Scheven, Christoph Partial regularity for subquadratic parabolic systems by \(\mathcal{A}\)-caloric approximation. (English) Zbl 1235.35061 Rev. Mat. Iberoam. 27, No. 3, 751-801 (2011). The paper is concerned with nonsingular parabolic systems of the form \(\partial_tu-\nabla\cdot a(t,x,u,Du)=B(x,t,u,Du)\). The structure function \(a\) is assumed to fulfill ellipticity and regularity conditions which are fairly general and quite natural. Moreover, it is assumed to have “polynomial” growth with growth rate \(p\in( {2n\over n+1},2)\). The assumptions on \(B\) are the usual ones.Partial regularity of weak solutions is proven, up to a singular set of vanishing measure in spacetime. Different characterizations of the singular sets are given. In the case \(p>2\) the problem has been solved (see e.g.[F. Duzaar, G. Mingione and K. Steffen, Mem. Am. Math. Soc. 1005, i-x, 118 p. (2011; Zbl 1238.35001)] and the references therein), and even under more general assumptions. Regularity in the subquadratic case \(p<2\), however, has not been treated before the current paper, except for very special equations. The proof uses a variant of the technique of harmonic approximation. Reviewer: Andreas Gastel (Duisburg) Cited in 14 Documents MSC: 35B65 Smoothness and regularity of solutions to PDEs 35K40 Second-order parabolic systems 35K59 Quasilinear parabolic equations Keywords:parabolic systems; partial regularity; harmonic approximation; singular set; subquadratic growth Citations:Zbl 1238.35001 PDF BibTeX XML Cite \textit{C. Scheven}, Rev. Mat. Iberoam. 27, No. 3, 751--801 (2011; Zbl 1235.35061) Full Text: DOI Euclid References: [1] Acerbi, E. and Fusco, N.: Regularity for minimizers of nonquadratic functionals: the case 1 < p < 2. J. Math. Anal. Appl. 140 (1989), no. 1, 115-135. · Zbl 0686.49004 [2] Beck, L.: Partial regularity for weak solutions of nonlinear elliptic systems: the subquadratic case. 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