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Feb
2
comment Spectral radius and dense subspace
$f = A$, I presume?
Feb
2
answered If $(z_{n}) \in \mathbb{C}$, $z_{n} \to \infty$ as $n \to \infty$, what happens to $|z_{n}|$, $Re(z_{n})$, $Im(z_{n})$, $Arg(z_{n})$?
Feb
2
comment Prove that $A - B$ is closed if $A$ or $B$ is bounded (or both)
Those counterexamples are not convex. However, you can try $\{(x,y):\; x>0, y > 0, xy \ge 1\}$ and $\{(x,y): \; x < 0, y > 0, xy \le -1\}$.
Feb
2
comment How does one prove that $2\uparrow\uparrow16+1$ is composite?
Noble Mushtak : "The rest of the Fermat numbers we know are composite"?. No. We know the other Fermat numbers up to $F_{32}$, and some others, are composite. As far as we know, all sufficiently large Fermat numbers could be primes.
Feb
1
comment Choosing a function inside an integral so as to remove the dependence on a particular variable
You can certainly take $f(y,x) = 0$, but I suppose you want less trivial solutions.
Feb
1
comment Choosing a function inside an integral so as to remove the dependence on a particular variable
Is $t$ fixed or variable? Are you assuming $y \ge t$? Your $f$ and $g$ can't really be completely arbitrary, because you want the integral to exist (perhaps as an improper Riemann integral). What differentiability assumptions are you willing to make?
Feb
1
answered Limit of $h(x)= \frac{f(x)}{g(x)}$
Feb
1
answered How many numbers between $0$ and $1,000,000$ have exactly one digit equal to $9$ and the sum of digits equal $13$?
Feb
1
answered P-adic norm/valuation of n!
Jan
31
awarded  approximation
Jan
29
comment How can define analytic function on simply connected domain?
It doesn't. The more turns of the spiral, the bigger an interval you need.
Jan
29
revised How can define analytic function on simply connected domain?
added 241 characters in body
Jan
29
comment Reformulation of Goldbach's Conjecture as optimization problem correct?
This is related to the postage stamp problem. Some estimates are known there. In particular, the Challis paper says, if I interpret it correctly, that with a set of $n$ positive integers you can get all positive integer sums up to $2 n^2/7$.
Jan
29
comment Reformulation of Goldbach's Conjecture as optimization problem correct?
I used an SMT solver (z3).
Jan
29
comment Reformulation of Goldbach's Conjecture as optimization problem correct?
There's nothing special about the primes. For example, you can represent every even number from $4$ to $56$ as the sum of two (not necessarily distinct) members of $\{ 2,4, 8, 12, 16, 18, 36, 38\}$, a set of cardinality 8. You can't do it with a set of $8$ primes: you need at least $10$.
Jan
29
comment Reformulation of Goldbach's Conjecture as optimization problem correct?
There are many sets $A$ of integers such that $A + A$ contains all even integers. All are countably infinite, of course, so there's nothing special about the primes there.
Jan
29
answered How can define analytic function on simply connected domain?
Jan
29
answered Is the following fractional function convex?
Jan
29
answered Polynomial with bounded coefficients and real root
Jan
28
comment relation between equallity of hermitian parts and numerical range
The numerical range is the set of $x^\star M x$ for all $x$ with $x^\star x = 1$. $x^\star A_H x$ is the real part of $x^\star A x$. So what depends only on the Hermitian part is the projection of the numerical range on the real axis.