Matthew Pressland
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 Sep 10 reviewed Approve Asymptotic bounds. What software to use? Sep 10 comment Proving that 4 specified sets are not algebraic For 3 and 4, assume $f$ is a polynomial vanishing on your specified set. Then by restricting to each line through the origin (i.e., set $y=\lambda x$ for some $\lambda$, or $x=0$), you can get a bunch of polynomials of one variable, each of which has infinitely many roots, so must be $0$. Thus you can show that $f$ vanishes everywhere. Possibly a similar method can be adapted to the others. Sep 10 reviewed Leave Open A map that is surjective but not injective between infinite dimensional vector spaces Sep 10 reviewed Leave Open A form problem between $S^3$ and $S^2$. Sep 10 reviewed Close A property of rings Sep 10 reviewed Close A ring with few invertible elements Sep 10 answered Show that $\operatorname{Hom}_R(M, -)$ is a functor from the category of $R$-modules to the category of abelian groups. Sep 9 reviewed Reject Rational Points on Elliptic Curves Sep 9 comment Canonical direct product (in a category) It's also then true that such a choice of three pieces of information is unique up to unique isomorphism (once "isomorphism" is defined appropriately), so I'm not sure it's really necessary to single out one choice as canonical. Sep 9 answered Simple Combinatorics Problem Sep 9 comment Simple Combinatorics Problem The question is a little unclear to me on whether one can tell the difference between each of the 5 letters. Concretely, in case 7, are there 5 possibilities depending on which letter is in the second box, or do you consider all of these equivalent? Sep 9 reviewed Leave Closed Why write $\mathrm dx, \mathrm dt$ etc. at the beginning of an integral? Sep 9 reviewed Leave Closed Paradox of Infinity? Sep 9 reviewed Leave Closed The union of kernels is a proper subspace Sep 9 reviewed Leave Closed General Linear Groups with Homomorphisms Sep 9 reviewed Leave Closed Proving a sequence limit. Is this correct? Sep 9 revised Proving a sequence limit. Is this correct? rolled back to a previous revision Sep 9 reviewed Leave Closed Questions on powers of a bijection $f\colon\{1,2,\dots,n\}\to\{1,2,\dots,n\}$ Sep 9 reviewed Leave Closed The irreducibility of determinant Sep 9 reviewed Leave Closed Inductive proof of the closed formula for the Fibonacci sequence