21,827 research outputs found
Low energy exciton states in a nanoscopic semiconducting ring
We consider an effective mass model for an electron-hole pair in a simplified
confinement potential, which is applicable to both a nanoscopic self-assembled
semiconducting InAs ring and a quantum dot. The linear optical susceptibility,
proportional to the absorption intensity of near-infrared transmission, is
calculated as a function of the ring radius . Compared with the
properties of the quantum dot corresponding to the model with a very small
radius , our results are in qualitative agreement with the recent
experimental measurements by Pettersson {\it et al}.Comment: 4 pages, 4 figures, revised and accepted by Phys. Rev.
Subsystem eigenstate thermalization hypothesis for entanglement entropy in CFT
We investigate a weak version of subsystem eigenstate thermalization
hypothesis (ETH) for a two-dimensional large central charge conformal field
theory by comparing the local equivalence of high energy state and thermal
state of canonical ensemble. We evaluate the single-interval R\'enyi entropy
and entanglement entropy for a heavy primary state in short interval expansion.
We verify the results of R\'enyi entropy by two different replica methods. We
find nontrivial results at the eighth order of short interval expansion, which
include an infinite number of higher order terms in the large central charge
expansion. We then evaluate the relative entropy of the reduced density
matrices to measure the difference between the heavy primary state and thermal
state of canonical ensemble, and find that the aforementioned nontrivial eighth
order results make the relative entropy unsuppressed in the large central
charge limit. By using Pinsker's and Fannes-Audenaert inequalities, we can
exploit the results of relative entropy to yield the lower and upper bounds on
trace distance of the excited-state and thermal-state reduced density matrices.
Our results are consistent with subsystem weak ETH, which requires the above
trace distance is of power-law suppression by the large central charge.
However, we are unable to pin down the exponent of power-law suppression. As a
byproduct we also calculate the relative entropy to measure the difference
between the reduced density matrices of two different heavy primary states.Comment: 28 pages, 4 figures;v2 change author list;v3 related subtleties about
weak ETH clarified; v4 minor correction to match JHEP versio
Dissimilarities of reduced density matrices and eigenstate thermalization hypothesis
We calculate various quantities that characterize the dissimilarity of
reduced density matrices for a short interval of length in a
two-dimensional (2D) large central charge conformal field theory (CFT). These
quantities include the R\'enyi entropy, entanglement entropy, relative entropy,
Jensen-Shannon divergence, as well as the Schatten 2-norm and 4-norm. We adopt
the method of operator product expansion of twist operators, and calculate the
short interval expansion of these quantities up to order of for the
contributions from the vacuum conformal family. The formal forms of these
dissimilarity measures and the derived Fisher information metric from
contributions of general operators are also given. As an application of the
results, we use these dissimilarity measures to compare the excited and thermal
states, and examine the eigenstate thermalization hypothesis (ETH) by showing
how they behave in high temperature limit. This would help to understand how
ETH in 2D CFT can be defined more precisely. We discuss the possibility that
all the dissimilarity measures considered here vanish when comparing the
reduced density matrices of an excited state and a generalized Gibbs ensemble
thermal state. We also discuss ETH for a microcanonical ensemble thermal state
in a 2D large central charge CFT, and find that it is approximately satisfied
for a small subsystem and violated for a large subsystem.Comment: V1, 34 pages, 5 figures, see collection of complete results in the
attached Mathematica notebook; V2, 38 pages, 5 figures, published versio
The Photometric Investigation of V921 Her using the Lunar-based Ultraviolet Telescope of Chang'e-3 mission
The light curve of V921 Her in ultraviolet band observed by the Lunar-based
Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our
solutions conclude that V921 Her is an early type marginal contact binary
system with an additional close-in component. The binary system is under poor
thermal contact with a temperature difference of nearly between the two
components. The close-in component contributes about of the total
luminosity in the triple system. Combining the radial velocity study together
with our photometric solutions, the mass of the primary star and secondary one
are calculated to be , . The evolutionary scenario of V921 Her is discussed.
All times of light minimum of V921 Her available in the bibliography are taken
into account and the curve is analyzed for the first time. The most
probable fitting results are discussed in the paper, which also confirm the
existence of a third component ( year) around the binary system. The
period of V921 Her is also undergoing a continuously rapid increase at a rate
of , which may due to mass
transfer from the less massive component to the more massive one
A transient solution for vesicle electrodeformation and relaxation
A transient analysis for vesicle deformation under DC electric fields is
developed. The theory extends from a droplet model, with the additional
consideration of a lipid membrane separating two fluids of arbitrary
properties. For the latter, both a membrane-charging and a membrane-mechanical
model are supplied. The vesicle is assumed to remain spheroidal in shape for
all times. The main result is an ODE governing the evolution of the vesicle
aspect ratio. The effects of initial membrane tension and pulse length are
examined. The model prediction is extensively compared with experimental data,
and is shown to accurately capture the system behavior in the regime of no or
weak electroporation. More importantly, the comparison reveals that vesicle
relaxation obeys a universal behavior regardless of the means of deformation.
The process is governed by a single timescale that is a function of the vesicle
initial radius, the fluid viscosity, and the initial membrane tension. This
universal scaling law can be used to calculate membrane properties from
experimental data
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