898 research outputs found

### Oriented Open-Closed String Theory Revisited

String theory on D-brane backgrounds is open-closed string theory. Given the
relevance of this fact, we give details and elaborate upon our earlier
construction of oriented open-closed string field theory. In order to
incorporate explicitly closed strings, the classical sector of this theory is
open strings with a homotopy associative A_\infty algebraic structure. We build
a suitable Batalin-Vilkovisky algebra on moduli spaces of bordered Riemann
surfaces, the construction of which involves a few subtleties arising from the
open string punctures and cyclicity conditions. All vertices coupling open and
closed strings through disks are described explicitly. Subalgebras of the
algebra of surfaces with boundaries are used to discuss symmetries of classical
open string theory induced by the closed string sector, and to write classical
open string field theory on general closed string backgrounds. We give a
preliminary analysis of the ghost-dilaton theorem.Comment: 61 pages, 19 eps figures, phyzzx, BoxedEP

### Building string field theory around non-conformal backgrounds

The main limitations of string field theory arise because its present
formulation requires a background representing a classical solution, a
background defined by a strictly conformally invariant theory. Here we sketch a
construction for a gauge-invariant string field action around non-conformal
backgrounds. The construction makes no reference to any conformal theory. Its
two-dimensional field-theoretic aspect is based on a generalized BRST operator
satisfying a set of Weyl descent equations. Its geometric aspect uses a complex
of moduli spaces of two-dimensional Riemannian manifolds having ordinary
punctures, and organized by the number of special punctures which goes from
zero to infinity. In this complex there is a Batalin-Vilkovisky algebra that
includes naturally the operator which adds one special puncture. We obtain a
classical field equation that appears to relax the condition of conformal
invariance usually taken to define classical string backgrounds.Comment: 38 pages, 4 figures, phyzzx and BoxedEPS include

### Double Field Theory, T-Duality, and Courant Brackets

These lecture notes are based on three lectures, each ninety minutes long,
given by the author at the "International School on Strings and Fundamental
Physics" which took place in Garching/Munich from July 25 to August 6, 2010.
These lectures, aimed at graduate students, require only a basic knowledge of
string theory and give a simple introduction to double field theory. These
notes were prepared by Marco Baumgartl and Nicolas Moeller.Comment: 25 page

### Interpolating String Field Theories

A minimal area problem imposing different length conditions on open and
closed curves is shown to define a one parameter family of covariant
open-closed quantum string field theories. These interpolate from a recently
proposed factorizable open-closed theory up to an extended version of Witten's
open string field theory capable of incorporating on shell closed strings. The
string diagrams of the latter define a new decomposition of the moduli spaces
of Riemann surfaces with punctures and boundaries based on quadratic
differentials with both first order and second order poles.Comment: 12 pages, 7 figures (not included

### A Solvable Toy Model for Tachyon Condensation in String Field Theory

The lump solution of \phi^3 field theory provides a toy model for unstable
D-branes of bosonic string theory. The field theory living on this lump is
itself a cubic field theory involving a tachyon, two additional scalar fields,
and a scalar field continuum. Its action can be written explicitly because the
fluctuation spectrum of the lump turns out to be governed by a solvable
Schroedinger equation; the \ell=3 case of a series of reflectionless
potentials. We study the multiscalar tachyon potential both exactly and in the
level expansion, obtaining insight into issues of convergence, branches of the
solution space, and the mechanism for removal of states after condensation. In
particular we find an interpretation for the puzzling finite domain of
definition of string field marginal parameters.Comment: 27 pages, 6 figures, LaTeX. Added references to reflectionless
potentials, minor typos correcte

### Effective Tachyonic Potential in Closed String Field Theory

We calculate the effective tachyonic potential in closed string field theory
up to the quartic term in the tree approximation. This involves an elementary
four-tachyon vertex and a sum over the infinite number of Feynman graphs with
an intermediate massive state. We show that both the elementary term and the
sum can be evaluated as integrals of some measure over different regions in the
moduli space of four-punctured spheres. We show that both elementary and
effective coupling give negative contributions to the quartic term in the
tachyon potential. Numerical calculations show that the fourth order term is
big enough to destroy a local minimum which exists in the third order
approximation.Comment: 41 pages, LaTeX + psfig macro package, 15 uuencoded tar-compressed
postscript figures include

### A Note on Gauge Transformations in Batalin-Vilkovisky Theory

We give a generally covariant description, in the sense of symplectic
geometry, of gauge transformations in Batalin-Vilkovisky quantization. Gauge
transformations exist not only at the classical level, but also at the quantum
level, where they leave the action-weighted measure $d\mu_S = d\mu
e^{2S/\hbar}$ invariant. The quantum gauge transformations and their Lie
algebra are $\hbar$-deformations of the classical gauge transformation and
their Lie algebra. The corresponding Lie brackets $[ , ]^q$, and $[ , ]^c$, are
constructed in terms of the symplectic structure and the measure $d\mu_S$. We
discuss closed string field theory as an application.Comment: 10 pages, phyzzx.tex, MIT-CTP-224

### Non-perturbative de Sitter vacua via $\alpha'$ corrections

The higher-derivative $\alpha'$ corrections consistent with $O(d,d)$ duality
invariance can be completely classified for cosmological, purely time-dependent
backgrounds. This result is used to show that there are duality invariant
theories featuring string-frame de Sitter vacua as solutions that are
non-perturbative in $\alpha'$, thus suggesting that classical string theory may
realize de Sitter solutions in an unexpected fashion.Comment: 7 pages, Second Prize Essay for the Gravity Research Foundation 2019
Awards for Essays on Gravitatio

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