13,480 reputation
13366
bio website zakuski.math.utsa.edu/~jagy
location Berkeley, California
age 57
visits member for 4 years, 3 months
seen 3 hours ago
My main activity is in number theory of integral positive ternary quadratic forms. This began through years of working with Irving Kaplansky. Much of his unpublished writing on quadratic forms can be found as pdfs at http://zakuski.math.utsa.edu/~kap/forms.html and about Lie and Jordan superalgebras at http://zakuski.math.utsa.edu/~kap/superalgebra.html One of my own email addresses can be found easily using the search feature at http://www.ams.org/cml and just putting in my last name

Apr
8
awarded  Notable Question
Mar
30
comment Are there nontrivial real functions of 2 real variables with gradient having constant euclidian norm on each level line?
mathoverflow.net/questions/82227/…
Mar
30
comment Are there nontrivial real functions of 2 real variables with gradient having constant euclidian norm on each level line?
en.wikipedia.org/wiki/Eikonal_equation
Mar
27
comment One Diophantine equation
I do not understand most of what you say; I suppose English is not your first language. It is certainly possible to describe some solutions of Apollonian circle packing with formulas. There will always be many other solutions that are not described by those formulas.
Mar
27
comment One Diophantine equation
no formula describes all solutions. Also, you don't seem to have asked any question.
Mar
27
comment One Diophantine equation
en.wikipedia.org/wiki/… The solutions are a forest of countably many rooted trees. See articles in the AMS Bulletin by Fuchs and Kantorovich.
Mar
24
comment Database of non-isomorphic trees
@BrendanMcKay, good point. But see the (American edition) cover of Interesting Times, by Terry Pratchett: Not tested on animals, you'll be the first! amazon.com/Interesting-Times-Discworld-Terry-Pratchett/dp/…
Mar
24
comment Database of non-isomorphic trees
Start one. You'll be the first!
Mar
23
comment Surface curves equidistant from a simple closed geodesic
Right. for Q2, cannot imagine all geodesics unless it is a cylinder over a plane curve.
Mar
22
comment Surface curves equidistant from a simple closed geodesic
Alright, one approach with a reference, en.wikipedia.org/wiki/…
Mar
22
comment Surface curves equidistant from a simple closed geodesic
similar to Morse functions, really, and some similar to the cut locus of a point. From an ellipsoid, note that the farthest point (Q4) need not be the same distance from all points of $\gamma,$ although perhaps from two points, otherwise a small movement could take it a hair farther. In general, though, thinking of hydra heads, en.wikipedia.org/wiki/…
Mar
21
comment Asymptotics of special square-free numbers
Thank you. So, the "most integers near $x$" would be Erdos-Kac. en.wikipedia.org/wiki/Erd%C5%91s-Kac_theorem
Mar
21
comment Asymptotics of special square-free numbers
@IstvánKovács, see the comment of Greg Martin after yours, then mine...
Mar
21
comment Asymptotics of special square-free numbers
@GregMartin, thanks. It seems to me, reading Lucia's comment, that Montgomery and Vaughan are saying exactly the same thing as Hardy and Wright. Maybe you could leave an answer with some detail about the error term, which i guess is the approximate size of H+W's $\tau_k(x) - \pi_k(x).$
Mar
21
comment Asymptotics of special square-free numbers
@IstvánKovács, not sure what to tell you; they say the result is the same for $\tau_k(x),$ where $k$ is the exponent sum and there is no longer a restriction to be squarefree. So for that interpretation, a sum of 1 seems correct. Well, I will leave it here, someone will explain the difficulty. I don't have Montgomery and Vaughan.
Mar
20
answered Asymptotics of special square-free numbers
Mar
20
comment Discriminant of a compositum of number fields, a bound?
math.stackexchange.com/questions/719377/…
Mar
20
comment Is there a Hotel California of set-theoretic geology?
@Erin, no, I just thought your question was amusing. With any luck Noah will give more detail. If you can wait, there are a variety of other people who can offer substantial answers. On one detail, a couple i know in England just came back from Tenerife. Maggie took pictures of the sardine and put it on facebook.
Mar
20
comment Is there a Hotel California of set-theoretic geology?
I guessed. Every year they have a funeral for a sardine. en.wikipedia.org/wiki/Carnival_of_Santa_Cruz_de_Tenerife
Mar
20
comment Is there a Hotel California of set-theoretic geology?
You've been deprived in some way, right? Could we take up a collection, give you a round trip to Tenerife? I hear good things.