共查询到20条相似文献,搜索用时 31 毫秒
1.
Loncarević I Budinski-Petković Lj Vrhovac SB 《The European physical journal. E, Soft matter》2007,24(1):19-26
Random sequential adsorption of binary mixtures of extended objects on a two-dimensional triangular lattice is studied numerically
by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding random walks on the lattice. We concentrate
here on the influence of the symmetry properties of the shapes on the kinetics of the deposition processes in two-component
mixtures. Approach to the jamming limit in the case of mixtures is found to be exponential, of the form: θ(t) ∼ θjam - Δθ exp(- t/σ), and the values of the parameter σ are determined by the order of symmetry of the less symmetric object in the mixture.
Depending on the local geometry of the objects making the mixture, jamming coverage of a mixture can be either greater than
both single-component jamming coverages or it can be in between these values. Results of the simulations for various fractional
concentrations of the objects in the mixture are also presented. 相似文献
2.
N. Moussa 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):193-196
Using computer simulations, we show that metastable states still
occur in two-lane traffic models with slow to start rules.
However, these metastable states no longer exist in systems where
aggressive drivers (which do not look back before changing
lanes) are present. Indeed, the presence of only one aggressive
driver in the circuit, triggers the breakdown of the high flow
states. In these systems, the steady state is unique and its
relaxation dynamics should depend on the lane changing probability
pch and the number of aggressive drivers present in the
circuit. It is found also that the relaxation time τ diverges
as the form of a power-law: τ∝pch
-β, β=1.
89.40.+k 相似文献
3.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
4.
J. H. Brewer M. Celio D. R. Harshman R. Keitel S. R. Kreitzman G. M. Luke D. R. Noakes R. E. Turner E. J. Ansaldo C. W. Clawson K. M. Crowe C. Y. Huang 《Hyperfine Interactions》1986,31(1-4):191-197
Muon spin relaxation in low (weak) longitudinal magnetic field (LLF-μSR) provides a means of independently determining the
static dipolar width Δ characterizing the μ+ lattice site and the correlation time τc for μ+ hopping, in a manner that is nearly model-independent for τc and especially accurate in the near-static limit (τc>τμ). The advantages of this method are illustrated by its application to muon hopping in Cu near the τc maximum around 50 K. 相似文献
5.
I.M. Sokolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):369-373
We consider two-particle dispersion in a velocity field, where the relative two-point velocity scales according to v
2(r) ∝r
α and the corresponding correlation time scales as τ(r) ∝r
β, and fix α = 2/3, as typical for turbulent flows. We show that two generic types of dispersion behavior arize: For α/2 +
β < 1 the correlations in relative velocities decouple and the diffusion approximation holds. In the opposite case, α/2 +
β > 1, the relative motion is strongly correlated. The case of Kolmogorov flows corresponds to a marginal, nongeneric situation.
In this case, depending on the particular parameters of the flow, the dispersion behavior can be rather diffusive or rather
ballistic.
Received 13 March 2001 相似文献
6.
We compute the dynamical structure factor S(q,τ) of an elastic medium where force dipoles appear at random in space and in time, due to “micro-collapses” of the structure.
Various regimes are found, depending on the wave vector q and the collapse time θ. In an early-time regime, the logarithm of the structure factor behaves as (qτ)3/2, as predicted in L. Cipelletti, S. Manley, R.C. Ball, D.A. Weitz, Phys. Rev. Lett. 84, 2275 (2000) using heuristic arguments. However, in an intermediate-time regime we rather obtain a (qτ)5/4 behaviour. Finally, the asymptotic long-time regime is found to behave as q
3/2τ. We also give a plausible scenario for aging, in terms of a strain-dependent energy barrier for micro-collapses. The relaxation
time is found to grow with the age t
w, quasi-exponentially at first, and then as t
w
4/5 with logarithmic corrections.
Received 23 July 2001 相似文献
7.
β-γ-γ directional correlation studies for the cascades (i)β-rays ofE
max=0.12 MeV,γ-rays of 557 keV andγ-rays of 53 keV and (ii)β-rays ofE
max=0.21 MeV,γ-rays of 444 keV andγ-rays of 53 keV have been made. The triple correlation functionsW(θ) were obtained to beW(θ)=1+(−0.153±0.031)P
2(cosθ)+(0.004±0.035)P
4(cosθ) forβ-rays ofE
max 0.12 MeV→557→53 keV cascade andW(θ)=1+(0.163±0.042)P
2(cosθ)+(−0.035±0.058)P
4(cosθ) forβ rays ofE
max=0.21 MeV→444 keV→53 keV cascade.
Spins and parities of the 650, 537 and 93 keV levels of103Rh are deduced by triple angular correlation and the internal conversion coefficient studies. Multipolarities of the transitions
are also determined. 相似文献
8.
Dephasing in open quantum chaotic systems has been investigated in the limit of large system sizes to the Fermi wavelength
ratio, L/λF 〉 1. The weak localization correction g
wl to the conductance for a quantum dot coupled to (i) an external closed dot and (ii) a dephasing voltage probe is calculated
in the semiclassical approximation. In addition to the universal algebraic suppression g
wl ∝ (1 + τD/τϕ)−1 with the dwell time τD through the cavity and the dephasing rate τ
ϕ
−1
, we find an exponential suppression of weak localization by a factor of ∝ exp[−
/τϕ], where
is the system-dependent parameter. In the dephasing probe model,
coincides with the Ehrenfest time,
∝ ln[L/λF], for both perfectly and partially transparent dot-lead couplings. In contrast, when dephasing occurs due to the coupling
to an external dot,
∝ ln[L/ξ] depends on the correlation length ξ of the coupling potential instead of λF.
The text was submitted by the authors in English. 相似文献
9.
The specific features of the dielectric spectra of statistical mixtures in the form of heterogeneous systems with spherical
particles chaotically arranged in the space have been investigated. The distribution function of relaxation times f(τ) has been restored. It has been established that the relaxation times are continuously distributed within a wide interval
[τ1, τ2]. Different methods for broadening the relaxation time distribution interval and approximating the relaxation time distribution
function f(τ) have been analyzed. It has been demonstrated that f(τ) is a nonmonotonic function with two maxima at the boundaries and a minimum in the vicinity of the midpoint of the interval
[τ1, τ2]. These features of the relaxation time distribution function are responsible for the large difference between the average
relaxation frequencies of the permittivity and the dielectric loss (electrical conductivity). 相似文献
10.
We compute the dynamical structure factor S(q,τ) of an elastic medium where force dipoles appear at random in space and in time, due to “micro-collapses” of the structure.
Various regimes are found, depending on the wave vector q and the collapse time θ. In an early time regime, the logarithm of the structure factor behaves as (qτ)3/2, as predicted in (L. Cipelletti et al., Phys. Rev Lett. 84, 2275 (2000)) using heuristic arguments. However, in an intermediate-time regime we rather obtain a (qτ)5/4 behaviour. Finally, the asymptotic long-time regime is found to behave as q
3/2τ. We also give a plausible scenario for aging, in terms of a strain-dependent energy barrier for micro-collapses. The relaxation
time is found to grow with the age tw, quasi-exponentially at first, and then as t
w
4/5 with logarithmic corrections.
Received 15 April 2002 相似文献
11.
Jai Kumar Singhal 《Pramana》2004,62(5):1029-1040
We examine the effects of mixing induced light heavy charged lepton neutral currents on the partial wave amplitude for the
process l+l− →ZZ (withl = e,μ or τ). By imposing the constraints that the amplitude should not exceed the perturbative unitarity limit at high energy (√s
= Λ), we obtain bounds on light heavy charged lepton mixing parameter sin2(2θ
L
a
) where θ
L
a
is the mixing angle of the ordinary charged lepton with its exotic partner. For Λ = 1 TeV, no bound is obtained on sin2 (2θ
L
a
) form
E < 0.69 TeV. However, sin2 (2θ
L
a
) ≤ 1.52×10−5 form
E = 5 TeV, sin2 (2θ
L
a
) ≤ 2.41 ×10−7 form
E = 10 TeV. Similarity for Λ = ∞ no bound is obtained on sin2 (2θ
L
a
) for mE < 1.97 TeV and sin2 (2θ
L
a
) ≤ 0.15 form
E = 5 TeV and sin2 (2θ
L
a
) ≤ 3.88×10-2 form
E = 10 TeV. 相似文献
12.
13.
W. Osak 《Applied Physics A: Materials Science & Processing》1997,65(3):263-264
d ∝t-s, where s<1 at the initial state and s>1 at the final state of the sample depolarisation. The loss peak frequency 1/τp exhibits an activation character of ωp∝exp(-E/kT) with E=0.25 eV in the direction of the a -axis and E=0.56 eV for the c-axis.
Received: 13 February 1997/Accepted: 7 April 1997 相似文献
14.
Matsuta K. Minamisono T. Tanigaki M. Onishi T. Fukuda M. Mihara M. Akai H. Sasaki M. Yamaguchi T. Miyake T. Sato K. Minamisono K. Ha C. Tanaka K. Kidera K. Morishita A. Kaminaka S. Tsubota T. Sumikama T. Kitagawa A. Torikoshi M. Kanazawa M. Nishio T. Koda S. Ohtsubo T. Nojiri Y. Momota S. Hanna S.S. Alonso J.R. Krebs G.F. Symons T.J.M. 《Hyperfine Interactions》1999,120(1-8):719-723
The Knight shifts K for short-lived β emitters 12N and 27Si implanted in Pt have been measured by means of β-NMR technique. The results were K(12N in Pt)= +(5.8 ± 2.1)× 10-4 and K(27Si in Pt)= +(1.4 ± 0.8)× 10-3. The spin–lattice relaxation time T1 was measured for 12N in Pt. The result was T1(12N in Pt, T=300 K)= 66 ± 8 ms, thus, T1T= 20 ± 2 Ks. The present Knight shifts are in good agreement with the KKR band structure calculation with local lattice relaxation
determined theoretically.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
A. Díaz-Sánchez A. Pérez-Garrido 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):483-486
The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional
Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, f (t) = f
0exp - (t/τ)β
, with the exponent β increasing with the temperature. The relaxation time diverges as an Arrhenius law when T→ 0.
Received 24 May 2001 and Received in final form 12 September 2001 相似文献
16.
Isothermal remanent magnetization decay,M
r(t), and ‘in-field’ growth of zero-field-cooled magnetization,M
ZFC(t), with time have been measured over four decades in time at temperatures ranging from 0.25T
c to 1.25T
c (whereT
c is the Curie temperature, determined previously for the same sample from static critical phenomena measurements) for a nearly
ordered intermetallic compound Ni3Al, which is an experimental realization of a three-dimensional (d = 3) ferromagnet with weak quenched random-exchange disorder. None of the functional forms ofM
r(t) predicted by the existing phenomenological models of relaxation dynamics in spin systems with quenched randomness, but only
the expressions
and
closely reproduce such data in the present case. The most striking features of magnetic relaxation in the system in question
are as follows: Aging effects are absent in bothM
r
t andM
ZFC(t) at all temperatures in the temperature range covered in the present experiments. A cross-over in equilibrium dynamics from
the one, characteristic of a pured = 3 ferromagnet with complete atomic ordering and prevalent at temperatures away from Tc, to that, typical of ad = 3 random-exchange ferromagnet, occurs asT → Tc. The relaxation times τ1(T)(τ1
′(T)) and τ2(T)(τ2
′(T)) exhibit logarithmic divergence at critical temperatures
and
;
and
both increase with the external magnetic field strength,H, such that at any given field value,
. The exponent characterizing the logarithmic divergence in τ
1
′
(T) and τ
2
′
T possesses a field-independent value of ≃16 for both relaxation times. Of all the available theoretical models, the droplet
fluctuation model alone provides a qualitative explanation for some aspects of the present magnetic relaxation data 相似文献
17.
J. Kaupužs R. V.N. Melnik J. Rimshans 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):363-370
Monte Carlo simulations of magnetization and susceptibility in the 3D XY
model are performed for system sizes up to L=384 (significantly exceeding the
largest size L=160 considered in work published previously), and fields h
≥ 0.0003125 at two different coupling constants β=0.5, and
β=0.55 in the ordered phase. We examine the prediction of the standard
theory that the longitudinal susceptibility χ∥ has a Goldstone mode singularity
such that χ∥ ∝h-1/2 holds when h↦0. Most
of our results, however, support another theoretical prediction that the
singularity is of a more general form χ∥ ∝hρ-1,
where 1/2<ρ<1 is a universal exponent related to the ∼hρ
variation of the magnetization. 相似文献
18.
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
19.
I. N. Izosimov V. G. Kalinnikov A. A. Solnyshkin 《Physics of Particles and Nuclei Letters》2008,5(5):427-431
A strength function for the β+/EC decay of the deformed 160g
Ho (25.6 min) nucleus has been obtained from experimental data. The fine structure of the strength function S
β(E) is analyzed. It is found to have a pronounced resonant structure for Gamow-Teller transitions. In S
β(E) with μτ = +1 the Gamow-Teller resonance has been observed to split into two components. This splitting is associated with anisotropy
of isovector density oscillation in deformed nuclei. The β+/EC strength function for first-forbidden transitions is obtained in the Coulomb (ξ) approximation. It is shown that S
β(E) for first-forbidden transitions does not have a pronounced resonant structure.
The text was submitted by the authors in English. 相似文献
20.
I. M. Suslov 《Journal of Experimental and Theoretical Physics》2010,111(3):450-465
The previously-obtained analytical asymptotic expressions for the Gell-Mann-Low function β(g) and anomalous dimensions in the ϕ4 theory in the limit g → ∞ are based on the parametric representation of the form g = f(t), β(g) = f
1(t) (where t ∝ g
0−1/2 is the running parameter related to the bare charge g
0), which is simplified in the complex t plane near a zero of one of the functional integrals. In this work, it has been shown that the parametric representation
has a singularity at t → 0; for this reason, similar results can be obtained for real g
0 values. The problem of the correct transition to the strong-coupling regime is simultaneously solved; in particular, the
constancy of the bare or renormalized mass is not a correct condition of this transition. A partial proof has been given for
the theorem of the renormalizability in the strong-coupling region. 相似文献