Contents
Contents
Idea
The idea of a minor scale comes from Peter Freyd, in his attempt to give an algebraic (in the sense of universal algebra) description of the real interval, which he believed to be more fundamental than the real numbers themselves in analysis.
Certain minor scales are models of multiplicative linear logic.
Minor scales are an example of centipede mathematics; a lot of this page will be determining which of Freyd’s results in Algebraic Real Analysis still applies in minor scales and possible weakenings of the scale identity axiom.
Note: The terms multiplicative conjunction, multiplicative disjunction, linear implication, reverse linear implication, additive conjunction, and additive disjunction used in this page come from scales, which are algebraic models of multiplicative-additive linear logics. While the same operations may be defined in the same way in minor scales as in scales, the operations may no longer correspond to any linear logic at all, and are simply defined to reduce syntactical complexity in equational sentences and axioms.
Definition
In terms of multiplicative conjunction and disjunction
A minor scale is a symmetric closed midpoint algebra with two binary operations called multiplicative conjunction and called multiplicative disjunction such that for all in ,
In terms of linear implication
Note: linear implication is usually denoted using . We use instead because there is no left-pointing in LaTeX? for the dual linear implication, while there is
From one could define the zoom operators.
-zooming can be defined as
-zooming can be defined as
In terms of zoom operations
A minor scale is a symmetric closed midpoint algebra with two functions called -zooming and called -zooming such that for all in ,
In terms of central dilatations
A minor scale is a symmetric closed midpoint algebra with a function called central dilatation such that for all in ,
-zooming can be defined as
-zooming can be defined as
Multiplicative conjunction can be defined as
Multiplicative disjunction can be defined as
Linear implication can be defined as
Other operations
The binary operation additive conjunction is defined as
and additive disjunction is defined as
The binary operation dilatation is defined as
or as
Defining operations in terms of other operations
Multiplication conjunction, multiplicative disjunction, -zooming, -zooming, linear implication, and dual linear implication can all be defined in terms of each other, , and .
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Additional possible equational axioms
Here is a list of other possible equational axioms that a minor scale might satisfy:
- the scale identities: for all and in ,
The rest of the axioms follow from the scale identities:
- is a fixed point of :
- the axiom of compensation: for all in ,
- the axioms of central distributivity: for all in ,
- the axiom of balance: for all and in ,
- the disjunction property: for all and in ,
- the coalgebra equation: for all in ,
- associativity of multiplicative conjunction: for all , , and in
- associativity of multiplicative disjunction: for all , , and in
- the various lattice axioms for : for all , , and in ,
Properties
Every minor scale with is trivial.
is a fixed point of and is a fixed point of .
As a minor scale is a closed midpoint algebra, a minor scale has a partial order . If , then .
The currying of results in a dilatation at an element . For every element in , dilatation at is a retraction of contraction at : , where is the identity function on .
Examples
The unit interval with , , , , , , , and is an example of a minor scale.
The set of truth values in Girard’s linear logic is a minor scale.
References
- Peter Freyd, Algebraic real analysis, Theory and Applications of Categories, Vol. 20, 2008, No. 10, pp 215-306 (tac:20-10)