4,975 research outputs found
Deflection and gravitational lensing with finite distance effect in the strong deflection limit in stationary and axisymmetric spacetimes
We study the deflection and gravitational lensing (GL) of both timelike and
null signals in the equatorial plane of arbitrary stationary and axisymmetric
spacetimes in the strong deflection limit. Our approach employs a perturbative
method to show that both the deflection angle and the total travel time take
quasi-series forms , with the coefficients and incorporating the signal
velocity and finite distance effect of the source and detector. This new
deflection angle allows us to establish an accurate GL equation from which the
apparent angles of the relativistic images and their time delays are found.
These results are applied to the Kerr and the rotating Kalb-Ramond (KR)
spacetimes to investigate the effect of the spacetime spin in both spacetimes,
and the effective charge parameter and a transition parameter in the rotating
KR spacetime on various observables. Moreover, using our approach, the effect
of the signal velocity and the source angular position on these variables is
also studied.Comment: 15 pages, 10 figures; updated to publish versio
Duality and Parafermions Revisited
Given a two-dimensional bosonic theory with a non-anomalous
symmetry, the orbifolding and fermionization can be understood holographically
using three-dimensional BF theory with level . From a Hamiltonian
perspective, the information of dualities is encoded in a topological boundary
state which is defined as an eigenstate of certain Wilson loop operators
(anyons) in the bulk. We generalize this story to two-dimensional theories with
non-anomalous symmetry, focusing on parafermionization. We find
the generic operators defining different topological boundary states including
orbifolding and parafermionization with or subgroups of
, and discuss their algebraic properties as well as the
duality web.Comment: 39 pages, 5 figure
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