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    Scattering amplitude and shift in self-energy in medium

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    Two simple proofs are presented for the first order virial expansion of the self-energy of a particle moving through a medium, characterised by temperature and/or chemical potential(s). One is based on the virial expansion of the self-energy operator itself, while the other is on the analysis of its Feynman diagrams in configuration space.Comment: 6 pages, revtex, with 1 eps figur

    Current algebra derivation of temperature dependence of hadron couplings with currents

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    The vector and the axial-vector meson couplings with the vector and the axial-vector currents respectively at finite temperature have been obtained in Ref. \cite{Mallik} by calculating all the relevant one-loop Feynman graphs with vertices obtained from the effective chiral Lagrangian. On the other hand, the same couplings were also derived in Ref.\cite{Ioffe1} by applying the method of current algebra and the hypothesis of partial conservation of axial-vector current (PCAC). The latter method appears to miss certain terms; in the case of the vector meson coupling with the vector current, for example, a term containing the ρωπ\rho\omega\pi coupling is missed. A similar situation would also appear for the nucleon coupling with the nucleon current. In this note we resolve these differences.Comment: 7 pages, 2 eps figure
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