186,879 reputation
17129289
bio website
location
age
visits member for 3 years, 9 months
seen 2 mins ago

As somebody used to say:

Does research. Smokes. Battles administration. Smokes. Wishes he could stop battling administration so that he could have more time to do research. Smokes some more.

The same. Except I do not smoke.


How to ask a good question?

This paragraph is for my personal use but freely available:

Welcome to Math.SE! Please, consider updating your question to include what you have tried and where you are getting stuck. That way, people on this site will know exactly what help you need.


2d
reviewed Approve suggested edit on Lyapunov exponent for simple functions
2d
comment Variance of stochastic process $MA(2)$
Got something from the answer below?
2d
comment Prove that $ \lim_{n \to \infty} \frac{\Phi(- \sqrt{n})}{f(\sqrt{n})} = 1$.
Got something from the answer below?
2d
comment A problem on super/sub martingale
It might be a good idea to add your proof (or at least the idea of your proof) that, if X is a super-martingale then |X| is a sub-martingale (a result which seems quite wrong at first sight).
2d
comment Comparing $X^{-1}(E(X| \mathscr{G})(A))$ and $A$
Got something from the answer below?
2d
revised Find all natural numbers n for which $3^n + 5^n$ is divisible by $3^{n-1} + 5^{n-1}$
added 38 characters in body
2d
answered Find all natural numbers n for which $3^n + 5^n$ is divisible by $3^{n-1} + 5^{n-1}$
2d
comment I know by Fubinis theorem that $N$ is $\mathcal E$-measurable and $\mu(N)=0$. How can I see that $N \neq X$, that is $N \subset X$?
If $N=X$ then $\mu(X)=0$ hence $\mu=0$. If $\mu=0$, then every $f$ is integrable for $\mu\otimes\nu=0$ hence $N$ may be any subset of $X$. You probably want to exclude this degenerate case.
2d
comment Find this maximum of this $\frac{\int_{0}^{\pi}f(x) \, dx}{\int_{0}^{\pi} f(x)\sin x\,dx}$
Yet again another unmotivated question with zero personal input.
2d
answered Find this maximum of this $\frac{\int_{0}^{\pi}f(x) \, dx}{\int_{0}^{\pi} f(x)\sin x\,dx}$
2d
answered Finding the ACVF
2d
comment Confusion with a proof about the continuity of convex functions
It should not be possible (otherwise the result is wrong), which is why one should either assume that $$||\textbf{x}-\textbf{x}^*||\leq\delta' \;\;\rightarrow \;\; \textbf{x}\in \text{int}S,$$ or that, for some $\delta''$, $$||\textbf{x}-\textbf{x}^*||\leq\delta'' \;\;\rightarrow \;\; \textbf{x}\in S$$ and then consider $\delta'\lt\delta''$.
2d
answered Confusion with a proof about the continuity of convex functions
2d
answered Why is the expected value of $|X|^p$ equal to $p\int_{0}^{\infty}y^{p-1}\mathbb{P}(|X|>y) dy$?
2d
comment Expectation of a powered complex circular gaussian process
Try x=2u+iv for (u,v) i.i.d. standard normal, then E(x^2)=3.
2d
revised Lyapunov exponent for simple functions
added 4 characters in body
2d
comment Expectation of a powered complex circular gaussian process
Then this fails, already for n=2.
2d
comment Finding a constant from a continuous distribution
"Using your above constant we get..." No, we get $\Pr(X≤x)=θ^{−x}/2$ if $x<0$.
2d
comment $X$ normally distributed in $\mathbb R^n$ iff components $x_i$ normally distributed?
If X1 is normal and X2=X1 then (X1,X2) is normal. Having a positive covariance matrix is not a prerequisite to be normal.
2d
comment Expectation of a powered complex circular gaussian process
Please define "non-circular".