8,162 research outputs found
The long-lasting optical afterglow plateau of short burst GRB 130912A
The short burst GRB 130912A was detected by Swift, Fermi satellites and
several ground-based optical telescopes. Its X-ray light curve decayed with
time normally. The optical emission, however, displayed a long term plateau,
which is the longest one in current short GRB observations. In this work we
examine the physical origin of the X-ray and optical emission of this peculiar
event. We find that the canonical forward shock afterglow emission model can
account for the X-ray and optical data self-consistently and the energy
injection model that has been widely adopted to interpret the
shallowly-decaying afterglow emission is not needed. We also find that the
burst was born in a very-low density interstellar medium, consistent with the
compact object merger model. Significant fractions of the energy of the forward
shock have been given to accelerate the non-thermal electrons and amplify the
magnetic fields (i.e., and , respectively), which are much larger than those inferred in most short
burst afterglow modeling and can explain why the long-lasting optical afterglow
plateau is rare in short GRBs.Comment: 5 pages, 2 figure
Treating the Expansive Soil Subgrade on the Goaf of Middle-Shallow Layer by Dynamic Compaction With Geogrid Reinforcement
Middle-shallow layer goaf left after the excavation of small coal mines in expansive soil areas always brings much trouble to expressway construction, the section of K21 +400~K22 +550 of Nanning outer ring expressway under construction faces such a situation. Based on the grasp of geological condition of the goaf, related national technical specifications and existing technical research about treatment, the dynamic compaction with geogird reinforcement method is applied to settle the roadbed with a good result showed in the field testing. This paper introduces the geological condition and stability evaluation of the goaf, and emphatically presents the technical note, construction procedure, quality inspection of the dynamic compaction with geogird reinforcement and the filling method of the upper expansive soil subgrade, which can offer a reference for the similar treatment projects in other expansive soil areas
Nonlinear Hall Effects in Strained Twisted Bilayer WSe
Recently, it has been pointed out that the twisting of bilayer WSe would
generate topologically non-trivial flat bands near the Fermi energy. In this
work, we show that twisted bilayer WSe (tWSe) with uniaxial strain
exhibits a large nonlinear Hall (NLH) response due to the non-trivial Berry
curvatures of the flat bands. Moreover, the NLH effect is greatly enhanced near
the topological phase transition point which can be tuned by a vertical
displacement field. Importantly, the nonlinear Hall signal changes sign across
the topological phase transition point and provides a way to identify the
topological phase transition and probe the topological properties of the flat
bands. The strong enhancement and high tunability of the NLH effect near the
topological phase transition point renders tWSe and related moire materials
new platforms for rectification and second harmonic generations.Comment: 5 pages, 3 figures. Comments are welcom
Transmission resonance in a composite plasmonic structure
The design, fabrication, and optical properties of a composite plasmonic
structure, a two-dimentional array of split-ring resonators inserted into
periodic square holes of a metal film, have been reported. A new type of
transmission resonance, which makes a significant difference from the
conventional peaks, has been suggested both theoretically and experimentally.
To understand this effect, a mechanism of ring- resonance induced dipole
emission is proposed.Comment: 14 pages, 4 figure
Estimating the central charge from the R\'enyi entanglement entropy
We calculate the von Neumann and R\'enyi bipartite entanglement entropy of
the model with a chemical potential on a 1+1 dimensional Euclidean
lattice with open and periodic boundary conditions. We show that the
Calabrese-Cardy conformal field theory predictions for the leading logarithmic
scaling with the spatial size of these entropies are consistent with a central
charge . This scaling survives the time continuum limit and truncations of
the microscopic degrees of freedom, modifications which allow us to connect the
Lagrangian formulation to quantum Hamiltonians. At half-filling, the forms of
the subleading corrections imposed by conformal field theory allow the
determination of the central charge with an accuracy better than two percent
for moderately sized lattices. We briefly discuss the possibility of estimating
the central charge using quantum simulators.Comment: 10 pages, 8 figures, 3 table
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