共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
A. Banerjee M.K. Harbola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):201-206
Employing a near exact Hylleraas wavefunction we calculate various third-order nonlinear optical properties for the helium
atom within the time-dependent Kohn-Sham theory. In our calculations we employ the adiabatic local-density approximation (ALDA)
for the exchange and correlation kernels fxc and gxc, and compare the numbers obtained by us with the available accurate theoretical as well as experimental results. Our results
demonstrate the accuracy of ALDA for the calculation of nonlinear optical properties of many electron systems.
Received: 22 June 1998 / Accepted: 15 October 1998 相似文献
3.
The Heisenberg spin-S quantum antiferromagnet is studied near the large-spin limit, applying a new continuous unitary transformation which extends the usual Bogoliubov transformation to higher order in the 1/S-expansion of the Hamiltonian. This allows to diagonalize the bosonic Hamiltonian resulting from the Holstein-Primakoff representation
beyond the conventional spin-wave approximation. The zero-temperature flow equations derived from the extension of the Bogoliubov
transformation to order for the ground-state energy, the spin-wave velocity, and the staggered magnetization are solved exactly and yield results
which are in agreement with those obtained by a perturbative treatment of the magnon interactions.
Received: 19 March 1998 / Revised: 2 June 1998 / Accepted: 8 June 1998 相似文献
4.
A. Gold 《Zeitschrift für Physik B Condensed Matter》1993,91(3):397-401
We discuss interaction effects for the one-dimensional Bose gas with a repulsive delta-function interaction potential. We use the random-phase approximation and a finite local-field correction. Analytical results are given for the local-field correction, the pair-correlation function and the ground-state energy. The groundstate energy is found to be in much better agreement with the exact result than the ground-state energy calculated within the Bogoliubov approximation, where local-field corrections are neglected. 相似文献
5.
6.
Qinghu Chen Yuhang Ren Zhengkuan Jiao Kelin Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):59-63
The Feynman-Haken variational path integral theory is, for the first time, generalized to calculate the ground-state energy
of an electron coupled simultaneously to a Coulomb potential and to a longitudinal-optical (LO) phonon field in parabolic
quantum wires. It is shown that the polaronic correction to the ground-state energy is more sensitive to the electron-phonon
coupling constant than the Coulomb binding parameter and monotonically stronger as the effective wire radius decreases. We
apply our calculations to several semiconductor quantum wires and find that the polaronic correction can be considerably large.
Received 16 November 1998 相似文献
7.
A.K. Hartmann U. Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(1):105-109
We investigate the critical behavior of three-dimensional random-field Ising systems with both Gauss and bimodal distribution
of random fields and additional the three-dimensional diluted Ising antiferromagnet in an external field. These models are
expected to be in the same universality class. We use exact ground-state calculations with an integer optimization algorithm
and by a finite-size scaling analysis we calculate the critical exponents , , and . While the random-field model with Gauss distribution of random fields and the diluted antiferromagnet appear to be in same
universality class, the critical exponents of the random-field model with bimodal distribution of random fields seem to be
significantly different.
Received: 9 July 1998 / Received in final form: 15 July 1998 / Accepted: 20 July
1998 相似文献
8.
9.
J.-L. Zhu R. Lü X.-B. Wang X. Chen L. Chang F.-C. Pu 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):223-231
The tunneling behaviors of the magnetization vector are studied in ferromagnetic systems with trigonal and hexagonal crystal
symmetries, respectively. The Euclidean transition amplitudes between the energetically degenerate easy directions are evaluated
with the help of the dilute instanton-gas approximation. By using the effective Hamiltonian method, the ground-state tunneling
level splittings are clearly shown for each kind of symmetry and are found to depend on the parity of the total spin of the
ferromagnetic particle. The effective Hamiltonian method is demonstrated to be equivalent to the dilute instanton-gas approximation.
Possible relevance to experiments is discussed.
Received: 18 November 1997 / Revised: 18 March 1998 / Accepted: 6 April 1998 相似文献
10.
A.K. Hartmann 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):619-626
Large numbers of ground states of two-dimensional Ising spin glasses with periodic boundary conditions in both directions
are calculated for sizes up to 402. A combination of a genetic algorithm and Cluster-Exact Approximation is used. For each quenched realization of the bonds
up to 40 independent ground states are obtained. For the infinite system a ground-state energy of e
=-1.4015(3) is extrapolated. The ground-state landscape is investigated using a finite-size scaling analysis of the distribution of overlaps.
The mean-field picture assuming a complex landscape describes the situation better than the droplet-scaling model, where for
the infinite system mainly two ground states exist. Strong evidence is found that the ground states are not organized in an
ultrametric fashion in contrast to previous results for three-dimensional spin glasses.
Received 12 October 1998 相似文献
11.
W. Apel H.-U. Everts U. Körner 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):317-324
A coherent state representation for the electrons of ordered antiferromagnets is used to derive effective Hamiltonians for
the dynamics of holes in such systems. By an appropriate choice of these states, the constraint of forbidden double occupancy
can be implemented rigorously. Using these coherent states, one arrives at a path integral representation of the partition
function of the systems, from which the effective Hamiltonians can be read off. We apply this method to the t-J model on the square lattice and on the triangular lattice. In the former case, we reproduce the well-known fermion-boson
Hamiltonian for a hole in a collinear antiferromagnet. We demonstrate that our method also works for non-collinear antiferromagnets
by calculating the spectrum of a hole in the triangular antiferromagnet in the self-consistent Born approximation and by comparing
it with numerically exact results.
Received: 23 December 1997 / Accepted: 17 March 1998 相似文献
12.
G. I. Mironov 《Physics of the Solid State》2002,44(2):216-220
The ground-state energy of the two-sublattice two-dimensional Hubbard model is calculated in the static-fluctuation approximation with allowance for electron transfer from sites to next-to-nearest neighbor sites. In a specific case, the energy of the one-dimensional Hubbard model is calculated and compared with an exact solution. 相似文献
13.
《Physics letters. A》1997,229(2):113-116
An analytical treatment for the ground-state energy density of the system of one-dimensional fermions interacting via repulsive δ-function potential is presented. The treatment rests on a direct approximation to the pair distribution function and coupling constant integration. The analytical results, obtained for arbitrary coupling strength values, are in good agreement with those given by the numerical solution of an exact integral equation. 相似文献
14.
J. Mertz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):53-66
We present a simple model for calculating the fluorescence generated by the multi-photon excitation (MPE) of molecules in
solution. The model takes into account internal molecular dynamics such as ground-state depletion due to inter-system crossing
(ISC), as well as external molecular dynamics associated with diffusion into and out of an excitation volume confined in 3-dimensions.
Internal and external molecular dynamics are combined by using a technique of linearization of a modified diffusion equation
which takes into account the possibility of concentration depletion due to photobleaching. In addition, we discuss the phenomenon
of pulse saturation which effectively limits the molecular excitation rate constant in the case of short pulsed excitation.
Our results are specifically applied in the context of fluorescence autocorrelation functions and single-molecule detection.
In the latter case, we discuss some consequences of high-order multi-photon photobleaching. Finally, we include three appendices
to rigorously define the temporal and spatial profiles of an arbitrary excitation beam, and also to discuss some properties
of an exact evaluation of concentration depletion due to photobleaching.
Received: 9 March 1998 / Accepted: 20 April 1998 相似文献
15.
Ground-State Properties of Charged Bosons Confined in a One-Dimensional Harmonic Double-Well Trap: Diffusion Monte Carlo Calculations
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The diffusion Monte Carlo method is applied to study the ground-state properties of charged bosons in one dimension confined in a harmonic double-well trap. The particles interact repulsively through a Coulombic 1/r potential. Numerical results show that the well separation has significant influence on the ground-state properties of the system. When the interaction of the system is weak, ground-state energy decreases with the increasing well separation and has a minimal value. If the well separation increases continually~ the ground-state energy increases and approaches to a constant gradually. This effect will be abatable in the strong interacting system. In addition, by calculating the density of the systems for different interaction strengths with various well separations, we find that the density increases abnormally when the well separation is large at the centre of the system. 相似文献
16.
Weiqiang Yu Shiping Feng 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):265-269
The magnetic properties of the spin liquid state of the antiferromagnetic Heisenberg model on the kagomé lattice are investigated
within the self-consistent mean-field theory. The results show that the spin liquid ground-state energy per site is , which is in very good agreement with the best numerical estimates. The spin structure factor and spin susceptibility are
also discussed.
Received 1 December 1998 and Received in final form 12 April 1999 相似文献
17.
W. Michalke S. Kreitmeier 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):469-473
The diffusion Quantum-Monte-Carlo method of solving the Schr?dinger equation is applied to the vibrational ground state of
a polyethylene molecule. The results for the ground state energy show good agreement with normal mode analysis. In addition
to stretching, bending and torsional interaction van-der-Waals interaction is applied to a single chain showing a decrease
of the energy of 5%. The decrease for a polyethylene system of 5 chains with 10 atoms per molecule at the positions of a unit
cell is determined to be 4.8% per molecule. Finally first steps towards simulating excited states were performed.
Received: 9 February 1998 / Revised: 2 April 1998 / Accepted: 23 April 1998 相似文献
18.
Ajeeta Dhavale D.G. Kanhere C. Majumder G.P. Das 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(4):495-500
The ground-state geometries, energetics and the stability of
(
n
=1-12) clusters are studied using ab initio molecular dynamics method. Our results indicate that the ground-state geometries of large clusters () are different from those of clusters where a trivalent impurity Al is added to the same monovalent host Na. Other features observed are an early appearance
of 3-dimensional structure and a pentagonal growth path from n
=6 up to n
=11. As expected, the ground-state geometry of is not an icosahedron but can be viewed as a distorted form of one of the low lying geometries of cluster. In the energetically favored structures impurity atom Mg is never located at the center of the cluster. The stability
analysis based on the energetics shows (8 valence electrons) to be the most stable. In addition there is a remarkable even-odd pattern observed in the dissociation
energy and the second difference in energy which is absent in earlier studies of and clusters.
Received: 16 September 1998 / Received in final form: 15 February 1999 相似文献
19.
H. Schiessel 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):373-380
We investigate the bending of flexible charged membranes due to the presence of rigid rodlike macroions in the framework of
the Debye-Hückel approximation. When the macroions are fixed in space at some distance from the bilayer the membrane bends
towards them; we calculate the exact deformation profile. On the other hand a macroion which is adsorbed on the membrane causes
a deflection of the bilayer. Finally, we consider swollen lamellar polyanion/charged-lipid complexes where the macroions are
intercalated between charged lipid bilayers. We predict the occurrence of a double adsorption (pinching effect) of the macroion
for sufficiently flexible membranes.
Received: 9 February 1998 / Revised: 9 June 1998 / Accepted: 2 July 1998 相似文献
20.
The ground-state energy of a system of fermions can be calculated by minimizing a linear functional of the two-particle reduced density matrix (2-RDM) if an accurate set of N-representability conditions is applied. In this Letter we introduce a class of linear N-representability conditions based on exact calculations on a reduced active space. Unlike wave-function-based approaches, the 2-RDM methodology allows us to combine information from calculations on different active spaces. By adding active-space constraints, we can iteratively improve our estimate for the ground-state energy. Applying our methodology to a 1D Hubbard model yields a significant improvement over traditional 2-positivity constraints with the same computational scaling. 相似文献