Section III.II: Postulates

Section III.II: Postulates#

Pivot Postulates#

Proof Let \(\zeta \in K\). Note

\[K \subseteq C \subseteq D\]

Then by definition of Perfect Palindromes, \(\zeta = \zeta^{-1}\).

(\(\rightarrow\)) Assume \(\omega_{\zeta} = \sigma\). Assume, for the sake of contradiction, \(\zeta \notin P_{-}\). Then, since,

\[P_{+} \cup P_{-} = P\]

And,

\[P_{+} \cap P_{-} = \varnothing\]

It follows that it must be the case, \(\zeta \in P_{+}\). Therefore, \(\exists i \in mathbb{N}: l(\zeta) = 2i\). Then, by definition of Pivot Characters,

\[\overrightarrow{\omega_s} = \overleftarrow{\omega_s} = \sigma\]

Where the last equality follows by assumption. Then,

\[\zeta[\frac{l(s) + 2}{2}] = \zeta[\frac{l(2)}{2}] = \sigma\]

In other words, two consecutive Characters are Delimiter. But this is impossible if \(\zeta \in D\). Therefore, it must be case,

\[\zeta \in P_{-}\]

(\(\leftarrow\)) Assume \(\zeta \in P_{-}\). By Theorem 2.1.5, it follows immediately,

\[\omega_{\zeta} = \sigma\]

Thus the equivalence is established. Summarizing and generalizing,

\[\forall \zeta \in K: (\omega_{\zeta} = \sigma) \equiv \zeta \in P_{-}\]

Proof Let \(\zeta \in K\).

Inverse Postulates#