2,292 research outputs found
Thermal Bremsstrahlung Radiation in a Two-Temperature Plasma
In the normal one-temperature plasma the motion of ions is usually neglected
when calculating the Bremsstrahlung radiation of the plasma. Here we calculate
the Bremsstrahlung radiation of a two-temperature plasma by taking into account
of the motion of ions. Our results show that the total radiation power is
always lower if the motion of ions is considered. We also apply the
two-temperature Bremsstrahlung radiation mechanism for an analytical
Advection-Dominated Accretion Flow (ADAF) model; we find the two-temperature
correction to the total Bremsstrahlung radiation for ADAF is negligible.Comment: 5 pages, 4 figures, accepted for publication in CHJAA. Some
discussions and references adde
Strong Aperiodic X-ray Variability and Quasi-Periodic Oscillation in X-ray Nova XTE J1550-564
We report the discovery of strong aperiodic X-ray variability and
quasi-periodic oscillation (QPO) in the X-ray light curves of a new X-ray Nova,
XTE J1550-564, and the evolution of the observed temporal properties during the
rise of the recent X-ray outburst. The power spectral analysis of the first
observation reveals strong aperiodic X-ray variability of the source (~28%), as
well as the presence of a QPO at ~82 mHz with fractional rms amplitude ~14%
over the 2-60 keV energy range. Also apparent is the first harmonic of the QPO
with the amplitude ~9%. As the X-ray flux increases, the source tends to become
less variable, and the QPO frequency increases rapidly, from 82 mHz to 4 Hz,
over the flux (2-50 keV) range of 1.73-5.75 x 10^{-8} ergs cm^{-2} s^{-1}. The
amplitude of the fundamental component of the QPO varies little, while that of
the harmonic follows a decreasing trend. The fundamental component strengthens
toward high energies, while its harmonic weakens. Initially, the power spectrum
is roughly flat at low frequencies and turns into a power law at high
frequencies, with the QPO harmonic sitting roughly at the break. In later
observations, however, the high-frequency portion of the continuum can actually
be better described by a broken power law (as opposed to a simple power law).
This effect becomes more apparent at higher energies. The overall amplitude of
the continuum shows a similar energy dependence to that of the fundamental
component of the QPO. Strong rapid X-ray variability, as well as hard energy
spectrum, makes XTE J1550-564 a good black hole candidate. We compare its
temporal properties with those of other black hole candidates.Comment: 12 pages, including 5 figures. To appear in ApJ Letters, vol. 512
(1999
On the uniqueness of the non-minimal matter coupling in massive gravity and bigravity
In de Rham-Gabadadze-Tolley (dRGT) massive gravity and bigravity, a
non-minimal matter coupling involving both metrics generically re-introduces
the Boulware--Deser (BD) ghost. A non-minimal matter coupling via a simple, yet
specific composite metric has been proposed, which eliminates the BD ghost
below the strong coupling scale. Working explicitly in the metric formulation
and for arbitrary spacetime dimensions, we show that this composite metric is
the unique consistent non-minimal matter coupling below the strong coupling
scale, which emerges out of two diagnostics, namely, absence of Ostrogradski
ghosts in the decoupling limit and absence of the BD ghost from matter quantum
loop corrections.Comment: v2: references added, matches accepted version in Physics Letters B
v1: 6 pages, two-colum
Comparison between Windowed FFT and Hilbert-Huang Transform for Analyzing Time Series with Poissonian Fluctuations: A Case Study
Hilbert-Huang Transform (HHT) is a novel data analysis technique for
nonlinear and non-stationary data. We present a time-frequency analysis of both
simulated light curves and an X-ray burst from the X-ray burster 4U 1702-429
with both the HHT and the Windowed Fast Fourier Transform (WFFT) methods. Our
results show that the HHT method has failed in all cases for light curves with
Poissonian fluctuations which are typical for all photon counting instruments
used in astronomy, whereas the WFFT method can sensitively detect the periodic
signals in the presence of Poissonian fluctuations; the only drawback of the
WFFT method is that it cannot detect sharp frequency variations accurately.Comment: 10 pages, 12 figure
Light-Switchable Polymer Adhesive Based on Photoinduced Reversible Solid-to-Liquid Transitions
Hawking radiation from the Schwarzschild black hole with a global monopole via gravitational anomaly
Hawking flux from the Schwarzschild black hole with a global monopole is
obtained by using Robinson and Wilczek's method. Adopting a dimension reduction
technique, the effective quantum field in the (3+1)--dimensional global
monopole background can be described by an infinite collection of the
(1+1)--dimensional massless fields if neglecting the ingoing modes near the
horizon, where the gravitational anomaly can be cancelled by the
(1+1)--dimensional black body radiation at the Hawking temperature.Comment: 4 pages, no figure, 3nd revsion with one reference adde
HINT: High-quality INpainting Transformer with Mask-Aware Encoding and Enhanced Attention
Existing image inpainting methods leverage convolution-based downsampling approaches to reduce spatial dimensions. This may result in information loss from corrupted images where the available information is inherently sparse, especially for the scenario of large missing regions. Recent advances in self-attention mechanisms within transformers have led to significant improvements in many computer vision tasks including inpainting. However, limited by the computational costs, existing methods cannot fully exploit the efficacy of long-range modelling capabilities of such models. In this paper, we propose an end-to-end High-quality INpainting Transformer, abbreviated as HINT, which consists of a novel mask-aware pixel-shuffle downsampling module (MPD) to preserve the visible information extracted from the corrupted image while maintaining the integrity of the information available for highlevel inferences made within the model. Moreover, we propose a Spatially-activated Channel Attention Layer (SCAL), an efficient self-attention mechanism interpreting spatial awareness to model the corrupted image at multiple scales. To further enhance the effectiveness of SCAL, motivated by recent advanced in speech recognition, we introduce a sandwich structure that places feed-forward networks before and after the SCAL module. We demonstrate the superior performance of HINT compared to contemporary state-of-the-art models on four datasets, CelebA, CelebA-HQ, Places2, and Dunhuang
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