2014/10/12 by Shvartsman, Pavel, Zobin, Nahum
#46E35 #FOS: Mathematics #Functional Analysis (math.FA)
paper · doi:10.48550/arxiv.1410.3100
For each m≥ 1 and p>2 we characterize bounded simply connected Sobolev Lmp-extension domains Ω⊂ R2. Our criterion is expressed in terms of certain intrinsic subhyperbolic metrics in Ω. Its proof is based on a series of results related to the existence of special chains of squares joining given points x and y in Ω. An important geometrical ingredient for obtaining these results is a new "Square Separation Theorem". It states that under certain natural assumptions on the relative positions of a point x and a square S⊂Ω there exists a similar square Q⊂Ω which touches S and has the property that x and S belong to distinct connected components of Ω∖ Q.