Navegação Ciências Exatas e da Terra por Autor "Theumann, Walter Karl"
Resultados 1-15 de 15
-
Categorization in fully connected multistate neural network models
Erichsen Junior, Rubem; Theumann, Walter Karl; Dominguez, David Renato Carreta (1999) [Artigo de periódico]The categorization ability of fully connected neural network models, with either discrete or continuous Q-state units, is studied in this work in replica symmetric mean-field theory. Hierarchically correlated multistate ... -
Categorization in the symmetrically dilute hopfield network
Krebs, Paulo Roberto; Theumann, Walter Karl (1999) [Artigo de periódico]A symmetrically dilute Hopfield model with a Hebbian learning rule is used to study the effects of gradual dilution and of synaptic noise on the categorization ability of an attractor neural network with hierarchically ... -
Crossover exponents for the potts model with quadratic symmetry breaking
Theumann, Walter Karl; Gusmao, Miguel Angelo Cavalheiro (1984) [Artigo de periódico]The effect of quadratic symmetry breaking (QSB) on two representations for the Potts vectors in a continuum-field model are studied to two-loop order in renormalized perturbation theory in d=6-E dimensions, in extension ... -
Effects of trilinear symmetry breaking on the Potts-model transition of uniaxially stressed SrTiO 3
Fontanari, Jose Fernando; Theumann, Walter Karl (1986) [Artigo de periódico]A Landau analysis shows that a break of trilinear symmetry in the continuous three-state Potts model with linear and quadratic symmetry breaking is re1evant for the trigonal-to-pseudotetragonal phase transition in uniaxially ... -
Inverse melting and inverse freezing in a three-state spin-glass model with finite connectivity
Erichsen Junior, Rubem; Theumann, Walter Karl; Magalhaes, Sergio Garcia (2013) [Artigo de periódico]The phase diagrams of the three-state Ghatak-Sherrington spin-glass (or random Blume-Capel) model are obtained in mean-field theory with replica symmetry in order to study the effects of a ferromagnetic bias and finite ... -
Mean field theory of the ising random-amisotropy-axis model in the large-component limit
Dominguez, David Renato Carreta; Theumann, Walter Karl (1993) [Artigo de periódico]The lsing random-anisotropy-axis model with additional noncubic anisotropy is investigated in mean-field theory in the limit p → ∞ for p-component random vectors on a lattice of N sites. The effects of anisotropy for ... -
Nonuniversality of ratios of critical and tricritical parameters in the three-state potts model with symmetry-breaking perturbations
Barbosa, Marcia Cristina Bernardes; Theumann, Walter Karl (1988) [Artigo de periódico]Fluctuation corrections to symmetry-breaking perturbations are shown to yield nonuniversal ratios for te lt, hc Ih, and Me IM, between the reduced temperature t, magnetic field h, and magnetization M of the underlying XY ... -
Optimally adapted multistate neural networks trained with noise
Erichsen Junior, Rubem; Theumann, Walter Karl (1999) [Artigo de periódico]The principle of adaptation in a noisy retrieval environment is extended here to a diluted attractor neural network of Q-state neurons trained with noisy data. The network is adapted to an appropriate noisy training overlap ... -
Pattern reconstruction and sequence processing in feed-forward layered neural networks near saturation
Metz, Fernando Lucas; Theumann, Walter Karl (2005) [Artigo de periódico]The dynamics and the stationary states for the competition between pattern reconstruction and asymmetric sequence processing are studied here in an exactly solvable feed-forward layered neural network model of binary units ... -
Period-two cycles in a feedforward layered neutral network model with symmetric sequence processing
Metz, Fernando Lucas; Theumann, Walter Karl (2007) [Artigo de periódico]The effects of dominant sequential interactions are investigated in an exactly solvable feedforward layered neural network model of binary units and patterns near saturation in which the interaction consists of a Hebbian ... -
Phase transitions in the three-state Ising spin-glass model with finite connectivity
Erichsen Junior, Rubem; Theumann, Walter Karl (2011) [Artigo de periódico]The statistical mechanics of a two-state Ising spin-glass model with finite random connectivity, in which each site is connected to a finite number of other sites, is extended in this work within the replica technique to ... -
Potts model in a random field
Fontanari, Jose Fernando; Theumann, Walter Karl; Dominguez, David Renato Carreta (1989) [Artigo de periódico]The q-state Potts model in a random field with a discrete distribution of statistically independent fields ordered along any of the q states is studied in mean-field theory. Detailed phase diagrams are obtained in a ... -
Renormalization and phase transitions in Potts [fi]/sup 3/-field theory with quadratic and trilinear symmetry breaking
Barbosa, Marcia Cristina Bernardes; Gusmao, Miguel Angelo Cavalheiro; Theumann, Walter Karl (1986) [Artigo de periódico]Renormalized perturbation theory with generalized minimal subtraction is used as an appropriate renormalization-group procedure for the study of crossover behavior in the continuum version of the p-state Potts model with ... -
Retrieval behavior and thermodynamic properties of symmetrically diluted Q-ising neural networks
Theumann, Walter Karl; Erichsen Junior, Rubem (2001) [Artigo de periódico]The retrieval behavior and thermodynamic properties of symmetrically diluted Q-Ising neural networks are derived and studied in replica-symmetric mean-field theory generalizing earlier works on either the fully connected ... -
Time evolution of the extremely diluted Blume-Emery-Griffiths neulal network
Bolle, Desire; Dominguez, David Renato Carreta; Erichsen Junior, Rubem; Korutcheva, Elka; Theumann, Walter Karl (2003) [Artigo de periódico]A study of the time evolution and a stability analysis of the phases in the extremely diluted Blume-Emery-Griffiths neural network model are shown to yield new phase diagrams in which fluctuation retrieval may drive pattern ...