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1.
The asymmetric simple exclusion process (ASEP) on a one-dimensional lattice is a system of particles which jump at ratesp and 1-p (herep > 1/2) to adjacent empty sites on their right and left respectively. The system is described on suitable macroscopic spatial
and temporal scales by the inviscid Burgers’ equation; the latter has shock solutions with a discontinuous jump from left
density ρ- to right density ρ+, ρ-< ρ +, which travel with velocity (2p−1 )(1−ρ+−p
−). In the microscopic system we may track the shock position by introducing a second class particle, which is attracted to
and travels with the shock. In this paper we obtain the time-invariant measure for this shock solution in the ASEP, as seen
from such a particle. The mean density at lattice siten, measured from this particle, approachesp
± at an exponential rate asn→ ±∞, witha characteristic length which becomes independent ofp when
. For a special value of the asymmetry, given byp/(1−p)=p
+(1−p
−)/p
−(1−p
+), the measure is Bernoulli, with densityρ
− on the left andp
+ on the right. In the weakly asymmetric limit, 2p−1 → 0, the microscopic width of the shock diverges as (2p+1)-1. The stationary measure is then essentially a superposition of Bernoulli measures, corresponding to a convolution of a density
profile described by the viscous Burgers equation with a well-defined distribution for the location of the second class particle. 相似文献
2.
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
3.
The electrical resistance of the binary liquid system cyclohexane + acetic anhydride is measured, in the critical region,
both in the pure mixture and when the mixture is doped with small amounts (≈ 100 ppm) of H2O/D2O impurities.T
c
was approached to aboutt=3×10−6 wheret=(T −T
c
)/T
c
. The critical exponentb ≈ 0.35 in the fit of the resistance data to the equationdR/dT ∼t
−b
does not seem to be affected appreciably by the impurities. There is a sign reversal ofdR/dt in the non-critical region. Binary liquid systems seem to violate the universality of the critical resistivity. 相似文献
4.
Variations in the temperature behavior of resistivity, ρ(T), in the ab plane of the anisotropic single-crystal high-T
c
superconductor BiSrCuO (2201 phase) have been observed at the insulator-metal (IM) transition. At low temperatures, as one
approaches the transition, the Mott relation for two dimensions, ln ρ ∝ T
−1/3, changes to ln ρ ∝ T
−1/2, which corresponds to hopping conduction with a Coulomb gap in the density of states. Negative temperature slopes were revealed
in the samples near the transition. Estimates suggest that superconductivity in these samples sets in from the Anderson insulator
state. The behavior of the width of the superconducting transition and of the temperature of its onset, T
con, at the IM transition has been studied from measurements of the ac magnetic susceptibility. It is shown that in the vicinity
of the IM transition the superconducting transition becomes broader, and the onset of the transition T
con shifts toward higher temperatures. This behavior is attributed to nonuniform superconductivity resulting from formation in
the crystal of superconducting droplets with different values of T
c
, which is caused by fluctuations in the local density of states due to the inherent disorder in the crystal. In these conditions,
superconductivity has a percolation character.
Fiz. Tverd. Tela (St. Petersburg) 40, 1190–1194 (July 1998) 相似文献
5.
Alexander G. Andreev Stefka G. Tsintsarska Maria Dimitrova-Ivanovich Ivaylo Polyanski Mladen Georgiev Alexander D. Gochev 《Central European Journal of Physics》2004,2(2):329-356
The temperatureT dependencies ρ(T) of normal state electric resistivitiesρ
c
(axial) andρ
ab
(in plane) of single-layer high-T
c
superconductors show common trends: AsT is raised, the resistivity first drops steeply before it starts rising αT above an apparent semiconductor-to-metal crossoverT
cross
. To analyze ρ(T) we plottT/ρ againstT at various dopingsx for bothρ
c
andρ
ab
.T/ρ is inversely proportional to the traversal time across a potential barrier as an ionic particle drifts in an electric field.
We findT/ρ in good agreement with theT dependence of the quantum rate of migrating particles: AsT is raised, a zero-point rate at the lowestT is extended to a nearly flat plateau before a thermally activated branch sets in. We also find evidence for the admixture
of 1- & 2-phonon absorptions below the Arrhenius range. These features shape the semiconductor-like branch below T
cross
. AboveT
cross
a metallic-like branch sets in, its αT character deriving from the field coupling of the migrating particle. Our analysis suggests that metal physics may not suffice
if ionic features play a role in transport. We attribute our conclusions to the drift of strong-coupling polarons along Cu−O
bonds. These “bond polarons” originate from carrier scattering by double-well potentials associated with the bonds. A bond
polaron dissociates to a free hole as it passes onto a neighboring O-O link. 相似文献
6.
Yu. N. Ovchinnikov 《Journal of Experimental and Theoretical Physics》1999,88(2):398-405
An expression is derived for the free energy of a superconductor near the critical temperature, taking account of the terms
of next highest order in the parameter 1−T/T
c. These terms become important for Ginzburg-Landau parameter values |κ−1|≪1, and in this case, in an external magnetic field H
0 close to H
c2, the structure of the order parameter is determined by the relative values of the three small parameters |κ−1|, 1−T/T
c, and (H
c2−H
0)/H
c2. Three types of lattices are investigated: triangular with one and two flux quanta per cell and square with one flux quantum
per cell.
Zh. éksp. Teor. Fiz. 115, 726–739 (February 1999) 相似文献
7.
M. A. Anisimov A. V. Bogach V. V. Glushkov S. V. Demishev N. A. Samarin V. B. Filipov N. Yu. Shitsevalova A. V. Kuznetsov N. E. Sluchanko 《Journal of Experimental and Theoretical Physics》2009,109(5):815-832
The magnetoresistance Δρ/ρ of single-crystal samples of praseodymium and neodymium hexaborides (PrB6 and NdB6) has been measured at temperatures ranging from 2 to 20 K in a magnetic field of up to 80 kOe. The results obtained have
revealed a crossover of the regime from a small negative magnetoresistance in the paramagnetic state to a large positive magnetoresistive
effect in magnetically ordered phases of the PrB6 and NdB6 compounds. An analysis of the dependences Δρ(H)/ρ has made it possible to separate three contributions to the magnetoresistance for the compounds under investigation. In
addition to the main negative contribution, which is quadratic in the magnetic field (−Δρ/ρ ∝ H
2), a linear positive contribution (Δρ/ρ ∝ H) and a nonlinear ferromagnetic contribution have been found. Upon transition to a magnetically ordered state, the linear
positive component in the magnetoresistance of the PrB6 and NdB6 compounds becomes dominant, whereas the quadratic contribution to the negative magnetoresistance is completely suppressed
in the commensurate magnetic phase of these compounds. The presence of several components in the magnetoresistance has been
explained by assuming that, in the antiferromagnetic phases of PrB6 and NdB6, ferromagnetic nanoregions (ferrons) are formed in the 5d band in the vicinity of the rareearth ions. The origin of the quadratic contribution to the negative magnetoresistance is
interpreted in terms of the Yosida model, which takes into account scattering of conduction electrons by localized magnetic
moments of rare-earth ions. Within the approach used, the local magnetic susceptibility χloc has been estimated. It has been demonstrated that, in the temperature range T
N < T < 20 K, the behavior of the local magnetic susceptibility χloc for the compounds under investigation can be described with good accuracy by the Curie-Weiss dependence χloc ∝ (T − Θ
p
)−1. 相似文献
8.
V. Fayaz H. Hossienkhani F. Felegary 《International Journal of Theoretical Physics》2012,51(8):2656-2664
We have investigated general Bianchi type I cosmological models which containing a perfect fluid and dark energy with time varying G and Λ that have been presented. The perfect fluid is taken to be one obeying the equation of state parameter, i.e., p=ωρ; whereas the dark energy density is considered to be either modified polytropic or the Chaplygin gas. Cosmological models admitting both power-law which is explored in the presence of perfect fluid and dark energy too. We reconstruct gravitational parameter G, cosmological term Λ, critical density ρ c , density parameter Ω, cosmological constant density parameter Ω Λ and deceleration parameter q for different equation of state. The present study will examine non-linear EOS with a general nonlinear term in the energy density. 相似文献
9.
Electron-doped (Ba1−x
La
x
)MnO3 compounds were prepared for x=0−0.5. Measurements of X-ray diffraction (XRD) at room temperature and temperature variation of dc electrical resistivity
down to 20 K were carried out. Samples with x=0.2–0.5 exhibit metal-insulator (M-I) transition. The maximum M-I transition temperature (T
c) of 289 K was observed for 30% of La doping (x=0.3). XRD patterns of these samples (x=0.2−0.5) were analyzed using Rietveld refinement. These samples are found to be mostly in single-phase form with orthorhombic
symmetry (space group Pbnm). We have found strong correlation between Mn-O-Mn bond angles and T
c of M-I transition. The resistivity data below T
c could be fitted to the expression ρ=ρ
1+ρ
2
T
2 and this shows that double exchange interaction plays a major role even in Mn4+-rich compound. Above T
c the resistivity data were fitted to variable range hopping and small polaron models. 相似文献
10.
A simple acceleration of convergence technique known as the ‘ε-convergence algorithm’ (ea) is applied to determine the critical temperatures and exponents. Several illustrations involving well-known series expansions
appropriate to two- and three-dimensional Ising models, three-dimensional Heisenberg models, etc., are given. Apart from this,
a few recently studied ferrimagnetic systems have also been analysed to emphasise the generality of the approach. Where exact
solutions are available, our estimates obtained from this procedure are in excellent agreement. In the case of other models,
the critical parameters we have obtained are consistent with other estimates such as those of the Padé approximants and group
theoretic methods.
The same procedure is applied to the partial virial series for hard spheres and hard discs and it is demonstrated that the
divergence of pressure occurs when the close-packing density is reached. The asymptotic form for the virial equation of state
is found to beP/ρkT ∼ (1 −ρ/ρ
c
−1 for hard spheres and hard discs.
Apart from the estimation of ‘critical parameters’, we have applied theea and the parametrised Euler transformation to sum the partial, truncated virial series for hard spheres and hard discs. The
resulting values of pressure so obtained, compare favourably with the molecular dynamics results. 相似文献
11.
Silver clad wires of highT
c superconductor Y1Ba2Cu3O7−x
have been fabricated through the powder metallurgy technique. The reacted wires show a midpointT
c of 84K. A critical current density of 26·4 A cm−2 (77K, 0T) is obtained in these wires. The wires, however, turn complete normal only at a current density of 280 A cm−2. The reasons for low critical current density obtained in these wires are discussed. 相似文献
12.
Electrical resistivity (ρ) of the amorphous (a-)Fe100−c
Zr
c
(c=8.5, 9.5 and 10) alloys has been measured in the temperature range 77 to 300 K, which embraces the second-order magnetic
phase transition at the Curie temperature point T
c. Analysis of the resistivity data particularly in the critical region reveals that these systems have a much wider range
of critical region compared to other crystalline ferromagnetic materials. The value of T
c and specific heat critical exponent, α has the same values as those determined from our earlier magnetic measurements. The value of α for all the present investigated alloys are in close agreement with the values predicted for three-dimensional (3D) Heisenberg
ferromagnet systems, which gives contradiction to the earlier results on similar alloys. It is observed from the analysis
that the presence of quenched disorder does not have any influence on critical behavior. 相似文献
13.
I. P. Nevirkovets 《Czechoslovak Journal of Physics》1996,46(Z2):647-648
Modified geometry (MG) devices, Nb/Al/Nb/Al−AlOx−Al−AlOx−Al/Nb/Al/Nb, have been fabricated and investigated in comparison with the basic geometry (BG) double-barrier Nb/Al−AlOx−Al−AlOx−Al/Nb devices. The enhancement of the critical temperature in the Al film is found to be weaker for the MG devices as compared
with the BG devices at temperatures nearT=4.2 K but stronger at lowT. Indication of an enhancement of dc Josephson critical current density,j
c
, at bias voltageV≠0 as compared withj
c
(V=0) has been observed in the MG devices for the first time. 相似文献
14.
L. S. Li W. Chen W. Dong X. S. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(2):189-193
Using Monte Carlo simulations and finite-size scaling, we
investigate the critical behavior of two-dimensional magnetic
lattice gas at densities ρ = 0.90, 0.95, 1.0. There is a
ferromagnetic phase transition at each density. As expected, the
critical temperature T
c
depends on system density ρ.
Unexpectedly, there is a density dependence of the critical
exponent of correlation length ν. For densities
ρ = 0.90,0.95,1.0, we obtain the inverse of critical exponent
1/ν = 0.835(5), 0.905(5), 1.00(1) respectively. It is found that
the ratios of critical exponent β/ν and γ/ν of
magnetization and susceptibility are independent of density. 相似文献
15.
V. Yu. Yushankhai 《Hyperfine Interactions》1989,50(1-4):775-779
On the basis of current theoretical views on the critical phenomena in isotropic Heisenberg ferromagnets the power temperature
behavior Λ=c(τ)λ0τ-w has been derived for the muon spin relaxation rate Λ as π-T
c
−1
(T-T
c
) → 0+. It is shown that the crossover from an exchange critical regime to a dipolar one is accompanied not only with the change
in the critical exponentw in the above law, but also with the reduction of the coefficientc(π). A comparison with the temperature behaviour of the inverse nuclear relaxation timet
R
−1
measured in the PAC experiment is carried out. 相似文献
16.
The heavy-fermion metal CePd1−x
Rh
x
can be tuned from ferromagnetism at x = 0 to the nonmagnetic state at some critical concentration x
c
. The non-Fermi liquid behavior (NFL) at x ≃ x
c
is recognized by the power-law dependence of the specific heat C(T) given by the electronic contribution susceptibility X(T) and volume expansion coefficient α(T) at low temperatures: C/T ∝ X(T) ∝ α(T)/T∝ 1/ √T. We also demonstrate that the behavior of the normalized effective mass M
N
*
observed in CePd1−x
Rh
x
at x ≃ 0.8 agrees with that of M
N
*
observed in paramagnetic CeRu2Si2 and conclude that these alloys exhibit the universal NFL thermodynamic behavior at their quantum critical points. We show
that the NFL behavior of CePd1−x
Rh
x
can be accounted for within the frameworks of the quasiparticle picture and fermion condensation quantum phase transition,
while this alloy exhibits a universal thermodynamic NFL behavior that is independent of the characteristic features of the
given alloy such as its lattice structure, magnetic ground state, dimension, etc.
The text was submitted by the authors in English. 相似文献
17.
G. O. Andrianov S. A. Nemov R. V. Parfen’ev D. V. Shamshur A. V. Chernyaev 《Physics of the Solid State》2010,52(9):1810-1814
This paper reports on a study of the low-temperature conductivity and parameters of the superconducting state, namely, the
critical temperature T
c
and the second critical magnetic field Hc2, in the (Pb0.3Sn0.7)0.95In0.05Te solid solution under hydrostatic pressure P ≤ 9 kbar at T = 4.2 K. The choice of this material has been motivated by the fact that, according to earlier observations, it undergoes
a superconducting transition at T
c
∼ 2.3 K, i.e., close to the maximum value T
c
∼ 2.9 K found for the (Pb
z
Sn1 − z
)0.95In0.05Te solid solutions with a lead content z ∼ 0.15–0.25. It has been demonstrated that an increase in the pressure to P ≤ 9 kbar leads to a bell-shaped dependence T
c
(P). The observed dependences are assigned to the effect of hydrostatic compression on the band structure of the solid solution
and indicate a shift in the position of the Fermi level E
F with increasing pressure within the impurity band of the In quasi-local states. In this case, E
F passes through a maximum in the density of impurity states at P = 3–5 kbar. 相似文献
18.
Marek Szydłowski Włodzimierz Godłowski Radosław Wojtak 《General Relativity and Gravitation》2006,38(5):795-821
In this paper we proposed to use the group of analysis of symmetries of the dynamical system to describe the evolution of the Universe. This method is used in searching for the unknown equation of state. It is shown that group of symmetries enforce the form of the equation of state for noninteracting scaling multifluids. We showed that symmetries give rise to the equation of state in the form p =-Λ + w
1ρ(a) + w
2
a
β + 0 and energy density ρ = Λ+ρ01
a
-3(1+w) +ρ02
a
α +ρ03
a
-3, which is commonly used in cosmology. The FRW model filled with scaling fluid (called homological) is confronted with the observations of distant type Ia supernovae. We found the class of model parameters admissible by the statistical analysis of SNIa data.We showed that the model with scaling fluid fits well to supernovae data. We found that Ωm,0 ≃ 0.4 and n ≃ -1 (β = -3n), which can correspond to (hyper) phantom fluid, and to a high density universe. However if we assume prior that Ωm,0 = 0.3 then the favoured model is close to concordance ΛCDM model. Our results predict that in the considered model with scaling fluids distant type Ia supernovae should be brighter than in the ΛCDM model, while intermediate distant SNIa should be fainter than in the ΛCDM model. We also investigate whether the model with scaling fluid is actually preferred by data over ΛCDM model. As a result we find from the Akaike model selection criterion: it prefers the model with noninteracting scaling fluid. 相似文献
19.
N. N. Loshkareva A. V. Korolev N. I. Solin E. V. Mostovshchikova S. V. Naumov N. V. Kostromitina A. M. Balbashov 《Journal of Experimental and Theoretical Physics》2009,108(1):88-97
The magnetic, electrical, and optical properties of Ca1 − x
Ce
x
MnO3 (x≤0.12) manganite single crystals are investigated with the aim of revealing the specific features of the multiphase electronic
and magnetic state as a function of the cerium concentration and the atmosphere used for growing single crystals. It is found
that the concentration dependence of the low-temperature magnetization M(x) of the single crystals is shifted toward the high-concentration range as compared to the corresponding dependence of the
polycrystals, which is explained by the predominant cation deficiency. The electrical resistivity and the reflection spectra
of the single crystals in the infrared spectral range indicate that charge carriers exhibit a band nature at temperatures
close to room temperature. The temperature dependence of the electrical resistivity of the single crystal with x = 0.08, which has the maximum magnetization in the studied series of Ca1 − x
Ce
x
MnO3 compounds, unlike polycrystals, exhibits a metallic behavior over the entire temperature range. The G-type antiferromagnetic phase with the Néel and Curie temperatures T
N(G) = T
C = 100 K is characterized by maxima of the electrical resistivity ρ and the magnetoresistance Δρ/ρ = |(ρ0 − ρ
H
)/ρ0| = 38% in the magnetic field H = 90 kOe. The magnetoresistance Δρ/ρ of the single crystals at cerium concentrations x = 0.10 and 0.12 with variations in temperature exhibit three specific features: near the temperature of charge ordering T
co, near the temperature of the magnetic phase transition to the C-type antiferromagnetic phase T
N(C), and near the temperature of the phase transition to the magnetic charge-ordered phase T
N(MCO). An anomalous temperature dependence of the magnetization is revealed for a single crystal with x = 0.10 grown in oxygen at a pressure of 5 atm, which is explained by the presence of regions with hole conductivity due to
cation deficiency. The inhomogeneous electronic and magnetic state is associated with the interrelation of the charge, orbital,
and spin orderings.
Original Russian Text ? N.N. Loshkareva, A.V. Korolev, N.I. Solin, E.V. Mostovshchikova, S.V. Naumov, N.V. Kostromitina, A.M.
Balbashov, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 135, No. 1, pp. 98–107. 相似文献
20.
Summary It is shown that the behaviour of the temperature dependence of the critical current in polycrystalline thin films of high-T
c superconductors depends crucially on the assumption made concerning the nature of the intergranular material. The usual assumption
of a superconductor-insulator-superconductor (=SIS) ?sandwich? between each grain leads to a crossover fromI
c∼(1−T/T
c) toI
c∼(1−T/T
c)3/2, for temperatures nearT
c (whereI
c is the critical current,T the absolute temperature, andT
c the superconducting transition temperature). Instead, for a superconductor-normal metal-superconductor (=SNS) sandwich the
dependenceI
c∼(1−T/T
c)2 is found for all temperatures. Consideration is given to the effect of self-magnetic field on the analysis. The comparison
between expressions for continuous and granular systems is extended.
Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction. 相似文献