A. Malaspinas - Academia.edu (original) (raw)

Papers by A. Malaspinas

Research paper thumbnail of Fokker-Planck adescription of a Navier-Stokes fluid with instability

Lecture Notes in Physics, 1978

Without Abstract

Research paper thumbnail of Finite size scaling approach to surface critical phenomena

Journal of Physics C: Solid State Physics, 1985

An extended finite-size scaling approach which allows the authors to treat simultaneously both bu... more An extended finite-size scaling approach which allows the authors to treat simultaneously both bulk and surface properties is presented. The method is tested on the two-dimensional Ising model. The bulk and surface magnetic exponents, are also estimated for the two-dimensional q-states Potts model, with q=3 and 4. For q=3, the value obtained for the surface magnetic exponent supports a recent

Research paper thumbnail of Migdal renormalisation-group transformation for the kinetic Ising model in arbitrary dimensions

Journal of Physics C: Solid State Physics, 1980

The critical behaviour of the kinetic Ising model is analysed in the framework of the Migdal dyna... more The critical behaviour of the kinetic Ising model is analysed in the framework of the Migdal dynamic renormalisation group, for arbitrary dimensions. The dynamic exponent z, correlation length exponent nu and critical fixed point K* are computed for d=1 to 6, in the Suzuki approximation. By analytic continuation, the case d=1+ epsilon is considered within this approximation. It is shown that already to leading order in epsilon , the predictions for K*, nu and z given by dynamics differ from those given by statics. Accordingly, the two-dimensional case is revisited by taking into account higher-order correlation functions. This modification of the renormalisation-group transformation improves significantly the preceding results.

Research paper thumbnail of The one-hypercube renormalisation group transformation for the planar rotator model

Journal of Physics C: Solid State Physics, 1978

The critical behaviour of the planar rotator model on a square lattice is investigated using the ... more The critical behaviour of the planar rotator model on a square lattice is investigated using the one-hypercube approximate renormalisation group transformation. An isolated critical fixed point emerges from this approximation. Critical exponents are calculated by standard methods. A lower bound on the free energy is obtained by integration on the flow in the space of the coupling constants.

Research paper thumbnail of Computation of structure factors by finite-size scaling and transfer matrix methods

Journal of Physics C: Solid State Physics, 1983

Presents a method to calculate the static structure factor of low-dimensional systems. The method... more Presents a method to calculate the static structure factor of low-dimensional systems. The method consists of a combination of the finite-size scaling theory and transfer matrix techniques. Its applicability is checked against the two-dimensional Ising ferromagnet with encouraging results.

Research paper thumbnail of Free energy of a long-range gauge theory on a triangular lattice

Physics Letters A, 1981

We discuss some properties of a model approximating a spin glass on a triangular lattice in two d... more We discuss some properties of a model approximating a spin glass on a triangular lattice in two dimensions and present an exact calculation of the free energy of the corresponding "gauge field" model in the long-range interaction limit. The results are compared to a mean field approximation.

Research paper thumbnail of On the critical dynamics of one-dimensional Ising models

Physics Letters A, 1986

The critical dynamics of an Ising ferromagnetic chain with two different coupling constants (J1&g... more The critical dynamics of an Ising ferromagnetic chain with two different coupling constants (J1>J2) is studied. The dynamical critical exponent z is found to be nonuniversal. For Glauber dynamics one finds z = 1+J1/J2, while for Kawasaki dynamics z = 3+2J1/J2. The case of a disordered chain is also briefly discussed.

Research paper thumbnail of Calculation of structure factors for a simple model of adsorption on a surface by real-space renormalization-group method

Physics Letters A, 1983

The structure factor S(q) of a simple model describing adsorption on a two-dimensional surface is... more The structure factor S(q) of a simple model describing adsorption on a two-dimensional surface is computed by real-space renormalization-group technique for T >= Tc. The method used is based on first-order cumulant expansion implemented with an ad hoc recursion relation for the coupling constants. The model is equivalent to an antiferromagnetic Ising model in an external field.

Research paper thumbnail of On the critical dynamics of one-dimensional disordered Ising models

Journal of Physics A-mathematical and General, 1987

The critical dynamics of a disordered Ising ferromagnetic chain with two coupling constants (J1&g... more The critical dynamics of a disordered Ising ferromagnetic chain with two coupling constants (J1>or=J2>0) is studied for Glauber dynamics. Using a domain wall argument the dynamical critical exponent z is found to be non-universal but independent of the disorder, namely z=1+J1/J2. The problem is formulated in terms of diffusion in a random medium. The diffusion is shown to be normal.

Research paper thumbnail of On the critical dynamics of one-dimensional Potts models

Journal of Physics A: Mathematical and General, 1986

Simple physical arguments about the movement of domain walls are used to determine the dependence... more Simple physical arguments about the movement of domain walls are used to determine the dependence of the dynamical critical exponent z on the transition rates for the one-dimensional q-state Potts model.

Research paper thumbnail of Physics in Living Matter

Research paper thumbnail of Fokker-Planck adescription of a Navier-Stokes fluid with instability

Lecture Notes in Physics, 1978

Without Abstract

Research paper thumbnail of Finite size scaling approach to surface critical phenomena

Journal of Physics C: Solid State Physics, 1985

An extended finite-size scaling approach which allows the authors to treat simultaneously both bu... more An extended finite-size scaling approach which allows the authors to treat simultaneously both bulk and surface properties is presented. The method is tested on the two-dimensional Ising model. The bulk and surface magnetic exponents, are also estimated for the two-dimensional q-states Potts model, with q=3 and 4. For q=3, the value obtained for the surface magnetic exponent supports a recent

Research paper thumbnail of Migdal renormalisation-group transformation for the kinetic Ising model in arbitrary dimensions

Journal of Physics C: Solid State Physics, 1980

The critical behaviour of the kinetic Ising model is analysed in the framework of the Migdal dyna... more The critical behaviour of the kinetic Ising model is analysed in the framework of the Migdal dynamic renormalisation group, for arbitrary dimensions. The dynamic exponent z, correlation length exponent nu and critical fixed point K* are computed for d=1 to 6, in the Suzuki approximation. By analytic continuation, the case d=1+ epsilon is considered within this approximation. It is shown that already to leading order in epsilon , the predictions for K*, nu and z given by dynamics differ from those given by statics. Accordingly, the two-dimensional case is revisited by taking into account higher-order correlation functions. This modification of the renormalisation-group transformation improves significantly the preceding results.

Research paper thumbnail of The one-hypercube renormalisation group transformation for the planar rotator model

Journal of Physics C: Solid State Physics, 1978

The critical behaviour of the planar rotator model on a square lattice is investigated using the ... more The critical behaviour of the planar rotator model on a square lattice is investigated using the one-hypercube approximate renormalisation group transformation. An isolated critical fixed point emerges from this approximation. Critical exponents are calculated by standard methods. A lower bound on the free energy is obtained by integration on the flow in the space of the coupling constants.

Research paper thumbnail of Computation of structure factors by finite-size scaling and transfer matrix methods

Journal of Physics C: Solid State Physics, 1983

Presents a method to calculate the static structure factor of low-dimensional systems. The method... more Presents a method to calculate the static structure factor of low-dimensional systems. The method consists of a combination of the finite-size scaling theory and transfer matrix techniques. Its applicability is checked against the two-dimensional Ising ferromagnet with encouraging results.

Research paper thumbnail of Free energy of a long-range gauge theory on a triangular lattice

Physics Letters A, 1981

We discuss some properties of a model approximating a spin glass on a triangular lattice in two d... more We discuss some properties of a model approximating a spin glass on a triangular lattice in two dimensions and present an exact calculation of the free energy of the corresponding "gauge field" model in the long-range interaction limit. The results are compared to a mean field approximation.

Research paper thumbnail of On the critical dynamics of one-dimensional Ising models

Physics Letters A, 1986

The critical dynamics of an Ising ferromagnetic chain with two different coupling constants (J1&g... more The critical dynamics of an Ising ferromagnetic chain with two different coupling constants (J1>J2) is studied. The dynamical critical exponent z is found to be nonuniversal. For Glauber dynamics one finds z = 1+J1/J2, while for Kawasaki dynamics z = 3+2J1/J2. The case of a disordered chain is also briefly discussed.

Research paper thumbnail of Calculation of structure factors for a simple model of adsorption on a surface by real-space renormalization-group method

Physics Letters A, 1983

The structure factor S(q) of a simple model describing adsorption on a two-dimensional surface is... more The structure factor S(q) of a simple model describing adsorption on a two-dimensional surface is computed by real-space renormalization-group technique for T >= Tc. The method used is based on first-order cumulant expansion implemented with an ad hoc recursion relation for the coupling constants. The model is equivalent to an antiferromagnetic Ising model in an external field.

Research paper thumbnail of On the critical dynamics of one-dimensional disordered Ising models

Journal of Physics A-mathematical and General, 1987

The critical dynamics of a disordered Ising ferromagnetic chain with two coupling constants (J1&g... more The critical dynamics of a disordered Ising ferromagnetic chain with two coupling constants (J1>or=J2>0) is studied for Glauber dynamics. Using a domain wall argument the dynamical critical exponent z is found to be non-universal but independent of the disorder, namely z=1+J1/J2. The problem is formulated in terms of diffusion in a random medium. The diffusion is shown to be normal.

Research paper thumbnail of On the critical dynamics of one-dimensional Potts models

Journal of Physics A: Mathematical and General, 1986

Simple physical arguments about the movement of domain walls are used to determine the dependence... more Simple physical arguments about the movement of domain walls are used to determine the dependence of the dynamical critical exponent z on the transition rates for the one-dimensional q-state Potts model.

Research paper thumbnail of Physics in Living Matter