15,040 research outputs found
Electron Monte Carlo Simulations of Nanoporous Si Thin Films -- The Influence of Pore-Edge Charges
Electron transport within nanostructures can be important to varied
engineering applications, such as thermoelectrics and nanoelectronics. In
theoretical studies, electron Monte Carlo simulations are widely used as an
alternative approach to solving the electron Boltzmann transport equation,
where the energy-dependent electron scattering, exact structure shape, and
detailed electric field distribution can be fully incorporated. In this work,
such electron Monte Carlo simulations are employed to predict the electrical
conductivity of periodic nanoporous Si films that have been widely studied for
thermoelectric applications. The focus is on the influence of pore-edge charges
on the electron transport. The results are further compared to our previous
modeling [Hao et al., J. Appl. Phys. 121, 094308 (2017)], where the pore-edge
electric field has its own scattering rate to be added to the scattering rates
of other mechanisms
A Cosmic Selection Rule for Glueball Dark Matter Relic Density
We point out a unique mechanism to produce the relic abundance for glueball
dark matter from a gauged hidden sector which is bridged to the
standard model sector through heavy vectorlike quarks colored under gauge
interactions from both sides. A necessary ingredient of our assumption is that
the vectorlike quarks, produced either thermally or non-thermally, are abundant
enough to dominate the universe for some time in the early universe. They later
undergo dark color confinement and form unstable vectorlike-quarkonium states
which annihilate decay and reheat the visible and dark sectors. The ratio of
entropy dumped into two sectors and the final energy budget in the dark
glueballs is only determined by low energy parameters, including the intrinsic
scale of the dark , , and number of dark colors, , but
depend weakly on parameters in the ultraviolet such as the vectorlike quark
mass or the initial condition. We call this a cosmic selection rule for the
glueball dark matter relic density.Comment: 7 pages, 3 figures; v2 references added; v3 published versio
Performance Analysis of a Low-Interference N-Continuous OFDM Scheme
This paper investigates two issues of power spectrum density (PSD) and bit
error rate (BER) of an N-continuous orthogonal frequency division multiplexing
(NC-OFDM) aided low-interference time-domain scheme, when the smooth signal is
designed by the linear combination of basis signals truncated by a window.
Based on the relationship between the continuity and sidelobe decaying, the PSD
performance is first analyzed and compared, in terms of the highest derivative
order (HDO) N and the length of the smooth signal L. Since the high-order
derivative of the truncation window has the finite continuity, the N-continuous
signal has two finite continuities, which may have different continuous
derivative orders. In this case, we develop a close PSD expression by
introducing another smooth signal, which is also linearly combined by other
basis signals, to explain the sidelobe decaying related to N and L. Then, in
the context of BER, considering the multipath Rayleigh fading channel, based on
the effect of the delayed tail of the smooth signal to the received signal, we
provide a procedure for calculating the BER expressed in the form of an
asymptotic summation.Comment: 7 pages, 6 figure
Gravitational waves with dark matter minispikes: the combined effect
It was shown that the dark matter(DM) minihalo around an intermediate mass
black hole(IMBH) can be redistributed into a cusp, called the DM minispike. We
consider an intermediate-mass-ratio inspiral consisting of an IMBH harbored in
a DM minispike with nonannihilating DM particles and a small black hole(BH)
orbiting around it. We investigate gravitational waves(GWs) produced by this
system and analyze the waveforms with the comprehensive consideration of
gravitational pull, dynamical friction and accretion of the minispike and
calculate the time difference and phase difference caused by it. We find that
for a certain range of frequency, the inspiralling time of the system is
dramatically reduced for smaller central IMBH and large density of DM. For the
central IMBH with , the time of merger is ahead, which can be
distinguished by LISA, Taiji and Tianqin. We focus on the effect of accretion
and compare it with that of gravitational pull and friction. We find that the
accretion mass is a small quantity compared to the initial mass of the small BH
and the accretion effect is inconspicuous compared with friction. However, the
accumulated phase shift caused by accretion is large enough to be detected by
LISA, Taiji and Tianqin, which indicate that the accretion effect can not be
ignored in the detection of GWs.Comment: 10 pages, 14 figure
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