Why dimensional analysis works: general classification of self-similarity based on scale-invariance
Abstract
In this work, we formulate self-similarity from the perspective of scale invariance, where a self-similar form is understood as the transformation of a function into a form invariant under scale transformations. By applying this formulation to physical parameters, which consist of numerical values and units, it is demonstrated that dimensional analysis works for physical problems because scale invariance is partially shared between units and physical parameters. This naturally leads to the distinction between similarity of the first kind and similarity of the second kind according to whether the scale functions induced by units and those associated with physical parameters are equivalent or not. Self-similar solutions of the second kind can be further classified according to whether the power exponents of the similarity parameters include functions of dimensionless numbers. This leads to the conclusion that there are three kinds of self-similar solutions. The present work provides a unified framework for understanding dimensional analysis and a universal classification of self-similarity in physical problems.
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BibTeX
@misc{maruoka2026dimensional,
title = {{Why dimensional analysis works: general classification of self-similarity based on scale-invariance}},
author = {Hirokazu Maruoka},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2606.17179},
eprint = {2606.17179},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.17179},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Why dimensional analysis works: general classification of self-similarity based on scale-invariance
AU - Hirokazu Maruoka
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2606.17179
UR - https://arxiv.org/abs/2606.17179
AB - In this work, we formulate self-similarity from the perspective of scale invariance, where a self-similar form is understood as the transformation of a function into a form invariant under scale transformations. By applying this formulation to physical parameters, which consist of numerical values and units, it is demonstrated that dimensional analysis works for physical problems because scale invariance is partially shared between units and physical parameters. This naturally leads to the distinction between similarity of the first kind and similarity of the second kind according to whether the scale functions induced by units and those associated with physical parameters are equivalent or not. Self-similar solutions of the second kind can be further classified according to whether the power exponents of the similarity parameters include functions of dimensionless numbers. This leads to the conclusion that there are three kinds of self-similar solutions. The present work provides a unified framework for understanding dimensional analysis and a universal classification of self-similarity in physical problems.
ER -