On the Reduction Structure of Effective Theories
Masaru Moriyama
This technical note compares the Q-box formalism of nuclear physics with density functional theory (DFT) of quantum chemistry and condensed matter physics, from a renormalization group (RG) perspective. Although the two theories developed independently, both share the methodological philosophy of eliminating intractable degrees of freedom to obtain a lower-dimensional effective description. This note formalizes that intuition, arguing that both belong to a Shared Methodological Lineage rooted in Wilsonian effective theory and stand in a Structural Analogy, traversing symmetric yet distinct paths in reduction axis and mathematical foundation. Key contents:- Formal juxtaposition of reduction operations: energy-scale reduction (Q-box) vs. spatial-dimension reduction (DFT)- Unified abstract structure as reduction maps R : X -> Y, with explicit asymmetry between R_Q (non-invertible, approximation-dependent) and R_D (invertible in principle via the Hohenberg-Kohn theorem)- Mathematical depth of DFT: Levy constrained search, Legendre transform isomorphism with the 1PI effective action, existence and unknowability of the universal functional- Genealogical comparison with Wilson RG, SRG (Wegner 1994; Glazek-Wilson 1993), DMRG (White 1992), and the 1PI effective action
•May 21, 2026•0 citations