2,720 research outputs found
E1 amplitudes, lifetimes, and polarizabilities of the low-lying levels of atomic ytterbium
The results of ab initio calculation of E1 amplitudes, lifetimes,and
polarizabilities for several low-lying levels of ytterbium are reported. The
effective Hamiltonian for the valence electrons has been constructed in the
frame of CI+MBPT method and solutions of many electron equation are found.Comment: 11 pages, submitted to Phys.Rev.
Advances in Unified Strength Theory and its Generalization
AbstractIt has been two decades since the first presentation of “A new model and theory on yield and failure of materials under complex stress state” at ICM-6 held at Kyoto, Japan in 1991. The twin-shear element model and a new strength theory were proposed at ICM-6. However, only the two equations were introduced, the characteristics and its applications of this strength theory have not been studied in details. A great deal of researches on this new strength theory and its applications are developed since then by Yu and other scholars at other Universities and Institutes in some countries. Some behaviour of the unified strength theory are described here. The advances in the unified strength theory and its applications are summarized briefly in the framework of continuum mechanics and engineering application
Optical cavity tests of Lorentz invariance for the electron
A hypothetical violation of Lorentz invariance in the electrons' equation of
motion (expressed within the Lorentz-violating extension of the standard model)
leads to a change of the geometry of crystals and thus shifts the resonance
frequency of an electromagnetic cavity. This allows experimental tests of
Lorentz invariance of the electron sector of the standard model. The material
dependence of the effect allows to separate it from an additional shift caused
by Lorentz violation in electrodynamics, and to place independent limits on
both effects. From present experiments, upper limits on Lorentz violation in
the electrons' kinetic energy term are deduced.Comment: 17 pages revte
Metallography of Al-Si Alloys with Alloying By Fe up to 1%
Metallographic analysis of aluminum-silicon alloys with different silicon content from 0 to 12% carried out. All alloys were differed in 2% by silicon amount from each other and all of them were additionally alloyed with iron in an amount of up to 1% in order to improve the technological properties in a die casting process. The paper shows the distribution of structural components of alloys made by electronic microscopy.
Keywords: aluminum-silicon alloys, metallography analysis, eutectic, structure, cast alloy, alloying, electron microscop
CFT Duals for Extreme Black Holes
It is argued that the general four-dimensional extremal Kerr-Newman-AdS-dS
black hole is holographically dual to a (chiral half of a) two-dimensional CFT,
generalizing an argument given recently for the special case of extremal Kerr.
Specifically, the asymptotic symmetries of the near-horizon region of the
general extremal black hole are shown to be generated by a Virasoro algebra.
Semiclassical formulae are derived for the central charge and temperature of
the dual CFT as functions of the cosmological constant, Newton's constant and
the black hole charges and spin. We then show, assuming the Cardy formula, that
the microscopic entropy of the dual CFT precisely reproduces the macroscopic
Bekenstein-Hawking area law. This CFT description becomes singular in the
extreme Reissner-Nordstrom limit where the black hole has no spin. At this
point a second dual CFT description is proposed in which the global part of the
U(1) gauge symmetry is promoted to a Virasoro algebra. This second description
is also found to reproduce the area law. Various further generalizations
including higher dimensions are discussed.Comment: 18 pages; v2 minor change
Additive N-Step Markov Chains as Prototype Model of Symbolic Stochastic Dynamical Systems with Long-Range Correlations
A theory of symbolic dynamic systems with long-range correlations based on
the consideration of the binary N-step Markov chains developed earlier in Phys.
Rev. Lett. 90, 110601 (2003) is generalized to the biased case (non equal
numbers of zeros and unities in the chain). In the model, the conditional
probability that the i-th symbol in the chain equals zero (or unity) is a
linear function of the number of unities (zeros) among the preceding N symbols.
The correlation and distribution functions as well as the variance of number of
symbols in the words of arbitrary length L are obtained analytically and
verified by numerical simulations. A self-similarity of the studied stochastic
process is revealed and the similarity group transformation of the chain
parameters is presented. The diffusion Fokker-Planck equation governing the
distribution function of the L-words is explored. If the persistent
correlations are not extremely strong, the distribution function is shown to be
the Gaussian with the variance being nonlinearly dependent on L. An equation
connecting the memory and correlation function of the additive Markov chain is
presented. This equation allows reconstructing a memory function using a
correlation function of the system. Effectiveness and robustness of the
proposed method is demonstrated by simple model examples. Memory functions of
concrete coarse-grained literary texts are found and their universal power-law
behavior at long distances is revealed.Comment: 19 pages, 8 figure
Dynamic correlations of the Coulomb Luttinger liquid
The dynamic density response function, form-factor, and spectral function of
a Luttinger liquid with Coulomb electron-electron interaction are studied with
the emphasis on the short-range electron correlations. The Coulomb interaction
changes dramatically the density response function as compared to the case of
the short-ranged interaction. The form of the density response function is
smoothing with time, and the oscillatory structure appears. However, the
spectral functions remain qualitatively the same. The dynamic form-factor
contains the -peak in the long-wave region, corresponding to one-boson
excitations. Besides, the multi-boson-excitations band exists in the
wave-number region near to . The dynamic form-factor diverges at the
edges of this band, while the dielectric function goes to zero there, which
indicates the appearance of a soft mode. We develop a method to analyze the
asymptotics of the spectral functions near to the edges of the
multi-boson-excitations band.Comment: 11 pages, 3 figures, submitted to PR
A Godel-Friedman cosmology?
Based on the mathematical similarity between the Friedman open metric and
Godel's metric in the case of nearby distances, we investigate a new scenario
for the Universe's evolution, where the present Friedman universe originates
from a primordial Godel universe by a phase transition during which the
cosmological constant vanishes. Using Hubble's constant and the present matter
density as input, we show that the radius and density of the primordial Godel
universe are close, in order of magnitude, to the present values, and that the
time of expansion coincides with the age of the Universe in the standard
Friedman model. In addition, the conservation of angular momentum provides, in
this context, a possible origin for the rotation of galaxies, leading to a
relation between the masses and spins corroborated by observational data.Comment: Extended version, accepted for publication in Physical Review
Studying Kaon-pion S-wave scattering in K-matrix formalism
We generalize our previous work on \pi\pi scattering to K\pi scattering, and
re-analyze the experiment data of K\pi scattering below 1.6 GeV. Without any
free parameter, we explain K\pi I=3/2 S-wave phase shift very well by using
t-channel rho and u-channel K^* meson exchange. With the t-channel and
u-channel meson exchange fixed as the background term, we fit the K\pi I=1/2
S-wave data of the LASS experiment quite well by introducing one or two
s-channel resonances. It is found that there is only one s-channel resonance
between K\pi threshold and 1.6 GeV, i.e., K_0^*(1430) with a mass around
1438~1486 MeV and a width about 346 MeV, while the t-channel rho exchange gives
a pole at (450-480i) MeV for the amplitude.Comment: REVTeX4 file, 11 pages and 3 figure
Instanton moduli spaces and bases in coset conformal field theory
Recently proposed relation between conformal field theories in two dimensions
and supersymmetric gauge theories in four dimensions predicts the existence of
the distinguished basis in the space of local fields in CFT. This basis has a
number of remarkable properties, one of them is the complete factorization of
the coefficients of the operator product expansion. We consider a particular
case of the U(r) gauge theory on C^2/Z_p which corresponds to a certain coset
conformal field theory and describe the properties of this basis. We argue that
in the case p=2, r=2 there exist different bases. We give an explicit
construction of one of them. For another basis we propose the formula for
matrix elements.Comment: 31 pages, 3 figure
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