40,702 research outputs found
Reversors and Symmetries for Polynomial Automorphisms of the Plane
We obtain normal forms for symmetric and for reversible polynomial
automorphisms (polynomial maps that have polynomial inverses) of the plane. Our
normal forms are based on the generalized \Henon normal form of Friedland and
Milnor. We restrict to the case that the symmetries and reversors are also
polynomial automorphisms. We show that each such reversor has finite-order, and
that for nontrivial, real maps, the reversor has order 2 or 4. The normal forms
are shown to be unique up to finitely many choices. We investigate some of the
dynamical consequences of reversibility, especially for the case that the
reversor is not an involution.Comment: laTeX with 5 figures. Added new sections dealing with symmetries and
an extensive discussion of the reversing symmetry group
Electromagnetic fields and transport coefficients in a hot pion gas
We present recent results on finite temperature electromagnetic form factors
and the electrical conductivity in a pion gas. The standard Chiral Perturbation
Theory power counting needs to be modified for transport coefficients. We pay
special attention to unitarity and to possible applications for dilepton and
photon production.Comment: 4pp, 2 figures, talk given at "Strong and Electroweak Matter 2006",
BNL, May 200
Transport coefficients of a massive pion gas
We review or main results concerning the transport coefficients of a light
meson gas, in particular we focus on the case of a massive pion gas. Leading
order results according to the chiral power-counting are presented for the DC
electrical conductivity, thermal conductivity, shear viscosity, and bulk
viscosity. We also comment on the possible correlation between the bulk
viscosity and the trace anomaly in QCD, as well as the relation between
unitarity and a minimum of the quotient near the phase transition.Comment: Talk given at the 5th International Conference on Quarks and Nuclear
Physics (QNP09), Beijing, September 21-26, 200
Chiral symmetry and mesons in hot and dense matter: recent developments
We review recent results on properties of the meson gas relevant for Heavy
Ion Collision and Nuclear Matter experiments, within the framework of chiral
lagrangians. In particular, we describe the temperature and density evolution
of the and poles and its connection with chiral symmetry
restoration, as well as the chemical nonequilibrated phase and transport
coefficients.Comment: Proceedings of the "Chiral10 International Workshop on Chiral
Symmetry in Hadrons and Nuclei", Valencia, Spain, 21-24 june 2010. 9 pages, 5
figures. AIP Proceedings styl
The hadronic off-shell width of meson resonances
Within the resonance chiral effective theory we study the dressed propagators
of the spin-1 fields, as arise from a Dyson-Schwinger resummation
perturbatively constructed from loop diagrams with absorptive contributions in
the s-channel. We apply the procedure to the vector pion form factor and the
elastic pion-pion scattering to obtain the off-shell width of the rho_0 meson.
We adopt a definition of the off-shell width of spin-1 meson resonances that
satisfies the requirements of analyticity, unitarity, chiral symmetry and
asymptotic behaviour ruled by QCD. To fulfil these constraints the resummation
procedure cannot consist only of self-energy diagrams. Our width definition is
shown to be independent of the formulation used to describe the spin-1 meson
resonances.Comment: 1+12 pages, 4 figures. Minor changes in text. Conclusions unchanged.
Version accepted for publication in Phys. Rev.
Electromagnetic quasinormal modes of five-dimensional topological black holes
We calculate exactly the QNF of the vector type and scalar type
electromagnetic fields propagating on a family of five-dimensional topological
black holes. To get a discrete spectrum of quasinormal frequencies for the
scalar type electromagnetic field we find that it is necessary to change the
boundary condition usually imposed at the asymptotic region. Furthermore for
the vector type electromagnetic field we impose the usual boundary condition at
the asymptotic region and we discuss the existence of unstable quasinormal
modes in the five-dimensional topological black holes.Comment: 16 pages. Already published in Revista Mexicana de Fisic
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