443 research outputs found
Nonlinear mechanism of plasmon damping in electron gas
At plasmon resonance, the condition of applicability of the linear response theory, which is the smallness of the oscillating field, evidently breaks down. We suggest a variant of the quadratic response theory which remains valid near and at plasma frequency and demonstrate that, as could be anticipated, the nonlinearity serves itself to restrict the amplitude of plasma oscillations, thus providing a mechanism of ânonlinear damping.â We apply this approach to calculate the damping of plasmon in two-dimensional electron gas below the threshold wave vector, which damping has recently been observed experimentally in the S1 surface band of Si(111)-sqrt[3]Ăsqrt[3]-Ag
Beneficial effects of green tea: A literature review
The health benefits of green tea for a wide variety of ailments, including different types of cancer, heart disease, and liver disease, were reported. Many of these beneficial effects of green tea are related to its catechin, particularly (-)-epigallocatechin-3-gallate, content. There is evidence from in vitro and animal studies on the underlying mechanisms of green tea catechins and their biological actions. There are also human studies on using green tea catechins to treat metabolic syndrome, such as obesity, type II diabetes, and cardiovascular risk factors
Comment on Dirac spectral sum rules for QCD_3
Recently Magnea hep-th/9907096 , hep-th/9912207 [Phys.Rev.D61, 056005 (2000);
Phys.Rev.D62, 016005 (2000)] claimed to have computed the first sum rules for
Dirac operators in 3D gauge theories from 0D non-linear sigma models. I point
out that these computations are incorrect, and that they contradict with the
exact results for the spectral densities unambiguously derived from random
matrix theory by Nagao and myself.Comment: REVTeX 3.1, 2 pages, no figure. (v2) redundant part removed,
conclusion unchange
Smallest Dirac Eigenvalue Distribution from Random Matrix Theory
We derive the hole probability and the distribution of the smallest
eigenvalue of chiral hermitian random matrices corresponding to Dirac operators
coupled to massive quarks in QCD. They are expressed in terms of the QCD
partition function in the mesoscopic regime. Their universality is explicitly
related to that of the microscopic massive Bessel kernel.Comment: 4 pages, 1 figure, REVTeX. Minor typos in subscripts corrected.
Version to appear in Phys. Rev.
Non-supersymmetric cousins of supersymmetric gauge theories: quantum space of parameters and double scaling limits
I point out that standard two dimensional, asymptotically free, non-linear
sigma models, supplemented with terms giving a mass to the would-be Goldstone
bosons, share many properties with four dimensional supersymmetric gauge
theories, and are tractable even in the non-supersymmetric cases. The space of
mass parameters gets quantum corrections analogous to what was found on the
moduli space of the supersymmetric gauge theories. I focus on a simple purely
bosonic example exhibiting many interesting phenomena: massless solitons and
bound states, Argyres-Douglas-like CFTs and duality in the infrared, and
rearrangement of the spectrum of stable states from weak to strong coupling. At
the singularities on the space of parameters, the model can be described by a
continuous theory of randomly branched polymers, which is defined beyond
perturbation theory by taking an appropriate double scaling limit.Comment: 10 pages, 1 figure. Slightly expanded version. Typos correcte
From polymers to quantum gravity: triple-scaling in rectangular matrix models
Rectangular matrix models can be solved in several qualitatively
distinct large limits, since two independent parameters govern the size of
the matrix. Regarded as models of random surfaces, these matrix models
interpolate between branched polymer behaviour and two-dimensional quantum
gravity. We solve such models in a `triple-scaling' regime in this paper, with
and becoming large independently. A correspondence between phase
transitions and singularities of mappings from to is
indicated. At different critical points, the scaling behavior is determined by:
i) two decoupled ordinary differential equations; ii) an ordinary differential
equation and a finite difference equation; or iii) two coupled partial
differential equations. The Painlev\'e II equation arises (in conjunction with
a difference equation) at a point associated with branched polymers. For
critical points described by partial differential equations, there are dual
weak-coupling/strong-coupling expansions. It is conjectured that the new
physics is related to microscopic topology fluctuations.Comment: 29 page
Topology and the Dirac Operator Spectrum in Finite-Volume Gauge Theories
The interplay between between gauge-field winding numbers, theta-vacua, and
the Dirac operator spectrum in finite-volume gauge theories is reconsidered. To
assess the weight of each topological sector, we compare the mass-dependent
chiral condensate in gauge field sectors of fixed topological index with the
answer obtained by summing over the topological charge. Also the microscopic
Dirac operator spectrum in the full finite-volume Yang-Mills theory is obtained
in this way, by summing over all topological sectors with the appropriate
weight.Comment: LaTeX, 21 pages. One reference adde
The microscopic spectrum of the QCD Dirac operator with finite quark masses
We compute the microscopic spectrum of the QCD Dirac operator in the presence
of dynamical fermions in the framework of random-matrix theory for the chiral
Gaussian unitary ensemble. We obtain results for the microscopic spectral
correlators, the microscopic spectral density, and the distribution of the
smallest eigenvalue for an arbitrary number of flavors, arbitrary quark masses,
and arbitrary topological charge.Comment: 11 pages, RevTeX, 2 figures (included), minor typos corrected and
discussion extended, version to appear in Phys. Rev.
Purification of aromatic l-amino acid decarboxylase from bovine brain with a monoclonal antibody
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