2010/09/10 by Carlo Morosi, Livio Pizzocchero · 6 citations
Mathematics · Physics and Astronomy · #math.AP #math-ph #math.FA #math.MP #msc:76D05 #msc:26D10 #msc:46E35
paper · pdf · doi:10.3934/cpaa.2012.11.557
published as Commun. Pure Appl. Anal. 11(2)(2012), 557-586 · LaTeX, 39 pages. arXiv admin note: text overlap with arXiv:1007.4412 by the same authors, not concerning the main results
arxiv created 2010/09/10 · arxiv updated 2012/09/08
We continue an analysis, started in [10], of some issues related to the incompressible Euler or Navier-Stokes (NS) equations on a d-dimensional torus Td. More specifically, we consider the quadratic term in these equations; this arises from the bilinear map (v, w) -> v . D w, where v, w : Td -> Rd are two velocity fields. We derive upper and lower bounds for the constants in some inequalities related to the above bilinear map; these bounds hold, in particular, for the sharp constants Gn d = Gn in the Kato inequality | < v . D w | w >n | <= Gn || v ||n || w ||2n, where n in (d/2 + 1, + infinity) and v, w are in the Sobolev spaces Hn, H^(n+1) of zero mean, divergence free vector fields of orders n and n+1, respectively. As examples, the numerical values of our upper and lower bounds are reported for d=3 and some values of n. When combined with the results of [10] on another inequality, the results of the present paper can be employed to set up fully quantitative error estimates for the approximate solutions of the Euler/NS equations, or to derive quantitative bounds on the time of existence of the exact solutions with specified initial data; a sketch of this program is given.