9,007 research outputs found
Effects of gluon number fluctuations on photon - photon collisions at high energies
We investigate the effects of gluon number fluctuations on the total
, cross sections and the photon structure
function . Considering a model which relates the
dipole-dipole and dipole-hadron scattering amplitudes, we estimate these
observables by using event-by-event and physical amplitudes. We demonstrate
that both analyses are able to describe the LEP data, but predict different
behaviours for the observables at high energies, with the gluon fluctuations
effects decreasing the cross sections. We conclude that the study of interactions can be useful to constrain the QCD dynamics.Comment: 9 pages, 6 figures. Improved version with two new figures. Version to
be published in Physical Review
On fermionic tilde conjugation rules and thermal bosonization. Hot and cold thermofields
A generalization of Ojima tilde conjugation rules is suggested, which reveals
the coherent state properties of thermal vacuum state and is useful for the
thermofield bosonization. The notion of hot and cold thermofields is introduced
to distinguish different thermofield representations giving the correct normal
form of thermofield solution for finite temperature Thirring model with correct
renormalization and anticommutation properties.Comment: 13 page
Genital Tuberculosis: a Rare Cause of Postmenopausal Bleeding
Introdução: A tuberculose continua um problema de saúde pública emergente. A incidência da tuberculose genito-urinária tem vindo a aumentar sendo o segundo local mais comum de infecção a seguir aos pulmões.
Caso clínico: Os autores apresentam dois casos de mulheres com hemorragia vaginal
pós-menopausa. O exame clínico não revelou alterações. A ecografia pélvica endocavitária
detectou a presença de uma lâmina líquida na cavidade endometrial em ambos os casos.
A histeroscopia identificou espessamentos focais do endométrio que foram biopsados. O
exame anatomopatológico revelou granulomas de células epitelióides sem atipia celular.
O exame cultural do endométrio foi positivo para Mycobacterium tuberculosis. Não foi
detectado envolvimento de outros órgãos tendo as doentes iniciado terapêutica antibacilar.
Conclusão: A tuberculose genital é rara na mulher pós-menopausa sendo responsável
por cerca de 1% da hemorragia vaginal pós-menopausa. No entanto, é uma doença curável
cujo diagnóstico precoce é importante, prevenindo a utilização de procedimentos invasivos desnecessários
cross section from the dipole model in momentum space
We reproduce the DIS measurements of the proton structure function at high
energy from the dipole model in momentum space. To model the dipole-proton
forward scattering amplitude, we use the knowledge of asymptotic solutions of
the Balitsky-Kovchegov equation, describing high-energy QCD in the presence of
saturation effects. We compare our results with the previous analysis in
coordinate space and discuss possible extensions of our approach.Comment: 9 pages, 3 figure
Experimental determination of the non-extensive entropic parameter
We show how to extract the parameter from experimental data, considering
an inhomogeneous magnetic system composed by many Maxwell-Boltzmann homogeneous
parts, which after integration over the whole system recover the Tsallis
non-extensivity. Analyzing the cluster distribution of
LaSrMnO manganite, obtained through scanning tunnelling
spectroscopy, we measure the parameter and predict the bulk magnetization
with good accuracy. The connection between the Griffiths phase and
non-extensivity is also considered. We conclude that the entropic parameter
embodies information about the dynamics, the key role to describe complex
systems.Comment: Submitted to Phys. Rev. Let
Vortex core size in interacting cylindrical nanodot arrays
The effect of dipolar interactions among cylindrical nanodots, with a
vortex-core magnetic configuration, is analyzed by means of analytical
calculations. The cylinders are placed in a N x N square array in two
configurations - core oriented parallel to each other and with antiparallel
alignment between nearest neighbors. Results comprise the variation in the core
radius with the number of interacting dots, the distance between them and dot
height. The dipolar interdot coupling leads to a decrease (increase) of the
core radius for parallel (antiparallel) arrays
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