Andrea Mori
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 Apr17 reviewed Close Intersection and Union of a random variable $X$ put in the form of $\{X\in A\}$ for an appropriate $A\subset\mathbb R$? Apr17 reviewed Leave Open Prove that $2n + m \equiv 0 \pmod3$if and only if $n \equiv m \pmod3$ Apr17 reviewed Leave Open The exceptation of a null space of a Gaussian vector is zero or not? Apr8 reviewed Reopen How to study math to really understand it and have a healthy lifestyle with free time? Apr8 reviewed No Action Needed If $K$ and $H$ are subgroups of $G$ and $H \triangleleft K$ then $K \subseteq N(H)$. Apr8 reviewed Leave Open Show that $\mathbb{Z}$ and $2\mathbb{Z}$ are not isomorphic as rings. Apr8 answered What is the difference between ring homomorphism and module homomorphism? Mar23 comment Prove that $|H|$ is odd and $|G/H|$ = $2^n$ for some positive integer n Using Cauchy for 1 is overkilling! Pair elements with their inverses. Since $1_G$ is paired with itself a parity check shows immediately that there must be an other element paired with itself. For 2, yes, $\bar g=gH\in G/H$. Mar23 revised Prove that $|H|$ is odd and $|G/H|$ = $2^n$ for some positive integer n deleted 2 characters in body Mar23 answered Prove that $|H|$ is odd and $|G/H|$ = $2^n$ for some positive integer n Mar23 awarded Nice Answer Mar20 answered Show that $a - b \mid f(a) - f(b)$ Mar20 comment Show that $a - b \mid f(a) - f(b)$ What is $f$? What are $a$ and $b$? Mar16 answered Is it a coincidence that $\mathbb{Z_{12}}$ has all distinct subgroups that are factors of 12? Mar9 awarded Nice Answer Mar6 answered Relation between rank of matrix over $K$ and over $L\supset K$ Mar6 answered Is there any hope to solve the game chess? Mar6 comment Are there any limit to the total amount of moves in chess? To put that in perspective tournament chess games rarely reach move 100. In the entire history of master level chess not more than a handful games, if any, reached move 200 Mar6 answered For every $n \in \mathbb Z^+$ , does there exist a ring automorphism $\psi$ on $\mathbb C[x]$ of order $n$? Mar2 revised Relationship between a vector space V and it's dual space V* deleted 1 character in body