6,036 research outputs found
The Stringy Quantum Hall Fluid
Using branes in massive Type IIA string theory, and a novel decoupling limit,
we provide an explicit correspondence between non-commutative Chern-Simons
theory and the fractional quantum Hall fluid. The role of the electrons is
played by D-particles, the background magnetic field corresponds to a RR 2-form
flux, and the two-dimensional fluid is described by non-commutative D2-branes.
The filling fraction is given by the ratio of the number of D2-branes and the
number of D8-branes, and therefore by the ratio rank/level of the Chern-Simons
gauge theory. Quasiparticles and quasiholes are realized as endpoints of
fundamental strings on the D2-branes, and are found to possess fractional
D-particle charges and fractional statistics.Comment: 24 pages, 2 figures; references adde
Suppression of Spin-Orbit Scattering in Strong-Disordered Gold Nanojunctions
We discovered that spin-orbit scattering in strong-disordered gold
nanojunctions is strongly suppressed relative to that in weak-disordered gold
thin films. This property is unusual because in weak-disordered films,
spin-orbit scattering increases with disorder. Granularity and freezing of
spin-orbit scattering inside the grains explains the suppression of spin-orbit
scattering. We propose a generalized Elliot-Yafet relation that applies to
strong-disordered granular regime.Comment: 4 pages 4 figure
Slow Dynamics in Glasses
Minimalist theories of complex systems are broadly of two kinds: mean-field
and axiomatic. So far all theories of complex properties absent from simple
systems and intrinsic to glasses are axiomatic. Stretched Exponential
Relaxation (SER) is the prototypical complex temporal property of glasses,
discovered by Kohlrausch 150 years ago, and now observed almost universally in
microscopically homogeneous, complex non-equilibrium materials, including
luminescent electronic (Coulomb) glasses. Critical comparison of alternative
axiomatic theories with both numerical simulations and experiments strongly
favors dynamical trap models over static percolative or energy landscape
models.
PACS: 61.20.Lc; 67.40.F
Generalized Paraxial Ray Trace Procedure Derived from Geodesic Deviation
Paraxial ray tracing procedures have become widely accepted techniques for
acoustic models in seismology and underwater acoustics. To date a generic form
of these procedures including fluid motion and time dependence has not appeared
in the literature. A detailed investigation of the characteristic curves of the
equations of hydrodynamics allows for an immediate generalization of the
procedure to be extracted from the equation form geodesic deviation. The
general paraxial ray trace equations serve as an ideal supplement to ordinary
ray tracing in predicting the deformation of acoustic beams in random
environments. The general procedure is derived in terms of affine
parameterization and in a coordinate time parameterization ideal for
application to physical acoustic ray propagation. The formalism is applied to
layered media, where the deviation equation reduces to a second order
differential equation for a single field with a general solution in terms of a
depth integral along the ray path. Some features are illustrated through
special cases which lead to exact solutions in terms of either ordinary or
special functions.Comment: Original; 40 pages (double spaced), 1 figure Replaced version; 36
pages single spaced, 7 figures. Expanded content; Complete derivation of the
equations from the equations of hydrodynamics, introduction of an auxiliary
basis for three dimensional wave-front modeling. Typos in text and equations
correcte
ABJM with Flavors and FQHE
We add fundamental matters to the N=6 Chern-Simons theory (ABJM theory), and
show that D6-branes wrapped over AdS_4 x S^3/Z_2 in type IIA superstring theory
on AdS_4 x CP^3 give its dual description with N=3 supersymmetry. We confirm
this by the arguments based on R-symmetry, supersymmetry, and brane
configuration of ABJM theory. We also analyze the fluctuations of the D6-brane
and compute the conformal dimensions of dual operators. In the presence of
fractional branes, the ABJM theory can model the fractional quantum Hall effect
(FQHE), with RR-fields regarded as the external electric-magnetic field. We
show that an addition of the flavor D6-brane describes a class of fractional
quantum Hall plateau transition.Comment: 23 pages, Latex, no figures; (v2) references added, typos correcte
Placental transfer of a hydroxylated polychlorinated biphenyl and effects on fetal and maternal thyroid hormone homeostasis in the rat
Earlier studies at our laboratory indicated that several hydroxylated polychlorinated biphenyls (OH-PCBs) detected in human blood could specifically inhibit thyroxine (T4) transport by competitive binding to the thyroid hormone transport protein transthyretin (TTR) in vitro. In the present study we investigated the effects of prenatal exposure to 5 mg/kg body weight of [14C]-labeled or unlabeled 4-OH-2,3,3',4',5-pentachlorobiphenyl (4-OH-CB107), one of the major metabolites of PCBs detected in human blood, from gestation days (GD) 10 to 16 on thyroid hormone status and metabolism in pregnant rats and their fetuses at GD 17 and GD 20. 4-OH-CB107 is a metabolite of both 2,3,3',4,4'-pentachlorobiphenyl (CB-105) and 2,3',4,4',5-pentachlorobiphenyl (CB-118). We were able to show the accumulation of 4-OH-CB107 in the fetal compartment. The fetal/maternal ratios at GD 20 in liver, cerebellum, and plasma were 11.0, 2.6, and 1.2, respectively. The 14C-4-OH-CB107-derived radioactivity in plasma was bound to TTR in both dams and fetuses. Fetal plasma TT4 and FT4 levels were significantly decreased at GD 17 and GD 20 (89 and 41␛espectively at GD 20). Fetal thyroid stimulating hormone levels were increased by 124 at GD 20. The T4 concentrations in fetal forebrain homogenates at GD20 were reduced by 35°but no effects could be detected on brain T3 concentrations. The deiodination of T4 to T3 was significantly increased in fetal forebrain homogenates at GD 17, and unaltered at GD 20. In addition, no alterations were observed in maternal and fetal hepatic T4-UDP-glucuronosyltransferase activity, type I deiodinase activity, and EROD activity. In conclusion, exposure of pregnant rats to 4-OH-CB107 results in the distribution of the compound in the maternal and fetal compartment, which is probably caused by the binding of the PCB metabolite to TTR. Consequently, TT4 levels in fetal plasma and brain samples were reduced. Despite reductions in fetal brain T4 levels, the active hormone (T3) in fetal brains remained unaffected
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