https://kbeanland.wordpress.com/research-articles/ Kevin Beanland ASSOCIATE PROFESSOR OF MATHEMATICS in the Department of Mathematics at Washington and Lee University.
Research Articles My main research area is Banach space theory but, I have some work in real analysis and know some descriptive set theory as it applies to Banach space theory.
https://kbeanland.files.wordpress.com/2010/01/beanlandrobstevensonmonthly.pdf Modifications of Thomae’s function and differentiability, (with James Roberts and Craig Stevenson) Amer. Math. Monthly, 116 (2009), no. 6, 531-535. (抜粋) 3. A DENSE SET. While attempting to prove that T(1/n2) is differentiable on the irrationals, we discovered that quite the opposite is actually true. In fact, as the following proposition indicates, functions that are zero on the irrationals and positive on the rationals will always be non-differentiable on a rather large set.
Proposition 3.1. Let f be a function on R that is positive on the rationals and 0 on the irrationals. Then there is an uncountable dense set of irrationals on which f is not differentiable. (引用終り)
