1,144 reputation
811
bio website northeastern.edu/suciu
location Boston
age
visits member for 3 years, 3 months
seen 1 hour ago

Dec
13
awarded  Necromancer
Dec
13
comment Please help me to find a paper by J. Wu
Have you tried (hopf.math.purdue.edu/WuJ/newsimplicialgroup_1.pdf)?
Dec
10
answered Fundamental groups of normal complex quasi-projective varieties
Dec
7
comment Can any Delone set be approximated by a model set?
The Delaunay triangulation is almost universally spelled that way, as in the original French form of the name, instead of the Cyrillic transliteration...
Dec
7
comment Can any Delone set be approximated by a model set?
Is Delone an alternate spelling of Boris Delaunay (en.wikipedia.org/wiki/Boris_Delaunay), or is that someone else?
Dec
7
comment Lower Central Series of Pure Braid Groups?
Have you tried looking at the book on Combinatorial group theory by Magnus, Karrass, and Solitar?
Dec
7
comment Lower Central Series of Pure Braid Groups?
By induction on $n$, using the known structure of $\Gamma_k F_r$.
Dec
7
answered Lower Central Series of Pure Braid Groups?
Nov
28
comment Action of the pure braid group on the commutator subgroup of a free group
For a thorough discussion of the status of the faithfulness problem for the Gassner representation, see Joan Birman's review of the paper "Braid groups are linear groups" by Seymour Bachmuth, at ams.org/mathscinet-getitem?mr=1399602
Nov
2
comment Bockstein homomorphism from $H^d(BG,Z_2)$ to $H^{d+1}(BG,Z)$, and Steenrod Square $Sq^1$
Yes, that's correct.
Oct
31
comment How to compute $\pi_{3}$ of $L(p,q)\# L(p',q')$?
@FernandoMuro: the group ring $\mathbb{Z} G$ of a group $G$ is the free abelian group on $G$ (as a group).
Oct
30
comment How to compute $\pi_{3}$ of $L(p,q)\# L(p',q')$?
The second homotopy group of $M\# N$ is the group ring of $\pi_1(M)*\pi_1(N)$. Composing with the Hopf map $S^3\to S^2$ yields non-trivial elements of $\pi_3(M\# N)$. When, say, $M$ is a lens space, we also have non-trivial elements of $\pi_3(M\# N)$ coming from $\pi_3(M)=\mathbb{Z}$.
Sep
16
awarded  Yearling
Aug
7
comment Is there a finitely presented group with infinite homology over $\mathbb{Q}$?
Yes, $H_2$ of an fp group is finitely generated. But, say, $H_3$ needs not be finitely generated. The first such example was given by John Stallings, in a seminal paper, titled, sure enough, A finitely presented group whose 3-dimensional integral homology is not finitely generated, see here.
Aug
7
comment Is there a finitely presented group with infinite homology over $\mathbb{Q}$?
Also, "infinite homology" means "infinite-dimensional homology" (as $\mathbb{Q}$-vector space), right?
Aug
7
comment Is there a finitely presented group with infinite homology over $\mathbb{Q}$?
Just to make sure: the assertion that $H_i(G,\mathbb{Q})$ is finite-dimensional (for all $i>2$) is an assumption, yes?
Jul
19
awarded  Nice Answer
Jul
18
revised Is it known which links have Seifert fibered complements?
added 192 characters in body
Jul
18
answered Is it known which links have Seifert fibered complements?
Apr
3
comment Kahler structure on holomorphic principal bundles
What's a "principle" bundle?