24,601 research outputs found
Determining Ratios of WIMP-Nucleon Cross Sections from Direct Dark Matter Detection Data
Weakly Interacting Massive Particles (WIMPs) are one of the leading
candidates for Dark Matter. So far the usual procedure for constraining the
WIMP-nucleon cross sections in direct Dark Matter detection experiments have
been to fit the predicted event rate based on some model(s) of the Galactic
halo and of WIMPs to experimental data. One has to assume whether the
spin-independent (SI) or the spin-dependent (SD) WIMP-nucleus interaction
dominates, and results of such data analyses are also expressed as functions of
the as yet unknown WIMP mass. In this article, I introduce methods for
extracting information on the WIMP-nucleon cross sections by considering a
general combination of the SI and SD interactions. Neither prior knowledge
about the local density and the velocity distribution of halo WIMPs nor about
their mass is needed. Assuming that an exponential-like shape of the recoil
spectrum is confirmed from experimental data, the required information are only
the measured recoil energies (in low energy ranges) and the number of events in
the first energy bin from two or more experiments.Comment: 33 pages, 20 eps figures; v2: typos fixed, references added and
updated, revised version for publicatio
Entanglement dynamics of two-qubit system in different types of noisy channels
In this paper, we study entanglement dynamics of a two-qubit extended
Werner-like state locally interacting with independent noisy channels, i.e.,
amplitude damping, phase damping and depolarizing channels. We show that the
purity of initial entangled state has direct impacts on the entanglement
robustness in each noisy channel. That is, if the initial entangled state is
prepared in mixed instead of pure form, the state may exhibit entanglement
sudden death (ESD) and/or be decreased for the critical probability at which
the entanglement disappear.Comment: 11 pages, 6 figure
Multipartite Entanglement Measure
In this paper, we generalize the residual entanglement to the case of
multipartite states in arbitrary dimensions by making use of a new method.
Through the introduction of a special entanglement measure, the residual
entanglement of mixed states takes on a form that is more elegant than that in
Ref.[7] (Phys.Rev.A 61 (2000) 052306) . The result obtained in this paper is
different from the previous one given in Ref.[8] (Phys.Rev.A 63 (2000) 044301).
Several examples demonstrate that our present result is a good measurement of
the multipartite entanglement. Furthermore, the original residual entanglement
is a special case of our result.Comment: 5 page
Determining the Mass of Dark Matter Particles with Direct Detection Experiments
In this article I review two data analysis methods for determining the mass
(and eventually the spin-independent cross section on nucleons) of Weakly
Interacting Massive Particles with positive signals from direct Dark Matter
detection experiments: a maximum likelihood analysis with only one experiment
and a model-independent method requiring at least two experiments.
Uncertainties and caveats of these methods will also be discussed.Comment: 24 pages, 10 figures, 1 reference added, typos fixed, published
version, to appear in the NJP Focus Issue on "Dark Matter and Particle
Physics
Combining Supply and Demand Estimates for Ecosystem Services from Cropland
Payment-for-Ecosystem-Services (PES) programs are gaining appeal as flexible approaches to inducing the voluntary provision of ecosystem services (ES). Farmers, who manage agricultural ecosystems, provide important nonmarket ecosystem services to the public by their choice of production inputs and management practices. Although there exist various PES programs in the United States and Europe, we are aware of none that was designed based on a comprehensive understanding of the underlying supply and demand of ecosystem services. Taking advantage of unique, coupled datasets of stated preferences, this paper combines a supply-side cost function of farmers’ willingness to adopt practices that provide increased ES with a demand-side social benefit function of residents’ willingness to pay (WTP) for these ES. The result is an empirically based, welfare-maximizing price and quantity of ES that can inform the design of future PES programs.Payment-for-Ecosystem-Services (PES), Contingent valuation, Aggregate supply and demand, Cropland, Eutrophication, Greenhouse gas, Agricultural and Food Policy, Environmental Economics and Policy, Q11, Q51, Q57, Q58,
Improved Spin Dynamics Simulations of Magnetic Excitations
Using Suzuki-Trotter decompositions of exponential operators we describe new
algorithms for the numerical integration of the equations of motion for
classical spin systems. These techniques conserve spin length exactly and, in
special cases, also conserve the energy and maintain time reversibility. We
investigate integration schemes of up to eighth order and show that these new
algorithms can be used with much larger time steps than a well established
predictor-corrector method. These methods may lead to a substantial speedup of
spin dynamics simulations, however, the choice of which order method to use is
not always straightforward.Comment: J. Mod. Phys. C (in press
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