共查询到20条相似文献,搜索用时 31 毫秒
1.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
2.
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
3.
H. Chamati D.M. Dantchev 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):89-99
The finite size behavior of the susceptibility, Binder cumulant and some even moments of the magnetization of a fully finite
O(n) cubic system of size L are analyzed and the corresponding scaling functions are derived within a field-theoretic ɛ-expansion scheme under periodic
boundary conditions. We suppose a van der Waals type long-range interaction falling apart with the distance r as r
- (d + σ), where 2 < σ < 4, which does not change the short-range critical exponents of the system. Despite that the system belongs
to the short-range universality class it is shown that above the bulk critical temperature T
c the finite-size corrections decay in a power-in-L, and not in an exponential-in-L law, which is normally believed to be a characteristic feature for such systems.
Received 8 August 2001 相似文献
4.
The classical treatment of quasi-spherical vesicle undulations has, in the present work, been reviewed and extended to systems,
which are affected by a gravitational field caused by a density difference across the membrane. The effects have been studied
by the use of perturbation theory leading to corrections to the mean shape and the fluctuation correlation matrix. These corrections
have been included in an analytical expression for the flicker spectrum to probe how the experimentally accessible spectrum
changes with gravity. The results are represented in terms of the gravitational parameter, g
0 = ΔρgR
4/κ. The contributions from gravity are in most experimental situations small and thus negligible, but for values of g0 above a certain limit, the perturbational corrections must be included. Expressions for the relative error on the flicker
spectrum have been worked out, so that it is possible to define the regime where gravity is negligible. An upper limit of
g0 has also been identified, where the error in all modes of the flicker spectrum is significant due to distortion of the mean
shape.
Received 9 July 2002 and Received in final form 15 November 2002
RID="a"
ID="a"e-mail: jonas@kemi.dtu.dk
RID="b"
ID="b"e-mail: ipsen@memphys.sdu.dk 相似文献
5.
A. V. Smilga 《Communications in Mathematical Physics》2002,230(2):245-269
We start with some methodic remarks referring to purely bosonic quantum systems and then explain how corrections to the leading-order
quasiclassical result for the fermion-graded partition function Tr { (−1)
F
e
− β
H
} can be calculated at small β. We perform such a calculation for certain supersymmetric quantum mechanical systems where
such corrections are expected to appear. We consider in particular supersymmetric Yang–Mills theory reduced to (0 + 1) dimensions
and were surprised to find that the correction ∝ β2 vanishes in this case. We discuss also a nonstandard N=2 supersymmetric σ-model defined on S
3 and show that the quasiclassical expansion breaks down for this system.
Received: 12 December 2001 / Accepted: 29 January 2002?Published online: 11 September 2002 相似文献
6.
7.
E. Gotsman E. Levin U. Maor J. S. Miller 《The European Physical Journal C - Particles and Fields》2008,57(4):689-709
In this paper we develop an approach to soft scattering processes at high energies which is based on two elements: the Good–Walker
mechanism for low mass diffraction and multi-pomeron interactions for high mass diffraction. The principal idea, which allows
us to specify the theory for pomeron interactions, is that the so called soft processes occur at rather short distances (r
2
∝1/〈p
t
〉2
∝
α′ℙ≈0.01 GeV−2), where perturbative QCD is valid. The value of the pomeron slope α′ℙ is obtained from a fit to the experimental data. Using this theoretical approach, we suggest a model that fits all soft data
in the ISR-Tevatron energy range: total, elastic, single and double diffractive cross sections, as well as the t dependence of the differential elastic cross section, and the mass dependence of single diffraction. In this model we calculate
the survival probability of diffractive Higgs production, and we obtain a value for this observable that is smaller than 1%
at the LHC energy range. 相似文献
8.
E.T. Seppälä M.J. Alava 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(3):407-424
We study the effect of an external field on (1 + 1) and (2 + 1) dimensional elastic manifolds, at zero temperature and with
random bond disorder. Due to the glassy energy landscape the configuration of a manifold changes often in abrupt, “first order”-type
of large jumps when the field is applied. First the scaling behavior of the energy gap between the global energy minimum and
the next lowest minimum of the manifold is considered, by employing exact ground state calculations and an extreme statistics
argument. The scaling has a logarithmic prefactor originating from the number of the minima in the landscape, and reads ΔE
1∼L
θ[ln(L
z
L
- ζ)]-1/2, where ζ is the roughness exponent and θ is the energy fluctuation exponent of the manifold, L is the linear size of the manifold, and Lz is the system height. The gap scaling is extended to the case of a finite external field and yields for the susceptibility
of the manifolds ∼L
2D + 1 - θ[(1 - ζ)ln(L)]1/2. We also present a mean field argument for the finite size scaling of the first jump field, h
1∼L
d - θ. The implications to wetting in random systems, to finite-temperature behavior and the relation to Kardar-Parisi-Zhang non-equilibrium
surface growth are discussed.
Received December 2000 and Received in final form April 2001 相似文献
9.
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
10.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):85-90
A compartmentalized surface model of Nambu and Goto is studied on triangulated spherical surfaces by using the canonical Monte
Carlo simulation technique. One-dimensional bending energy is defined on the skeletons and at the junctions, and the mechanical
strength of the surface is supplied by the one-dimensional bending energy defined on the skeletons and junctions. The compartment
size is characterized by the total number L′ of bonds between the two-neighboring junctions and is assumed to have values in the range from L′ = 2 to L′ = 8 in the simulations, while that of the previously reported model is characterized by L′ = 1, where all vertices of the triangulated surface are the junctions. Therefore, the model in this paper is considered to
be an extension of the previous model in the sense that the previous model is obtained from the model in this paper in the
limit of L′↦1. The model in this paper is identical to the Nambu-Goto surface model without curvature energies in the limit of L′↦∞ and hence is expected to be ill-defined at sufficiently large L′. One remarkable result obtained in this paper is that the model has a well-defined smooth phase even at relatively large
L′ just as the previous model of L′↦ 1. It is also remarkable that the fluctuations of surface in the smooth phase are crucially dependent on L′; we can see no surface fluctuation when L′≤ 2, while relatively large fluctuations are seen when L′≥ 3. 相似文献
11.
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
12.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
13.
P. Pirooznia P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):291-296
We calculate the damping γq of collective density oscillations
(zero sound) in a
one-dimensional Fermi gas
with dimensionless forward scattering interaction
F and quadratic energy dispersion
k2 / 2 m at zero temperature.
Using standard many-body perturbation theory,
we obtain γq from the expansion
of the
inverse irreducible polarization to first order
in the effective screened (RPA) interaction.
For wave-vectors | q| /kF ≪F (where kF = m vF is the Fermi wave-vector)
we find to leading order γq ∝| q |3 /(vF m2).
On the other hand, for F ≪| q| /kF most of the spectral weight
is carried by the particle-hole continuum, which is
distributed over a frequency interval of the order of q2/m.
We also show that zero sound damping
leads to a finite maximum proportional to
|k - kF | -2 + 2 η
of the charge peak in the single-particle
spectral function, where η is the anomalous
dimension. Our prediction agrees with photoemission data for
the blue bronze K0.3MoO3.
We comment on other recent calculations of γq. 相似文献
14.
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
15.
We consider corrections to scaling within an approximate theory developed by Mazenko for nonconserved order parameter in the
limit of low (d → 1) and high (d → ∞) dimensions. The corrections to scaling considered here follows from the departures of the initial condition from the
scaling morphology. Including corrections to scaling, the equal time correlation function has the form: C(r, t) = f
0(r/L)+L
−ω
f
1(r/L)+…, where L is a characteristic length scale (i.e. domain size). The correction-to-scaling exponent ω and the correction-to-scaling functions f
1(x) are calculated for both low and high dimensions. In both dimensions the value of ω is found to be ω = 4 similar to 1D Glauber model and OJK theory (the theory developed by Ohta, Jasnow and Kawasaki). 相似文献
16.
I. E. Mazets J. Schmiedmayer 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):335-339
We provide a simple physical picture of the loss of coherence between two coherently split one-dimensional Bose-Einstein condensates.
The source of the dephasing is identified with nonlinear corrections to the elementary excitation energies in either of the
two independent condensates. We retrieve the result by Burkov, Lukin and Demler [Phys. Rev. Lett. 98, 200404 (2007)] on the subexponential decay of the coherence ∝exp [-(t/t0)2/3] for the large time t, however, the scaling of t0 differs. 相似文献
17.
P.-E. Roche B. Castaing B. Chabaud B. Hébral J. Sommeria 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):405-408
In Rayleigh Bénard experiments, the side wall conductivity is traditionally taken into account by subtracting the empty cell
heat conductivity from the measured one. We present a model showing that the correction to apply could be considerably larger.
We compare to experiments and find good agreement. One of the consequences is that the Nusselt behavior for Ra < 1010 could be closer to Nu∝Ra
1/3 than currently assumed. Also, the wall effect can appear as a continuous change in the γ exponent Nu∝Ra
γ.
Received 26 April and Received in final form 1st October 2001 相似文献
18.
C. Monthus T. Garel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):39-45
The directed polymer in a 1+3 dimensional
random medium is known to present a disorder-induced phase
transition. For a polymer of length L, the high temperature
phase is characterized by a diffusive behavior for the end-point
displacement R2 ∼L and by free-energy fluctuations of order
ΔF(L) ∼O(1). The low-temperature phase is characterized by
an anomalous wandering exponent R2/L ∼Lω and
by free-energy fluctuations of order ΔF(L) ∼Lω
where ω∼0.18. In this paper, we first study the scaling
behavior of various properties to localize the critical temperature
Tc. Our results concerning R2/L and ΔF(L) point towards
0.76 < Tc ≤T2=0.79, so our conclusion is that Tc is equal
or very close to the upper bound T2 derived by Derrida and
coworkers (T2 corresponds to the temperature above which the ratio
remains finite as L ↦
∞). We then present histograms for the free-energy, energy and
entropy over disorder samples. For T ≫Tc, the free-energy
distribution is found to be Gaussian. For T ≪Tc, the free-energy
distribution coincides with the ground state energy distribution, in
agreement with the zero-temperature fixed point picture. Moreover the
entropy fluctuations are of order ΔS ∼L1/2 and follow a
Gaussian distribution, in agreement with the droplet predictions,
where the free-energy term ΔF ∼Lω is a near
cancellation of energy and entropy contributions of order L1/2. 相似文献
19.
B. G. Zakharov 《JETP Letters》1997,65(8):615-620
The induced gluon radiation of a high-energy quark in a finite-size QCD medium is studied. For a sufficiently energetic quark
produced inside a medium we find the radiative energy loss ΔE
q∝L
2, where L is the distance traveled by quark in the medium. It has a weak dependence on the initial quark energy E
q. The L
2 dependence turns to L
1 as the quark energy decreases. Numerical calculations are performed for a cold nuclear matter and a hot quark-gluon plasma.
For a quark incident on a nucleus we predict ΔE
q
≈0.1E
q
(L/10fm)
β
, with β close to unity.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 585–589 (25 April 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
20.
Using a scaling approach we consider a 2D comb copolymer brush under bending deformations. We show that the rectilinear brush
is locally stable and can be characterized by a persistence length λ increasing with the molecular weight of grafting side
chains as λ ∼ M3. A bending instability due to redistribution of the side chains appears in the non-linear regime where bending is strong.
Arguments are presented that the brush conformations consist of alternating rectilinear and bent sections corresponding to
the different free-energy minima. 相似文献