38 research outputs found
Type IIB tensionless superstrings in a pp-wave background
We solve the tensionless string in a constant plane wave background and
obtain a hugely degenerate spectrum. This is the case for a large class of
plane wave backgrounds. We show that the solution can also be derived as a
consistent limit of the quantized tensile theory of IIB strings in a pp-wave.
This is in contrast to the situation for several other backgrounds.Comment: 1+17 pages, LaTeX, minor corrections, added new reference
Spherically Symmetric and Rotating Wormholes Produced by Lightlike Branes
Lightlike p-branes (LL-branes) with dynamical (variable) tension allow simple
and elegant Polyakov-type and dual to it Nambu-Goto-like world-volume action
formulations. Here we first briefly describe the dynamics of LL-branes as test
objects in various physically interesting gravitational backgrounds of black
hole type, including rotating ones. Next we show that LL-branes are the
appropriate gravitational sources that provide proper matter energy momentum
tensors in the Einstein equations of motion needed to generate traversable
wormhole solutions, in particular, self-consistent cylindrical rotating
wormholes, with the LL-branes occupying their throats. Here a major role is
being played by the dynamical LL-brane tension which turns out to be negative
but may be of arbitrary small magnitude. As a particular solution we obtain
traversable wormhole with Schwarzschild geometry generated by a LL-brane
positioned at the wormhole throat, which represents the correct consistent
realization of the original Einstein-Rosen "bridge" manifold.Comment: 27 pages; important clarifications regarding the meaning of the
original Einstein-Rosen "bridge" construction; an important addition to the
Appendix; acknowledgments adde
Hiding and Confining Charges via "Tube-like" Wormholes
We describe two interesting effects in wormhole physics. First, we find that
a genuinely charged matter source may appear neutral to an external observer -
a phenomenon opposite to the famous Misner-Wheeler "charge without charge"
effect. This phenomenon takes place when coupling a bulk
gravity/nonlinear-gauge-field system to a charged lightlike brane as a matter
source. The "charge-hiding" effect occurs in a wormhole solution which connects
a non-compact "universe", comprising the exterior region of
Schwarzschild-(anti-)de-Sitter (SdS) or purely Schwarzschild black hole beyond
the Schwarzschild horizon, to a Levi-Civita-Bertotti-Robinson-type (LCBR)
"tube-like" "universe" via a wormhole "throat" occupied by the brane. In this
solution the whole electric flux produced by the brane is expelled into the
"tube-like" "universe" and the brane is detected as neutral by an observer in
the non-compact "universe". Next, we find a truly charge-confining wormhole
solution when we couple the bulk gravity/nonlinear-gauge-field system to two
oppositely charged lightlike branes. The latter system possesses a "two-throat"
wormhole solution, where the "left-most" and the "right-most" "universes" are
two identical copies of the exterior region of SdS black hole beyond the
Schwarzschild horizon, whereas the "middle" "universe" is of LCBR "tube-like"
form with geometry dS_2 x S^2. It comprises the finite-extent intermediate
region of dS_2 between its two horizons. Both "throats" are occupied by the two
oppositely charged lightlike branes and the whole electric flux produced by the
latter is confined entirely within the middle "tube-like" "universe". A crucial
ingredient is the special form of the nonlinear gauge field action, which
contains both the standard Maxwell term as well as a square root of the latter.
This theory was previously shown to produce a QCD-like confining dynamics in
flat space-time.Comment: 26 pages, 2 figures; v.2 several references added, missing constant
factors in few equations inserted, acknowledgement added, results unchanged;
v.3 28 pages, several clarifying remarks, references and acknowledgements
added, version to appear in International Journal of Modern Physics
Logarithmic intertwining operators and vertex operators
This is the first in a series of papers where we study logarithmic
intertwining operators for various vertex subalgebras of Heisenberg vertex
operator algebras. In this paper we examine logarithmic intertwining operators
associated with rank one Heisenberg vertex operator algebra , of
central charge . We classify these operators in terms of {\em depth}
and provide explicit constructions in all cases. Furthermore, for we
focus on the vertex operator subalgebra L(1,0) of and obtain
logarithmic intertwining operators among indecomposable Virasoro algebra
modules. In particular, we construct explicitly a family of {\em hidden}
logarithmic intertwining operators, i.e., those that operate among two ordinary
and one genuine logarithmic L(1,0)-module.Comment: 32 pages. To appear in CM
SL(2,Z) tensionless string backgrounds in IIB string theory
We examine a tensionless limit of a SL(2,Z) set of background solutions to
IIB supergravity theory, obtained by performing an infinite boost. This yields
a solution that corresponds to taking the original string tension to zero. The
limit reproduces ordinary Minkowski space except for a delta-like singularity
along the string. We study the field content and the energy momentum tensor.Comment: 1+8 pages, LaTeX, JHEP styl
Worldsheet Instantons and a Null String Limit of Born-Infeld Theory
For a superstring theory in four spacetime dimensions, we propose a
modification of the Born-Infeld action that possesses a well-defined
tensionless limit. We interpret this as describing the effective target space
dynamics of null strings on a D3-brane. We argue that such a modification can
be induced by nonperturbative contributions from instantons in the worldsheet
sigma-model describing string propagation on the brane.Comment: 11 pages; Comments and references adde
Higher Spin Symmetry and N=4 SYM
We assemble the spectrum of single-trace operators in free N=4 SU(N) SYM
theory into irreducible representations of the Higher Spin symmetry algebra
hs(2,2|4). Higher Spin representations or YT-pletons are associated to Young
tableaux (YT) corresponding to representations of the symmetric group
compatible with the cyclicity of color traces. After turning on interactions,
YT-pletons decompose into infinite towers of representations of the
superconformal algebra PSU(2,2|4) and anomalous dimensions are generated. We
work out the decompositions of tripletons with respect to the N=4
superconformal algebra PSU(2,2|4) and compute their one anomalous dimensions at
large N. We then focus on operators/states sitting in semishort superconformal
multiplets. By passing them through a semishort-sieve that removes
superdescendants, we derive compact expressions for the partition function of
semishort primaries.Comment: 38 pages, no figures. v2: references adde
Minimal Superstrings and Loop Gas Models
We reformulate the matrix models of minimal superstrings as loop gas models
on random surfaces. In the continuum limit, this leads to the identification of
minimal superstrings with certain bosonic string theories, to all orders in the
genus expansion. RR vertex operators arise as operators in a Z_2 twisted sector
of the matter CFT. We show how the loop gas model implements the sum over spin
structures expected from the continuum RNS formulation. Open string boundary
conditions are also more transparent in this language.Comment: 36 pages, 3 figure
Chiral de Rham complex on Riemannian manifolds and special holonomy
Interpreting the chiral de Rham complex (CDR) as a formal Hamiltonian
quantization of the supersymmetric non-linear sigma model, we suggest a setup
for the study of CDR on manifolds with special holonomy. We show how to
systematically construct global sections of CDR from differential forms, and
investigate the algebra of the sections corresponding to the covariantly
constant forms associated with the special holonomy. As a concrete example, we
construct two commuting copies of the Odake algebra (an extension of the N=2
superconformal algebra) on the space of global sections of CDR of a Calabi-Yau
threefold and conjecture similar results for G_2 manifolds. We also discuss
quasi-classical limits of these algebras.Comment: 49 pages, title changed, major rewrite with no changes in the main
theorems, published versio