共查询到20条相似文献,搜索用时 109 毫秒
1.
V. Hizhnyakov H. Kaasik I. Tehver 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):271-276
A nonperturbative theory of the multiphonon relaxation of a localized vibrational mode, caused by a high-order anharmonic
interaction with the nearest atoms of the crystal lattice, is proposed. It relates the rate of the process to the positive
frequency part of the time-dependent non-stationary displacement correlation function of atoms. The nonlinear integral equation
for this function is derived and solved numerically. We have found that the rate exhibits a critical behavior: it sharply
increases near a specific (critical) value(s) of the interaction; the corresponding dependence is characterized by the critical
index k - 1, where k is the number of the created phonons.
Received 2 May 2002 Published online 31 July 2002 相似文献
2.
G.J. Rodgers Y.J. Yap 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):129-132
A model of herding is introduced which is exceptionally simple, incorporating only two phenomena, growth and addition. At
each time step either (i) with probability p the system grows through the introduction of a new agent or (ii) with probability q = 1 - p a free agent already in the system is added at random to a group of size k with rate Ak. Two versions of the model, A
k = k and A
k = 1, are solved and in both versions we find two different types of behaviour. When p > 1/2 all the moments of the distribution of group sizes are linear in time for large time and the group distribution is
power-law. When p < 1/2 the system runs out of free agents in a finite time.
Received 12 February 2002 Published online 9 July 2002 相似文献
3.
V.Yu. Irkhin M.I. Katsnelson 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):481-486
Peculiarities of transport properties of three- and two-dimensional half-metallic ferromagnets are investigated, which are
connected with the absence of spin-flip scattering processes. The temperature and magnetic field dependences of resistivity
in various regimes are calculated. The resistivity is proportional to T
9/2 for T < T
* and to T
7/2 for T > T
*, T* being the crossover temperature for longitudinal scattering processes. The latter scale plays also an important role in magnetoresistance.
The contribution of non-quasiparticle (incoherent) states to the transport properties is discussed. It is shown that they
can dominate in the temperature dependence of the impurity-induced resistivity and in the tunnel junction conductivity.
Received 16 September 2002 / Received in final form 6 November 2002 Published online 31 December 2002 相似文献
4.
A. Fioretti E. Arimondo A. Crubellier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):219-225
The measurements of fine-structure changing collisions in a cesium magneto-optical trap, reported in a previous work [A. Fioretti
et al., Phys. Rev. A 55, R3999 (1997)], are reanalyzed within a model based on the flux enhancement effect, which takes place in cold atomic collisions.
In the present analysis, we consider the cooperative effect of the long-range and the shorter-range excitation by the strong
trap laser. We evidence also the important role of the hyperfine structure of the Cs2 molecular levels asymptotically connected to the ground-state and excited-state dissociation limits.
Received 22 July 1999 and Received in final form 4 May 2000 相似文献
5.
B. Mazzi F. Okkels J.C. Vassilicos 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):243-251
We present a shell-model of fractal induced turbulence which predicts that structure function scaling exponents decrease in
absolute value as the fractal dimension of the turbulence-inducing fractal object increases. This qualitative prediction is
in agreement with laboratory measurements. Finer details of the fractal induced turbulence statistics and dynamics depend
on the fractal force's phases, i.e. on the detailed construction of the fractal stirrer. In a case of deterministic forcing phases, a critical fractal dimension
exists below which the average rate of inter-scale energy transfer <T
n> is a decreasing function of the wavenumber kn and the structure function scaling exponents take close to Kolmogorov values. Above this critical fractal dimension, <T
n> is an increasing function of kn and the structure function scaling exponents deviate significantly from Kolmogorov values.
Received 25 June 2001 / Received in final form 5 April 2002 Published online 19 July 2002 相似文献
6.
G. Zet 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):405-408
A model of spherically symmetric SU(2) gauge theory is considered. The self-duality equations are written and it is shown that they are compatible with the Einstein-Yang-Mills
equations. It is proven that the SU(2) gauge model is self-dual on a Schwarzschild space-time but not on a Reissner-Nordstr?m one.
Received: 24 May 2002 / Accepted: 1 July 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: gzet@phys.tuiasi.ro
Communicated by A. Sch?fer 相似文献
7.
O. Filippov K.H. Ringhofer B.I. Sturman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):285-290
Analytically and numerically we investigate the dependence of the first Fourier harmonics of the space-charge field, induced
in an AC-biased sillenite crystal by a light-interference pattern, on the light contrast m. It is shown that within the whole contrast range, 0 < m < 1, these dependences are controlled by the only scalar parameter - the space-charge wave quality factor Q. In the low-contrast limit, m Q
-2, this factor defines the degree of enhancement of the nonlinear response while for larger contrasts it characterizes strong
saturation effects. The data obtained are compared with the results of the previous studies of the AC-response. The possibilities
of experimental detection of predicted dependences and their possible implications are discussed.
Received 13 September 2002 / Received in final form 27 December 2002 Published online 11 February 2003 相似文献
8.
H. Takeda R. Aoyagi M. Matsushita T. Shiosaki 《Applied Physics A: Materials Science & Processing》2003,76(2):295-297
The crystal structure of sodium bismuth tantalate, Na0.5Bi2.5Ta2O9, was analyzed by the powder X-ray-diffraction Rietveld method. The distribution of Na atoms was found to be ordered in the
A site of the pseudo-perovskite (ATa2O7)2- blocks. The piezoelectric properties were effectively examined using dense bulk ceramics containing manganese oxide as the
dopant. The electromechanical coupling coefficients (kij) and the electrical quality factors (Qm) are kp=10%, k31=8.3%, kt=19.7%, and Qm=3000.
Received: 1 July 2002 / Accepted: 3 July 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +81-743-726069, E-mail: hiro-t@ms.aist-nara.ac.jp 相似文献
9.
J.O. Andersen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):389-396
We consider an interacting homogeneous Bose gas at zero temperature in two spatial dimensions. The properties of the system
can be calculated as an expansion in powers of g, where g is the coupling constant. We calculate the ground state pressure and the ground state energy density to second order in the
quantum loop expansion. The renormalization group is used to sum up leading and subleading logarithms from all orders in perturbation
theory. In the dilute limit, the renormalization group improved pressure and energy density are expansions in powers of the
T
2B and T
2Bln(T
2B), respectively, where T
2B is the two-body T-matrix.
Received 19 April 2002 Published online 13 August 2002 相似文献
10.
Cocco S Marko JF Monasson R Sarkar A Yan J 《The European physical journal. E, Soft matter》2003,10(3):249-263
The elastic response of flexible polymers made of elements which can be either folded or unfolded, having different lengths
in these two states, is discussed. These situations are common for biopolymers as a result of folding interactions intrinsic
to the monomers, or as a result of binding of other smaller molecules along the polymer length. Using simple flexible-chain
models, we show that even when the energy ε associated with maintaining the folded state is comparable to k
B
T, the elastic response of such a chain can mimic usual polymer linear elasticity, but with a force scale enhanced above that
expected from the flexibility of the chain backbone. We discuss recent experiments on single-stranded DNA, chromatin fiber
and double-stranded DNA with proteins weakly absorbed along its length which show this effect. Effects of polymer semiflexiblity
and torsional stiffness relevant to experiments on proteins binding to dsDNA are analyzed. We finally discuss the competition
between electrostatic self-repulsion and folding interactions responsible for the complex elastic response of single-stranded
DNA.
Received 7 August 2002 and Received in final form 7 March 2003 / Published online: 15 April 2003
RID="a"
ID="a"e-mail: jmarko@uic.edu 相似文献
11.
M. Takigawa M. Ichioka K. Machida 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):303-311
Thermal conductivity κ
xx(T) under a field is investigated in d
x2 - y2-wave superconductors and isotropic s-wave superconductors by the linear response theory, using a microscopic wave function of the vortex lattice states. To study
the origin of the different field dependence of κxx(T) between higher and lower temperature regions, we analyze the spatially-resolved thermal conductivity around a vortex at
each temperature, which is related to the spectrum of the local density of states. We also discuss the electric conductivity
in the same formulation for a comparison.
Received 8 December 2001 and Received in final form 20 March 2002 Published online 6 June 2002 相似文献
12.
Kostakis K Mourmouris S Charalabidis D Pitsikalis M 《The European physical journal. E, Soft matter》2003,10(1):55-63
Linear polyisoprenes having dimethylamine end groups were prepared by high vacuum anionic polymerization techniques using
3-dimethylaminopropyllithium as the initiator. The amine group was reacted with 2-cholesteryl-2-oxo-1,3,2-dioxaphospholane
to provide polymer chains having end zwitterionic groups chemically connected with cholesterol. The association behavior of
these end-functionalized polymers was studied in cyclohexane by low angle laser light scattering, dynamic light scattering,
and viscometry. The aggregation numbers, N
w were found to decrease by increasing the molecular weight of the precursor polymer, due to excluded volume repulsions. The
ability of cholesterol to form liquid crystal mesophases facilitated the association process leading to higher N
w values. The hydrodynamic behavior of the aggregates was similar to that of star polymers. The dependence of the N
w values on the molecular weight of the base polymer, the polydispersity of the associates and the absence of critical micelle
concentration, cmc are compatible with the linear head-packing model.
Received 29 April 2002 and Received in final form 13 November 2002 Published online: 11 March 2003 相似文献
13.
M. Samsel-Czekała G. Kontrym-Sznajd G. Döring W. Schülke J. Kwiatkowska F. Maniawski S. Kaprzyk A. Bansil 《Applied Physics A: Materials Science & Processing》2003,77(1):87-92
A reconstruction technique based on the solution of the Radon transform in terms of Jacobi polynomials is used to obtain the
3D electron momentum density, ϱ(p), from nine high-resolution Compton profiles (CPs) for a Cu0.9Al0.1 disordered alloy single crystal. The method was also applied to theoretical CPs computed within the Korringa–Kohn–Rostoker
coherent potential approximation (KKR-CPA) first-principles scheme for the same nine orientations of the crystal. The experimental
ϱ(p) is in satisfactory agreement with the theoretical ϱ(p), shows most details of the Fermi surface (FS) and exhibits electron correlation effects. We comment on the map of the FS
obtained by folding the reconstructed ϱ(p) into the first Brillouin zone, which yields the occupation number density, ϱ(k). A test of the validity of data via a consistency condition (within our reconstruction algorithm) as well as the propagation
of experimental noise in the reconstruction of both ϱ(p) and ϱ(k) are investigated.
Received: 24 October 2001 / Accepted: 20 January 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +48-71/344-10-29, E-mail: samsel@int.pan.wroc.pl 相似文献
14.
S. Boettcher 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):29-39
The average ground state energy and entropy for ±J spin glasses on Bethe lattices of connectivities k + 1 = 3..., 26 at T = 0 are approximated numerically. To obtain sufficient accuracy for large system sizes (up to n = 212), the Extremal Optimization heuristic is employed which provides high-quality results not only for the ground state energies
per spin ek+1 but also for their entropies sk+1. The results indicate sizable differences between lattices of even and odd connectivities. The extrapolated ground state
energies compare very well with recent one-step replica symmetry breaking calculations. These energies can be scaled for all
even connectivities k + 1 to within a fraction of a percent onto a simple functional form, e
k + 1 = E
SK
- (2E
SK + )/, where E
SK = - 0.7633 is the ground state energy for the broken replica symmetry in the Sherrington-Kirkpatrick model. But this form
is in conflict with perturbative calculations at large k + 1, which do not distinguish between even and odd connectivities. We also find non-zero entropies per spin sk+1 at small connectivities. While sk+1 seems to vanish asymptotically with 1/(k + 1) for even connectivities, it is numerically indistinguishable from zero already for odd k + 1 ≥ 9.
Received 9 August 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: sboettc@emory.edu www.physics.emory.edu/faculty/boettcher 相似文献
15.
B. Pilawa I. Keilhauer G. Fischer S. Knorr J. Rahmer A. Grupp 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):321-330
The magnetic properties of the cyclic compound [Fe6(bicine)6] LiClO4
. 2MeOH are reported. The cluster Fe6(bicine)6 forms an antiferromagnetically coupled ring structure of Fe III ions. The magnetic susceptibility is measured between 2 and 300 K and yields the exchange coupling of J/k
B = - 27.5±0.5 K. The field dependence of the magnetic moment is studied at 3 and 6 K in magnetic fields up to 5 T. The zero-field
splitting of the first excited spin states with S = 2 and 3 are determined by ESR at 94 GHz. The intra-molecular interactions of the Fe III ions are analyzed and the on-site anisotropy of the Fe III due to the ligand-configuration is determined to d /k
B = - 0.633±0.008K.
Received 28 October 2002 / Received in final form 22 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: bernd@piobelix.physik.uni-karlsruhe.de 相似文献
16.
K. Lagergren B. Cederwall A. Johnson J. Blomqvist D. Sohler G. de Angelis P. Bednarczyk T. Bäck T. Claesson O. Dorvaux E. Farnea A. Gadea M. Górska L. Milechina L.-O. Norlin A. Odahara M. Palacz I. Stefanescu O. Thelen J.P. Vivien 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):393-396
The first evidence for excited states in 95Ag is presented. 95Ag is the heaviest T
z = 1/2 nucleus for which gamma-rays have been identified. The reaction 40Ca(58Ni, 1p2n)95Ag was used in the experiment, which resulted in the assignment of three gamma-rays to 95Ag. A detector system consisting of the detector arrays Euroball, Neutron Wall and Euclides was used to detect gamma-rays,
neutrons and charged particles, respectively.
Received: 31 May 2002 / Accepted: 8 July 2002 相似文献
17.
J. Dietel T. Koschny W. Apel W. Weller 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):439-445
We reconsider the theory of the half-filled lowest Landau level using the Chern-Simons formulation and study the grand-canonical
potential in the random-phase approximation (RPA). Calculating the unperturbed response functions for current- and charge-density
exactly, without any expansion with respect to frequency or wave vector, we find that the integral for the ground-state energy
converges rapidly (algebraically) at large wave vectors k, but exhibits a logarithmic divergence at small k. This divergence originates in the k-2 singularity of the Chern-Simons interaction and it is already present in lowest-order perturbation theory. A similar divergence
appears in the chemical potential. Beyond the RPA, we identify diagrams for the grand-canonical potential (ladder-type, maximally
crossed, or a combination of both) which diverge with powers of the logarithm. We expand our result for the RPA ground-state
energy in the strength of the Coulomb interaction. The linear term is finite and its value compares well with numerical simulations
of interacting electrons in the lowest Landau level.
Received: 19 February 1998 / Revised: 25 March 1998 / Accepted: 17 April 1998 相似文献
18.
D.H. Setiadi G.A. Chass L.L. Torday A. Varro J.Gy. Papp I.G. Csizmadia 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):609-618
The molecular conformations of shortened molecular models of vitamin E (tocopherol and tocotrienol) and their sulfur and selenium
congeners were studied computationally at the DFT level of theory [B3LYP/6-31G(d)]. The sequence of stabilization by the various
heteroatoms was found to be the following: O∼Se > S. On the basis of the present structural results it seems that the seleno-congener of vitamin E is a distinct possibility.
Received 9 May 2002 / Received in final form 9 July 2002 Published online 13 September 2002 相似文献
19.
S. Abriet D. Karevski 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):77-82
We study the non-equilibrium time evolution of the average transverse magnetisation and end-to-end correlation functions of
the random Ising quantum chain. Starting with fully magnetised states, either in the x or z direction, we compute numerically the average quantities. They show similar behaviour to the homogeneous chain, that is an
algebraic decay in time toward a stationary state. During the time evolution, the spatial correlations, measured from one
end to the other of the chain, are building up and finally at long time they reach a size-dependent constant depending on
the distance from criticality. Analytical arguments are given which support the numerical results.
Received 11 July 2002 / Received in final form 9 September 2002 Published online 29 October 2002 相似文献
20.
N.H. Damrauer C. Dietl G. Krampert S.-H. Lee K.-H. Jung G. Gerber 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):71-76
Adaptive femtosecond laser pulse shaping is employed to achieve bond selective photodissociation/photoionization of CH2ClBr in the gas phase. The photoproduct signal measured in a reflectron time-of-flight mass spectrometer is used as feedback
to improve iteratively the spectral phases of the laser pulse via an evolutionary algorithm. We observe an increase of the fission of the stronger versus the weaker carbon halogen bond by 100%. Single parameter control schemes proved unable to achieve bond-selectivity. The complexity
of the control problem is addressed by mapping it onto the well-known problem of maximizing second-harmonic generation (SHG).
Further spectroscopic results indicate that the control involves manipulation of wave-packet dynamics on the neutral surfaces.
Received 21 December 2001 / Received in final form 2 April 2002 Published online 28 June 2002 相似文献