= Conformal anomaly
{wiki=Conformal_anomaly}
The conformal anomaly, also known as the trace anomaly, is a phenomenon that occurs in certain quantum field theories (QFT) when a theory that is classically conformally invariant loses this symmetry at the quantum level. In simpler terms, while a classical theory may display conformal invariance under scale transformations (where distances are scaled by some factor without changing the shape), quantum effects can introduce terms that break this invariance.
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