Directory talk:Jon Awbrey/Papers/Inquiry Driven Systems : Part 6

Work Area

Alternate Text

A semigroup consists of a nonempty set with an associative LOC on it. On formal occasions, a semigroup is introduced by means a formula like \(X = (X, *),\!\) interpreted to mean that a semigroup \(X\!\) is specified by giving two pieces of data, a nonempty set that conventionally, if somewhat ambiguously, goes under the same name \({}^{\backprime\backprime} X {}^{\prime\prime},\!\) plus an associative binary operation denoted by \({}^{\backprime\backprime} * {}^{\prime\prime}.\!\) In contexts where there is only one semigroup being discussed, or where the additional structure is otherwise understood, it is common practice to call the semigroup by the name of the underlying set. In contexts where more than one semigroup is formed on the same set, one may use notations like \(X_i = (X, *_i)\!\) to distinguish them.

Additive Presentation

Version 1

The \(n^\text{th}\!\) multiple of an element \(x\!\) in a semigroup \(\underline{X} = (X, +, 0),\!\) for integer \(n > 0,\!\) is notated as \(nx\!\) and defined as follows. Proceeding recursively, for \(n = 1,\!\) let \(1x = x,\!\) and for \(n > 1,\!\) let \(nx = (n-1)x + x.\!\)

The \(n^\text{th}\!\) multiple of \(x\!\) in a monoid \(\underline{X} = (X, +, 0),\!\) for integer \(n \ge 0,\!\) is defined the same way for \(n > 0,\!\) letting \(0x = 0\!\) when \(n = 0.\!\)

The \(n^\text{th}\!\) multiple of \(x\!\) in a group \(\underline{X} = (X, +, 0),\!\) for any integer \(n,\!\) is defined the same way for \(n \ge 0,\!\) letting \(nx = (-n)(-x)\!\) for \(n < 0.\!\)

Version 2

In a semigroup written additively, the \(n^\text{th}\!\) multiple of an element \(x\!\) is notated as \(nx\!\) and defined for every positive integer \(n\!\) in the following manner. Proceeding recursively, let \(1x = x\!\) and let \(nx = (n-1)x + x\!\) for all \(n > 1.\!\)

In a monoid written additively, the multiple \(nx\!\) is defined for every non-negative integer \(n\!\) by letting \(0x = 0\!\) and proceeding the same way for \(n > 0.\!\)

In a group written additively, the multiple \(nx\!\) is defined for every integer \(n\!\) by letting \(nx = (-n)(-x)\!\) for \(n < 0\!\) and proceeding the same way for \(n \ge 0.\!\)

Table Work

\(\text{Table 32.1}~~\text{Scheme of a Group Operation Table}\)

\(*\!\)	\(x_0\!\)	\(\ldots\!\)	\(x_j\!\)	\(\ldots\!\)
\(x_0\!\)	\(x_0 * x_0\!\)	\(\ldots\!\)	\(x_0 * x_j\!\)	\(\ldots\!\)
\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)
\(x_i\!\)	\(x_i * x_0\!\)	\(\ldots\!\)	\(x_i * x_j\!\)	\(\ldots\!\)
\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)	\(\ldots\!\)

 
Table 32.1  Scheme of a Group Multiplication Table
	*	x0	...	xj	...
	x0	x0*x0	...	x0*xj	...
	...	...	...	...	...
	xi	xi*x0	...	xi*xj	...
	...	...	...	...	...

Table 32.2  Scheme of the Regular Ante-Representation
	Element	Function as Set of Ordered Pairs of Elements
	x0	{ <x0, x0*x0>,   ...,   <xj, x0*xj>,   ...,    }
	...
	xi	{ <x0, xi*x0>,   ...,   <xj, xi*xj>,   ...,    }
	...

Table 32.3  Scheme of the Regular Post-Representation
	Element	Function as Set of Ordered Pairs of Elements
	x0	{ <x0, x0*x0>,   ...,   <xj, xj*x0>,   ...,    }
	...
	xi	{ <x0, x0*xi>,   ...,   <xj, xj*xi>,   ...,    }
	...