475 research outputs found
The Small-Is-Very-Small Principle
The central result of this paper is the small-is-very-small principle for
restricted sequential theories. The principle says roughly that whenever the
given theory shows that a property has a small witness, i.e. a witness in every
definable cut, then it shows that the property has a very small witness: i.e. a
witness below a given standard number.
We draw various consequences from the central result. For example (in rough
formulations): (i) Every restricted, recursively enumerable sequential theory
has a finitely axiomatized extension that is conservative w.r.t. formulas of
complexity . (ii) Every sequential model has, for any , an extension
that is elementary for formulas of complexity , in which the
intersection of all definable cuts is the natural numbers. (iii) We have
reflection for -sentences with sufficiently small witness in any
consistent restricted theory . (iv) Suppose is recursively enumerable
and sequential. Suppose further that every recursively enumerable and
sequential that locally inteprets , globally interprets . Then,
is mutually globally interpretable with a finitely axiomatized sequential
theory.
The paper contains some careful groundwork developing partial satisfaction
predicates in sequential theories for the complexity measure depth of
quantifier alternations
Interpretable Graph Networks Formulate Universal Algebra Conjectures
The rise of Artificial Intelligence (AI) recently empowered researchers to
investigate hard mathematical problems which eluded traditional approaches for
decades. Yet, the use of AI in Universal Algebra (UA) -- one of the fields
laying the foundations of modern mathematics -- is still completely unexplored.
This work proposes the first use of AI to investigate UA's conjectures with an
equivalent equational and topological characterization. While topological
representations would enable the analysis of such properties using graph neural
networks, the limited transparency and brittle explainability of these models
hinder their straightforward use to empirically validate existing conjectures
or to formulate new ones. To bridge these gaps, we propose a general algorithm
generating AI-ready datasets based on UA's conjectures, and introduce a novel
neural layer to build fully interpretable graph networks. The results of our
experiments demonstrate that interpretable graph networks: (i) enhance
interpretability without sacrificing task accuracy, (ii) strongly generalize
when predicting universal algebra's properties, (iii) generate simple
explanations that empirically validate existing conjectures, and (iv) identify
subgraphs suggesting the formulation of novel conjectures
The wonderland of reflections
A fundamental fact for the algebraic theory of constraint satisfaction
problems (CSPs) over a fixed template is that pp-interpretations between at
most countable \omega-categorical relational structures have two algebraic
counterparts for their polymorphism clones: a semantic one via the standard
algebraic operators H, S, P, and a syntactic one via clone homomorphisms
(capturing identities). We provide a similar characterization which
incorporates all relational constructions relevant for CSPs, that is,
homomorphic equivalence and adding singletons to cores in addition to
pp-interpretations. For the semantic part we introduce a new construction,
called reflection, and for the syntactic part we find an appropriate weakening
of clone homomorphisms, called h1 clone homomorphisms (capturing identities of
height 1).
As a consequence, the complexity of the CSP of an at most countable
-categorical structure depends only on the identities of height 1
satisfied in its polymorphism clone as well as the the natural uniformity
thereon. This allows us in turn to formulate a new elegant dichotomy conjecture
for the CSPs of reducts of finitely bounded homogeneous structures.
Finally, we reveal a close connection between h1 clone homomorphisms and the
notion of compatibility with projections used in the study of the lattice of
interpretability types of varieties.Comment: 24 page
Certified -sentences
In this paper, we study the employment of -sentences with
certificate, i.e., -sentences where a number of principles is added
to ensure that the witness is sufficiently number-like. We develop certificates
in some detail and illustrate their use by reproving some classical results and
proving some new ones. An example of such a classical result is Vaught's
theorem of the strong effective inseparability of . We also develop
the new idea of a theory being -sourced. Using this notion
we can transfer a number of salient results from to a variety of
other theories.Comment: 31 page
Realms: A Structure for Consolidating Knowledge about Mathematical Theories
Since there are different ways of axiomatizing and developing a mathematical
theory, knowledge about a such a theory may reside in many places and in many
forms within a library of formalized mathematics. We introduce the notion of a
realm as a structure for consolidating knowledge about a mathematical theory. A
realm contains several axiomatizations of a theory that are separately
developed. Views interconnect these developments and establish that the
axiomatizations are equivalent in the sense of being mutually interpretable. A
realm also contains an external interface that is convenient for users of the
library who want to apply the concepts and facts of the theory without delving
into the details of how the concepts and facts were developed. We illustrate
the utility of realms through a series of examples. We also give an outline of
the mechanisms that are needed to create and maintain realms.Comment: As accepted for CICM 201
Pairs, sets and sequences in first-order theories
Asuransi sebagai aktivitas bisnis diharuskan memenuhi prinsip-prinsip hukum asuransi. Salah satu prinsip yang harus dipegang teguh adalah principle of utmost good faith, di samping prinsip yang lain. Prinsip ini berbunyi bahwa seorang tertanggung wajib memberi informasi secara jujur terhadap apa yang dipertanggungkan kepada penanggung. Dalam bisnis Islam, kejujuran merupakan prinsip yang harus dijunjung tinggi. Secara hukum, prinsip ini diatur dalam KUH Dagang. Persoalannya adalah apakah prinsip ini dianggap cukup dari sudut pandang hukum perjanjian syariah. Secara sekilas bahwa prinsip iktikad baik sempurna ini telah memenuhi asas perjanjian syariah, namun demikian tidak memiliki kriteria maksimal kejujuran. Ketiadaan kejujuran dalam bisnis asuransi akan berdampak pada batalnya perjanjian asuransi karena ada unsur cacat kehendak (‘uyub ar-ridla). Insurance as a business activity must fulfill principles of insurance law. One of the principles that must be hold on is the principle of utmost good faith. The principle says that an endured person must honestly give information of what should be given responsibility to the guarantor. In Islamic business, honesty is a principle that should be respected. From point of view of law, the principle is settled in commerce law. The problem is that whether the principle is represenative enough if it is viewed from law of syariah agreement. At glance, the principle has fulfilled the basic of syariah agreement, however, it does not have maximum criteria of honesty. Unavailability of honesty in insurance business will give effect of invalidate of insurance agreement, for there is a deformity of desire (‘uyub ar-ridla).</p
Day's Theorem is sharp for even
Both congruence distributive and congruence modular varieties admit Maltsev
characterizations by means of the existence of a finite but variable number of
appropriate terms. A. Day showed that from J\'onsson terms
witnessing congruence distributivity it is possible to construct terms witnessing congruence modularity. We show that Day's result
about the number of such terms is sharp when is even. We also deal with
other kinds of terms, such as alvin, Gumm, directed, specular, mixed and
defective.
All the results hold also when restricted to locally finite varieties. We
introduce some families of congruence distributive varieties and characterize
many congruence identities they satisfy.Comment: v.2, some improvements and some corrections, particularly in Section
9 v.3, a few further improvements, corrections simplification
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