اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدVacuum current and polarization induced by magnetic flux in a higher-dimensional cosmic string in the presence of a flat boundary
129
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
In this paper we analyze the vacuum bosonic current and polarization induced by a magnetic flux running along a higher dimensional cosmic string in the presence of a flat boundary orthogonal to the string. In our analysis we assume that the quantum field obeys Dirichlet or Neunmann conditions on the flat boundary. In order to develop this analysis we calculate the corresponding Wightman function. As consequence of the boundary, the Wightamn function is expressed in term of two contributions: The first one corresponds to the boundary-free cosmic string Wightman function, while the second one is induced by the boundary. The boundary-induced contributions have opposite signs for Dirichlet and Newman scalars. Because the analysis of vacuum current and polarization effects in the boundary-free cosmic string spacetime have been developed in the literature, here we are mainly interested in the calculations of the effects induced by the boundary. Regarding to the induced current, we show that, depending on the condition adopted, the boundary-induced azimuthal current can cancel or intensifies the total induced azimuthal current on the boundary; moreover, the boundary-induced azimuthal current is a periodic odd function of the magnetic flux. As to the vacuum expectation values of the field squared and the energy-momentum tensor, the boundary-induced contributions are even functions of magnetic flux. In particular, we consider some special cases of the boundary-induced part of the energy density and evaluate the normal vacuum force on the boundary.
قيم البحث
اقرأ أيضاً
In this paper, we consider a massive charged fermionic quantum field and investigate the current densities induced by a magnetic flux running along the core of an idealized cosmic string in the background geometry of a 5-dimensional anti-de Sitter sp
acetime, assuming that an extra dimension is compactified. Along the compact dimension quasi-periodicity condition is imposed on the field with a general phase. Moreover, we admit the presence of a magnetic flux enclosed by the compactified axis. The latter gives rise to Ahanorov-Bohm-like effect on the vacuum expectation value of the currents. In this setup, only azimuthal and axial current densities take place. The former presents two contributions, with the first one due to the cosmic string in a 5-dimensional AdS spacetime without compact dimension, and the second one being induced by the compactification itself. The latter is an odd function of the magnetic flux along the cosmic string and an even function of the magnetic flux enclosed by the compactified axis with period equal to the quantum flux. As to the induced axial current, it is an even function of the magnetic flux along the strings core and an odd function of the magnetic flux enclosed by the compactification perimeter. For untwisted and twisted field along compact dimension, the axial current vanishes. The massless field case is presented as well as some asymptotic limits for the parameters of the model.
We study the fermionic condensate (FC) and the vacuum expectation value (VEV) of the energy-momentum tensor for a massive spinor field in the de Sitter (dS) spacetime including an ideal cosmic string. In addition, spatial dimension along the string i
s compactified to a circle of length $L$. The fermionic field is assumed to obey quasi-periodic condition along the $z$-axis. There are also magnetic fluxes running along the cosmic string and enclosed by the compact dimension. Both, the FC and the VEV of the energy-momentum tensor, are decomposed into two parts: one induced by the cosmic string in dS spacetime considering the absence of the compactification, and another one induced by the compactification. In particular, we show that the FC vanishes for a massless fermionic field.
The relativistic charged spinor matter field is quantized in the background of a straight cosmic string with nonvanishing transverse size. The most general boundary conditions ensuring the impossibility for matter to penetrate through the edge of the
string core are considered. The role of discrete symmetries is elucidated, and analytic expressions for the temporal and spatial components of the induced vacuum current are derived in the case of either $P$ or $CT$ invariant boundary condition with two parameters varying arbitrarily from point to point of the edge. The requirement of physical plausibility for the global induced vacuum characteristics is shown to remove completely an arbitrariness in boundary conditions. We find out that a magnetic field is induced in the vacuum and that a sheath in the form of a tube of the magnetic flux lines encloses a cosmic string. The dependence of the induced vacuum magnetic field strength on the string flux and tension, as well as on the transverse size of the string and on the distance from the string, is unambiguously determined.
In the present paper, we study the vacuum bosonic currents in the geometry of a compactified cosmic string in the background of the de Sitter spacetime. The currents are induced by magnetic fluxes, one running along the cosmic string and another one
enclosed by the compact dimension. To develop the analysis, we obtain the complete set of normalized bosonic wave-functions obeying a quasiperiodicity condition. In this context, we calculate the azimuthal and axial current densities and we show that these quantities are explicitly decomposed into two contributions: one originating from the geometry of a straight uncompactified cosmic string and the other induced by the compactification. We also compare the results with the literature in the case of a massive fermionic field in the same geometry.
We investigate topological effects of a cosmic string and compactification of a spatial dimension on the vacuum expectation value (VEV) of the energy-momentum tensor for a fermionic field in (4+1)-dimensional locally AdS spacetime. The contribution i
nduced by the compactification is explicitly extracted by using the Abel-Plana summation formula. The mean energy-momentum tensor is diagonal and the vacuum stresses along the direction perpendicular to the AdS boundary and along the cosmic string are equal to the energy density. All the components are even periodic functions of the magnetic fluxes inside the string core and enclosed by compact dimension, with the period equal to the flux quantum. The vacuum energy density can be either positive or negative, depending on the values of the parameters and the distance from the string. The topological contributions in the VEV of the energy-momentum tensor vanish on the AdS boundary. Near the string the effects of compactification and gravitational field are weak and the leading term in the asymptotic expansion coincides with the corresponding VEV in (4+1)-dimensional Minkowski spacetime. At large distances, the decay of the cosmic string induced contribution in the vacuum energy-momentum tensor, as a function of the proper distance from the string, follows a power law. For a cosmic string in the Minkowski bulk and for massive fields the corresponding fall off is exponential. Within the framework of the AdS/CFT correspondence, the geometry for conformal field theory on the AdS boundary corresponds to the standard cosmic string in (3+1)-dimensional Minkowski spacetime compactified along its axis.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
