Self-force of a point charge in the space-time of a symmetric wormhole

We consider the self-energy and the self-force for an electrically charged particle at rest in the wormhole space-time. We develop general approach and apply it to two specific profiles of the wormhole throat with singular and with smooth curvature. The self-force for these two profiles is found in manifest form; it is an attractive force. We also find an expression for the self-force in the case of arbitrary symmetric throat profile. Far from the throat the self-force is always attractive.Comment: 18 pages, 3 figures Comments: corrected pdf, enlarged pape

Zeta-function approach to Casimir energy with singular potentials

In the framework of zeta-function approach the Casimir energy for three simple model system: single delta potential, step function potential and three delta potentials is analyzed. It is shown that the energy contains contributions which are peculiar to the potentials. It is suggested to renormalize the energy using the condition that the energy of infinitely separated potentials is zero which corresponds to subtraction all terms of asymptotic expansion of zeta-function. The energy obtained in this way obeys all physically reasonable conditions. It is finite in the Dirichlet limit and it may be attractive or repulsive depending on the strength of potential. The effective action is calculated and it is shown that the surface contribution appears. The renormalization of the effective action is discussed.Comment: 17 pages, 2 figures, added reference, address correcte

Ground State Energy of Massive Scalar Field Inside a Spherical Region in the Global Monopole Background

Using the zeta function regularization method we calculate the ground state energy of scalar massive field inside a spherical region in the space-time of a point-like global monopole. Two cases are investigated: (i) We calculate the Casimir energy inside a sphere of radius $R$ and make an analytical analysis about it. We observe that this energy may be positive or negative depending on metric coefficient $\alpha$ and non-conformal coupling $\xi$. In the limit $R\to\infty$ we found a zero result. (ii) In the second model we surround the monopole by additional sphere of radius $r_0<R$ and consider scalar field confined in the region between these two spheres. In the latter, the ground state energy presents an additional contribution due to boundary at $r_0$ which is divergent for small radius. Additional comments about renormalization are considered.Comment: 30 pages and 2 figures. LATEX fil

Self-energy and Self-force in the Space-time of a Thick Cosmic String

We calculate the self-energy and self-force for an electrically charged particle at rest in the background of Gott-Hiscock cosmic string space-time. We found the general expression for the self-energy which is expressed in terms of the $S$ matrix of the scattering problem. The self-energy continuously falls down outward from the string's center with maximum at the origin of the string. The self-force is repulsive for an arbitrary position of the particle. It tends to zero in the string's center and also far from the string and it has a maximum value at the string's surface. The plots of the numerical calculations of the self-energy and self-force are shown.Comment: 15 pages, 4 Postscript figures, ReVTe

Self-energy and self-force on a scalar particle in a wormhole spacetime

We consider the self-energy and the self-force for scalar massless particles at rest in the short-throat flat-spacetime wormhole background. In some limiting cases we found how the sign of the self-energy changes with the non-minimal constant ξ. We found that the self-force is always attractive for the profile of the throat considered. © 2010 World Scientific Publishing Company

Self-force on a scalar particle in a class of wormhole spacetimes

We consider the self-energy and the self-force for scalar massive and massless particles at rest in a class of wormhole spacetimes. We develop a general approach to obtain the self-force and apply it to the two specific profiles of the wormhole throat, namely, with singular and with smooth curvature. We found that the self-force changes its sign at the point where nonminimal coupling ξ=1/8 (for the massless case) and it tends to infinity for specific values of ξ. It may be attractive as well as repulsive depending on the profile of the throat. For the massless particle and minimal coupling case, the electromagnetic results are recovered. © 2009 The American Physical Society

The vacuum expectation value of the spinor massive field in the cosmic string spacetime

We find the contribution to the vacuum expectation value of the energy-momentum tensor of a massive Dirac field due to the conical geometry of the cosmic string spacetime. The heat kernel and heat kernel expansion for the squared Dirac operator in this background are also considered and the first three coefficients are found in an explicit form. © 2006 IOP Publishing Ltd