12,337 reputation
11228
bio website faculty.missouri.edu/~stephen
location Columbia, MO
age 51
visits member for 3 years, 1 month
seen 6 hours ago

To find out about me, go to my website. You will probably find out far more than you want to know.


22h
comment An easy example of a non-constructive proof without an obvious “fix”?
@CarlMummert At some intuitive level, I would say that Becher and Figueira give a non-constructive proof of a constructable normal number. At least in the following sense - if I asked them what the hundredth digit of their example is, I think it would take an extremely long time to compute it.
22h
answered An easy example of a non-constructive proof without an obvious “fix”?
Jan
24
comment How to show that exp is a diffeomorphism between symmetric reals and positiv definite matrices?
I think I used an over-complicated way to show it is smooth. Simply use the fact that the local inverse of a smooth, invertible function is itself smooth.
Jan
20
comment A future in mathematics
I would be happy to try to answer your questions. Click on my name, and you will get my email address. (I don't know about elliptic curves though.) Also, have you tried the chat rooms on this website?
Jan
20
answered What's your favorite proof accessible to a general audience?
Jan
13
awarded  Enlightened
Jan
13
awarded  Nice Answer
Jan
1
comment relationship between BMO norm and $L_p$ norm
Thanks, I changed it.
Jan
1
revised relationship between BMO norm and $L_p$ norm
Make last sentence correct.
Jan
1
comment relationship between BMO norm and $L_p$ norm
If I remember correctly - try $f(x) = \log |x|$ on $[-1,1]$, and $g(x) = (\log x) I_{x>0}$.
Jan
1
comment Counter example for Poincare inequality does not hold on unbounded domain
+1 - it's a lot simpler than what I did (even though it is essentially equivalent).
Dec
31
answered Counter example for Poincare inequality does not hold on unbounded domain
Dec
30
awarded  Yearling
Dec
30
comment relationship between BMO norm and $L_p$ norm
Oops - maybe I meant to say that if $0 \le g \le f$, and $f \in \text{BMO}$, this doesn't necessarily mean $g \in \text{BMO}$.
Dec
30
comment Understanding mathematical syntax in SO(3) - Part II
$x^T y$ is a $1 \times 1$ matrix, which is interpreted as a scalar.
Dec
30
revised Prove an identity using differential calculus to a problem connected to fluids
v -> mathbf v
Dec
30
comment Prove an identity using differential calculus to a problem connected to fluids
@abel Bernoulli's equation is $\partial v/\partial t + \omega \times v = -\nabla (p + \frac12 v^2)$, where $\omega = \text{curl} \,v$. I might be wrong on the first $+$, but the second $+$ is definitely a $+$ and not a $-$.
Dec
30
revised Prove an identity using differential calculus to a problem connected to fluids
deleted 1 character in body
Dec
30
answered Prove an identity using differential calculus to a problem connected to fluids
Dec
30
comment Understanding mathematical syntax in SO(3) - Part II
I don't see the problem here. Your definition is compatible with $\text{trace}(\hat x \hat y) = -2 x^T y$. Just multiply out the left hand side in detail, and you will see that it is correct.