Search Results
Search type | Search syntax |
---|---|
Tags | [tag] |
Exact | "words here" |
Author |
user:1234 user:me (yours) |
Score |
score:3 (3+) score:0 (none) |
Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
Views | views:250 |
Code | code:"if (foo != bar)" |
Sections |
title:apples body:"apples oranges" |
URL | url:"*.example.com" |
Saves | in:saves |
Status |
closed:yes duplicate:no migrated:no wiki:no |
Types |
is:question is:answer |
Exclude |
-[tag] -apples |
For more details on advanced search visit our help page |
Commutative rings, modules, ideals, homological algebra, computational aspects, invariant theory, connections to algebraic geometry and combinatorics.
10
votes
Why we can analytically define $ε$ in dual numbers so to distinguish $ε$ from $-ε$ but canno...
The short answer is "because you are considering $\mathbb{C}$ and $\mathbb{R}[\epsilon]$ them with different structure", which is an artificial choice.
Maybe to illustrate the point : If I want to wor …
7
votes
1
answer
233
views
Functions on Stone spaces as "enveloping algebra" of Boolean algebra
I'm looking for references for the following closely related facts:
Given a Boolean algebra $B$, I denote by $\mathbb{Z}[B]$ the free ring generated by symbols $e_b$ such that $e_b e_{b'} = e_{b \cap …
12
votes
Does the category of local rings with residue field $F$ have an initial object?
I will show that this is not the case for $F=\mathbb{F}_9$. The proof generalize to any $\mathbb{F}_{p^k}$, with $k >1$.
I'm starting from the observation that:
$\mathbb{F}_9 \simeq \mathbb{Z}[i]/(3) …
20
votes
Accepted
What is a module over a Boolean ring?
Theorem: Given $A$ a boolean ring/boolean algebra then there is an equivalence of categories between the category of $A$-modules and the category of sheaves of $\mathbb{F}_2$-vector spaces on Spec $A$ …
6
votes
Accepted
Free augmented algebras
For any choice of $\lambda_1,\dots,\lambda_n$ there is an isomorphism:
$$ k[X_1^{[\lambda_1]},\dots,X_n^{[\lambda_n]} ] \simeq k[Y_1^{[0]},\dots,Y_n^{[0]} ] $$
Which is given by $X_i \leftrightarro …
3
votes
Accepted
Matrix diagonalization and eigenvector computation constructively
The following works constructively over an arbitrary local ring $R$ (constructively, $\mathbb{R}$ is a local ring).
Assume that you matrix $M$ is canceled by a polynomial $Q$, of degree $m$ (with lea …
8
votes
How to construct a constructive proof from a non-constructive proof using prime ideals?
Here is a method which is very efficient in the case were "constructive" is interpreted as "no axiom of choice at all, not even countable and no law of excluded middle", i.e. essentially "topos logic" …
3
votes
Accepted
Classification of commutative ring ideal closure operators?
Note that for any such "closure operations" one has $cl(A) = cl(\langle A\rangle)$ where $\langle A\rangle$ denotes the ideal generated by $A$. Hence it can be defined as an operation on ideals.
Now …