The Fundaments of Unity: πͺ(1) Couplings in Quantum Field Theories
Abstract
We critically examine the expectation that in a fundamental quantum field theory, dimensionless couplings in the Lagrangian density should all be of order unity. We propose a measure to quantify the adherence of a theory to this: the spread (the ratio of the largest to the smallest of the magnitudes) of such dimensionless couplings, obtaining various closed-form results. If we take independent and identically distributed (IID) couplings to parameterise our uncertainty on the values of the order-unity couplings, the spread can be much larger than one might naively expect. For a theory with 20 IID unit normal couplings, the probability that the spread is greater than 100 is 0.29, for example. Even when the IID couplings have exponentially suppressed tails, the distribution of the spread has fat power-law tails whose amplitude grows with the number of independent couplings.
Related
- Divergences in Nonpolynomial Quantum Field Theories
- Unitary quantum conformal Bondi-Metzner-Sachs field theories
- Boundary Quantum Knizhnik-Zamolodchikov Equations and Integrability of Quantum Field Theories with Time-Dependent Bulk and Boundary Coupling Strengths
- Time-dependent integrable quantum field theories with dynamical boundaries
- Quasi-Normal Modes and thermalization in integrable Quantum Field Theories from the Thermodynamic Bethe Ansatz
BibTeX
@misc{allanach2026fundaments,
title = {{The Fundaments of Unity: $\mathcal O(1)$ Couplings in Quantum Field Theories}},
author = {Ben Allanach},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.12393},
eprint = {2606.12393},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.12393},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - The Fundaments of Unity: πͺ(1) Couplings in Quantum Field Theories
AU - Ben Allanach
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2606.12393
UR - https://arxiv.org/abs/2606.12393
AB - We critically examine the expectation that in a fundamental quantum field theory, dimensionless couplings in the Lagrangian density should all be of order unity. We propose a measure to quantify the adherence of a theory to this: the spread (the ratio of the largest to the smallest of the magnitudes) of such dimensionless couplings, obtaining various closed-form results. If we take independent and identically distributed (IID) couplings to parameterise our uncertainty on the values of the order-unity couplings, the spread can be much larger than one might naively expect. For a theory with 20 IID unit normal couplings, the probability that the spread is greater than 100 is 0.29, for example. Even when the IID couplings have exponentially suppressed tails, the distribution of the spread has fat power-law tails whose amplitude grows with the number of independent couplings.
ER -