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991.
992.
993.
A.V. Prokofiev F. Büllesfeld W. Assmus H. Schwenk D. Wichert U. Löw B. Lüthi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):313-316
Experimental results on magnetic resonance (ESR) and magnetic susceptibility are given for single crystalline (VO)2P2O7. The crystal growth procedure is briefly discussed. The susceptibility is interpreted numerically using a model with alternating
spin chains. We determine J
=51 K and . Furthermore we find a spin gap of meV from our ESR measurements. Using elastic constants no indication of a phase transition forcing the dimerization is seen
below 300 K.
Received: 22 December 1997 / Accepted: 17 March 1998 相似文献
994.
M. Hinczewski A. N. Berker 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):461-472
The anisotropic d=3 tJ model is studied by
renormalization-group theory, yielding the evolution of the system
as interplane coupling is varied from the isotropic
three-dimensional to quasi-two-dimensional regimes.
Finite-temperature phase diagrams, chemical potential shifts, and
in-plane and interplane kinetic energies and antiferromagnetic
correlations are calculated for the entire range of electron
densities. We find that the novel τ phase, seen in earlier
studies of the isotropic d=3 tJ model, persists even for
strong anisotropy. While the τ phase appears at low
temperatures at 30–35% hole doping away from 〈
ni〉=1, at smaller hole dopings we see a complex lamellar
structure of antiferromagnetic and disordered regions, with a
suppressed chemical potential shift, a possible marker of
incommensurate ordering in the form of microscopic stripes. An
investigation of the renormalization-group flows for the isotropic
two-dimensional tJ model also shows a clear pre-signature of the
τ phase, which in fact appears with finite transition
temperatures upon addition of the smallest interplane coupling. 相似文献
995.
T. Hirano 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):19-22
We can establish a new picture, the perfect fluid sQGP core and the dissipative hadronic corona, of the space-time evolution
of produced matter in relativistic heavy-ion collisions at RHIC. It is also shown that the picture works well also in the
forward rapidity region through an analysis based on a new class of the hydro-kinetic model and that this is a manifestation
of the rapid increase of the entropy density in the vicinity of QCD critical temperature, namely, deconfinement. 相似文献
996.
T. Verkholyak A. Honecker W. Brenig 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):283-287
The Jordan-Wigner transformation is applied to study the ground
state properties and dimerization transition in the J1-J2
XXZ chain. We consider different solutions of the mean-field
approximation for the transformed Hamiltonian. Ground state
energy and the static structure factor are compared with complementary
exact diagonalization and good agreement is found
near the limit of the Majumdar-Ghosh model.
Furthermore, the ground state phase diagram is discussed
within the mean-field theory. In particular, we show that an
incommensurate ground state is absent for large J2 in a fully
self-consistent mean-field analysis. 相似文献
997.
K. Lochmann A. Anikeenko A. Elsner N. Medvedev D. Stoyan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):67-76
The performance of various structure characteristics in
the task of indicating structural peculiarities in packings of
hard spheres is investigated. Various characteristics based on
Voronoi polyhedra, spherical harmonics, and Delaunay simplices are
considered together with the pair correlation function and the
mean number of r-close triples. They are applied to a set of
hard sphere packings of density φ from 0.62 to 0.72. It turns
out that all used structure characteristics are able to indicate
changes of order from non-crystalline to crystalline packings.
However, not all of them are sensitive enough to indicate
different stages of structure transformation under densification.
The characteristics based on Delaunay simplices turn out to be the
most sensitive for this purpose.
For the models considered three principal structure classes are
found: packings of densities lower than the known critical value
0.64 showing a non-crystalline behavior; packings with
considerable crystalline regions for φ up to 0.66–0.67;
rather complete crystals although with numerous defects for φ
above 0.67. 相似文献
998.
Charles R. Ross II 《Journal of statistical physics》1987,49(1-2):261-268
As an analysis of the development of first-order behavior in two-dimensional Ising lattices, the square lattice with antiferromagnetic nearest-neighbor interactions and a ferromagnetic next-nearest-neighbor interaction in the (11) direction has been modeled. The phase diagram was calculated for a range of interaction parameters and imposed fields; the calculations were performed using the cluster variation method (CVM). Analysis of the calculations suggests that no first-order behavior is developed in this system, so that higher dimensionality or connectivities are required before such behavior is developed. 相似文献
999.
R. J. Baxter 《Journal of statistical physics》2005,120(1-2):1-36
An outstanding problem in statistical mechanics is the order parameter of the chiral Potts model. An elegant conjecture for this was made in 1983. It has since been successfully tested against series expansions, but there is as yet no proof of the conjecture. Here we show that if one makes a certain analyticity assumption similar to that used to derive the free energy, then one can indeed verify the conjecture. The method is based on the ‘‘broken rapidity line’’ approach pioneered by Jimbo et al. (J. Phys. A 26:2199--2210 (1993).). 相似文献
1000.
R. Andrade F. Grassi Y. Hama T. Kodama O. Socolowski jr. B. Tavares 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):23-26
Elliptic flow at RHIC is computed event by event with NeXSPheRIO. Reasonable agreement with experimental results on v
2(η) is obtained. Various effects are studied as well: reconstruction of impact parameter direction, freeze-out temperature,
equation of state (with or without crossover), emission mechanism. 相似文献