Questions tagged [magma]
A magma is a set together with a binary operation on this set. (For questions about the computer algebra system named Magma, use the [magma-cas] tag instead.)
202 questions
2 votes
1 answer
116 views
Is the variety defined by $x*(y*z) = (x*z)*y$ (in commutative unital magmas) known or studied?
I am exploring a particular algebraic structure defined as follows: Let $(M, ∗)$ be a set $M$ equipped with a binary operation such that: $*$ is commutative: $a * b = b * a$ for all $a, b \in M$. ...
1 vote
1 answer
136 views
Elliptic curve $y^2=x^3+ax^3+bx$ with rational 2-torsion in Magma/Sage
Let $E/\mathbb{Q}: y^2=x^3+ax+b$ be an elliptic curve with $E(\mathbb{Q})[2]\cong \mathbb{Z}/2\mathbb{Z}$. I know that we can rewrite the equation of $E/\mathbb{Q}$ in the form $y^2=x^3+a'x^2+b'x$ (...
0 votes
0 answers
70 views
What do you call a structure such that its group operation distributes over the operation under which it is a commutative magma?
Is there a term in use (ever used?--I have not had much luck in my attempts at literature review) to designate an algebraic structure with two operations, one of which satisfies the properties of a ...
1 vote
0 answers
40 views
Calculating the Ext algebra of a module via magma
Let $A$ be a quiver algebra (with admissible relations) of finite global dimension and $M$ a finite dimensional basic $A$-module. Is there a way to use a computer algebra system like Magma to ...
0 votes
0 answers
25 views
Coercion between a number field and a cyclotomic field in MAGMA
Let $K$ be a cyclotomic field defined in MAGMA, via K:=CyclotomicField(N). Let $x$ be an element in $K$ that is not contained in $\mathbb{Q}$. I try to run the ...
0 votes
0 answers
59 views
MAGMA returning non-principal ideals when factorizing primes over a ring of integers in a PID
I am working through Will Steins Math129 course, some of which requires the use of MAGMA. Specifically, assignment two (question 2a) requires the factorization of the ideal (2004) over the Gaussian ...
3 votes
1 answer
150 views
Alternative proof that a power-associative magma with no idempotent elements is infinite.
I have been investigating commutative, associative magmas in an ad hoc way for the past few days and was curious about idempontent-free magmas. The magma $(\mathbb{Z}_{\ge 1}, +)$ is idempotent-free, ...
0 votes
2 answers
91 views
Is there a magma with at least 2 elements which is commutative but almost completely non-associative?
I know there exist non-empty magmas $(S;*)$ which are both completely non-associative and non-commutative (completely non-commutative means $x*y \neq y*x$ unless $x=y$, and completely non-associative ...
1 vote
1 answer
107 views
Collection of not-numerical semi-group of $\mathbb{N}$
Let $k \in \mathbb{N^*}$ and $r$ a divisor of $k$. Then : $$M_{k,\ r}=\{k,\ k+r,\ k+2r,\ k+3r,\ \cdots\}$$ is a collection of proper semi-group of $\mathbb{N}$ for $+$ (classic addition), which are ...
3 votes
0 answers
68 views
Conservative idempotent magma - proof attempt
I need help with checking proof about idempotent and conservative magmas. Let magma be any ordered pair $(M, \odot)$, where $M$ is nonempty set and $\odot$ binary operation on $M$. Now I need to ...
2 votes
0 answers
59 views
Weaker notion of closure for partial magmas
Let $(G,\cdot)$ be a partial magma (a set endowed with a partial binary operation). In principle, for such generic structures it is possible that $\exists g \in G$ such that $\forall h \in G, \, g\...
-1 votes
1 answer
60 views
map from spin to special orthogonal in Magma [closed]
Let $G:=\operatorname{Spin}(7,5)$. How to construct in Magma the map $G \rightarrow G/Z(G) $ where $Z(G)$ is the center. I get this from Magma: ...
-4 votes
1 answer
157 views
Practical example of differences between associativity and alternativity (and the in-between Bol loop)? [closed]
Associativity is: $$(a * b) * c = a * (b * c)$$ Alternativity is: $$a * (a * b) = (a * a) * b$$ $$(a * b) * b = a * (b * b)$$ Bol loop is: $${\displaystyle a(b(ac))=(a(ba))c}$$ $${\displaystyle ((ca)b)...
2 votes
1 answer
97 views
Smallest possible cardinality of finite set with two non-elementarily equivalent magmas which satisfy the same $\forall$-theory?
This is a follow-up to my previous question, here: Smallest possible cardinality of finite set with two non-elementarily equivalent magmas which satisfy the same quasi-equations?. My question now is, ...
3 votes
1 answer
122 views
Are there 45 unital magmas with three elements (up to isomorphism)?
How many unital magmas (magma with an identity element) with three elements are there (up to isomorphism)? My approach: List out all of the possible 2x2 multiplication tables for the two non-identity ...