cactus314
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 Apr 6 asked Let $\theta(z) = \sum q^{n^2}$, is $\theta(-1/z)$ also a theta function? Apr 6 reviewed Close Subgroup half as big as its group is normal. Apr 6 reviewed Leave Open Expand the function $e^{z+\frac{1}{z}}$ in laurent series around the origin Apr 6 reviewed Leave Open Prove {$x|P(x) \land S(x)$}$\cup$ {$x|P(x) \land \neg S(x)$} $=${$x|P(x)$} Apr 6 answered Intuitive explanation for why $\left(1-\frac{1}{n}\right)^n \to \frac{1}{e}$ Apr 6 asked Show that $\mathrm{SO}_3(\mathbb{Q}_p) \simeq \mathrm{SL}_2(\mathbb{Q}_p)$ Apr 4 asked Show that $SO_3(\mathbb{Z}) \simeq SO_3(\mathbb{Z}/3\mathbb{Z})$ Apr 4 comment A set such that $A$, $A+A$ have density zero but $A+A+A$ has positive density. Is that called log density? Not even. Like $\sqrt{\log}$ density. Apr 4 comment A set such that $A$, $A+A$ have density zero but $A+A+A$ has positive density. Finally $d(\square + \square + \square + \square) = 1$ as all positive integers can be expressed as the sum of 4 squares. So what is happening here? Apr 4 asked A set such that $A$, $A+A$ have density zero but $A+A+A$ has positive density. Mar 24 comment $S=\frac{-d^2}{dx^2}$ self-adjoint operator or not? I am a little bit confused by symmetric but not self-adjoint as this could never happen in finite dimensional space Mar 24 answered What does algebraic number look like locally? Mar 24 asked Image of lines under the Cayley Transform $z \mapsto \frac{z-1}{z+1}$ Mar 22 accepted equivalent to $A \to (C \leftrightarrow D)$ Mar 22 comment equivalent to $A \to (C \leftrightarrow D)$ If $A$ is not true, then maybe $C$ and $D$ are not equivalent. In number theory, there are rings where "prime" and "irreducible" are not equivalent. Mar 21 reviewed Approve equivalent to $A \to (C \leftrightarrow D)$ Mar 21 comment Ruler and compass question how is this Galois theory? Mar 21 asked equivalent to $A \to (C \leftrightarrow D)$ Mar 20 revised sum of divisors function $\sum \tau(n) = \frac{1}{4}$ added 755 characters in body Mar 20 comment sum of divisors function $\sum \tau(n) = \frac{1}{4}$ @Gerben Divergent series get hated on in math courses but I trudge on since I see them so often in physics courses.