Spin Models
Mostrando 13-24 de 80 artigos, teses e dissertações.
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13. Tsallis scaling in the long-range Ising chain with competitive interactions
A numerically efficient transfer matrix approach is used to investigate the validity of the Tsallis scaling hypothesis in the long-range Ising spin chain with competitive interactions. In this model, the interaction between two spins i and j placed r lattice steps apart is Ji, j = (-1)ζ(i,j)J0/rα, where ζ(i, j) is either 0 or 1. This procedure has succeed
Brazilian Journal of Physics. Publicado em: 2009-08
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14. Sinais de produção de novos bósons vetoriais no LHC / Signals of production of new vector bosons at the LHC
In this work we performed a phenomenological observation of new spin-1 bosons associated with the Electroweak Symmetry Breaking sector. As motivation for this analysis we previously studied the special case of models based on the mechanism of Eletroweak Symmetry Breaking via Boundary Conditions, which also have a tower vector of Kaluza-Klein bosons ensuring
Publicado em: 2009
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15. Integrable inhomogeneous spin chains in generalized Lunin-Maldacena backgrounds
We obtain through a Matrix Product Ansatz the exact solution of the most general inhomogeneous spin chain with nearest neighbor interaction and with U(1)² and U(1)³ symmetries. These models are related to the one loop mixing matrix of the Leigh-Strassler deformed N = 4 SYM theory, dual to type IIB string theory in the generalized Lunin-Maldacena background
Brazilian Journal of Physics. Publicado em: 2008-09
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16. The Matrix Product Ansatz for integrable U(1)N models in Lunin-Maldacena backgrounds
We obtain through a Matrix Product Ansatz (MPA) the exact solution of the most general N-state spin chain with U(1)N symmetry and nearest neighbour interaction. In the case N = 6 this model contain as a special case the integrable SO(6) spin chain related to the one loop mixing matrix for anomalous dimensions in N = 4 SYM, dual to type IIB string theory in t
Brazilian Journal of Physics. Publicado em: 2008-06
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17. The spin-1/2 ising model with skew magnetic field at high temperatures
We calculate the thermodynamics of the one-dimensional spin-1/2 Ising model in the presence of a constant skew magnetic field. We obtain the high-temperature expansion of its Helmholtz free energy (HFE), for the ferromagnetic and antiferromagnetic cases, up to order beta7. This expansion permits us to obtain the behaviour of the model for $ |J| \beta \stackr
Brazilian Journal of Physics. Publicado em: 2008-03
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18. Simulation of geomagnetic reversals through magnetic critical models
We use numerical simulations of a well-known phase-transition model to study reversals of the geomagnetic field. Each ring current in the geodynamo was supposed to behave as a magnetic spin while the magnetization of the model was supposed to be proportional to the Earth's magnetic dipole. We have performed a size-dependence study of the calculated quantitie
Brazilian Journal of Physics. Publicado em: 2008-03
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19. Uncovering the secrets of unusual phase diagrams: applications of two-dimensional Wang-Landau sampling
We use a two-dimensional Wang-Landau sampling algorithm to calculate the density of states for two discrete spin models and then extract their phase diagrams. The first system is an asymmetric Ising model on a triangular lattice with two- and three-body interactions in an external field. An accurate density of states allows us to locate the critical endpoint
Brazilian Journal of Physics. Publicado em: 2008-03
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20. Symmetry breaking and quantum phase transition in spin-boson models / Quebra de simetria e transição de fase quantica em alguns modelos de acoplamento spin-boson
Neste trabalho estudamos o efeito sobre a Transição de Fase Quântica (TFQ) do Modelo de Dicke Integrável devido a adição de um pequeno termo (fixo) de interação de dois bósons na Aproximação de Onda Girante (RWA). Mostramos que, embora a descontinuidade na derivada da energia do Estado Fundamental (EF) como função do parâmetro principal de inte
Publicado em: 2008
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21. Estudos do transporte de partÃculas brownianas interagentes e de transiÃÃes de fases em modelos de spin quÃnticos
Nesta Tese, sÃo investigados dois temas de interesse atual, o transporte de partÃculas brownianas interagentes e as transiÃÃes de fase em sistemas magnÃticos quÃnticos. No primeiro, o transporte de partÃculas brownianas interagentes sujeitas a um potencial de substrato do tipo catraca foi investigado numericamente atravÃs da dinÃmica de Langevin. Me
Publicado em: 2008
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22. Desenvolvimento de processos de deposição de filmes filmes sobre substratos polimericos fotopolimerizdos / Development of process of deposition of thin films on photopolymerization polymeric substrats
A new era has begun all around the world. The quality of life and health depends more and more on the human capacity of resolving problems that are becoming longer and more complex day by day. As communication and globalization advance, time becomes scarcer and more precious. The semiconductor materials which are used to activate the logical functions, the h
Publicado em: 2007
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23. EPR and semi-empirical studies as tools to assign the geometric structures of FeIII isomer models for transferrins
A reação entre Fe(ClO4)3.nH2O e N,N'-bis[(2-hidroxibenzil)-N,N' -bis(1-metilimidazol-2-il-metil)]etilenodiamina (H2bbimen) resulta na formação de dois isômeros geométricos, A e B, do cátion complexo [Fe(bbimen)]+, os quais foram isolados e caracterizados por espectroscopia na região do infravermelho e UV-visível, espectrometria de massas, medidas de
Journal of the Brazilian Chemical Society. Publicado em: 2006-12
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24. Numerical simulation of N-vector spin models in a magnetic field
Three-dimensional N-vector spin models may define universality classes for such diverse phenomena as i) the superfluid transition in liquid helium (currently investigated in the micro-gravity environment of the Space Shuttle) and ii) the transition from hadronic matter to a quark-gluon plasma, studied in heavy-ion collisions at the laboratories of Brookhaven
Brazilian Journal of Physics. Publicado em: 2006-09