13,187 research outputs found
Numerical Quantum Field Theory on the Continuum and a New Look at Perturbation Theory
The Source Galerkin method finds approximate solutions to the functional
differential equations of field theories in the presence of external sources.
While developing this process, it was recognized that approximations of the
spectral representations of the Green's functions by Sinc function expansions
are an extremely powerful calculative tool. Specifically, this understanding
makes it not only possible to apply the Source Galerkin method to higher
dimensional field theories, but also leads to a new approach to perturbation
theory calculations in scalar and fermionic field theories. This report
summarizes the methodologies for solving quantum field theories with the Source
Galerkin method and for performing perturbation theory calculations using Sinc
approximations.Comment: Lattice2001(theorydevelop
Coupling between internal spin dynamics and external degrees of freedom in the presence of colored noise
We observe asymmetric transition rates between Zeeman levels (spin-flips) of
magnetically trapped atoms. The asymmetry strongly depends on the spectral
shape of an applied noise. This effect follows from the interplay between the
internal states of the atoms and their external degrees of freedom, where
different trapped levels experience different potentials. Such insight may
prove useful for controlling atomic states by the introduction of noise, as
well as provide a better understanding of the effect of noise on the coherent
operation of quantum systems.Comment: 5 pages, 4 figures; accepted to PR
On the duality in CPT-even Lorentz-breaking theories
In this paper, we generalize the duality between self-dual and
Maxwell-Chern-Simons theories for the case of a CPT-even Lorentz-breaking
extension of these theories. The duality is demonstrated with use of the gauge
embedding procedure, both in free and coupled cases, and with the master action
approach. The physical spectra of both Lorentz-breaking theories are studied.
The massive poles are shown to coincide and to respect the requirements for
unitarity and causality at tree level. The extra massless poles which are
present in the dualized model are shown to be nondynamical.Comment: 17 pages, version accepted to EPJ
Energy Dissipation in Fractal-Forced Flow
The rate of energy dissipation in solutions of the body-forced 3-d
incompressible Navier-Stokes equations is rigorously estimated with a focus on
its dependence on the nature of the driving force. For square integrable body
forces the high Reynolds number (low viscosity) upper bound on the dissipation
is independent of the viscosity, consistent with the existence of a
conventional turbulent energy cascade. On the other hand when the body force is
not square integrable, i.e., when the Fourier spectrum of the force decays
sufficiently slowly at high wavenumbers, there is significant direct driving at
a broad range of spatial scales. Then the upper limit for the dissipation rate
may diverge at high Reynolds numbers, consistent with recent experimental and
computational studies of "fractal-forced'' turbulence.Comment: 14 page
OIM analysis of microstructure and texture of a TRIP assisted steel after static and dynamic deformation
TRIP-assisted steel with a composition of 0.2%C, 1.6%Mn, 1.5%Al was studied in the undeformed state, after the application of 10 and 30 % static tensile strain parallel to rolling the direction of the sheet and after dynamic (Hopkinson) fracture test. Detailed examination of the microstructure and microtexture by means of electron backscattered diffraction (EBSD) was carried out in order to quantify the microstructural constituents and to study the strain distribution. The microtexture evolution and the distribution of the specific texture components between the BCC and FCC phases were studied as a function of the external strain and the strain mode-static or dynamic. The strain localization and strain distribution between the structural constituents were quantified based on local misorientation maps. The full constraint Taylor model was used to predict the texture changes in the material and the results were compared to the experimental findings. Comparing the local misorientation data it was found that at low strains the ferrite accommodates approximately 10 times more deformation than the retained austenite. The strain localizes initially on the BCC-FCC phase boundaries and is then spread in the BCC constituents (ferrite and bainite) creating a deformation skeleton in the BCC phase.
It was found that the observed texture changes in the measured retained austenite texture after deformation do not correspond exactly to the model prediction. The austenite texture components which were predicted by the Taylor model were not found in the measured austenite texture after deformation which means that they are first transformed to martensite, which is considered as an indication for the selective transformation of austenite under strain
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