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1
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Thermodynamics of Ising Ferromagnet Studied by the Real-Space Renormalization Group Method

100%
Reich W., Piotrkowska K., Esposito U., Caramico D'Auria A.
Acta Physica Polonica A
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1993
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vol. 84
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issue 2
275-278
EN
The critical exponents of the 3D Ising model were calculated in the approximation of the fourth-order cumulant expansion. Thermodynamic functions in the high-temperature range are obtained.
2
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SU(2) Coherent State Path Integral Investigation of the Holstein Dimer

80%
Hakioğlu T., Ivanov V., Zhuravlev M.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
927-930
EN
The SU(2) coherent state path integral is used to investigate the partition function of the Holstein dimer. This approach naturally takes into account the dynamical symmetry of the model. The ground-state energy and the number of the phonons are calculated as functions of the parameters of the Hamiltonian. The renormalizations of the phonon frequency and electron hopping for bonding and antibonding states are considered. The destruction of quasiclassical mean field solution is discussed.
3
Content available remote

Numerical Test of Molecular-Field Renormalization Group

80%
Kamieniarz G.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
423-426
EN
A new transfer matrix approach has been worked out to test the predictions of the molecular-field renormalization group for square Ising clusters with a linear size up to L ≤ 11. The convergence of the finite-size critical couplings towards the exact value for the molecular-field renormalization group is shown and the limit of the ratio y_{h}/y_{t} consistent with the corresponding universal value is revealed.
4
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Improved Phase Diagrams of Ashkin-Teller Model

80%
Pawlicki P., Kamieniarz G., Kozlowski P., Dekeyser R., Rogiers J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
453-458
EN
The phase diagram of the Askhin-Teller model in two dimensions is determined. Numerical calculations are performed for the simple square L × L lattice using transfer matrix technique. Exploiting finite-size scaling all unknown critical lines were obtained with good accuracy. An extended version of the Ashkin-Teller model is also considered within the molecular field renormalization group method and the critical surface for three-parameter odd-parity Hamiltonian is calculated.
5
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Simulations of the 3D Ising Model at Criticality

70%
Blöte H., Kamieniarz G.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
395-398
EN
We present some new finite-size results for the Binder cumulant that we obtained by means of a transfer-matrix perturbation expansion and by the cluster Monte Carlo methods - the Swendsen-Wang and Wolff algorithms and the largest-cluster method. A finite-size scaling analysis taking into account a correction to scaling locates the critical coupling at Kc = 0.221649(4).
6
Content available remote

Critical Behaviour of Some 2D Lattice Models

61%
Kamieniarz G., Blöte H., Dekeyser R.
Acta Physica Polonica A
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1994
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vol. 85
|
issue 2
389-393
EN
The density series of the non-interacting hard-square lattice gas model are reanalyzed by the ratio, Dlog Padé and differential approximant methods. The problem of poor consistency between series and other results is resolved. Transfer matrix calculations are performed, implementing both finite-size scaling and conformal invariance. Very accurate estimates of the critical exponents y_{t}, and y_{h} are obtained in agreement with Ising universality. Furthermore, an improvement of the value of the critical density ρ_{c} is found. In addition, the universal critical-point ratios of the square of the second and the fourth moment of the magnetization for ferromagnetic Ising models on the square and on the triangular lattice with periodic boundary conditions are reported.
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