120076947
Cosmology in multiply warped braneworld scenario
Hubble expansion in warped braneworld model is addressed in the presence of more than one warped extra dimensions. Some distinct phenomenological signatures of such model has already been discussed in the context of collider-based experiments as well as to explain the fermion mass hierarchy in the Standard Model of elementary particles. In this paper, we explore some cosmological implications of such a model. It is shown that while the expansion depends on all the moduli, an exponential nature of the expansion of the scale factor emerges as a generic feature which is independent of the number of extra dimensions but depends only on the bulk cosmological constant and brane pressure. A generalized expression for the effective 3-brane cosmological constant in such model has been derived. This generalizes the well-known fine tuning/detuning between the bulk cosmological constant and brane tension to obtain the desired cosmological constant on the brane. The warped factor corresponding to the higher-dimensional cosmological scenario is determined and the issue of gauge hierarchy problem is discussed.
118380719
Radion stability and induced, on-brane geometries in an effective scalar-tensor theory of gravity
About a decade ago, using a specific expansion scheme, effective, on-brane scalar tensor theories of gravity were proposed by Kanno and Soda (Phys.Rev. {\bf D 66} 083506 ,(2002)) in the context of the warped two brane model of Randall--Sundrum. The inter-related effective theories on both the branes were derived with the space-time dependent radion field playing a crucial role. Taking a re-look at this effective theory, we find cosmological and spherically symmetric, static solutions sourced by a radion--induced, effective stress energy, as well as additional, on-brane matter. The distance between the branes (governed by the time or space dependent radion) is shown to be stable and asymptotically non-zero, thereby setting aside any possibility of brane collisions. It turns out that the inclusion of on-brane matter plays a decisive role in stabilising the radion - a fact which we demonstrate through our solutions.
15221926
Large rotating AdS black holes from fluid mechanics
We use the AdS/CFT correspondence to argue that large rotating black holes in global AdSD spaces are dual to stationary solutions of the relativistic Navier-Stokes equations on SD−2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating black holes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating black holes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning black holes. Our fluid dynamical description applies to large non-extremal black holes as well as a class of large non-supersymmetric extremal black holes, but is never valid for supersymmetric black holes. Our results yield predictions for the thermodynamics of all large black holes in all theories of gravity on AdS spaces, for example, string theory on AdS5 × S5 and M theory on AdS4 × S7 and AdS7 × S4.
11891649
Supersymmetric states of N = 4 Yang-Mills from giant gravitons
Mikhailov has constructed an infinite family of 1 BPS D3-branes in AdS5 × S 5 . We regulate Mikhailov's solution space by focussing on finite dimensional submani- folds. Our submanifolds are topologically complex projective spaces with symplectic form cohomologically equal to 2πN times the Fubini-Study Kahler class. Upon quan- tization and removing the regulator we find the Hilbert Space of N noninteracting Bose particles in a 3d Harmonic oscillator, a result previously conjectured by Beasley. This Hilbert Space is isomorphic to the classical chiral ring of 1 BPS states in N = 4 Yang-Mills theory. We view our result as evidence that the spectrum of 1 BPS states in N = 4 Yang Mills theory, which is known to jump discontinuously from zero to infinitesimal coupling, receives no further renormalization at finite values of the 't Hooft coupling.