3,909 research outputs found
Secondary emission conductivity of high purity silica fabric
High purity silica fabrics were proposed for use as a material to control the effects of electrostatic charging of satellites at synchronous altitudes. These materials exhibited very quiet behavior when placed in simulated charging environments as opposed to other dielectrics used for passive thermal control which exhibit varying degrees of electrical arcing. Secondary emission conductivity is proposed as a mechanism for this superior behavior. Design of experiments to measure this phenomena and data taken on silica fabrics are discussed as they relate to electrostatic discharge (ESD) control on geosynchronous orbit spacecraft. Studies include the apparent change in resistivity of the material as a function of the electron beam energy, flux intensity, and the effect of varying electric fields impressed across the material under test
Isospin-violating dark matter from a double portal
We study a simple model that can give rise to isospin-violating interactions
of Dirac fermion asymmetric dark matter to protons and neutrons through the
interference of a scalar and U(1) gauge boson contribution. The model can
yield a large suppression of the elastic scattering cross section off Xenon
relative to Silicon thus reconciling CDMS-Si and LUX results while being
compatible with LHC findings on the 126 GeV Higgs, electroweak precision tests
and flavour constraints.Comment: 25 pages, 7 figure
All we need is the candidate’s face: the irrelevance of information about political coalition affiliation and campaign promises
Recent research has indicated that judgments of competence based on very short exposure to political candidates' faces reliably predict electoral success. An unexplored question is whether presenting written information of the kind to which voters are typically exposed during an election alongside candidates' faces affects competence judgments. We conducted three studies using photographs of 16 pairs of competing politicians in 16 medium-sized towns of northeast Italy as stimuli. Study 1 confirmed the external validity of earlier research in which participants were exposed to candidates' faces without providing any other information. Study 2a showed that competence judgments were not subject to in-group favoritism: candidates' faces were presented alongside information about the political coalition to which they belonged (center left; center right) to participants who declared a left or right political orientation. Finally, Study 2c compared the competence inferences made in Study 1 (face-only condition) with those of Study 2a (face plus political coalition label) and with new inferences (Study 2b) based on candidates' faces plus information about campaign promises (greater equality; lower taxes). The results showed that automatic competence inferences are not substantially modified when relevant written information is presented alongside candidates' faces
Equilibrium random-field Ising critical scattering in the antiferromagnet Fe(0.93)Zn(0.07)F2
It has long been believed that equilibrium random-field Ising model (RFIM)
critical scattering studies are not feasible in dilute antiferromagnets close
to and below Tc(H) because of severe non-equilibrium effects. The high magnetic
concentration Ising antiferromagnet Fe(0.93)Zn(0.07)F2, however, does provide
equilibrium behavior. We have employed scaling techniques to extract the
universal equilibrium scattering line shape, critical exponents nu = 0.87 +-
0.07 and eta = 0.20 +- 0.05, and amplitude ratios of this RFIM system.Comment: 4 pages, 1 figure, minor revision
Monte Carlo Simulation of Ising Models with Dipole Interaction
Recently, a new memory effect was found in the metamagnetic domain structure
of the diluted Ising antiferromagnet by domain imaging
with Faraday contrast. Essential for this effect is the dipole interaction. We
simulate the low temperature behavior of diluted Ising-antiferromagnets by a
Monte Carlo simulation considering long range interaction. The metamagnetic
domain structure occurring due to the dipole interaction is investigated by
graphical representation. In the model considered the antiferromagnetic state
is stable for an external magnetic field smaller than a lower boundary
while for fields larger than an upper boundary the system is in the
saturated paramagnetic phase, where the spins are ferromagnetically polarized.
For magnetic fields in between these two boundaries a mixed phase occurs
consisting of ferromagnetic domains in an antiferromagnetic background. The
position of these ferromagnetic domains is stored in the system: after a cycle
in which the field is first removed and afterwards applied again the domains
reappear at their original positions. The reason for this effect can be found
in the frozen antiferromagnetic domain state which occurs after removing the
field.Comment: Latex, 10 pages; 3 postsript-figures, compressed tar-file, uuencoded,
report 10109
Limits on dark matter proton scattering from neutrino telescopes using micrOMEGAs
Limits on dark matter spin dependent elastic scattering cross section on
protons derived from IceCube data are obtained for different dark matter
annihilation channels using micrOMEGAs. The uncertainty on the derived limits,
estimated by using different neutrino spectra, can reach a factor two. For all
dark matter annihilation channels except for quarks, the limits on the spin
dependent cross section are more stringent than those obtained in direct
detection experiments. The new functions that allow to derive those limits are
described.Comment: 23 pages, 7 figures; v2: references added; v3 and v4: clarifications
added; The code can be downloaded from https://lapth.cnrs.fr/micromega
Singular point characterization in microscopic flows
We suggest an approach to microrheology based on optical traps in order to
measure fluid fluxes around singular points of fluid flows. We experimentally
demonstrate this technique, applying it to the characterization of controlled
flows produced by a set of birefringent spheres spinning due to the transfer of
light angular momentum. Unlike the previous techniques, this method is able to
distinguish between a singular point in a complex flow and the absence of flow
at all; furthermore it permits us to characterize the stability of the singular
point.Comment: 4 pages and 4 figure
Ordering in the dilute weakly-anisotropic antiferromagnet Mn(0.35)Zn(0.65)F2
The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated
by neutron scattering in zero field. The Bragg peaks observed below the Neel
temperature TN (approximately 10.9 K) indicate stable antiferromagnetic
long-range ordering at low temperature. The critical behavior is governed by
random-exchange Ising model critical exponents (nu approximately 0.69 and gamma
approximately 1.31), as reported for Mn(x)Zn(1-x)F2 with higher x and for the
isostructural compound Fe(x)Zn(1-x)F2. However, in addition to the Bragg peaks,
unusual scattering behavior appears for |q|>0 below a glassy temperature Tg
approximately 7.0 K. The glassy region T<Tg corresponds to that of noticeable
frequency dependence in earlier zero-field ac susceptibility measurements on
this sample. These results indicate that long-range order coexists with
short-range nonequilibrium clusters in this highly diluted magnet.Comment: 7 pages, 5 figure
How light can the lightest neutralino be?
In this talk we summarize previous work on mass bounds of a light neutralino
in the Minimal Supersymmetric Standard Model. We show that without the GUT
relation between the gaugino mass parameters M_1 and M_2, the mass of the
lightest neutralino is essentially unconstrained by collider bounds and
precision observables. We conclude by considering also the astrophysics and
cosmology of a light neutralino.Comment: 6 pages, 3 figures, to appear in the proceedings of the 16th
International Symposium on Particles, Strings and Cosmology (PASCOS2010),
Valencia (Spain), July 19th - 23rd, 201
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