Dynamical Symmetry Breaking With a Fourth Generation

Adding a fourth generation to the Standard Model and assuming it to be valid up to some cutoff \Lambda, we show that electroweak symmetry is broken by radiative corrections due to the fourth generation. The effects of the fourth generation are isolated using a Lagrangian with a genuine scalar without self-interactions at the classical level. For masses of the fourth generation consistent with electroweak precision data (including the B \rightarrow K \pi\ CP asymmetries) we obtain a Higgs mass of the order of a few hundreds GeV and a cutoff \Lambda\ around 1-2 TeV. We study the reliability of the perturbative treatment used to obtain these results taking into account the running of the Yukawa couplings of the fourth quark generation with the aid of the Renormalization Group (RG) equations, finding similar allowed values for the Higgs mass but a slightly lower cut-off due to the breaking of the perturbative regime. Such low cut-off means that the effects of new physics needed to describe electroweak interactions at energy above \Lambda\ should be measurable at the LHC. We use the minimal supersymmetric extension of the standard model with four generations as an explicit example of models realizing the dynamical electroweak symmetry breaking by radiative corrections and containing new physics. Here, the cutoff is replaced by the masses of the squarks and electroweak symmetry breaking by radiative corrections requires the squark masses to be of the order of 1 TeV.Comment: 20 pages, 7 figures. New section adde

Ecologia do desenvolvimento profissional das crianças: uma revisão da literatura

Previous efforts to elaborate an organizing framework for the study of children’s career development identified its main dimensions and processes. However, the existing literature on children’s ecological subsystems is scarce. This article presents a literature review of the context of children’s career development. Based on Bronfenbrenner’s theory, 36 eligible articles covered the following subjects: the Microsystems family and school; the mesosystems family-school/peer-school relations and antecedents of transitions; the exosystems parents’ work situation, social class, curriculum and teachers’ professional development; the macrosystems ethnicity and culture; and the chronosystems passage of time over the life-course and across generations. An ecological perspective can be included in an organizing framework of children’s careers and support further research and intervention. Empirical and practical implications are discussed.Esforços prévios para organizar um modelo organizador do estudo do desenvolvimento profissional das crianças têm identificado as suas principais dimensões e processos. Contudo, a literatura existente sobre os subsistemas ecológicos das crianças é escassa. Este artigo apresenta uma revisão da literatura sobre os contextos de desenvolvimento profissional das crianças. De acordo com a teoria de Bronfenbrenner, 36 artigos elegidos abordam: os microssistemas família e escola; os mesossistemas família-escola/pares-escola e antecedentes de transições; os exossistemas situação profissional parental, classe social, currículo e desenvolvimento profissional de professores; os macrossistemas etnia e cultura; e os cronossistemas passagem do tempo no ciclo vital e entre gerações. Uma perspetiva ecológica pode ser incluída em um modelo organizador do desenvolvimento profissional das crianças e apoiar ivestigações e intervenção futuras. Discutem-se implicações empíricas e práticas.(undefined)info:eu-repo/semantics/publishedVersio

Theory of Second and Higher Order Stochastic Processes

This paper presents a general approach to linear stochastic processes driven by various random noises. Mathematically, such processes are described by linear stochastic differential equations of arbitrary order (the simplest non-trivial example is $\ddot x = R(t)$, where $R(t)$ is not a Gaussian white noise). The stochastic process is discretized into $n$ time-steps, all possible realizations are summed up and the continuum limit is taken. This procedure often yields closed form formulas for the joint probability distributions. Completely worked out examples include all Gaussian random forces and a large class of Markovian (non-Gaussian) forces. This approach is also useful for deriving Fokker-Planck equations for the probability distribution functions. This is worked out for Gaussian noises and for the Markovian dichotomous noise.Comment: 35 pages, PlainTex, accepted for publication in Phys Rev. E

Pinning of spiral fluxons by giant screw dislocations in YBa_2Cu_3O_7 single crystals: Josephson analog of the fishtail effect

By using a highly sensitive homemade AC magnetic susceptibility technique, the magnetic flux penetration has been measured in YBa_2Cu_3O_7 single crystals with giant screw dislocations (having the structure of the Archimedean spirals) exhibiting a=3 spiral turnings, the pitch b=18.7 microns and the step height c=1.2nm (the last parameter is responsible for creation of extended weak-link structure around the giant defects). The magnetic field applied parallel to the surface enters winding around the weak-link regions of the screw in the form of the so-called spiral Josephson fluxons characterized by the temperature dependent pitch b_f(T). For a given temperature, a stabilization of the fluxon structure occurs when b_f(T) matches b (meaning an optimal pinning by the screw dislocations) and manifests itself as a pronounced low-field peak in the dependence of the susceptibility on magnetic field (applied normally to the surface) in the form resembling the high-field (Abrikosov) fishtail effect.Comment: see also http://www.jetpletters.ac.ru/ps/1886/article_28701.shtm

Enraizamento de miniestacas de erva-mate sob diferentes ambientes.

Pouco se conhece a respeito da propagação vegetativa da erva-mate, principalmente em relação à miniestaquia e aos aspectos relacionados ao ambiente de enraizamento. O estudo objetivou avaliar o efeito do ambiente inicial de enraizamento sobre a sobrevivência, vigor da parte aérea e enraizamento de miniestacas da espécie. O delineamento experimental foi o inteiramente casualizado em arranjo fatorial (3x2), sendo três clones (A7, A21 e A35) e dois ambientes de enraizamento (casa-de-vegetação simples, sem controle de temperatura e umidade e casa-de-vegetação automatizada). A sobrevivência das miniestacas na saída das casas de enraizamento e na casa-de-sombra não foram influenciadas pelo ambiente testado, com variação de 51,8 % a 71,9 %. Os clones A7 e A21 não diferiram significativamente quanto ao enraizamento, com médias de 49,1 % e 46,4 %, respectivamente. Contudo, o clone A35 mostrou-se superior quando proveniente da casa-de-vegetação automatizada, com 62,5 % de enraizamento. A casa-de-vegetação automatizada favoreceu tanto o número de folhas quanto o número e comprimento das brotações emitidas. A miniestaquia de erva-mate pode ser considerada tecnicamente viável em ambos os ambientes de enraizamento testados, apresentando resultados semelhantes