248 research outputs found
Unified Gas-kinetic Wave-Particle Methods III: Multiscale Photon Transport
In this paper, we extend the unified gas-kinetic wave-particle (UGKWP) method
to the multiscale photon transport. In this method, the photon free streaming
and scattering processes are treated in an un-splitting way. The duality
descriptions, namely the simulation particle and distribution function, are
utilized to describe the photon. By accurately recovering the governing
equations of the unified gas-kinetic scheme (UGKS), the UGKWP preserves the
multiscale dynamics of photon transport from optically thin to optically thick
regime. In the optically thin regime, the UGKWP becomes a Monte Carlo type
particle tracking method, while in the optically thick regime, the UGKWP
becomes a diffusion equation solver. The local photon dynamics of the UGKWP, as
well as the proportion of wave-described and particle-described photons are
automatically adapted according to the numerical resolution and transport
regime. Compared to the -type UGKS, the UGKWP requires less memory cost
and does not suffer ray effect. Compared to the implicit Monte Carlo (IMC)
method, the statistical noise of UGKWP is greatly reduced and computational
efficiency is significantly improved in the optically thick regime. Several
numerical examples covering all transport regimes from the optically thin to
optically thick are computed to validate the accuracy and efficiency of the
UGKWP method. In comparison to the -type UGKS and IMC method, the UGKWP
method may have several-order-of-magnitude reduction in computational cost and
memory requirement in solving some multsicale transport problems.Comment: 27 pages, 15 figures. arXiv admin note: text overlap with
arXiv:1810.0598
Revisit to Non-decoupling MSSM
Dipole operator requires the helicity
flip in the involving quark states thus the breaking of chiral . On the other hand, the -quark mass generation is also a
consequence of chiral symmetry breaking. Therefore,
in many models, there might be strong correlation between the
and quark Yukawa coupling. We use non-decoupling MSSM model to illustrate
this feature. The light Higgs boson may evade the direct search experiments at
LEPII or Tevatron while the 125 GeV Higgs-like boson is identified as the heavy
Higgs boson in the spectrum. A light charged Higgs is close to the heavy Higgs
boson which is of 125 GeV and its contribution to requires
large supersymmetric correction with large PQ and symmetry breaking. The
large supersymmetric contribution at the same time significantly modifies the
quark Yukawa co upling. With combined flavor constraints
and and direct constraints on Higgs properties, we
find best fit scenarios with light stop of (500 GeV), negative
around -750 GeV and large -term of 2-3 TeV. In addition, reduction in
partial width may also result in large enhancement of
decay branching fraction. Large parameter region in the survival space under
all bounds may be further constrained by if no excess of
is confirmed at LHC. We only identify a small parameter region with
significant decay that is consistent with all bounds and reduced
decay branching fraction.Comment: 18pages, 6 figure
Spin-dependent sub-GeV Inelastic Dark Matter-electron scattering and Migdal effect: (I). Velocity Independent Operator
The ionization signal provide an important avenue of detecting light dark
matter. In this work, we consider the sub-GeV inelastic dark matter and use the
non-relativistic effective field theory (NR-EFT) to derive the constraints on
the spin-dependent DM-electron scattering and DM-nucleus Migdal scattering.
Since the recoil electron spectrum of sub-GeV DM is sensitive to tails of
galactic DM velocity distributions, we also compare the bounds on corresponding
scattering cross sections in Tsallis, Empirical and standard halo models. With
the XENON1T data, we find that the exclusion limits of the DM-proton/neutron
and DM-electron scattering cross sections for exothermic inelastic DM are much
stronger that those for the endothermic inelastic DM. Each limits of the
endothermic inelastic DM can differ by an order of magnitude at most in three
considered DM velocity distributions.Comment: 36 pages, 7 figure
Gamma-rays from Nearby Clusters: Constraints on Selected Decaying Dark Matter Models
Recently, the Fermi-LAT collaboration reported upper limits on the GeV
gamma-ray flux from nearby clusters of galaxies. Motivated by these limits, we
study corresponding constraints on gamma-ray emissions from two specific
decaying dark matter models, one via grand unification scale suppressed
operators and the other via R-parity violating operators. Both can account for
the PAMELA and Fermi-LAT excesses of e^\pm. For GUT decaying dark matter, the
gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to
10 GeV, lead to the most stringent constraints to date. As a result, this dark
matter is disfavored with conventional model of e^\pm background. In addition,
it is likely that some tension exists between the Fermi-LAT e^\pm excess and
the gamma ray constraints for any decaying dark matter model, provided
conventional model of e^\pm background is adopted. Nevertheless, the GUT
decaying dark matter can still solely account for the PAMELA positron fraction
excess without violating the gamma-ray constraints. For the gravitino dark
matter model with R-parity violation, cluster observations do not give tight
constraints. This is because a different e^\pm background has been adopted
which leads to relatively light dark matter mass around 200 GeV.Comment: 17 pages, 4 figures, version to appear in Phys. Lett.
Ion Channels in Epilepsy: Blasting Fuse for Neuronal Hyperexcitability
Voltage-gated ion channels (VGICs), extensively distributed in the central nervous system (CNS), are responsible for the generation as well as modulation of neuroexcitability and considered as vital players in the pathogenesis of human epilepsy, with regulating the shape and duration of action potentials (APs). For instance, genetic alterations or abnormal expression of voltage-gated sodium channels (VGSCs), Kv channels, and voltage-gated calcium channels (VGCCs) are proved to be associated with epileptogenesis. This chapter aims to highlight recent discoveries on the mutations in VGIC genes and dysfunction of VGICs in epilepsy, especially focusing on the pathophysiological and pharmacological properties. Understanding the role of epilepsy-associated VGICs might not only contribute to clarify the mechanism of epileptogenesis and genetic modifiers but also provide potential targets for the precise treatment of epilepsy
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