Question

Is $G = \left\{ \begin{bmatrix}a & -b \\ b & a\end{bmatrix} : a,b \in \Bbb R \right\}$ under matrix multiplication a monoid, semigroup, or neither?

score 177 · Answer 1 · 2026-03-25 19:05:50

Is $G = \left\{ \begin{bmatrix}a & -b \\ b & a\end{bmatrix} : a,b \in \Bbb R \right\}$ under matrix multiplication a monoid, semigroup, or neither?

score 120 · Answer 2 · 2026-02-23 04:57:26

120

Views

Is $G = (\Bbb Q^,ab=\frac{a+b}{2})$ a group, monoid, semigroup or none of these?

Published on 23 Feb 2026 - 4:57

score 196 · Answer 3 · 2019-11-25 02:23:06

196

Views

Semigroup over a finite set that is nothing more than that

Published on 25 Nov 2019 - 2:23

score 216 · Answer 4 · 2019-11-27 18:18:53

216

Views

Example of a monoid required for union operation

Published on 27 Nov 2019 - 18:18

score 112 · Answer 5 · 2026-03-25 09:24:55

112

Views

Associative binary operation with several left inverse elememts

Published on 25 Mar 2026 - 9:24

score 41 · Answer 6 · 2019-12-06 11:50:15

41

Views

Semilattice of idempotent

Published on 06 Dec 2019 - 11:50

score 28 · Answer 7 · 2019-12-11 10:07:57

28

Views

Large semigroups of real matrices with real eigenvalues

Published on 11 Dec 2019 - 10:07

score 89 · Answer 8 · 2026-03-25 19:04:32

89

Views

Is $\mathbb{R}\setminus \{-1\}$ a Semi group/Monoid/Group with $a\cdot b=a+b+ab$?

Published on 25 Mar 2026 - 19:04

score 65 · Answer 9 · 2019-12-13 16:02:14

65

Views

Proof that commutative groupoid $(G,*)$ is a semigroup

Published on 13 Dec 2019 - 16:02

score 135 · Answer 10 · 2026-03-25 19:06:24

135

Views

The monoid of fractions associated with the submonoid of cancellable elements of a commutative monoid E

Published on 25 Mar 2026 - 19:06

score 74 · Answer 11 · 2026-03-25 06:12:00

74

Views

Are positional notation systems for natural numbers wreath products of semigroups?

Published on 25 Mar 2026 - 6:12

score 80 · Answer 12 · 2019-12-17 15:22:50

80

Views

A functional equation on a semigroup

Published on 17 Dec 2019 - 15:22

score 294 · Answer 13 · 2019-12-20 06:45:03

294

Views

Existence of a commutative inverse semigroup with no identity element

Published on 20 Dec 2019 - 6:45

score 65 · Answer 14 · 2026-03-25 19:02:17

65

Views

Group of mappings

Published on 25 Mar 2026 - 19:02

score 89 · Answer 15 · 2019-12-22 21:41:13

89

Views

Is the semigroup of lines $\mathcal{M}_n(\mathbb{Q})$, finitely generated

Published on 22 Dec 2019 - 21:41

List Question

Is $G = \left\{ \begin{bmatrix}a & -b \\ b & a\end{bmatrix} : a,b \in \Bbb R \right\}$ under matrix multiplication a monoid, semigroup, or neither?

Is $G = (\Bbb Q^,ab=\frac{a+b}{2})$ a group, monoid, semigroup or none of these?

Semigroup over a finite set that is nothing more than that

Example of a monoid required for union operation

Associative binary operation with several left inverse elememts

Semilattice of idempotent

Large semigroups of real matrices with real eigenvalues

Is $\mathbb{R}\setminus \{-1\}$ a Semi group/Monoid/Group with $a\cdot b=a+b+ab$?

Proof that commutative groupoid $(G,*)$ is a semigroup

The monoid of fractions associated with the submonoid of cancellable elements of a commutative monoid E

Are positional notation systems for natural numbers wreath products of semigroups?

A functional equation on a semigroup

Existence of a commutative inverse semigroup with no identity element

Group of mappings

Is the semigroup of lines $\mathcal{M}_n(\mathbb{Q})$, finitely generated

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