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Mihaela Vajiac

Publications and source records attributed to Mihaela Vajiac.

10 recordsLinked to original sources
arXiv2024

Unitary rational functions: The scaled quaternion case

We develop the theory of minimal realizations and factorizations of rational functions where the coefficient space is a ring of the type introduced in our previous work, the scaled quaternions, which includes as special cases the quaternions and the split quaternions. The methods involved are not a direct generalization of the complex or quaternionic settings, and in particular, the adjoint is not the classical adjoint and we use properties of real Hilbert spaces. This adjoint allows to define the counterpart of unitarity for matrix-rational functions, and we develop the corresponding theories of realizations and unitary factorizations. We also begin a theory of matrices in the underlying rings.

math.FA↗
arXiv2024

Scaled global operators and Fueter variables on non-zero scaled hypercomplex numbers

In this paper we describe the rise of global operators in the scaled quaternionic case, an important extension from the quaternionic case to the family of scaled hypercomplex numbers $\mathbb{H}_t,\, t\in\mathbb{R}^*$, of which the $\mathbb{H}_{-1}=\mathbb{H}$ is the space of quaternions and $\mathbb{H}_{1}$ is the space of split quaternions. We also describe the scaled Fueter-type variables associated to these operators, developing a coherent theory in this field. We use these types of variables to build different types of function spaces on $\mathbb{H}_t$. Counterparts of the Hardy space and of the Arveson space are also introduced and studied in the present setting. The two different adjoints in the scaled hypercomplex numbers lead to two parallel cases in each instance. Finally we introduce and study the notion of rational function.

math.FA↗
arXiv2023

Two Bicomplex and One Multicomplex Least Mean Square algorithms

We study and introduce new gradient operators in the complex and bicomplex settings, inspired from the well-known Least Mean Square (LMS) algorithm invented in 1960 by Widrow and Hoff for Adaptive Linear Neuron (ADALINE). These gradient operators will be used to formulate new learning rules for the Bicomplex Least Mean Square (BLMS) algorithms and we will also formulate these learning rules will for the case of multicomplex LMS algorithms (MLMS). This approach extends both the classical real and complex LMS algorithms.

cs.LG↗
arXiv2023

The Bicomplex Tensor Product, a Bicomplex Choi Theorem and Applications

In this paper we extend the concept of tensor product to the bicomplex case and use it to prove the bicomplex counterpart of the classical Choi theorem in the theory of complex matrices and operators. The concept of hyperbolic tensor product is also discussed, and we link these results to the theory of quantum channels in the bicomplex and hyperbolic case, as well as applications to bicomplex digital signal processing.

cs.IT↗
arXiv2022

Discrete Wiener Algebra in the Bicomplex Setting, Spectral Factorization with Symmetry, and Superoscillations

In this paper we present parallel theories on constructing Wiener algebras in the bicomplex setting. With the appropriate symmetry condition, the bicomplex matrix valued case can be seen as a complex valued case and, in this matrix valued case, we make the necessary connection between classical bicomplex analysis and complex analysis with symmetry. We also write an application to superoscillations in this case.

math.CV↗
arXiv2022

A note on the complex and bicomplex valued neural networks

In this paper we first write a proof of the perceptron convergence algorithm for the complex multivalued neural networks (CMVNNs). Our primary goal is to formulate and prove the perceptron convergence algorithm for the bicomplex multivalued neural networks (BMVNNs) and other important results in the theory of neural networks based on a bicomplex algebra.

cs.LG↗
arXiv2019

A primer on Script Geometry

This text is an exposition of a new approach into discrete differential geometry, called Script Geometry. In difference to classic approaches while scripts are based on complexes of cells we are not limited to simplicial complexes. One of the principal concepts of Script Geometry is the notion of tightness which is a minimality condition corresponds to the condition that the local homology at the level of cells is trivial and provides us the equivalence of a Poincare lemma. Basic concepts and properties of scripts are presented as well as operations on scripts. Also the necessary concepts of metrics, dual scripts, Dirac and Laplace operators are presented to provide the groundwork for a discrete function theory. To help understanding the concepts concrete and illustrative examples are provided.

math.DG↗
arXiv2006

Virasoro Actions and Harmonic Maps (after Schwarz)

The actions of a half Virasoro algebra have appeared in many integrable systems. In this paper we show that there is an action of a (Half) Virasoro algebra on the space of (2+0) harmonic maps into a Lie group. This action is generated by a natural action on the frames. A similar calculation on the space-time (1+1) harmonic maps yields formulas generated by John Schwarz.

math.DG↗