Computability

About: Computability is a research topic. Over the lifetime, 2829 publications have been published within this topic receiving 85162 citations.

A Programming Approach to Computability

Abstract: 1 Introduction.- 1.1 Partial Functions and Algorithms.- 1.2 An Invitation to Computability Theory.- 1.3 Diagonalization and the Halting Problem.- 2 The Syntax and Semantics of while-Programs.- 2.1 The Language of while-Programs.- 2.2 Macro Statements.- 2.3 The Computable Functions.- 3 Enumeration and Universality of the Computable Functions.- 3.1 The Effective Enumeration of while-Programs.- 3.2 Universal Functions and Interpreters.- 3.3 String-Processing Functions.- 3.4 Pairing Functions.- 4 Techniques of Elementary Computability Theory.- 4.1 Algorithmic Specifications.- 4.2 The s-m-n Theorem.- 4.3 Undecidable Problems.- 5 Program Methodology.- 5.1 An Invitation to Denotational Semantics.- 5.2 Recursive Programs 110 5.3* Proof Rules for Program Properties.- 6 The Recursion Theorem and Properties of Enumerations.- 6.1 The Recursion Theorem.- 6.2 Model-Independent Properties of Enumerations.- 7 Computable Properties of Sets (Part 1).- 7.1 Recursive and Recursively Enumerable Sets.- 7.2 Indexing the Recursively Enumerable Sets.- 7.3 Godel's Incompleteness Theorem.- 8 Computable Properties of Sets (Part 2).- 8.1 Rice's Theorem and Related Results.- 8.2 A Classification of Sets.- 9 Alternative Approaches to Computability.- 9.1 The Turing Characterization.- 9.2 The Kleene Characterization.- 9.3 Symbol-Manipulation Systems and Formal Languages.- References.- Notation Index.- Author Index.

Proofs and Computations

Abstract: Driven by the question, 'What is the computational content of a (formal) proof?', this book studies fundamental interactions between proof theory and computability. It provides a unique self-contained text for advanced students and researchers in mathematical logic and computer science. Part I covers basic proof theory, computability and Gdel's theorems. Part II studies and classifies provable recursion in classical systems, from fragments of Peano arithmetic up to 11-CA0. Ordinal analysis and the (Schwichtenberg-Wainer) subrecursive hierarchies play a central role and are used in proving the 'modified finite Ramsey' and 'extended Kruskal' independence results for PA and 11-CA0. Part III develops the theoretical underpinnings of the first author's proof assistant MINLOG. Three chapters cover higher-type computability via information systems, a constructive theory TCF of computable functionals, realizability, Dialectica interpretation, computationally significant quantifiers and connectives and polytime complexity in a two-sorted, higher-type arithmetic with linear logic.

Positive real control for uncertain two-dimensional systems

Abstract: This brief deals with the problem of positive real control for uncertain two-dimensional (2-D) discrete systems described by the Fornasini-Marchesini local state-space model. The parameter uncertainty is time-invariant and norm-bounded. The problem we address is the design of a state feedback controller that robustly stabilizes the uncertain system and achieves the extended strictly positive realness of the resulting closed-loop system for all admissible uncertainties. A version of positive realness for 2-D discrete systems is established. Based on this, a condition for the solvability of the positive real control problem is derived in terms of a linear matrix inequality. Furthermore,the solution of a desired state feedback controller is also given. Finally, we provide a numerical example to demonstrate the applicability of the proposed approach.

Hypercomputation: Computing Beyond the Church-Turing Barrier

Abstract: This book provides a thorough description of hypercomputation. It covers all attempts at devising conceptual hypermachines and all new promising computational paradigms that may eventually lead to the construction of a hypermachine. Readers will gain a deeper understanding of what computability is, and why the Church-Turing thesis poses an arbitrary limit to what can be actually computed. Hypercomputing is a relatively novel idea. However, the books most important features are its description of the various attempts of hypercomputation, from trial-and-error machines to the exploration of the human mind, if we treat it as a computing device.

Computing the non-computable

Abstract: We explore in the framework of quantum computation the notion of computability, which holds a central position in mathematics and theoretical computer science. A quantum algorithm that exploits the quantum adiabatic processes is considered for Hilbert's tenth problem, which is equivalent to the Turing halting problem and known to be mathematically non-computable. Generalized quantum algorithms are also considered for some other mathematical non-computables in the same and in different non-computability classes. The key element of all these algorithms is the measurability of both the values of physical observables and the quantum-mechanical probability distributions for these values. It is argued that computability, and thus the limits of mathematics, ought to be determined not solely by mathematics itself but also by physical principles.