TITLE:
Old and new results on SNAs on the real line

AUTHORS:
Angel Jorba^1, Carmen Nuņez^2, Rafael Obaya^2, Joan Carles Tatjer^1

(1) Departament de Matematica Aplicada i Analisi
    Universitat de Barcelona
    Gran Via 585
    08007 Barcelona, Spain.

(2) Departamento de Matematica Aplicada
    E.T.S. de Ingenieros Industriales
    Universidad de Valladolid
    Paseo del Cauce S/N
    47011 Valladolid, Spain.
    
E-Mails: angel@maia.ub.es, carnun@wmatem.eis.uva.es,
         rafoba@wmatem.eis.uva.es, jcarles@maia.ub.es

ABSTRACT:
Classical and new results concerning the topological structure of
skew-products semiflows, coming from non-autonomous maps and
differential equations, are combined in order to establish rigorous
conditions giving rise to the occurrence of strange nonchaotic
attractors. A special attention is paid to the relation of these sets
with the almost automorphic extensions of the base flow. The scope of
the results is clarified by applying them to the Harper map, although
they are valid in a much wider context.