3,432 reputation
1715
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location Pisa, Italy
age 25
visits member for 2 years, 8 months
seen Apr 17 at 7:42

Mar
11
awarded  Nice Answer
Mar
5
comment An easy question with integer numbers
Thank you, Barto!
Mar
5
comment An easy question with integer numbers
Thank you very much, Ewan!
Mar
5
accepted An easy question with integer numbers
Mar
5
asked An easy question with integer numbers
Feb
11
awarded  Necromancer
Oct
27
comment When quotient map is open?
If $\pi \colon X \to X/G$ is the projection under the action of $G$ and $U \subseteq X$, then $\pi^{-1} (\pi (U)) = \cup_{g \in G} g(U)$.
Aug
7
awarded  Yearling
Jul
15
answered How to calculate the embedding dimension of this ring
Jul
10
revised Local rank and direct sum decomposition
edited body
Jul
8
answered Local rank and direct sum decomposition
Jul
8
answered Equivalence/Similarity of matrices over domains
Jul
1
comment Infinitely many primary decompositions of an ideal
See Exercise 1 of the chapter about Artin rings in Atiyah-MacDonald.
May
30
awarded  Nice Answer
May
6
awarded  Necromancer
Apr
10
comment Associated Primes of Tensor Product
I think that in general almost nothing can be said. See for example $M =A/I$ and $N = A/J$.
Apr
10
comment Does there exists a continuous surjection from $\mathbb{R}$ to $\mathbb{R}^2$?
I don't know, but continuous is probably too weak as a condition. In fact there is the Peano curve, which is an example of continuous surjection $[0,1] \to [0,1] \times [0,1]$.
Mar
24
answered When do two matrices have the same column space?
Jan
25
comment Similar matrices and field extensions
I have just discovered that my proof is contained also in Problems 7 and 9 of Section 6.7 in Topics in algebra (2nd ed.) by I. N. Herstein.
Dec
6
comment Shrinking the base field of a scheme of finite type over a field
It is true by the theory of limits of schemes of finite presentation: EGA IV §8.