The entropy production is not always monotone for hard spheres or for Maxwell molecules

Luis Silvestre

For the three-dimensional space-homogeneous Boltzmann equation with collision kernel B=|v−v*|^γ/(4π), 0≤γ≤1, Silvestre constructs smooth positive radial two-Maxwellian initial densities f_R=(1−p)M₁+pM_R. For 0<p<p_γ and sufficiently large R, the entropy production D initially increases: dD(f_R)/dt>0 at t=0, with a positive leading term proportional to R^γ log R. The range includes constant-angle Maxwell molecules and hard spheres.

Sources for this record

What was already known

Silvestre had earlier disproved the broader monotonicity claim using a singular collision kernel. That construction did not cover these physical kernels.

AI involvement AI-led

Silvestre credits ChatGPT 5.6 Sol in Codex Ultra with the first proof of the physical-kernel result, working from his earlier paper and notes. Claude Code made an initial rewrite; Silvestre reinterpreted and restructured the final argument.

The first proof of the new physical-kernel claim is expressly model-origin, within a human-defined program and with substantial later human reconstruction; independent model autonomy is not supported.

Importance Notable

Provides counterexamples in the standard Maxwell-molecule and hard-sphere settings.

Limitations

The claim concerns the specified homogeneous Boltzmann kernels and two-Maxwellian data; it does not address the Landau equation or arbitrary kernels. The paper gives an analytic proof and a human-reworked explanation, but no explicit completed proof check or machine verification of this theorem is documented.

Technical verification Reported

The paper contains an analytic proof and Silvestre reworked it, but neither an explicit complete human check nor a machine check of this exact result is documented. Author responsibility and registry labels alone do not establish Formal.

Human understanding Full

Silvestre says he reinterpreted and restructured the initial model proof, and his exposition explains the asymptotic balance yielding a positive derivative.

Correction and publication history

2026-10-18 · publication

The paper attributes the physical-kernel proof to ChatGPT and presents a human-reworked argument.

Read this published revision