High-energy effective theory for a bulk brane

We derive an effective theory describing the physics of a bulk brane in the context of the RS1 model. This theory goes beyond the usual low energy effective theory in that it describes the regime where the bulk brane has a large velocity and the radion can change rapidly. We achieve this by concentrating on the region where the distance between the orbifold planes is small in comparison to the AdS length scale. Consequently our effective theory will describe the physics shortly before a bulk/boundary or boundary/boundary brane collision. We study the cosmological solutions and find that, at large velocities, the bulk brane decouples from the matter on the boundary branes, a result which remains true for cosmological perturbations.Comment: Updated version as published in PR

Submodels of Nonlinear Grassmann Sigma Models in Any Dimension and Conserved Currents, Exact Solutions

In the preceding paper(hep-th/9806084), we constructed submodels of nonlinear Grassmann sigma models in any dimension and, moreover, an infinite number of conserved currents and a wide class of exact solutions. In this paper, we first construct almost all conserved currents for the submodels and all ones for the one of ${\bf C}P^1$-model. We next review the Smirnov and Sobolev construction for the equations of ${\bf C}P^1$-submodel and extend the equations, the S-S construction and conserved currents to the higher order ones.Comment: 13 pages, AMSLaTex; an new section and an appendix adde

Super-soft symmetry energy encountering non-Newtonian gravity in neutron stars

Considering the non-Newtonian gravity proposed in the grand unification theories, we show that the stability and observed global properties of neutron stars can not rule out the super-soft nuclear symmetry energies at supra-saturation densities. The degree of possible violation of the Inverse-Square-Law of gravity in neutron stars is estimated using an Equation of State (EOS) of neutron-rich nuclear matter consistent with the available terrestrial laboratory data.Comment: Version accepted by Physical Review Letter

High-energy effective theory for orbifold branes

We derive an effective theory on the orbifold branes of the Randall-Sundrum 1 (RS1) braneworld scenario in the presence of a bulk brane. We concentrate on the regime where the three branes are close and consider a scenario where the bulk brane collides with one of the orbifold branes. This theory allows us to understand the corrections to a low-energy approach due to the presence of higher velocity terms, coming from the Kaluza-Klein modes. We consider the evolution of gravitational waves on a cosmological background and find that, within the large velocity limit, the boundary branes recover a purely four-dimensional behavior.Comment: 4 pages, accepted for publication in Phys. Rev.

Cosmological perturbations in kk-essence model

Subhorizon approximation is often used in cosmological perturbation theory. In this paper, however, it is shown that the subhorizon approximation is not always a good approximation at least in case of $k$-essence model. We also show that the sound speed given by $k$-essence model exerts a huge influence on the time evolution of the matter density perturbation, and the future observations could clarify the differences between the $\Lambda$CDM model and $k$-essence model.Comment: 21 pages, sentences and equations are corrected, conclusions are changed a littl

Baryogenesis and Gravitino Dark Matter in Gauge-Mediated Supersymmetry-Breaking Models

We discuss two cosmological issues in a generic gauge-mediated supersymmetry (SUSY)-breaking model, namely the Universe's baryon asymmetry and the gravitino dark-matter density. We show that both problems can be simultaneously solved if there exist extra matter multiplets of a SUSY-invariant mass of the order of the ``$\mu$-term'', as suggested in several realistic SUSY grand-unified theories. We propose an attractive scenario in which the observed baryon asymmetry is produced in a way totally independent of the reheating temperature of inflation without causing any cosmological gravitino problem. Furthermore, in a relatively wide parameter space, we can also explain the present mass density of cold dark matter by the thermal relics of the gravitinos without an adjustment of the reheating temperature of inflation. We point out that there is an interesting relation between the baryon asymmetry and the dark-matter density.Comment: 20 pages, 2 figure

Quantum Mechanics on Manifolds Embedded in Euclidean Space

Quantum particles confined to surfaces in higher dimensional spaces are acted upon by forces that exist only as a result of the surface geometry and the quantum mechanical nature of the system. The dynamics are particularly rich when confinement is implemented by forces that act normal to the surface. We review this confining potential formalism applied to the confinement of a particle to an arbitrary manifold embedded in a higher dimensional Euclidean space. We devote special attention to the geometrically induced gauge potential that appears in the effective Hamiltonian for motion on the surface. We emphasize that the gauge potential is only present when the space of states describing the degrees of freedom normal to the surface is degenerate. We also distinguish between the effects of the intrinsic and extrinsic geometry on the effective Hamiltonian and provide simple expressions for the induced scalar potential. We discuss examples including the case of a 3-dimensional manifold embedded in a 5-dimensional Euclidean space.Comment: 12 pages, LaTe

Elasticity of smectic liquid crystals with focal conic domains

We study the elastic properties of thermotropic smectic liquid crystals with focal conic domains (FCDs). After the application of the controlled preshear at different temperatures, we independently measured the shear modulus G' and the FCD size L. We find out that these quantities are related by the scaling relation G' ~ \gamma_{eff}/L where \gamma_{eff} is the effective surface tension of the FCDs. The experimentally obtained value of \gamma_{\rm eff} shows the same scaling as the effective surface tension of the layered systems \sqrt{KB} where K and B are the bending modulus and the layer compression modulus, respectively. The similarity of this scaling relation to that of the surfactant onion phase suggests an universal rheological behavior of the layered systems with defects.Comment: 14 pages, 7 figures, accepted for publication in JPC

Microscopic Cluster Model for Exotic Nuclei

For a better understanding of the dynamics of exotic nuclei it is of crucial importance to develop a practical microscopic theory easy to be applied to a wide range of masses. Theoretically the basic task consists in formulating an easy solvable theory able to reproduce structures and transitions of known nuclei which should be then used to calculate the sparely known properties of proton- or neutron-rich nuclei. In this paper we start by calculating energies and distributions of A\leq4 nuclei withing a unitary correlation model restricted to include only two-body correlations. The structure of complex nuclei is then calculated extending the model to include correlation effects of higher order.Comment: 10 pages, 4 figures. Final Version to be published in "Progress of Particle and Nuclear Physics (2007