Higher-spatial-regularity conjecture for the Augmented formula

Let n2n\geq 2 with nNn\in\mathbb{N}. Let Hκn\mathbb{H}^n_\kappa be the two-dimensional vectorial field equipped with the weighted norm specified below. For even nn, define

uHn2:=u1Lr22+ru1Lr22+drru1Lr22++(rdr)n/2u1Lr22+u2L22+dru2Lr22+rdru2Lr22++(drr)n/2u2Lr22+κ2(drr)n/2dru2Lr22.\begin{aligned} \lVert u\rVert_{\mathbb{H}^{n}}^2:= {}&\lVert u_1\rVert_{L^2_r}^2+\lVert\partial_r u_1\rVert_{L^2_r}^2+\lVert {\rm d}_r\partial_r u_1\rVert_{L^2_r}^2+\cdots+\lVert(\partial_r{\rm d}_r)^{n/2}u_1\rVert_{L^2_r}^2\\ &+\lVert u_2\rVert_{L^2}^2+\lVert{\rm d}_r u_2\rVert_{L^2_r}^2+\lVert\partial_r{\rm d}_r u_2\rVert_{L^2_r}^2+\cdots+\lVert({\rm d}_r\partial_r)^{n/2}u_2\rVert_{L^2_r}^2+\kappa^2\lVert({\rm d}_r\partial_r)^{n/2}{\rm d}_r u_2\rVert_{L^2_r}^2. \end{aligned}

For odd nn, define

uHn2:=u1Lr22+ru1Lr22+drru1Lr22++(drr)(n1)/2dru1Lr22+u2L22+dru2Lr22+rdru2Lr22++dr(rdr)(n1)/2u2Lr22+κ2(rdr)(n+1)/2u2Lr22.\begin{aligned} \lVert u\rVert_{\mathbb{H}^{n}}^2:= {}&\lVert u_1\rVert_{L^2_r}^2+\lVert\partial_r u_1\rVert_{L^2_r}^2+\lVert {\rm d}_r\partial_r u_1\rVert_{L^2_r}^2+\cdots+\lVert({\rm d}_r\partial_r)^{(n-1)/2}{\rm d}_r u_1\rVert_{L^2_r}^2\\ &+\lVert u_2\rVert_{L^2}^2+\lVert{\rm d}_r u_2\rVert_{L^2_r}^2+\lVert\partial_r{\rm d}_r u_2\rVert_{L^2_r}^2+\cdots+\lVert{\rm d}_r(\partial_r{\rm d}_r)^{(n-1)/2}u_2\rVert_{L^2_r}^2+\kappa^2\lVert(\partial_r{\rm d}_r)^{(n+1)/2}u_2\rVert_{L^2_r}^2. \end{aligned}

Higher-spatial-regularity conjecture. The Augmented formula is well-posed in Ck([0,T),Hn×R4)\mathscr{C}^k\left([0,T),\mathbb{H}^n\times\mathbb{R}^4\right), with the corresponding weighted norm above according to the parity of nn. The conjecture is motivated by applying the indicated alternating radial differential operators to the Augmented formula. The supplied passage gives no result establishing or refuting this higher-regularity claim.

Sources & referencesView supporting material

Primary source

Geoffrey Beck, Ewan Contentin and Ludovic Martaud, “Freely floating cylinder on a 3D fluid governed by the Boussinesq equations in the axisymmetric without swirl case”, arXiv:2601.03133 (2026).

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