We prove that if f: → is Darboux and has a point of prime period different from , i = 0,1,..., then the entropy of f is positive. On the other hand, for every set A ⊂ ℕ with 1 ∈ A there is an almost continuous (in the sense of Stallings) function f: → with positive entropy for which the set Per(f) of prime periods of all periodic points is equal to A.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-cm121-1-9, author = {Tomasz Natkaniec and Piotr Szuca}, title = {On Pawlak's problem concerning entropy of almost continuous functions}, journal = {Colloquium Mathematicae}, volume = {120}, year = {2010}, pages = {107-111}, zbl = {1206.26003}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm121-1-9} }
Tomasz Natkaniec; Piotr Szuca. On Pawlak's problem concerning entropy of almost continuous functions. Colloquium Mathematicae, Tome 120 (2010) pp. 107-111. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm121-1-9/