Bilinear Form Research Articles

A Note on Some Properties of Unbounded Bilinear Forms Associated with Skew-Symmetric $L^q(\Omega)$-Matrices

We study the bilinear forms on the space of measurable $p$-integrable functions which are generated by skew-symmetric matrices with unbounded coefficients. We give an example showing that if a skew-symmetric matrix contains a locally unbounded $L^q$-elements, then the corresponding quadratic forms can be alternating. These questions are closely related to the existence issues of the Nuemann boundary value problem for $p$-Laplace elliptic equations with non-symmetric and locally unbounded anisotropic diffusion matrices.

The norming set of a bilinear form on a certain normed space $\mathbb{R}^2$

In this paper we classify the norming set of a bilinear form on the plane with a certain norm whose unit ball has only four extreme points. We obtain the results of [6, 8] as corollary.

Dynamical pathology, singular manifold, bilinear forms and solitons on a (3+1)-dimensional Jadaun-Singh equation in aortic dissection

Dynamical pathology, singular manifold, bilinear forms and solitons on a (3+1)-dimensional Jadaun-Singh equation in aortic dissection

[formula omitted]-soliton solutions of coupled Schrödinger–Boussinesq equation with variable coefficients

In this paper, soliton solutions of the coupled variable coefficients Schrödinger–Boussinesq equation, which describes the stationary propagation of coupled upper-hybrid waves and magnetoacoustic waves in a magnetized plasma, are investigated. Based on the Hirota bilinear method, the bilinear form, one, two, three and N-soliton solutions of Schrödinger–Boussinesq equation are derived. By means of numerical calculation, the specific figures of different soliton solutions are obtained by selecting different coefficients. The propagation and interaction of the soliton solutions are analyzed graphically.

Integrability, and stability aspects for the non-autonomous perturbed Gardner KP equation: Solitons, breathers, [formula omitted]-type resonance and soliton interactions

This article examines the soliton-type solutions, their interactions, and the integrable properties of a non-autonomous perturbed Gardner KP (NPGKP) equation. For the NPGKP equation under consideration, a bilinear structure, and a Bäcklund transformation are designed explicitly, which claim the integrability of the system under some constraints. The stability of the obtained solutions is discussed using modulation instability. The bilinear form demonstrates the dynamic characteristics of multiple solitons, breathers, and their interactions in response to external impulses. Furthermore, it allows for determining the solitons’ amplitudes and velocities. The two-soliton solution yields a first-order breather solution. At the same time, the analytical investigation focuses on the interaction between a single breather and a single-soliton within the multi-soliton solution. This investigation also identifies the resonance of Y-shaped solitons and examines the dynamical characteristics of the interaction between resonant Y-shaped solitons and M-fissionable pulses. The multi-shock solutions and the collisions between shocks are analyzed in the presence of external influences. Graphical representations of the relationships between different sorts of achieved solutions are provided explicitly.

Extensions of Some Statistical Concepts to the Complex Domain

This paper deals with the extension of principal component analysis, canonical correlation analysis, the Cramer–Rao inequality, and a few other statistical concepts in the real domain to the corresponding complex domain. Optimizations of Hermitian forms under a linear constraint, a bilinear form under Hermitian-form constraints, and similar maxima/minima problems in the complex domain are discussed. Some vector/matrix differential operators are developed to handle the above types of problems. These operators in the complex domain and the optimization problems in the complex domain are believed to be new and novel. These operators will also be useful in maximum likelihood estimation problems, which will be illustrated in the concluding remarks. Detailed steps are given in the derivations so that the methods are easily accessible to everyone.

The inverse of a quantum bilinear form of the oriented braid arrangement

We follow here the results of Varchenko, who assigned to each weighted arrangement \(\mathcal{A}\) of hyperplanes in the \(n\)-dimensional real space a bilinear form, which he called the quantum bilinear form of the arrangement \(\mathcal{A}\). We briefly explain the quantum bilinear form of the oriented braid arrangement in the \(n\)-dimensional real space. The main concern of this paper is to compute the inverse of the matrix of the quantum bilinear form of the oriented braid arrangement in \(\mathbb{R}^n\), \({n\ge 2}\). To solve this problem, in [3] the authors used some special matrices and their factorizations in terms of simpler matrices. So, to simplify some matrix calculations, we first introduce a twisted group algebra \({\mathcal{A}(S_{n})}\) of the symmetric group \(S_{n}\) with coefficients in the polynomial ring in \(n^2\) commutative variables and then use a natural representation of some elements of the algebra \({\mathcal{A}(S_{n})}\) on the generic weight subspaces of the multiparametric quon algebra \({\mathcal{B}}\), which immediately gives the corresponding matrices of the quantum bilinear form.

A note on the generalized Babuška–Brezzi theory: Revisiting the proof of the associated Strang error estimates

In this note we simplify the derivation of the error estimates for the generalized Babuška–Brezzi theory with Galerkin schemes defined in terms of approximate bilinear forms and functionals. More precisely, we provide a straight proof that makes no use of any translated continuous or discrete kernel nor of the distance between them, but of suitable upper bounds of the distances of each component of the Galerkin solution to any other member of the respective finite element subspace. In this way, the Strang error estimates are obtained simply by applying the aforementioned bounds along with the triangle inequality, so that they become cleaner and with fully explicit constants. The case in which the discrete bilinear forms can be evaluated at the continuous solution is also considered, which yields the consistency terms to appear separately from the distances to the subspaces, thus allowing the former to be handled independently from the latter.

Breather-type and N-breather solutions for the positive Gardner-KP equation

Starting from the bilinear form of the positive Gardner–Kadomtsev–Petviashvili equation, breather-type and N-breather solutions are obtained with the help of the extended homoclinic test approach. Breather-type, one-breather, two-breather and three-breather solutions are illustrated through 3D plots, density plots and contour plots and some appropriate parameter values have been chosen to better demonstrate their time evolution.

The integrability and infinite conservation laws of a variable coefficient higher-order Schrödinger equation

In this paper, a variable coefficient high-order Schrödinger equation is studied to describe the propagation of ultrashort optical pulses in dispersion reducing fibers. It has third-order dispersion, self steepening and stimulated Raman scattering effects. Using the Bell polynomial method, the integrability of the variable coefficient higher-order Schrödinger equation is discussed. And the bilinear Bäcklund transformation, Lax pair, and infinite conservation laws of the equation are derived. It can be obtained that the variable coefficient higher-order Schrödinger equation is integrable in the sense of Lax pair. The soliton solutions are constructed from the obtained bilinear Bäcklund transformation and the bilinear form. The obtained results are analyzed in the initial–boundary value problem. It is worth mentioning that this paper, based on the angle of increasing the order, obtained the bilinear Bäcklund transformation of the third order variable coefficient Schrödinger equation by using the Bell polynomial method. On this basis, relevant properties such as Lax pair and infinite conservation laws are also obtained, and analyzed the application in the initial–boundary value problem. This has not been studied in existing literatures.

Products of unipotent elements of index 2 in orthogonal and symplectic groups

An automorphism u of a vector space is called unipotent of index 2 whenever (u−id)2=0. Let b be a non-degenerate symmetric or skewsymmetric bilinear form on a vector space V over a field F of characteristic different from 2.Here, we characterize the elements of the isometry group of b that are the product of two unipotent isometries of index 2. In particular, if b is skewsymmetric and nondegenerate we prove that an element of the symplectic group of b is the product of two unipotent isometries of index 2 if and only if it has no Jordan cell of odd size for the eigenvalue −1. As an application, we prove that every element of a symplectic group is the product of three unipotent elements of index 2 (and no fewer in general).For orthogonal groups, the classification closely matches the classification of sums of two square-zero skewselfadjoint operators that was obtained in a recent article [7].

Complete descriptions of pseudo-Euclidean left-symmetric L-algebras and their pseudo-Euclidean modules

A pseudo-Euclidean left-symmetric algebra (A,.,〈,〉) is a left-symmetric algebra endowed with a non-degenerate symmetric bilinear form 〈,〉 such that left multiplications by any element of A are skew-symmetric with respect to 〈,〉. We recall that a pseudo-Euclidean Lie algebra (g,[,],〈,〉) is flat if and only if (g,.,〈,〉), its underlying vector space endowed with the Levi-Civita product associated with 〈,〉, is a pseudo-Euclidean left-symmetric algebra. In this paper, we study pseudo-Euclidean left-symmetric algebras (A,.,〈,〉) such that commutators of all elements of A are contained in the left annihilator of (A,.), these algebras will be called pseudo-Euclidean left-symmetric L-algebras. Next, we introduce and study pseudo-Euclidean modules of pseudo-Euclidean left-symmetric L-algebras. We develop double extension processes that allow us to have inductive descriptions of all pseudo-Euclidean left-symmetric L-algebras and of all its pseudo-Euclidean modules of any signature. This, in particular, improves some of the results obtained in [11].

Shallow-water waves through two new generalized multi-dimensional variable coefficient equations

The objective of this study is to propose and investigate two new forms of generalized variable coefficients within multi-dimensional equations describing shallow-water waves. We employ the Mathematica program to rigorously establish Painlevé's integrability for these two nonlinear equations. Subsequently, we constructed their bilinear forms and utilized Hirota's bilinear method to examine the dispersion relations and phase shifts of these two models that enable the derivative of multi-soliton solutions. Furthermore, diverse forms of lump-wave solutions are also considered. To illustrate the physical characteristics of these two models, we establish several graphical representations of the discovered solutions. These visualizations offer insights into the behavior, shape, and dynamics of both the multi-soliton, Peregrine soliton, lump wave, and rogue wave, enhancing our understanding of their physical significance. The two soliton solutions effectively replicate the shallow water waves, encompassing the T-, X-, and Y-types, along with other intricate interactions. Additionally, the lump and rogue wave structures are displayed to visually represent their spatial structures. These graphical representations offer a comprehensive view of the diverse wave phenomena observed in shallow water systems, aiding in the understanding of their spatial characteristics and interactions. Therefore, our findings indicate that the introduction of the two newly proposed integrable nonlinear evolution equations enhances the repertoire of integrable system models and aids in comprehending the distinctive characteristics of nonlinear dynamics in real-world applications.

Novel complexiton solutions to the new extended (3+1)-dimensional Boiti-Leon-Manna-Pempinelli equation for incompressible fluid

This letter focuses on exploring some novel exact solutions to the new extended (3+1)-dimensional Boiti-Leon-Manna-Pempinelli equation (BLMPE) that has a major role in incompressible fluid. Adopting the Cole-Hopf transformation, the bilinear form of the considered equation is successfully constructed. Then the singular complexiton solutions (SCSs) are developed by applying the ansatz function method with a novel functional form. Additionally, we also find the non-singular complexiton solutions (NCSs) via imposing the restrictive conditions. To unveil the behaviors of the attained solutions better, the corresponding outlines are plotted via Maple.

Multi-scale Sparse Domination

We prove a bilinear form sparse domination theorem that applies to many multi-scale operators beyond Calderón–Zygmund theory, and also establish necessary conditions. Among the applications, we cover large classes of Fourier multipliers, maximal functions, square functions and variation norm operators.

A Skew-Symmetric Energy Stable Almost Dissipation Free Formulation of the Compressible Navier-Stokes Equations

We show that a specific skew-symmetric formulation of the nonlinear terms in the compressible Navier-Stokes equations leads to an energy rate in terms of surface integrals only. No dissipative volume integrals contribute to the energy rate. We also discuss boundary conditions that bounds the surface integrals.

On the presentation of the Grothendieck–Witt group of symmetric bilinear forms over local rings

We prove a chain lemma for inner product spaces over commutative local rings R with residue field other than F2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathbb {F}_2$$\\end{document} and use this to show that the usual presentation of the Grothendieck–Witt group of symmetric bilinear forms over R as the zeroth Milnor–Witt K-group holds provided the residue field of R is not F2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathbb {F}_2$$\\end{document}.

Soliton structures for the (3 + 1)-dimensional Painlevé integrable equation in fluid mediums

The (3 + 1)-dimensional Painlevé integrable equation are a class of nonlinear differential equations with special properties, which play an important role in nonlinear science and are of great significance in solving various practical problems, such as many important models in fields such as quantum mechanics, statistical physics, nonlinear optics, and celestial mechanics. In this work, we utilize the Hirota bilinear form and Mathematica software to formally obtain the interaction solution among lump wave, solitary wave and periodic wave, which has not yet appeared in other literature. Additionally, using the (G′/G)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(G'/G)$$\\end{document}-expansion method, we provide a rich set of exact solutions for the (3 + 1)-dimensional Painlevé integrable equation, which includes two functions with arbitrary values. This method is the first to be applied to the (3 + 1)-dimensional Painlevé integrable equation. By giving some 3D graphics and density maps, the dynamic properties are analyzed and demonstrated, which is beneficial for promoting understanding and application of the (3 + 1)-dimensional Painlevé integrable equation.

Multiple solitons with fission and multi waves interaction solutions of a (3+1)-dimensional combined pKP-BKP integrable equation

The potential Kadomtsev-Petviashvili (pKP) equation delineates the development of small-amplitude, nonlinear, long waves characterized by a gradual variation in the transverse coordinate. The B-type KP equation outlines the relationships among exponentially localized shapes and was employed as a representation for shallow water waves and plasma physics. In this paper, we consider the combined pKP-BKP integrable equation. We discuss the multiple solitons of a newly proposed (3+1)-dimensional combined pKP-BKP integrable equation. We use the Hirota bilinear (HB) form of the considered equation to deduce fission process in higher order solitons with different orders. Moreover, the breather dynamics and its interaction with other solitons are investigated via HB. The lump solution and its interaction with first order and fourth order kink soliton is studied.

Bright solitons and interaction in the higher-order Gross-Pitaevskii equation investigated with Hirota's bilinear method

In this paper, we investigate bright solitons and their interactions in trapless Bose-Einstein condensate described by a one-dimensional Gross-Pitaevskii equation in the presence of higher-order nonlinearity. By constructing appropriate Hirota bilinear form of the problem, we derive the one- and two-bright soliton solutions where the effects of the higher-order interaction term are discussed in details. The profile of different solutions obtained clearly presents the phenomenon of soliton interaction that embodies the properties of soliton. It also highlights the impact of higher-order interactions that plays the role of wave amplification/compression resulting from the condensate. The theoretical results confirm that Hirota bilinear method is an efficient and interesting tool for the analysis of nonlinearity in physical science. In addition, the higher-order interactions have significant effects on the stabilization process of Bose-Einstein condensates.