49,816 research outputs found
Conformal or Walking? Monte Carlo renormalization group studies of SU(3) gauge models with fundamental fermions
Strongly coupled gauge systems with many fermions are important in many
phenomenological models. I use the 2-lattice matching Monte Carlo
renormalization group method to study the fixed point structure and critical
indexes of SU(3) gauge models with 8 and 12 flavors of fundamental fermions.
With an improved renormalization group block transformation I am able to
connect the perturbative and confining regimes of the N_f=8 flavor system, thus
verifying its QCD-like nature. With N_f=12 flavors the data favor the existence
of an infrared fixed point and conformal phase, though the results are also
consistent with very slow walking. I measure the anomalous mass dimension in
both systems at several gauge couplings and find that they are barely different
from the free field value.Comment: 26 pages, 11 figure
First-principles calculations of a high-pressure synthesized compound PtC
First-principles density-functional method is used to study the recently
high-pressure synthesized compound PtC. It is confirmed by our calculations
that the platinum carbide has a zinc-blende ground-state phase at zero pressure
and the rock-salt structure is a high-pressure phase. The theoretical
transition pressure from zinc-blende to rock-salt is determined to be 52GPa.
Furthermore, our calculation shows the possibility that the experimentally
synthesized PtC by Ono et al. under high pressure condition might undergo a
transition from rock-salt structure to zinc-blende after the pressure quench to
ambient condition.Comment: A revised versio
Field-Induced Ferromagnetic Order and Colossal Magnetoresistance in La_{1.2}Sr_{1.8}Mn_2O_7: a ^{139}La NMR study
In order to gain insights into the origin of colossal magneto-resistance
(CMR) in manganese oxides, we performed a ^{139}La NMR study in the
double-layered compound La_{1.2}Sr_{1.8}Mn_2O_7. We find that above the Curie
temperature T_C=126 K, applying a magnetic field induces a long-range
ferromagnetic order that persists up to T=330 K. The critical field at which
the induced magnetic moment is saturated coincides with the field at which the
CMR effect reaches to a maximum. Our results therefore indicate that the CMR
observed above T_C in this compound is due to the field-induced ferromagnetism
that produces a metallic state via the double exchange interaction
Spin squeezing: transforming one-axis-twisting into two-axis-twisting
Squeezed spin states possess unique quantum correlation or entanglement that
are of significant promises for advancing quantum information processing and
quantum metrology. In recent back to back publications [C. Gross \textit{et al,
Nature} \textbf{464}, 1165 (2010) and Max F. Riedel \textit{et al, Nature}
\textbf{464}, 1170 (2010)], reduced spin fluctuations are observed leading to
spin squeezing at -8.2dB and -2.5dB respectively in two-component atomic
condensates exhibiting one-axis-twisting interactions (OAT). The noise
reduction limit for the OAT interaction scales as , which
for a condensate with atoms, is about 100 times below standard
quantum limit. We present a scheme using repeated Rabi pulses capable of
transforming the OAT spin squeezing into the two-axis-twisting type, leading to
Heisenberg limited noise reduction , or an extra 10-fold
improvement for .Comment: 4 pages, 3 figure
Lifetime Difference and Endpoint effect in the Inclusive Bottom Hadron Decays
The lifetime differences of bottom hadrons are known to be properly explained
within the framework of heavy quark effective field theory(HQEFT) of QCD via
the inverse expansion of the dressed heavy quark mass. In general, the spectrum
around the endpoint region is not well behaved due to the invalidity of
expansion near the endpoint. The curve fitting method is adopted to treat the
endpoint behavior. It turns out that the endpoint effects are truly small and
the explanation on the lifetime differences in the HQEFT of QCD is then well
justified. The inclusion of the endpoint effects makes the prediction on the
lifetime differences and the extraction on the CKM matrix element
more reliable.Comment: 11 pages, Revtex, 10 figures, 6 tables, published versio
Properties of glucoside 3-dehydrogenase and its potential applications
Glucoside 3-dehydrogenase, one of the glucose redoxidases, is perhaps known for the vital role it plays in converting a series of sugars to their corresponding 3-ketoglucosides. Glucoside 3-dehydrogenase has attracted considerable attention in recent years due to broad substrate specificity and excellent regioselectivity. Glucoside 3-dehydrogenase is a FAD-enzyme, which is capable of oxidizing glucosides and galactosides to their corresponding 3-ketoglycosides, due to the enzyme’s site-selective oxidation of the C-3 hydroxyl group. These 3-ketoglucosides are useful as building blocks for chemicals such as detergents and polymers. The versatile glucoside 3-dehydrogenase has potential applications in different fields including sugar industry, clinical diagnosis and pharmaceuticalintermediates synthesis. This review attempts to describe the glucoside 3-dehydrogenase concerning the sources, properties and applications in detail
Optical properties of in the normal state
We present the optical reflectance and conductivity spectra for non-oxide
antiperovskite superconductor at different temperatures. The
reflectance drops gradually over a large energy scale up to 33,000 cm,
with the presence of several wiggles. The reflectance has slight temperature
dependence at low frequency but becomes temperature independent at high
frequency. The optical conductivity shows a Drude response at low frequencies
and four broad absorption features in the frequency range from 600 to
33,000 . We illustrate that those features can be well understood from
the intra- and interband transitions between different components of Ni 3d
bands which are hybridized with C 2p bands. There is a good agreement between
our experimental data and the first-principle band structure calculations.Comment: 4 pages, to be published in Phys. Rev.
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