Algebras Of Type Research Articles

Quasi-rectifiable Lie algebras for partial differential equations

Abstract We introduce families of quasi-rectifiable vector fields and study their geometric and algebraic aspects. Then, we analyse their applications to systems of partial differential equations. Our results explain, in a simple manner, the properties of families of vector fields describing hydrodynamic-type equations by means of k-waves. Facts concerning families of quasi-rectifiable vector fields, their relation to Hamiltonian systems, and practical procedures for studying such families are developed. We introduce and analyse quasi-rectifiable Lie algebras, which are motivated by geometric and practical reasons. We classify different types of quasi-rectifiable Lie algebras, e.g. indecomposable ones up to dimension five. New methods for solving systems of hydrodynamic-type equations are established to illustrate our results. In particular, we study hydrodynamic-type systems admitting Riemann k-wave solutions through quasi-rectifiable Lie algebras of vector fields. We develop techniques for obtaining the submanifolds related to quasi-rectifiable Lie algebras of vector fields and systems of partial differential equations admitting a nonlinear superposition rule: the PDE Lie systems.

The Properties of Two-Fold Algebra Based on the n-standard Fuzzy Number Theoretical System

In this paper, we study the two-fold algebra based on the n-standard fuzzy number theoretical system as a special type of two-fold fuzzy algebras, where we study the elementary properties of the algebraic operations defined over this system. Also, we prove many results that describe the relations between two-fold substructures and sub-algebras defined by fuzzy number theoretical systems. On the other hand, we provide many different examples to explain our results.

Deformation Quantization of Nonassociative Algebras

We investigate formal deformations of certain classes of nonassociative algebras including classes of K[Σ3]-associative algebras, Lie-admissible algebras and anti-associative algebras. In a process which is similar to Poisson algebra for the associative case, we identify for each type of algebras (A,μ) a type of algebras (A,μ,ψ) such that formal deformations of (A,μ) appear as quantizations of (A,μ,ψ). The process of polarization/depolarization associates to each nonassociative algebra a couple of algebras which products are respectively commutative and skew-symmetric and it is linked with the algebra obtained from the formal deformation. The anti-associative case is developed with a link with the Jacobi–Jordan algebras.

Sum and Weighted Sum Formulas for Fibonacci and Lucas Quaternions

Fibonacci and Lucas quaternions are deeply studied in the literature after its definition by Horadam in 1963. Binet formula, generation function, Cassini, Catalan, Honsberger, and other identities for these sequences studied in different quaternion algebra types like split quaternion algebra, dual quaternion algebra, etc. Additionally, some of the generalizations for Fibonacci and Lucas quaternions are studied like k-Fibonacci quaternions, k-Lucas quaternions, Horadam quaternions, and more. However, despite being researched intensively, the summation formulas or weighted summation formulas for these sequences are not examined thoroughly. In this study, after briefly summarizing the literature, we focused on the summation and the weighted summation formulas for the Fibonacci and the Lucas quaternions. In addition, we provided generalized weighted summation formulas for the Fibonacci and Lucas quaternions. Moreover, we calculated generalized weighted summation formulas for the double coefficient Fibonacci and double coefficient Lucas quaternions which have two Fibonacci and Lucas coefficient in every unit of the quaternion, respectively.

Validity-Preserving Delta Debugging via Generator Trace Reduction

Reducing test inputs that trigger bugs is crucial for efficient debugging. Delta debugging is the most popular approach for this purpose. When test inputs need to conform to certain specifications, existing delta debugging practice encounters a validity problem: it blindly applies reduction rules, producing a large number of invalid test inputs that do not satisfy the required specifications. This overall diminishing effectiveness and efficiency becomes even more pronounced when the specifications extend beyond syntactical structures. Our key insight is that we should leverage input generators, which are aware of these specifications, to generate valid reduced inputs, rather than straightforwardly performing reduction on test inputs. In this paper, we propose a generator-based delta debugging method, namely GReduce, which derives validity-preserving reducers. Specifically, given a generator and its execution, demonstrating how the bug-inducing test input is generated, GReduce searches for other executions on the generator that yield reduced, valid test inputs. The evaluation results on five benchmarks (i.e., graphs, DL models, JavaScript programs, SymPy, and algebraic data types) show that GReduce substantially outperforms state-of-the-art syntax-based reducers including Perses and T-PDD, and also outperforms QuickCheck, SmartCheck, as well as the state-of-the-art choice-sequence-based reducer Hypothesis, demonstrating the effectiveness, efficiency, and versatility of GReduce.

Quantum Reference Frames, Measurement Schemes and the Type of Local Algebras in Quantum Field Theory

We develop an operational framework, combining relativistic quantum measurement theory with quantum reference frames (QRFs), in which local measurements of a quantum field on a background with symmetries are performed relative to a QRF. This yields a joint algebra of quantum-field and reference-frame observables that is invariant under the natural action of the group of spacetime isometries. For the appropriate class of quantum reference frames, this algebra is parameterised in terms of crossed products. Provided that the quantum field has good thermal properties (expressed by the existence of a KMS state at some nonzero temperature), one can use modular theory to show that the invariant algebra admits a semifinite trace. If furthermore the quantum reference frame has good thermal behaviour (expressed in terms of the properties of a KMS weight) at the same temperature, this trace is finite. We give precise conditions for the invariant algebra of physical observables to be a type II1 factor. Our results build upon recent work of Chandrasekaran et al. (J High Energy Phys 2023(2): 1–56, 2023. arXiv:2206.10780), providing both a significant mathematical generalisation of these findings and a refined operational understanding of their model.

APPLICATION OF SYSTEMS ANALYSIS AND COMPUTER ALGORITHMS IN STUDYING ORBITS OF 7-DIMENSIONAL LIE ALGEBRAS

We discuss a systematic approach to the problem of describing holomorphically homogeneous real hypersurfaces in the space C4, each of which is an orbit of some real Lie algebra. When studying the family of 7-dimensional Lie algebras, which plays an important role in the problem at hand and contains more than a thousand different types of algebras, it is natural to use computer algorithms. With the participation of the authors of this article, classification results on the orbits of several large blocks of algebras from this family were previously obtained. Relations are established between the presence and dimensions of nilpotent and Abelian subalgebras of the original Lie algebras and such properties of their orbits in C4 as Levi degeneracy and tubularity. In this article, the above ideas and computer algorithms are applied to a family of 18 types of 7-dimensional Lie algebras that have a common 6-dimensional nil-radical. Holomorphic realizations in C4 of these algebras are constructed and by integrating them, all holomorphically homogeneous (in the local sense) Levi-nondegenerate 7-dimensional orbits of this family are obtained. Using a quadratic change of variables, it is shown that all these orbits are holomorphically equivalent to tubular hypersurfaces.

A Brief Overview of the Pawns Programming Language

This paper describes the Pawns programming language, currently under development, which uses several novel features to combine the functional and imperative programming paradigms. It supports pure functional programming (including algebraic data types, higher-order programming and parametric polymorphism), where the representation of values need not be considered. It also supports lower-level C-like imperative programming with pointers and the destructive update of all fields of the structs used to represent the algebraic data types. All destructive update of variables is made obvious in Pawns code, via annotations on statements and in type signatures. Type signatures must also declare sharing between any arguments and result that may be updated. For example, if two arguments of a function are trees that share a subtree and the subtree is updated within the function, both variables must be annotated at that point in the code, and the sharing and update of both arguments must be declared in the type signature of the function. The compiler performs extensive sharing analysis to check that the declarations and annotations are correct. This analysis allows destructive update to be encapsulated: a function with no update annotations in its type signature is guaranteed to behave as a pure function, even though the value returned may have been constructed using destructive update within the function. Additionally, the sharing analysis helps support a constrained form of global variables that also allows destructive update to be encapsulated and safe update of variables with polymorphic types to be performed.

Generation of algebraic data type values using evolutionary algorithms

Automatic data generation is a key component of automated software testing. Random generation of test input data can uncover some bugs in software, but its effectiveness decreases when those inputs must satisfy complex properties in order to be meaningful. In this work, we study an evolutionary approach to generate values that can be encoded as algebraic data types plus additional properties. First, the approach is illustrated with the generation of sorted lists. Then, we generalize the technique to arbitrary algebraic data type definitions. Finally, we consider the problem of constrained data types where the data must satisfy some nontrivial property, using the well-known example of red-black trees for our experiments. This example will allow us to introduce the main principles of evolutionary algorithms and how these principles can be applied to obtain valid, nontrivial samples of a given data structure. Our experiments have revealed that this evolutionary approach is able to improve diversity, and increase the size of valid generated values with respect to simple random sampling techniques.

Yang-Baxter Equations and Relative Rota-Baxter Operators for Left-Alia Algebras Associated to Invariant Theory

Left-Alia algebras are a class of algebras with symmetric Jacobi identities. They contain several typical types of algebras as subclasses, and are closely related to the invariant theory. In this paper, we study the construction theory of left-Alia bialgebras. We introduce the notion of the left-Alia Yang-Baxter equation. We show that an antisymmetric solution of the left-Alia Yang-Baxter equation gives rise to a left-Alia bialgebra that we call triangular. The notions of relative Rota-Baxter operators of left-Alia algebras and pre-left-Alia algebras are introduced to provide antisymmetric solutions of the left-Alia Yang-Baxter equation.

Catamorphic Abstractions for Constrained Horn Clause Satisfiability

Abstract Catamorphisms are functions that are recursively defined on list and trees and, in general, on algebraic data types (ADTs), and are often used to compute suitable abstractions of programs that manipulate ADTs. Examples of catamorphisms include functions that compute size of lists, orderedness of lists, and height of trees. It is well known that program properties specified through catamorphisms can be proved by showing the satisfiability of suitable sets of constrained Horn clauses (CHCs). We address the problem of checking the satisfiability of those sets of CHCs, and we propose a method for transforming sets of CHCs into equisatisfiable sets where catamorphisms are no longer present. As a consequence, clauses with catamorphisms can be handled without extending the satisfiability algorithms used by existing CHC solvers. Through an experimental evaluation on a nontrivial benchmark consisting of many list and tree processing algorithms expressed as sets of CHCs, we show that our technique is indeed effective and significantly enhances the performance of state-of-the-art CHC solvers.

The Ultimate Conditional Syntax

Functional programming languages typically support expressive pattern-matching syntax allowing programmers to write concise and type-safe code, especially appropriate for manipulating algebraic data types. Many features have been proposed to enhance the expressiveness of stock pattern-matching syntax, such as pattern bindings, pattern alternatives (a.k.a. disjunction), pattern conjunction, view patterns, pattern guards, pattern synonyms, active patterns, ‘if-let’ patterns, multi-way if-expressions, etc. In this paper, we propose a new pattern-matching syntax that is both more expressive and (we argue) simpler and more readable than previous alternatives. Our syntax supports parallel and nested matches interleaved with computations and intermediate bindings. This is achieved through a form of nested multi-way if-expressions with a condition-splitting mechanism to factor common conditional prefixes as well as a binding technique we call conditional pattern flowing. We motivate this new syntax with many examples in the setting of MLscript, a new ML-family programming language. We describe a straightforward desugaring pass from our rich source syntax into a minimal core syntax that only supports flat patterns and has an intuitive small-step semantics. We then provide a translation from the core syntax into a normalized syntax without backtracking, which is more amenable to coverage checking and compilation, and formally prove that our translation is semantics-preserving. We view this work as a step towards rethinking pattern matching to make it more powerful and natural to use. Our syntax can easily be integrated, in part or in whole, into existing as well as future programming language designs.

Validating SMT Solvers for Correctness and Performance via Grammar-Based Enumeration

We introduce ET, a grammar-based enumerator for validating SMT solver correctness and performance. By compiling grammars of the SMT theories to algebraic datatypes, ET leverages the functional enumerator FEAT. ET is highly effective at bug finding and has many complimentary benefits. Despite the extensive and continuous testing of the state-of-the-art SMT solvers Z3 and cvc5, ET found 102 bugs, out of which 76 were confirmed and 32 were fixed. Moreover, ET can be used to understand the evolution of solvers. We derive eight grammars realizing all major SMT theories including the booleans, integers, reals, realints, bit-vectors, arrays, floating points, and strings. Using ET, we test all consecutive releases of the SMT solvers Z3 and CVC4/cvc5 from the last six years (61 versions) on 8 million formulas, and 488 million solver calls. Our results suggest improved correctness in recent versions of both solvers but decreased performance in newer releases of Z3 on small timeouts (since z3-4.8.11) and regressions in early cvc5 releases on larger timeouts. Due to its systematic testing and efficiency, we further advocate ET's use for continuous integration.

On $3$-generated axial algebras of Jordan type $\frac{1}{2}$

Axial algebras of Jordan type $\eta$ are a special type of commutative non-associative algebras. They are generated by idempotents whose adjoint operators have the minimal polynomial dividing $(x-1)x(x-\eta)$, where $\eta$ is a fixed value that is not equal to $0$ or $1$. These algebras have restrictive multiplication rules that generalize the Peirce decomposition for idempotents in Jordan algebras. A universal $3$-generated algebra of Jordan type $\frac{1}{2}$ as an algebra with $4$ parameters was constructed by I. Gorshkov and A. Staroletov. Depending on the value of the parameter, the universal algebra may contain a non-trivial form radical. In this paper, we describe all semisimple $3$-generated algebras of Jordan type $\frac{1}{2}$ over a quadratically closed field.

Boundary algebras of the Kitaev quantum double model

The recent article by Jones et al. [arXiv:2307.12552 (2023)] gave local topological order (LTO) axioms for a quantum spin system, showed they held in Kitaev’s Toric Code and in Levin-Wen string net models, and gave a bulk boundary correspondence to describe bulk excitations in terms of the boundary net of algebras. In this article, we prove the LTO axioms for Kitaev’s Quantum Double model for a finite group G. We identify the boundary nets of algebras with fusion categorical nets associated to (Hilb(G),C[G]) or (Rep(G),CG) depending on whether the boundary cut is rough or smooth, respectively. This allows us to make connections to the work of Ogata [Ann. Henri Poincaré 25, 2353–2387 (2024)] on the type of the cone von Neumann algebras in the algebraic quantum field theory approach to topological superselection sectors. We show that the boundary algebras can also be calculated from a trivial G-symmetry protected topological phase (G-SPT), and that the gauging map preserves the boundary algebras. Finally, we compute the boundary algebras for the (3 + 1)D Quantum Double model associated to an Abelian group.

GADTs are not (Even partial) functors

Abstract Generalized Algebraic Data Types (GADTs) are a syntactic generalization of the usual algebraic data types (ADTs), such as lists, trees, etc. ADTs’ standard initial algebra semantics (IAS) in the category $\mathit{Set}$ of sets justify critical syntactic constructs – such as recursion, pattern matching, and fold – for programming with them. In this paper, we show that semantics for GADTs that specialize to the IAS for ADTs are necessarily unsatisfactory. First, we show that the functorial nature of such semantics for GADTs in $\mathit{Set}$ introduces ghost elements, i.e., elements not writable in syntax. Next, we show how such ghost elements break parametricity. We observe that the situation for GADTs contrasts dramatically with that for ADTs, whose IAS coincides with the parametric model constructed via their Church encodings in System F. Our analysis reveals that the fundamental obstacle to giving a functorial IAS for GADTs is the inherently partial nature of their map functions. We show that this obstacle cannot be overcome by replacing $\mathit{Set}$ with other categories that account for this partiality.

Double-Ended Bit-Stealing for Algebraic Data Types

Algebraic data types are central to the development and evaluation of most functional programs. It is therefore important for compilers to choose compact and efficient representations of such types, in particular to achieve good memory footprints for applications. Algebraic data types are most often represented using blocks of memory where the first word is used as a so-called tag, carrying information about the constructor, and the following words are used for carrying the constructor's arguments. As an optimisation, lists are usually represented more compactly, using a technique called bit-stealing, which, in its simplest form, uses the word-alignment property of pointers to byte-addressed allocated memory to discriminate between the nil constructor (often represented as 0x1) and the cons constructor (aligned pointer to allocated pair). Because the representation supports that all values can be held uniformly in one machine word, possibly pointing to blocks of memory, type erasure is upheld. However, on today's 64-bit architectures, memory addresses (pointers) are represented using only a subset of the 64 bits available in a machine word, which leave many bits unused. In this paper, we explore the use, not only of the least-significant bits of pointers, but also of the most-significant bits, for representing algebraic data types in a full ML compiler. It turns out that, with such a particular utilisation of otherwise unused bits, which we call double-ended bit-stealing, it is possible to choose unboxed representations for a large set of data types, while still not violating the principle of uniform data-representations. Examples include Patricia trees, union-find data structures, stream data types, internal language representations for types and expressions, and mutually recursive ASTs for full language definitions. The double-ended bit-stealing technique is implemented in the MLKit compiler and speedup ranges from 0 to 26 percent on benchmarks that are influenced by the technique. For MLKit, which uses abstract data types extensively, compilation speedups of around 9 percent are achieved for compiling MLton (another Standard ML compiler) and for compiling MLKit itself.

Mini-Workshop: Poisson and Poisson-type algebras

The first historical encounter with Poisson-type algebras is with Hamiltonian mechanics. With the abstraction of many notions in Physics, Hamiltonian systems were geometrized into manifolds that model the set of all possible configurations of the system, and the cotangent bundle of this manifold describes its phase space, which is endowed with a Poisson structure. Poisson brackets led to other algebraic structures, and the notion of Poisson-type algebra arose, including transposed Poisson algebras, Novikov–Poisson algebras, or commutative pre-Lie algebras, for example. These types of algebras have long gained popularity in the scientific world and are not only of their own interest to study, but are also an important tool for researching other mathematical and physical objects.

Automorphism groups of some non-nilpotent Leibniz algebras

Let $L$ be an algebra over a field $F$ with the binary operations $+$ and $[,]$. Then $L$ is called a left Leibniz algebra if it satisfies the left Leibniz identity: $[a,[b,c]]=[[a,b],c]+[b,[a,c]]$ for all $a,b,c\in L$. A linear transformation $f$ of $L$ is called an endomorphism of $L$, if $f([a,b])=[f(a),f(b)]$ for all elements $a,b\in L$. A bijective endomorphism of $L$ is called an automorphism of $L$. It is easy to show that the set of all automorphisms of Leibniz algebra is a group with respect to the operation of multiplication of automorphisms. The description of the structure of the automorphism groups of Leibniz algebras is one of the natural and important problems of the general Leibniz algebra theory. The main goal of this article is to describe the structure of the automorphism group of a certain type of non-nilpotent three-dimensional Leibniz algebras.

Nearly associative algebras

We present a comprehensive study of nearly associative algebras. Our research shows that these algebras are power associative Lie-admissible for which the related Lie algebra is solvable, and are also Jordan-admissible.Furthermore, we describe the features of finite-dimensional nearly associative algebras that are nilpotent. In addition, we define the concepts of radical and semisimplicity for this type of algebras. We give a characterization of semisimple nearly associative algebras and prove the Wedderburn Principal Theorem for them.Lastly, we deal with quadratic nearly associative algebras. We provide a characterization and then an inductive description of them through the process of double extension, enriching our understanding of the structural intricacies of this class of algebras.