The general Maxwellian long-time asymptotics conjecture for collision-dominated homoenergetic flows

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Let BB be a collision cross-section satisfying condition, and let γ\gamma denote its homogeneity. Let Q(t)Q(t) and L0L_0 be the matrix-valued quantities appearing in the homoenergetic Boltzmann equation, let μ(t)\mu(t) be its time-dependent coefficient, and let β(t)\beta(t) be the temperature scale. Let L\mathbb{L} be the linearized collision operator on the weighted space L2(R3;e−∣ξ∣2dξ)L^2(\mathbb{R}^3;e^{-\lvert\xi\rvert^2}d\xi). General Maxwellian asymptotics conjecture. Under suitable assumptions on γ\gamma and μ(t)\mu(t), there exists a weak solution gg in the stated measure-valued solution class and a function β(t)\beta(t) such that

β(t)−32g(t,ξβ(t))⟶π−32e−∣ξ∣2\beta(t)^{-\frac32}g\left(t,\frac{\xi}{\sqrt{\beta(t)}}\right)\longrightarrow \pi^{-\frac32}e^{-\lvert\xi\rvert^2}

in L2(R3;e−∣ξ∣2dξ)L^2(\mathbb{R}^3;e^{-\lvert\xi\rvert^2}d\xi) as t→∞t\to\infty. In case 1, if Q(t)=L0+O(t−1−δ)Q(t)=L_0+O(t^{-1-\delta}), δ>0\delta>0, Tr⁡(L0)≠0\operatorname{Tr}(L_0)\ne0, a=23Tr⁡(L0)a=\frac23\operatorname{Tr}(L_0), and μ(t)e−γat/2≫t1+δ\mu(t)e^{-\gamma at/2}\gg t^{1+\delta}, then β(t)=Ceat(1+o(1))\beta(t)=Ce^{at}(1+o(1)). In case 2, if γ>0\gamma>0, Tr⁡(Q(t))=0\operatorname{Tr}(Q(t))=0, Q(t)=L0+o(1)Q(t)=L_0+o(1) with L0≠0L_0\ne0, λ(t)=∫0tds/μ(s)→∞\lambda(t)=\int_0^t ds/\mu(s)\to\infty, λ′(t)/λ(t)→0\lambda'(t)/\lambda(t)\to0, and b=⟨ξ⋅L0ξ,(−L)−1[ξ⋅L0ξ]⟩w>0b=\langle \xi\cdot L_0\xi,(-\mathbb{L})^{-1}[\xi\cdot L_0\xi]\rangle_w>0, then β(t)=((4/3)γbλ(t))−2/γ(1+o(1))\beta(t)=((4/3)\gamma b\lambda(t))^{-2/\gamma}(1+o(1)). These asymptotic existence and Maxwellian claims are proposed as the main general collision-dominated result; the paper supplies heuristic support through the Hilbert-expansion strategy, but no proof or resolution is given.

References

Primary source

Richard D. James, Alessia Nota and Juan J. L. Velázquez, “Long time asymptotics for homoenergetic solutions of the Boltzmann equation. Collision-dominated case”, arXiv:1808.06941 (2018).

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