Discrete symmetries — charge conjugation (C), parity inversion (P), time reversal (T), and their combinations — provide insight into the structure of our physical theories. Many extensions to the Standard Model predict symmetry violations beyond those already known. From the first evidence of P-violation in the 1950s using cold atoms, low-energy, high-precision experiments have quantified existing violations and constrained further ones. In this lecture, I will describe several searches for discrete symmetry violations with low-energy experiments. T-violation, closely related to matter/antimatter asymmetry through the CPT theorem, is tightly constrained by searches for intrinsic electric dipole moments. CPT-violation — the only combination of these symmetries obeyed by the entire Standard Model — is constrained in leptons by comparisons of the electron to the positron and in baryons by comparisons of the proton to the antiproton. Ongoing work with antihydrogen aims to further constrain CPT-violation in both these sectors.
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