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Parabolic Q-minima and minimal solutions to variational flow. (English) Zbl 0674.35042
The purpose of the paper is to provide a unified version of some regularity results on parabolic systems of the form $u'-\sum D_{x_ i}(D_{p_ i}F(x,u,Du))+D_ uF(x,u,Du)=0.$ To this aim, the notion of parabolic Q-minimum is introduced, where Q is a real number greater than or equal to 1. It is an adaptation to the parabolic case of the notion of (elliptic) Q-minimum introduced in M. Giaquinta and E. Giusti [Ann. Inst. Henri Poincaré, Anal. Non Linéaire 1, 79-104 (1984; Zbl 0541.49008)].
Results on $$L^ p$$-summability of the spatial derivatives of u, Hölder continuity of u (in the scalar case) and partial Hölder continuity of u (in the vector case) are given for parabolic Q-minima.
More special results are proved for the so-called minimal solutions, namely Q-minima with $$Q=1$$. A characterization of the existence of such minimal solutions is given in terms of the convexity of the associated functional $$\int F(x,u,Du)dx$$.
Reviewer: M.Degiovanni

##### MSC:
 35K55 Nonlinear parabolic equations 35B65 Smoothness and regularity of solutions to PDEs 35A15 Variational methods applied to PDEs
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##### References:
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