Tau-functions and dressing transformations for zero-curvature affine integrable equations

The solutions of a large class of hierarchies of zero-curvature equations that includes Toda- and KdV-type hierarchies are investigated. All these hierarchies are constructed from affine (twisted or untwisted) Kac-Moody algebras g. Their common feature is that they have some special vacuum solutions corresponding to Lax operators lying in some Abelian (up to the central term) subalgebra of g; in some interesting cases such subalgebras are of the Heisenberg type. Using the dressing transformation method, the solutions in the orbit of those vacuum solutions are constructed in a uniform way. Then, the generalized tau-functions for those hierarchies are defined as an alternative set of variables corresponding to certain matrix elements evaluated in the integrable highest-weight representations of g. Such definition of tau-functions applies for any level of the representation, and it is independent of its realization (vertex operator or not). The particular important cases of generalized mKdV and KdV hierarchies as well as the Abelian and non-Abelian affine Toda theories are discussed in detail. © 1997 American Institute of Physics.

Simulação numérica de trocadores de calor multitubulares equipados com fitas helicoidais externamente aos tubos

Classical shell-and-tube heat exchangers are usually equipped with segmental baffles. These baffles serve two basic functions: (a) they provide tube supports, thereby preventing or reducing mechanical problems, such as sagging or vibration; (b) they direct the fluid flow over the tubes so as to introduce a cross-flow component, thereby increasing the heat transfer. Segmented baffles have several sources of performance loss, some due to various leakage flows and others caused by stagnation zones. A new concept of longitudinal flow heat exchanger - based on placing twisted tapes along the tube bundle subchannels - was developed to mitigate drawbacks of other types of tubular heat exchangers. In this paper, a numerical model has been implemented in order to simulate the thermal-hydraulic feature of tubular heat exchangers equipped either with segmental baffles or with subchannel twisted tapes. The tube bundle has been described by means of an equivalent porous medium type model, allowing a macroscopic description of the shell-side flow. The basic equations - continuity, momentum and energy - have been solved by using the finite volume method. Typical numerical results have been compared with experimental data, reaching a very good agreement. A comparative analysis of different types of heat exchangers has been carried out, revealing the satisfactory thermal-hydraulic efficiency level of the twisted tapes heat exchangers.

Supersymmetry and the KdV equations for integrable hierarchies with a half-integer gradation

Supersymmetry is formulated for integrable models based on the sl(2 1) loop algebra endowed with a principal gradation. The symmetry transformations which have half-integer grades generate supersymmetry. The sl(2 1) loop algebra leads to N=2 supersymmetric mKdV and sinh-Gordon equations. The corresponding N=1 mKdV and sinh-Gordon equations are obtained via reduction induced by twisted automorphism. Our method allows for a description of a non-local symmetry structure of supersymmetric integrable models. © 2003 Elsevier B.V. All rights reserved.

Pure spinor formalism as an N ≤ 2 topological string

Following suggestions of Nekrasov and Siegel, a non-minimal set of fields are added to the pure spinor formalism for the superstring. Twisted ĉ ≤ 3 N ≤ 2 generators are then constructed where the pure spinor BRST operator is the fermionic spin-one generator, and the formalism is interpreted as a critical topological string. Three applications of this topological string theory include the super-Poincaré covariant computation of multiloop superstring amplitudes without picture-changing operators, the construction of a cubic open superstring field theory without contact-term problems, and a new four-dimensional version of the pure spinor formalism which computes F-terms in the spacetime action. © SISSA 2005.

Dynamical twisting and the b ghost in the pure spinor formalism

After adding an RNS-like fermionic vector ψ m to the pure spinor formalism, the non-minimal b ghost takes a simple form similar to the pure spinor BRST operator. The N=2 superconformal field theory generated by the b ghost and the BRST current can be interpreted as a dynamical twisting of the RNS formalism where the choice of which spin 1/2 ψ m variables are twisted into spin 0 and spin 1 variables is determined by the pure spinor variables that parameterize the coset SO(10)/U(5). © 2013 SISSA, Trieste, Italy.

Crioconservação de embriões de peixes neotropicais

Pós-graduação em Biologia Animal - IBILCE

Corpo, escola e processos de subjetivação: a educação física no programa São Paulo faz escola

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência dos estados emocionais em jogadoras de handebol

Questions of psychological interference have been white of the researchers, that identify in the emotional states, a key precious and important in the fight to get a significant result in the esportivo context. The present study it raised questions of interest of sciences of the sport, objectifying to check the influences of the emotional states of players of handebol and its possible interferences in the esportivo income. We work with a qualitative research, leading given next to the athletes and commission technique of the team of handebol of Sorocaba; using questionnaires structuralized and halfstructuralized for the collection of data. All the gotten results had been represented graphically and analyzed front to the theoretical referencial of the area. These results in had shown them that inside of the searched universe, consequentemente exist some factors that intervene with the esportivo income of the majority of the athletes , affecting in a generalized manner the income of the team. In this way we have that it is not only enough to give attention to the physical training, technician and tacticians. It is necessary to give a special attention to the psychological factors of the athletes, so that in a competition they can relieve everything that that has condition to relieve. Finally, we more suggest deepened research inside of this area so that let us can better understand and take attitudes with regard to subjects as the Daily paymenstrual Tension and the question of the leadership, in the form of case studies. We also suggest an intervention of work of a psychologist of the sport acting next to team since the phase of definition of objectives until the ends of the championship.

Influence of the rotary and/or oscillatory reciprocating systems in the morphological changes of narrow and curved molar root canals anatomy

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Algebraic constructions of densest lattices

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Um método para avaliação de desempenho de transmissão em cabos LAN

Pós-graduação em Engenharia Elétrica - FEB