共查询到20条相似文献,搜索用时 24 毫秒
1.
K. Hikami Y. Komori 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):583-588
Studied is the elliptic Ruijsenaars model, which is a difference analogue of the Calogero-Sutherland-Moser model. Using a
novel relationship between the elliptic Ruijsenaars operator and the transfer matrix of the Belavin model, we diagonalize
the Ruijsenaars operator by the algebraic Bethe ansatz method.
Received: 29 January 1998 / Accepted: 17 April 1998 相似文献
2.
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
3.
For multiphoton Jaynes-Cummings(JC) model Hamiltonian, we find its supersymmetric structure. Based on this, we introduce a supersymmetric unitary transformation to diagonalize the JC Hamiltonian, in so doing, its eigenvalues and eigenfunctions are obtained. The transition process is also calculated. 相似文献
4.
用超对称幺正变换解双光子过程的Jaynes-Cummings模型 总被引:1,自引:0,他引:1
本文发现了描写双光子过程的Jaynes-Cummings哈密顿量的超对称结构.根据超对称量子力学理论,引入了超对称幺正变换使其哈密顿量对角化.从而,得到了它的本征值、本征态,同时也计算了态的演化和跃迁几率. 相似文献
5.
《Nuclear Physics B》2001,592(3):512-562
A continuous sequence of infinitesimal unitary transformations is used to diagonalize the quantum sine-Gordon model for β2∈(2π,∞). This approach can be understood as an extension of perturbative scaling theory since it links weak- to strong-coupling behavior in a systematic expansion: a small expansion parameter is identified and this parameter remains small throughout the entire flow unlike the diverging running coupling constant of perturbative scaling. Our approximation consists in neglecting higher orders in this small parameter. We find very accurate results for the single-particle/hole spectrum in the strong-coupling phase and can describe the full crossover from weak to strong-coupling. The integrable structure of the sine-Gordon model is not used in our approach. Our new method should be of interest for the investigation of nonintegrable perturbations and for other strong-coupling problems. 相似文献
6.
We introduce supersymmetric unitary operators to directly diagonalize some generalized Jaynes-Cummings (J-C) Hamiltonians; which more deeply shows that supersymmetry is a natural language to depict the J-C model. 相似文献
7.
A Time-Dependent Approach to High-Resolution Photoabsorption Spectrum of Rydberg Atoms in Magnetic Fields
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A robust time-dependent approach to the high-resolution photoabsorption spectrum of Rydberg atoms in magnetic fields is presented. Traditionally we have to numerically diagonalize a huge matrix to solve the eigen-problem and then to obtain the spectral information. This matrix operation requires high-speed computers with large memories. Alternatively we present a unitary but very easily parallelized time-evolution method in an inexpensive way, which is very accurate and stable even in long-time scaie evolution. With this method, we perform the spectral caiculation of hydrogen atom in magnetic field, which agrees well with the experimentai observation. It can be extended to study the dynamics of Rydberg atoms in more complicated cases such as in combined electric and magnetic fields. 相似文献
8.
G. Abramovici 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(1):39-44
We introduce a new Non-Orthogonal Tight-Binding model, for complex alloys, in which electronic structure is characterized
by charge transfers. We give the analytic calculation of a charge transfer, in which overlapping two-center terms are rigorously
taken into account. Then, we apply numerically this result to an approximant phase of a quasicrystal of alloy. This model is more particularly adapted to transition metals, and gives realistic densities of states.
Received: 7 July 1997 / Revised: 10 March 1998 / Accepted: 3 April 1998 相似文献
9.
Qun Li 《International Journal of Theoretical Physics》2010,49(4):842-848
A new exactly solvable multiphoton generalized Jaynes-Cummings model is presented, whose Hamiltonian is related to the inverse
of field mode creation and annihilation operators. Then we use supersymmetric unitary operators to diagonalize the Hamiltonian
above and obtain their energy spectra and eigenstates. In addition, its pseudo-invariant eigen-operator is found as well,
directly leading to the corresponding energy-level gap. 相似文献
10.
A unitary operator U which can directly diagonalize the Hamiltonian of a ring of N coupled oscillators is found. With use of the technique of integration within an ordered product of operators we see that U includes a squeezing transformation. For large N it turns out that, except a zero-mode, the ring Hamiltonian has the same spectrum as the one-dimensional monatomic lattice model plus the Born-Von-Karmen boundary condition. The density matrix of this model is calculated by the U transformation, which further leads us to derive the heat capacity of the coupled oscillators in the large N limit. 相似文献
11.
A.O. Sousa S. Moss de Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(2):365-369
We introduce a square lattice into the Penna bit-string model for biological ageing and study the evolution of the spatial
distribution of the population considering different strategies of child-care. Two of the strategies are related to the movements
of a whole family on the lattice: in one case the mother cannot move if she has any child younger than a given age, and in
the other case if she moves, she brings these young children with her. A stronger condition has also been added to the second
case, considering that young children die with a higher probability if their mothers die, this probability decreasing with
age. We show that a highly non uniform occupation can be obtained when child-care is considered, even for an uniform initial
occupation per site. We also compare the standard survival rate of the model with that obtained when the spacial lattice is
considered (without any kind of child-care).
Received 30 October 1998 and Received in final form 27 November 1998 相似文献
12.
C.F. Lo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):93-95
Based upon the hidden Lie SU(1,1) symmetry, we have constructed the unitary decoupling transformation which diagonalizes the
multimode two-quantum Jaynes-Cummings model and provides us with an extremely convenient basis to gain a deeper understanding
of the dressing processes present in the matter-field interaction. This canonical transformation approach is very simple and
can be easily extended to other generalized Jaynes-Cummings models.
Received: 5 July 1997 / Revised: 3 November 1997 / Accepted: 14 November 1997 相似文献
13.
C. Ruyer-Quil P. Manneville 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):277-292
A new model of film flow down an inclined plane is derived by a method combining results of the classical long wavelength
expansion to a weighted-residuals technique. It can be expressed as a set of three coupled evolution equations for three slowly
varying fields, the thickness h, the flow-rate q, and a new variable that measures the departure of the wall shear from the shear predicted by a parabolic velocity profile. Results of a preliminary
study are in good agreement with theoretical asymptotic properties close to the instability threshold, laboratory experiments
beyond threshold and numerical simulations of the full Navier-Stokes equations.
Received: 16 April 1998 / Revised: 29 June 1998 / Accepted: 2 July 1998 相似文献
14.
T.M. Nieuwenhuizen C.N.A. van Duin 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):191-209
In realistic spinglasses, such as , and , magnetic atoms are located at random positions. Their couplings are determined by their relative positions. For such systems
a field theory is formulated. In certain limits it reduces to the Hopfield model, the Sherrington-Kirkpatrick model, and the
Viana-Bray model. The model has a percolation transition, while for RKKY couplings the “concentration scaling” occurs. Within the Gaussian approximation the Ginzburg-Landau expansion is considered in the clusterglass phase, that is
to say, for not too small concentrations. Near special points, the prefactor of the cubic term, or the one of the replica-symmetry-breaking
quartic term, may go through zero. Around such points new spin glass phases are found.
Received: 27 April 1998 / Received in final form: 27 July 1998 / Accepted: 13 August 1998 相似文献
15.
We introduce a supersymmetric unitary transformation, to diagonalize the multiphoton Jaynes–Cummings model Hamiltonian based on supersymmetric quantum mechanics theory, that includes any forms of intensity-dependent coupling and field nonlinearity. On doing so, we obtain its eigenvalue and eigenstates, and the time evolution of state vector. 相似文献
16.
J. Jimenez R. Rajagopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):237-243
We introduce a new simulation method, which we call the contact-distribution method, for the determination of the Helmholtz potential for polymer/colloid systems from lattice Monte-Carlo simulations. This
method allows one to obtain forces between finite or semi-infinite objects of any arbitrary shape and dimensions in the presence
of polymer chains in solution or physisorbed or chemisorbed at interfaces. We illustrate the application of the method using
two examples: (i) the interaction between the tip of an atomic force microscope (AFM) and a single, end-grafted polymer chain
and (ii) the interaction between an AFM tip and a polymer brush. Numerical results for the first two cases illustrate how
the method can be used to confirm and extend scaling laws for forces and Helmholtz potentials, to examine the effects of the
shapes and sizes of the objects and to examine conformational transitions in the polymer chains.
Received: 15 May 1998 / Revised: 11 June 1998 / Accepted: 12 June 1998 相似文献
17.
P. Entel R. Meyer K. Kadau H.C. Herper E. Hoffmann 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):379-388
Results are presented of first-principles total-energy calculations and molecular-dynamics simulations of structural transformations
in magnetic transition metal alloys like Fe1-xNix. While first-principles calculations allow to identify those structures having the lower total energy, molecular-dynamics
simulations can be used to trace out the dependence of the transformation on temperature, composition, concentration of defects
etc. We have used the method of the semi-empiric embedded-atom potential in the molecular-dynamics simulations which yields remarkable
good results for the structural changes.
Received: 3 February 1998 / Revised: 4 May 1998 / Accepted: 24 June 1998 相似文献
18.
P. Dommersnes S. Straumsnes E.G. Flekkøy T. Nicolai S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):669-677
We study the hydrodynamic properties of polymers and more generally self-similar structures using a new recursion model. The
hydrodynamic interaction between monomers is modeled by the standard Green's function of Stokes flow in which an ultrametric
distance is substituted for the usual Euclidean distance. This leads to a model where the long-range hydrodynamic interactions
and the long-range correlations of the polymer conformation can both be accounted for and yet allow for analytical solutions.
We explore the asymptotic as well as the finite size corrections to the scaling behavior with this model. In order to compare
the results of the present scheme with more conventional techniques a generalized version of the existing mean field results
by Kirkwood and Riseman for the hydrodynamic drag is introduced.
Received 26 August 1998 and Received in final form 7 December 1998 相似文献
19.
I. Mróz A. Pękalski 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):181-186
We propose a model suitable for investigating the conditions under which a population, adapted to a given environment, may
colonize a new neighbouring, spatially separated, habitat. We find out how similar the two regions must be for such a colonization
to succeed and what will be the spatial distribution of genetic pools of the two populations after the process. It is found
that between the two populations each adapted to the different region, a hybrid zone, characterized by increased heterozygosity,
may be formed. The dependence of the shape of the hybrid zone on the external (environmental) parameters is determined. When
the differences between the two regions are significant, the populations are separated by a depopulated zone. We show that
the conditions in the colonized habitat influence the genetic pool of the population living in the first region. Computer
simulations based on the standard Monte Carlo technique are used.
Received 11 December 1998 and Received in final form 17 December 1998 相似文献
20.
A model for ripple instabilities in granular media 总被引:1,自引:0,他引:1
O. Terzidis P. Claudin J.-P. Bouchaud 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):245-249
We extend the model of surface granular flow proposed in [#!bcre!#] to account for the effect of an external `wind', which
acts as to dislodge particles from the static bed, such that a stationary state of flowing grains is reached. We discuss in
detail how this mechanism can be described in a phenomenological way, and show that a flat bed is linearly unstable against
ripple formation in a certain region of parameter space. We focus in particular on the (realistic) case where the migration
velocity of the instability is much smaller than the grains' velocity. In this limit, the full dispersion relation can be
established. We relate the critical wave vector to the mean hopping length and to the ratio of the flight time to the `stick'
time. We provide an intuitive interpretation of the instability.
Received: 30 January 1998 / Revised: 12 May 1998 / Accepted: 8 June 1998 相似文献