All Questions
14 questions
25
votes
1
answer
3k
views
A preprint of Sela concerning the work of Kharlampovich-Miyasnikov
Yesterday, Z. Sela published a preprint in arXiv which claims that the solution of Olga Kharlampovich and Alexi Miyasnikov for the Tarski problem on decidablity of the first order theories of free ...
- 2,233
14
votes
2
answers
725
views
Are there any non-conjugation "extendible automorphisms" in the category of finite groups?
Let $\mathbf{Grp}$ be the category of groups. Given a subcategory $\mathscr{G}$ of $\mathbf{Grp}$ and $G\in\mathit{Ob}(\mathscr{G})$, a $\mathscr{G}$-extendible map on $G$ will here mean an assignment ...
- 20.5k
13
votes
4
answers
843
views
What is a "general" relation algebra?
I'm trying to understand why (or if) the axioms of relation algebras are "the right ones." For example, we can back up the idea that the group axioms exactly capture the notion of "...
- 20.5k
9
votes
1
answer
760
views
What classes of groups can arise as "symmetry groups of terms"?
Let $\mathfrak{A}$ be an algebra (in the sense of universal algebra). To each term $t(x_1,...,x_n)$ in the language of $\mathfrak{A}$ in which each variable actually appears we can assign a group $G_\...
- 20.5k
8
votes
2
answers
585
views
Is the equational theory of groups axiomatized by the associative law?
Consider the class of groups in the signature {*}. Is the equational theory of that class axiomatized by the associative law? I asked this on math stack exchange but I didn't receive a satisfactory ...
- 2,023
8
votes
0
answers
148
views
What is this quotient of the free product?
Previously asked at MSE. The construction here can generalize to arbitrary algebras (in the sense of universal algebra) in the same signature with the only needed tweak being the replacement of "...
- 20.5k
6
votes
2
answers
706
views
Non-trivial problems about the trivial group
Is there any non-trivial problem (maybe open problem) about the trivial group?
I asked already a question about the Laws characterizing the trivial group. There is a description of such laws. As ...
- 2,233
5
votes
3
answers
309
views
The existence of an algebra whose set of identities and first order theory are equivalent
Is there an algebra $A$ (for example a group) such that $Th(A)$ is logically equivalent to $id(A)$? In other words, is there an algebra $A$ such that
$$
Mod(Th(A))=Var(A)?
$$
Clearly finite algebras ...
- 2,233
4
votes
1
answer
206
views
Why the axiomatic rank of the variety of groups is equal to three?
I am thankful of Anton Klyachko who introduced axiomatic rank to me: the axiomatic rank of a variety is the minimum number of variables which we need to define that variety by identities.
It seems ...
- 2,233
4
votes
0
answers
166
views
Is there any good methods for writing down basis for laws of groups?
I am wondering if there is a good method to write down a finite equational basis for a finite group.
Especially I am wondering if there is a good method in following situations:
We can write a group ...
- 93
2
votes
4
answers
555
views
relatively free groups in $Var(S_3)$
Suppose $S_3$ is the symmetric group of order 6. Which elements of the variety $Var(S_3)$ are relatively free?
This question is related to my previous question
Relatively free algebras in a variety ...
- 2,233
2
votes
1
answer
330
views
Algebras admitting quantifier elimination
I apologize if this question is meaningless or trivial:
What are examples of Algebras admitting quantifier elimination? Especially are there Groups admitting quantifier elimination?
I need to say ...
- 2,233
2
votes
1
answer
223
views
Possible symmetry groups of power terms
Previously asked and bountied at MSE:
Let $\mathfrak{E}=(\mathbb{N};\mathit{exp})$ be the algebra in the sense of universal algebra consisting of the natural numbers with just exponentiation. To each ...
- 20.5k
0
votes
3
answers
185
views
Negated varieties and their relatively free algebras
During the past days, I asked some questions in order to gain a clear understanding of the notion of "free algebras". I suppose that the question below is the most clear image of the concept I have ...
- 2,233