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Jul
16
awarded  Favorite Question
Jun
23
awarded  Yearling
Jun
23
awarded  Nice Answer
Jun
2
awarded  abstract-algebra
May
26
comment Type of singularity of $\sin(z)/z^3$ at $0$
What is the Taylor expansion of $\sin z$?
May
23
comment Is there a “ping-pong lemma proof” that $\langle x \mapsto x+1,x \mapsto x^3 \rangle$ is a free group of rank 2?
@Paul I don't know anything about arithmetic dynamics (or geometric group theory for that matter), but I agree with you that it's a nice question with an arithmetic flavor to it. Cheers!
May
23
comment Is there a “ping-pong lemma proof” that $\langle x \mapsto x+1,x \mapsto x^3 \rangle$ is a free group of rank 2?
@Martin Sure, but $x^{1/3}$ is not a polynomial. I just thought it should be made clearer in the statement of the question that $f$ and $g$ are to be thought of as automorphisms of $\mathbb R$, and not as polynomials.
May
23
comment Is there a “ping-pong lemma proof” that $\langle x \mapsto x+1,x \mapsto x^3 \rangle$ is a free group of rank 2?
What is the inverse of $x \mapsto x^3$?
May
23
comment Multiplying two tensors of the Levi-Civita type
You should explain your notation. What are $\epsilon, \sigma, \mu, \nu, \rho, \rho', \sigma', \delta$?
May
23
comment Is there an object in reality that is proven to be uncountable?
I certainly couldn't; or, at least, not without being a smartass.
May
23
comment Is there an object in reality that is proven to be uncountable?
Technically speaking, isn't the number $200^{200^{200}}$ itself a set with exactly $200^{200^{200}}$ elements? :)
May
23
revised Are closed simple curves with this property necessarily circles?
rolled back to a previous revision
May
23
answered Does the sum of the Zeta function taken on natural numbers converge?
May
23
answered Is $\mathbb{Z}[2\sqrt{2}]$ a PID?
May
22
comment On the expression of the Galois conjugates in terms of the coordinates in a basis
@Stabilo My pleasure
May
22
answered On the expression of the Galois conjugates in terms of the coordinates in a basis
May
22
comment How do I compute the norm of a non-principal ideal of the ring of integers of a quadratic field without using ''large'' results
The bar denotes the nontrivial automorphism of $\mathbb Q(\sqrt{15})$, sending $\sqrt{15}$ to $-\sqrt{15}$; it is not complex conjugation.
May
22
comment How do I compute the norm of a non-principal ideal of the ring of integers of a quadratic field without using ''large'' results
What makes you think that $I^2$ should be a priori principal? $I^2$ and $I\overline{I}$ are not the same ideal...
May
19
answered Number field attached to a finite group.
May
19
answered What is the motivation for complex conjugation?