5,018 research outputs found
Symmetry Breaking in d-Dimensional Self-gravitating Systems
Systems with long-range interactions, such as self-gravitating clusters and
magnetically confined plasmas, do not relax to the usual Boltzmann-Gibbs
thermodynamic equilibrium, but become trapped in quasi-stationary states (QSS)
the life time of which diverges with the number of particles. The QSS are
characterized by the lack of ergodicity which can result in a symmetry broken
QSS starting from a spherically symmetric particle distribution. We will
present a theory which allows us to quantitatively predict the instability
threshold for spontaneous symmetry breaking for a class of d-dimensional
self-gravitating systems.Comment: 5 pages, 4 figures. Accepted for publication in Physical Review
Letter
Non equilibrium phase transition with gravitational-like interaction in a cloud of cold atoms
We propose to use a cloud of laser cooled atoms in a quasi two dimensional
trap to investigate a non equilibrium collapse phase transition in presence of
gravitational-like interaction. Using theoretical arguments and numerical
simulations, we show that, like in two dimensional gravity, a transition to a
collapsed state occurs below a critical temperature. In addition and as a
signature of the non equilibrium nature of the system, persistent particles
currents, dramatically increasing close to the phase transition, are observed.Comment: 5 pages, 4 figure
Chile 1991: o Punk da transição e a alegria que não veio
Trabalho realizado sob orientação do professor Clécio
Ferreira Mendes, como requisito para a obtenção do
diploma de licenciado em História pela Universidade
Federal da Integração Latino Americana.Objetivo deste artigo é analisar o discurso do movimento punk chileno no período da
transição da ditadura à democracia através do disco ¿Democracia?, da banda Los Miserables, de
1991. Entendendo o punk como um movimento cultural e político, abordamos o seu surgimento na
Inglaterra e Estados Unidos e sua chegada ao Chile. Analisamos o processo de formação da juventude
punk e sua postura política no período ditatorial chileno, a resposta do movimento à transição
negociada e a desilusão com a democracia marcada por permanências da ditadura.El objetivo de este artículo es analizar el discurso del movimiento punk chileno durante
el periodo de la transición de la dictadura a la democracia a través del disco ¿Democracia?, de la
banda Los miserables, de 1991. Entendiendo al punk como un movimiento cultural y político,
abordamos su surgimiento en Inglaterra, Estado Unidos y su llegada a Chile. Analizamos el proceso
de formación de la juventud punk y su postura política durante el periodo dictatorial chileno, la
respuesta del movimiento a la transición negociada y la desilusión con la democracia marcada por
permanencias de la dictadur
Vlasov limit and discreteness effects in cosmological N-body simulations
We present the problematic of controlling the discreteness effects in
cosmological N-body simulations. We describe a perturbative treatment which
gives an approximation describing the evolution under self-gravity of a lattice
perturbed from its equilibrium, which allows to trace the evolution of the
fully discrete distribution until the time when particles approach one another
("shell-crossing"). Perturbed lattices are typical initial conditions for
cosmological N-body simulations and thus we can describe precisely the early
time evolution of these simulations. A quantitative comparison with fluid
Lagrangian theory permits to study discreteness effects in the linear regime of
the simulations. We show finally some work in progress about quantifying
discreteness effects in the non-perturbative (highly non-linear) regime of
cosmological N-body simulations by evolving different discretizations of the
same continuous density field.Comment: 8 pages, proceedings (refereed) of "Vlasovia 2006", 2nd int'l
workshop on the theory and applications of the Vlasov equation, Florence,
September 2006. A more detailed report on recent progress may be found at
arXiv:0805.135
Field notes on findings of threatened amphibian species in the central mountain range of western Panama
During field work along a transect in the Cordillera Central of western Panama between 2008 and 2010, we detected several populations of amphibian species which are considered as “Endangered” or “Critically Endangered” by the IUCN. Some of these species had suffered from serious population declines, probably due to chytridiomycosis, but all are generally threatened by habitat loss. We detected 53% of the Endangered and 56% of the Critically Endangered amphibian species that have previously been reported from within the investigated area. We report on findings of species that have not been found in Panama for many years, and provide locality data of newly discovered populations. There is a need to create a new protected area in the Cerro Colorado area of the Serranía de Tabasará, where we found 15% of the Endangered and Critically Endangered amphibian species known to Panama.Durante trabajo de campo en un transecto a lo largo de la Cordillera Central en el oeste de Panamá entre 2008 y 2010, encontramos varias poblaciones de anfibios que son considerados “En Peligro” o “En Peligro Crítico” por la UICN. Algunas de estas especies habían sufrido serias disminuciones de sus poblaciones, probablemente causadas por la quitridiomicosis, pero todas se encuentran amenazadas por pérdida de hábitat. Detectamos el 53% de las especies En Peligro y el 56% de las especies En Peligro Crítico que se habían reportado previamente en el área de estudio. Reportamos hallazgos de especies que no se habían avistado en Panamá por muchos años, así como localidades de poblaciones descubiertas por primera vez. Se requiere crear una nueva área de protección en los alrededores del Cerro Colorado en la Serranía de Tabasará, donde se han encontrado 15% de los anfibios En Peligro y En Peligro Crítico de todo Panamá
Use of flight interception traps of Malaise type and attractive traps for social wasps record (Vespidae: Polistinae)
The literature provides different methodologies for sampling social
wasps, including, flight intercept trap type Malaise and Attractive
trap, however, there is no consensus on its use. In this respect, the
aim of this study was to evaluate the best use of Malaise traps and
Attractive trap in biodiversity work of social wasps, and generate a
collection protocol for the use of these traps. The study was conducted
in the Parque Estadual do Rio Doce, located in the east of the state
of Minas Gerais, in the years 2000, 2001, 2002 and 2004 and in the
Botanical Garden of the Federal University of Juiz de Fora, located in
the southeastern state of Minas Gerais, in years 2011, 2012 and 2013.
15 species were collected using Malaise traps, and, 26 species of social
wasps were collected using Attractive traps. Although the negative
aspects of both traps, complementary methodologies surveys varying
social wasps are useful and it is recommended to choose for using in
accordance with the logistical field
A composition algorithm based on crossmodal taste-music correspondences
While there is broad consensus about the structural similarities between language and music, comparably less attention has been devoted to semantic correspondences between these two ubiquitous manifestations of human culture. We have investigated the relations between music and a narrow and bounded domain of semantics: the words and concepts referring to taste sensations. In a recent work, we found that taste words were consistently mapped to musical parameters. Bitter is associated with low-pitched and continuous music (legato), salty is characterized by silences between notes (staccato), sour is high pitched, dissonant and fast and sweet is consonant, slow and soft (Mesz et al., 2011). Here we extended these ideas, in a synergistic dialog between music and science, investigating whether music can be algorithmically generated from taste-words. We developed and implemented an algorithm that exploits a large corpus of classic and popular songs. New musical pieces were produced by choosing fragments from the corpus and modifying them to minimize their distance to the region in musical space that characterizes each taste. In order to test the capability of the produced music to elicit significant associations with the different tastes, musical pieces were produced and judged by a group of non-musicians. Results showed that participants could decode well above chance the taste-word of the composition. We also discuss how our findings can be expressed in a performance bridging music and cognitive science
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