23,681 research outputs found
On the Nonrelativistic Limit of the phi^4 Theory in 2+1 Dimensions
We study the nonrelativistic limit of the quantum theory of a real scalar
field with quartic self-interaction. The two body scattering amplitude is
written in such way as to separate the contributions of high and low energy
intermediary states. From this result and the two loop computation of the self
energy correction, we determine an effective nonrelativistic action.Comment: 15 pages, 2 figures, revte
Radiative Corrections to the Aharonov-Bohm Scattering
We consider the scattering of relativistic electrons from a thin magnetic
flux tube and perturbatively calculate the order , radiative
correction, to the first order Born approximation. We show also that the second
order Born amplitude vanishes, and obtain a finite inclusive cross section for
the one-body scattering which incorporates soft photon bremsstrahlung effects.
Moreover, we determine the radiatively corrected Aharonov-Bohm potential and,
in particular, verify that an induced magnetic field is generated outside of
the flux tube.Comment: 14 pages, revtex, 3 figure
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Sistemas de producción de patata y otras hortalizas: procesos de producción, organización y consumo de productos ecológicos en Andalucía/España.
bitstream/item/43963/1/documento-329.pd
Nonrelativistic Limit of the Scalar Chern-Simons Theory and the Aharonov-Bohm Scattering
We study the nonrelativistic limit of the quantum theory of a Chern-Simons
field minimally coupled to a scalar field with quartic self-interaction. The
renormalization of the relativistic model, in the Coulomb gauge, is discussed.
We employ a procedure to calculate scattering amplitudes for low momenta that
generates their expansion and separates the contributions coming from
high and low energy intermediary states. The two body scattering amplitude is
calculated up to order . It is shown that the existence of a critical
value of the self-interaction parameter for which the 2-particle scattering
amplitude reduces to the Aharonov-Bohm one is a strictly nonrelativistic
feature. The subdominant terms correspond to relativistic corrections to the
Aharonov-Bohm scattering. A nonrelativistic reduction scheme and an effective
nonrelativistic Lagrangian to account for the relativistic corrections are
proposed.Comment: 22 pages, 8 figures, revtex, to be published in Int. J. Mod. Phys.
Influence of the local morphology on the surface tension of injection molded polypropylene
Publicado em “Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”In this work, we investigate the development of the morphology of an injection molding polypropylene under the local
thermomechanical environment imposed during processing, and its effect on the contact angle and, hence, on the surface
tension of the moldings. Melt and mold temperatures were varied in two levels. The local thermomechanical environment was
characterized by mold filling computational simulations that allow the calculation of thermomechanical variables (e.g., local
temperatures, shear stresses) and indices (related to the local morphology development). In order to investigate the structural
hierarchy variations of the moldings in the thickness direction, samples from skin to core were used. The molecular orientation
and degree of crystallinity were determined as function of the thickness, as well as the contact angle. The variations of the
degree of crystallinity were assessed by differential scanning calorimetry. The level of molecular orientation was evaluated by
birefringence measurements. The contact angles were measured in deionized water by sessile drop (needle in) method at room
temperature, to determine the wettability of the samples. The contact angles were found to vary along the molding thickness in
the skin, transition and core layers. These variations are related to the local morphologies developed. Results suggest that water
contact angle increases with the level of molecular orientation and for finer microstructures
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