2,986 research outputs found
Superspace formulation of general massive gauge theories and geometric interpretation of mass-dependent BRST symmetries
A superspace formulation is proposed for the osp(1,2)-covariant Lagrangian
quantization of general massive gauge theories. The superalgebra os0(1,2) is
considered as subalgebra of sl(1,2); the latter may be considered as the
algebra of generators of the conformal group in a superspace with two
anticommuting coordinates. The mass-dependent (anti)BRST symmetries of proper
solutions of the quantum master equations in the osp(1,2)-covariant formalism
are realized in that superspace as invariance under translations combined with
mass-dependent special conformal transformations. The Sp(2) symmetry - in
particular the ghost number conservation - and the "new ghost number"
conservation are realized as invariance under symplectic rotations and
dilatations, respectively. The transformations of the gauge fields - and of the
full set of necessarily required (anti)ghost and auxiliary fields - under the
superalgebra sl(1,2) are determined both for irreducible and first-stage
reducible theories with closed gauge algebra.Comment: 35 pages, AMSTEX, precision of reference
Creating figures: why re-imagining urban structure supports a regenerative urban model
Some authors describe the contemporary metropolis like the field where co-exist simultaneous strategies of exploitation of fragmentary opportunities provided by the specific conditions of places (Florida, Bagnasco, SolĂĄ-Morales): physical (geography, infrastructures, etc.), social (people, culture and local values, etc.) and economic conditions. In their opinion, the causes of the âlateralâ development of the city could be (i) the relationships between the different elements of the land mosaic (Forman) and (ii) the fragmentary logics of the current urban realities. This important process of transformation would integrate the classic âlinealâ growth, more related to the urban rising along infrastructures. The result of these interactions is the change of scales in the performing of contemporary urban phenomena. Several authors have been interested in studying this new reality, called âexopolisâ (Soja), city-region (De las Rivas, Portas & al.) or metropolizated territory (Indovina, MonclĂșs). Those not-conventional approaches are necessary to understand the contemporary urban condition and its complex, unstable, transient dynamics. Nowadays, several traditional concepts and ideas have become less useful and too rigid to achieve this target. This lack of effectiveness regards the discipline as a whole, divided between sectorial analysis and fragmentary solutions. In our opinion, using figures as âimages with the potential to represent new territorial realitiesâ is one of the most important steps to produce an innovative and non-conventional understanding of post-metropolitan (Soja) urban space. This paper is aimed at explaining why figures are more useful than images to understand the complex urban pattern of current territory, as well as demonstrating this idea with the case studies of Valladolid and its emerging urban area. The result is a way to show the structure of this territory, which is more coherent with a contemporary narrative of space, and closer to its spatial and temporal dimensions. This is something not completely original but in this paper we present our views on it
A study on PDC drill bits quality
The quality of innovating PDC (Polycrystalline Diamond Compact) bits materials needs to be determined with accuracy by measuring cutting efficiency and wear rate, both related to the overall mechanical properties. An original approach is developed to encompass cutting efficiency and wear contribution to the overall sample quality. Therefore, a lathe-type test device was used to abrade specific samples from various manufacturers. Post-experiment analyzes are based on models establishing coupled relationships between cutting and friction stresses related to the drag bits excavation mechanism. These models are implemented in order to evaluate cutting efficiency and to estimate wear of the diamond insert. Phase analysis by XRD and finite element simulations were performed to explain the role of physicochemical parameters on the calculated quality factor values. Four main properties of PDC material were studied to explain quality results obtained in this study: cobalt content in samples that characterizes hardness/fracture toughness compromise, undesired phase as tungsten carbide weakening diamond structure, diamond grains sizes and residual stresses distribution affecting abrasion resistance
Scaling in many-body systems and proton structure function
The observation of scaling in processes in which a weakly interacting probe
delivers large momentum to a many-body system simply reflects the
dominance of incoherent scattering off target constituents. While a suitably
defined scaling function may provide rich information on the internal dynamics
of the target, in general its extraction from the measured cross section
requires careful consideration of the nature of the interaction driving the
scattering process. The analysis of deep inelastic electron-proton scattering
in the target rest frame within standard many-body theory naturally leads to
the emergence of a scaling function that, unlike the commonly used structure
functions and , can be directly identified with the intrinsic proton
response.Comment: 11 pages, 4 figures. Proceedings of the 11th Conference on Recent
Progress in Many-Body Theories, Manchester, UK, July 9-13 200
AnĂĄlise faunĂstica e flutuação populacional de cigarrinhas (Cicadellidae: Cicadellinae) potenciais vetoras de Xylella fastidiosa associadas Ă cultura da videira nos municĂpios de Bento Gonçalves e Pinto Bandeira, RS.
A cultura da videira Ă© de grande importĂąncia econĂŽmica e social, proporcionando a geração de empregos de forma direta ou indireta. PaĂses da AmĂ©rica do Norte e Central estĂŁo enfrentando problemas causados pela doença de Pierce (?Pierce?s disease), provocada pela bactĂ©ria Xylella fastidiosa Wells et al., 1987, onde as cigarrinhas (Cicadellidae) atuam como vetoras. O objetivo desse estudo foi realizar a anĂĄlise faunĂstica e conhecer a flutuação populacional das espĂ©cies de cigarrinhas (Cicadellidae: Cicadellinae) potenciais vetoras de Xylella fastidiosa associadas Ă cultura da videira em Bento Gonçalves e Pinto Bandeira, Rio Grande do Sul, Brasil. Para o trabalho foram realizadas coletas com cartĂ”es adesivos amarelos, medindo 8,5 x 11,5 cm em quatro vinhedos comerciais de Vitis vinifera (cultivar Merlot), localizados na cidade de Bento Gonçalves (dois no Vale dos Vinhedos) e dois em Pinto Bandeira. As amostragens foram realizadas no perĂodo de janeiro de 2011 a dezembro de 2012. Ao longo do perĂodo de amostragem foram coletados 5745 espĂ©cimes e identificadas as espĂ©cies de Cicadellinae comprovadamente vetoras de X. fastidiosa em outras culturas no Brasil, destacando a ocorrĂȘncia em todas as ĂĄreas amostradas: Cicadellini - B. xanthophis, H. similis, P. gratiosa e S. grossa; Proconiini - A. citrina, H. ignorata e O. facialis. Nos quatro vinhedos o pico populacional das cigarrinhas ocorreu nos meses de fevereiro e novembro com um declĂnio na população no mĂȘs de junho
Towards equity and justice in ocean sciences
The global scientific community is currently going through a self-reckoning in which it is questioning and re-examining its existing practices, many of which are based on colonial and neo-colonial perceptions. This is particularly acute for the ocean research community, where unequal and unbalanced international collaborations have been rife. Consequently, numerous discussions and calls have been made to change the current status quo by developing guidelines and frameworks addressing the key issues plaguing our community. Here, we provide an overview of the key topics and issues that the scientific community has debated over the last three to four years, with an emphasis on ocean research, coupled with actions per stakeholder groups (research community, institutions, funding agencies, and publishers). We also outline some key discussions that are currently missing and suggest a path forward to tackle these gaps. We hope this contribution will further accelerate efforts to bring more equity and justice into ocean sciences
Optical Line Emission from z6.8 Sources with Deep Constraints on Ly Visibility
We analyze a sample of -dropout galaxies in the CANDELS GOODS South and
UDS fields that have been targeted by a dedicated spectroscopic campaign aimed
at detecting their Ly line. Deep IRAC observations at 3.6 and 4.5
m are used to determine the strength of optical emission lines affecting
these bands at z6.5-6.9 in order to i) investigate possible physical
differences between Ly emitting and non-emitting sources; ii) constrain
the escape fraction of ionizing photons; iii) provide an estimate of the
specific star-formation rate at high redshifts. We find evidence of strong
[OIII]+H emission in the average (stacked) SEDs of galaxies both with
and without Ly emission. The blue IRAC [3.6]-[4.5] color of the stack
with detected Ly line can be converted into a rest-frame equivalent
width EW([OIII]+H)=1500 assuming a flat intrinsic
stellar continuum. This strong optical line emission enables a first estimate
of f20% on the escape fraction of ionizing photons from
Ly detected objects. The objects with no Ly line show less
extreme EW([OIII]+H)=520 suggesting different
physical conditions of the HII regions with respect to Ly-emitting
ones, or a larger f. The latter case is consistent with a combined
evolution of f and the neutral hydrogen fraction as an explanation of
the lack of bright Ly emission at z6. A lower limit on the specific
star formation rate, SSFR9.1 for galaxies at these redshifts can be derived from the
spectroscopically confirmed sample.Comment: 10 pages, 7 figures; The Astrophysical Journal in press; matched to
the published versio
Entanglement and purity of two-mode Gaussian states in noisy channels
We study the evolution of purity, entanglement and total correlations of
general two--mode Gaussian states of continuous variable systems in arbitrary
uncorrelated Gaussian environments. The time evolution of purity, Von Neumann
entropy, logarithmic negativity and mutual information is analyzed for a wide
range of initial conditions. In general, we find that a local squeezing of the
bath leads to a faster degradation of purity and entanglement, while it can
help to preserve the mutual information between the modes.Comment: 10 pages, 8 figure
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