TY - JOUR ID - Goodman2008 LB - Goodman2008 AU - Goodman, Gerald S. TI - Fractal sets satisfying the strong open set condition in complete metric spaces ST - Fractal sets satisfying the strong open set condition in complete metric spaces JO - Opuscula Math. JA - Opuscula Math. JF - Opuscula Mathematica PY - 2008 VL - 28 IS - 4 SP - 463 EP - 470 DO - http://dx.doi.org/10.7494/OpMath.2008.28.4.463 UR - http://dx.doi.org/10.7494/OpMath.2008.28.4.463 AB - Let \(K\) be a Hutchinson fractal in a complete metric space \(X\), invariant under the action \(S\) of the union of a finite number of Lipschitz contractions. The Open Set Condition states that \(X\) has a non-empty subinvariant bounded open subset \(V\), whose images under the maps are disjoint. It is said to be strong if \(V\) meets \(K\). We show by a category argument that when \(K \not\subset V\) and the restrictions of the contractions to \(V\) are open, the strong condition implies that \(\check{V}=\bigcap_{n=0}^{\infty} S^n(V)\), termed the core of \(V\) , is non-empty. In this case, it is an invariant, proper, dense, subset of \(K\), made up of points whose addresses are unique. Conversely, \(\check{V}\neq \emptyset\) implies the SOSC, without any openness assumption. KW - address KW - Baire category KW - fractal KW - scaling function KW - scaling operator KW - strong open set condition SN - 1232-9274 ER -