450 research outputs found
Field Redefinitions, T-duality and Solutions in Closed String Field Theories
We investigate classical solutions in closed bosonic string field theory and
heterotic string field theory that are obtained order by order starting from
solutions of the linearized equations of motion, and we discuss the ``field
redefinitions'' which relate massless fields in the string field theory side
and the low energy effective theory side. Massless components of the string
field theory solutions are not corrected and from them we can infer
corresponding solutions in the effective theory: the chiral null model and the
pp-wave solution with B-field, which have been known to be alpha'-exact. These
two sets of solutions in the two sides look slightly different because of the
field redefinitions. It turns out that T-duality is a useful tool to determine
them: We show that some part of the field redefinitions can be determined by
using the correspondence between T-duality rules in the two sides, irrespective
of the detail of the interaction terms and the integrating-out procedure.
Applying the field redefinitions, we see that the solutions in the effective
theory side are reproduced from the string field theory solutions.Comment: LaTeX, 40 pages, no figure v2: minor corrections v3: minor correctio
Chiral rings and GSO projection in Orbifolds
The GSO projection in the twisted sector of orbifold background is sometimes
subtle and incompatible descriptions are found in literatures. Here, from the
equivalence of partition functions in NSR and GS formalisms, we give a simple
rule of GSO projection for the chiral rings of string theory in \C^r/\Z_n,
. Necessary constructions of chiral rings are given by explicit mode
analysis.Comment: 24 page
(Twisted) Toroidal Compactification of pp-Waves
The maximally supersymmetric type IIB pp-wave is compactified on spatial
circles, with and without an auxiliary rotational twist. All spatial circles of
constant radius are identified. Without the twist, an S compactification
can preserve 24, 20 or 16 supercharges. compactifications can preserve
20, 18 or 16 supercharges; compactifications can preserve 18 or 16
supercharges and higher compactifications preserve 16 supercharges. The
worldsheet theory of this background is discussed. The T-dual and
decompactified type IIA and M-theoretic solutions which preserve 24
supercharges are given. Some comments are made regarding the AdS parent and the
CFT description.Comment: 22 pages REVTeX 4 and AMSLaTeX. v3: References and a paragraph on
nine dimensional Killing spinors were added. v4: A few typos corrected and a
footnote was modifie
Classical and Quantum Strings in compactified pp-waves and Godel type Universes
We consider Neveu-Schwarz pp-waves with spacetime supersymmetry. Upon
compactification of a spacelike direction, these backgrounds develop Closed
Null Curves (CNCs) and Closed Timelike Curves (CTCs), and are U-dual to
supersymmetric Godel type universes. We study classical and quantum strings in
this background, with emphasis on the strings winding around the compact
direction. We consider two types of strings: long strings stabilized by NS flux
and rotating strings which are stabilized against collapse by angular momentum.
Some of the latter strings wrap around CNCs and CTCs, and are thus a potential
source of pathology. We analyze the partition function, and in particular
discuss the effects of these string states. Although our results are not
conclusive, the partition function seems to be dramatically altered due to the
presence of CNCs and CTCs. We discuss some interpretations of our results,
including a possible sign of unitary violation.Comment: 42 pages, LaTeX, 2 figure
Closed String Tachyons and Semi-Classical Instabilities
We conjecture that the end point of bulk closed string tachyon decay at any
non-zero coupling, is the annihilation of space time by Witten's bubble of
nothing, resulting in a topological phase of the theory. In support of this we
present a variety of situations in which there is a correspondence between the
existence of perturbative tachyons in one regime and the semi-classical
annihilation of space-time. Our discussion will include many recently
investigated scenarios in string theory including Scherk-Schwarz
compactifications, Melvin magnetic backgrounds, and noncompact orbifolds. We
use this conjecture to investigate a possible web of dualities relating the
eleven-dimensional Fabinger-Horava background with nonsupersymmetric string
theories. Along the way we point out where our conjecture resolves some of the
puzzles associated with bulk closed string tachyon condensation.Comment: 31 pages, 5 figures 3 figures added, typos corrected and references
added. Discussion of Type 0/Heterotic s-duality extended and some other
points clarified Revision of discussion on Fabinger-Horava string
descendents, section on Scherk-Schwarz compactification of Horava-Witten
removed, some references adde
Can free strings propagate across plane wave singularities?
We study free string propagation in families of plane wave geometries
developing strong scale-invariant singularities in certain limits. We relate
the singular limit of the evolution for all excited string modes to that of the
center-of-mass motion (the latter existing for discrete values of the overall
plane wave profile normalization). Requiring that the entire excitation energy
of the string should be finite turns out to be quite restrictive and
essentially excludes consistent propagation across the singularity, unless
dimensionful scales are introduced at the singular locus (in an otherwise
scale-invariant space-time).Comment: 24 pages; v.2: published version, minor clarifications adde
Open Strings in Exactly Solvable Model of Curved Spacetime and PP-Wave Limit
In this paper we study the superstring version of the exactly solvable string
model constructed by Russo and Tseytlin. This model represents superstring
theory in a curved spacetime and can be seen as a generalization of the Melvin
background. We investigate D-branes in this model as probes of the background
geometry by constructing the boundary states. We find that spacetime
singularities in the model become smooth at high energy from the viewpoint of
open string. We show that there always exist bulk (movable) D-branes by the
effect of electric flux. The model also includes Nappi-Witten model as the
Penrose limit and supersymmetry is enhanced in the limit. We examine this
phenomenon in the open string spectrum. We also find the similar enhancement of
supersymmetry can be occurred in several coset models.Comment: Latex, 32 pages, typos corrected, references added, to appear in
JHEP, eq.(2.22) correcte
Spectra of PP-Wave Limits of M-/Superstring Theory on AdS_p x S^q Spaces
In this paper we show how one can obtain very simply the spectra of the
PP-wave limits of M-theory over AdS_7(4) x S^4(7) spaces and IIB superstring
theory over AdS_5 x S^5 from the oscillator construction of the Kaluza-Klein
spectra of these theories over the corresponding spaces. The PP-wave symmetry
superalgebras are obtained by taking the number P of ``colors'' of oscillators
to be large (infinite). In this large P limit, the symmetry superalgebra
osp(8*|4) of AdS_7 x S^4 and the symmetry superalgebra osp(8|4,R) of AdS_4 x
S^7 lead to isomorphic PP-wave algebras, which is the semi-direct sum of
su(4|2) with H^(18,16), while the symmetry superalgebra su(2,2|4) of AdS_5 x
S^5 leads to the semi-direct sum of [psu(2|2) + psu(2|2) + u(1)] with H^(16,16)
as its PP-wave algebra [H^(m,n) denoting a super-Heisenberg algebra with m
bosonic and n fermionic generators]. The zero mode spectra of M-theory or IIB
superstring theory in the PP-wave limit corresponds simply to the unitary
positive energy representations of these algebras whose lowest weight vector is
the Fock vacuum of all the oscillators. General positive energy supermultiplets
including those corresponding to higher modes can similarly be constructed by
the oscillator method.Comment: Typos corrected; references added; minor modifications to improve
presentation; 37 pages, LaTeX fil
AdS Bubbles, Entropy and Closed String Tachyons
We study the conjectured connection between AdS bubbles (AdS solitons) and
closed string tachyon condensations. We confirm that the entanglement entropy,
which measures the degree of freedom, decreases under the tachyon condensation.
The entropies in supergravity and free Yang-Mills agree with each other
remarkably. Next we consider the tachyon condensation on the AdS twisted circle
and argue that its endpoint is given by the twisted AdS bubble, defined by the
double Wick rotation of rotating black 3-brane solutions. We calculated the
Casimir energy and entropy and checked the agreements between the gauge and
gravity results. Finally we show an infinite boost of a null linear dilaton
theory with a tachyon wall (or bubble), leads to a solvable time-dependent
background with a bulk tachyon condensation. This is the simplest example of
spacetimes with null boundaries in string theory.Comment: 45 pages, 6 figures, harvmac, eq.(2.16) corrected, references adde
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