330 research outputs found
Muon Anomalous Magnetic Moment and Lepton Flavor Violation
A non-universal interaction, which involves only the third family leptons
induces lepton flavor violating couplings and contributes to the anomalous
magnetic moment of muon. In this paper, we study the effects of non-universal
interaction on muon (g-2) and rare decay by using an
effective lagrangian technique, and a phenomenological model where
couples only to the third family lepton. We find that the deviation
from the theory can be explained and the induced rate
could be very close to the current experimental limit. In the model,
has to be lighter than 2.6 TeV.Comment: references added, the version to appear in PR
The 3-3-1 model with S_4 flavor symmetry
We construct a 3-3-1 model based on family symmetry S_4 responsible for the
neutrino and quark masses. The tribimaximal neutrino mixing and the diagonal
quark mixing have been obtained. The new lepton charge \mathcal{L} related to
the ordinary lepton charge L and a SU(3) charge by L=2/\sqrt{3} T_8+\mathcal{L}
and the lepton parity P_l=(-)^L known as a residual symmetry of L have been
introduced which provide insights in this kind of model. The expected vacuum
alignments resulting in potential minimization can origin from appropriate
violation terms of S_4 and \mathcal{L}. The smallness of seesaw contributions
can be explained from the existence of such terms too. If P_l is not broken by
the vacuum values of the scalar fields, there is no mixing between the exotic
and the ordinary quarks at the tree level.Comment: 20 pages, revised versio
Electroweak Radiative Corrections to Parity-Violating Electroexcitation of the
We analyze the degree to which parity-violating (PV) electroexcitation of the
resonance may be used to extract the weak neutral axial vector
transition form factors. We find that the axial vector electroweak radiative
corrections are large and theoretically uncertain, thereby modifying the
nominal interpretation of the PV asymmetry in terms of the weak neutral form
factors. We also show that, in contrast to the situation for elastic electron
scattering, the axial PV asymmetry does not vanish at the photon
point as a consequence of a new term entering the radiative corrections. We
argue that an experimental determination of these radiative corrections would
be of interest for hadron structure theory, possibly shedding light on the
violation of Hara's theorem in weak, radiative hyperon decays.Comment: RevTex, 76 page
Saberes na graduação em administração : um estudo nas universidades federais do estado de Minas Gerais
Conforme censo da educação superior no Brasil de 2015, o curso de administração
é um dos mais procurados no país. Esta pesquisa teve como objetivo investigar
como surgem e são legitimados os saberes na graduação em administração das
universidades federais mineiras. Na tentativa de responder a este objetivo, foi
realizada uma caracterização do curso, investigados os saberes veiculados na
matriz curricular e analisada a produção de verdades na graduação. A abordagem
metodológica escolhida para este estudo foi a da pesquisa qualitativa por meio da
técnica de análise de conteúdo. A produção dos dados foi feita mediante a análise
de um conjunto de 13 (treze) projetos pedagógicos. Como resultados foram
identificados os objetivos do pensamento crítico e reflexivo, do campo de atuação e
da qualificação técnica, os perfis responsável e generalista e os métodos da
transmissão, da prática e da construção do saber. Em relação aos saberes
veiculados na matriz curricular, foram investigados os saberes de formação básica,
nas funções organizacionais, das especificidades regionais e organizacionais,
formação social, ambiental e ética e em pesquisa. Assim, com a análise das
características do curso com os saberes veiculados nas matrizes curriculares foi
possível analisar a produção de verdades na graduação. Os objetivos do campo de
atuação, da qualificação técnica e o perfil generalista são as características que se
relacionam com os saberes mais presentes na graduação, de modo que os objetivos
econômicos ainda estão ocupando uma posição hegemônica na formação dos
bacharéis em administração entre as universidades pesquisadas.According to a census of higher education in Brazil in 2015, the administration course
is one of the most sought after in the country. This research had as objective to
investigate how the knowledge and the knowledge in the administration graduation of
the federal universities of Minas Gerais arise and are legitimized. In an attempt to
respond to this objective, a course characterization was carried out, the knowledge
conveyed in the curricular matrix was investigated and the production of truths at the
undergraduate level was analyzed. The methodological approach chosen for this
study was that of the qualitative research through the technique of content analysis.
The data were produced through the analysis of a set of 13 (thirteen) pedagogical
projects. As results, the objectives of critical and reflexive thinking, the field of
performance and technical qualification, the responsible and generalist profiles and
the methods of transmission, practice and knowledge construction were identified. In
relation to the knowledge conveyed in the curricular matrix, the basic training
knowledge in organizational functions, regional and organizational specificities,
social, environmental and ethical training and research were investigated. Thus, with
the analysis of the characteristics of the course with the knowledge conveyed in the
curricular matrices, it was possible to analyze the production of truths in the
undergraduate course. The objectives of the field of activity, the technical
qualification and the generalist profile are the characteristics that are related to the
most present knowledge in the undergraduate, so that the economic objectives are
still occupying a hegemonic position in the formation of the bachelors in
administration among the researched universities
Ionization degree of the electron-hole plasma in semiconductor quantum wells
The degree of ionization of a nondegenerate two-dimensional electron-hole
plasma is calculated using the modified law of mass action, which takes into
account all bound and unbound states in a screened Coulomb potential.
Application of the variable phase method to this potential allows us to treat
scattering and bound states on the same footing. Inclusion of the scattering
states leads to a strong deviation from the standard law of mass action. A
qualitative difference between mid- and wide-gap semiconductors is
demonstrated. For wide-gap semiconductors at room temperature, when the bare
exciton binding energy is of the order of T, the equilibrium consists of an
almost equal mixture of correlated electron-hole pairs and uncorrelated free
carriers.Comment: 22 pages, 6 figure
The cosmic ray positron excess and neutralino dark matter
Using a new instrument, the HEAT collaboration has confirmed the excess of
cosmic ray positrons that they first detected in 1994. We explore the
possibility that this excess is due to the annihilation of neutralino dark
matter in the galactic halo. We confirm that neutralino annihilation can
produce enough positrons to make up the measured excess only if there is an
additional enhancement to the signal. We quantify the `boost factor' that is
required in the signal for various models in the Minimal Supersymmetric
Standard Model parameter space, and study the dependence on various parameters.
We find models with a boost factor greater than 30. Such an enhancement in the
signal could arise if we live in a clumpy halo. We discuss what part of
supersymmetric parameter space is favored (in that it gives the largest
positron signal), and the consequences for other direct and indirect searches
of supersymmetric dark matter.Comment: 11 pages, 6 figures, matches published version (PRD
Search for TeV Scale Physics in Heavy Flavour Decays
The subject of heavy flavour decays as probes for physics beyond the TeV
scale is covered from the experimental perspective. Emphasis is placed on the
more traditional Beyond the Standard Model topics that have potential for
impact in the short term, with the physics explained. We do unabashedly promote
our own phemonenology work.Comment: 10 pages, 9 figures (now fixed); Submitted for the SUSY07 proceeding
25 Years of Self-organized Criticality: Concepts and Controversies
Introduced by the late Per Bak and his colleagues, self-organized criticality (SOC) has been one of the most stimulating concepts to come out of statistical mechanics and condensed matter theory in the last few decades, and has played a significant role in the development of complexity science. SOC, and more generally fractals and power laws, have attracted much comment, ranging from the very positive to the polemical. The other papers (Aschwanden et al. in Space Sci. Rev., 2014, this issue; McAteer et al. in Space Sci. Rev., 2015, this issue; Sharma et al. in Space Sci. Rev. 2015, in preparation) in this special issue showcase the considerable body of observations in solar, magnetospheric and fusion plasma inspired by the SOC idea, and expose the fertile role the new paradigm has played in approaches to modeling and understanding multiscale plasma instabilities. This very broad impact, and the necessary process of adapting a scientific hypothesis to the conditions of a given physical system, has meant that SOC as studied in these fields has sometimes differed significantly from the definition originally given by its creators. In Bak’s own field of theoretical physics there are significant observational and theoretical open questions, even 25 years on (Pruessner 2012). One aim of the present review is to address the dichotomy between the great reception SOC has received in some areas, and its shortcomings, as they became manifest in the controversies it triggered. Our article tries to clear up what we think are misunderstandings of SOC in fields more remote from its origins in statistical mechanics, condensed matter and dynamical systems by revisiting Bak, Tang and Wiesenfeld’s original papers
Adaptabilidade e estabilidade de populações de milho-pipoca relacionadas por ciclos de seleção
Os objetivos deste trabalho foram estimar os parâmetros de adaptabilidade e estabilidade em populações de milho-pipoca relacionadas por ciclos de seleção, inferir sobre a eficiência dos métodos de seleção pelos quais as populações foram obtidas e avaliar os efeitos da seleção sobre os parâmetros de adaptabilidade e estabilidade. Vinte e cinco populações e três testemunhas comerciais foram avaliadas em 14 ensaios realizados nos anos agrícolas de 2003/2004, 2004/2005, 2006/2007, 2008/2009 e 2009/2010, em sete locais. Utilizou-se o delineamento experimental de blocos completos ao acaso, com quatro repetições. Foram analisadas a capacidade de expansão, avaliada em forno de microondas e na pipocadora Metric Weight Volume Tester (MWVT), além da produtividade de grãos. Utilizou-se o método de adaptabilidade e estabilidade de Eberhart & Russell. Em geral, as populações base e melhoradas apresentaram previsibilidade de comportamento em resposta às variações de ambiente. A seleção pode provocar mudanças nos padrões de adaptabilidade e estabilidade, e as diferentes estratégias de seleção empregadas na obtenção das populações apresentaram eficiências semelhante
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