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

BICEP2, non Bunch-Davies and Entanglement

BICEP2 result on the tensor to scalar ratio $r$ indicates a blue tilt in the primordial gravitational wave spectrum. This blue tilt and the observed large value $r = 0.2$ are difficult to accommodate within the single field inflationary scenarios under standard conditions. Non Bunch-Davies vacuum states have been proposed as a possibility. Such vacuua are known to lead to pathologies. In this note we propose to interpret them as excited/squeezed states built over the standard Bunch-Davies vacuum and discuss the associated entanglement properties due to de Sitter horizon, and how such an approach may be more natural in the context of inflation.Comment: 5 page