370 research outputs found
Kappa symmetric OSp(2|2) WZNW model
We construct a kappa symmetric WZNW model for the OSp(2|2) supergroup, whose
bosonic part is AdS3xS1 space. The field equation gives the chiral current
conservation and the right/left factorization is shown after the kappa symmetry
is fixed. The right-moving modes contain both bosons and fermions while the
left-moving modes contain only bosons.Comment: 18 pages; reference and comments added, version to appear in JHE
On factorizations in perturbative quantum gravity
Some features of Einstein gravity are most easily understood from string
theory but are not manifest at the level of the usual Lagrangian formulation.
One example is the factorization of gravity amplitudes into gauge theory
amplitudes. Based on the recently constructed `double field theory' and a
geometrical frame-like formalism developed by Siegel, we provide a framework of
perturbative Einstein gravity coupled to a 2-form and a dilaton in which, as a
consequence of T-duality, the Feynman rules factorize to all orders in
perturbation theory. We thereby establish the precise relation between the
field variables in different formulations and discuss the Lagrangian that, when
written in terms of these variables, makes a left-right factorization manifest.Comment: 18 pages, v2: reference added, to appear in JHE
String solitons in the M5-brane worldvolume with a Nambu-Poisson structure and Seiberg-Witten map
We analyze BPS equations for string-like configurations derived from the
M5-brane worldvolume action with a Nambu-Poisson structure constructed in
arXiv:0804.3629, arXiv:0805.2898. We solve the BPS equations up to the first
order in the parameter which characterizes the strength of the
Nambu-Poisson bracket. We compare our solutions to previously constructed BPS
string solitons in the conventional description of M5-brane in a constant
three-form background via Seiberg-Witten map, and find agreement.Comment: v2: minor corrections, the title slightly changed. 10 pages. v3: some
clarifying comment
Boundary states in the Nappi-Witten model
We investigate D-branes in the Nappi-Witten model. Classically symmetric
D-branes are classified by the (twisted) conjugacy classes of the Nappi-Witten
group, which specify the geometry of the corresponding D-branes. Quantum
description of the D-branes is given by boundary states, and we need one point
functions of closed strings to construct the boundary states. We compute the
one point functions solving conformal bootstrap constraints, and check that the
classical limit of the boundary states reproduces the geometry of D-branes.Comment: 19 pages, no figure; minor changes, references adde
Closed String Tachyon Condensation on Twisted Circles
We study IIA/B string theory compactified on twisted circles. These models
possess closed string tachyons and reduce to type 0B/A theory in a special
limit. Using methods of gauged linear sigma models and mirror symmetry we
construct a conformal field theory which interpolates between these models and
flat space via an auxiliary Liouville direction. Interpreting motion in the
Liouville direction as renormalization group flow, we argue that the end point
of tachyon condensation in all these models (including 0B/A theory) is
supersymmetric type II theory. We also find a zero-slope limit of these models
which is best described in a T-dual picture as a type II NS-NS fluxbrane. In
this limit tachyon condensation is an interesting and well posed problem in
supergravity. We explicitly determine the tachyon as a fluctuation of
supergravity fields, and perform a rudimentary numerical analysis of the
relevant flows.Comment: 21 pages plus appendices (12 pages), harvmac, 1 fig, v2: minor
changes and references added, v3: minor changes version published in JHE
BPS Solitons in M5-Brane Worldvolume Theory with Constant Three-Form Field
We study BPS solutions for a self-dual string and a neutral string in
M5-brane worldvolume theory with constant three-form field. We further
generalize such solitons to superpose with a calibrated surface. We also study
a traveling wave on a calibrated surface in the constant three-form field
background.Comment: 12 pages, LaTeX, minor correction, added referenc
AdS and pp-wave D-particle superalgebras
We derive anticommutators of supercharges with a brane charge for a
D-particle in AdS(2) x S(2) and pp-wave backgrounds. A coset GL(2|2)/(GL(1))^4
and its Penrose limit are used with the supermatrix-valued coordinates for the
AdS and the pp-wave spaces respectively. The brane charges have position
dependence, and can be absorbed into bosonic generators by shift of momenta
which results in closure of the superalgebras.Comment: 15 page
Superstring Vacua of 4-dimensional PP-Waves with Enhanced Supersymmetry
We study the superstring vacua constructed from the conformal field theories
of the type H_4 x M, where H_4 denotes the super Nappi-Witten model (super WZW
model on the 4-dimensional Heisenberg group H_4) and M denotes an arbitrary N=2
rational superconformal field theory with c=9. We define (type II) superstring
vacua with 8 supercharges, which are twice as many as those on the backgrounds
of H_4 x CY_3. We explicitly construct as physical vertices the space-time SUSY
algebra that is a natural extension of H_4 Lie algebra. The spectrum of
physical states is classified into two sectors: (1) strings freely propagating
along the transverse plane of pp-wave geometry and possessing the integral
U(1)_R-charges in M sector, and (2) strings that do not freely propagate along
the transverse plane and possess the fractional U(1)_R-charges in M. The former
behaves like the string excitations in the usual Calabi-Yau compactification,
but the latter defines new sectors without changing the physics in ``bulk''
space. We also analyze the thermal partition functions of these systems,
emphasizing the similarity to the DLCQ string theory. As a byproduct we prove
the supersymmetric cancellation of conformal blocks in an arbitrary unitary N=2
SCFT of c=12 with the suitable GSO projection.Comment: 37 pages, no figures, v2: typo corrected, references added, v3: minor
change
Comments on D-brane Interactions in PP-wave Backgrounds
We calculate the interaction potential between widely separated D-branes in
PP-wave backgrounds in string theory as well as in low-energy supergravity.
Timelike and spacelike orientations are qualitatively different but in both
cases the effective brane tensions and RR charges take the same values as in
Minkowski space in accordance with the expectations from the sigma model
perturbation theory.Comment: Latex, 22 pages. Typos corrected and a reference added, final versio
Closed-String Tachyons and the Hagedorn Transition in AdS Space
We discuss some aspects of the behaviour of a string gas at the Hagedorn
temperature from a Euclidean point of view. Using AdS space as an infrared
regulator, the Hagedorn tachyon can be effectively quasi-localized and its
dynamics controled by a finite energetic balance. We propose that the off-shell
RG flow matches to an Euclidean AdS black hole geometry in a generalization of
the string/black-hole correspondence principle. The final stage of the RG flow
can be interpreted semiclassically as the growth of a cool black hole in a
hotter radiation bath. The end-point of the condensation is the large Euclidean
AdS black hole, and the part of spacetime behind the horizon has been removed.
In the flat-space limit, holography is manifest by the system creating its own
transverse screen at infinity. This leads to an argument, based on the
energetics of the system, explaining why the non-supersymmetric type 0A string
theory decays into the supersymmetric type IIB vacuum. We also suggest a notion
of `boundary entropy', the value of which decreases along the line of flow.Comment: 24 pages, Harvmac. 2 Figures. Typos corrected and reference adde
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