Geometric Analysis of the Damped Harmonic Oscillator via the Lambert W Function

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Auteurs principaux: Sharma, Arpan, Jogi, Bhargava, Roberts, Ken, Molli, Muralikrishna, Valluri, S. R.
Format: Preprint
Publié: 2026
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author Sharma, Arpan
Jogi, Bhargava
Roberts, Ken
Molli, Muralikrishna
Valluri, S. R.
author_facet Sharma, Arpan
Jogi, Bhargava
Roberts, Ken
Molli, Muralikrishna
Valluri, S. R.
contents The underdamped harmonic oscillator is analyzed through the complex mapping $ζ= e^{-iφ}we^{-w}$ with $w = βt + iΩt$, which transforms the dynamics into a logarithmic spiral. Within this framework, the displacement extrema correspond to crossings of the imaginary axis by $ζ(t)$, yielding the explicit times $t_n = (θ- φ- π/2 + nπ)/Ω$, where $θ= \arctan(Ω/β)$. The Lambert $W$ function provides closed-form solutions $t = -β^{-1}W_k(-βA/ω_0)$ for the times at which the spiral radius attains a given threshold $A$, covering both the rising and decaying branches. The quality factor $Q = ω_0/(2β) = \tfrac{1}{2}\secθ$ is directly encoded in the ray angle $θ$ of the $(u,v)$-plane. Key geometric invariants are derived: the winding number $N_\varepsilon \approx (Q/π)\ln(2Q/\varepsilon)$ for large $Q$, the enclosed area $A = ω_0^2Ω/(8β^3) \approx Q^3$ in the lightly damped limit, and the energy decay $E(t) = E_0 e^{-ω_0 t/Q}$. Three methods for determining $Q$ from experimental data are compared: logarithmic decrement, ray-angle measurement, and spiral turn counting. The turn-counting method proves particularly robust for high-$Q$ systems, where successive amplitude peaks differ by tiny fractions. The framework unifies classical damped oscillations with complex analysis and special functions.
format Preprint
id arxiv_https___arxiv_org_abs_2605_31456
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Geometric Analysis of the Damped Harmonic Oscillator via the Lambert W Function
Sharma, Arpan
Jogi, Bhargava
Roberts, Ken
Molli, Muralikrishna
Valluri, S. R.
Mathematical Physics
The underdamped harmonic oscillator is analyzed through the complex mapping $ζ= e^{-iφ}we^{-w}$ with $w = βt + iΩt$, which transforms the dynamics into a logarithmic spiral. Within this framework, the displacement extrema correspond to crossings of the imaginary axis by $ζ(t)$, yielding the explicit times $t_n = (θ- φ- π/2 + nπ)/Ω$, where $θ= \arctan(Ω/β)$. The Lambert $W$ function provides closed-form solutions $t = -β^{-1}W_k(-βA/ω_0)$ for the times at which the spiral radius attains a given threshold $A$, covering both the rising and decaying branches. The quality factor $Q = ω_0/(2β) = \tfrac{1}{2}\secθ$ is directly encoded in the ray angle $θ$ of the $(u,v)$-plane. Key geometric invariants are derived: the winding number $N_\varepsilon \approx (Q/π)\ln(2Q/\varepsilon)$ for large $Q$, the enclosed area $A = ω_0^2Ω/(8β^3) \approx Q^3$ in the lightly damped limit, and the energy decay $E(t) = E_0 e^{-ω_0 t/Q}$. Three methods for determining $Q$ from experimental data are compared: logarithmic decrement, ray-angle measurement, and spiral turn counting. The turn-counting method proves particularly robust for high-$Q$ systems, where successive amplitude peaks differ by tiny fractions. The framework unifies classical damped oscillations with complex analysis and special functions.
title Geometric Analysis of the Damped Harmonic Oscillator via the Lambert W Function
topic Mathematical Physics
url https://arxiv.org/abs/2605.31456