Matti Åstrand

331 reputation

	331 reputation	bio	website		visits	member for	2 years, 9 months
14 badges		location	Philadelphia, PA		seen	May 12 at 19:58

14 Actions

May 5	comment	What is the proper name of this class of rings? I guess I would just call it "an integral domain of characteristic 0"... But your statement about polynomials is not true: $R$ could also be an infinite integral domain of characteristic $p$.
May 1	comment	I need to diagonalize this matrix but I'm not sure it can be It can't be diagonalized, since the matrix only has one eigenvector for the double eigenvalue. You should check out "Jordan Normal Form".
May 1	answered	Is the following problem convex?
May 1	comment	Is the following problem convex? It's not true in general that a composition of two convex functions is convex. See this question
Mar 25	answered	Is there a property that isolates the formulas that remain valid as you move from the natural numbers to the integers?
Mar 14	comment	Shortest string possible I would think it has to be 0100010. The shortest one can't have a substring that's also an instance of S.
Mar 14	comment	Count indices in summation I think inclusion-exclusion principle might help you.
Jul 28	awarded	Yearling
Jul 16	awarded	Nice Answer
Jul 29	awarded	Editor
Jul 29	revised	Why is the “finitely many” quantifier not definable in First Order Logic? Correction.
Jul 28	awarded	Teacher
Jul 28	answered	Why is the “finitely many” quantifier not definable in First Order Logic?
Jul 27	awarded	Supporter