Results 1  10
of
12
Gauge Symmetry and Supersymmetry Breaking From Intersecting Branes,” arXiv:hepth/0703135
"... We study a system of intersecting NS and Dbranes in type IIA string theory in IR 9,1. We show that the 3 + 1 dimensional nonsupersymmetric theory at the intersection has unstable vacua which are longlived in some regions of the parameter space of brane configurations, and disappear in others. We ..."
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Cited by 47 (10 self)
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We study a system of intersecting NS and Dbranes in type IIA string theory in IR 9,1. We show that the 3 + 1 dimensional nonsupersymmetric theory at the intersection has unstable vacua which are longlived in some regions of the parameter space of brane configurations, and disappear in others. We also comment on the relation of our construction to systems of D and ¯ Dbranes wrapped around cycles of noncompact CalabiYau manifolds and to other related systems. 3/07
NonCritical Pure Spinor Superstrings
, 2006
"... We construct noncritical pure spinor superstrings in two, four and six dimensions. We find explicitly the map between the RNS variables and the pure spinor ones in the linear dilaton background. The RNS variables map onto a patch of the pure spinor space and the holomorphic top form on the pure spi ..."
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Cited by 15 (3 self)
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We construct noncritical pure spinor superstrings in two, four and six dimensions. We find explicitly the map between the RNS variables and the pure spinor ones in the linear dilaton background. The RNS variables map onto a patch of the pure spinor space and the holomorphic top form on the pure spinor space is an essential ingredient of the mapping. A basic feature of the map is the requirement of doubling the superspace, which we analyze in detail. We study the structure of the noncritical pure spinor space, which is different from the tendimensional one, and its quantum anomalies. We compute the pure spinor lowest lying BRST cohomology and find an agreement with the RNS spectra. The analysis is generalized to curved backgrounds and we construct as an example the noncritical pure spinor type IIA superstring on AdS4 with RR 4form flux.
Treelevel stability without spacetime fermions: Novel examples
 in string theory,” JHEP 07 (2007) 065, arXiv:0705.2140 [hepth
"... Is perturbative stability intimately tied with the existence of spacetime fermions in string theory in more than two dimensions? Type 0 ′ B string theory in tendimensional flat space is a rare example of a nontachyonic, nonsupersymmetric string theory with a purely bosonic closed string spectrum. ..."
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Cited by 8 (2 self)
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Is perturbative stability intimately tied with the existence of spacetime fermions in string theory in more than two dimensions? Type 0 ′ B string theory in tendimensional flat space is a rare example of a nontachyonic, nonsupersymmetric string theory with a purely bosonic closed string spectrum. However, all known type 0 ′ constructions exhibit massless NSNS tadpoles signaling the fact that we are not expanding around a true vacuum of the theory. In this note, we are searching for perturbatively stable examples of type 0 ′ string theory without massless tadpoles in backgrounds with a spatially varying dilaton. We present two examples with this property in noncritical string theories that exhibit fourand sixdimensional Poincaré invariance. We discuss the Dbranes that can be embedded in this context and the type of gauge theories that can be constructed in this manner. We also comment on the embedding of these noncritical models in critical string theories and their holographic (Little String Theory) interpretation and propose a general conjecture for the role of asymptotic supersymmetry in perturbative string theory.
Long Strings, Anomaly Cancellation, Phase Transitions, Tduality and Locality
 in the 2d Heterotic String,” [arXiv:hepth/0511220
"... We study the noncritical twodimensional heterotic string. Long fundamental strings play a crucial role in the dynamics. They cancel anomalies and lead to phase transitions when the system is compactified on a Euclidean circle. A careful analysis of the gauge symmetries of the system uncovers new su ..."
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Cited by 7 (1 self)
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We study the noncritical twodimensional heterotic string. Long fundamental strings play a crucial role in the dynamics. They cancel anomalies and lead to phase transitions when the system is compactified on a Euclidean circle. A careful analysis of the gauge symmetries of the system uncovers new subtleties leading to modifications of the worldsheet results. The compactification on a Euclidean thermal circle is particularly interesting. It leads us to an incompatibility between Tduality (and its corresponding gauge symmetry) and locality. 11/05
Black Hole  String Transition and Rolling Dbrane
"... We investigate the black hole string transition in the twodimensional Lorentzian black hole system from the exact boundary states that describe the rolling Dbrane falling down into the twodimensional black hole. The black hole string phase transition is one of the fundamental properties of the ..."
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Cited by 3 (0 self)
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We investigate the black hole string transition in the twodimensional Lorentzian black hole system from the exact boundary states that describe the rolling Dbrane falling down into the twodimensional black hole. The black hole string phase transition is one of the fundamental properties of the nonsupersymmetric black holes in string theory, and we will reveal the nature of the phase transition from the exactly solvable worldsheet conformal field theory viewpoint. Since the twodimensional Lorentzian black hole system (SL(2; R)k/U(1) coset model at level k) typically appears as nearhorizon geometries of various singularities such as NS5branes in string theory, our results can be regarded as the probe of such singularities from the nonsupersymmetric probe rolling Dbrane. The exact construction of boundary states for the rolling D0brane falling down into the twodimensional Dbrane enables us to probe the phase transition at k = 1 directly in the physical amplitudes. During the study, we uncover three fundamental questions in string theory as a consistent theory of quantum gravity: small charge limit v.s. large charge limit of nonsupersymmetric quantum black holes, analyticity v.s. nonanalyticity in physical amplitudes and physical observables, and unitarity v.s. open closed duality in timedependent string backgrounds.
Synopsis
, 804
"... We study several classes of marginal deformations of the conformal field theory SU(2)k × Rφ. This theory describes the nearhorizon region of a stack of parallel and coincident NS5branes and is related holographically to little string theory. We investigate the supersymmetry properties of these def ..."
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Cited by 2 (0 self)
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We study several classes of marginal deformations of the conformal field theory SU(2)k × Rφ. This theory describes the nearhorizon region of a stack of parallel and coincident NS5branes and is related holographically to little string theory. We investigate the supersymmetry properties of these deformations and we elucidate their rôle in the context of holography. The conformal field theory moduli space contains “nonholographic ” operators that do not seem to have a simple interpretation in little string theory. Subsequently, we analyze several NS5brane configurations in terms of SU(2)k × Rφ deformations. We discuss in detail interesting phenomena, like the excision of the strong coupling region associated with the linear dilaton and the manifestation of the symmetries of an NS5brane setup in the deforming operators. Finally, we present a class of conformally hyperkähler geometries that arise as “nonholographic ” deformations of SU(2)k × Rφ. a
Closed string tachyon condensation in supercritical strings and rg flows, JHEP 03
, 2006
"... We show an explicit relation between an RG flow of a twodimensional gravity and an onshell tachyon condensation in the corresponding string theory, in the case when the string theory is supercritical. The shape of the tachyon potential in this case can, in principle, be obtained by examining vario ..."
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Cited by 1 (0 self)
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We show an explicit relation between an RG flow of a twodimensional gravity and an onshell tachyon condensation in the corresponding string theory, in the case when the string theory is supercritical. The shape of the tachyon potential in this case can, in principle, be obtained by examining various RG flows. We also argue that the shape of tachyon potential for a (sub)critical string can be obtained by analyzing a supercritical string which is obtained from the (sub)critical string. 1
An Alternative for Moduli Stabilisation
, 2006
"... The oneloop vacuum energy is explicitly computed for a class of perturbative string vacua where supersymmetry is spontaneously broken by a Tduality invariant asymmetric ScherkSchwarz deformation. The lowlying spectrum is tachyonfree for any value of the compactification radii and thus no Hagedo ..."
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The oneloop vacuum energy is explicitly computed for a class of perturbative string vacua where supersymmetry is spontaneously broken by a Tduality invariant asymmetric ScherkSchwarz deformation. The lowlying spectrum is tachyonfree for any value of the compactification radii and thus no Hagedornlike phasetransition takes place. Indeed, the induced effective potential is free of divergence, and has a global anti de Sitter minimum where geometric moduli are naturally stabilised. July, 2006The true vacuum state in a quantum field theory is given by the configuration with the lowest vacuum energy. In general, superstrings yield a vanishing vacuum energy for toroidal or orbifold compactifications if supersymmetry is intact. As a consequence, superstring compactifications are usually characterised by a moduli space of supersymmetric vacua. This moduli space is spanned by certain dynamical moduli with vanishing potential, whose undetermined vacuum expectation values fix the shape and size of compact internal spaces, and set the strength of gravitational and gauge interactions. This is clearly an embarrassment for any attempt at phenomenological study in String Theory since experiments
Holographic Duals of Long Open Strings
, 803
"... We study the holographic map between long open strings, which stretch between Dbranes separated in the bulk spacetime, and operators in the dual boundary theory. We focus on a generalization of the SakaiSugimoto holographic model of QCD, where the simplest chiral condensate involves an operator o ..."
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We study the holographic map between long open strings, which stretch between Dbranes separated in the bulk spacetime, and operators in the dual boundary theory. We focus on a generalization of the SakaiSugimoto holographic model of QCD, where the simplest chiral condensate involves an operator of this type. Its expectation value is dominated by a semiclassical string worldsheet, as for Wilson loops. We also discuss the deformation of the model by this operator, and in particular its effect on the meson spectrum. This deformation can be thought of as a generalization of a quark mass term to strong coupling. It leads to the first topdown holographic model of QCD with a nonAbelian chiral symmetry which is both spontaneously and explicitly broken, as in QCD. Other examples we study include halfsupersymmetric open Wilson lines, and systems of Dbranes ending on NS5branes, which can be analyzed using worldsheet methods. March 2008 1. Introduction and
On NonCritical Superstring/Black Hole Transition
, 2005
"... An interesting case of string/black hole transition occurs in twodimensional noncritical string theory dressed with a compact CFT. In these models the high energy densities of states of perturbative strings and black holes have the same leading behavior when the Hawking temperature of the black ho ..."
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An interesting case of string/black hole transition occurs in twodimensional noncritical string theory dressed with a compact CFT. In these models the high energy densities of states of perturbative strings and black holes have the same leading behavior when the Hawking temperature of the black hole is equal to the Hagedorn temperature of perturbative strings. We compare the first subleading terms in the black hole and closed string entropies in this setting and argue that the entropy interpolates between these expressions as the energy is varied. We compute the subleading correction to the black hole entropy for a specific simple model. Dec. 6