2,015 research outputs found
gauge vector field on a codimension-2 brane
In this paper, we obtain a gauge invariant effective action for a bulk
massless gauge vector field on a brane with codimension two by using a
general Kaluza-Klein (KK) decomposition for the field. It suggests that there
exist two types of scalar KK modes to keep the gauge invariance of the action
for the massive vector KK modes. Both the vector and scalar KK modes can be
massive. The masses of the vector KK modes contain two parts,
and , due to the existence of the two extra
dimensions. The masses of the two types of scalar KK modes and
are related to the vector ones, i.e.,
and . Moreover, we
derive two Schr\"{o}dinger-like equations for the vector KK modes, for which
the effective potentials are just the functions of the warp factor.Comment: 15 pages,no figures, accepted by JHE
Null geodesics and gravitational lensing in a nonsingular spacetime
In this paper, the null geodesics and gravitational lensing in a nonsingular
spacetime are investigated. According to the nature of the null geodesics, the
spacetime is divided into several cases. In the weak deflection limit, we find
the influence of the nonsingularity parameter on the positions and
magnifications of the images is negligible. In the strong deflection limit, the
coefficients and observables for the gravitational lensing in a nonsingular
black hole background and a weakly nonsingular spacetime are obtained.
Comparing these results, we find that, in a weakly nonsingular spacetime, the
relativistic images have smaller angular position and relative magnification,
but larger angular separation than that of a nonsingular black hole. These
results might offer a way to probe the spacetime nonsingularity parameter and
put a bound on it by the astronomical instruments in the near future.Comment: 15 pages, 5 figures, 1 tabl
Bulk matter fields on two-field thick branes
In this paper we obtain a new solution of a brane made up of a scalar field
coupled to a dilaton. There is a unique parameter in the solution, which
decides the distribution of the energy density and will effect the localization
of bulk matter fields. For free vector fields, we find that the zero mode can
be localized on the brane. And for vector fields coupled with the dilaton via
, the condition for localizing the zero mode is
with with , which
includes the case . While the zero mode for free Kalb-Ramond fields can
not be localized on the brane, if only we introduce a coupling between the
Kalb-Ramond fields and the dilaton via .
When the coupling constant satisfies with or
with , the zero mode for the KR fields can
be localized on the brane. For spin half fermion fields, we consider the
coupling between the fermions
and the background scalars with positive Yukawa coupling . The effective
potentials for both chiral fermions have three types of shapes decided by the
relation between the dilaton-fermion coupling constant and the
parameter . For , the zero mode of left-chiral
fermion can be localized on the brane. While for with
or with , the zero mode for
left-chiral fermion also can be localized.Comment: 22 pages, 8 figures, improved version, accepted by Physical Review
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