Evidence for Efimov quantum states in an ultracold gas of cesium atoms

Systems of three interacting particles are notorious for their complex physical behavior. A landmark theoretical result in few-body quantum physics is Efimov's prediction of a universal set of bound trimer states appearing for three identical bosons with a resonant two-body interaction. Counterintuitively, these states even exist in the absence of a corresponding two-body bound state. Since the formulation of Efimov's problem in the context of nuclear physics 35 years ago, it has attracted great interest in many areas of physics. However, the observation of Efimov quantum states has remained an elusive goal. Here we report the observation of an Efimov resonance in an ultracold gas of cesium atoms. The resonance occurs in the range of large negative two-body scattering lengths, arising from the coupling of three free atoms to an Efimov trimer. Experimentally, we observe its signature as a giant three-body recombination loss when the strength of the two-body interaction is varied. We also detect a minimum in the recombination loss for positive scattering lengths, indicating destructive interference of decay pathways. Our results confirm central theoretical predictions of Efimov physics and represent a starting point with which to explore the universal properties of resonantly interacting few-body systems. While Feshbach resonances have provided the key to control quantum-mechanical interactions on the two-body level, Efimov resonances connect ultracold matter to the world of few-body quantum phenomena.Comment: 18 pages, 3 figure

Use of a mathematical model to estimate the impact of shrimp pen culture at Patos Lagoon estuary, Brazil

Ecological modeling has been used as a tool to estimate potential impacts caused by aquaculture to the surrounding environment. In this work, a mathematical model was applied to estimate the maximum amount of pink shrimp (Farfantepenaeus paulensis) culture units (3,100m2 pen enclosures) that could be installed at two shallow estuarine bays of Patos Lagoon (known as Coreia and Porto do Rei) with no significant effects on either water quality or viability of the culture system. To calibrate the model, information about the culture of Litopenaeus vannamei and F. paulensis as well as field data (influence of netting material, water current speed and nitrogen concentrations) were used. Under a bad scenario (water current velocity of 0.01m s–1 and a mesh clogging effect of 40%), it would be possible to install up to 29 pens at the Coreia bay, and 39 pens at the Porto do Rei bay. Results indicate that the model was useful in determining the maximum number of culture units that could be installed at these bays, and thus have the potential to become an important tool in the definition of environmental management strategies in relation to aquaculture development.Modelos ecológicos têm sido utilizados como ferramenta para avaliar potenciais impactos ambientais causados pela aquicultura. Neste trabalho, foi aplicado um modelo matemático para estimar a quantidade máxima de unidades de produção (cercados com 3.100 m2) do camarão-rosa Farfantepenaeus paulensis que podem ser instalados em duas baías rasas no estuário da Lagoa dos Patos (conhecidas como Coreia e Porto do Rei), sem efeitos significativos sobre a qualidade da água e viabilidade do sistema de engorda. Para calibrar o modelo, informações sobre a criação de Litopenaeus vannamei e F. paulensis, bem como dados de campo (influência de material de pano, a velocidade da corrente da água e concentração de nitrogênio) foram utilizados. Considerando um cenário ruim, velocidade da corrente da água de 0,01 m s–1 e um efeito de colmatação da malha de 40%, seria possível instalar no máximo 29 cercados na baía Coreia e 39 na baia Porto do Rei. Os resultados indicam que o modelo foi útil para determinar o número máximo de unidades de produção que podem ser instalados nestes compartimentos e, portanto, tem o potencial para se tornar uma ferramenta importante na definição de estratégias de gestão ambiental, em relação ao desenvolvimento da aquicultura