4,287 research outputs found
Cosmic e^\pm, \bar p, \gamma and neutrino rays in leptocentric dark matter models
Dark matter annihilation is one of the leading explanations for the recently
observed excesses in cosmic rays by PAMELA, ATIC, FERMI-LAT and HESS.
Any dark matter annihilation model proposed to explain these data must also
explain the fact that PAMELA data show excesses only in spectrum but
not in anti-proton. It is interesting to ask whether the annihilation mode into
anti-proton is completely disallowed or only suppressed at low energies. Most
models proposed have negligible anti-protons in all energy ranges. We show that
the leptocentric dark matter model can explain the
excesses with suppressed anti-proton mode at low energies, but at higher
energies there are sizable anti-proton excesses. Near future data from PAMELA
and AMS can provide crucial test for this type of models. Cosmic ray
data can further rule out some of the models. We also show that this model has
interesting cosmic neutrino signatures.Comment: Latex 20 pages and five figures. References adde
Combination of Multiple Bipartite Ranking for Web Content Quality Evaluation
Web content quality estimation is crucial to various web content processing
applications. Our previous work applied Bagging + C4.5 to achive the best
results on the ECML/PKDD Discovery Challenge 2010, which is the comibination of
many point-wise rankinig models. In this paper, we combine multiple pair-wise
bipartite ranking learner to solve the multi-partite ranking problems for the
web quality estimation. In encoding stage, we present the ternary encoding and
the binary coding extending each rank value to (L is the number of the
different ranking value). For the decoding, we discuss the combination of
multiple ranking results from multiple bipartite ranking models with the
predefined weighting and the adaptive weighting. The experiments on ECML/PKDD
2010 Discovery Challenge datasets show that \textit{binary coding} +
\textit{predefined weighting} yields the highest performance in all four
combinations and furthermore it is better than the best results reported in
ECML/PKDD 2010 Discovery Challenge competition.Comment: 17 pages, 8 figures, 2 table
Entanglement entropy of critical spin liquids
Quantum spin liquids are phases of matter whose internal structure is not
captured by a local order parameter. Particularly intriguing are critical spin
liquids, where strongly interacting excitations control low energy properties.
Here we calculate their bipartite entanglement entropy that characterize their
quantum structure. In particular we calculate the Renyi entropy , on model
wavefunctions obtained by Gutzwiller projection of a Fermi sea. Although the
wavefunctions are not sign positive, can be calculated on relatively
large systems (>324 spins), using the variational Monte Carlo technique. On the
triangular lattice we find that entanglement entropy of the projected Fermi-sea
state violates the boundary law, with enhanced by a logarithmic factor.
This is an unusual result for a bosonic wave-function reflecting the presence
of emergent fermions. These techniques can be extended to study a wide class of
other phases.Comment: 4+ pages, 2 figures, to be published in PR
Infinite critical boson non-Fermi liquid on heterostructure interfaces
We study the emergence of non-Fermi liquid on heterostructure interfaces
where there exists an infinite number of critical boson modes accounting for
the magnetic fluctuations in two spatial dimensions. The interfacial
Dzyaloshinskii-Moriya interaction naturally arises in magnetic interactions due
to the absence of inversion symmetry, resulting in a degenerate contour for the
low-energy bosonic modes in the momentum space which simultaneously becomes
critical near the magnetic phase transition. The itinerant electrons are
scattered by the critical boson contour via the Yukawa coupling. When the boson
contour is much smaller than the Fermi surface, it is shown that, there exists
a regime with a dynamic critical exponent z=3 while the boson contour still
controls the low-energy magnetic fluctuations. Using a self-consistent
renormalization calculation for this regime, we uncover a prominent non-Fermi
liquid behavior in the resistivity with a characteristic temperature scaling
power. These findings open up new avenues for understanding boson-fermion
interactions and the novel fermionic quantum criticality.Comment: 17 pages(with Appendix), 7 figure
The System Dynamics Model in Electronic Products Closed-Loop Supply Chain Distribution Network with Three-Way Recovery and the Old-for-New Policy
With the technological developments and rapid changes in demand pattern, diverse varieties of electronic products are entering into the market with reduced lifecycle which leads to the environmental problems. The awareness of electronic products take-back and recovery has been increasing in electronic products supply chains. In this paper, we build a system dynamics model for electronic products closed-loop supply chain distribution network with the old-for-new policy and three electronic products recovery ways, namely, electronic products remanufacturing, electronic component reuse and remanufacturing, and electronic raw material recovery. In the simulation study, we investigate the significance of various factors including the old-for-new policy, collection and remanufacturing, their interactions and the type of their impact on bullwhip, and profitability through sensitivity analysis. Our results instruct that the old-for-new policy and three electronic products recovery ways can reduce the bullwhip effect in the retailers and the distributors and increases the profitability in the closed-loop supply chain distribution network
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