共查询到20条相似文献,搜索用时 46 毫秒
1.
H. Mitter D. Robaschik 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):335-340
A complete thermodynamic treatment of the Casimir effect is presented. Explicit expressions for the free and the internal
energy, the entropy and the pressure are discussed. As an example we consider the Casimir effect with different temperatures
between the plates (T) resp. outside of them (T'). For T'<T the pressure of heat radiation can eventually compensate the Casimir force and the total pressure can vanish. We consider
both an isothermal and an adiabatic treatment of the interior region. The equilibrium point (vanishing pressure) turns out
instable in the isothermal case. In the adiabatic situation we have both an instable and a stable equilibrium point, if T'/T is sufficiently small. Quantitative aspects are briefly discussed.
Received 24 February 1999 and Received in final form 26 April 1999 相似文献
2.
H. Chamati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):241-249
The finite-size critical properties of the (n) vector ϕ4 model, with long-range interaction decaying algebraically with the interparticle distance r like r
-d - σ, are investigated. The system is confined to a finite geometry subject to periodic boundary condition. Special attention
is paid to the finite-size correction to the bulk susceptibility above the critical temperature T
c. We show that this correction has a power-law nature in the case of pure long-range interaction i.e. 0 < σ < 2 and it turns out to be exponential in case of short-range interaction i.e.σ = 2. The results are valid for arbitrary dimension d, between the lower ( d
< = σ) and the upper ( d
> = 2σ) critical dimensions.
Received 2 July 2001 and Received in final form 4 Septembre 2001 相似文献
3.
M.V. Moskalets 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):523-529
The peculiarities of a low temperature heat transfer through a ballistic quantum dot (a double potential barrier) with interacting
leads due to a long-range Coulomb interaction (in the geometrical capacitance approach) are considered. It is found that the
thermal conductance K shows periodic peaks as a function of the electrostatic potential of a dot at low temperatures. At the peak maximum it is
whereas near the minimum it is . Near the peak maximum the dependence K(T) is essentially nonmonotonic at the temperatures correspondent to the level spacing in the quantum dot.
Received 20 October 1999 and Received in final form 20 January 2000 相似文献
4.
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
5.
A.E. Allahverdyan Th.M. Nieuwenhuizen D.B. Saakian 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):317-335
In a p-spin interaction spherical spin-glass model both the spins and the couplings are allowed to change with time. The spins are
coupled to a heat bath with temperature T, while the coupling constants are coupled to a bath having temperature TJ. In an adiabatic limit (where relaxation time of the couplings is much larger that of the spins) we construct a generalized
two-temperature thermodynamics. It involves entropies of the spins and the coupling constants. The application for spin-glass
systems leads to a standard replica theory with a non-vanishing number of replicas, n=T/T
J
. For p>2 there occur at low temperatures two different glassy phases, depending on the value of n. The obtained first-order transitions have positive latent heat, and positive discontinuity of the total entropy. This is
an essentially non-equilibrium effect. The dynamical phase transition exists only for n<1. For p=2 correlation of the disorder (leading to a non-zero n) removes the known marginal stability of the spin glass phase. If the observation time is very large there occurs no finite-temperature
spin glass phase. In this case there are analogies with the non-equilibrium (aging) dynamics. A generalized fluctuation-dissipation
relation is derived.
Received 12 July 1999 and Received in final form 8 December 1999 相似文献
6.
We consider the Casimir force acting on a d-dimensional rectangular piston due to a massless scalar field with periodic, Dirichlet and Neumann boundary conditions and
an electromagnetic field with perfect electric-conductor and perfect magnetic-conductor boundary conditions. The Casimir energy
in a rectangular cavity is derived using the cut-off method. It is shown that the divergent part of the Casimir energy does
not contribute to the Casimir force acting on the piston, thus renders an unambiguously defined Casimir force acting on the
piston. At any temperature, it is found that the Casimir force acting on the piston increases from −∞ to 0 when the separation
a between the piston and the opposite wall increases from 0 to ∞. This implies that the Casimir force is always an attractive
force pulling the piston towards the closer wall, and the magnitude of the force gets larger as the separation a gets smaller. Explicit exact expressions for the Casimir force for small and large plate separations and for low and high
temperatures are computed. The limits of the Casimir force acting on the piston when some pairs of transversal plates are
large are also derived. An interesting result regarding the influence of temperature is that in contrast to the conventional
result that the leading term of the Casimir force acting on a wall of a rectangular cavity at high temperature is the Stefan–Boltzmann
(or black-body radiation) term which is of order T
d+1, it is found that the contributions of this term from the two regions separating the piston cancel with each other in the
case of piston. The high-temperature leading-order term of the Casimir force acting on the piston is of order T, which shows that the Casimir force has a nontrivial classical ℏ→0 limit. Explicit formulas for the classical limit are computed. 相似文献
7.
I.S. Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):43-46
Some metallic quantities are calculated on the grounds of Tsallis generalized statistics: the specific heat at constant volume,
c
V
(T); the chemical potential, ; the Pauli paramagnetic susceptibility, and the Korringa constant, . First it is found that for a general value of q, the Sommerfeld expansion series will exhibit both, odd and even terms, contrary to what is obtained if we use the Fermi-Dirac
(FD) statistics, where only even terms appear. It follows that: (i) the specific heat coefficient, , is q-dependent, but the temperature dependence of cV remains linear, as in the FD case; (ii) the Fermi energy, , differs from the chemical potential by a linear term in T, and not quadratic, as in FD, the same happening for ; (iii) the Korringa constant is q-dependent, but not
T-dependent. In the limit the results of FD statistics are recovered. Metallic thin films and multilayers exhibiting fractal surface structures are
possible systems where the present results could be tested.
Received 30 June 1999 and Received in final form 7 September 1999 相似文献
8.
E. Cappelluti C. Grimaldi L. Pietronero 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):511-517
In small Fermi energy metals, disorder can deeply modify superconducting state properties leading to a strong suppression
of the critical temperature Tc. In this paper, we show that also normal state properties can be seriously influenced by disorder when the Fermi energy E
F is sufficiently small. We calculate the normal state spin susceptibility χ for a narrow band electron-phonon coupled metal
as a function of the non-magnetic impurity scattering rate . We find that as soon as is comparable to E
F, χ is strongly reduced with respect to its value in the clean limit. The effects of the electron-phonon interaction including
the nonadiabatic corrections are discussed. Our results strongly suggest that the recent finding on irradiated MgB2 samples can be naturally explained in terms of small E
F values associated with the σ-bands of the boron plane, sustaining therefore the hypothesis that MgB2 is a nonadiabatic metal.
Received 31 July 2002 / Received in final form 21 September 2002 Published online 31 December 2002 相似文献
9.
B. M. Letfulov 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):423-428
Phase separation in the strongly correlated Falicov-Kimball model in infinite dimensions is examined. We show that the phase
separation can occur for any values of the interaction constant J* when the site energy of the localized electrons is equal to zero. Electron-poor regions always have homogeneous state and electron-rich regions
have chessboard state for , chessboard state or homogeneous state in dependence upon temperature for 0<J
*
<0.03 and homogeneous state for J
*
=0. For J
*
=0 and T=0, phase separation (segregation) occurs at .The obtained results are exact for the Bethe lattice with infinite number of the nearest neighbours.
Received 1 December 1998 and Received in final form 12 April 1999 相似文献
10.
A. Lambrecht S. Reynaud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):309-318
We study the influence of finite conductivity of metals on the Casimir effect. We put the emphasis on explicit theoretical
evaluations which can help comparing experimental results with theory. The reduction of the Casimir force is evaluated for
plane metallic plates. The reduction of the Casimir energy in the same configuration is also calculated. It can be used to
infer the reduction of the force in the plane-sphere geometry through the “proximity theorem”. Frequency dependent dielectric
response functions of the metals are represented either by the simple plasma model or, more accurately, by using the optical
data known for the metals used in recent experiments, that is Al, Au and Cu. In the two latter cases, the results obtained
here differ significantly from those published recently.
Received 30 July 1999 相似文献
11.
A fireball model with time evolution based on transport calculations is used to examine the dilepton emission rate of an ultra-relativistic
heavy-ion collision. A transition from hadronic matter to a quark-gluon plasma at a critical temperature T
C between 130-170 MeV is assumed. We also consider a possible mixed phase scenario. We include thermal corrections to the hadronic
spectra below T
C and use perturbation theory above T
C. The sensitivity of the spectra with respect to the freeze-out temperature, the initial fireball temperature and the critical
temperature is investigated.
Received: 4 August 2000 / Accepted: 14 November 2000 相似文献
12.
H. Kachkachi D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):291-300
Analytical calculations based on finite-size spin-wave theory and Monte Carlo (MC) simulations are performed to investigate
the validity of the well-known relation m(H, T) = M(H, T)B
D[M(H, T)
H/T] between the induced magnetization m of the magnetic particle and its intrinsic magnetization M for the Ising and isotropic classical models (B
D(x) is the Langevin function, D is the number of spin components, is the number of atoms in the particle). It follows from general arguments and from our analytical results for the Heisenberg
model at T≪T
c that this relation is not exact for any finite D and nonzero temperature. Nevertheless, corrections to this formula remain very small practically in the whole range T < T
c if ≫ 1, as confirmed by our Monte Carlo calculations. At T
T
c/4 there is a good agreement between the MC and finite-size spin-wave calculations for the field dependence of m and M for the Heisenberg model with free boundary conditions.
Received 1st December 2000 相似文献
13.
V.Yu. Irkhin M.I. Katsnelson 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):401-408
The longitudinal and transverse nuclear magnetic relaxation rates 1/T
1(T) and 1/T
2(T) are calculated for three- and two-dimensional (3D and 2D) metallic ferro- and antiferromagnets (FM and AFM) with localized
magnetic moments in the spin-wave temperature region. The contribution of the one-magnon decay processes is strongly enhanced
in comparison with the standard T-linear Korringa term, especially for the FM case. For the 3D AFM case this contribution diverges logarithmically, the divergence
being cut at the magnon gap ω due to magnetic anisotropy, and for the 2D AFM case as ω-1. The electron-magnon scattering processes yield T
2ln(T/ω) and T
2/ω1/2-terms in 1/T
1 for the 3D AFM and 2D FM cases, respectively. The two-magnon (“Raman”) contributions are investigated and demonstrated to
be large in the 2D FM case. Peculiarities of the isotropic 2D limit (where the correlation length is very large) are analyzed.
Received 29 November 1999 and Received in final form 6 June 2000 相似文献
14.
This is a companion paper to [DR1]. Using the method of continuous renormalization group around the Fermi surface and the
results of [DR1], we achieve the proof that a two-dimensional jellium system of interacting Fermions at low temperature T is a Fermi liquid above the BCS temperature. Following [S], this means proving analyticity in the coupling constant λ for
, where K is some numerical constant, and some uniform bounds on the derivatives of the self-energy.
Received: 27 July 1999 / Accepted: 31 May 2000 相似文献
15.
R. Bulla M. Potthoff 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):257-264
The Mott-Hubbard metal-insulator transition is studied within a simplified version of the Dynamical Mean-Field Theory (DMFT)
in which the coupling between the impurity level and the conduction band is approximated by a single pole at the Fermi energy.
In this approach, the DMFT equations are linearized, and the value for the critical Coulomb repulsion can be calculated analytically. For the symmetric single-band Hubbard model at zero temperature, the critical value is found
to be given by 6 times the square root of the second moment of the free (U=0) density of states. This result is in good agreement with the numerical value obtained from the Projective Selfconsistent
Method and recent Numerical Renormalization Group calculations for the Bethe and the hypercubic lattice in infinite dimensions.
The generalization to more complicated lattices is discussed. The “linearized DMFT” yields plausible results for the complete
geometry dependence of the critical interaction.
Received 6 May 1999 and Received in final form 2 July 1999 相似文献
16.
A. Pumir V.V. Barelko 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):71-77
Fronts of weakly exothermal chemical reaction may propagate in solids at very low temperatures ( 4K≤T≤77K) thanks to a quite unusual mechanism, involving a feedback between the heat produced by the reaction and the disruption of
the solid matrix. In this class of phenomena, the reaction may be induced by mechanical constraints, without a large elevation
of temperature. On the basis of a simple phenomenological model, we investigate ignition of a propagating front by initially
(i) disrupting a localized zone of the solid matrix, or by (ii) introducing a temperature jump, leading to a thermal shock
with strong temperature gradients. In particular, we show that reaction can be initiated by disrupting only a very small fraction
of the sample. Applications to the problem of initiation of solid explosives by friction or shocks is briefly discussed.
Received 26 January 2001 and Received in final form 3 May 2001 相似文献
17.
Y. Chen S.H. Guo Z.B. Li S. Marculescu L. Schülke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):289-296
The renormalisation group approach is applied to the study of the short-time critical behaviour of the d-dimensional Ginzburg-Landau model with long-range interaction of the form in momentum space. Firstly the system is quenched from a high temperature to the critical temperature and then relaxes to
equilibrium within the model A dynamics. The asymptotic scaling laws and the initial slip exponents and of the order parameter and the response function respectively, are calculated to the second order in .
Received 9 June 2000 and Received in final form 2 August 2000 相似文献
18.
M. Boström J.J. Longdell D.J. Mitchell B.W. Ninham 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):47-52
The nature of the resonance interaction between two isotropic atoms in an excited configuration is reinvestigated. The currently
accepted oscillatory form for the long-range retarded resonance interaction is shown to be a subtle artefact that arises due
to too drastic approximations. Formulation of the resonance interaction energy problem in terms of the interacting system leads to a form that it is ∝ r
-4 in the retarded limit. We also demonstrate that the resonance interaction energy at any finite temperature goes over to purely
classical long-range asymptote. This manifestation of the correspondence principle is due to thermal excitation of the electromagnetic
field. We finally discuss why the textbook result for the F?rster energy transfer between two atoms is incorrect for the same
reasons.
Received 31 January 2002 / Received in final form 25 July 2002 Published online 29 October 2002
RID="a"
ID="a"e-mail: mtb110@rsphysse.anu.edu.au 相似文献
19.
A. Politi S. Ruffo L. Tessieri 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):673-679
We have investigated numerically the quantum evolution of a -like wave-packet in a quenched disordered medium described by a tight-binding Hamiltonian with long-range hopping (band random
matrix approach). We have obtained clean data for the scaling properties in time and in the bandwidth b of the packet width and its fluctuations with respect to disorder realizations. We confirm that the fluctuations of the packet width in the steady-state show an anomalous
scaling [0pt] with [0pt] . This can be related to the presence of non-Gaussian tails in the distribution of [0pt]. Finally, we have analysed the steady state probability profile and we have found 1/b corrections with respect to the theoretical formula derived by Zhirov in the limit, except at the origin, where the corrections are .
Received 6 August 1999 and Received in final form 22 October 1999 相似文献
20.
D. Dantchev J. Rudnick 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):251-268
We study the behavior of systems in which the interaction contains a long-range component that does not dominate the critical
behavior. Such a component is exemplified by the van der Waals force between molecules in a simple liquid-vapor system. In
the context of the mean spherical model with periodic boundary conditions we are able to identify, for temperatures close
above T
c, finite-size contributions due to the subleading term in the interaction that are dominant in this region decaying algebraically as a function of L. This mechanism goes beyond the standard formulation of the finite-size scaling but is to be expected in real physical systems.
We also discuss other ways in which critical point behavior is modified that are of relevance for analysis of Monte Carlo
simulations of such systems.
Received 21 November 2000 and Received in final form 28 February 2001 相似文献