Relations between Positivity, Localization and Degrees of Freedom: the Weinberg-Witten theorem and the van~Dam-Veltman-Zakharov discontinuity

Resumo

The problem of accounting for the degrees of freedom in passing from
massive spin to massless helicity degrees of freedom and its inverse, the
``fattening'' of massless tensor fields to their massive $s=\left\vert
h\right\vert $ counterparts, are solved using ``string-localized
fields''.

This approach allows to overcome the Weinberg-Witten impediment against the
existence of massless $\left\vert h\right\vert \geq 2$ energy-momentum
tensors, and to replace the van Dam-Veltman-Zakharov discontinuity concerning,
e.g., very light gravitons, by a continuous limit $m\to0$.