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Seminars "Proof Theory" and "Logic Online Seminar"
May 18, 2020 18:30, Moscow, online
 


Fusible numbers and Peano Arithmetic

Gabriel Nivasch
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MP4 826.3 Mb
MP4 1,294.5 Mb

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Gabriel Nivasch



Abstract: Inspired by a mathematical riddle involving fuses, we define a set of rational numbers which we call "fusible numbers". We prove that the set of fusible numbers is well-ordered in $\mathbb{R}$, with order type $\varepsilon_0$. We prove that the density of the fusible numbers along the real line grows at an incredibly fast rate, namely at least like the function $F_{\varepsilon_0}$ of the fast-growing hierarchy. Finally, we derive some true statements that can be formulated but not proven in Peano Arithmetic, of a different flavor than previously known such statements, for example, "For every natural number $n$ there exists a smallest fusible number larger than $n$."

Language: English

* Join the Zoom meeting 18.05.2020 18:30 MSK (GMT +3): https://zoom.us/j/887484923
 
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