20,748 research outputs found
Background effects on reconstructed WIMP couplings
In this talk, I presented effects of small, but non-negligible unrejected
background events on the determinations of WIMP couplings/cross sections.Comment: 4 pages, 5 eps figures, to appear in the proceedings of the 12th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP 2011), September 5-9, 2011, Munich, German
Study of mechanical response in embossing of ceramic green substrate by micro-indentation
Micro-indentation test with a micro flat-end cone indenter was employed to
simulate micro embossing process and investigate the thermo-mechanical response
of ceramic green substrates. The laminated low temperature co-fired ceramic
green tapes were used as the testing material ; the correlations of indentation
depth versus applied force and applied stress at the temperatures of 25 degrees
C and 75degrees C were studied. The results showed that permanent indentation
cavities could be formed at temperatures ranging from 25 degrees C to 75
degrees C, and the depth of cavities created was applied force, temperature and
dwell time dependent. Creep occurred and made a larger contribution to the
plastic deformation at elevated temperatures and high peak loads. There was
instantaneous recovery during the unloading and retarded recovery in the first
day after indentation. There was no significant pile-up due to material flow
observed under compression at the temperature up to 75 degrees C. The plastic
deformation was the main cause for formation of cavity on the ceramic green
substrate under compression. The results can be used as a guideline for
embossing ceramic green substrates.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
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
Structural comparison of nickel electrodes and precursor phases
A summary of previous Raman spectroscopic results and a discussion of important structural differences in the various phases of active mass and active mass precurors are presented. Raman spectra provide unique signatures for these phases, and allow one to distinguish each phase, even when the compound is amorphous to X-rays (i.e., does not scatter X-rays because of a lack of order and/or small particle size). The structural changes incurred during formation, charge and discharge, cobalt addition, and aging will be discussed and related to electrode properties. Important structural differences include NiO2 layer stacking, nonstoichiometry (especially cation-deficit nonstoichiometry), disorder, dopant content, and water content. The results indicate that optimal nickel active mass is non-close packed and nonstoichiometric. The formation process transforms precursor phases into this structure. Therefore, the precursor disorder, or lack thereof, influences this final active mass structure and the rate of formation. Aging processes induce structural change which is believed to be detrimental. The role of cobalt addition can be appreciated in terms of structures favored or stabilized by the dopant. In recent work, the in situ Raman technique to characterize the critical structural parameters was developed. An in situ method relates structure, electrochemistry, and preparation. In situ Raman spectra of cells during charge and discharge, either during cyclic voltammetry or under constant current conditions were collected. With the structure-preparation knowledge and the in situ Raman tool, it will be possible to define the structure-property-preparation relations in more detail. This instrumentation has application to a variety of electrode systems
Analyzing direct dark matter detection data with unrejected background events by the AMIDAS website
In this talk I have presented the data analysis results of extracting
properties of halo WIMPs: the mass and the (ratios between the)
spin-independent and spin-dependent couplings/cross sections on nucleons by the
AMIDAS website by taking into account possible unrejected background events in
the analyzed data sets. Although non-standard astronomical setup has been used
to generate pseudodata sets for our analyses, it has been found that, without
prior information/assumption about the local density and velocity distribution
of halo Dark Matter, these WIMP properties have been reconstructed with ~ 2% to
<~ 30% deviations from the input values.Comment: 9 pages, 10 eps figures, 1 table, to appear in the proceedings of the
Seventh International Workshop on the Dark Side of the Universe (DSU 2011),
September 26-30, 2011, Beijing, Chin
Holographic Heat Current as Noether Current
We employ the Noether procedure to derive a general formula for the radially
conserved heat current in AdS planar black holes with certain transverse and
traceless perturbations, for a general class of gravity theories. For Einstein
gravity, the general higher-order Lovelock gravities and also a class of
Horndeski gravities, we derive the boundary stress tensor and show that the
resulting boundary heat current matches precisely the bulk Noether current.Comment: Latex, 27 pages, typos corrected, comments added, references adde
Thermodynamics of Einstein-Proca AdS Black Holes
We study static spherically-symmetric solutions of the Einstein-Proca
equations in the presence of a negative cosmological constant. We show that the
theory admits solutions describing both black holes and also solitons in an
asymptotically AdS background. Interesting subtleties can arise in the
computation of the mass of the solutions and also in the derivation of the
first law of thermodynamics. We make use of holographic renormalisation in
order to calculate the mass, even in cases where the solutions have a rather
slow approach to the asymptotic AdS geometry. By using the procedure developed
by Wald, we derive the first law of thermodynamics for the black hole and
soliton solutions. This includes a non-trivial contribution associated with the
Proca "charge." The solutions cannot be found analytically, and so we make use
of numerical integration techniques to demonstrate their existence.Comment: 35 pages, Improved discussion of cases with logarithmic asymptotic
fall off
Generalised Smarr Formula and the Viscosity Bound for Einstein-Maxwell-Dilaton Black Holes
We study the shear viscosity to entropy ratio in the boundary field
theories dual to black hole backgrounds in theories of gravity coupled to a
scalar field, and generalisations including a Maxwell field and non-minimal
scalar couplings. Motivated by the observation in simple examples that the
saturation of the bound is correlated with the existence
of a generalised Smarr relation for the planar black-hole solutions, we
investigate this in detail for the general black-hole solutions in these
theories, focusing especially on the cases where the scalar field plays a
non-trivial role and gives rise to an additional parameter in the space of
solutions. We find that a generalised Smarr relation holds in all cases, and in
fact it can be viewed as the bulk gravity dual of the statement of the
saturation of the viscosity to entropy bound. We obtain the generalised Smarr
relation, whose existence depends upon a scaling symmetry of the planar
black-hole solutions, by two different but related methods, one based on
integrating the first law of thermodynamics, and the other based on the
construction of a conserved Noether charge.Comment: Latex, 36 pages, references added, typos corrected, to appear in PR
Magnetically-Charged Black Branes and Viscosity/Entropy Ratios
We consider asymptotically-AdS -dimensional black brane solutions in a
theory of gravity coupled to a set of -form field strengths, in which
the field strengths carry magnetic charges. For appropriately chosen charges,
the metrics are isotropic in the transverse directions. However, in
general the field strength configurations break the full Euclidean symmetry of
the -dimensional transverse space. We then study the linearised equation
for transverse traceless metric perturbations in these backgrounds, and by
employing the Kubo formula we obtain expressions for , the ratio of
shear viscosity to entropy density. We find that the KSS bound on the ratio
is generally violated in these solutions. We also extend the
discussion by including also a dilatonic scalar field in the theory, leading to
solutions that are asymptotically Lifshitz with hyperscaling violation.Comment: References added. 21 page
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