43,693 reputation
14185
bio website zakuski.utsa.edu/~jagy
location Berkeley, CA
age 58
visits member for 3 years, 7 months
seen 34 mins ago

I put an email address here and intended it to be visible. In case it is not, search with my last name at http://www.ams.org/cml/

See me at http://mathoverflow.net/users/3324/will-jagy

and http://zakuski.utsa.edu/~jagy/ and

http://zakuski.math.utsa.edu/~kap/forms.html and

http://arxiv.org/find/math/1/au:+Jagy_W/0/1/0/all/0/1

If people would include the source of a given problem as part of the process of posting a question, life would be a little easier.


2h
revised How many primes can be represented in JavaScript?
added 17 characters in body
2h
answered How many primes can be represented in JavaScript?
3h
comment Proof If $A_{2x2}$ and $\lambda$ real number then $|\lambda I-A|=\lambda^2-(\operatorname{tr}A) \lambda+|A|$
I once told a student the analogous calculation for 3 by 3 matrices, he said "why didn't you tell us that?!" Easier than putting in the $\lambda$ and doing a determinant with symbols. On the other hand, not worth worrying about for 4 by 4 or bigger
3h
comment Fundamental group of sphere with two holes
what is the fundamental group of the plane with one point removed?
20h
comment How to create a computationally cheap function passing through given points?
usually begin with a log-log plot. Right now there is no reason to think polynomials are involved.
1d
comment primes of the form $4k+3$ and sums of squares
@GrigoryM, in case you notice these... we also say "anisotropic" for milder conditions such as this: if $x^2 + 3 y^2 \equiv 0 \pmod 9,$ then both $x,y$ are divisible by $3.$ I imagine, not sure, that people discussing this in the language of quadratic fields would distinguish between unramified and ramified things of some sort. Similar for $x^2 + 27 y^2 \equiv 0 \pmod {81}$
1d
revised primes of the form $4k+3$ and sums of squares
added 92 characters in body
1d
comment primes of the form $4k+3$ and sums of squares
@GrigoryM, no, it is different from that one. There is a name for this property, the quadratic form $x^2 + y^2$ is "anisotropic" in $\mathbb Q_p.$ This question has also been asked many, many times, of course. For example, this shows that integers cannot solve $x^2 + y^2 = 21,$ even though $21 \equiv 1 \pmod 4.$
1d
revised primes of the form $4k+3$ and sums of squares
added 245 characters in body
1d
answered primes of the form $4k+3$ and sums of squares
2d
revised Is every sufficiently large positive integer of the form $ab + ac + bc + 1$?
added 171 characters in body
2d
answered Is every sufficiently large positive integer of the form $ab + ac + bc + 1$?
Dec
19
comment The metric and Kronecker's delta
Once the order all matches up properly, then you just replace the $w$ back into $u$ again.
Dec
19
comment The metric and Kronecker's delta
unfortunate repeating the exact same indices; to me it seems it was multiplied by $g_{wu}$ and summed over $u.$ Then it would be pairs $wv.$ If that is not quite right, try variants.
Dec
19
comment Prove the Schwarz inequality using $ 2xy \leq x^2 + y^2 $
There is no Swartz. There are two famous mathematicians with similar spelling. Absolutely no idea what inequality you might mean. Could be this en.wikipedia.org/wiki/Cauchy%E2%80%93Schwarz_inequality
Dec
19
awarded  Constituent
Dec
19
revised If $(m,n)\in\mathbb Z_+^2$ satisfies $3m^2+m = 4n^2+n$ then $(m-n)$ is a perfect square.
added 189 characters in body
Dec
19
comment Can anyone explain this quote about how mathematicians think?
vserver1.cscs.lsa.umich.edu/~crshalizi/reviews/wolfram
Dec
17
revised How many smooth functions are non-analytic?
added 125 characters in body
Dec
17
comment Is there any pattern to pythagorean triples where there are two a-b pairs for one c?
Easiest are $c=pq,$ with two different prime $p \equiv q \equiv 1 \pmod 4$