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Volume 10 (2026)

Sergey E. Stepanov1
1Department of Mathematics, Finance University, 125468 Moscow, Leningradsky Prospect, 49-55, Russian Federation
Abstract:

We establish a localized Bochner-type rigidity theorem for harmonic maps between Riemannian manifolds. Let f : (M, g) → (, ) be a harmonic map from a compact manifold. Instead of assuming global nonpositivity of the sectional curvature of the target manifold, we impose a curvature bound localized along the image f(M), expressed in terms of the maximal sectional curvature encountered along this image. We prove that if the minimal Ricci curvature of the domain dominates this image–dependent curvature bound through a quantitative curvature pinching inequality involving the maximal energy density of f, then the map must be constant. In the critical case of equality, we obtain a homothetic classification: the differential of f is parallel and the image f(M) is totally geodesic. Thus, the theorem replaces global curvature sign assumptions by an image–dependent curvature domination principle and provides a localized analogue of classical Yano–Ishihara–type rigidity results.

Baver Okutmustur1, Cornelis Vuik2, Kadir Yigit1
1Department of Mathematics, Middle East Technical University, Ankara, Turkiye
2Delft Institute of Applied Mathematics, Delft University of Technology, Delft, The Netherlands
Abstract:

This work presents a novel investigation of the recently derived relativistic Burgers-FLRW model, a scalar hyperbolic balance law with nontrivial source terms, using the Moving Mesh Method (MMM). Building on an MMM framework originally developed for hyperbolic conservation laws, we examine a range of monitor and smoothing functions to identify effective combinations for accurately resolving key solution features while reducing computational error. Numerical experiments compare the MMM with Adaptive Mesh Refinement (AMR) and uniform mesh discretizations. An L1-error analysis is used to study the effect of different monitor functions, explore the role of various β parameters, and directly compare the performance of the MMM and AMR strategies. The results show that both adaptive approaches provide higher accuracy and better efficiency than uniform meshes, while also offering a clear comparison between MMM and AMR and practical insight into mesh adaptation for scalar balance laws.

Chun-Ying He1, Feng Qi2
1School of Mathematics and Physics, Hulunbuir University, Hulunbuir, Inner Mongolia, 021008, China
217709 Sabal Court, University Village, Dallas, TX 75252-8024, USA
Abstract:

In the work, by establishing integral representations for a class of specific Maclaurin power series, the authors restate recently-published results related to the normalized remainder of the Maclaurin power series of the exponential function, alternatively prove some of these results, and pose some new problems in terms of the majorizing relations.

Fabio Silva Botelho1
1Department of Mathematics, Federal University of Santa Catarina, UFSC, Florianopolis, SC – Brazil
Abstract:

This article develops a formal proof of Castilgiano Theorem in an elasticity theory context. The results are based on standard tools of applied functional analysis and calculus of variations. It is worth mentioning such results here presented may be easily extended to a non-linear elasticity context. Finally, in the last section we present a numerical example in order to illustrate the results applicability.

Elif N. Yıldırım1, Fatih Nuray2
1Department of Mathematics, Istanbul Commerce University, Istanbul, Türkiye
2Department of Mathematics, Afyon Kocatepe University, 03200, Afyonkarahisar, Türkiye
Abstract:

In this paper, we introduce and investigate the concept of statistically bornological convergence for sequences of subsets in metric spaces. This notion combines the localization principle of bornological convergence with the asymptotic flexibility of statistical convergence. A sequence of sets is said to be statistically bornologically convergent if the bornological inclusion conditions hold for a set of indices with natural density one. We provide examples distinguishing this concept from classical bornological and Hausdorff convergence. Under appropriate boundedness assumptions, we establish a functional characterization using excess functionals. We prove stability under bi-Lipschitz embeddings using a direct inclusion-based approach with properly defined pushforward ideals, and establish a subsequence theorem via the diagonal density lemma. The relationship with Wijsman statistical convergence is clarified.

David Ellerman1
1University of Ljubljana, Slovenia
Abstract:

The theory of q-analogs develops combinatorial formulas for finite vector spaces over a finite field with q elements–in analogy with formulas for finite sets (the limiting case q = 1). A direct-sum decomposition of a finite vector space is the vector-space analogue of a set partition. This paper uses elementary counting methods to derive direct formulas for the number of direct-sum decompositions (DSDs) that play the role of the Stirling and Bell numbers for set partitions. In particular, we give a signature-based counting formula for DSDs and recover the standard set-partition formulas in the limit q → 1. We also develop new companion formulas that enumerate DSDs with m blocks in an n-dimensional vector space over GF(q) such that a specified nonzero vector lies in one of the blocks, together with the corresponding totals over all numbers of blocks. Initial computations are included for the case q = 2, with hand-checkable low-dimensional examples, internal consistency checks, and applications to the pedagogical model of quantum mechanics over 2 (QM/Sets). Four related sequences for q = 2 are recorded in the On-Line Encyclopedia of Integer Sequences

B. Ravi1, Christophe Chesneau2
1Government College for Men – Anantapur, 515001, Andhra Pradesh, India
2Department of Mathematics, LMNO, University of Caen-Normandie, 14032 Caen, France
Abstract:

This paper presents several new integral formulas inspired by classical results and problems in the existing literature. We present a simpler alternative proof of a well-known technical result that avoids the use of the digamma function. Additionally, we derive a set of integral formulas involving finite series in the numerator, generalizing existing formulas.

C. I. Nkeki1, I. A. Mbarie2
1Department of Mathematics, Faculty of Physical Sciences, University of Benin, Benin City, Edo State, Nigeria
2Institute of Child Health, College of Medical Sciences, University of Benin, Benin City, Edo State, Nigeria
Abstract:

This paper considers mathematical modelling and stability analysis of Varicella-Zoster Virus (VZV) disease model in a homogeneous population that is structured as a class of susceptible-exposed-quarantined-infected-hospitalized-recovered with immunity. In this paper, the infectious classes are the exposed, quarantined, infected and hospitalized. The infected class is further subdivided into three subclasses: incubation, prodromal and active classes of VZV. The infectious rate of VZV at the incubation, prodromal, active and hospitalization stages are discussed. The aim of this paper is to determine the significance of having the subclasses of the infected class, and the role these subclasses of the infected class and contact rate play in the spread of chickenpox in the population. The basic reproduction number of our VZV model is obtained. Also, we discuss the global stability of the disease-free equilibrium and the local stability of the endemic equilibrium in the feasible region of the VZV model. Some numerical simulations are carried out to valid the models in this paper, and it is found that the subclasses of the infected class and contact rate play distinct and significant role in the spread of chickenpox in a population.

Constantin Fetecau1, Dumitru Vieru2,3
1Academy of Romanian Scientists, 3 Ilfov, Bucharest 050044, Romania
2Department of Mathematics, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, 602105, Tamil Nadu, India
3Department of Theoretical Mechanics, Technical University of Iasi, Iasi 700050, Romania
Abstract:

Axial flow of incompressible Burgers fluids in an infinite circular cylinder that slides along its symmetry axis with an arbitrary time-dependent velocity is analytically and numerically investigated in the presence of a constant magnetic field. Analytic expressions are established for the dimensionless velocity field and the non-trivial shear stress. For validation, distinct expressions are determined for the fluid velocity and their equivalence in a concrete case is graphically proved. The influence of relaxation time and of Burgers and magnetic parameters on the fluid velocity is graphically highlighted and discussed. It was found that, outside a small vicinity of the symmetry axis of cylinder, the fluid flows slower in the presence of the magnetic field. The oscillatory translational movement of the cylinder induces a motion with oscillating velocity of the fluid. If the cylinder velocity tends to a constant value for large values of the time t, the fluid motion becomes steady in time and the corresponding steady solutions are determined.

Abimbola Abolarinwa1
1Department of Mathematics, University of Lagos, Akoka, Lagos State, Nigeria
Abstract:

In this paper we establish a new nonlinear variable exponent Picone-type identities for p(x)-biharmonic operator on a general stratified Lie group. As applications, eigenvalue properties, domain monotonicity, Barta-type estimate are proved for p(x)-sub-biharmonic operator. Furthermore, a Díaz-Saa-type inequality is proved and applied to study results on uniqueness of positive solutions of quasilinear elliptic equations involving variable exponent p(x)-sub-biharmonic operator.