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stablemap

11,562 karma · joined September 17, 2016

stablemap@icloud.com
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stablemap··on Elliptic Curves
I should have said real manifolds; I thought that was what the parent comment had in mind but the brevity wasn't worth it.

Of course, I've learned a lot about these things from your writings.

stablemap··on Elliptic Curves
I would expect him to spell this out in lectures 15 and 16. It does take work. What is surprising is that despite their all looking the same -- certainly they are the same as real manifolds -- there are tons of elliptic curves. The difference is in the complex analytic structure.
stablemap··on Elliptic Curves
It believe mathematicians will continue to favor boards. Sitting in the audience I greatly prefer this; however, such lectures have less chance of being posted at all.

For this topic we are lucky to have Silverman's book [1], which everyone seems to like.

[1] https://www.math.brown.edu/~jhs/AECHome.html

stablemap··on The Corporate Contradictions of Neoliberalism
One example:

http://www.bradford-delong.com/2016/03/the-benefits-of-free-...

stablemap··on Clojure Linear Algebra Refresher: Eigenvalues and Eigenvectors
It is probably logically unnecessary but I think it's best to have experience with the "computational" aspects of linear algebra before diving into Axler's book.
stablemap··on Clojure Linear Algebra Refresher: Eigenvalues and Eigenvectors
What he gives is the identity matrix—multiply on the right by any 2x1 vector and you will get that vector back. So any such vector, provided it is not the zero vector, is an eigenvector with eigenvalue 1.
stablemap··on Smart Reply in Gmail
There's also a post, which this links at the end, describing algorithmic improvements:

https://research.googleblog.com/2017/05/efficient-smart-repl...

stablemap··on Why Are Economists Giving Piketty the Cold Shoulder?
I thought the author would mention the new collection of essays After Piketty: The Agenda for Economics and Inequality, particularly since he is one of the editors.

http://www.hup.harvard.edu/catalog.php?isbn=9780674504776

stablemap··on Why is Russia so good at encouraging women into tech?
I hesitate to hold up mathematics as a good example. There are an encouraging number of female majors but further down the pipeline the numbers get much worse. For tenured faculty positions the latest number [1] I've seen is 14%.

[1] http://www.ams.org/profession/data/annual-survey/

stablemap··on MathJax CDN shutting down on April 30, 2017
Was this the case in 2011 when MathJax began offering this? I don't know the answer.
stablemap··on Mathify – Simple Text Equation to LaTeX
Often I do want to output x/3; is there a way to do that here?
stablemap··on Abstract Algebra (2016) [pdf]
Gross links to this archive, which has more material:

http://wayback.archive-it.org/3671/20150528171650/https://ww...

stablemap··on What does it feel like to invent math? (2015) [video]
My short advertisement is that it has proven very useful to study Diophantine equations by reducing mod n. The Chinese remainder theorem [1] tells you to focus on reducing mod p^r, where p is a prime. If r = 1 then you are working in a field but in the ring Z/4, for example, I know 2 ≠ 0 and yet 2·2 = 0.

To make the p-adics Z_p I stitch all of these Z/p^r together: an element is a choice of a_r in each Z/p^r and these have to be compatible: a_2 reduces mod p to a_1 and so on. The resulting Z_p has no "zero divisors", and if I allow myself to invert p I get a field Q_p.

This is a huge improvement, a foundation on which to build analysis and geometry as we did over R.

[1] https://en.wikipedia.org/wiki/Chinese_remainder_theorem

stablemap··on The Fundamental Theorem of Algebra: A Visual Approach [pdf]
Look at the end, past the bibliography.
stablemap··on The Fundamental Theorem of Algebra: A Visual Approach [pdf]
Apart from the typesetting, is this different from this submission from earlier in the day?

https://news.ycombinator.com/item?id=13686519

stablemap··on The Fundamental Theorem of Algebra: A Visual Approach (2015) [pdf]
There's a big list of proofs on MathOverflow [1]. Not a lot of pictures in it but there are many to be drawn.

My favorite is probably top answer: a polynomial f(z) gives you a map from the Riemann sphere ℙ^1 to itself. Topology tells you it's closed and analysis tells you it's open because locally a holomorphic map always looks like z^n. It follows that the map is surjective.

[1] http://mathoverflow.net/questions/10535/ways-to-prove-the-fu...

stablemap··on How CS50 at Harvard uses GitHub to teach computer science
I wouldn't read too much into the number. Their department claims that Math 55, for example, is the hardest undergraduate math class in the country and I believe them.
stablemap··on The Wall Street Journal to Close Google Loophole Entirely
It's not as obvious as I'd remembered. I think these instructions work:

http://help.washingtonpost.com/link/portal/15067/15080/Artic...

stablemap··on The Wall Street Journal to Close Google Loophole Entirely
Maybe this doesn't count as supporting, but: you also get free access with a .edu, .gov, or .mil email address.
stablemap··on The Axiom of Choice Is Wrong (2007)
Maybe I'm missing your point, but for δ I think the hack is using the word "function"; as a measure or distribution it's a pedestrian object.
stablemap··on A Bitter Ending
It's focused on the resulting economics but I've heard great things about the book Misbehaving by Thaler. The remarks under "Outtakes" here give some context:

http://www.misbehavingbook.org

stablemap··on To Live Your Best Life, Do Mathematics
The Wayback machine does not absolve me—probably I just missed it twice. Thank you.
stablemap··on To Live Your Best Life, Do Mathematics
Everyone I know who went to his MAA farewell address said it was wonderful. Definitely follow their link to read or hear the whole thing:

https://mathyawp.wordpress.com/2017/01/08/mathematics-for-hu...

stablemap··on White House discussing asking foreign visitors for social media and phone contacts
I appreciate that the proposal [1] was put out for comments half a year before its implementation last month, although I wonder what comments it would have taken to get this thing reversed. "Optional" is a menacing word here—has anyone followed up on this?

[1] https://www.federalregister.gov/d/2016-14848

stablemap··on Whiteboard sticker for your laptop
It seems to me that the logo is a second sticker.
stablemap··on I emailed my Senators regarding Net Neutrality this is their responses
I've heard ex-staffers say that emails are worthless but calls—in volume, as you say—have an impact.
stablemap··on Safari 10.1
Yes, sorry: I was afraid of changing the given title and there's nothing new here if you run purple Safari. I assume they put this up to go along with the public betas for macOS 10.12.4 and iOS 10.3. I don't get much out of the release notes attached to the tech previews so this was welcome to me.
stablemap··on About the irrationality of e=2.718... (1840)
I don't have any recommendations, but they do exist:

http://mathoverflow.net/questions/22141/how-do-i-see-latex-m...

stablemap··on About the irrationality of e=2.718... (1840)
Maybe it's better to write his equation as ae² - ce + b = 0. The proof would say that e isn't degree ≤ 2 over the rationals.
stablemap··on About the irrationality of e=2.718... (1840)
I still see this, particularly when it would be awkward to create a new symbol: "when the discriminant is ≤ 1". I feel that Halmos [1] wouldn't have liked it, but it does lessen the distance between what is written and the equation the reader will want to have in his mind.

[1] http://www.math.washington.edu/~lind/Resources/Halmos.pdf

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