91 research outputs found
Universal threshold enhancement
By assuming certain analytic properties of the propagator, it is shown that
universal features of the spectral function including threshold enhancement
arise if a pole describing a particle at high temperature approaches in the
complex energy plane the threshold position of its two-body decay with the
variation of T. The case is considered, when one can disregard any other decay
processes. The quality of the proposed description is demonstrated by comparing
it with the detailed large N solution of the linear sigma model around the
pole-threshold coincidence.Comment: 4 pages, 2 figure
RENORMALISATION GROUP AIDED FINITE TEMPERATURE REDUCTION OF QUANTUM FIELD THEORIES
Dimensional reduction of finite temperature quantum field theories can be
improved with help of continous renormalisation group steps. The method is
applied to the integration of the lowest non-static () modes of the
finite temperature -theory. A second, physically important application
is the integration of the Debye-screened static scalar potential
in the gauged SU(2) Higgs model.Comment: 31 pages, latex, no figure
Non-perturbative construction of counterterms for 2PI-approximation
A concise method is presented for the non-perturbative computation of the
counterterms renormalising 2PI-actions. The procedure is presented for a real
scalar field up to lambda^2 order in the skeleton truncation of Gamma_2PI with
respect to the self-coupling, and in a constant symmetry breaking background.
The method is easily generalizable to field theories with arbitrary global
symmetry.Comment: 4 pages, poster presented at Strong and Electroweak Matter
(SEWM2008), Amsterdam,August 25-29 200
On the evolution of an entangled lepton-neutrino pair
The evolution of the entangled muon-neutrino system emerging from charged
pion decay is explored both in vacuum and in matter. The study is based on a
Weisskopf-Wigner type wave-packet description. Explicit formulae are derived
displaying modulation and attenuation of the oscillations due to additional
time scales characterising the production process. The case of neutrinos
disentangled due to the detection of the muon is also considered
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