On the existence of extremals for the critical Sobolev immersion with variable exponents

Abstract

In this work we review some recent results conserning the existence problem of an extremal for the immersion W 1,p(x) 0 (Ω),→ L q(x) (Ω) in the critical range, i.e. A = {x ∈ Ω: q(x) = p ∗ (x)} 6= /0, where p ∗ (x) = N p(x)/(N − p(x)) is the critical Sobolev exponent.