1,957 research outputs found
Vacuum polarization by topological defects in de Sitter spacetime
In this paper we investigate the vacuum polarization effects associated with
a massive quantum scalar field in de Sitter spacetime in the presence of
gravitational topological defects. Specifically we calculate the vacuum
expectation value of the field square, . Because this investigation
has been developed in a pure de Sitter space, here we are mainly interested on
the effects induced by the presence of the defects.Comment: Talk presented at the 1st. Mediterranean Conference on Classical and
Quantum Gravity (MCCQG
Vacuum Polarization for a Massless Spin-1/2 Field in the Global Monopole Spacetime at Nonzero Temperature
In this paper we present the effects produced by the temperature in the
renormalized vacuum expectation value of the zero-zero component of the
energy-momentum tensor associated with massless left-handed spinor field in the
pointlike global monopole spacetime. In order to develop this calculation we
had to obtain the Euclidean thermal Green function in this background. Because
the expression obtained for the thermal energy density cannot be expressed in a
closed form, its explicit dependence on the temperature is not completely
evident. So, in order to obtain concrete information about its thermal
behavior, we develop a numerical analysis of our result in the high-temperature
limit for specific values of the parameter which codify the presence
of the monopole.Comment: 22 pages, LaTex format, 5 figure
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 and make an analytical analysis
about it. We observe that this energy may be positive or negative depending on
metric coefficient and non-conformal coupling . In the limit
we found a zero result. (ii) In the second model we surround the
monopole by additional sphere of radius 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 which
is divergent for small radius. Additional comments about renormalization are
considered.Comment: 30 pages and 2 figures. LATEX fil
Produção de alpĂnia em cultivo protegido na regiĂŁo litorĂąnea do estado do CearĂĄ.
bitstream/item/33803/1/Ct-137.pd
Vacuum Polarization of a Massless Scalar Field in the Background of a Global Monopole with Finite Core
In this paper we analyze the vacuum polarization effects of a massless scalar
field in the background of a global monopole considering a inner structure to
it. Specifically we investigate the effect of its structure on the vacuum
expectation value of the square of the field operator, ,
admitting a non-minimal coupling between the field with the geometry: $\xi
{\cal{R}}\hat{\Phi}^2$. Also we calculate the corrections on the vacuum
expectation value of the energy-momentum tensor, , due to
the inner structure of the monopole. In order to develop these analysis, we
calculate the Euclidean Green function associated with the system for points in
the region outside the core. As we shall see, for specific value of the
coupling parameter , the corrections caused by the inner structure of the
monopole can provide relevant contributions on these vacuum polarizations.Comment: Accepted for publication in Classical and Quantum Gravity. Added
references. 22 pages, 1 figur
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