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The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions often require the calculation of the gradient and Hessian, however,…

Numerical Analysis · Mathematics 2016-02-23 Dongpo Xu , Danilo P. Mandic

Recently, the connectionist temporal classification (CTC) model coupled with recurrent (RNN) or convolutional neural networks (CNN), made it easier to train speech recognition systems in an end-to-end fashion. However in real-valued models,…

Second order circularity, also called properness, for complex random variables is a well known and studied concept. In the case of quaternion random variables, some extensions have been proposed, leading to applications in quaternion signal…

General Mathematics · Mathematics 2016-11-24 Nicolas Le Bihan

Quaternions are important for a wide variety of rotation-related problems in computer graphics, machine vision, and robotics. We study the nontrivial geometry of the relationship between quaternions and rotation matrices by exploiting the…

Image and Video Processing · Electrical Eng. & Systems 2022-05-20 Andrew J. Hanson , Sonya M. Hanson

In recent years, hyper-complex deep networks (such as complex-valued and quaternion-valued neural networks) have received a renewed interest in the literature. They find applications in multiple fields, ranging from image reconstruction to…

Machine Learning · Computer Science 2020-07-14 Riccardo Vecchi , Simone Scardapane , Danilo Comminiello , Aurelio Uncini

Recurrent neural networks (RNNs) are powerful architectures to model sequential data, due to their capability to learn short and long-term dependencies between the basic elements of a sequence. Nonetheless, popular tasks such as speech or…

More than 150 years after their invention by Hamilton, quaternions are now widely used in the aerospace and computer animation industries to track the paths of moving objects undergoing three-axis rotations. It is shown here that they…

Mathematical Physics · Physics 2015-06-26 J. D. Gibbon

In recent years, several models using Quaternion-Valued Convolutional Neural Networks (QCNNs) for different problems have been proposed. Although the definition of the quaternion convolution layer is the same, there are different…

Machine Learning · Computer Science 2024-09-04 Gerardo Altamirano-Gómez , Carlos Gershenson

The paper presents a classification of quadratic extension algebras, also known as algebras of degree 2, as well as several characterizations of quaternion algebras over a field (of characteristic not 2). The presentation is not restricted…

Rings and Algebras · Mathematics 2016-09-27 France Dacar

Quaternion valued neural networks experienced rising popularity and interest from researchers in the last years, whereby the derivatives with respect to quaternions needed for optimization are calculated as the sum of the partial…

Machine Learning · Computer Science 2022-12-27 Johannes Pöppelbaum , Andreas Schwung

In this paper we introduce a new algebraic device, which enables us to treat the quaternions as though they were a commutative field. This is of interest both for its own sake, and because it can be applied to develop an "algebraic…

Differential Geometry · Mathematics 2007-05-23 Dominic Joyce

The purpose of this paper is to propose a new multi-layer feedforward quaternion neural network model architecture, Reverse Quaternion Neural Network which utilizes the non-commutative nature of quaternion products, and to clarify its…

Neural and Evolutionary Computing · Computer Science 2025-08-14 Shogo Yamauchi , Tohru Nitta , Takaaki Ohnishi

A fully tensorial theoretical framework for hypercomplex-valued neural networks is presented. The proposed approach enables neural network architectures to operate on data defined over arbitrary finite-dimensional algebras. The central…

Machine Learning · Computer Science 2026-01-27 Agnieszka Niemczynowicz , Radosław Antoni Kycia

Machine Learning algorithms have had a profound impact on the field of computer science over the past few decades. These algorithms performance is greatly influenced by the representations that are derived from the data in the learning…

The article is devoted to affine and wrap algebras over quaternions and octonions. Residues of functions of quaternion and octonion variables are studied. They are used for construction of such algebras. Their structure is investigated.

Complex Variables · Mathematics 2018-12-18 S. V. Ludkovsky

Contemporary state-of-the-art neural networks have increasingly large numbers of parameters, which prevents their deployment on devices with limited computational power. Pruning is one technique to remove unnecessary weights and reduce…

Machine Learning · Computer Science 2023-08-15 Sahel Mohammad Iqbal , Subhankar Mishra

Motivated by a model in quantum computation we study orthogonal sets of integral vectors of the same norm that can be extended with new vectors keeping the norm and the orthogonality. Our approach involves some arithmetic properties of the…

Number Theory · Mathematics 2022-03-22 Fernando Chamizo , Jorge Jiménez Urroz

Quaternions often appear in wide areas of applied science and engineering such as wireless communications systems, mechanics, etc. It is known that are two types of non-isomorphic generalized quaternion algebras, namely: the algebra of…

Rings and Algebras · Mathematics 2014-06-05 Cristina Flaut , Vitalii Shpakivskyi

One of the important ways development takes place in mathematics is via a process of generalization. On the basis of a recent characterization of this process we propose a principle that generalizations of mathematical structures that are…

High Energy Physics - Phenomenology · Physics 2008-02-03 Ronald Anderson , Girish C. Joshi

Inspired by the relation between the algebra of complex numbers and plane geometry, William Rowan Hamilton sought an algebra of triples for application to three dimensional geometry. Unable to multiply and divide triples, he invented a…

History and Overview · Mathematics 2016-06-13 Govind S. Krishnaswami , Sonakshi Sachdev