaborate on some aspects of Born-Infeld action and its supersymmetric generalizations in connection with string theory. Contents: BI action from string theory; some properties of bosonic D=4 BI action; N=1 and N=2 supersymmetric BI actions with manifest linear D=4 supersymmetry; four-derivative terms in N=4 supersymmetric BI action; BI actions with `deformed' supersymmetry from D-brane actions; non-abelian generalization of BI action; derivative corrections to BI action in open superstring theory.

Born-Infeld action, supersymmetry and string theory

We study both bosonic and supersymmetric (p,q) minimal models coupled to Liouville theory using the ground ring and the various branes of the theory. From the FZZT brane partition function, there emerges a unified, geometric description of all these theories in terms of an auxiliary Riemann surface p,q and the corresponding matrix model. In terms of this geometric description, both the FZZT and ZZ branes correspond to line integrals of a certain one-form on p,q. Moreover, we argue that there are a finite number of distinct (m,n) ZZ branes, and we show that these ZZ branes are located at the singularities of p,q. Finally, we discuss the possibility that the bosonic and supersymmetric theories with (p,q) odd and relatively prime are identical, as is suggested by the unified treatment of these models.

Branes, rings and matrix models in minimal (super)string theory

Motivated by the apparent dependence of string σ models on the sum of spacetime metric and antisymmetric tensor fields, we reconsider gravity theories constructed from a nonsymmetric metric. We first show, by expanding in powers of the antisymmetric field, that all such ‘‘geometrical’’ theories homogeneous in second derivatives violate standard physical requirements: ghost freedom, absence of algebraic inconsistencies, or continuity of degree-of-freedom content. This no-go result applies in particular to the old unified theory of Einstein and its recent avatars. However, we find that the addition of nonderivative, ‘‘cosmological’’ terms formally restores consistency by giving a mass to the antisymmetric tensor field, thereby transmuting it into a fifth-force-like massive vector but with novel possible matter couplings. The resulting macroscopic models also exhibit ‘‘van der Waals’’–type gravitational effects, and may provide useful phenomenological foils to general relativity.

/pdf/nonsymmetric-gravity-theories-inconsistencies-and-a-cure-58cjhojwlx.pdf

Nonsymmetric gravity theories: Inconsistencies and a cure.

We present some consequences of non-anomalous propagation requirements on various massless fields. Among the models of nonlinear electrodynamics we show that only the Maxwell and Born-Infeld models also obey duality invariance. Separately we show that, for actions depending only on the invariant, the permitted models have . We also characterize acceptable vector-scalar systems. Finally, we find that wide classes of gravity models share with the Einstein model the null nature of their characteristic surfaces.

`Good propagation' and duality invariance constraints on scalar, gauge vector and gravity actions

Dimensional reduction of the Seiberg--Witten equations leads to the equations of motion of a U(1) Chern--Simons theory coupled to a massless spinorial field. A topological quantum field theory is constructed for the moduli space of gauge equivalence classes of solutions of these equations. The Euler characteristic of the moduli space is obtained as the partition function which yields an analogue of Casson's invariant.A mathematically rigorous definition of the invariant isdeveloped for homology spheres using the theory of spectral flow ofself-adjoint Fredholm operators.

/pdf/seiberg-witten-monopoles-in-three-dimensions-5e8elpdlr1.pdf

Seiberg--Witten Monopoles in Three Dimensions

We present some consequences of non-anomalous propagation requirements on various massless fields. Among the models of nonlinear electrodynamics we show that only Maxwell and Born-Infeld also obey duality invariance. Separately we show that, for actions depending only on the $F_\mn^2$ invariant, the permitted models have $L \sim \sqrt{1 + F^2}$. We also characterize acceptable vector-scalar systems. Finally we find that wide classes of gravity models share with Einstein the null nature of their characteristic surfaces.

``Good Propagation'' Constraints on Dual Invariant Actions in Electrodynamics and on Massless Fields

We discuss the BSRT quantization of 2D $N=1$ supergravity coupled to superconformal matter with $\hat{c} \leq 1$ in the conformal gauge. The physical states are computed as BRST cohomology. In particular, we consider the ring structure and associated symmetry algebra for the 2D superstring ($\hat{c} = 1$).

J. McCarthy

Papers

Nonsymmetric gravity theories: Inconsistencies and a cure.

`Good propagation' and duality invariance constraints on scalar, gauge vector and gravity actions

Seiberg--Witten Monopoles in Three Dimensions

``Good Propagation'' Constraints on Dual Invariant Actions in Electrodynamics and on Massless Fields

Ground ring for the 2D NSR string