Phase Fluctuations in Bose-Einstein Condensates

We demonstrate the existence of phase fluctuations in elongated Bose-Einstein Condensates (BECs) and study the dependence of those fluctuations on the system parameters. A strong dependence on temperature, atom number, and trapping geometry is observed. Phase fluctuations directly affect the coherence properties of BECs. In particular, we observe instances where the phase coherence length is significantly smaller than the condensate size. Our method of detecting phase fluctuations is based on their transformation into density modulations after ballistic expansion. An analytic theory describing this transformation is developed.Comment: 11 pages, 7 figure

Localization and Anomalous Transport in a 1-D Soft Boson Optical Lattice

We study the dynamics of Bose-Einstein condensed atoms in a 1-D optical lattice potential in a regime where the collective (Josephson) tunneling energy is comparable with the on-site interaction energy, and the number of particles per lattice site is mesoscopically large. By directly imaging the motion of atoms in the lattice, we observe an abrupt suppression of atom transport through the array for a critical ratio of these energies, consistent with quantum fluctuation induced localization. Directly below the onset of localization, the frequency of the observed superfluid transport can be explained by a phonon excitation but deviates substantially from that predicted by the hydrodynamic/Gross-Pitaevskii equations.Comment: 14 pages, 5 figure

Dynamics of apparent horizons in quantum gravitational collapse

We study the gravitational collapse of a massless scalar field within the effective scenario of loop quantum gravity. Classical singularity is avoided and replaced by a quantum bounce in this model. It is shown that, quantum gravity effects predict a threshold scale below which no horizon can form as the collapse evolves towards the bounce.Comment: Contribution to the Spanish Relativity Meeting in Portugal 2012 (ERE2012), Guimaraes, Portuga

Behavioral and hormonal changes following social instability in young rhesus macaques (Macaca mulatta)

This is an accepted manuscript of an article published by American Psychological Association in Journal of Comparative Psychology, available online at: https://doi.org/10.1037/com0000297 This article may not exactly replicate the authoritative document published in the APA journal. It is not the copy of recordSocial instability (SI) occurs when there is competition over social status. Reduced certainty of social status can lead to heightened aggression, which can increase physiological stress responses, as individuals prepare to fight for their social status. However, adults can take proactive coping mechanisms to reduce the physiological stress induced by SI, such as increasing affiliation. Very little is known, however, about the behavioral and hormonal effects of SI early in development. Filling these gaps in knowledge would add to the fields of primatology and developmental and comparative psychology. We conducted an opportunistic study of a peer group of 18 rhesus macaque (Macaca mulatta) yearlings before and during SI. We used social network analysis to measure individuals’ dominance certainty (DC, in their aggressive and submissive network) and their position in affiliative networks (grooming and play) and analyzed hair cortisol concentrations (HCCs). As predicted, during SI, we observed a decrease in DC, indicating that individuals had less stable dominance positions. As well, during SI, we observed increased rates of social grooming and decreased rates of social play, reflecting potential coping mechanisms. More socially connected individuals in social grooming and social play networks received higher levels of coalitionary support. Contrary to predictions, DC did not predict HCCs; rather individuals that were more connected in the social play network exhibited smaller increases in HCCs during SI, revealing a potential buffering effect of social play. Our results underscore the need for further research on the effects of SI during ontogeny.Division of Intramural Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Interference of a Tonks-Girardeau Gas on a Ring

We study the quantum dynamics of a one-dimensional gas of impenetrable bosons on a ring, and investigate the interference that results when an initially trapped gas localized on one side of the ring is released, split via an optical-dipole grating, and recombined on the other side of the ring. Large visibility interference fringes arise when the wavevector of the optical dipole grating is larger than the effective Fermi wavevector of the initial gas.Comment: 7 pages, 3 figure

The Lieb-Liniger Model as a Limit of Dilute Bosons in Three Dimensions

We show that the Lieb-Liniger model for one-dimensional bosons with repulsive $\delta$-function interaction can be rigorously derived via a scaling limit from a dilute three-dimensional Bose gas with arbitrary repulsive interaction potential of finite scattering length. For this purpose, we prove bounds on both the eigenvalues and corresponding eigenfunctions of three-dimensional bosons in strongly elongated traps and relate them to the corresponding quantities in the Lieb-Liniger model. In particular, if both the scattering length $a$ and the radius $r$ of the cylindrical trap go to zero, the Lieb-Liniger model with coupling constant $g \sim a/r^2$ is derived. Our bounds are uniform in $g$ in the whole parameter range $0\leq g\leq \infty$, and apply to the Hamiltonian for three-dimensional bosons in a spectral window of size $\sim r^{-2}$ above the ground state energy.Comment: LaTeX2e, 19 page

Dominance rank predicts social network position across developmental stages in rhesus monkeys

Social network analysis is increasingly common in studying the complex interactions among individuals. Across a range of primates, high-ranking adults are generally more socially connected, which results in better fitness outcomes. However, it still remains unclear whether this relationship between social network position and dominance rank emergences in infancy and whether, in species with a social transmission of dominance rank, social network positions are driven by the presence of the mother. To fill this gap, we first explored whether dominance ranks were related to social network position, measured via eigenvector centrality, in infants, juveniles, and adults in a troop of semi-free ranging rhesus macaques (Macaca mulatta). We then examined relationships between dominance rank and eigenvector centrality in a peer-only group of yearlings who were reared with their mothers in either a rich, socially complex environment of multigenerational (MG) kin support or a unigenerational (UG) group of mothers and their infants from birth through eight months. In experiment 1, we found that mother’s network position predicted offspring network position, and that dominants across all age categories were more central in affiliative networks (social contact, social grooming, and social play). Experiment 2 showed that high-ranking yearlings in a peer-only group were more central only in the social contact network. Moreover, yearlings reared in a socially complex environment of MG kin support were more central. Our findings suggest that the relationship between dominance rank and social network position begins early in life, and that complex early social environments can promote later social competency. Our data add to the growing body of evidence that the presence/absence of the mother and kin influence how dominance rank affects social network position. These findings have important implications for the role of caregivers in the social status of developing primates, which ultimately ties to health and fitness outcomes

Trans-Dimensional Geoacoustic Inversion of Wind-Driven Ambient Noise

This letter applies trans-dimensional Bayesian geoacoustic inversion to quantify the uncertainty due to model selection when inverting bottom-loss data derived from wind-driven ambient-noise measurements. A partition model is used to represent the seabed, in which the number of layers, their thicknesses, and acoustic parameters are unknowns to be determined from the data. Exploration of the parameter space is implemented using the Metropolis–Hastings algorithm with parallel tempering, whereas jumps between parameterizations are controlled by a reversible-jump Markov chain Monte Carlo algorithm. Sediment uncertainty profiles from inversion of simulated and experimental data are presented

Ramos do Cooperativismo: cenário da região centro oeste do Brasil.

O cooperativismo é um modelo econômico com características próprias, baseado em princípios definidos pela Aliança Cooperativa Internacional - ACI. Está presente no Brasil desde o final do século XIX, contemplando hoje seus diferentes ramos, e em todos os Estados brasileiros e Distrito Federal. Na região centro oeste do país, temos hoje 575 cooperativas ativas, sendo 178 do ramo agropecuário, em Mato Grosso do Sul das 71 cooperativas, 26 são deste ramo. O desenvolvimento de forma sustentável é um desafio para as instituições e governos, assim, devido a sua natureza, o cooperativismo pode ser uma alternativa de promover o crescimento da economia, o desenvolvimento local de maneira sustentável? O que percebemos é que o crescente número de negócios de natureza cooperativa que vêm se firmando no país pode ser um sinal de que o caminho para alcançar tal desenvolvimento foi encontrado, uma vez que a maior parte das cooperativas do país já existem a mais de 20 anos, algumas mais de 40 demonstrando a solidez e sustentabilidade do negócio. Também evidenciando que ainda há espaço para crescimento.Anais do VI EIGEDIN