arXiv subjects
Publications and source records attributed to Matthew P. Szudzik.
This article reformulates the theory of computable physical models, previously introduced by the author, as a branch of applied model theory in first-order logic. It provides a semantic approach to the philosophy of science that incorporates aspects of operationalism and Popper's degrees of falsifiability.
This article surveys the known results (and not very well-known results) associated with Cantor's pairing function and the Rosenberg-Strong pairing function, including their inverses, their generalizations to higher dimensions, and a discussion of a few of the advantages of the Rosenberg-Strong pairing function over Cantor's pairing function in practical applications. In particular, an application to the problem of enumerating full binary trees is discussed.
A pairing function for the non-negative integers is said to be binary perfect if the binary representation of the output is of length 2k or less whenever each input has length k or less. Pairing functions with square shells, such as the Rosenberg-Strong pairing function, are binary perfect. Many well-known discrete space-filling curves, including the discrete Hilbert curve, are also binary perfect. The concept of a binary proportional pairing function generalizes the concept of a binary perfect pairing function. Binary proportional pairing functions may be useful in applications where a pairing function is used, and where the function's inputs have lengths differing by a fixed proportion. In this article, a general technique for constructing a pairing function from any non-decreasing unbounded function is described. This technique is used to construct a binary proportional pairing function and its inverse.
Godel's theory T can be understood as a theory of the simply-typed lambda calculus that is extended to include the constant 0, the successor function S, and the operator R_tau for primitive recursion on objects of type tau. It is known that the functions from non-negative integers to non-negative integers that can be defined in this theory are exactly the <epsilon_0-recursive functions of non-negative integers. As an extension of this result, we show that when the domain and codomain are restricted to pure closed normal forms, the functionals of arbitrary type that are definable in T can be encoded as <epsilon_0-recursive functions.
When can a model of a physical system be regarded as computable? We provide the definition of a computable physical model to answer this question. The connection between our definition and Kreisel's notion of a mechanistic theory is discussed, and several examples of computable physical models are given, including models which feature discrete motion, a model which features non-discrete continuous motion, and probabilistic models such as radioactive decay. We show how computable physical models on effective topological spaces can be formulated using the theory of type-two effectivity (TTE). Various common operations on computable physical models are described, such as the operation of coarse-graining and the formation of statistical ensembles. The definition of a computable physical model also allows for a precise formalization of the computable universe hypothesis--the claim that all the laws of physics are computable.
We discuss historical attempts to formulate a physical hypothesis from which Turing's thesis may be derived, and also discuss some related attempts to establish the computability of mathematical models in physics. We show that these attempts are all related to a single, unified hypothesis.