959 resultados para statistical quantum field theory
Resumo:
This paper presents a search for new particles in events with one lepton (electron or muon) and missing transverse momentum using 20.3 fb−1 of proton-proton collision data at TeX = 8 TeV recorded by the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. A W ′ with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 3.24 TeV. Excited chiral bosons (W *) with equivalent coupling strengths are excluded for masses up to 3.21 TeV. In the framework of an effective field theory limits are also set on the dark matter-nucleon scattering cross-section as well as the mass scale M * of the unknown mediating interaction for dark matter pair production in association with a leptonically decaying W.
Resumo:
search is presented for production of dark-matter particles recoiling against a leptonically decaying Z boson in 20.3 fb−1 of pp collisions at √s=8 TeV with the ATLAS detector at the Large Hadron Collider. Events with large missing transverse momentum and two oppositely charged electrons or muons consistent with the decay of a Z boson are analyzed. No excess above the Standard Model prediction is observed. Limits are set on the mass scale of the contact interaction as a function of the dark-matter particle mass using an effective field theory description of the interaction of dark matter with quarks or with Z bosons. Limits are also set on the coupling and mediator mass of a model in which the interaction is mediated by a scalar particle.
Resumo:
Even though the Standard Model with a Higgs mass mH = 125GeV possesses no bulk phase transition, its thermodynamics still experiences a "soft point" at temperatures around T = 160GeV, with a deviation from ideal gas thermodynamics. Such a deviation may have an effect on precision computations of weakly interacting dark matter relic abundances if their mass is in the few TeV range, or on leptogenesis scenarios operating in this temperature range. By making use of results from lattice simulations based on a dimensionally reduced effective field theory, we estimate the relevant thermodynamic functions across the crossover. The results are tabulated in a numerical form permitting for their insertion as a background equation of state into cosmological particle production/decoupling codes. We find that Higgs dynamics induces a non-trivial "structure" visible e.g. in the heat capacity, but that in general the largest radiative corrections originate from QCD effects, reducing the energy density by a couple of percent from the free value even at T > 160GeV.
Resumo:
In this paper, we study the reduction of four-dimensional Seiberg duality to three dimensions from a brane perspective. We reproduce the nonperturbative dynamics of three-dimensional field theory via a T–duality at a finite radius and the action of Euclidean D–strings. In this way, we also overcome certain issues regarding the brane description of Aharony duality. Moreover, we apply our strategy to more general dualities, such as toric duality for M2–branes and dualities with adjoint matter fields.
Resumo:
We present an overview of a perturbative-kinetic approach to jet propagation, energy loss, and momentum broadening in a high temperature quark–gluon plasma. The leading-order kinetic equations describe the interactions between energetic jet-particles and a non-abelian plasma, consisting of on-shell thermal excitations and soft gluonic fields. These interactions include ↔ scatterings, collinear bremsstrahlung, and drag and momentum diffusion. We show how the contribution from the soft gluonic fields can be factorized into a set of Wilson line correlators on the light-cone. We review recent field-theoretical developments, rooted in the causal properties of these correlators, which simplify the calculation of the appropriate Wilson lines in thermal field theory. With these simplifications lattice measurements of transverse momentum broadening have become possible, and the kinetic equations describing parton transport have been extended to next-to-leading order in the coupling g.
Resumo:
Introduction: According to the ecological view, coordination establishes byvirtueof social context. Affordances thought of as situational opportunities to interact are assumed to represent the guiding principles underlying decisions involved in interpersonal coordination. It’s generally agreed that affordances are not an objective part of the (social) environment but that they depend on the constructive perception of involved subjects. Theory and empirical data hold that cognitive operations enabling domain-specific efficacy beliefs are involved in the perception of affordances. The aim of the present study was to test the effects of these cognitive concepts in the subjective construction of local affordances and their influence on decision making in football. Methods: 71 football players (M = 24.3 years, SD = 3.3, 21 % women) from different divisions participated in the study. Participants were presented scenarios of offensive game situations. They were asked to take the perspective of the person on the ball and to indicate where they would pass the ball from within each situation. The participants stated their decisions in two conditions with different game score (1:0 vs. 0:1). The playing fields of all scenarios were then divided into ten zones. For each zone, participants were asked to rate their confidence in being able to pass the ball there (self-efficacy), the likelihood of the group staying in ball possession if the ball were passed into the zone (group-efficacy I), the likelihood of the ball being covered safely by a team member (pass control / group-efficacy II), and whether a pass would establish a better initial position to attack the opponents’ goal (offensive convenience). Answers were reported on visual analog scales ranging from 1 to 10. Data were analyzed specifying general linear models for binomially distributed data (Mplus). Maximum likelihood with non-normality robust standard errors was chosen to estimate parameters. Results: Analyses showed that zone- and domain-specific efficacy beliefs significantly affected passing decisions. Because of collinearity with self-efficacy and group-efficacy I, group-efficacy II was excluded from the models to ease interpretation of the results. Generally, zones with high values in the subjective ratings had a higher probability to be chosen as passing destination (βself-efficacy = 0.133, p < .001, OR = 1.142; βgroup-efficacy I = 0.128, p < .001, OR = 1.137; βoffensive convenience = 0.057, p < .01, OR = 1.059). There were, however, characteristic differences in the two score conditions. While group-efficacy I was the only significant predictor in condition 1 (βgroup-efficacy I = 0.379, p < .001), only self-efficacy and offensive convenience contributed to passing decisions in condition 2 (βself-efficacy = 0.135, p < .01; βoffensive convenience = 0.120, p < .001). Discussion: The results indicate that subjectively distinct attributes projected to playfield zones affect passing decisions. The study proposes a probabilistic alternative to Lewin’s (1951) hodological and deterministic field theory and enables insight into how dimensions of the psychological landscape afford passing behavior. Being part of a team, this psychological landscape is not only constituted by probabilities that refer to the potential and consequences of individual behavior, but also to that of the group system of which individuals are part of. Hence, in regulating action decisions in group settings, informers are extended to aspects referring to the group-level. References: Lewin, K. (1951). In D. Cartwright (Ed.), Field theory in social sciences: Selected theoretical papers by Kurt Lewin. New York: Harper & Brothers.
Resumo:
Cervical cancer is the leading cause of death and disease from malignant neoplasms among women in developing countries. Even though the Pap smear has significantly decreased the number of deaths from cervical cancer in the past years, it has its limitations. Researchers have developed an automated screening machine which can potentially detect abnormal cases that are overlooked by conventional screening. The goal of quantitative cytology is to classify the patient's tissue sample based on quantitative measurements of the individual cells. It is also much cheaper and potentially can take less time. One of the major challenges of collecting cells with a cytobrush is the possibility of not sampling any existing dysplastic cells on the cervix. Being able to correctly classify patients who have disease without the presence of dysplastic cells could improve the accuracy of quantitative cytology algorithms. Subtle morphologic changes in normal-appearing tissues adjacent to or distant from malignant tumors have been shown to exist, but a comparison of various statistical methods, including many recent advances in the statistical learning field, has not previously been done. The objective of this thesis is to use different classification methods applied to quantitative cytology data for the detection of malignancy associated changes (MACs). In this thesis, Elastic Net is the best algorithm. When we applied the Elastic Net algorithm to the test set, we combined the training set and validation set as "training" set and used 5-fold cross validation to choose the parameter for Elastic Net. It has a sensitivity of 47% at 80% specificity, an AUC 0.52, and a partial AUC 0.10 (95% CI 0.09-0.11).^
Resumo:
Este trabajo tiene como propósito presentar algunos potenciales aportes de la Teoría del Campo de Pierre Bourdieu en tres niveles de lectura: El de los fenómenos a estudiar en el marco de un proyecto de investigación, el del estatuto de esta teoría dentro de la Teoría Social Contemporánea y, finalmente, el de la posición del que escribe dentro del campo de investigación. El énfasis va a ponerse en el nivel de los fenómenos que es posible reconstruir a partir del análisis de fragmentos de documentos producidos en el trabajo de campo. Finalmente se harán algunas conclusiones sobre el uso de la categoría capital corporal para designar una subespecie de capital simbólico en el dominio de las prácticas corporales parte de la intervención de la Educación Física en una cárcel de la Provincia de Buenos Aires.
Resumo:
Este trabajo tiene como propósito presentar algunos potenciales aportes de la Teoría del Campo de Pierre Bourdieu en tres niveles de lectura: El de los fenómenos a estudiar en el marco de un proyecto de investigación, el del estatuto de esta teoría dentro de la Teoría Social Contemporánea y, finalmente, el de la posición del que escribe dentro del campo de investigación. El énfasis va a ponerse en el nivel de los fenómenos que es posible reconstruir a partir del análisis de fragmentos de documentos producidos en el trabajo de campo. Finalmente se harán algunas conclusiones sobre el uso de la categoría capital corporal para designar una subespecie de capital simbólico en el dominio de las prácticas corporales parte de la intervención de la Educación Física en una cárcel de la Provincia de Buenos Aires.
Resumo:
Este trabajo tiene como propósito presentar algunos potenciales aportes de la Teoría del Campo de Pierre Bourdieu en tres niveles de lectura: El de los fenómenos a estudiar en el marco de un proyecto de investigación, el del estatuto de esta teoría dentro de la Teoría Social Contemporánea y, finalmente, el de la posición del que escribe dentro del campo de investigación. El énfasis va a ponerse en el nivel de los fenómenos que es posible reconstruir a partir del análisis de fragmentos de documentos producidos en el trabajo de campo. Finalmente se harán algunas conclusiones sobre el uso de la categoría capital corporal para designar una subespecie de capital simbólico en el dominio de las prácticas corporales parte de la intervención de la Educación Física en una cárcel de la Provincia de Buenos Aires.
Resumo:
The threshold behavior of the transport properties of a random metal in the critical region near a metal–insulator transition is strongly affected by the measuring electromagnetic fields. In spite of the randomness, the electrical conductivity exhibits striking phase-coherent effects due to broken symmetry, which greatly sharpen the transition compared with the predictions of effective medium theories, as previously explained for electrical conductivities. Here broken symmetry explains the sign reversal of the T → 0 magnetoconductance of the metal–insulator transition in Si(B,P), also previously not understood by effective medium theories. Finally, the symmetry-breaking features of quantum percolation theory explain the unexpectedly very small electrical conductivity temperature exponent α = 0.22(2) recently observed in Ni(S,Se)2 alloys at the antiferromagnetic metal–insulator transition below T = 0.8 K.
Resumo:
We introduce a computational method to optimize the in vitro evolution of proteins. Simulating evolution with a simple model that statistically describes the fitness landscape, we find that beneficial mutations tend to occur at amino acid positions that are tolerant to substitutions, in the limit of small libraries and low mutation rates. We transform this observation into a design strategy by applying mean-field theory to a structure-based computational model to calculate each residue's structural tolerance. Thermostabilizing and activity-increasing mutations accumulated during the experimental directed evolution of subtilisin E and T4 lysozyme are strongly directed to sites identified by using this computational approach. This method can be used to predict positions where mutations are likely to lead to improvement of specific protein properties.
Resumo:
In this work we review the basic principles of the theory of the relativistic bosonic string through the study of the action functionals of Nambu-Goto and Polyakov and the techniques required for their canonical, light-cone, and path-integral quantisation. For this purpose, we briefly review the main properties of the gauge symmetries and conformal field theory involved in the techniques studied.
Resumo:
In this contribution the line flow method is applied to an optimized secondary optics in a photovoltaic concentration system where the primary optics is already defined and characterized. This method is a particular application of photic field theory. This method uses the parameterization of a given primary optics, including actual tolerances of the manufacturing process. The design of the secondary optics is constrained by the selection of primary optics and maximizes the concentration at a previously specified collection area. The geometry of the secondary element is calculated by using a virtual source, which sends light in a first concentration step. This allows us to calculate the line flow for this specific case. This concept allows designing more compact and efficient secondary optics of photovoltaic systems.
Resumo:
Esta pesquisa investiga o contexto social do desenvolvimento da produção científica contábil brasileira, defendendo a tese de que os agentes, no decorrer do processo de divulgação de suas investigações, estão priorizando aspectos produtivistas e quantitativos e, consequentemente, deixando em segundo plano a preocupação qualitativa e epistemológica [vigilância crítica] de tal produção. Fundamentado na Teoria de Campos de Pierre Bourdieu, este estudo busca relacionar a socialização acadêmica, o habitus dos agentes imbricados no campo, a distribuição do capital científico na área contábil e as características epistemológicas das publicações científicas da área, para obtenção das evidências sobre a problemática levantada. Trata-se de um levantamento operacionalizado por meio de entrevista semiestruturada, com uma amostra de 9 respondentes e estudo documental, com uma amostra de 43 artigos. Os dados foram analisados com emprego da técnica de análise de conteúdo. Apoiando-se em Bourdieu (2004, 2008, 2009, 2011, 2013) foram encontradas evidências de que as teorias, conceitos, metodologias, técnicas e demais escolhas realizadas pelos pesquisadores da área contábil, na maioria das vezes, não passam de manobras estratégicas que visam conquistar, reforçar, assegurar ou derrubar o monopólio da autoridade científica, visando a obtenção de maior poder simbólico no campo. Com relação ao habitus dos agentes pertencentes ao campo científico contábil, constatou-se uma tendência ao produtivismo em consequência das determinações dos órgãos reguladores da pesquisa em contabilidade (CAPES) e das lutas simbólicas travadas no campo para obtenção da autoridade científica. No tocante à socialização acadêmica, reforçou-se a presença de condutas produtivistas, por meio dos programas de pós-graduação stricto sensu, que repassam aos agentes as regras do jogo científico, doutrinando-os na maneira de publicar grande quantidade de comunicações em pouco tempo e com menos custos. As análises epistemológicas puderam triangular os dois últimos constructos, a fim de lhes dar validade, e evidenciaram uma preferência por temáticas que envolvem a contabilidade destinada aos usuários externos e procedimentos contábeis destinados ao mercado financeiro, privilegiando a utilização de dados secundários, por meio de pesquisas documentais. Em termos metodológicos, constatou-se a presença unânime de estudos positivistas, com alguns aspectos empiristas, mostrando uma ausência de inovação em termos de pesquisas norteadas por abordagens metodológicas alternativas e utilização de modelos econométricos para explicar a realidade observada sem teoria para embasar e explicar esses modelos. Por fim, a distribuição do capital simbólico no campo, mostrou que individualmente nenhum agente desponta com maior capital científico, mas, institucionalmente, a FEA/USP ocupa essa posição de destaque. Por conseguinte, pôde-se concluir que o campo científico contábil permanece estagnado e sem grandes modificações teóricas, pelo fato do produtivismo e das lutas simbólicas no interior do campo; fatos esses que, de certa maneira, motivaram a criação de uma espécie de \"receita mágica para publicar\" ou \"formato ideal\" legitimado, institucionalizado e difícil de ser modificado, a não ser que ocorra uma revolução científica que mude o paradigma existente