September 25, 2006
The backreaction on the Randall-Sundrum warped spacetime is determined in presence of scalar field in the bulk. A general analysis shows that the stability of such a model can be achieved only if the scalar field action has non-canonical higher derivative terms. It is further shown that the gauge hierarchy problem can be resolved in such a stabilized scenario by appropriate choice of various parameters of the theory. The effective cosmological constant on the brane is shown to vanish.
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April 26, 2006
The stability problem of Randall-Sundrum braneworld is readdressed in the light of stabilizing bulk scalar fields. It is shown that in such scenario the instability persists because of back-reaction even when an arbitrary potential is introduced for a canonical scalar field in the bulk. It is further shown that a bulk scalar field can indeed stabilize the braneworld when it has a tachyon-like action. The full back-reacted metric in such model is derived and a proper resolutio...
December 5, 2008
We review various key issues in connection with the warped braneworld models which provide us with new insights and explanations of physical phenomena through interesting geometrical features of such extra dimensional theories. Starting from the original Randall-Sundrum two brane models, we have discussed the stability, hierarchy and other important issues in connection with such braneworld. The role of higher derivative terms in the bulk for modulus stabilization has been ex...
September 24, 2008
We study the stabilization of inter-brane spacing modulus of generalized warped brane models with a nonzero brane cosmological constant. Employing Goldberger-Wise stabilization prescription of brane world models with a bulk scalar field, we show that the stabilized value of the modulus generally depends on the value of the brane cosmological constant. Our result further reveals that the stabilized modulus value corresponding to a vanishingly small cosmological constant can on...
November 6, 2007
We generalize the Randall Sundrum warped braneworld model in six and higher dimension and propose a resolution to the mass hierarchy among the standard model fermions. The fine tuning problem in connection with the scalar mass however is shown to reappear in a new guise in five dimensional warped model when the two form antisymmetric tensor fields, a massless string mode, propagates in the bulk. Finally the issue of modulus stabilization is re-examined in presence of a bulk s...
April 10, 2008
We explore the possibility of constructing stable, warped two--brane models which solve the hierarchy problem, with a bulk non--canonical scalar field (tachyon matter) as the source term in the action. Among our examples are two models--one with a warp factor (denoted as $e^{-2f(\sigma)}$) which differs from that of the standard Randall--Sundrum by the addition of a quadratic piece in the $f(\sigma)$ and another, where the warping is super-exponential. We investigate the issu...
July 28, 2005
We consider a new braneworld model with a bulk scalar field coupled to gravity. The bulk scalar action is inspired by the proposed low energy effective action around the tachyon vacuum. A class of warped geometries representing solutions of this Einstein-scalar system for a specific scalar potential is found. The geometry is non singular with a decaying warp factor and a negative Ricci curvature. The solution of the hierarchy problem is obtained using this type of warping. Th...
December 18, 2000
We show that exponentially large warp factor hierarchies can be dynamically generated in supersymmetric compactifications. The compactification we consider is the supersymmetric extension of the Randall-Sundrum model. The crucial issue is the stabilization of the radius modulus for large warp factor. The stabilization sector we employ is very simple, consisting of two pure Yang--Mills sectors, one in the bulk and the other localized on a brane. The only fine-tuning required i...
April 24, 2003
Generalizations of the Randall-Sundrum model containing a bulk scalar field $\Phi$ interacting with the curvature $R$ through the general coupling $R f(\Phi)$ are considered. We derive the general form of the effective 4D potential for the spin-zero fields and show that in the mass matrix the radion mixes with the Kaluza-Klein modes of the bulk scalar fluctuations. We demonstrate that it is possible to choose a non-trivial background form $\Phi_0(y)$ (where $y$ is the extra d...
August 23, 2000
We present the 5-dimensional cosmological solutions in the Randall-Sundrum warped compactification scenario, using the Goldberger-Wise mechanism to stabilize the size of the extra dimension. Matter on the Planck and TeV branes is treated perturbatively, to first order. The back-reaction of the scalar field on the metric is taken into account. We identify the appropriate gauge-invariant degrees of freedom, and show that the perturbations in the bulk scalar can be gauged away. ...
February 14, 2001
There are many interesting issues in the brane world with a large/warped extra dimension. We focus on the cosmological aspects. We review the cosmological solutions of the brane world and how the conventional four-dimensional cosmology is recovered by including the effect of stabilization. Its implications on the mass hierarchy and the cosmological constant are discussed.