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Jul
23
revised Worst case difference in rank by column-row swapping
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Jul
23
comment Worst case difference in rank by column-row swapping
@BrendanMcKay: Actually, I'm back to not being sure what "swapping" means, so the operation might be as in my comment or as above. Fortunately, the above argument works either way. I've included an edit to mention this.
Jul
23
revised Worst case difference in rank by column-row swapping
edited body
Jul
23
revised Worst case difference in rank by column-row swapping
deleted 366 characters in body
Jul
22
comment Worst case difference in rank by column-row swapping
I've deleted my last comment, which was nonsense.
Jul
9
revised the true reason of the incompleteness of formal systems
added 610 characters in body
Jul
9
comment Worst case difference in rank by column-row swapping
@BrendanMcKay: The operation seems to be $$\pmatrix{A&B\cr C&D\cr}\mapsto \pmatrix {A&C^T\cr B^T&D\cr}$$ where $A$ and $D$ are square matrices (perhaps of different sizes), $C$ and $D$ are rectangular of appropriate sizes, and the upper-$T$ denotes the transpose.
Jul
9
revised Worst case difference in rank by column-row swapping
added 107 characters in body
Jul
9
revised Worst case difference in rank by column-row swapping
added 17 characters in body
Jul
9
answered Worst case difference in rank by column-row swapping
Jul
7
awarded  Good Answer
Jul
5
comment Which journals publish research announcements?
@SergeiAkbarov: A "research announcement" is a short communication without complete proofs.
Jul
5
comment Worst case difference in rank by column-row swapping
Ah. I see that you've changed your example to respond to my last comment, but without bothering to mention or acknowledge it.
Jul
5
comment Worst case difference in rank by column-row swapping
Your example adds to my confusion. If $S_i$ is the operation that "swaps" the $i$th row and column, and if I understand what "swap" means, then it seems that the $S_i$ commute with each other. But your example suggests that the results of applying $S_iS_j$ and $S_jS_i$ are different. So I'm back to believing that I don't know what "swap" means.
Jul
5
comment Worst case difference in rank by column-row swapping
What does it mean to swap rows for columns? In particular, what is the result of swapping the first row for the second column in $\pmatrix{a&b\cr c&d\cr}$ ?
Jul
4
comment Freedom of speech in scientific discussions - An invitation to more tolerance in Scientific debates
This is not a math question.
Jun
29
awarded  Nice Answer
May
25
comment John Nash's Mathematical Legacy
@IgorKhavkine: I'm the wrong person to ask.
May
24
comment John Nash's Mathematical Legacy
@IgorKhavkine: The paper is basically a list of desiderata for a parellel computer.
May
14
comment Second differences of primes determined by increasing first differences: every positive even integer?
@JonMarkPerry: It would really be better if you answered the question.