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Why do we "normal-order" instead of just subtracting off vacuum energy?

A normal ordered operatpr has finite matrix elements between any pair of states. Subtracting a constant only gurantees you a finite number for the diagonal matrix element between one specific state ...
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Quantum Fields living in finite dimensional non-unitary irreducible representations of the Lorentz group

The finite-dimensional representation is on the target space of the classical fields, not on the space of fields itself. Of course, the "target space" of an operator-valued distribution is a ...
• 107k

Questions on RG flows, CFTs, and UV and IR theories

The theory with characteristic length $R_\text{c}=0$ is the UV CFT, since it is probing things at the smallest possible length scale, i.e. at the largest possible energy. In other words, its ...
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