4,057 research outputs found
Thermal Hall conductivity of marginal Fermi liquids subject to out-of plane impurities in high- cuprates
The effect of out-of-plane impurities on the thermal Hall conductivity
of in-plane marginal-Fermi-liquid (MFL) quasiparticles in
high- cuprates is examined by following the work on electrical Hall
conductivity by Varma and Abraham [Phys. Rev. Lett. 86, 4652
(2001)]. It is shown that the effective Lorentz force exerted by these
impurities is a weak function of energies of the MFL quasiparticles, resulting
in nearly the same temperature dependence of and ,
indicative of obedience of the Wiedemann-Franz law. The inconsistency of the
theoretical result with the experimental one is speculated to be the
consequence of the different amounts of out-of-plane impurities in the two
YBaCuO samples used for the and measurements.Comment: 5 pages, 2 eps figures; final versio
The environmental dependence of the stellar mass-size relation in STAGES galaxies
We present the stellar mass-size relations for elliptical, lenticular, and
spiral galaxies in the field and cluster environments using HST/ACS imaging and
data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a
large sample of ~1200 field and cluster galaxies, and a sub-sample of cluster
core galaxies, and quantify the significance of any putative environmental
dependence on the stellar mass-size relation. For elliptical, lenticular, and
high-mass (log M*/M_sun > 10) spiral galaxies we find no evidence to suggest
any such environmental dependence, implying that internal drivers are governing
their size evolution. For intermediate/low-mass spirals (log M*/M_sun < 10) we
find evidence, significant at the 2-sigma level, for a possible environmental
dependence on galaxy sizes: the mean effective radius a_e for lower-mass
spirals is ~15-20 per cent larger in the field than in the cluster. This is due
to a population of low-mass large-a_e field spirals that are largely absent
from the cluster environments. These large-a_e field spirals contain extended
stellar discs not present in their cluster counterparts. This suggests the
fragile extended stellar discs of these spiral galaxies may not survive the
environmental conditions in the cluster. Our results suggest that internal
physical processes are the main drivers governing the size evolution of
galaxies, with the environment possibly playing a role affecting only the discs
of intermediate/low-mass spirals.Comment: 16 pages, 10 figures, accepted to MNRA
Fermionic superfluidity: From high Tc superconductors to ultracold Fermi gases
We present a pairing fluctuation theory which self-consistently incorporates
finite momentum pair excitations in the context of BCS--Bose-Einstein
condensation (BEC) crossover, and we apply this theory to high
superconductors and ultracold Fermi gases. There are strong similarities
between Fermi gases in the unitary regime and high Tc superconductors. Here we
address key issues of common interest, especially the pseudogap. In the Fermi
gases we summarize recent experiments including various phase diagrams (with
and without population imbalance), as well as evidence for a pseudogap in
thermodynamic and other experiments.Comment: Expanded version, invited talk at the 5th International Conference on
Complex Matter -- Stripes 2006, 6 pages, 6 figure
Ethanol and production of the hepatotoxic metabolite of acetaminophen in healthy adults
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109855/1/cptclpt200062.pd
Torque magnetometry on single-crystal high temperature superconductors near the critical temperature: a scaling approach
Angular-dependent magnetic torque measurements performed near the critical
temperature on single crystals of HgBa_{2}CuO_{4+y}, La_{2-x}Sr{x}CuO_{4}, and
YBa_{2}Cu_{3}O_{6.93} are scaled, following the 3D XY model, in order to
determine the scaling function dG^{\pm}(z)/dz which describes the universal
critical properties near T_{c}. A systematic shift of the scaling function with
increasing effective mass anisotropy \gamma = (m_{ab}*/m_{c}*)^{1/2} is
observed, which may be understood in terms of a 3D-2D crossover. Further
evidence for a 3D-2D crossover is found from temperature-dependent torque
measurements carried out in different magnetic fields at different field
orientations \delta, which show a quasi 2D "crossing region'' (M*,T*). The
occurrence of this "crossing phenomenon'' is explained in a phenomenological
way from the weak z dependence of the scaling function around a value z = z*.
The "crossing'' temperature T* is found to be angular-dependent. Torque
measurements above T_{c} reveal that fluctuations are strongly enhanced in the
underdoped regime where the anisotropy is large, whereas they are less
important in the overdoped regime.Comment: 9 pages, 10 figures, submitted to PR
A Spectral Method for Elliptic Equations: The Neumann Problem
Let be an open, simply connected, and bounded region in
, , and assume its boundary is smooth.
Consider solving an elliptic partial differential equation over with a Neumann boundary condition. The problem is converted
to an equivalent elliptic problem over the unit ball , and then a spectral
Galerkin method is used to create a convergent sequence of multivariate
polynomials of degree that is convergent to . The
transformation from to requires a special analytical calculation
for its implementation. With sufficiently smooth problem parameters, the method
is shown to be rapidly convergent. For
and assuming is a boundary, the convergence of
to zero is faster than any power of .
Numerical examples in and show experimentally
an exponential rate of convergence.Comment: 23 pages, 11 figure
Repurpose 2D Character Animations for a VR Environment Using BDH Shape Interpolation.
Virtual Reality technology has spread rapidly in recent years.
However, its growth risks ending soon due to the absence of quality content, except for few exceptions. We present an original framework that allows artists to use 2D characters and animations in a 3D Virtual Reality environment, in order to give an easier access to the production of content for the platform. In traditional platforms, 2D animation represents a more economic and immediate alternative to 3D. The challenge in adapting 2D characters to a 3D environment is to interpret the missing depth information. A 2D character is actually flat, so there is not any depth information, and every body part is at the same level of the others. We exploit mesh interpolation, billboarding and parallax scrolling to simulate the depth between each body segment of the character. We have developed a prototype of the system, and extensive tests with a 2D animation production show the effectiveness of our framework
Spatial matter density mapping of the STAGES Abell A901/2 supercluster field with 3D lensing
We present weak lensing data from the Hubble Space Telescope(HST)/Space Telescope A901/902 Galaxy Evolution Survey (STAGES) survey to study the three-dimensional spatial distribution of matter and galaxies in the Abell 901/902 supercluster complex. Our method improves over the existing 3D lensing mapping techniques by calibrating and removing redshift bias and accounting for the effects of the radial elongation of 3D structures. We also include the first detailed noise analysis of a 3D lensing map, showing that even with deep HST-quality data, only the most massive structures, for example M200≳ 1015M⊙h-1 at z∼ 0.8, can be resolved in 3D with any reasonable redshift accuracy (Δz≈ 0.15). We compare the lensing map to the stellar mass distribution and find luminous counterparts for all mass peaks detected with a peak significance >3σ. We see structures in and behind the z= 0.165 foreground supercluster, finding structure directly behind the A901b cluster at z∼ 0.6 and also behind the south-west (SW) group at z∼ 0.7. This 3D structure viewed in projection has no significant impact on recent mass estimates of A901b or the SW group components SWa and SWb. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Central Structural Parameters of Early-Type Galaxies as Viewed with HST/NICMOS
We present surface photometry for the central regions of a sample of 33
early-type (E, S0, and S0/a) galaxies observed at 1.6 microns (H band) using
the Hubble Space Telescope (HST). We employ a new technique of two-dimensional
fitting to extract quantitative parameters for the bulge light distribution and
nuclear point sources, taking into consideration the effects of the
point-spread function. Parameterizing the bulge profile with a ``Nuker'' law,
we confirm that the central surface-brightness distributions largely fall into
two categories, each of which correlates with the global properties of the
galaxies. ``Core'' galaxies tend to be luminous ellipticals with boxy or pure
elliptical isophotes, whereas ``power-law'' galaxies are preferentially lower
luminosity systems with disky isophotes. Unlike most previous studies, however,
we do not find a clear gap in the distribution of inner cusp slopes; several
objects have inner cusp slopes (0.3 < gamma < 0.5) which straddle the regimes
conventionally defined for core and power-law type galaxies. The nature of
these intermediate objects is unclear. We draw attention to two objects in the
sample which appear to be promising cases of galaxies with isothermal cores
that are not the brightest members of a cluster. Unresolved nuclear point
sources are found in about 50% of the sample galaxies, roughly independent of
profile type, with magnitudes in the range m^{nuc}_H = 12.8 to 17.4 mag, which
correspond to M_H^{nuc} = -12.8 to -18.4 mag. (Abridged)Comment: To appear in The Astronomical Journal. Latex, 24 pages and 17 JPEG
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Stripes, Non-Fermi-Liquid Behavior, and High-Tc Superconductivity
The electronic structure of the high-Tc cuprates is studied in terms of
"large-U" and "small-U" orbitals. A striped structure and three types of
quasiparticles are obtained, polaron-like "stripons" carrying charge, "svivons"
carrying spin, and "quasielectrons" carrying both. The anomalous properties are
explained, and specifically the behavior of the resistivity, Hall constant, and
thermoelectric power. High-temperature superconductivity results from
transitions between pair states of quasielectrons and stripons.Comment: 4 page
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