4,780 research outputs found
Interactions for Winding Strings in Misner Space
We compute correlation functions of closed strings in Misner space, a big
crunch big bang universe. We develop a general method for correlators with
twist fields, which are relevant for the investigation on the condensation of
winding tachyon. We propose to compute the correlation functions by performing
an analytic continuation of the results in C/Z_N Euclidean orbifold. In
particular, we obtain a finite result for a general four point function of
twist fields, which might be important for the interpretation as the quartic
term of the tachyon potential. Three point functions are read off through the
factorization, which are consistent with the known results.Comment: 29 pages, no figure; typos corrected, references adde
String spectra near some null cosmological singularities
We construct cosmological spacetimes with null Kasner-like singularities as
purely gravitational solutions with no other background fields turned on. These
can be recast as anisotropic plane-wave spacetimes by coordinate
transformations. We analyse string quantization to find the spectrum of string
modes in these backgrounds. The classical string modes can be solved for
exactly in these time-dependent backgrounds, which enables a detailed study of
the near singularity string spectrum, (time-dependent) oscillator masses and
wavefunctions. We find that for low lying string modes(finite oscillation
number), the classical near-singularity string mode functions are non-divergent
for various families of singularities. Furthermore, for any infinitesimal
regularization of the vicinity of the singularity, we find a tower of string
modes of ultra-high oscillation number which propagate essentially freely in
the background. The resulting picture suggests that string interactions are
non-negligible near the singularity.Comment: Latex, 30pgs; v2. minor clarifications, references adde
Supersymmetric Intersecting Branes in Time-dependent Backgrounds
We construct a family of supersymmetric solutions in time-dependent
backgrounds in supergravity theories. One class of the solutions are
intersecting brane solutions and another class are brane solutions in pp-wave
backgrounds, and their intersection rules are also given. The relation to
existing literature is also discussed. An example of D1-D5 with linear null
dilaton together with its possible dual theory is briefly discussed.Comment: 12 pages, corrected typo, added reference, to appear in Phys. Rev.
Non-Relativistic Superstring Theories
We construct a supersymmetric version of the ``critical'' non-relativistic
bosonic string theory\cite{Kim:2007hb} with its manifest global symmetry. We
introduce the anticommuting CFT which is the super partner of the
CFT. The conformal weights of the and fields are both
1/2. The action of the fermionic sector can be transformed into that of the
relativistic superstring theory. We explicitly quantize the theory with
manifest SO(8) symmetry and find that the spectrum is similar to that of Type
IIB superstring theory. There is one notable difference: the fermions are
non-chiral. We further consider ``noncritical'' generalizations of the
supersymmetric theory using the superspace formulation. There is an infinite
range of possible string theories similar to the supercritical string theories.
We comment on the connection between the critical non-relativistic string
theory and the lightlike Linear Dilaton theory.Comment: Typos corrected, references added. A version to appear in Phys. Rev.
Matrix Big Brunch
Following the holographic description of linear dilaton null Cosmologies with
a Big Bang in terms of Matrix String Theory put forward by Craps, Sethi and
Verlinde, we propose an extended background describing a Universe including
both Big Bang and Big Crunch singularities. This belongs to a class of exact
string backgrounds and is perturbative in the string coupling far away from the
singularities, both of which can be resolved using Matrix String Theory. We
provide a simple theory capable of describing the complete evolution of this
closed Universe.Comment: 15 pages, no figures. References adde
Time Dependent Cosmologies and Their Duals
We construct a family of solutions in IIB supergravity theory. These are time
dependent or depend on a light-like coordinate and can be thought of as
deformations of AdS_5 x S^5. Several of the solutions have singularities. The
light-like solutions preserve 8 supersymmetries. We argue that these solutions
are dual to the N=4 gauge theory in a 3+1 dimensional spacetime with a metric
and a gauge coupling that is varying with time or the light-like direction
respectively. This identification allows us to map the question of singularity
resolution to the dual gauge theory.Comment: 13 pages REVTeX and AMSLaTeX. v2: corrected typos and made some
clarifications; reference added; v3: more clarifications, references adde
Effective Dynamics of the Matrix Big Bang
We study the leading quantum effects in the recently introduced Matrix Big
Bang model. This amounts to a study of supersymmetric Yang-Mills theory
compactified on the Milne orbifold. We find a one-loop potential that is
attractive near the Big Bang. Surprisingly, the potential decays very rapidly
at late times, where it appears to be generated by D-brane effects. Usually,
general covariance constrains the form of any effective action generated by
renormalization group flow. However, the form of our one-loop potential seems
to violate these constraints in a manner that suggests a connection between the
cosmological singularity and long wavelength, late time physics.Comment: 22 pages, LaTeX; some minor changes; an improved discussion of the
potentia
Null cosmological singularities and free strings
We continue exploring free strings in the background of null Kasner-like
cosmological singularities, following arXiv:0904.4532 [hep-th]. We study the
free string Schrodinger wavefunctional along the lines of arXiv:0807.1517
[hep-th]. We find the wavefunctional to be nonsingular in the vicinity of
singularities whose Kasner exponents satisfy certain relations. We compare this
with the description in other variables. We then study certain regulated
versions of these singularities where the singular region is replaced by a
substringy but nonsingular region and study the string spectra in these
backgrounds. The string modes can again be solved for exactly, giving some
insight into how string oscillator states get excited near the singularity.Comment: Latex, 24pgs, v3. PRD version, various clarifications on AdS/CFT
connections added, references adde
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