Quantum energy inequalities and local covariance

Except for a few special cases, quantum energy inequalities proved to date have constrained stress-energy tensors 'normal-ordered' with respect to a reference state, sometimes called 'difference quantum inequalities'. The reliance on a reference state is problematic, because one does not have access to, e.g., the two-point function of a suitable reference state in a generic curved spacetime background. In this talk, based on work with Calvin Smith (York), I will present a general derivation of an absolute quantum energy inequality, which does not appeal to a reference state at any stage, and is manifestly locally covariant. I will also describe other connections between quantum energy inequalities and local covariance, based on work with Mitch Pfenning (West Point).