21,229 research outputs found
Constraining fast radio burst progenitors with gravitational lensing
Fast Radio Bursts (FRBs) are new transient radio sources discovered recently.
Because of the angular resolution restriction in radio surveys, no optical
counter part has been identified yet so it is hard to determine the progenitor
of FRBs. In this paper we propose to use radio lensing survey to constrain FRB
progenitors. We show that, different types of progenitors lead to different
probabilities for a FRB to be gravitationally lensed by dark matter halos in
foreground galaxies, since different type progenitors result in different
redshift distributions of FRBs. For example, the redshift distribution of FRBs
arising from double stars shifts toward lower redshift than of the FRBs arising
from single stars, because double stars and single stars have different
evolution timescales. With detailed calculations, we predict that the FRB
sample size for producing one lensing event varies significantly for different
FRB progenitor models. We argue that this fact can be used to distinguish
different FRB models and also discuss the practical possibility of using
lensing observation in radio surveys to constrain FRB progenitors.Comment: 14 pages, including 6 figures and 1 tabl
Search for strong gravitational lensing effect in the current GRB data of BATSE
Because gamma-ray bursts (GRBs) trace the high-z Universe, there is an
appreciable probability for a GRB to be gravitational lensed by galaxies in the
universe. Herein we consider the gravitational lensing effect of GRBs
contributed by the dark matter halos in galaxies. Assuming that all halos have
the singular isothermal sphere (SIS) mass profile in the mass range and all GRB samples follow
the intrinsic redshift distribution and luminosity function derived from the
Swift LGRBs sample, we calculated the gravitational lensing probability in
BATSE, Swift/BAT and Fermi/GBM GRBs, respectively. With an derived probability
result in BATSE GRBs, we searched for lensed GRB pairs in the BATSE 5B GRB
Spectral catalog. The search did not find any convincing gravitationally lensed
events. We discuss our result and future observations for GRB lensing
observation.Comment: 18 pages, 8 figure
Decoherence of quantum gates based on Aharonov-Anandan phases in a multistep scheme
We study quantum decoherence of single-qubit and two-qubit Aharonov-Anandan
(AA) geometric phase gates realized in a multistep scheme. Each AA gate is also
compared with the dynamical phase gate performing the same unitary
transformation within the same time period and coupled with the same
environment, which is modeled as harmonic oscillators. It is found that the
fidelities and the entanglement protection of the AA phase gates are enhanced
by the states being superpositions of different eigenstates of the
environmental coupling, and the noncommutativity between the qubit interaction
and the environmental coupling.Comment: 7 pages, published in EP
Correlation-driven chiral superconductivity and chiral spin order in doped kagome lattice
We study the electronic instabilities of the Hubbard model in the 1/6
hole-doped Kagome lattice using the variational cluster approach. The 1/6 hole
doping is unique in the sense that the Fermi level is at the von Hove
singularity and the Fermi surface has a perfect nesting. In this case, a
density wave is usually realized. However, we demonstrate here that the chiral
superconducting state is most favorable when a small
Hubbard interaction U(U<3.0t) is introduced, and a scalar chiral spin order is
realized at large U(U>5.0t). Between them, a spin-disordered insulating state
is proposed.Comment: 5 pages, 4 figure
Quantum Phase Transition in Hall Conductivity on an Anisotropic Kagome Lattice
We study the quantum Hall effect(QHE) on the Kagom\'{e} lattice with
anisotropy in one of the hopping integrals. We find a new type of QHE
characterized by the quantization rules for Hall conductivity
and Landau Levels ( is an integer), which is different from any known type. This phase
evolves from the QHE phase with and in the isotropic case, which is realized in a system
with massless Dirac fermions (such as in graphene). The phase transition does
not occur simultaneously in all Hall plateaus as usual but in sequence from low
to high energies, with the increase of hopping anisotropy.Comment: 5 pages, 4 figure
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