4,319 reputation
21433
bio website ryancreich.info
location Los Angeles, CA
age 31
visits member for 4 years, 1 month
seen 5 hours ago
I am a postdoc at U Michigan (Ann Arbor). I was a graduate student at Harvard, where my advisor was Dennis Gaitsgory, and I graduated in the spring of 2011. In short, I do geometric representation theory, which in the case of my thesis means perverse sheaves on the affine grassmannian with some gerbes thrown in, but could also mean something much more elementary. I'm also active on tex.stackexchange.com.

Jul
19
comment Should all equations which appear in a thesis be numbered?
Doesn't this mean that the hidden numbers will cause gaps in the sequence of explicit numbers?
Jul
2
awarded  Curious
Jun
24
comment The functional equation $f(f(x))=x+f(x)^2$
The images in this answer are hosted on tinypic for now-obsolete historical reasons, and one of them has vanished. If you could, would you re-upload them using the Stack Exchange image tags?
Jun
17
comment Is the following sum irrational?
Of course; I just meant that on its own the result was incomparable with Apery's.
Jun
17
comment Is the following sum irrational?
Not exactly "stronger" (it could be 1, for instance).
Jun
6
awarded  Nice Answer
Jun
4
awarded  Yearling
May
27
awarded  Good Question
May
15
answered In this special situation, does $M \otimes B=0$ imply $M=0$?
May
10
comment Non-continuous higher differentiability, II
Francois' comment reminds me of how, in topology, to define $n$-connected, you first require $k$-connected for all $k < n$. That is, a simply connected space must first be connected, and so on. Most likely whatever hopes you have for this shortcut to twice-differentiability will have this particular problem.
May
6
comment Non-continuous higher differentiability
I sort of doubt this even implies that $f$ is differentiable except at $x$. For example, let $n = 1$, let $w(t)$ be your typical nowhere-differentiable continuous (i.e. Weierstrass) function, and let $f(t) = t^2 + t^3 w(t)$. Then this is "twice differentiable" according to you, but only at $t = 0$.
May
4
comment The half-life of a theorem, or Arnold's principle at work
I can't say I'm surprised. The "physics" of the aether was motivated by electromagnetism, which is inherently a relativistic theory in which the number $c$ naturally appears. The concept of mass-energy (or -aether) equivalence seems plausible given the qualities of both that aether was supposed to possess. Finally, $E = mc^2$ is dimensionally correct (of course) and so getting something that looks like it from the above considerations seems to be not that hard. If so, this is not the only "classical" factor of 2 that Einstein fixed with relativity.
Feb
23
comment Fibrations with isomorphic fibers, but not Zariski locally trivial
Oh, is that what the Brauer group is?
Feb
12
comment Was lattice theory central to mid-20th century mathematics?
+1 for finding a connection between "lattices" and "lattices", not to mention all your other comments.
Jan
6
awarded  Nice Answer
Jan
6
answered Why we need to study representations of matrix groups?
Jan
4
comment Geometric interpretation of the half-derivative?
I can't answer your question, but it reminds me of this one, in whose answer locality of the derivative is obtained from the Leibniz rule.
Jan
2
comment Examples of common false beliefs in mathematics
@Chris As you know, this is not a "real function" to the minds of calculus students.
Dec
18
comment A question on long line
Ah, I did not realize that even a very large "manifold" with a Riemannian metric could be topologically metrized. I was thinking of the obvious definition where you measure the infimum length of piecewise-smooth paths between two points, as computed by arc length, and which obviously doesn't work for a non-path-connected space.
Dec
18
comment A question on long line
The metric gives a local distance, but since the long line is not path-connected, the local distance doesn't compare two arbitrary points.