Large Countable Ordinals (Part 2)

Last time I took you on a road trip to infinity. We zipped past a bunch of countable ordinals

\omega , \; \omega^\omega,\; \omega^{\omega^\omega}, \;\omega^{\omega^{\omega^\omega}}, \dots

and stopped for gas at the first one after all these. It’s called \epsilon_0. Heuristically, you can imagine it like this:

\epsilon_0 = \omega^{\omega^{\omega^{\omega^{\cdot^{\cdot^{\cdot}}}}}}

More rigorously, it’s the smallest ordinal x obeying the equation

x = \omega^x

Beyond εo

But I’m sure you have a question. What comes after \epsilon_0?

Well, duh! It’s

\epsilon_0 + 1

Then comes

\epsilon_0 + 2

and then eventually we get to

\epsilon_0 + \omega

and then

\epsilon_0 + \omega^2 ,\dots, \epsilon_0 + \omega^3,\dots \epsilon_0 + \omega^4,\dots

and after a long time

\epsilon_0 + \epsilon_0 = \epsilon_0 2

and then eventually

\epsilon_0^2

and then eventually….

Oh, I see! You wanted...

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Published on July 03, 2016 18:00
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