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Warped strings: Selfdual flux and contemporary compactifications
"... String theory is a leading candidate for the quantum theory of gravitation and is the only serious unified theory of all the forces of physics. Additionally, string theory seems to be mathematically unique, and it is possible that all the parameters of physics could be determined by the dynamics of ..."
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String theory is a leading candidate for the quantum theory of gravitation and is the only serious unified theory of all the forces of physics. Additionally, string theory seems to be mathematically unique, and it is possible that all the parameters of physics could be determined by the dynamics of string theory. However, there are two intertwined problems. First is that string theory requires ten dimensions for mathematical consistency, so six must be compact or otherwise decoupled from the physics we observe. Also, there exist many different ground states of string theory, so it is difficult to make predictions that are generic to string theory. Therefore, it is crucial to gain a broad understanding of all the string theory vacua, particularly those compactified to four dimensions. In recent years, our understanding of string theory compactifications has expanded greatly to include many new classes of solutions. In this dissertation, I discuss type IIB string compactifications in which the threeform field strengths satisfy a selfduality condition on the internal manifold. I
PUPT2288 Time warps
"... I reconsider asymmetrically warped compactifications, in which time and space have different warp factors. I call such compactifications time warps if the bulk geometry has neither entropy nor temperature. I provide an example starting from an asymptotically AdS5 spacetime where the speed of light, ..."
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I reconsider asymmetrically warped compactifications, in which time and space have different warp factors. I call such compactifications time warps if the bulk geometry has neither entropy nor temperature. I provide an example starting from an asymptotically AdS5 spacetime where the speed of light, measured in a fixed coordinate system, is larger near the boundary than it is deep in the interior. This example follows the general plan of earlier work on superconducting black holes. To obtain a normalizable, fourdimensional graviton, one can introduce a Planck brane whose action includes a wrongsign EinsteinHilbert term. The equation of state of the Planck brane has w < −1, which is a violation of the null energy condition. I show, in an almost dimensionindependent fashion, that such a violation must occur in a static time warp geometry. Time warps of the type I describe provide an extradimensional description of boost invariance as an emergent symmetry in the infrared. Highenergy violations of Lorentz symmetry, if confined to a strongly coupled unparticle sector dual to the time warp geometry, might manifest themselves through unusual kinematic constraints. As an example, I explain how modifications of unparticle phase space would affect the decay of a heavy particle into a light visible sector particle plus unparticle stuff.
hepth/0302049
, 2003
"... We describe the supergravity solutions dual to D6branes with both timedependent and timeindependent Bfields. These backgrounds generalize the TaubNUT metric in two key ways: they have asymmetric warp factors and background fluxes. In the timedependent case, the warping takes a novel form. Kalu ..."
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We describe the supergravity solutions dual to D6branes with both timedependent and timeindependent Bfields. These backgrounds generalize the TaubNUT metric in two key ways: they have asymmetric warp factors and background fluxes. In the timedependent case, the warping takes a novel form. KaluzaKlein reduction in these backgrounds is unusual, and we explore some of the new features. In particular, we describe how a localized gaugefield emerges with an analogue of the open string metric and coupling. We also describe a gravitational analogue of the SeibergWitten map. This provides a framework in supergravity both for studying noncommutative gauge theories, and for constructing novel warped backgrounds.
AdS/CFT Duality and the Higgs Branch of N = 2 SYM
, 2005
"... We construct the AdS description of the Higgs branch of the finite N = 2 Sp(N) gauge theory with one antisymmetric hypermultiplet and four fundamental hypermultiplets. Holography, combined with the nonrenormalization of the metric on the Higgs branch, leads to novel constraints on unknown terms in ..."
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We construct the AdS description of the Higgs branch of the finite N = 2 Sp(N) gauge theory with one antisymmetric hypermultiplet and four fundamental hypermultiplets. Holography, combined with the nonrenormalization of the metric on the Higgs branch, leads to novel constraints on unknown terms in the nonabelian DiracBornInfeld action. These terms include nonminimal couplings of Dbranes to bulk supergravity fields.
Holography and the Higgs branch of N=2 SYM
, 2004
"... We present a proposal for the description of the Higgs branch of fourdimensional N=2 supersymmetric Yang–Mills theories in the context of the AdS/CFT correspondence. We focus on a finite Sp(N) N=2 theory arising as dual of a configuration of N D3branes in the vicinity of four D7branes and an orie ..."
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We present a proposal for the description of the Higgs branch of fourdimensional N=2 supersymmetric Yang–Mills theories in the context of the AdS/CFT correspondence. We focus on a finite Sp(N) N=2 theory arising as dual of a configuration of N D3branes in the vicinity of four D7branes and an orientifold 7plane in type I ′ string theory. The field theory contains hypermultiplets in the second rank antisymmetric and in the fundamental representations. The Higgs branch has a dual description in terms of gauge field configurations with nonzero instanton number on the worldvolume of the D7branes. In this setting the nonrenormalisation of the metric on the Higgs branch implies constraints on the α ′ corrections to the D7brane effective action, including couplings to the curvature and fiveform field strength. In the second part of the paper we discuss nonrenormalisation properties of BPS Wilson lines, which are closely related to the physics of the Higgs branch. Using a formulation of the fourdimensional N=2 theory in terms of a threedimensional N=2 superspace we show that the expectation value of certain Wilsonline operators with hypermultiplets at the end points is independent of the length and thus coincides with the expectation value of the local operators parametrising the Higgs branch.
HUEP04/62 Strong Coupling Dynamics of the Higgs Branch: Rolling a Higgs by Collapsing an Instanton
, 2005
"... We construct the dual supergravity description of strongly coupled, large N, eightsupercharge gauge theories with fundamental hypermultiplets at points on the mixed CoulombHiggs branch. With certain assumptions about unknown couplings of Dbranes to supergravity, this construction gives the correct ..."
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We construct the dual supergravity description of strongly coupled, large N, eightsupercharge gauge theories with fundamental hypermultiplets at points on the mixed CoulombHiggs branch. With certain assumptions about unknown couplings of Dbranes to supergravity, this construction gives the correct metric on the hypermultiplet (Higgsbranch) component the moduli space, which decouples from the vector multiplet (Coulombbranch) moduli. Going beyond the geodesic approximation, we find that the dynamics of a hypermultiplet VEV rolling towards a singularity on the Higgs component of the moduli space is sensitive to the vector multiplet moduli. The dual description of the approach to the singularity involves collapsing “instantons ” of a nonAbelian DiracBornInfeld theory in a curved background. In general, we find a decelerating approach to the singularity, although the manner of deceleration depends on the vector multiplet moduli. Upon introducing a potential on the Higgs branch of a four dimensional N = 2 theory coupled to gravity, this deceleration mechanism might lead to interesting inflating cosmologies analogous those studied recently by Alishahiha, Silverstein and Tong.
PUPT2394 Superluminal neutrinos and extra dimensions: constraints from the null energy condition
, 2011
"... In light of the recent results from the OPERA collaboration, indicating that neutrinos can travel superluminally, I review a simple extradimensional strategy for accommodating such behavior; and I also explain why it is hard in this strategy to avoid violating the null energy condition somewhere in ..."
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In light of the recent results from the OPERA collaboration, indicating that neutrinos can travel superluminally, I review a simple extradimensional strategy for accommodating such behavior; and I also explain why it is hard in this strategy to avoid violating the null energy condition somewhere in the extra dimensions.