43 research outputs found
The Kato Square Root Problem for Mixed Boundary Conditions
We consider the negative Laplacian subject to mixed boundary conditions on a
bounded domain. We prove under very general geometric assumptions that slightly
above the critical exponent its fractional power domains still
coincide with suitable Sobolev spaces of optimal regularity. In combination
with a reduction theorem recently obtained by the authors, this solves the Kato
Square Root Problem for elliptic second order operators and systems in
divergence form under the same geometric assumptions.Comment: Inconsistencies in Section 6 remove
Non-local Gehring lemmas in spaces of homogeneous type and applications
We prove a self-improving property for reverse H{\"o}lder inequalities with
non-local right hand side. We attempt to cover all the most important
situations that one encounters when studying elliptic and parabolic partial
differential equations as well as certain fractional equations. We also
consider non-local extensions of A weights. We write our results in
spaces of homogeneous type.Comment: Revised version. Changed title. Application to a more relevant
fractional elliptic equation given in the final section. 40 page
Explicit improvements for -estimates related to elliptic systems
We give a simple argument to obtain -boundedness for heat
semigroups associated to uniformly strongly elliptic systems on
by using Stein interpolation between Gaussian estimates and hypercontractivity.
Our results give explicitly in terms of ellipticity. It is optimal at the
endpoint . We also obtain -estimates for the gradient
of the semigroup, where depends on ellipticity but not on dimension.Comment: 16 pages, improved readability, accepted for publication in Bulletin
of the LM
On regularity of weak solutions to linear parabolic systems with measurable coefficients
We establish a new regularity property for weak solutions of parabolic
systems with coefficients depending measurably on time as well as on all
spatial variables. Namely, weak solutions are locally H{\"o}lder continuous Lp
valued functions for some p > 2.Comment: 23 pages. Proof of Lemma 3.3 corrected. Final version to appear in J.
Math. Pures App