Combinatorial principles in second-order theories of bounded arithmetic
De Castro, Rodrigo
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https://hdl.handle.net/2142/20320
Description
Title
Combinatorial principles in second-order theories of bounded arithmetic
Author(s)
De Castro, Rodrigo
Issue Date
1992
Doctoral Committee Chair(s)
Jockusch, Carl G., Jr.
Department of Study
Mathematics
Discipline
Mathematics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Mathematics
Language
eng
Abstract
An attempt is made to study the mathematical strength of the weak second order theories of Bounded Arithmetic U$\sbsp{2}{i}$ and V$\sbsp{2}{i}$, i $\geq$ 0, introduced by S. Buss. It is first shown that U$\sbsp{2}{1}$ can $\Sigma\sbsp{1}{1,b}$-define the functions in the second class of Grzegorczyk, $\varepsilon\sp2$, or, equivalently, the class of $\Sigma\sbsp{1}{1,b}$-definable functions in U$\sbsp{2}{1}$ is closed under bounded recursion.
It is shown next that U$\sbsp{2}{1}$ proves the $\Delta\sbsp{1}{1,b}$-pigeonhole principle. Two general combinatorial principles, the $\Delta\sbsp{1}{1,b}$-partition principle and the $\Delta\sbsp{1}{1,b}$-equipartition principle, are obtained from it thereby demonstrating that the $\Delta\sbsp{1}{1,b}$-PHP embodies a strong notion of cardinality. The introduction of these principles is motivated with some examples, notably by showing that Euler's theorem is provable in U$\sbsp{2}{1}$. The provability of Euler's theorem in weak first order fragments of Peano Arithmetic is an open problem.
"A theory of polynomials is developed in U$\sbsp{2}{1}$ and it is proved that U$\sbsp{2}{1}$ + B $\vdash$ ""existence of primitive roots"" where formula B asserts that a nontrivial polynomial of degree n can have at most n solutions modulo p if p is a prime. By an essential use of the $\Delta\sbsp{1}{1,b}$-PHP and the $\Delta\sbsp{1}{1,b}$-partition principle it is shown that V$\sbsp{2}{1}\/\vdash$ B, hence V$\sbsp{2}{1}\/\vdash$ ""existence of primitive roots""."
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