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Apr
25
comment Extension property for unipotent linear groups over rings
@S.A.K.A. John You have changed the wording again. It still does not make sense. Now $G$ has nothing to do with $R$. Is $G$ an abstract group or not? What does "over some ring" mean? My example shows that such things matter. As a real Lie group my example has only one nontrivial normal subgroup, but it should never be written $\mathbb{G}_a$.
Apr
25
answered Extension property for unipotent linear groups over rings
Apr
20
comment Complexity of solving systems of linear diophantine equations
Why Smith normal form? Hermite normal form suffices.
Mar
29
comment Do degrees determine the chromatic number?
Play with the Petersen graph. Its edges have no three coloring. Now `untwist' it.
Mar
21
awarded  Yearling
Mar
11
awarded  Civic Duty
Sep
26
awarded  Good Answer
Sep
26
revised How to prove this polynomial always has integer values at all integers?
formula ran off page
Sep
26
revised How to prove this polynomial always has integer values at all integers?
formula ran off page
Sep
26
awarded  Enlightened
Sep
25
comment How to prove this polynomial always has integer values at all integers?
It was take home.
Sep
23
comment cohomology theory for algebraic groups
@David_Stuart The paper by Brian is called "Cohomology of Algebraic groups" and it explains that generic cohomology of a finite dimensional module equals discrete cohomology because the projective limit satisfies the Mittag-Leffler condition.
Sep
23
comment cohomology theory for algebraic groups
@David_Stuart. Am I missing a projective limit? Is the argument of van der Kallen that this is the kind of limit that is treated by J. E. Roos in LNM 92, Berlin 1969 ?
Sep
23
comment cohomology theory for algebraic groups
Why refer to something that is difficult to get hold of? Just refer to our 1977 Inventiones paper which was a joint paper for good reasons.
Sep
22
revised How to prove this polynomial always has integer values at all integers?
91 replaced with 153
Sep
22
revised How to prove this polynomial always has integer values at all integers?
three inequalities corrected
Sep
21
revised How to prove this polynomial always has integer values at all integers?
one more number corrected
Sep
21
revised How to prove this polynomial always has integer values at all integers?
two numbers changed
Sep
18
awarded  Nice Answer
Sep
18
awarded  Necromancer