# Positivity and causal localizability in higher spin quantum field theories. (arXiv:1712.02346v2 [math-ph] CROSS LISTED)

The relation between massive and massless vector (tensor) potentials is

reviewed in the light of recent progress concerning the connection between

positivity-preserving renormalizable interactions and a weakening of causal

localization. The resulting string-(or ray-) localized free fields extend the

smooth passage between massive 2-point functions and their massless helicity

counterparts to any spin and resolves problems of degrees of freedom counting

which have their origin in the gauge theoretic presence of unphysical degrees

of freedom. The so extended local quantum physics has its strongest impact on

interacting theories. The use of a short distance-improving string-local "field

coordinatization" allows a subtle separation of short-distance singular terms

which can be disposed in the adiabatic limit, and a short distance-improved

part which accounts for the physics. Unlike the standard setting of

perturbation theory it avoids the use of any parallelism to classical field

theories as Lagrangian quantization (Jordan's "without classical crutches") in

favor of concepts which are intrinsic to QFT. It leads to a significant

extension of QFT which includes a more foundational understanding of the role

of the Higgs particle and fibre bundle like structures of selfinteracting

higher spin fields as consequences of the positivity-preserving causal

localization principles of QFT.