Abstract:
we consider the gravitational fields generated by a cosmic string, a global monopole and a tubular matter with interior magnetic field (safko-witten space-time), and examine some classical and quantum effects due to these fields. we investigate the aharonov-bohm effect in the space-time of a cosmic string, using the loop variables. in the space-time of a global monopole, we calculate the total energy radiated by a uniformly moving charged scalar particle, for small solid angle deficit. we show that the radiated energy is proportional to the cube of the velocity of the particle and to the cube of the lorenz factor, in the non-relativistic and ultra-relativistic cases, respectively. in the safko-witten space-time, we investigate the existence of an electrostatic self-force on a charged particle. we also consider a hydrogen atom in the background space-time generated by a cosmic string and we find the solutions of the corresponding dirac equation and we determine the energy levels of the atom. we investigate how the topological features of this space-time lead to shifts in the energy levels as compared with the flat minkowski space-time. we study the behavior of non-relativistic quantum particles interacting with a kratzer potential in the space-time generated by a global monopole and we find the energy spectrum in the presence of this topological defect. in the safko-witten space-time, an investigation is also made concerning the interaction of an harmonic oscillator with this background gravitational field.

Abstract:
We consider the gravitational fields generated by a cosmic string, a global monopole and a tubular matter with interior magnetic field (Safko-Witten space-time), and examine some classical and quantum effects due to these fields. We investigate the Aharonov-Bohm effect in the space-time of a cosmic string, using the loop variables. In the space-time of a global monopole, we calculate the total energy radiated by a uniformly moving charged scalar particle, for small solid angle deficit. We show that the radiated energy is proportional to the cube of the velocity of the particle and to the cube of the Lorenz factor, in the non-relativistic and ultra-relativistic cases, respectively. In the Safko-Witten space-time, we investigate the existence of an electrostatic self-force on a charged particle. We also consider a hydrogen atom in the background space-time generated by a cosmic string and we find the solutions of the corresponding Dirac equation and we determine the energy levels of the atom. We investigate how the topological features of this space-time lead to shifts in the energy levels as compared with the flat Minkowski space-time. We study the behavior of non-relativistic quantum particles interacting with a Kratzer potential in the space-time generated by a global monopole and we find the energy spectrum in the presence of this topological defect. In the Safko-Witten space-time, an investigation is also made concerning the interaction of an harmonic oscillator with this background gravitational field.

Abstract:
We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings and solutions with black-hole behaviour are discussed and compared with those found in the literature.

Abstract:
We calculate the electrostatic potential generated by a point charge in the space-time of Reissner-Nordstrom with a conical defect. An expression for the self-energy is also presented.

Abstract:
We study the relativistic quantum mechanical scattering of a bosonic particle by an infinite straight cosmic string, considering the non-minimal coupling between the bosonic field and the scalar curvature. In this case, an effective two-dimensional delta-function interaction takes place besides the usual topological scattering and a renormalization procedure is necessary in order to treat the problem that appears in connection with the delta-function.

Abstract:
we discuss the gravitomagnetism in the context of scalar-tensor theories of gravity. we obtain the equation of motion of a particle in terms of gravitoelectric and gravitomagnetic fields. we discuss the gravitomagnetic time delay and the lense-thirring effect in the context of scalar-tensor theories of gravity. in the particular case of brans-dicke theory, we compare the results obtained with those predicted by general relativity and show that within the accuracy of experiments designed to measure these effects, both theories predict essentially the same results.

Abstract:
we study the behavior of a non-relativistic quantum particle interacting with different potentials, in the background space-time generated by a cosmic string. we find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat minkowski space-time values.

Abstract:
A massless spinor particle is considered in the background gravitational field due to a rotating body. In the weak field approximation it is shown that the solution of the Weyl equations depend on the angular momentum of the rotating body, which does not affect the curvature in this approximation. This result may be looked upon as a generalization of the gravitational Aharonov-Bohm effect.

Abstract:
We study the behaviour of a non-relativistic quantum particle interacting with different potentials, in the background spacetime generated by a cosmic string. We find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat Minkowski spacetime values.

Abstract:
This work deals with the formation of black hole in bidimensional dilaton gravity coupled to scalar matter fields. We investigate two scalar matter systems, one described by a sixth power potential and the other defined with two scalar fields containing up to the fourth power in the fields. The topological solutions that appear in these cases allow the formation of black holes in the corresponding dilaton gravity models.