  Three topics, the self-consistent resummation of the perturbative expansion
for thermal Yang-Mills (YM) theory, nonperturbative analysis of Yang-Mills
theories in (2+1) dimensions and modification of the Bose distribution for
gluons, are discussed. These topics are related to the magnetic mass or
magnetic screening in the quark-gluon plasma. The value of the magnetic mass is
argued to be close to $e^2N/2\pi=g^2TN/2\pi$ for an SU(N) gauge theory. An
analytic calculation of the string tension for $YM_{2+1}$, which agrees with
numerical simulations to within 3%, is another result.
