16 research outputs found
Nonequilibrium perturbation theory for spin-1/2 fields
A partial resummation of perturbation theory is described for field theories
containing spin-1/2 particles in states that may be far from thermal
equilibrium. This allows the nonequilibrium state to be characterized in terms
of quasiparticles that approximate its true elementary excitations. In
particular, the quasiparticles have dispersion relations that differ from those
of free particles, finite thermal widths and occupation numbers which, in
contrast to those of standard perturbation theory evolve with the changing
nonequilibrium environment. A description of this kind is essential for
estimating the evolution of the system over extended periods of time. In
contrast to the corresponding description of scalar particles, the structure of
nonequilibrium fermion propagators exhibits features which have no counterpart
in the equilibrium theory.Comment: 16 pages; no figures; submitted to Phys. Rev.
Classical Fields Near Thermal Equilibrium
We discuss the classical limit for the long-distance (``soft'') modes of a
quantum field when the hard modes of the field are in thermal equilibrium. We
address the question of the correct semiclassical dynamics when a momentum
cut-off is introduced. Higher order contributions leads to a stochastic
interpretation for the effective action in analogy to Quantum Brownian Motion,
resulting in dissipation and decoherence for the evolution of the soft modes.
Particular emphasis is put on the understanding of dissipation. Our discussion
focuses mostly on scalar fields, but we make some remarks on the extension to
gauge theories.Comment: REVTeX, 6 figure
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Shorter contributions to general geology
From introduction: This report deals with the stratigraphic and ecologic significance of Foraminifera contained in a Tertiary sequence that crops out in the northern part of the Olympic Peninsula, Wash. (pl. 1). The work was done as a part of a program of geologic investigations for oil and gas possibilities conducted by the U.S. Geological Survey
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The Ore bin ; Vol. 31 No. 3 (March 1969)
This field trip consists of two geologic tours. On Tour 1, the Tertiary sedimentary rocks exposed along the Yaquina River between Newport and Toledo, Oregon, will be examined. This tour will start at the mouth of Yaquina Bay where Miocene sedimentary rocks are exposed and will proceed generally eastward and downsection. Tour 2 is primarily concerned with volcanic rocks of early Eocene, late Eocene, and middle Miocene age that form important stratigraphic units in the Oregon Coast Range