#### Alladi Ramakrishnan Hall

#### Phases of Non-Abelian Gauge Theories

#### A.P. Balachandran

##### IMSc

*The phases of non-abelian gauge theories like QCD are classified according to a_0,*

the asymptotic value of the time component A_0 of the vector potential. The gauge group G is unbroken if a_0 is zero as is normally assumed. In this talk, we argue however that there are cases where it is not zero, as when gauge transformations with non-trivial winding numbers are considered. Such gauge transformations are important for Polyakov loops in finite temperature field theories. When a_0 is not zero, G is broken to the stability group H of a_0. H is U(1)xU(1) or U(2) in QCD. The gauge fields in the spontaneously broken directions are also shown to acquire mass by a novel variant of the Higgs mechanism.

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