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33
Semantics of Local Variables
, 1992
"... This expository article discusses recent progress on the problem of giving sufficiently abstract semantics to localvariable declarations in Algollike languages, especially work using categorical methods. ..."
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Cited by 35 (4 self)
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This expository article discusses recent progress on the problem of giving sufficiently abstract semantics to localvariable declarations in Algollike languages, especially work using categorical methods.
Deliverables: A Categorical Approach to Program Development in Type Theory
, 1992
"... This thesis considers the problem of program correctness within a rich theory of dependent types, the Extended Calculus of Constructions (ECC). This system contains a powerful programming language of higherorder primitive recursion and higherorder intuitionistic logic. It is supported by Pollack's ..."
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Cited by 24 (1 self)
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This thesis considers the problem of program correctness within a rich theory of dependent types, the Extended Calculus of Constructions (ECC). This system contains a powerful programming language of higherorder primitive recursion and higherorder intuitionistic logic. It is supported by Pollack's versatile LEGO implementation, which I use extensively to develop the mathematical constructions studied here. I systematically investigate Burstall's notion of deliverable, that is, a program paired with a proof of correctness. This approach separates the concerns of programming and logic, since I want a simple program extraction mechanism. The \Sigmatypes of the calculus enable us to achieve this. There are many similarities with the subset interpretation of MartinLof type theory. I show that deliverables have a rich categorical structure, so that correctness proofs may be decomposed in a principled way. The categorical combinators which I define in the system package up much logical bo...
A topos foundation for theories of physics: II. Daseinisation and the liberation of quantum theory
 Journal of Mathematical Physics
"... This paper is the second in a series whose goal is to develop a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. Our basic contention is that constructing a t ..."
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Cited by 11 (4 self)
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This paper is the second in a series whose goal is to develop a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. Our basic contention is that constructing a theory of physics is equivalent to finding a representation in a topos of a certain formal language that is attached to the system. Classical physics arises when the topos is the category of sets. Other types of theory employ a different topos. In this paper, we study in depth the topos representation of the propositional language, PL(S), for the case of quantum theory. In doing so, we make a direct link with, and clarify, the earlier work on applying topos theory to quantum physics. The key step is a process we term ‘daseinisation ’ by which a projection operator is mapped to a subobject of the spectral presheaf—the topos quantum analogue of a classical state space. In the second part of the paper we change gear with the introduction of the more sophisticated local language L(S). From this point forward, throughout the rest of the series of papers, our attention will be devoted almost entirely to this language. In the present paper, we use L(S) to study ‘truth objects ’ in the topos. These are objects in the topos that play the role of states: a necessary development as the spectral presheaf has no global elements, and hence there are no microstates in the sense of classical physics. Truth objects therefore play a crucial role in our formalism.
Fibring Logics with Topos Semantics
, 2002
"... The concept of fibring is extended to higherorder logics with arbitrary modalities and binding operators. A general completeness theorem is established for such logics including HOL and with the metatheorem of deduction. As a corollary, completeness is shown to be preserved when fibring such rich ..."
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Cited by 11 (6 self)
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The concept of fibring is extended to higherorder logics with arbitrary modalities and binding operators. A general completeness theorem is established for such logics including HOL and with the metatheorem of deduction. As a corollary, completeness is shown to be preserved when fibring such rich logics. This result is extended to weaker logics in the cases where fibring preserves conservativeness of HOLenrichments. Soundness is shown to be preserved by fibring without any further assumptions.
Knowledge Representation, Computation, and Learning in Higherorder Logic
 In preparation
, 2001
"... This paper contains a systematic study of the foundations of knowledge representation, computation, and learning in higherorder logic. First, a polymorphicallytyped higherorder logic, whose origins can be traced back to Church's simple theory of types, is presented. A model theory and proof theor ..."
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Cited by 10 (7 self)
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This paper contains a systematic study of the foundations of knowledge representation, computation, and learning in higherorder logic. First, a polymorphicallytyped higherorder logic, whose origins can be traced back to Church's simple theory of types, is presented. A model theory and proof theory for this logic are developed and basic theorems relating these two are given. A metric space of certain closed terms, which provides a rich language for representing individuals, is then studied. Also a method of systematically constructing predicates on such individuals is given. The technique of programming with abstractions is illustrated. Major applications of the logic to declarative programming languages and machine learning are indicated. 1
Does category theory provide a framework for mathematical structuralism?
 PHILOSOPHIA MATHEMATICA
, 2003
"... Category theory and topos theory have been seen as providing a structuralist framework for mathematics autonomous vis à vis set theory. It is argued here that these theories require a background logic of relations and substantive assumptions addressing mathematical existence of categories themselves ..."
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Cited by 10 (3 self)
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Category theory and topos theory have been seen as providing a structuralist framework for mathematics autonomous vis à vis set theory. It is argued here that these theories require a background logic of relations and substantive assumptions addressing mathematical existence of categories themselves. We propose a synthesis of Bell’s “manytopoi” view and modalstructuralism. Surprisingly, a combination of mereology and plural quantification suffices to describe hypothetical large domains, recovering the Grothendieck method of universes. Both topos theory and set theory can be carried out relative to such domains; puzzles about “large categories ” and “proper classes ” are handled in a
A topos foundation for theories of physics: I. Formal languages for physics
, 2007
"... This paper is the first in a series whose goal is to develop a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. Our basic contention is that constructing a th ..."
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Cited by 9 (3 self)
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This paper is the first in a series whose goal is to develop a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. Our basic contention is that constructing a theory of physics is equivalent to finding a representation in a topos of a certain formal language that is attached to the system. Classical physics arises when the topos is the category of sets. Other types of theory employ a different topos. In this paper we discuss two different types of language that can be attached to a system, S. The first is a propositional language, PL(S); the second is a higherorder, typed language L(S). Both languages provide deductive systems with an intuitionistic logic. The reason for introducing PL(S) is that, as shown in paper II of the series, it is the easiest way of understanding, and expanding on, the earlier work on topos theory and quantum physics. However, the main thrust of our programme utilises the more powerful language L(S) and its representation in an appropriate topos.
NonCommutative Topology for Curved Quantum Causality
 International Journal of Theoretical Physics
"... A quantum causal topology is presented. This is modeled after a noncommutative scheme type of theory for the curved finitary spacetime sheaves of the nonabelian incidence Rota algebras that represent ‘gravitational quantum causal sets’. The finitary spacetime primitive algebra scheme structures fo ..."
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Cited by 8 (8 self)
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A quantum causal topology is presented. This is modeled after a noncommutative scheme type of theory for the curved finitary spacetime sheaves of the nonabelian incidence Rota algebras that represent ‘gravitational quantum causal sets’. The finitary spacetime primitive algebra scheme structures for quantum causal sets proposed here are interpreted as the kinematics of a curved and reticular local quantum causality. Dynamics for quantum causal sets is then represented by appropriate scheme morphisms, thus it has a purely categorical description that is manifestly ‘gaugeindependent’. Hence, a schematic version of the Principle of General Covariance of General Relativity is formulated for the dynamically variable quantum causal sets. We compare our noncommutative schemetheoretic curved quantum causal topology with some recent C ∗quantale models for nonabelian generalizations of classical commutative topological spaces or locales, as well as with some relevant recent results obtained from applying sheaf and topostheoretic ideas to quantum logic proper. Motivated by the latter, we organize our finitary spacetime primitive algebra schemes of curved quantum causal sets into a toposlike structure, coined ‘quantum topos’, and argue that it is a sound model of a structure that Selesnick has anticipated to underlie Finkelstein’s reticular and curved quantum causal net. At the end we conjecture that the fundamental quantum timeasymmetry that Penrose has expected to be the main characteristic of the elusive ‘true quantum gravity ’ is possibly of a kinematical or structural rather than of a dynamical character, and we also discuss the possibility of a unified description of quantum logic and quantum gravity in quantum topostheoretic terms.
A Topos Perspective on StateVector Reduction
"... A preliminary investigation is made of possible applications in quantum theory of the topos formed by the collection of all Msets, where M is a monoid. Earlier results on topos aspects of quantum theory can be rederived in this way. However, the formalism also suggests a new way of constructing a ‘ ..."
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Cited by 5 (2 self)
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A preliminary investigation is made of possible applications in quantum theory of the topos formed by the collection of all Msets, where M is a monoid. Earlier results on topos aspects of quantum theory can be rederived in this way. However, the formalism also suggests a new way of constructing a ‘neorealist’ interpretation of quantum theory in which the truth values of propositions are determined by the actions of the monoid of strings of finite projection operators. By these means, a novel topos perspective is gained on the concept of statevector reduction. 1