Abstract
We prove sharp regularity results for a general class of functionals of the type
featuring non-standard growth conditions and non-uniform ellipticity properties. The model case is given by the double phase integral
with \(0<\nu \le b(\cdot )\le L \). This changes its ellipticity rate according to the geometry of the level set \(\{a(x)=0\}\) of the modulating coefficient \(a(\cdot )\). We also present new methods and proofs that are suitable to build regularity theorems for larger classes of non-autonomous functionals. Finally, we disclose some new interpolation type effects that, as we conjecture, should draw a general phenomenon in the setting of non-uniformly elliptic problems. Such effects naturally connect with the Lavrentiev phenomenon.
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Communicated by L. Ambrosio.
To Paolo Marcellini on his 70th birthday, with admiration for his pioneering work in the Calculus of Variations.
The authors thank the referee, for his/her careful reading of the original manuscript and for providing several remarks that eventually led to a better final version.