4 papers
Groups generated by positive multi-twists and the fake lantern problem
Hessam Hamidi-Tehrani
Let Gamma be a group generated by two positive multi-twists. We give some sufficient conditions for Gamma to be free or have no `unexpectedly reducible' elements. For a group Gamma…
On the linearity problem for mapping class groups
Tara E. Brendle, Hessam Hamidi-Tehrani
Formanek and Procesi have demonstrated that Aut(F_n) is not linear for n >2. Their technique is to construct nonlinear groups of a special form, which we call FP-groups, and then t…
Groups Generated by Powers of Dehn Twists
Hessam Hamidi-Tehrani
We classify groups generated by powers of 2 Dehn twists which are 1) free or 2) have no ``unexpected'' reducible elements. We give some sufficient conditions in the case of groups…
On Complexity of the Word Problem in Braid Groups and Mapping Class Groups
Hessam Hamidi-Tehrani
We prove that the word problem in the mapping class group of the once-punctured surface of genus g has complexity O(|w|^2 g for |w| > log(g) where |w| is the length of the word in…