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seen Jun 17 '13 at 11:21

Jul
5
comment Block Diagonalizing an antisymmetric matrix
yeah, it's an antisymmetric matrix and it will probably have compex eigenvalues. so, my question is how to put it in block diagonal form. Thanks!
Jul
5
asked Block Diagonalizing an antisymmetric matrix
Jul
1
comment Open sets, topology
@Qiaochu Yuan: Okay! I understand the analogy you give in the link! Thank you!
Jun
30
comment Open sets, topology
So, more generally, is it just that when you take the intersection of an infinite number of sets, there's a possibility of getting a closed set. So, we just exclude such intersections?
Jun
30
awarded  Student
Jun
30
comment Open sets, topology
I'm sorry, I'm not sure if the answer in the link you provided and the question GEdgar is asking make complete sense to me. So, is the point that an intersection of an infinite number of open sets might not be open because it could turn out to be a single point (which would be closed), or is it that it's too difficult to determine if the intersection of an infinite number of open sets is open (which is what the first answer in the link you gave says.)
Jun
30
asked Open sets, topology