Brandon Carter
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 Apr 26 comment Euler characteristic is the alternating sum of dimensions of the homology There are other possible definitions, e.g. as the alternating sum of the number of $n$-simplices/cells. Did your instructor give an alternate definition? Apr 26 comment What is the $\lim _{x→\infty}(0.5)^x$? $|x| < 1$, not $x < 1$. Apr 24 comment Fermat's little theorem's proof for a negative integer Can you think of a way to get an $a^p$ term from that last equation? Apr 24 comment Fermat's little theorem's proof for a negative integer Hint: If $a$ is negative, then $-a$ is non-negative, so $(-a)^p \equiv -a \pmod{p}$. Apr 13 reviewed Close Is quotient of a matrix group still a matrix group? Apr 13 reviewed Leave Open Prove little-o example Apr 13 reviewed Close How to derive identities Apr 13 reviewed Close Showing that $\langle x,y\rangle^2 \subsetneq \langle x,y^2\rangle$ Apr 13 reviewed Close Index and Normal Subgroups? Apr 13 reviewed Close Reducibility of $x^2+1$ in $\mathbb{Z}_n[x]$ Apr 8 comment Does sum of the reciprocals of all the composite numbers converge? You have a lower bound given by the sum of all reciprocals of even numbers bigger than 2, which is essentially half of the harmonic series. So it must diverge. Apr 4 reviewed Close prove homogeneous markov chain Apr 4 reviewed Close $a^2=e~\land~a\ast b^2\ast a=b^3\implies b^5=e~~\textrm{for }(G,\ast)~$? Apr 4 comment Show $(x,y) \rightarrow (x,-y)$ is a group homomorphism? What kind of background do you have? There are several different ways to show this, but some will fit better than others depending on where you encountered this problem. Mar 30 comment Proof of Kummer's Lemma in S. Langs 'Cyclotomic fields' @nguyenquangdo The question asked why showing $\mathbf{Q}(\zeta_p, u^{1/p})/\mathbf{Q}(\zeta_p)$ is unramified is enough. You need the condition that $u$ is congruent to an integer mod $p$ to actually show that it's unramified. Mar 29 answered Proof of Kummer's Lemma in S. Langs 'Cyclotomic fields' Mar 28 comment Translating from (short) Weierstrass form to a Lattice. Integrate the invariant differential against elements of $H_1(E(\mathbf{C}), \mathbf{Z})$ to recover the (period) lattice. Mar 26 answered What does extra zero of an $L$-function mean? Mar 20 comment The module $\Omega^1_{\mathcal{O}_E|\mathbf{Z}}$ It's annihilator is exactly the different ideal, which gives you almost all ramification information (everything except for wild ramification). Mar 18 comment Equivalence of two definitions of rational equivalence They aren't equivalent in general (the first definition is incorrect). See the answer to this post on MO.