30 research outputs found
Vortex nucleation as a case study of symmetry breaking in quantum systems
Mean-field methods are a very powerful tool for investigating weakly
interacting many-body systems in many branches of physics. In particular, they
describe with excellent accuracy trapped Bose-Einstein condensates. A generic,
but difficult question concerns the relation between the symmetry properties of
the true many-body state and its mean-field approximation. Here, we address
this question by considering, theoretically, vortex nucleation in a rotating
Bose-Einstein condensate. A slow sweep of the rotation frequency changes the
state of the system from being at rest to the one containing one vortex. Within
the mean-field framework, the jump in symmetry occurs through a turbulent phase
around a certain critical frequency. The exact many-body ground state at the
critical frequency exhibits strong correlations and entanglement. We believe
that this constitutes a paradigm example of symmetry breaking in - or change of
the order parameter of - quantum many-body systems in the course of adiabatic
evolution.Comment: Minor change
Corrida em piscina funda: limites e possibilidades para o alto desempenho Velocidad en piscina de profundidad: lĂmites y posibilidades para un alto desempeño Deep water running: limits and possibilities for high performance
O objetivo deste estudo foi analisar os limites e possibilidades da utilização da corrida em piscina funda no treinamento de corredores de rendimento. AlĂ©m disso, sĂŁo discutidas as respostas agudas submáximas, máximas e crĂ´nicas, do ponto de vista fisiolĂłgico e biomecânico entre a corrida em terra e em piscina funda. As respostas máximas de freqĂĽĂŞncia cardĂaca e consumo de oxigĂŞnio sĂŁo menores no exercĂcio aquático do que na corrida terrestre. Dados experimentais sugerem o uso do treinamento de corrida em piscina funda para corredores de rendimento; contudo, essas evidĂŞncias sĂŁo limitadas para treinamentos de atĂ© 10 semanas.<br>El objetivo de este estudio ha sido el de analizar los lĂmites y posibilidades de la utilizaciĂłn de carreras de velocidad en piscina de profundidad durante el entrenamiento de velocista de rendimiento. Además de esto, son discutidas las respuestas agudas submáximas, máximas y crĂłnicas, bajo el punto de vista fisiolĂłgico y biomecánico entre la carrera en tierra y en piscina profunda. Las respuestas máximas de frecuencia cardĂaca y consumo de oxĂgeno son menores en el ejercicio acuático que en la de tierra. Datos experimentales sugieren el uso de entrenamiento de carrera en piscina profunda para velocistas de rendimiento, sin embargo estas evidencias son limitadas a entrenamientos de hasta 10 semanas.<br>The purpose of this study was to analyze the limits and possibilities of deep water running on training of performance runners. Besides, it has been discussed the submaximal acute, maximal acute and chronical responses, following physiological and biomechanical aspects between running on land and deep water running. Heart rate and oxygen uptake's maximal responses are lower in aquatic exercise than in running on land. Experimental evidences suggest the deep water running training for performance athletes, but these studies are limited in training program until ten weeks