Searches for P- and T-violating permanent electric dipole moments

A permanent electric dipole moment (EDM) of a particle or system is a measure of the separation of charge along its angular momentum axis and is a direct signal of both parity ($P$) violation & time-reversal ($T$) violation and, assuming $CPT$-symmetry, charge-parity ($CP$) violation. For nearly 70 years EDMs have been studied, first as a signal of a $P$-violation and then as a signal of $CP$-violation. Contemporary motivations include the role that $CP$-violation plays in explaining the cosmological matter-antimatter asymmetry and the search for new physics. Experiments on a variety of systems have become ever-more sensitive, but provide only upper limits on EDMs, and theory at several scales is crucial to interpret these limits. In this talk, I will provide an overview of EDM experiments in atom and molecules in both the paramagnetic and diamagnetic sectors.