Vector fields localization on brane worlds

To confine vector bosons in the four dimensional sector of a domain wall spacetime, we propose a mechanism in which the interaction among vectors is propagated via the self-interaction of the scalar wall. In the process, the vector acquires an asymptotic mass, defined by the bulk cosmological constant, and it ends up coupled to the wall by the tension of the brane. The mechanism is applied on the Randall Sundrum scenario and regular versions of it, and on singular domain walls. In any case, the electrostatic potential between two charged particles is defined by both the vector state attached to the wall and a continuous tower of massive vector states that propagate freely along the scenario's extra dimension.

A solvable model for fermion masses on a warped 6D world with the extra 2D sphere

In a warped 6D world with an extra two-dimensional sphere, we propose an exactly solvable model for fermion masses with zero mode. The warp factor is given by ϕ(θ, φ) = sin θ cos φ, which is a solution to the 6D Einstein equation with the bulk cosmological constant Λ and the energy–momentum tensor of the bulk matter fields. Our model provides another possibility of obtaining fermion zero mode, rather than traditional model based on Dirac's monopole.

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.

WARPED COMPACTIFICATION ON SIGMA MODEL, SKYRMIONS IN SIX DIMENSIONS

We construct two distinct brane solutions in six dimensional effective field theory models. The CP 1 sigma model and the baby skyrmion realize warped compactification of the extra dimensions for negative bulk cosmological constant. Higher winding number solutions of the baby skyrmion are also presented.

BRANE SOLUTIONS WITH A QUADRATIC POTENTIAL IN STRING FRAME

We have examined brane world solutions for the low energy effective string gravity action coupled with a quadratic dilaton potential in string frame. For a negative bulk cosmological constant, static 3-brane solutions exist. Their properties are analyzed depending on the quadratic potential parameters. It is found that a brane solution in a curved bulk space in Einstein frame corresponds to a dilaton solution in flat space in string frame.

EFFECTIVE COSMOLOGICAL CONSTANT IN BRANE COSMOLOGY

We consider a brane-world of co-dimension one without reflection symmetry. Through it, we give a possible explanation of the great discrepancy between the vacuum energy and the observed cosmological constant without contradiction to the knowledge we have about our Universe. We also show the gravity observed will be standard four-dimensional gravity as long as the discrepancy of the bulk cosmological constant at different sides of the brane is small enough.

VACUUM ENERGY DENSITY AND COSMOLOGICAL CONSTANT IN dS BRANE-WORLD

We discuss the vacuum energy density and the cosmological constant of dS5 brane-world with a dilaton field. It is shown that a stable AdS4 brane can be constructed and gravity localization can be realized. An explicit relation between the dS bulk cosmological constant and the brane cosmological constant is obtained. The discrete mass spectrum of the massive scalar field in the AdS4 brane is used to acquire the relationship between the brane cosmological constant and the vacuum energy density. The vacuum energy density in the brane gotten by this method is in agreement with astronomical observations.

SPONTANEOUS PHYSICAL COMPACTIFICATION OF THE EXTRA DIMENSIONS

We conjecture that the extra dimensions are physical noncompact at high energy scale or high temperature; after the symmetry breaking or cosmological phase transition, the bulk cosmological constant may become negative, and then, the extra dimensions may become physical compact at low energy scale. We show this in a five-dimensional toy brane model with three parallel three-branes and a real bulk scalar whose potential is temperature-dependent. We also point out that after the global or gauge symmetry breaking, or the supersymmetry breaking in supergravity theory, the spontaneous physical compactification of the extra dimensions might be realized.