1,294 research outputs found
A Uniform Method for Proving Lower Bounds of the Computational Complexity of Logical Theories
https://deepblue.lib.umich.edu/bitstream/2027.42/154178/1/39015100081655.pd
Third-order matching in -Curry is undecidable
Given closed untyped -terms and , which can be assigned some types and respectively in the Curry-style systems of type assignment (essentially due to R.~Hindley) -Curry [Barendregt 92], [Mitchell 96], [Hindley97], it is undecidable whether there exist closed terms of types such that , even if the orders of 's do not exceed 3. This undecidability result should be contrasted to the decidability of the third-order matching in the Church-style simply typed lambda calculus with a single constant base type [Dowek 92]. The proof is by reduction from the recursively inseparable sets of invalid and finitely satisfiable sentences of the first-order theory of binary relation [Trakhtenbrot 53, Vaught 60]
The Rice-Shapiro theorem in Computable Topology
We provide requirements on effectively enumerable topological spaces which
guarantee that the Rice-Shapiro theorem holds for the computable elements of
these spaces. We show that the relaxation of these requirements leads to the
classes of effectively enumerable topological spaces where the Rice-Shapiro
theorem does not hold. We propose two constructions that generate effectively
enumerable topological spaces with particular properties from wn--families and
computable trees without computable infinite paths. Using them we propose
examples that give a flavor of this class
The umbilical cord of finite model theory
Model theory was born and developed as a part of mathematical logic. It has
various application domains but is not beholden to any of them. A priori, the
research area known as finite model theory would be just a part of model theory
but didn't turn out that way. There is one application domain -- relational
database management -- that finite model theory had been beholden to during a
substantial early period when databases provided the motivation and were the
main application target for finite model theory.
Arguably, finite model theory was motivated even more by complexity theory.
But the subject of this paper is how relational database theory influenced
finite model theory.
This is NOT a scholarly history of the subject with proper credits to all
participants. My original intent was to cover just the developments that I
witnessed or participated in. The need to make the story coherent forced me to
cover some additional developments.Comment: To be published in the Logic in Computer Science column of the
February 2023 issue of the Bulletin of the European Association for
Theoretical Computer Scienc
On Elementary Theories of Ordinal Notation Systems based on Reflection Principles
We consider the constructive ordinal notation system for the ordinal
that were introduced by L.D. Beklemishev. There are fragments of
this system that are ordinal notation systems for the smaller ordinals
(towers of -exponentiations of the height ). This
systems are based on Japaridze's provability logic . They are
closely related with the technique of ordinal analysis of and
fragments of based on iterated reflection principles. We consider
this notation system and it's fragments as structures with the signatures
selected in a natural way. We prove that the full notation system and it's
fragments, for ordinals , have undecidable elementary theories.
We also prove that the fragments of the full system, for ordinals
, have decidable elementary theories. We obtain some results
about decidability of elementary theory, for the ordinal notation systems with
weaker signatures.Comment: 23 page
Orthogonal vector computations
Quantum computation is the suitable orthogonal encoding of possibly holistic
functional properties into state vectors, followed by a projective measurement.Comment: 8 pages, 2 figures, some revisions and addition
What is Radical Recursion?
Recursion or self-reference is a key feature of contemporary research and writing in semiotics. The paper begins by focusing on the role of recursion in poststructuralism. It is suggested that much of what passes for recursion in this field is in fact not recursive all the way down. After the paradoxical meaning of radical recursion is adumbrated, topology is employed to provide some examples. The properties of the Moebius strip prove helpful in bringing out the dialectical nature of radical recursion. The Moebius is employed to explore the recursive interplay of terms that are classically regarded as binary opposites: identity and difference, object and subject, continuity and discontinuity, etc. To realize radical recursion in an even more concrete manner, a higher-dimensional counterpart of the Moebius strip is utilized, namely, the Klein bottle. The presentation concludes by enlisting phenomenological philosopher Maurice Merleau-Ponty’s concept of depth to interpret the Klein bottle’s extra dimension
A Patterning Approach to Complexity Thinking and Understanding for Students: A Case Study
Complexity thinking and understanding are vital skills for young people in these times of uncertainty and change. Such skills contribute to resilience and capacities for adaptivity and innovation. Within my teaching practice I have found students to be aware of complex dynamics, uncertainty and change, both in their lives and in the world. However, the current curriculum lacks language and process to conceptualise, articulate and develop complexity understanding. To address this problem, I developed and introduced a patterns-based design and process to a cohort of Australian secondary students. Comprising flowform patterning together with ecological metaphors, the design forms a conceptual language and practical process for thinking about, understanding and engaging with complex phenomena and change. Together these capacities are described here as complexity competence. Implemented initially to engage with time as a complex phenomenon, the design is described as the Patterns of Humantime (PHT), and the process of implementation as Complexity Patterning. Implementation during the development phase demonstrated the design’s capacity as a way to understand time as a complex phenomenon, as well as facilitating a relational and identity development approach to learning. In more recent research workshops with American undergraduate Liberal Studies students, the PHT design showed to be effective for understanding complexity and indicated the design’s capacity as a patterning process for engaging in collaborative projects in complex situations of diversity, change and uncertainty. Avenues to develop curriculum and evaluation materials, as well as professional development workshops, are being explored
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