PreprintCC BY-NC-ND 4.0arXiv
Exact Integration and Invertibility Completeness of the Nonlinear Relaxation Equation
Abstract
We examine the nonlinear initial value problem ẏ = C(1 − yα) modeling polytropic gas permeation. For rational α, we derive the exact primitive via cyclotomic partial fraction decomposition, establishing its real trigonometric representation. By synthesizing Ritt's theorem with Rosenlicht's differential algebraic residue criterion, we prove the exact step response y(t) is an elementary function if and only if α∈ {1, 2}. Admitting the Lambert W function extends closed-form solvability strictly to α∈ {−1, 1/2}. Finally, the asymptotic limit α→ 0 converges to a singular dynamics solved by the logarithmic integral. These results constitute a complete classification of all explicit closed-form solutions admitted by this system.
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BibTeX
@misc{mrazik2026exact,
title = {{Exact Integration and Invertibility Completeness of the Nonlinear Relaxation Equation}},
author = {Lukáš Mrazík},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.31748},
eprint = {2609.31748},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.31748},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Exact Integration and Invertibility Completeness of the Nonlinear Relaxation Equation
AU - Lukáš Mrazík
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.31748
UR - https://arxiv.org/abs/2609.31748
AB - We examine the nonlinear initial value problem ẏ = C(1 − y^α) modeling polytropic gas permeation. For rational α, we derive the exact primitive via cyclotomic partial fraction decomposition, establishing its real trigonometric representation. By synthesizing Ritt's theorem with Rosenlicht's differential algebraic residue criterion, we prove the exact step response y(t) is an elementary function if and only if α∈ {1, 2}. Admitting the Lambert W function extends closed-form solvability strictly to α∈ {−1, 1/2}. Finally, the asymptotic limit α→ 0 converges to a singular dynamics solved by the logarithmic integral. These results constitute a complete classification of all explicit closed-form solutions admitted by this system.
ER -