Bressan's compactness conjecture for nearly incompressible flows

Let bk:[0,+[×RdRdb_k:[0,+\infty[\times\mathbb{R}^d\to\mathbb{R}^d, kNk\in\mathbb{N}, be a sequence of smooth vector fields, and let XkX_k denote their classical flows. Assume that

bk+bkL1\|b_k\|_\infty+\|\nabla b_k\|_{L^1}

is uniformly bounded, and that the flows are uniformly nearly incompressible: for some constant C>0C>0,

1Cdet(xXk(t,x))C.\frac{1}{C}\leq{\rm \det}(\nabla_xX_k(t,x))\leq C.

Bressan's compactness conjecture. Under these assumptions, the sequence {Xk}\{X_k\} is strongly precompact in Lloc1([0,+[×Rd)L^1_{\operatorname{loc}}([0,+\infty[\times\mathbb{R}^d).

This conjecture concerns compactness of flows under uniform bounds on the vector fields and their gradients and a uniform nondegeneracy condition on the Jacobians. The source notes that a positive answer to the renormalization conjecture would imply a positive answer to this compactness conjecture.

Sources & referencesView supporting material

Primary source

Gianluca Crippa and Laura V. Spinolo, “An Overview on Some Results Concerning the Transport Equation and its Applications to Conservation Laws”, arXiv:0911.2675 (2009).

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