Open Access
2013/2014 Directional Lower Porosity
Gareth Speight
Real Anal. Exchange 39(1): 45-56 (2013/2014).


We investigate differences between upper and lower porosity. In finite dimensional Banach spaces every upper porous set is directionally upper porous. We show the situation is very different for lower porous sets; there exists a lower porous set in \(\mathbb{R}^2\) which is not even a countable union of directionally lower porous sets.


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Gareth Speight. "Directional Lower Porosity." Real Anal. Exchange 39 (1) 45 - 56, 2013/2014.


Published: 2013/2014
First available in Project Euclid: 1 July 2014

zbMATH: 1298.28005
MathSciNet: MR3261898

Primary: 28A05 , 28A75

Keywords: Directed Porosity , Directionally Porous , lower porosity , Sigma Porous

Rights: Copyright © 2013 Michigan State University Press

Vol.39 • No. 1 • 2013/2014
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