197 reputation
16
bio website
location
age
visits member for 3 years, 4 months
seen Jun 6 '13 at 9:03

Jul
2
awarded  Curious
Oct
8
asked How do I break MAGMA?
Oct
5
accepted How to iterate over power set in MAGMA?
Oct
5
revised How to iterate over power set in MAGMA?
added 141 characters in body
Oct
5
asked How to iterate over power set in MAGMA?
Sep
11
accepted Picking out columns from a matrix using MAGMA
Sep
9
asked Picking out columns from a matrix using MAGMA
May
23
revised Extending an ideal of a polynomial ring to a polynomial ring with more indeterminates. Is it a tensor product?
deleted 85 characters in body
May
16
accepted Is the image of a tensor product equal to the tensor product of the images?
May
16
comment Is the image of a tensor product equal to the tensor product of the images?
Thanks a lot for great answer. I don't quite see what the unique injection $\mathbb{Z}/2\mathbb{Z}\rightarrow\mathbb{Q}/\mathbb{Z}$ is though...could you please tell me? And what if all the modules $A,A',B,B'$ are free $S$- modules (even finitely generated), do we then have $$\operatorname{im}(\phi\otimes\psi)=\operatorname{im}(\phi)\otimes_{S}\operator‌​name{im}(\psi)?$$
May
16
asked Is the image of a tensor product equal to the tensor product of the images?
May
5
comment Showing that the Taylor series of $f(x)=\frac{1}{\sqrt{1+x}}$ converges to $f$ on (I think) the interval (-1,1].
Well, thanks a lot. This is a first year calculus exercise though, and neither complex analysis nor binomial coefficients involving non-natural numbers are part of the curriculum...far from it:)
May
5
asked Showing that the Taylor series of $f(x)=\frac{1}{\sqrt{1+x}}$ converges to $f$ on (I think) the interval (-1,1].
May
5
accepted Manipulation of some power series (probably integration or derivation).
May
4
comment Manipulation of some power series (probably integration or derivation).
Well, but using the series for $ln(1+x)$ and $ln(1-x)$ together with $\ln(a/b)=\ln(a)-\ln(b)$, which I had already tried, doesn't yield the deisred identity. I am pretty sure one is supposed to use the sum for $\frac{1}{1-x^2}$ mentioned above. And the absolute values, pointless though they are, I think may be a hint that one is supposed to integrate both sides of something, since \integral 1/y = ln|y| + C. But I still have no idea how to solve this exercise.
May
4
asked What happens to the sequence $a_n=\frac{3\cdot5\cdot7\cdot\ldots\cdot(2n-1)}{2\cdot4\cdot6\cdot\ldots\cdot2n}$ as $n$ tends to $\infty$?
May
3
asked Manipulation of some power series (probably integration or derivation).
Apr
28
awarded  Commentator
Apr
28
comment When is every spanning tree of a connected graph the union of spanning trees of its subgraphs?
In general, if the proposition holds for some $\{H_i\}$, then it holds for any "coarser partition" of $\{H_i\}$ as well.
Apr
28
comment When is every spanning tree of a connected graph the union of spanning trees of its subgraphs?
Have found some sufficient conditions for this to be true, but no necessary conditions so far. Sufficient, at least, is for each $H_i$ to be a union of blocks of $G$, in such a way that $H_1,H_2,\ldots H_r$ constitute a "partition" of the blocks of $G$. In particular, it holds whenever $H_1,H_2,\ldots H_r$ are the blocks of $G$. Can provide a proof of this if anyone is interested. Have not managed to show that this is a necessary condition (nor to find a counterexample showing that it isn't).