bio  website  jamespropp.org 

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visits  member for  4 years, 11 months 
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I am interested in combinatorics, probability, dynamical systems, and various other topics.
2h

revised 
Notions of positivity for qpolynomials
added 5 characters in body 
18h

revised 
Notions of positivity for qpolynomials
Clarified that coefficients need not be positive 
18h

asked  Notions of positivity for qpolynomials 
Dec 20 
revised 
Nonperiodic points of piecewiselinear homeomorphisms
added 212 characters in body 
Dec 20 
accepted  Nonperiodic points of homeomorphisms of a ball 
Dec 20 
comment 
Nonperiodic points of homeomorphisms of a ball
The original journal reference for this theorem is D. Montgomery. Pointwise periodic homeomorphisms, Amer. J. Math. 59 (1937), 118120. Thanks! 
Dec 19 
comment 
Nonperiodic points of homeomorphisms of a ball
What is the "doubling" trick Rivin is referring to? 
Dec 19 
awarded  Nice Question 
Dec 19 
revised 
Nonperiodic points of piecewiselinear homeomorphisms
added 188 characters in body 
Dec 19 
asked  Nonperiodic points of homeomorphisms of a ball 
Dec 18 
comment 
Nonperiodic points of piecewiselinear homeomorphisms
The paragraph "The sets $E_{n⋅k}∩$ △′ are closed. They might have nonempty interiors but the complement contains a controlable open set near the boundary of $E_n$. It is sufficient to apply the proof Baire theorem and conclude that $E_{n⋅k}$ do not cover △′. The later leads to a contradiction" is unclear to me. 
Dec 17 
comment 
Nonperiodic points of piecewiselinear homeomorphisms
I still don't understand. I'm going to post a bounty, so that Anton (or others) will have an extra incentive to write a clear and complete proof. 
Dec 15 
comment 
Nonperiodic points of piecewiselinear homeomorphisms
In the articleinprogress arxiv.org/abs/1310.5294, David Einstein and I prove that a certain piecewiselinear homeomorphism on the order polytope of the poset $[2] \times [2]$ has infinite order, by constructing arbtrarily long orbitsegments. (Actually, we don't do this in the current draft, but we plan to add details soon.) We'd like to know that nonperiodic points exist, and indeed that "most" point are nonperiodic, in the sense of measure or the sense of category. And of course we'd like to know this for other, similar examples. 
Dec 15 
comment 
Nonperiodic points of piecewiselinear homeomorphisms
Anton, your comment about rectangles was very helpful, and I'll explain in a minute why I need this result, but first let me ask why we can conclude that the sets $E_{n \cdot k}$ do not cover $\Delta'$. I don't follow this step. 
Dec 13 
comment 
Nonperiodic points of piecewiselinear homeomorphisms
I don't understand the sentence "They might have nonempty interiors but the complement contains a controlable open set near the boundary of $E_n$" (partly because I don't know what "controlable" means). 
Dec 11 
asked  Nonperiodic points of piecewiselinear homeomorphisms 
Dec 2 
accepted  A generalized meanvalue theorem 
Dec 2 
asked  A generalized meanvalue theorem 
Nov 14 
accepted  Origin of the numbers game 
Nov 14 
comment 
Origin of the numbers game
I hear that Knuth studied it as well; can anyone provide a pointer to Knuth's article? 