Take the tour ×  There is a lot of normal subgroups in braid
groups (for example there is an action of $B_n$ on unitriangular
bilinear forms on $R^n$ over arbitrary commutative ring $R$:
$b_i\colon e_j\mapsto e_j$, $j\ne i, i+1$, $b_i\colon
e_{i+1}\mapsto e_i$, $b_i\colon e_i\mapsto e_{i+1}-(e_i,
e_{i+1})e_i$ and set $R=\mathbb Z_m$).  Is there any
classification (with no conditions on terms of classification)
of normal subgroups of $B_n$?  update: the interesting case of
this classification for me is the case of finite index normal
subgroups. For example I don't even know what is the kernel of
the action described above. The answer may be useful in
algebraic geometry (see A.L. Gorodentsev, TRANSFORMATIONS OF
EXCEPTIONAL BUNDLES ON $\mathbb P^n$)  share|improve this
question @zroslav - I think I found the answer. Take a look at
my final edit. –  HJRW Mar 19 '11 at 0:54 @HW: I'm not sure that
I understand this classification. Neither geometric nor the
"listing" meaning are clear for me. –  zroslav Mar 19 '11 a