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# Artificial dynamical effects in quantum field theory

## Abstract

In Newtonian mechanics, studying a system in a non-Galilean reference frame can lead to inertial pseudoforces appearing, such as the centrifugal force that seems to arise in dynamics analysed in a rotating frame. Likewise, artificial effects may arise in relativistic quantum field theory (QFT) if a system is studied in a framework that violates Poincaré invariance. In this Perspective, we highlight how such issues complicate the traditional canonical quantization of QFTs and can lead to a subjective description of natural phenomena. By contrast, the treatment of the same problem using light-front quantization is free from spurious pseudoeffects because Poincaré invariance is effectively preserved for all practical intents and purposes. We illustrate these statements using several examples: the Gerasimov–Drell–Hearn (GDH) relation, a fundamental feature of QFT; the absence of any measurable impact of Lorentz contraction in high-energy collisions; and the fictitious character of vacuum fluctuation contributions to the cosmological constant.

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## Acknowledgements

This work is supported by the US Department of Energy, contract DE-AC02-76SF00515 (S.J.B.); the US Department of Energy, Office of Science, Office of Nuclear Physics, contract DE-AC05-06OR23177 (A.D.); and the National Natural Science Foundation of China, grant no. 12135007 (C.D.R.).

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Correspondence to Stanley J. Brodsky, Alexandre Deur or Craig D. Roberts.

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Brodsky, S.J., Deur, A. & Roberts, C.D. Artificial dynamical effects in quantum field theory. Nat Rev Phys 4, 489–495 (2022). https://doi.org/10.1038/s42254-022-00453-3

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