637 research outputs found
Time-dependent toroidal compactification proposals and the Bianchi type I model: classical and quantum solutions
In this work we construct an effective four-dimensional model by
compactifying a ten-dimensional theory of gravity coupled with a real scalar
dilaton field on a time-dependent torus. This approach is applied to
anisotropic cosmological Bianchi type I model for which we study the classical
coupling of the anisotropic scale factors with the two real scalar moduli
produced by the compactification process. Under this approach, we present an
isotropization mechanism for the Bianchi I cosmological model through the
analysis of the ratio between the anisotropic parameters and the volume of the
Universe which in general keeps constant or runs into zero for late times. We
also find that the presence of extra dimensions in this model can accelerate
the isotropization process depending on the momenta moduli values. Finally, we
present some solutions to the corresponding Wheeler-DeWitt (WDW) equation in
the context of Standard Quantum Cosmology.Comment: LaTeX source, 16 pages, Modified title and additional references.
Advances in High Energy Physics, 201
Exact treatment of dispersion relations in pp and p\=p elastic scattering
Based on a study of the properties of the Lerch's transcendent, exact closed
forms of dispersion relations for amplitudes and for derivatives of amplitudes
in pp and p\=p scattering are introduced. Exact and complete expressions are
written for the real parts and for their derivatives at based on given
inputs for the energy dependence of the total cross sections and of the slopes
of the imaginary parts. The results are prepared for application in the
analysis of forward scattering data of the pp and p\=p systems at all energies,
where exact and precise representations can be written.Comment: 23 pages, 1 figur
The direct boundary element method: 2D site effects assessment on laterally varying layered media (methodology)
The Direct Boundary Element Method (DBEM) is presented to solve the elastodynamic field equations in 2D, and a complete comprehensive implementation is given. The DBEM is a useful approach to obtain reliable numerical estimates of site effects on seismic ground motion due to irregular geological configurations, both of layering and topography. The method is based on the discretization of the classical Somigliana's elastodynamic representation equation which stems from the reciprocity theorem. This equation is given in terms of the Green's function which is the full-space harmonic steady-state fundamental solution. The formulation permits the treatment of viscoelastic media, therefore site models with intrinsic attenuation can be examined. By means of this approach, the calculation of 2D scattering of seismic waves, due to the incidence of P and SV waves on irregular topographical profiles is performed. Sites such as, canyons, mountains and valleys in irregular multilayered media are computed to test the technique. The obtained transfer functions show excellent agreement with already published results
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