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3h

comment 
Worst case difference in rank by column and row substitution
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 $\pmatrix{a&b\cr c&d\cr}$ ? 
19h

comment 
Freedom of speech in scientific discussions  An invitation to more tolerance in Scientific debates
This is not a math question. 
Jun 30 
comment 
Example of a ring with infinitely many zero divisors and finitely many invertible elements
How should we understand the notation $f(x):=3$ when $x$ appears only on the left hand side? 
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. 
May 14 
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Second differences of primes determined by increasing first differences: every positive even integer?
@JonMarkPerry: Ah, thanks for clarifying $p_1$ and $p_2$  I had indeed missed the fact that these were arbitrary. I'm still not clear on where they're supposed to be ramified. 
May 14 
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Second differences of primes determined by increasing first differences: every positive even integer?
@JonMarkPerry ?? Ramified where? And for that matter, what are $p_1$ and $p_2$? 
May 12 
revised 
What can I further assume about the speeds of runners of Lonely Runner Conjecture WLOG?
defined notation to render post comprehensible. 
May 6 
awarded  Excavator 
May 6 
revised 
How to recognise that the polynomial method might work
deleted 3 characters in body 
Apr 26 
comment 
Google question: In a country in which people only want boys
A tiny correction, years later: In the fourth comment, $(1)^k$ should be $(1)^{k+1}$. 
Mar 9 
comment 
How to prove that any perfect complex on an affine scheme is strictly perfect?
I might be mistaken, but I'd have thought that the usual definition of "strictly perfect" (as found in, say, SGA6) would replace your "complex of finite rank free sheaves" with a complex of finite rank locally free sheaves. This would rule out Fernando's counterexample. 
Mar 9 
answered  What is $K_2(\mathbb{Z}[x,x^{1}])$? 
Mar 4 
comment 
Communal problem books
Perhaps at least marginally relevant: thebigquestions.com/papers/jimmys.pdf 
Mar 3 
awarded  Popular Question 
Mar 3 
awarded  Nice Question 
Mar 3 
asked  Do the real numbers “know” that they are countable in a larger model? 
Feb 5 
comment 
map in Ktheory
At the level of rings, this is the map $K_n(R)\mapsto K_n(R/I)$ given by taking the class of a projective $R$module $[P]$ to the class of the (finite projective dimension) $R/I$module $P/IP$. (Take the alternating sum of the classes of the projective modules occurring in a projective resolution of $P/IP$.) The reason you need smoothness is to insure that $P/IP$ has finite projective dimension so that this class is well defined. 