We study the empirical realization of the memory effect in Yang-Mills theory, especially in view of the classical vs quantum nature of the theory. Gauge invariant analysis of memory in classical U ( 1 ) electrodynamics and its observation by total change of transverse momentum of a charge is reviewed. Gauge fixing leads to a determination of a gauge transformation at infinity. An example of Yang-Mills memory then is obtained by reinterpreting known results on interactions of a quark and a large high energy nucleus in the theory of color glass condensate. The memory signal is again a kick in transverse momentum, but it is only obtained in quantum theory after fixing the gauge, after summing over an ensemble of classical processes.
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