Antonio de Padua Santos | Universidade Federal Rural de Pernambuco (original) (raw)

Papers by Antonio de Padua Santos

In this paper, we study regular cosmic string solutions of the non-Abelian Higgs model coupled wi... more In this paper, we study regular cosmic string solutions of the non-Abelian
Higgs model coupled with gravity. In order to develop this analysis, we
constructed a set of coupled non-linear differential equations. Because there is
no closed solution for this set of equations, we solve it numerically. The
solutions we are interested in asymptote to a flat spacetime with a planar angle
deficit. The model under consideration presents two bosonic sectors, besides
the non-Abelian gauge field. The two bosonic sectors may present a direct
coupling, so we investigate the relevance of this coupling on the system,
specifically in the linear energy density of the string and on the planar angle
deficit. We also analyze the behaviors of these quantities as a function of the
energy scale where the gauge symmetry is spontaneously broken.

We investigate the fermionic condensate and the vacuum expectation value (VEV) of the energy-mome... more We investigate the fermionic condensate and the
vacuum expectation value (VEV) of the energy-momentum
tensor for a charged massive fermionic field in the geometry
of a cosmic string compactified along its axis. In addition,
we assume the presence of two types of magnetic fluxes: a
flux running along the cosmic string and another enclosed by
the compact dimension. These fluxes give rise to Aharanov–
Bohm-like effects on the VEVs. The VEVs are decomposed
into two parts corresponding to the geometry of a straight cos-
mic string without compactification plus a topological part
induced by the compactification of the string axis. Both con-
tributions are even periodic functions of the magnetic fluxes
with period equal to the flux quantum. The vacuum energy
density is equal to the radial stress for the parts corresponding
to the straight cosmic string and the topological one. More-
over, the axial stress is equal to the energy density for the
parts corresponding to the straight cosmic string; however,
for massive fermionic fields this does not occur for the topo-
logical contributions. With respect to the dependence on the
magnetic fluxes, both the fermionic condensate and the vac-
uum energy density, can be either positive or negative. More-
over, for points near the string, the main contribution to the
VEVs comes from the straight cosmic string part, whereas at
large distances the topological ones dominate. In addition to
the local characteristics of the vacuum state, we also evalu-
ate the part in the topological Casimir energy induced by the
string.

Physics Letters A, 1998

Topological defects in solids, usually described by complicated boundary conditions in elastic th... more Topological defects in solids, usually described by complicated boundary conditions in elastic theory, may be described more simply as sources of a gravity-like deformation field in the geometric approach of Katanaev and Volovich. This way, the deformation field is described by a non-Euclidean metric that incorporates the boundary conditions imposed by the defects. A possible way of gaining some insight into the motion of particles in a medium with topological defects (e.g., electrons in a dislocated metal) is to look at the geodesics of the medium around the defect. In this work, we find the exact solution for the geodesic equation for an elastic medium with a generic line defect, the dispiration, that can either be a screw dislocation or a wedge disclination for particular choices of its parameters.

In this work, we propose a geometrical model for the study of conformational properties of a star... more In this work, we propose a geometrical model for the study of conformational properties of a starburst dendrimer with the topology of a truncated Bethe lattice. A convenient embedding of the Bethe lattice in the hyperbolic plane is used to study the architecture of the dendrimer. As results, we find an upper bound for the molecular size and the density profile.

In this paper, we study regular cosmic string solutions of the non-Abelian Higgs model coupled wi... more In this paper, we study regular cosmic string solutions of the non-Abelian
Higgs model coupled with gravity. In order to develop this analysis, we
constructed a set of coupled non-linear differential equations. Because there is
no closed solution for this set of equations, we solve it numerically. The
solutions we are interested in asymptote to a flat spacetime with a planar angle
deficit. The model under consideration presents two bosonic sectors, besides
the non-Abelian gauge field. The two bosonic sectors may present a direct
coupling, so we investigate the relevance of this coupling on the system,
specifically in the linear energy density of the string and on the planar angle
deficit. We also analyze the behaviors of these quantities as a function of the
energy scale where the gauge symmetry is spontaneously broken.

We investigate the fermionic condensate and the vacuum expectation value (VEV) of the energy-mome... more We investigate the fermionic condensate and the
vacuum expectation value (VEV) of the energy-momentum
tensor for a charged massive fermionic field in the geometry
of a cosmic string compactified along its axis. In addition,
we assume the presence of two types of magnetic fluxes: a
flux running along the cosmic string and another enclosed by
the compact dimension. These fluxes give rise to Aharanov–
Bohm-like effects on the VEVs. The VEVs are decomposed
into two parts corresponding to the geometry of a straight cos-
mic string without compactification plus a topological part
induced by the compactification of the string axis. Both con-
tributions are even periodic functions of the magnetic fluxes
with period equal to the flux quantum. The vacuum energy
density is equal to the radial stress for the parts corresponding
to the straight cosmic string and the topological one. More-
over, the axial stress is equal to the energy density for the
parts corresponding to the straight cosmic string; however,
for massive fermionic fields this does not occur for the topo-
logical contributions. With respect to the dependence on the
magnetic fluxes, both the fermionic condensate and the vac-
uum energy density, can be either positive or negative. More-
over, for points near the string, the main contribution to the
VEVs comes from the straight cosmic string part, whereas at
large distances the topological ones dominate. In addition to
the local characteristics of the vacuum state, we also evalu-
ate the part in the topological Casimir energy induced by the
string.

Physics Letters A, 1998

Topological defects in solids, usually described by complicated boundary conditions in elastic th... more Topological defects in solids, usually described by complicated boundary conditions in elastic theory, may be described more simply as sources of a gravity-like deformation field in the geometric approach of Katanaev and Volovich. This way, the deformation field is described by a non-Euclidean metric that incorporates the boundary conditions imposed by the defects. A possible way of gaining some insight into the motion of particles in a medium with topological defects (e.g., electrons in a dislocated metal) is to look at the geodesics of the medium around the defect. In this work, we find the exact solution for the geodesic equation for an elastic medium with a generic line defect, the dispiration, that can either be a screw dislocation or a wedge disclination for particular choices of its parameters.

In this work, we propose a geometrical model for the study of conformational properties of a star... more In this work, we propose a geometrical model for the study of conformational properties of a starburst dendrimer with the topology of a truncated Bethe lattice. A convenient embedding of the Bethe lattice in the hyperbolic plane is used to study the architecture of the dendrimer. As results, we find an upper bound for the molecular size and the density profile.