critical dynamics below the percolation threshold the critical dynamics of the diluted two dimensional ising model below the percolation threshold is studied the dynamics exhibits a crossover from a concentration dependent behaviour for xi t xi p to a percolating lattice type behaviour for xi t xi p where xi t and xi p are the thermal and percolation correlation lengths respectively as a consequence the dynamical exponents a and b are shown to be the limits of dynamical functions a x and b x respectively here x ln xi p ln xi t extensive monte carlo simulations support our predictions

breakdown of dynamic scaling at the percolation threshold the critical dynamics of the two dimensional ising model at the bond percolation threshold is investigated by monte carlo simulations on a 64 64 lattice conventional dynamic scaling breaks down at low temperatures the logarithm of the relaxation time depends quadratically upon the logarithm of the thermal correlation length the coefficients of the quadratic and linear terms are 0 51 and 3 25 respectively the results are compared with recent experimental and analytic work

critical crossover phenomena in disordered ising systems the author has investigated the critical behaviour of site disordered ising systems over a large range of dilution 0 6 or p or 1 0 investing about 1015 single spin flips with conventional local dynamics critical temperatures have been determined with high precision using the cumulant method the finite size simulations lead to concentration dependent exponents which seem to violate universality the author shows that the concentration dependence is induced by a crossover phenomenon which governs a large interval of the critical region the author finds that the scaling functions of systems with different disorder converge asymptotically to universal behaviour consistent with the fixed point of weak disorder

on the completeness of photon added coherent states we demonstrate explicitly the completeness of photon added coherent states pacss introduced by agarwal and tara agarwal g s and tara k 1991 phys rev a 43 492 and defined up to normalization by m z m 0 1 2 where is the boson creation operator and z are conventional glauber klauder coherent states we find the analytical form of the positive weight function in their resolution of unity by solving the associated stieltjes power moment problem we furnish an example of generation of another set of pacss which are complete

non universality in the dynamics at the percolation threshold the dynamical behavior of the two dimensional ising model at the site percolation threshold on l l lattices with l or 64 is studied by monte carlo simulations the results are consistent with the recently proposed singular dynamic scaling the new dynamical exponents are estimated to be as 0 62 or 0 12 and bs 3 92 or 0 89 comparison with bond dilution strongly suggests that universality is violated for this model

the ising model on a saw using a renormalization group calculation the authors show that the most probable value of the static correlation function of the ising model on a saw decays as a stretched exponential with an exponent equal to the dimension d of the saw they prove that the thermal exponent vt equals d 1 on the basis of extensive monte carlo simulations they conclude that the spin spin autocorrelation function also decays as a stretched exponential they find evidence for a breakdown of dynamical scaling

construction of photon added spin coherent states and their statistical properties in the present work we construct and investigate some properties of the photon added spin coherent states pa scss the klauder s minimal set of conditions required to obtain coherent states are discussed we give the analytical form for the positive weight function in the resolution of unity finally we examine the statistical properties of the pa scss in terms of different parameters using the mandel s q parameter all these quantities are expressed in terms of hypergeometric and meijer g functions and so the pa scss are a new field of application for these functions

breakdown of dynamic scaling in the 2d diluted potts model the recently found breakdown of dynamic scaling of the kinetic ising model at the percolation threshold is here shown to be exhibited also by the single spin flip dynamical q state potts model the authors find a q mod a 2 2 q 1 mod q in good agreement with very recent monte carlo simulations

accuracy and stability of integration algorithms for elastoplastic constitutive relations an analysis of accuracy and stability of algorithms for the integration of elastoplastic constitutive relations is carried out in this paper reference is made to a very general internal variable formulation of plasticity and to two families of algorithms that generalize the well known trapezoidal and midpoint rules to fit the present context other integration schemes such as the radial return mean normal and closest point procedures are particular cases of this general formulation the meaning of first and second order accuracy in the presence of the plastic consistency condition is examined in detail and the criteria derived are used to identify two second order accurate members of the proposed algorithms a general methodology is also derived whereby the numerical stability properties of integration schemes can be systematically assessed with the aid of this methodology the generalized midpoint rule is seen to have far better stability properties than the generalized trapezoidal rule finally numerical examples are presented that illustrate the performance of the algorithms

critical dynamics of the one dimensional potts model uses the method developed by achiam and kosterlitz 1978 to obtain the dynamical critical exponent of the one dimensional q state potts model the author finds z 3 q 2 and z 2 q 2 thus confirming lower bound estimates found previously

application of a domain decomposition method to elastoplastic problems abstract in this paper parallel computing is applied to the solution of elastoplastic problems with strain hardening after a brief discussion of the classical variational and finite element formulations of the plasticity problem an algorithm is proposed it is based on a variant of the johnson weak formulation and on the schwarz domain decomposition method the domain is triangulated and the subdomains are defined as the union of the elements having a node in common this leads to many small subproblems which can be solved in a simple and efficient manner the algorithm has been implemented on a parallel computer the numerical results obtained for two examples a sheared plate and a perforated plate in tension compare quite favorably with simulations using a classical finite element code the computing times obtained show that the proposed method utilizes the parallel structure of the computer very efficiently

critical behavior of the kinetic ising model on a fractal lattice the authors study the critical behaviour static and dynamic of the ising model defined on a fractal sierpinski carpet using monte carlo calculations estimates for various critical exponents are obtained from a finite size scaling analysis the results are compared with the available predictions for the dynamical critical exponent z they find the dynamic exponent z near 2 2 to be lower than predicted

on the critical dynamics of the diluted q state potts models the results of monte carlo simulations of the four state potts model on a square lattice at the bond percolation threshold are presented estimates are given for the new dynamical exponents a and b the result for a is in clear contradiction with a recent conjecture of nunes da silva and lage 1987

a generalization of the schwarz alternating method to an arbitrary number of subdomains we give a generalization of the schwarz alternating method to an arbitrary number of subdomains as applications we prove that the method converges for the main second order boundary value problems as well as for the system of linear elasticity for the dirichlet problems it is proved that the method converges geometrically and some numerical examples are given

dynamics of the potts model on a fractal lattice the dynamics of the q state potts model on a fractal lattice is studied using monte carlo simulations the glauber dynamics is used leading to an effective temperature dependent critical exponent of the form z ak b implying the breakdown of conventional dynamic scaling the value of a is shown to be independent of q within the error bars

bicritical scaling and dynamic crossover in the bond diluted glauber ising chain the author presents an investigation of the dynamic critical behaviour near the percolation bicritical point of the 1d bond diluted glauber ising model the expected bicritical dynamic scaling form is rigorously established for the decay functions describing the decay of the equilibrium wavevector dependent correlation function and the decay of the magnetisation from a non equilibrium wavevector dependent initial state the corresponding characteristic decay times are evaluated exactly and exhibit a cross over from pure to percolation dominated behaviour on increasing the dilution the results in the percolation regime are in agreement with recent calculations in which domain boundary diffusion methods are applied to a wider class of kinetic ising models

a tfeti domain decomposition solver for elastoplastic problems we propose an algorithm for the efficient parallel implementation of elastoplastic problems with hardening based on the so called tfeti total finite element tearing and interconnecting domain decomposition method we consider an associated elastoplastic model with the von mises plastic criterion and the linear isotropic hardening law such a model is discretized by the implicit euler method in time and the consequent one time step elastoplastic problem by the finite element method in space the latter results in a system of nonlinear equations with a strongly semismooth and strongly monotone operator the semismooth newton method is applied to solve this nonlinear system corresponding linearized problems arising in the newton iterations are solved in parallel by the above mentioned tfeti domain decomposition method the proposed tfeti based algorithm was implemented in matlab parallel environment and its performance was illustrated on a 3d elastoplastic benchmark numerical results for different time discretizations and mesh levels are presented and discussed and a local quadratic convergence of the semismooth newton method is observed

on the schwarz alternating method with more than two subdomains for nonlinear monotone problems in a hilbert space an iterative process is defined which generalizes the schwarz alternating method for nonlinear monotone problems to more than two subdomains and the convergence of this process is proved in the case of the problems with the solution in a convex of h 0 1 omega it is proved that the method converges geometrically numerical results are given concerning the problem of elastic plastic torsion of prismatic bars and the problem of seepage of fluids through porous media

novel domain growth law in random magnets abstract we investigate the kinetics of domain growth in ising magnets where a fraction 1 p of the magnetic atoms or ions spins are randomly substituted by non magnetic impurities we argue that close to the percolation threshold p c the statistical self similarity of the underlying structure gives rise to a novel crossover in the growth law we propose a method to detect any evidence of this new prediction from the kinetics of domain growth in the dilute ising model dim during intermediate time scales by carrying out monte carlo simulations not at p p c but at slightly higher spin concentrations we analyze the results of our extensive monte carlo simulation of the strongly diluted two dimensional ising model and find the growth to be consistent with the proposed scenario we also compare our observations with those in the recent experiments on the kinetics of ordering in rb 2 co p mg 1 p f 4

photon added barut girardello coherent states of the pseudoharmonic oscillator in a previous paper popov d 2001 j phys a math gen 34 5283 we have constructed the coherent states css of the pseudoharmonic oscillator pho these states are of the barut girardello type in the present paper we have constructed and investigated some properties of the photon added barut girardello coherent states pa bgcss of the pho these states are not orthogonal but are normalized and satisfy a unity resolution relation the completeness relation we have found the analytical form for the positive weight function in the resolution of unity by using these states we have calculated some expectation values the first two powers of the number operator n which have evinced some non classical properties in order to examine the statistical properties of a pho gas which obeys the quantum canonical distribution the diagonal p representation of the density operator m is constructed and the thermal expectation values are calculated all these quantities are expressed in terms of meijer g functions and so the pa bgcss are a new field of application for these functions also the time dependence of the pa bgcss is examined if in the obtained results we put m 0 we recover all the results from our previous paper