863 reputation
411
bio website gmarks.org
location
age
visits member for 3 years, 10 months
seen yesterday
Note. I am less likely to respond to questions posed anonymously.

Oct
19
awarded  Necromancer
Sep
13
comment What is the expected number of random numbers (generated uniformly) such that their sum of numbers exceeds one?
This question was Problem A3 of the 1958 Putnam Competition (and as such is not research-level mathematics).
Sep
13
awarded  Informed
Aug
20
answered Proof a Weyl Algebra isn't isomorphic to a matrix ring over a division ring
Jul
29
answered Subgroups of finite index of fields
Jun
25
awarded  Revival
Jun
2
awarded  Yearling
Jul
6
comment How do you present a non-existence theorem?
This story implicitly answers the problem of the student who shrugs upon hearing the theorem on bounded entire functions. By the time it occurs in a class it's very natural, but presented with it cold, the reaction of any student of normal inquisitiveness would be astonishment and an attempt at a counterexample. A student who isn't excited about celebrated classical results is perhaps best advised to find a field of study more to his liking. Incidentally, a result that has allured many a student into mathematics is, so to speak, a non-existence non-theorem: the continuum hypothesis.
Jul
6
comment How do you present a non-existence theorem?
My first reaction on seeing the title of this question was to recall Rota's "Ten Lessons I Wish I Had Been Taught": completely erase the blackboard, begin writing in the upper left corner, ....
Jun
17
awarded  Nice Answer
Jun
13
answered When is a topological group Hausdorff (separated)?
Jun
2
awarded  Yearling
Feb
17
awarded  Nice Answer
Aug
27
comment When a group ring is a local ring
For the general problem, can you see why the augmentation ideal is nilpotent?
Jul
30
comment How do you pronounce “Hartshorne”?
The poor devils could follow Kiran Kedlaya's example: mit.edu/~kedlaya/about-my-name.html
Jun
3
awarded  Yearling
Apr
4
comment The multiplicative order of 2 modulo primes
Simple but amusing application: that multiplicative order is the minimal number of perfect shuffles required to restore a deck of $p \pm 1$ cards (the $\pm$ depending on which of the two ways of perfectly shuffling we're talking about).
Mar
28
answered Why is it a good idea to study a ring by studying its modules?
Mar
14
comment Group ring and left zero divisor.
You are very kind to credit me, but I doubt I deserve it. I am embarrassed to say that the very interesting paper of Gutan and Kisielewicz had slipped my mind. Gutan and Kisielewicz completely resolve the group algebra reversibility question for the case of torsion groups. They remark that the torsion-free case is connected with the zero divisor problem, in the sense that it will be very difficult to produce a non-reversible group algebra with a torsion-free group, since this will of course resolve the zero divisor problem in the negative.
Mar
12
revised Group ring and left zero divisor.
added 7 characters in body