Would either or both of these work as a lattice on the closed unit circle in the plane?(adsbygoogle = window.adsbygoogle || []).push({});

(1) Using a linear order: Expressing points in polar coordinates (with angles 0≤θ<2π), define:

(r,α) < (s,β) iff r<s or (r=s & α<β)

(r,α) ≤ (s,β) iff (r,α) < (s,β) or (r=s & α=β)

The meet and join are then just the inf and the sup, resp.

(2) Non-linear partial order:

(r,α) < (s,β) iff r<s

(r,α) ≤ (s,β) iff (r,α) < (s,β) or (r=s & α=β)

The join: if (r,α) < (s,β), then (r,α) [itex]\vee[/itex] (s,β) = (s,β)

For the cases r=s: (r,α)[itex]\vee[/itex](r,α) =(r,α)

If α≠β, then (r,α)[itex]\vee[/itex](r,β) = ((r+1)/2, (α+β)/2)

The meet: if (r,α) < (s,β), then (r,α) [itex]\wedge[/itex] (s,β) = (r,α)

For the cases r=s: (r,α)[itex]\wedge[/itex](r,α) =(r,α)

If α≠β, then (r,α)[itex]\wedge[/itex](r,β) = (r/2, (α+β)/2)

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# Lattice on the closed unit circle?

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