## Alternative definitions of $${\mathcal J}$$-density topology.(English)Zbl 0666.26002

The author presents six alternative definitions of Wilczyński’s $${\mathcal J}$$-density point. Some of them are similar to the original definition of Wilczyński, while the others (for example (5)) are of completely different form. [There is an error in references: the seventh position should be L. Zajíček, Real Anal. Exch. 12(1986/87), 313- 326 (1987; Zbl 0641.26004).]
Reviewer: J.Niewiarowski

### MSC:

 26A15 Continuity and related questions (modulus of continuity, semicontinuity, discontinuities, etc.) for real functions in one variable 54A10 Several topologies on one set (change of topology, comparison of topologies, lattices of topologies) 26A03 Foundations: limits and generalizations, elementary topology of the line 28A05 Classes of sets (Borel fields, $$\sigma$$-rings, etc.), measurable sets, Suslin sets, analytic sets

Zbl 0641.26004
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