Time-Dependent Warping, Fluxes, and NCYM (2003)
Dasgupta, Keshav, Rajesh, Govindan, Robbins, Daniel, Sethi, Savdeep
We describe the supergravity solutions dual to D6-branes with both time-dependent and time-independent B-fields. These backgrounds generalize the Taub-NUT metric in two key ways: they have asymmetric...
Comments on Cosmological Singularities in String Theory (2002)
Berkooz, Micha, Craps, Ben, Kutasov, David, Rajesh, Govindan
We compute string scattering amplitudes in an orbifold of Minkowski space by a boost, and show how certain divergences in the four point function are associated with graviton exchange near the...
String Propagation in the Presence of Cosmological Singularities (2002)
Craps, Ben, Kutasov, David, Rajesh, Govindan
We study string propagation in a spacetime with positive cosmological constant, which includes a circle whose radius approaches a finite value as |t|\to\infty, and goes to zero at t=0. Near this...
Nonlocal Field Theories and their Gravity Duals (2001)
Bergman, Aaron, Dasgupta, Keshav, Ganor, Ori J., Karczmarek, Joanna L., Rajesh, Govindan
The gravity duals of nonlocal field theories in the large N limit exhibit a novel behavior near the boundary. To explore this, we present and study the duals of dipole theories - a particular class...
Codimension-Three Bundle Singularities in F-Theory (2000)
Candelas, Philip, Diaconescu, Duiliu-Emanuel, Florea, Bogdan, Morrison, David R., Rajesh, Govindan
We study new nonperturbative phenomena in N=1 heterotic string vacua corresponding to pointlike bundle singularities in codimension three. These degenerations result in new four-dimensional infrared...
Duality and Non-Commutative Gauge Theory (2000)
Ganor, Ori J., Rajesh, Govindan, Sethi, Savdeep
We study the generalization of S-duality to non-commutative gauge theories. For rank one theories, we obtain the leading terms of the dual theory by Legendre transforming the Lagrangian of the...
Noncommutative Tachyons (2000)
Dasgupta, Keshav, Mukhi, Sunil, Rajesh, Govindan
When unstable Dp-branes in type II string theory are placed in a B-field, the resulting tachyonic world-volume theory becomes noncommutative. We argue that for large noncommutativity parameter,...
Pinned Branes and New Non Lorentz Invariant Theories (2000)
Chakravarty, Shoibal, Dasgupta, Keshav, Ganor, Ori J., Rajesh, Govindan
We describe a mechanism for localising branes in ambient space. When a 3-form flux is turned on in a Taub-NUT space, an M5-brane gets an effective potential that pins it to the center of the space. A...
M Theory, Orientifolds and G-Flux (1999)
Dasgupta, Keshav, Rajesh, Govindan, Sethi, Savdeep
We study the properties of M and F theory compactifications to three and four dimensions with background fluxes. We provide a simple construction of supersymmetric vacua, including some with...
Geometrical Aspects of Fivebranes in Heterotic/F-Theory Duality in Four Dimensions (1999)
Diaconescu, Duiliu-Emanuel, Rajesh, Govindan
We use the method of stable degenerations to study the local geometry of Calabi-Yau fourfolds for F-theory compactifications dual to heterotic compactifications on a Calabi-Yau threefold with...
Toric geometry and F-theory/Heterotic Duality in Four Dimensions (1998)
We study, as hypersurfaces in toric varieties, elliptic Calabi-Yau fourfolds for F-theory compactifications dual to E8xE8 heterotic strings compactified to four dimensions on elliptic Calabi-Yau...
Matter from Toric Geometry (1997)
Candelas, Philip, Perevalov, Eugene, Rajesh, Govindan
We present an algorithm for obtaining the matter content of effective six-dimensional theories resulting from compactification of F-theory on elliptic Calabi-Yau threefolds which are hypersurfaces in...
Mirror Symmetry via Deformation of Bundles on K3 Surfaces (1997)
Perevalov, Eugene, Rajesh, Govindan
We consider F-theory compactifications on a mirror pair of elliptic Calabi-Yau threefolds. This yields two different six-dimensional theories, each of them being nonperturbatively equivalent to some...
Toric Geometry and Enhanced Gauge Symmetry of F-Theory/Heterotic Vacua (1997)
Candelas, Philip, Perevalov, Eugene, Rajesh, Govindan
We study F-theory compactified on elliptic Calabi-Yau threefolds that are realised as hypersurfaces in toric varieties. The enhanced gauge group as well as the number of massless tensor multiplets...
Comments on A,B,C Chains of Heterotic and Type II Vacua (1997)
Candelas, Philip, Perevalov, Eugene, Rajesh, Govindan
We construct, as hypersurfaces in toric varieties, Calabi-Yau manifolds corresponding to F-theory vacua dual to E8*E8 heterotic strings compactified to six dimensions on K3 surfaces with...
F-Theory Duals of Nonperturbative Heterotic E8xE8 Vacua in Six Dimensions (1996)
Candelas, Philip, Perevalov, Eugene, Rajesh, Govindan
We present a systematic way of generating F-theory models dual to nonperturbative vacua (i.e., vacua with extra tensor multiplets) of heterotic E8xE8 strings compactified on K3, using hypersurfaces...