71 research outputs found
Do many-particle neutrino interactions cause a novel coherent effect?
We investigate whether coherent flavor conversion of neutrinos in a neutrino
background is substantially modified by many-body effects, with respect to the
conventional one-particle effective description. We study the evolution of a
system of interacting neutrino plane waves in a box. Using its equivalence to a
system of spins, we determine the character of its behavior completely
analytically. We find that, if the neutrinos are initially in flavor
eigenstates, no coherent flavor conversion is realized, in agreement with the
effective one-particle description. This result does not depend on the size of
the neutrino wavepackets and therefore has a general character. The validity of
the several important applications of the one-particle formalism is thus
confirmed.Comment: 25 pages, 1 figur
Numerical Study of High-Temperature Jet Flow Using RANS/LES and PANS Formulations
Two multi-scale-type turbulence models are implemented in the PAB3D solver. The models are based on modifying the Reynolds Averaged Navier-Stokes (RANS) equations. The first scheme is a hybrid RANS/LES model utilizing the two-equation (k(epsilon)) model with a RANS/LES transition function dependent on grid spacing and the computed turbulence length scale. The second scheme is a modified version of the Partially Averaged Navier-Stokes (PANS) model, where the unresolved kinetic energy parameter (f(sub k)) is allowed to vary as a function of grid spacing and the turbulence length scale. This parameter is estimated based on a novel two-stage procedure to efficiently estimate the level of scale resolution possible for a given flow on a given grid for Partial Averaged Navier-Stokes (PANS). It has been found that the prescribed scale resolution can play a major role in obtaining accurate flow solutions. The parameter f(sub k) varies between zero and one and equal to one in the viscous sub layer, and when the RANS turbulent viscosity becomes smaller than the LES viscosity. The formulation, usage methodology, and validation examples are presented to demonstrate the enhancement of PAB3D's time-accurate and turbulence modeling capabilities. The accurate simulations of flow and turbulent quantities will provide valuable tool for accurate jet noise predictions. Solutions from these models are compared to RANS results and experimental data for high-temperature jet flows. The current results show promise for the capability of hybrid RANS/LES and PANS in simulating such flow phenomena
Non-Linear Integral Equations for complex Affine Toda associated to simply laced Lie algebras
A set of coupled non-linear integral equations is derived for a class of
models connected with the quantum group ( simply laced Lie
algebra), which are solvable using the Bethe Ansatz; these equations describe
arbitrary excited states of a system with finite spatial length . They
generalize the Destri-De Vega equation for the Sine-Gordon/massive Thirring
model to affine Toda field theory with imaginary coupling constant. As an
application, the central charge and all the conformal weights of the UV
conformal field theory are extracted in a straightforward manner. The quantum
group truncation for at a root of unity is discussed in detail; in the UV
limit we recover through this procedure the RCFTs with extended
conformal symmetry.Comment: 33 pages, TeX with lanlmac (revised: minor misprints corrected, some
comments added, appendix slightly expanded revised 05/98: more misprints
corrected, important refs added
Looking Forward to Looking Backward: A Dossier of Writings on Architecture from the 1930s
Natural Attenuation Strategy for Groundwater Cleanup Focuses on Demonstrating Cause and Effect
this article reviews the results of two USGS Toxics Program case studies in the context of the NRC committee's recommendations. This is followed by a discussion of the emerging research issues for natural attenuation processe
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