Analele ştiinţifice ale Universităţii "Ovidius" Constanţa. Seria Matematică Feed

Pointwise hemi-slant warped product submanifolds in nearly Kaehler manifolds

Sat, 29 Nov 2025 00:00:00 GMT

In this paper, we introduce the notion of pointwise hemi-slant sub-manifolds of nearly Kaehler manifolds. Further, we study their warped products and prove the necessary and sufficient condition that a point-wise hemi-slant submanifold to be a warped product manifold. Also, we establish a sharp inequality for the pointwise hemi-slant warped product submanifolds of the form M = M⊥ ×f Mθ which is mixed totally geodesic in an arbitrary nearly Kaehler manifold ~M. The equality case is also discussed.

Extension of Paul Erdős graph on hypergroups

Sat, 29 Nov 2025 00:00:00 GMT

This paper introduces ultra non-commutative graphs derived from ultra non-commutative hypergroups. Vertices represent ultra non -commutative elements of the hypergroup U, defined as AU = {x ∈ U |Ǝy ∈ U, y ○ x ∩ x ○ y = ∅}. An edge connects vertices x and y if and only if y ○ x ∩ x ○ y = ∅. We investigate properties of the associated graph Γ(U), including connectivity, Hamiltonian conditions, and planarity.

Almost and quasi-Leinster groups

Sat, 29 Nov 2025 00:00:00 GMT

In this paper, we extend the parallelism between perfect numbers and Leinster groups, by introducing the new concepts of almost and quasi-Leinster groups which parallel almost and quasi-perfect numbers. These are small deviations from perfect numbers; very few results and/or examples are known about them. We investigate nilpotent almost/quasi-/Leinster groups and find some examples and conditions for the existence of such groups for classes of nonnilpotent groups: ZM (Zassenhaus metacyclic) groups, affine groups, dihedral groups and dicyclic groups.

An examination of the fundamental solution and Green’s function in orthotropic photothermoelastic with diffusion under the MGT model

Sat, 29 Nov 2025 00:00:00 GMT

The objective of this paper is to investigate the fundamental solution and Green’s function in a semi-infinite orthotropic photothermoelastic diffusion medium that is based on the Moore-Gibson-Thompson heat equation (MGTPWD). First, we transform the governing equations into a two-dimensional format and then make dimensionless to derive the general solution for the MGTPWD model. Based on the general solution, nine new harmonic functions were used to build the fundamental solution and Green’s function for a steady point heat source on the surface and inside of a semi-infinite material in the proposed model. The elementary functions are used to express the components of displacements, stress, temperature distribution, carrier density distribution and chemical potential. The physical field quantities (stress, temperature distribution, carrier density distribution and chemical potential) are computed numerically and presented graphically to depict diffusion impact. A unique case have been deduced and compared with earlier known results. The results acquired can be used to delineate a variety of semiconductor elements during the coupled photo thermoelastic impact and can also be applied in the material and engineering sciences.

A mathematical note about a FLRW universe embedded in a universe without time

Sat, 29 Nov 2025 00:00:00 GMT

In this paper we propose to study a six-dimensional Friedmann-Lemaître-Robertson-Walker (FLRW) universe without time. The way we study this timeless universe is the classic one: we highlight future oriented time-like loops and closed chains of future oriented time-like curves. Inside this six-dimensional FLRW universe it is embedded a four-dimensional classical FLRW universe.

Square-difference factor absorbing submodules of modules over commutative rings

Sat, 29 Nov 2025 00:00:00 GMT

Let R be a commutative ring with identity and M an unitary R-module. Recently, in [5], Anderson, Badawi and Coykendalla defined a proper ideal I of R to be a square-difference factor absorbing ideal (sdf-absorbing ideal) of R if whenever a2 − b2 ∈ I for 0 ≠ a, b ∈ R, then a + b ∈ I or a − b ∈ I. Generally, this article is devoted to introduce and study square-difference factor absorbing submodules. A proper submodule N of M is called square-difference factor absorbing (sdf-absorbing) in M if whenever m ∈ M and a, b ∈ R\AnnR(m) such that (a2 − b2)m ∈ N, then (a + b)m ∈ N or (a − b)m ∈ N. Many properties, examples and characterizations of sdf-absorbing submodules are introduced, especially in multiplication modules. Comparing this new class of submodules with classical prime submodules, we present new characterizations for von-Neumann regular modules in terms of sdf-absorbing submodules. Further characterizations of some special modules in which every nonzero proper submodule is sdf-absorbing are investigated. Finally, the sdf-absorbing submodules in amalgamated modules are studied.

A note on conformal mappings onto mutually non-overlapping domains

Sat, 29 Nov 2025 00:00:00 GMT

In the paper, an approach is proposed that allowed to establish new upper estimates for products of inner radii of mutually non-overlapping domains.

The characterization of Nelson algebras by Sheffer stroke

Sat, 29 Nov 2025 00:00:00 GMT

In this study, Sheffer stroke Nelson algebras (briefly, s-Nelson algebras), (ultra) ideals, quasi-subalgebras, quotient sets, and fuzzy structures on these algebraic structures are introduced. The relationships between s-Nelson and Nelson algebras are analyzed. It is also shown that an s-Nelson algebra is a bounded distributive modular lattice, and the family of all ideals forms a complete distributive modular lattice. A congruence relation on an s-Nelson algebra is determined by an ideal and quotient s-Nelson algebras are constructed by this congruence relation. Finally, it is indicated that a quotient s-Nelson algebra constructed by the ultra ideal is totally ordered and that the cardinality of the quotient is less than or equal to 2.

Weak MPCEP and *CEPMP inverses

Sat, 29 Nov 2025 00:00:00 GMT

We generalize the systems of equations, which introduced the MPCEP and *CEPMP inverses, using a minimal rank weak Drazin inverse and a minimal rank right weak Drazin inverse. In order to solve new generalized systems of matrix equations, we define new types of generalized inverses, the so-called weak MPCEP and *CEPMP inverses. The DMP, MPD, MPCEP and *CEPMP inverses are particular kinds of weak MPCEP and *CEPMP inverses. We show characterizations and formulae for weak MPCEP and *CEPMP inverses as well as their perturbation results. As application of weak MPCEP and *CEPMP inverses, we prove solvability of certain linear equations and recover the main application of the Moore–Penrose inverse.

Steiner distances in generalized corona products

Sat, 29 Nov 2025 00:00:00 GMT

The Steiner distance of a subset of vertices in a graph is the minimum size among all the connected subgraphs containing this subset. This paper focuses on the study of Steiner distances in both generalized vertex corona (GVC) and generalized edge corona (GEC) products, and the relationship with their corresponding center and outer graphs. Particularly, we show how Steiner distances in GEC products can be computed from those ones in GVC products, and we also establish sharp bounds for their Steiner numbers, eccentricities, radii, diameters and k-Wiener indices. In this way, we extend some known results on corona products.

Numerical solution of nonlinear reaction advection-diffusion equation using the modified collocation method

Tue, 03 Jun 2025 00:00:00 GMT

This article presents a numerical solution of the nonlinear reaction-advection-diffusion equation with specified initial and boundary conditions using a modified cubic B-spline collocation method. Nonlinear terms are linearised using the Crank-Nicholson method. The derived numerical scheme is shown to be unconditionally convergent through stability analysis. The accuracy of the numerical scheme has been verified by its application to the three standard instances. The numerical findings are then compared with the existing analytical results by employing the l2 and l∞ error norms. The main feature of this article is the graphical presentation of the numerical solution of the concerned model for different sets of advection, diffusion and reaction coefficients to show the effect on the solute profile when advection and diffusion terms are both nonlinear. Nonlinear reaction-advection-diffusion equations have found applications in diverse areas like groundwater and water pollution studies.

The topology of the generic polar curve and the Zariski invariant for branches of genus one

Tue, 03 Jun 2025 00:00:00 GMT

We study, for plane complex branches of genus one, the topological type of its generic polar curve, as a function of the semigroup of values and the Zariski invariant of the branch. We improve some results given by Casas-Alvero in 2023, since we filter the topological type fixed for the branch by the possible values of Zariski invariants.

On some differential inclusions with anti-periodic solutions

Tue, 03 Jun 2025 00:00:00 GMT

In this paper, we investigate a class of second- and first-order differential inclusions, along with an algebraic inclusion, all subject to anti-periodic boundary conditions in a real Hilbert space. These problems, denoted as (Pɛμ)ap, (Pµ)ap, and (E00), involve operators that are odd, maximal monotone, and possibly set-valued. The second- and first-order differential inclusions are parameterized by two nonnegative constants, ɛ and µ, which affect the behavior of the differential terms. We establish the existence and uniqueness of strong solutions for the problems (Pɛµ)ap and (Pµ)ap, as well as for the algebraic inclusion (E00). Additionally, we prove the continuous dependence of the solution to problem (Pɛµ)ap on parameters ɛ and µ. We also provide approximation results for the solutions to (Pµ)ap and (E00) as the parameters ɛ and µ approach zero. Finally, we discuss some applications of our theoretical results.

On topological quotient hyperrings and α*-relation

Tue, 03 Jun 2025 00:00:00 GMT

In this research, we first introduce the concept of a topological Krasner hyperring and then proceed to investigate its properties. By applying relative topology to subhyperrings, we analyze the properties associated with them. In other words, the aim is to utilize specific topologies to identify the diverse substructural characteristics of this type of hyperring. Additionally, we examine the quotient topology resulting from an interesting relation on the discussed spaces to understand how this relation influences the topological structure of the hyperring. Finally, we demonstrate that the topological Krasner hyperring induced by τα, which is the finest and strongest topology on ℋ, ultimately forms a ring. In summary, this research not only analyzes the structural properties of these hyperrings but also examines, from a topological perspective, how different relations impact this structure, proving that the resulting topology is strong enough to form a ring.

On the zero-free region and the distribution of zeros of the prime zeta function

Tue, 03 Jun 2025 00:00:00 GMT

The prime zeta function is one of the most under-researched varieties of the class. Very little is known about the irregular distribution of its zeros. The presented study aims - albeit partially - to fill the gap in our understanding of the subject. We consider the zero-free region of the prime zeta function and verify statistically certain conjectures regarding the distribution patterns of the zeroes of the prime zeta function.

Evaluating AT,S(2) A_{T,S}^{\left( 2 \right)} Matrix Inverses from full-rank Singular Value Decomposition

Tue, 03 Jun 2025 00:00:00 GMT

Based on the compact SVD decomposition of the full rank of a predetermined matrix M, a method for calculating the inverses AT,S(2) A_{T,S}^{\left( 2 \right)} of matrix A is derived. As a consequence, the advantages of compact single value decompositions were developed with this new method. The method is then extended to a set of polynomial matrices. As a result, an algorithm is proposed for effective symbolic computation of AT,S(2) A_{T,S}^{\left( 2 \right)} inverses of a polynomial matrix. Some implementation details and comparative computation times compared to other similar methods are shown to illustrate the efficiency of the algorithm.

Is there a polynomial D(2X + 1)-quadruple?

Tue, 03 Jun 2025 00:00:00 GMT

In this paper, we show that there does not exist a polynomial D(2X+ 1)-quadruple {a, b, c, d}, such that 0 < a < b < c < d and deg d = deg b.

Necessary conditions and sufficient conditions for h-dichotomy of skew-evolution cocycles in Banach spaces

Tue, 03 Jun 2025 00:00:00 GMT

This study focuses on the problem of h-dichotomy for skew-evolution cocycles within Banach spaces. It outlines the necessary conditions and sufficient conditions for this framework, along with those for the notable concepts like exponential dichotomy, polynomial dichotomy and uniform h-dichotomy. These conditions are established through the use of strongly invariant families of projectors.

Approximation of fractional derivatives by Brass-Stancu operators

Tue, 03 Jun 2025 00:00:00 GMT

In this paper, we study uniform approximation of fractional derivatives in Caputo sense by Brass-Stancu operators. For the rate of approximation, we give some estimates in terms of the modulus of continuity.

An alternate measure of the cumulative residual Sharma-Taneja-Mittal entropy

Tue, 03 Jun 2025 00:00:00 GMT

We define a new alternate measure of the cumulative residual Sharma-Taneja-Mittal entropy. For this measure, there are given upper and lower bounds, is introduced a consistent test based on the uniform distribution and some concrete numerical examples are formulated.