4,014 research outputs found
N=(4,4) Type IIA String Theory on PP-Wave Background
We construct IIA GS superstring action on the ten-dimensional pp-wave
background, which arises as the compactification of eleven-dimensional pp-wave
geometry along the isometry direction. The background geometry has 24 Killing
spinors and among them, 16 components correspond to the non-linearly realized
kinematical supersymmetry in the string action. The remaining eight components
are linearly realized and shown to be independent of x^+ coordinate, which is
identified with the world-sheet time coordinate of the string action in the
light-cone gauge. The resultant dynamical N=(4,4) supersymmetry is
investigated, which is shown to be consistent with the field contents of the
action containing two free massive supermultiplets.Comment: latex, 15 pages; v2: typos corrected, polished, references adde
Possible types of the evolution of vacuum shells around the de Sitter space
All possible evolution scenarios of a thin vacuum shell surrounding the
spherically symmetric de Sitter space have been determined and the
corresponding global geometries have been constructed. Such configurations can
appear at the final stage of the cosmological phase transition, when isolated
regions (islands) of the old vacuum remain. The islands of the old vacuum are
absorbed by the new vacuum, expand unlimitedly, or form black holes and
wormholes depending on the sizes of the islands as well as on the density and
velocity of the shells surrounding the islands.Comment: 3 pages, 1 figur
Kaigorodov spaces and their Penrose limits
Kaigorodov spaces arise, after spherical compactification, as near horizon
limits of M2, M5, and D3-branes with a particular pp-wave propagating in a
world volume direction. We show that the uncompactified near horizon
configurations K\times S are solutions of D=11 or D=10 IIB supergravity which
correspond to perturbed versions of their AdS \times S analogues. We derive the
Penrose-Gueven limits of the Kaigorodov space and the total spaces and analyse
their symmetries. An Inonu-Wigner contraction of the Lie algebra is shown to
occur, although there is a symmetry enhancement. We compare the results to the
maximally supersymmetric CW spaces found as limits of AdS\times S spacetimes:
the initial gravitational perturbation on the brane and its near horizon
geometry remains after taking non-trivial Penrose limits, but seems to
decouple. One particuliar limit yields a time-dependent homogeneous plane-wave
background whose string theory is solvable, while in the other cases we find
inhomogeneous backgrounds.Comment: latex2e, 24 page
On d=4,5,6 Vacua with 8 Supercharges
We show how all known N=2, d=4,5,6 maximally supersymmetric vacua (Hpp-waves
and aDSxS solutions) are related through dimensional reduction/oxidation
preserving all the unbroken supersymmetries. In particular we show how the N=2,
d=5 family of vacua (which are the near-horizon geometry of supersymmetric
rotating black holes) interpolates between aDS_2xS^3 and aDS_3xS^2 in parameter
space and how it can be dimensionally reduced to an N=2, d=4 dyonic
Robinson-Bertotti solution with geometry aDS_2xS^2 and oxidized to an N=2, d=6
solution with aDS_3xS^3 geometry (which is the near-horizon of the self-dual
string).Comment: Latex2e, 19 pages, 1 figure. v2: typos corrected, refs. added. v3:
very minor corrections, more refs. added, version to be published in
Classical and Quantum Gravit
Penrose Limits, the Colliding Plane Wave Problem and the Classical String Backgrounds
We show how the Szekeres form of the line element is naturally adapted to
study Penrose limits in classical string backgrounds. Relating the "old"
colliding wave problem to the Penrose limiting procedure as employed in string
theory we discuss how two orthogonal Penrose limits uniquely determine the
underlying target space when certain symmetry is imposed. We construct a
conformally deformed background with two distinct, yet exactly solvable in
terms of the string theory on R-R backgrounds, Penrose limits. Exploiting
further the similarities between the two problems we find that the Penrose
limit of the gauged WZW Nappi-Witten universe is itself a gauged WZW plane wave
solution of Sfetsos and Tseytlin. Finally, we discuss some issues related to
singularity, show the existence of a large class of non-Hausdorff solutions
with Killing Cauchy Horizons and indicate a possible resolution of the problem
of the definition of quantum vacuum in string theory on these time-dependent
backgrounds.Comment: Some misprints corrected. Matches the version in print. To appear in
Classical & Quantum Gravit
Penrose Limits, PP-Waves and Deformed M2-branes
Motivated by the recent discussions of the Penrose limit of AdS_5\times S^5,
we examine a more general class of supersymmetric pp-wave solutions of the type
IIB theory, with a larger number of non-vanishing structures in the self-dual
5-form. One of the pp-wave solutions can be obtained as a Penrose limit of a
D3/D3 intersection. In addition to 16 standard supersymmetries these
backgrounds always allow for supernumerary supersymmetries. The latter are in
one-to-one correspondence with the linearly-realised world-sheet
supersymmetries of the corresponding exactly-solvable type IIB string action.
The pp-waves provide new examples where supersymmetries will survive in a
T-duality transformation on the x^+ coordinate. The T-dual solutions can be
lifted to give supersymmetric deformed M2-branes in D=11. The deformed M2-brane
is dual to a three-dimensional field theory whose renormalisation group flow
runs from the conformal fixed point in the infra-red regime to a non-conformal
theory as the energy increases. At a certain intermediate energy scale there is
a phase transition associated with a naked singularity of the M2-brane. In the
ultra-violet limit the theory is related by T-duality to an exactly-solvable
massive IIB string theory.Comment: Latex, 23 pages. Typographical errors corrected, and references adde
A Comment on Masses, Quantum Affine Symmetries and PP-Wave Backgrounds
Two dimensional light cone world sheet massive models can be used to define
good string backgrounds.In many cases these light cone world sheet lagrangians
flow from a CFT in the UV to a theory of massive particles in the IR. The
relevant symmetry in the IR, playing a similar role to Virasoro in the UV, are
quantum affine Kac Moody algebras. Finite dimensional irreps of this algebra
are associated with the spectrum of massive particles. The case of N=0 Sine
Gordon at the N=2 point is associated with a Landau Ginzburg model that defines
a good string background. For the world sheet symmetry the N=2 piece is associated with the string conformal
invariance and the piece with the world sheet RG. The two
dimensional light cone world sheet massive model can be promoted to a CFT by
adding extra light cone fields and . From the point of view of
the quantum affine symmetry these two fields are associated, respectively, with
the center and the derivation of the affine Kac Moody algebra.Comment: 9 pages. Typos correcte
Modelling the dynamics of global monopoles
A thin wall approximation is exploited to describe a global monopole coupled
to gravity. The core is modelled by de Sitter space; its boundary by a thin
wall with a constant energy density; its exterior by the asymptotic
Schwarzschild solution with negative gravitational mass and solid angle
deficit, , where is the symmetry
breaking scale. The deficit angle equals when . We find that: (1) if , there exists a unique globally
static non-singular solution with a well defined mass, . provides
a lower bound on . If , the solution oscillates. There are no
inflating solutions in this symmetry breaking regime. (2) if ,
non-singular solutions with an inflating core and an asymptotically
cosmological exterior will exist for all . (3) if is not too large,
there exists a finite range of values of where a non-inflating monopole
will also exist. These solutions appear to be metastable towards inflation. If
is positive all solutions are singular. We provide a detailed description
of the configuration space of the model for each point in the space of
parameters, and trace the wall trajectories on both the interior
and the exterior spacetimes. Our results support the proposal that topological
defects can undergo inflation.Comment: 44 pages, REVTeX, 11 PostScript figures, submitted to the Physical
Review D. Abstract's correcte
Berezin Quantization of Gauged WZW and Coset Models
Gauged WZW and coset models are known to be useful to prove holomorphic
factorization of the partition function of WZW and coset models. In this note
we show that these gauged models can be also important to quantize the theory
in the context of the Berezin formalism. For gauged coset models Berezin
quantization procedure also admits a further holomorphic factorization in the
complex structure of the moduli space.Comment: 15+1 pages, no figures, revte
Power-law singularities in string theory and M-theory
We extend the definition of the Szekeres-Iyer power-law singularities to
supergravity, string and M-theory backgrounds, and find that are characterized
by Kasner type exponents. The near singularity geometries of brane and some
intersecting brane backgrounds are investigated and the exponents are computed.
The Penrose limits of some of these power-law singularities have profiles
for . We find the range of the
exponents for which and the frequency squares are bounded by 1/4. We
propose some qualitative tests for deciding whether a null or timelike
spacetime singularity can be resolved within string theory and M-theory based
on the near singularity geometry and its Penrose limits.Comment: 32 page
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