5,923 research outputs found
Modeling the IDV emissions of the BL Lac Objects with a Langevin type stochastic differential equation
In this paper, we introduce a simplified model for explaining the
observations of the optical intraday variability (IDV) of the BL Lac Objects.
We assume that the source of the IDV are the stochastic oscillations of an
accretion disk around a supermassive black hole. The Stochastic Fluctuations on
the vertical direction of the accretion disk are described by using a Langevin
type equation with a damping term and a random, white noise type force.
Furthermore, the preliminary numerical simulation results are presented, which
are based on the numerical analysis of the Langevin stochastic differential
equation.Comment: 4 pages, 4 figures, accepted for publication in J. Astrophys. Ast
Is the Convergence of Accounting Standards Good for Stock Markets?
This paper examines the impact of the convergence of Hong Kong Accounting Standard 40 (HKAS 40) with the International Financial Reporting Standard (IFRS) on the stock prices of firms in the property industry. Using a sample of 22111 firm-day observations, we show that the new standard has a negative impact on the stock performance of these firms.Hong Kong Accounting Standard 40, Event Window, Stock Return.
Heuristic derivation of continuum kinetic equations from microscopic dynamics
We present an approximate and heuristic scheme for the derivation of
continuum kinetic equations from microscopic dynamics for stochastic,
interacting systems. The method consists of a mean-field type, decoupled
approximation of the master equation followed by the `naive' continuum limit.
The Ising model and driven diffusive systems are used as illustrations. The
equations derived are in agreement with other approaches, and consequences of
the microscopic dependences of coarse-grained parameters compare favorably with
exact or high-temperature expansions. The method is valuable when more
systematic and rigorous approaches fail, and when microscopic inputs in the
continuum theory are desirable.Comment: 7 pages, RevTeX, two-column, 4 PS figures include
Multi-wavelength emissions from the millisecond pulsar binary PSR J1023+0038 during an accretion active state
Recent observations strongly suggest that the millisecond pulsar binary PSR
J1023+0038 has developed an accretion disk since 2013 June. We present a
multi-wavelength analysis of PSR J1023+0038, which reveals that 1) its
gamma-rays suddenly brightened within a few days in June/July 2013 and has
remained at a high gamma-ray state for several months; 2) both UV and X-ray
fluxes have increased by roughly an order of magnitude, and 3) the spectral
energy distribution has changed significantly after the gamma-ray sudden flux
change. Time variabilities associated with UV and X-rays are on the order of
100-500 seconds and 50-100 seconds, respectively. Our model suggests that a
newly formed accretion disk due to the sudden increase of the stellar wind
could explain the changes of all these observed features. The increase of UV is
emitted from the disk, and a new component in gamma-rays is produced by inverse
Compton scattering between the new UV component and pulsar wind. The increase
of X-rays results from the enhancement of injection pulsar wind energy into the
intra-binary shock due to the increase of the stellar wind. We also predict
that the radio pulses may be blocked by the evaporated winds from the disk and
the pulsar is still powered by rotation.Comment: 8 pages, 3 figures; accepted for publication in Ap
Non-equilibrium stationary state of a two-temperature spin chain
A kinetic one-dimensional Ising model is coupled to two heat baths, such that
spins at even (odd) lattice sites experience a temperature ().
Spin flips occur with Glauber-type rates generalised to the case of two
temperatures. Driven by the temperature differential, the spin chain settles
into a non-equilibrium steady state which corresponds to the stationary
solution of a master equation. We construct a perturbation expansion of this
master equation in terms of the temperature difference and compute explicitly
the first two corrections to the equilibrium Boltzmann distribution. The key
result is the emergence of additional spin operators in the steady state,
increasing in spatial range and order of spin products. We comment on the
violation of detailed balance and entropy production in the steady state.Comment: 11 pages, 1 figure, Revte
Transient sensitivity of sectorial split-drain magnetic field-effect transistor
published_or_final_versio
Analytical Results for a Hole in an Antiferromagnet
The Green's function for a hole moving in an antiferromagnet is derived
analytically in the long-wavelength limit. We find that the infrared divergence
is eliminated in two and higher dimensions so that the quasiparticle weight is
finite. Our results also suggest that the hole motion is polaronic in nature
with a bandwidth proportional to ( is a constant).
The connection of the long-wavelength approximation to the first-order
approximation in the cumulant expansion is also clarified.Comment: 12 papes, 2 figures available upon request, revte
Shake-induced order in nanosphere systems
Self-assembled patterns obtained from a drying nanosphere suspension are
investigated by computer simulations and simple experiments. Motivated by the
earlier experimental results of Sasaki and Hane and Schope, we confirm that
more ordered triangular lattice structures can be obtained whenever a moderate
intensity random shaking is applied on the drying system. Computer simulations
are realized on an improved version of a recently elaborated
Burridge-Knopoff-type model. Experiments are made following the setup of Sasaki
and Hane, using ultrasonic radiation as source for controlled shaking.Comment: 7 pages, 10 figure
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