@misc{10481/110582,
year = {2026},
month = {2},
url = {https://hdl.handle.net/10481/110582},
abstract = {Within density functional theory (DFT), where the density is the fundamental vari
able, quantum phase transitions (QPTs) can be formulated through a Hamiltonian
H = ˆH0+∑iξi ˆAi, such that the control parameters {ξi} are in bijective correspondence (in
the nondegenerate case) with the “densities” ai = ⟨ ˆAi⟩, and the functional Q({ai}) acts as
the Legendre transform of the energy; this structure even permits the use of Rényi entropy
(for a given order) as an alternative control parameter, while degeneracy can be handled via
a subspace density. On this foundation, information-theoretic measures provide sensitive
diagnostics of criticality: fidelity and its susceptibility χ, Fisher information, relative Rényi
entropy, and the Kullback–Leibler divergence are locally linked by Rq≈ q IKL≈ 2qχ(δλ)2,
revealing their proportionality in the small-parameter-shift regime. Applied to the Dicke
model, numerical analyses show that fidelity exhibits pronounced curvature or divergence
near λc = √
ωω0/2 and that the response sharpens with increasing j, corroborating that
these information measures capture QPTs with precision within the DFT framework.},
publisher = {MDPI},
keywords = {Density functional theory},
keywords = {Quantum phase transitions},
keywords = {Rényi entropy},
title = {Density Functional Theory and Information-Theoretic Diagnostics of Quantum Phase Transitions},
doi = {10.3390/e28020170},
author = {Romera Gutiérrez, Elvira and Nagy, Agnes},
}