4,775 research outputs found
Penrose Limits of Orbifolds and Orientifolds
We study the Penrose limit of various AdS_p X S^q orbifolds. The limiting
spaces are waves with parallel rays and singular wave fronts. In particular, we
consider the orbifolds AdS_3 X S^3/\Gamma, AdS_5 X S^5/\Gamma and AdS_{4,7} X
S^{7,4}/\Gamma where \Gamma acts on the sphere and/or the AdS factor. In the
pp-wave limit, the wave fronts are the orbifolds C^2/\Gamma, C^4/\Gamma and R
XC^4/\Gamma, respectively. When desingularization is possible, we get
asymptotically locally pp-wave backgrounds (ALpp). The Penrose limit of
orientifolds are also discussed. In the AdS_5 X RP^5 case, the limiting
singularity can be resolved by an Eguchi-Hanson gravitational instanton. The
pp-wave limit of D3-branes near singularities in F-theory is also presented.
Finally, we give the embedding of D-dimensional pp-waves in flat M^{2,D} space.Comment: 20 pages, references adde
Strings on pp-waves and Hadrons in (softly broken) N=1 gauge theories
We study the Penrose limit of Type IIB duals of softly broken N=1 SU(N) gauge
theories in four dimensions, obtained as deformations of the Maldacena-Nunez
and Klebanov-Strassler backgrounds. We extract the string spectrum on the
resulting pp-wave backgrounds and discuss some properties of the conjectured
dual gauge theory hadrons, the so called "Annulons". The string zero-point
energy on the light-cone is nontrivial, due to the loss of linearly realized
worldsheet supersymmetry, and negative, even in the unbroken supersymmetric
case. This causes the appearance of non-perturbative corrections to the
hadronic mass spectrum. We briefly discuss the thermodynamic behavior of these
string models, calculating the corresponding Hagedorn temperatures.Comment: 20 page
Vector Supersymmetry of 2D Yang-Mills Theory
The vector supersymmetry of the 2D topological BF model is extended to 2D
Yang-Mills. The consequences of the corresponding Ward identity on the
ultraviolet behavior of the theory are analyzed.Comment: Some references adde
Diffeomorphisms and Holographic Anomalies
Using the relation between diffeomorphisms in the bulk and Weyl
transformations on the boundary we study the Weyl transformation properties of
the bulk metric on shell and of the boundary action. We obtain a universal
formula for one of the classes of trace anomalies in any even dimension in
terms of the parameters of the gravity action.Comment: 12 pages, harvma
Homogeneity and plane-wave limits
We explore the plane-wave limit of homogeneous spacetimes. For plane-wave
limits along homogeneous geodesics the limit is known to be homogeneous and we
exhibit the limiting metric in terms of Lie algebraic data. This simplifies
many calculations and we illustrate this with several examples. We also
investigate the behaviour of (reductive) homogeneous structures under the
plane-wave limit.Comment: In memory of Stanley Hobert, 33 pages. Minor corrections and some
simplification of Section 4.3.
Penrose limits, supergravity and brane dynamics
We investigate the Penrose limits of classical string and M-theory
backgrounds. We prove that the number of (super)symmetries of a supergravity
background never decreases in the limit. We classify all the possible Penrose
limits of AdS x S spacetimes and of supergravity brane solutions. We also
present the Penrose limits of various other solutions: intersecting branes,
supersymmetric black holes and strings in diverse dimensions, and cosmological
models. We explore the Penrose limit of an isometrically embedded spacetime and
find a generalisation to spaces with more than one time. Finally, we show that
the Penrose limit is a large tension limit for all branes including those with
fields of Born--Infeld type.Comment: 67 page
Light-like Big Bang singularities in string and matrix theories
Important open questions in cosmology require a better understanding of the
Big Bang singularity. In string and matrix theories, light-like analogues of
cosmological singularities (singular plane wave backgrounds) turn out to be
particularly tractable. We give a status report on the current understanding of
such light-like Big Bang models, presenting both solved and open problems.Comment: 20 pages, invited review for Class. Quant. Grav; v3: section 2.3
shortened, discussion on DLCQ added in section 3.1, published versio
One Loop Partition Function in Plane Waves R-R Background
We compute the one loop partition function of type IIB string in plane wave
R-R 5-form background using both path integral and operator formalisms
and show that the two results agree perfectly. The result turns out to be equal
to the partition function in the flat background. We also study the Tadpole
cancellation for the unoriented closed and open string model in plane wave R-R
5-form background studied in hep-th/0203249 and find that the cancellation of
the Tadpole requires the gauge group to be SO(8).Comment: 12 pages, no figures, latex, misprint corrected and reference added;
to appear in JHE
More on Penrose limits and non-local theories
We obtain the Penrose limit of six dimensional Non-Commutative Open String
(NCOS) theory and show that in the neighborhood of a particular null
geodesic it leads to an exactly solvable string theory (unlike their
counterparts in four or in other dimensions). We describe the phase structure
of this theory and discuss the Penrose limit in different phases including Open
D-string (OD1) theory. We compute the string spectrum and discuss their
relations with the states of various theories at different phases. We also
consider the case of general null geodesic for which the Penrose limit leads to
string theory in the time dependent pp-wave background and comment on the
renormalization group flow in the dual theory.Comment: latex, 22 pages, minor corrections, references added, published
versio
G/G models as the strong coupling limit of topologically massive gauge theory
We show that the problem of computing the vacuum expectation values of gauge
invariant operators in the strong coupling limit of topologically massive gauge
theory is equivalent to the problem of computing similar operators in the
model where is the integer coefficient of the Chern-Simons term.
The model is a topological field theory and many correlators can be
computed analytically. We also show that the effective action for the Polyakov
loop operator and static modes of the gauge fields of the strongly coupled
theory at finite temperature is a perturbed, non-topological model. In
this model, we compute the one loop effective potential for the Polyakov loop
operators and explicitly construct the low-lying excited states. In the strong
coupling limit the theory is in a deconfined phase.Comment: Latex, 23 pages, no figure
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