# Red workbook, p4

### Transcript

• (a)=> (b)
• , synd,
• Sei =>
• Nimm Limes von
• (f) => (a)
• ist min. US [!] (abg. klar; US klar; jeder Orbit enhaelt )
• (e) => (a)
• wie (b)=>(e) die Beh.
• [Rest einfach bis trivial]
• [Corollar prox =>
• Bew: => Beh. ]
• Corollar prox , unif. rek. => ex
• ”<=” Cor & Satz zuvor
• ”=>” Cor -> L -> (Satz(e)) wirkt wie auf .
• Corollar/Notiz: unif. <=> .
• {Mittwoch 10 Uhr]

### partial Translation

• (a)=> (b)
• , syndetic =>
• Let =>
• Let be the limit of
• (f) => (e)
• is a minimal subsystem
• obviously closed and a subsystem. Also, every orbit contains .
• (e) => (a)
• now proceed as in (b)=>(a).
• [Corollary proximal to =>
• Bew: => Claim. ]
• Corollary proximal to , uniformly recurrent => ex
• ”<=” by previous Corollary & Theorem
• ”=>” previous corollary yields min. LID L => (Theorem part (e)) => operates like on .
• Corollary/Note: unif. recurrent <=> .

### Notes

Not much to say here; just finishing the proof of the theorem with some simple corollaries. The notes are very short on details but it seems to be all there.

This finishes the first lecture in the workbook (the next one was apparently scheduled for Wednesday, 10am).

In a sense it’s a very “normal” proof in this field. That isn’t to say it’s easy but while the proof is a bit of a grind (a and b being the really only interesting part), the arguments are typical arguments that appear frequently; e.g., how to use syndeticity to build an ultrafilter (in this case using a net), the powerful properties of minimal left ideals (and their somewhat horrific lack of discernable structure).