Hot QED beyond ladder graphs

Abstract

At finite temperature a breakdown of the hard thermal loop expansion arises whenever external momenta are light-like or tend to very soft scales. A resummation of ladder graphs is important in these cases where the effects of infrared or light-cone singularities are enhanced. We show that in hot QED another class of diagrams is also relevant at leading order due to long range magnetic interactions and therefore recent studies about ladder expansions need to be corrected. A general cancellation of the hard modes damping effects still occurs near the light-cone or in the infrared region. The validity of an improved version of the hard thermal loop resummation scheme is discussed.