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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.