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1.
V. G. Arakcheev V. N. Bagratashvili A. A. Valeev V. B. Morozov V. K. Popov 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(8):1245-1251
Carbon dioxide Fermi doublet 1388/1285 cm−1
Q-band broadenings and shifts measured using coherent anti-Stokes Raman spectroscopy are presented. Measurements were performed
over a wide density range (0.1ρ
c
< ρ < 1.9ρ
c
) during compression in the gaseous and condensed states at temperatures close to critical (the reduced temperature values
were T
r
= 0.995, 1.000, and 1.006). At densities above the ρ
c
critical value, the width of Q-bands did not increase as the density grew, and the low-frequency Q band considerably narrowed up to the density value 1.7ρ
c
. The main reason for this anomalous behavior was progressing narrowing of the spectral contribution caused by the special
features of rotational exchange in the condensed state and not related directly to the closeness to the critical point. The
refined critical broadening value was about 10% of the width for the high-frequency Q-band and 15% of the width for the low-frequency Q-band. 相似文献
2.
E.G. Drukarev M.G. Ryskin V.A. Sadovnikova 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):171-186
We calculate the contribution of pions to the $\bar qq$-expectation value κ(ρ) =<M|ˉq
q|M> in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional
straightforward calculation leads to the “pion condensation” at unrealistically small values of densities, causing even earlier
restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct
dependence of in-medium mass values on κ(ρ), e.g. the Nambu–Jona-Lasinio–model. We show, that in the self-consistent approach
the ρ-dependence of the condensate is described by a smooth curve. The “pion condensate” point is removed to much higher values
of density. The chiral restoration does not take place at least while ρ < 2.8ρ0 with ρ0 being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars)
in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found m
*(ρ0) = 0.6m, consistent with nowadays results of other authors.
Received: 8 October 1998 相似文献
3.
A. F. Rozenfeld K. Laneri E. V. Albano 《The European physical journal. Special topics》2007,143(1):3-8
A dynamic scaling Ansatz for the approach to stationary states in complex systems
is proposed and tested by means of extensive simulations applied to both
the Bak-Sneppen (BS) model, which exhibits robust Self-Organised
Critical (SOC) behaviour, and the Game of Life (GOL) of J. Conway,
whose critical behaviour is under debate. Considering the dynamic scaling behaviour of the density of
sites (ρ(t)), it is shown that i) by starting the dynamic measurements with configurations
such that ρ(t=0) →0, one observes an initial increase of the
density with exponents θ= 0.12(2) and θ= 0.11(2) for the BS and GOL models, respectively;
ii) by using initial configurations with ρ(t=0) →1, the density decays with exponents δ= 0.47(2) and δ= 0.28(2) for the BS
and GOL models, respectively.
It is also shown that the temporal autocorrelation decays with exponents
Ca = 0.35(2) (Ca = 0.35(5)) for the BS (GOL) model.
By using these dynamically determined critical exponents
and suitable scaling relationships, we also obtain the dynamic
exponents z = 2.10(5) (z = 2.10(5)) for the
BS (GOL) model.
Based on this evidence we conclude that the dynamic
approach to stationary states of the investigated models
can be described by suitable power-law functions
of time with well-defined exponents. 相似文献
4.
In numerical simulations of nonabelian plasma instabilities in the hard-loop approximation, a turbulent spectrum has been
observed that is characterized by a phase-space density of particles n(p)∼p
−ν
with exponent ν≃2, which is larger than expected from relativistic 2↔2 scatterings. Using the approach of Zakharov, L’vov and Falkovich,
we analyze possible Kolmogorov coefficients for relativistic (m≥4)-particle processes, which give at most ν=5/3 perturbatively for an energy cascade. We discuss non-perturbative scenarios which lead to larger values. As an extreme
limit we find the result ν=5 generically in an inherently non-perturbative effective field theory situation, which coincides with results obtained by
Berges et al. in large-N scalar field theory. If we instead assume that scaling behavior is determined by Schwinger–Dyson resummations such that the
different scaling of bare and dressed vertices matters, we find that intermediate values are possible. We present one simple
scenario, which would single out ν=2. 相似文献
5.
Sineeba Ramadas Vishnu M. Bannur 《The European Physical Journal C - Particles and Fields》2012,72(4):1975
From an analogy with non-relativistic degenerate QED plasma we make an estimate of the coupling strength of QGP hypothesized
to be present in compact star interiors. At densities ranging from 3ρ
0–10ρ
0 (normal nuclear density ρ
0=0.16 fm−3), quark matter is found to be strongly to intermediately coupled. The equation of state for QED plasma obtained via Pade
approximation, modified to QGP, yields stable stellar sequences with maximum mass ≳2M
⊙ for B
1/4≲215 MeV. 相似文献
6.
We introduce a new class of two-dimensional cellular automata with a bootstrap percolation-like dynamics. Each site can be
either empty or occupied by a single particle and the dynamics follows a deterministic updating rule at discrete times which
allows only emptying sites. We prove that the threshold density ρ
c
for convergence to a completely empty configuration is non trivial, 0<ρ
c
<1, contrary to standard bootstrap percolation. Furthermore we prove that in the subcritical regime, ρ<ρ
c
, emptying always occurs exponentially fast and that ρ
c
coincides with the critical density for two-dimensional oriented site percolation on ℤ2. This is known to occur also for some cellular automata with oriented rules for which the transition is continuous in the
value of the asymptotic density and the crossover length determining finite size effects diverges as a power law when the
critical density is approached from below. Instead for our model we prove that the transition is discontinuous and at the same time the crossover length diverges faster than any power law. The proofs of the discontinuity and the lower bound on the crossover length use a conjecture on the critical behaviour for
oriented percolation. The latter is supported by several numerical simulations and by analytical (though non rigorous) works
through renormalization techniques. Finally, we will discuss why, due to the peculiar mixed critical/first order character of this transition, the model is particularly relevant to study glassy and jamming transitions. Indeed, we will show that
it leads to a dynamical glass transition for a Kinetically Constrained Spin Model. Most of the results that we present are
the rigorous proofs of physical arguments developed in a joint work with D.S. Fisher. 相似文献
7.
Rolf Rentzsch Ch. Reich A. N. Ionov V. Ginodman I. Shlimak P. Fozooni M. J. Lea 《Physics of the Solid State》1999,41(5):757-760
We present a critical review of the present state of the critical exponent puzzle of the metal-insulator transition of doped
semiconductors with emphasis on the role of meso-and macroscopic inhomogeneity caused by the disorder of intended or unintended
acceptors and donors in crystals. By using both isotopic engineering and neutron transmutation doping (NTD) of germanium we
found for low compensations (at K=1.4 and 12%) that the critical exponents of the localization length and the dielectric constant are nearly ν=1/2 and ζ=1, which double for medium compensations (at K=38 and 54%) to ν=1 and ζ=2, respectively.
Fiz. Tverd. Tela (St. Petersburg) 41, 837–840 (May 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
8.
Laurent Desvillettes François Golse Valeria Ricci 《Journal of statistical physics》2008,131(5):941-967
We propose a mathematical derivation of Brinkman’s force for a cloud of particles immersed in an incompressible viscous fluid.
Specifically, we consider the Stokes or steady Navier-Stokes equations in a bounded domain Ω⊂ℝ3 for the velocity field u of an incompressible fluid with kinematic viscosity ν and density 1. Brinkman’s force consists of a source term 6π
ν
j where j is the current density of the particles, and of a friction term 6π
ν
ρ
u where ρ is the number density of particles. These additional terms in the motion equation for the fluid are obtained from the Stokes
or steady Navier-Stokes equations set in Ω minus the disjoint union of N balls of radius ε=1/N in the large N limit with no-slip boundary condition. The number density ρ and current density j are obtained from the limiting phase space empirical measure
, where x
k
is the center of the k-th ball and v
k
its instantaneous velocity. This can be seen as a generalization of Allaire’s result in [Arch. Ration. Mech. Anal. 113:209–259,
[1991]] who considered the case of periodically distributed x
k
s with v
k
=0, and our proof is based on slightly simpler though similar homogenization arguments. Similar equations are used for describing
the fluid phase in various models for sprays. 相似文献
9.
T.-H. Tang E. Deretey S. J. Knak Jensen I. G. Csizmadia 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(2):217-222
The electron densities for a number of molecules with either inter- or
intra-molecular hydrogen bonds are analyzed using the theory of atoms in
molecules. The levels of theory used include second order M?ller Plesset
and density functional methods. The molecules investigated ranges from small
molecules/ions to an alanine octa-peptide. The hydrogen bond length, BL,
varies from 1.15 to 3.01 ? and ρb, the electron density at the
bond critical point, spans the interval 0.0033 to 0.168 (au). We find that
the data may be represented by the relation
), where A and B are empirical constants. The relation is
compared to a similar relation derived from solid state experiments. Since
the ρb values are related to the bond strengths, this general
relationship may useful for hydrogen bond studies. 相似文献
10.
The excess 1/f noise in a random lattice with bond resistances r∼exp(−λx), where x is a random variable and λ≪1, is studied theoretically. It is shown that if the correlation function {δr
2}∼r
r
θ+2, then the relative spectral density of the noise in the system is expressed as C
e∼λm exp(−λ(1−p
c)), where p
c is the percolation threshold and m=νd (ν is the critical exponent of the correlation length and d is the dimensionality of the problem). It is hypothesized that the exponent m possesses a dual universality: It is independent of 1) the geometry of the lattice and 2) the θ-mechanism responsible for
the generation of the local noise. Numerical modeling in a three-dimensional lattice gives m=52.3 for θ=1 and θ=0, in agreement with the hypothesis.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 614–618 (25 April 1996) 相似文献
11.
M. A. Yurishchev 《Journal of Experimental and Theoretical Physics》2010,111(4):525-533
The behavior of Ising chains with the spin-spin interaction value λ in a transverse magnetic field of constant intensity (h = 1) is considered. For a chain of infinite length, exact analytical formulas are obtained for the second central moment
(dispersion) of the entropy operator Ŝ = -lnρ with reduced density matrix ρ, which corresponds to a semi-infinite part of the model chain occurring in the ground
state. In the vicinity of a critical point λc = 1, the entanglement entropy fluctuation ΔS (defined as the square root of dispersion) diverges as ΔS ∼ [ln(1/|1 − λ|)]1/2. For the known behavior of the entanglement entropy S, this divergence results in that the relative fluctuation δS = ΔS/S vanishes at the critical point, that is, a state with almost nonfluctuating entanglement is attained. 相似文献
12.
According to recent progresses in the finite size scaling theory of
disordered systems, thermodynamic observables are not self-averaging
at critical points when the disorder is relevant in the
Harris criterion sense. This lack of
self-averageness at criticality is directly related to the distribution
of pseudo-critical temperatures Tc(i,L) over the ensemble of
samples (i) of size L. In this paper, we apply this analysis to
disordered Poland-Scheraga models with different loop exponents c,
corresponding to marginal and relevant disorder. In all cases, we
numerically obtain a Gaussian
histogram of pseudo-critical temperatures Tc(i,L) with mean
Tcav(L) and width ΔTc(L).
For the marginal case c=1.5 corresponding to two-dimensional wetting,
both the width ΔTc(L) and the shift
[Tc(∞)-Tcav(L)] decay as L-1/2, so the exponent is
unchanged (νrandom=2=νpure) but disorder is relevant and
leads to non self-averaging at criticality.
For relevant disorder
c=1.75, the width ΔTc(L) and the shift
[Tc(∞)-Tcav(L)] decay with the same new exponent
L-1/νrandom (where νrandom ∼2.7 > 2 > νpure) and
there is again no self-averaging at criticality. Finally for the value
c=2.15, of interest in the context of DNA denaturation, the
transition is first-order in the pure case. In the presence of
disorder, the width ΔTc(L) ∼L-1/2
dominates over the shift [Tc(∞)-Tcav(L)] ∼L-1,
i.e. there are two correlation length exponents ν=2 and
that govern respectively the averaged/typical loop distribution. 相似文献
13.
S. Li Z. Q. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):299-304
We use the Ulam method to study spectral properties of the Perron-Frobenius operators of dynamical maps in a chaotic regime.
For maps with absorption we show numerically that the spectrum is characterized by the fractal Weyl law recently established
for nonunitary operators describing poles of quantum chaotic scattering with the Weyl exponent ν = d-1, where d is the fractal
dimension of corresponding strange set of trajectories nonescaping in future times. In contrast, for dissipative maps we numerically
find the Weyl exponent ν = d/2 where d is the fractal dimension of strange attractor. The Weyl exponent can be also expressed
via the relation ν = d0/2 where d0 is the fractal dimension of the invariant sets. We also discuss the properties of eigenvalues and eigenvectors of such operators
characterized by the fractal Weyl law. 相似文献
14.
15.
M.J. Bowick A. Cacciuto G. Thorleifsson A. Travesset 《The European physical journal. E, Soft matter》2001,5(2):149-160
We present an analysis of extensive large-scale Monte Carlo simulations of self-avoiding fixed-connectivity membranes for sizes (number of faces) ranging from 512 to 17672 (triangular) plaquettes. Self-avoidance is implemented via
impenetrable plaquettes. We simulate the impenetrable plaquette model in both three and four bulk dimensions. In both cases we find the
membrane to be flat for all temperatures: the size exponent in three dimensions is ν = 0.95(5) (Hausdorff dimension d
H = 2.1(1)). The single flat phase appears, furthermore, to be equivalent to the large bending rigidity phase of non-self-avoiding fixed-connectivity membranes --the roughness exponent in three dimensions is ξ = 0.63(4). This suggests that there is a unique
universality class for flat fixed-connectivity membranes without attractive interactions. Finally, we address some theoretical
and experimental implications of our work.
Received 23 June 2000 and Received in final form 25 October 2000 相似文献
16.
The character of the evolution of a system of weak links in granular high-temperature superconductors under the action of
an external magnetic field H
ext has been studied by measuring the current-voltage characteristics E(j)Hext = constE{(j)_{{H_{ext}} = const}} of YBa2Cu3O7 − δ (δ ≈ 0.05) ceramic samples. The measurements have been performed at T = 77.3 K in a range of very weak magnetic fields 0 < H
ext ≲ 0.5H
c2J, where H
c2J is the upper critical field of the Josephson weak links. The results have been used to construct the field dependences of
the magnetoresistance Δρ(H
ext) of the superconducting ceramics. It has been established that the parameters of the power equation E = A(j − j
cJ)ν and the magnetoresistance Δρ are nonmonotonic functions of the external magnetic field. The presence of extrema in the curves
A(H
ext), j
cJ(H
ext), ν(H
ext), and Δρ(H
ext) indicates that different systems of weak links between grain boundaries, which are capable of forming extended Josephson
contacts, undergo sequential transitions to a resistive state with an increase in H
ext. 相似文献
17.
Magnetoplastic effect in irradiated NaCl and LiF crystals 总被引:2,自引:0,他引:2
V. I. Al’shitz E. V. Darinskaya O. L. Kazakova 《Journal of Experimental and Theoretical Physics》1997,84(2):338-344
The effect of low x-ray irradiation doses (≈102 rad) on the magnetoplastic effect — the detachment of dislocations from paramagnetic centers under the action of an external
magnetic field B — in alkali-halide crystals has been investigated. The measurements were performed on LiF crystals and three types of NaCl
crystals, differing in impurity content. The dependence of the mean free path l of the dislocations on the rotational frequency ν of a sample in a magnetic field was especially sensitive to low irradiation doses. In unirradiated crystals this dependence
is a single-step dependence and is characterized by a critical frequency ν
c ∝B
2 above which the magnetoplastic effect is not observed. The frequency ν
c depends only on the type of paramagnetic centers, and not on their density. Even the lowest irradiation dose employed (<100
rad) leads to a sharp restructuring of the dependence l(ν), converting it into a two-step dependence (for edge dislocations) with an additional critical frequency ν
c2, that is insensitive to the irradiation dose, and that corresponds to the appearance of magnetically sensitive stoppers
of a new type under irradiation. The initial critical frequency ν
c1, as a rule, also varies with the dose, reflecting the change in state of the impurity complexes (Ca in NaCl and Mg in LiF).
Specifically, it is shown for NaCl(Ca) crystals that as the irradiation dose increases, the frequency ν
c1 increases, gradually approaching the value ν
c2, so that by the time the dose is ≈300 rad, the dependence l(ν) once again becomes a single-step dependence, dropping sharply only for ν⩾ν
c2. It is shown that the addition of a small number of Ni atoms to a NaCl crystal makes the Ca complexes radiation resistant,
and the critical frequency ν
c1 corresponding to them initially equals ν
c2 for crystals with no Ni. The recombination kinetics of radiation defects in the case in which the samples are irradiated
under a tungsten lamp was investigated. A possible physical model of the observed dependences is discussed.
Zh. éksp. Teor. Fiz. 111, 615–626 (February 1997) 相似文献
18.
There are various situations in which it is natural to ask whether a given collection of k functions, ρ
j
(r
1,…,r
j
), j=1,…,k, defined on a set X, are the first k correlation functions of a point process on X. Here we describe some necessary and sufficient conditions on the ρ
j
’s for this to be true. Our primary examples are X=ℝ
d
, X=ℤ
d
, and X an arbitrary finite set. In particular, we extend a result by Ambartzumian and Sukiasian showing realizability at sufficiently
small densities ρ
1(r). Typically if any realizing process exists there will be many (even an uncountable number); in this case we prove, when
X is a finite set, the existence of a realizing Gibbs measure with k body potentials which maximizes the entropy among all realizing measures. We also investigate in detail a simple example
in which a uniform density ρ and translation invariant ρ
2 are specified on ℤ; there is a gap between our best upper bound on possible values of ρ and the largest ρ for which realizability can be established. 相似文献
19.
Timothy M. Garoni Giovanni Ossola Marco Polin Alan D. Sokal 《Journal of statistical physics》2011,144(3):459-518
We study, via Monte Carlo simulation, the dynamic critical behavior of the Chayes–Machta dynamics for the Fortuin–Kasteleyn
random-cluster model, which generalizes the Swendsen–Wang dynamics for the q-state Potts ferromagnet to non-integer q≥1. We consider spatial dimension d=2 and 1.25≤q≤4 in steps of 0.25, on lattices up to 10242, and obtain estimates for the dynamic critical exponent z
CM. We present evidence that when 1≤q≲1.95 the Ossola–Sokal conjecture z
CM≥β/ν is violated, though we also present plausible fits compatible with this conjecture. We show that the Li–Sokal bound z
CM≥α/ν is close to being sharp over the entire range 1≤q≤4, but is probably non-sharp by a power. As a byproduct of our work, we also obtain evidence concerning the corrections to
scaling in static observables. 相似文献
20.
We consider the totally asymmetric simple exclusion process (TASEP) with two-sided Bernoulli initial condition, i.e., with
left density ρ
− and right density ρ
+. We study the associated height function, whose discrete gradient is given by the particle occurrences. Macroscopically one
has a deterministic limit shape with a shock or a rarefaction fan depending on the values of ρ
±. We characterize the large time scaling limit of the multipoint fluctuations as a function of the densities ρ
± and of the different macroscopic regions. Moreover, using a slow decorrelation phenomena, the results are extended from fixed
time to the whole space-time, except along the some directions (the characteristic solutions of the related Burgers equation)
where the problem is still open. 相似文献