arXiv subjects
Publications and source records attributed to A. A. Garcia.
A new method is developed which permits the reconstruction of the surface-density distribution in the galactic disk of finite radius from an arbitrary smooth distribution of the angular velocity via two simple quadratures. The existence of upper limits for disk's mass and radius during the analytic continuation of rotation curves into the hidden (non-radiating) part of the disk is demonstrated.
Recently it was argued that an inflationary potential yielding power spectra characterized by a scale-invariant tensorial spectral index and a weakly scale-dependent scalar spectral index might account for a generic large-scale structure formation in the multiverses scenario of eternal inflation. Here it is shown that this statement remains true if the tensorial index is allowed to slowly vary in a wide range of angular scales. In the cases analyzed in this paper, the scalar index also slightly depends on the scales. Therefore, the production of closely resembling each other universes seems to be a common feature of inflationary scenarios with weakly scale-dependent spectral indices. With power-law inflation as the extreme case, this is the class of scenarios which may give the best fit to near future CMB observations.
Recently an inflationary potential yielding power spectra characterized by a scale-invariant tensorial spectral index and a scale-dependent scalar spectral index was introduced. We analize here the implications that this potential could have for the large-scale structure formation in the multiverses scenario of eternal inflation.
The derivation of the Demianski-Newman solution within the framework of the Ernst complex formalism is considered. We show that this solution naturally arises as a two-soliton specialization of the axisymmetric multi-soliton electrovacuum metric, and we work out the full set of the corresponding metrical fields and electromagnetic potentials. Some limits and physical properties of the DN space-time are briefly discussed.
We present a new approximation scheme that allows us to increase the accuracy of analytical predictions of the power spectra of inflationary perturbations for two specific classes of inflationary models. Among these models are chaotic inflation with a monomial potential, power-law inflation and natural inflation (inflation at a maximum). After reviewing the established first order results we calculate the amplitudes and spectral indices for these classes of models at higher orders in the slow-roll parameters for scalar and tensorial perturbations.
Gravity coupled three--dimensional $σ$--model describing the stationary Einstein--Maxwell--dilaton system with general dilaton coupling is studied. Killing equations for the corresponding five--dimensional target space are integrated. It is shown that for general coupling constant $α$ the symmetry algebra is isomorphic to the maximal solvable subalgebra of $sl(3,R)$. For two critical values $α=0$ and $α=\sqrt{3}$, Killing algebra enlarges to the full $sl(3,R)$ and $su(2,1)\times R$ algebras respectively, which correspond to five--dimensional Kaluza--Klein and four--dimensional Brans--Dicke--Maxwell theories. These two models are analyzed in terms of the unique real variables. Relation to the description in terms of complex Ernst potentials is discussed. Non--trivial discrete maps between different subspaces of the target space are found and used to generate new arbitrary--$α$ solutions to dilaton gravity.