3,842 research outputs found
The Hamiltonian BRST quantization of a noncommutative nonabelian gauge theory and its Seiberg-Witten map
We consider the Hamiltonian BRST quantization of a noncommutative non abelian
gauge theory. The Seiberg-Witten map of all phase-space variables, including
multipliers, ghosts and their momenta, is given in first order in the
noncommutative parameter . We show that there exists a complete
consistence between the gauge structures of the original and of the mapped
theories, derived in a canonical way, once we appropriately choose the map
solutions.Comment: 10 pages, Latex. Address adde
Regularization of a three-body problem with zero-range potentials
We propose a coordinate-space regularization of the three-body problem with
zero-range potentials. We include the effective range and the shape parameter
in the boundary condition of the zero-range potential. The proposed extended
zero-range model is tested against atomic helium trimers and is shown to
provide an adequate quantitative description of these systems
The spatially-resolved star formation histories of CALIFA galaxies: Implications for galaxy formation
This paper presents the spatially resolved star formation history (SFH) of
nearby galaxies with the aim of furthering our understanding of the different
processes involved in the formation and evolution of galaxies. To this end, we
apply the fossil record method of stellar population synthesis to a rich and
diverse data set of 436 galaxies observed with integral field spectroscopy in
the CALIFA survey. The sample covers a wide range of Hubble types, with stellar
masses ranging from to . Spectral
synthesis techniques are applied to the datacubes to retrieve the spatially
resolved time evolution of the star formation rate (SFR), its intensity
(), and other descriptors of the 2D-SFH in seven bins of
galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and five bins of stellar
mass. Our main results are: a) Galaxies form very fast independently of their
current stellar mass, with the peak of star formation at high redshift (). Subsequent star formation is driven by and morphology, with less
massive and later type spirals showing more prolonged periods of star
formation. b) At any epoch in the past the SFR is proportional to ,
with most massive galaxies having the highest absolute (but lowest specific)
SFRs. c) While nowadays is similar for all spirals, and
significantly lower in early type galaxies (ETG), in the past scales well with morphology. The central regions of today's ETGs are
where reached the highest values (Gyrpc), similar to those measured in high redshift
star forming galaxies. d) The evolution of in Sbc systems
matches that of models for Milky-Way-like galaxies, suggesting that the
formation of a thick disk may be a common phase in spirals at early epochs.Comment: 21 pages, 11 figures, 1 table, accepted for publication in Astronomy
& Astrophysics, abstract abridged for arXiv submissio
The spatially resolved star formation history of CALIFA galaxies: Cosmic time scales
This paper presents the mass assembly time scales of nearby galaxies observed
by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record
method of the stellar populations to the complete sample of the 3rd CALIFA data
release, with a total of 661 galaxies, covering stellar masses from 10
to 10 M and a wide range of Hubble types. We apply spectral
synthesis techniques to the datacubes and process the results to produce the
mass growth time scales and mass weighted ages, from which we obtain temporal
and spatially resolved information in seven bins of galaxy morphology and six
bins of stellar mass (M) and stellar mass surface density
(). We use three different tracers of the spatially resolved
star formation history (mass assembly curves, ratio of half mass to half light
radii, and mass-weighted age gradients) to test if galaxies grow inside-out,
and its dependence with galaxy stellar mass, , and morphology.
Our main results are as follows: (a) The innermost regions of galaxies assemble
their mass at an earlier time than regions located in the outer parts; this
happens at any given M, , or Hubble type, including
the lowest mass systems. (b) Galaxies present a significant diversity in their
characteristic formation epochs for lower-mass systems. This diversity shows a
strong dependence of the mass assembly time scales on and
Hubble type in the lower-mass range (10 to 10), but a very
mild dependence in higher-mass bins. (c) All galaxies show negative
log age gradients in the inner 1 HLR. The profile
flattens with increasing values of . There is no significant
dependence on M within a particular bin, except for
the lowest bin, where the gradients becomes steeper.Comment: 15 pages, 13 figures, 3 tables, accepted for publication in Astronomy
& Astrophysics. *Abridged abstract
Diagnóstico de sistemas de dessalinização de água salobra subterrânea em municípios do Estado da Paraíba-Brasil.
Embora, no Semi-Árido brasileiro, predomine o embasamento cristalino, com poços apresentando qualidade comprometida por sais, à tecnologia da dessalinização permite a potabilização dessas águas. Desde 1996 vem sendo implantados, equipamentos de dessalinização por osmose inversa visando o atendimento da demanda hídrica para consumo humano. No entanto, dificuldades estão presentes na implantação dos equipamentos, tais como a falta de operação e manutenção adequadas que causam a paralisação dos mesmos, e como a produção de rejeitos, os quais são água com elevados teores de sais, normalmente despejados ao solo sem qualquer critério, cujo maior impacto tem sido a erosão e a salinidade do solo. Assim, considerando que a Embrapa Semi-Árido pesquisa manejos dos rejeitos, a Fundação Banco do Brasil realizou parceria com a Embrapa, com o objetivo de avaliar 21 sistemas de dessalinização implantados no Estado da Paraíba. O presente artigo tem por objetivo apresentar um diagnóstico da atual situação dos sistemas da Paraíba, principalmente quanto aos aspectos de conservação, manutenção e operacionalização; aos parâmetros técnicos, à qualidade de água e aos impactos ambientais causados pelos rejeitos
Lighting conditions in home office and occupant's perception: Exploring drivers of satisfaction
This paper depicts lighting home office conditions within different countries and continents, emphasizing the user's satisfaction with the visual environment. The scope of this article is to investigate the drivers of participants' satisfaction with the lighting conditions at the home office. The study was developed by a team of international experts working together on Subtask A: User perspective and requirements, Task 61 IEA (International Energy Agency): Solutions for daylighting and electric lighting. An online survey was launched in December 2020 and closed on March 2021. The survey was implemented in the native languages of six participant countries (Brazil, Colombia, Denmark, Italy, Poland, and Japan) using Google Forms, and its dissemination was via various social media platforms. Measures of association between variables and predictive tests were run to explore which investigated aspects drove participants' satisfaction with the lighting conditions at the home office. We found some differences in satisfaction due to participants' sex, occupation, and participants' continent of residence. Females were more satisfied with daylight than males. Associations between the perception of seven light descriptors and satisfaction showed differences between East Asians and the rest of the participants, which might be related to the high dependence of the formers on electric lighting even when daylight is available. Design features as southern facades, the distance from the working area to the window, type of internal sun shading were related to daylighting satisfaction. Moreover, satisfaction with the general light level and the electric light was higher for those participants who did not need to switch on the ceiling, floor, or desk lamp when daylight was available. We found that an external view composed of 3 layers and the sky's visibility afforded a higher satisfaction with the window view. Having an independent room for the home office appeared to be related to a higher willingness to continue in the home office. Likewise, higher satisfaction with the overall visual environment and window view appeared to increase the willingness to continue working from home. Bridging the gap amid cultural differences and daylighting and lighting satisfaction is needed, particularly, relational studies between design features –as a response of cultural, climatic, and local practices- and occupants' preferences and acceptability. Thus, our understanding of occupants' responses will be more comprehensive. Engaging further research and measures to improve the visual environment and overall indoor environmental quality in dwellings is now a necessary step
Produtividade da bananeira submetida a diferentes níveis de irrigação e densidade de plantas.
O Brasil se apresenta como o quinto maior produtor de banana do mundo, com produtividade média, em 2011, de 14,54 t ha-1. O objetivo do presente trabalho foi avaliar as características do cacho da bananeira cv. Prata anã em seu terceiro ciclo, submetida a diferentes níveis de irrigação e densidade de plantas nas condições de Cruz das Almas-BA
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