# 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.)

108 questions
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### What is an example of a groupoid which is not a semigroup?

I know that groupoid refers to an algebraic structure with a binary operation. The only necessary condition is closure. However, I couldn't find any easy-to-understand example of a groupoid which is ...
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### Uniqueness of two side zeroes of binary operation

I came across the following fact in group theory: Two-sided identity of binary operation is unique. Does the similar statement for two sided zero also holds? : Two-sided zero of binary ...
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### Is there a name for an algebraic structure with only “addition” and “truncated subtraction”?

Given a set $S$ with An associative binary "addition" operation $+$ with corresponding neutral element $0$ such that $(S, +)$ is a monoid A non-associative binary "truncated subtraction" operation $-$...
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### The direct product $G\times E$ of a group $G$ with a right zero semigroup $E$ is a right group.

This is part of Exercise 2.6.6 of Howie's "Fundamentals of Semigroup Theory". I apologise in advance if this is a duplicate. The Details: Let $S$ be a semigroup. Definition 1: We call $S$ right ...
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### Deducing a lattice is modular.

This is (the second part of) Exercise 2.6.4 of Howie's "Fundamentals of Semigroup Theory". The first part is here. The Details. Definition 1: A lattice $(L, \le, \wedge, \vee)$ is modular if, for ...
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