3,673 research outputs found
Damping Rate of a Yukawa Fermion at Finite Temperature
The damping of a massless fermion coupled to a massless scalar particle at
finite temperature is considered using the Braaten-Pisarski resummation
technique. First the hard thermal loop diagrams of this theory are extracted
and effective Green's functions are constructed. Using these effective Green's
functions the damping rate of a soft Yukawa fermion is calculated. This rate
provides the most simple example for the damping of a soft particle. To leading
order it is proportional to , whereas the one of a hard fermion is of
higher order.Comment: 5 pages, REVTEX, postscript figures appended, UGI-94-0
Equilibrium and Non-Equilibrium Hard Thermal Loop Resummation in the Real Time Formalism
We investigate the use of the hard thermal loop (HTL) resummation technique
in non-equilibrium field theory. We use the Keldysh representation of the real
time formalism (RTF). We derive the HTL photon self energy and the resummed
photon propagator. We show that no pinch singularities appear in the
non-equilibrium HTL effective propagator. We discuss a possible regularization
mechanism for these singularities at higher orders. As an example of the
application of the HTL resummation method within the RTF we discuss the damping
rate of a hard electron.Comment: 23 pages, REVTEX, 5 PostScript figures, revised version to be
published in Eur. Phys. J.
Ward Identities in Non-equilibrium QED
We verify the QED Ward identity for the two- and three -point functions at
non-equilibrium in the HTL limit. We use the Keldysh formalism of real time
finite temperature field theory. We obtain an identity of the same form as the
Ward identity for a set of one loop self-energy and one loop three-point vertex
diagrams which are constructed from HTL effective propagators and vertices.Comment: 19 pages, RevTex, 4 PostScript figures, revised version to be
published in Phys. Rev.
Damping Rate of a Hard Photon in a Relativistic Plasma
The damping rate of a hard photon in a hot relativistic QED and QCD plasma is
calculated using the resummation technique by Braaten and Pisarski.Comment: 4 pages, REVTeX, 2 figures (not included), UGI-MT-94-0
Collisional Energy Loss of Fast Charged Particles in Relativistic Plasmas
Following an argument by Kirzhnits we rederive an exact expression for the
energy loss of a fast charged particle in a relativistic plasma using the
quantum field theoretical language. We compare this result to perturbative
calculations of the collisional energy loss of an energetic electron or muon in
an electron-positron plasma and of an energetic parton in the quark-gluon
plasma.Comment: 9 pages, LATEX, 2 PostScript figure
What can we learn from electromagnetic plasmas about the quark-gluon plasma?
Ultra-relativistic electromagnetic plasmas can be used for improving our
understanding of the quark-gluon plasma. In the weakly coupled regime both
plasmas can be described by transport theoretical and quantum field theoretical
methods leading to similar results for the plasma properties (dielectric
tensor, dispersion relations, plasma frequency, Debye screening, transport
coefficients, damping and particle production rates). In particular, future
experiments with ultra-relativistic electron-positron plasmas in ultra-strong
laser fields might open the possibility to test these predictions, e.g. the
existence of a new fermionic plasma wave (plasmino). In the strongly coupled
regime electromagnetic plasmas such as complex plasmas can be used as models or
at least analogies for the quark-gluon plasma possibly produced in relativistic
heavy-ion experiments. For example, pair correlation functions can be used to
investigate the equation of state and cross section enhancement for parton
scattering can be explained.Comment: 8 pages, 7 figures, talk given at the SCCS 2008 International
Conference, 29 July - 2 August 2008, Camerino, Ital
Practices and Processes of Leading High Performance Home Builders in the Upper Midwest
The NorthernSTAR Building America Partnership team proposed this study to gain insight into the business, sales, and construction processes of successful high performance builders. The knowledge gained by understanding the high performance strategies used by individual builders, as well as the process each followed to move from traditional builder to high performance builder, will be beneficial in proposing more in-depth research to yield specific action items to assist the industry at large transform to high performance new home construction. This investigation identified the best practices of three successful high performance builders in the upper Midwest. In-depth field analysis of the performance levels of their homes, their business models, and their strategies for market acceptance were explored. All three builders commonly seek ENERGY STAR certification on their homes and implement strategies that would allow them to meet the requirements for the Building America Builders Challenge program. Their desire for continuous improvement, willingness to seek outside assistance, and ambition to be leaders in their field are common themes. Problem solving to overcome challenges was accepted as part of doing business. It was concluded that crossing the gap from code-based building to high performance based building was a natural evolution for these leading builders
Photon-Photon Interaction in a Photon Gas
Using the effective Lagrangian for the low energy photon-photon interaction
the lowest order photon self energy at finite temperature and in
non-equilibrium is calculated within the real time formalism. The Debye mass,
the dispersion relation, the dielectric tensor, and the velocity of light
following from the photon self energy are discussed. As an application we
consider the interaction of photons with the cosmic microwave background
radiation.Comment: REVTEX, 7 pages, 1 PostSrcipt figur
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