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Revisiting 5D chiral symmetry breaking and holographic QCD models
We take a closer look at the recently discussed models of hadrons based on
holographic ideas and chiral symmetry breaking in five dimensions. We study the
two point correlator in detail and look at the field theoretic properties
needed to be satisfied by the correlator. It is shown that the spectral density
becomes negative, violating the basic requirements for the Kallen-Lehmann
representation. We briefly discuss the implications of this violation of the
positivity of the spectral density and also discuss possible origin of such a
violation in these models. Put simply this means that such models are not
physical descriptions of the hadron spectrum.Comment: Latex, 9 pages including 6eps figures. More discussion added and
minor rewording done. To appear in PL
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