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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.