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# Lifting Diffeomorphisms to Vector Bundles

Studia Scientiarum Mathematicarum Hungarica
Authors:
Jaime Muñoz Masqué
,
, and
Ignacio Sánchez Rodríguez

Criteria for a diffeomorphism of a smooth manifold M to be lifted to a linear automorphism of a given real vector bundle p : V → M, are stated. Examples are included and the metric and complex vector-bundle cases are also considered.

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# A Remark on Nefness of Divisors on Surfaces of General Type

Studia Scientiarum Mathematicarum Hungarica
Authors:
Debojyoti Bhattacharya
and
Joyentanuj Das

Let X be an irreducible complex projective variety of dimension n ≥ 1. Let D be a Cartier divisor on X such that Hi(X, OX (mD)) = 0 for m > 0 and for all i > 0, then it is not true in general that D is a nef divisor (cf. [4]). Also, in general, effective divisors on smooth surfaces are not necessarily nef (they are nef provided they are semiample). In this article, we show that, if X is a smooth surface of general type and C is a smooth hyperplane section of it, then for any non-zero effective divisor D on X satisfying H1(X, OX (mD)) = 0 for all m > C.KX , D is a nef divisor.

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# Gel’fand Γ-Semirings

Mathematica Pannonica
Authors:
Tilak Raj Sharma
and
Hitesh Kumar Ranote

In this paper, we introduce the notion of a Gel’fand Γ-semiring and discuss the various characterization of simple, k-ideal, strong ideal, t-small elements and additively cancellative elements of a Gel’fand Γ-semiring R, and prove that the set of additively cancellative elements, set of all t-small elements of R and set of all maximal ideal of R are strong ideals. Further, let R be a simple Gel’fand Γ-semiring and 1 ≠ tR. Let M be the set of all maximal left (right) ideals of R. Then an element x of R is t-small if and only if it belongs to every maximal one sided left (right)ideal of R containing t.

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# Operator Convexity of an Integral Transform with Applications

Mathematica Pannonica
Author:
Silvestru Sever Dragomir

For a continuous and positive function w(λ), λ > 0 and μ a positive measure on (0, ∞) we consider the following integral transform

$D w , μ t : = ∫ 0 ∞ w λ λ + t − 1 d μ λ ,$

where the integral is assumed to exist for t > 0.

We show among others that D(w, μ) is operator convex on (0, ∞). From this we derive that, if f : [0, ∞) → R is an operator monotone function on [0, ∞), then the function [f(0) -f(t)] t -1 is operator convex on (0, ∞). Also, if f : [0, ∞) → R is an operator convex function on [0, ∞), then the function $f 0 + f + ′ 0 t − f t t − 2$ is operator convex on (0, ∞). Some lower and upper bounds for the Jensen’s difference

$D w , μ A + D w , μ B 2 − D w , μ A + B 2$

under some natural assumptions for the positive operators A and B are given. Examples for power, exponential and logarithmic functions are also provided.

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# Perfect Solutions to Problems on Common Transversals and Submodular Functions from Welsh’s 1976 Text Matroid Theory

Mathematica Pannonica
Author:
Jonathan David Farley

Problem 2 of Welsh’s 1976 text Matroid Theory, asking for criteria telling when two families of sets have a common transversal, is solved.

Another unsolved problem in the text Matroid Theory, on whether the “join” of two non-decreasing submodular functions is submodular, is answered in the negative. This resolves an issue first raised by Pym and Perfect in 1970.

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# Algebra of Data Reconciliation

Studia Scientiarum Mathematicarum Hungarica
Authors:
Elod P. Csirmaz
and
Laszlo Csirmaz

With distributed computing and mobile applications becoming ever more prevalent, synchronizing diverging replicas of the same data is a common problem. Reconciliation – bringing two replicas of the same data structure as close as possible without overriding local changes – is investigated in an algebraic model. Our approach is to consider two sequences of simple commands that describe the changes in the replicas compared to the original structure, and then determine the maximal subsequences of each that can be propagated to the other. The proposed command set is shown to be functionally complete, and an update detection algorithm is presented which produces a command sequence transforming the original data structure into the replica while traversing both simultaneously. Syntactical characterization is provided in terms of a rewriting system for semantically equivalent command sequences. Algebraic properties of sequence pairs that are applicable to the same data structure are investigated. Based on these results the reconciliation problem is shown to have a unique maximal solution. In addition, syntactical properties of the maximal solution allow for an efficient algorithm that produces it.

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# Existence and Stability of Solutions for a Nonlinear Beam Equation with Internal Damping

Mathematica Pannonica
Authors:
Ducival Carvalho Pereira
,
Carlos Alberto Raposo
, and
Huy Hoang Nguyen

This manuscript deals with the global existence and asymptotic behavior of solutions for a Kirchhoff beam equation with internal damping. The existence of solutions is obtained by using the Faedo-Galerkin method. Exponential stability is proved by applying Nakao’s theorem.

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# Hypersphere Having ΔIIx = Ax in E4

Mathematica Pannonica
Authors:
Erhan Güler
and
Kübra Yilmaz

We consider hypersphere x = x(u, v, w) in the four dimensional Euclidean space. We calculate the Gauss map, and the curvatures of it. Moreover, we compute the second Laplace-Beltrami operator the hypersphere satisfying ΔIIx = Ax, where A ϵ Mat (4,4).

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# A Marcinkiewicz Type Interpolation Theorem for Orlicz Spaces and Its Application

Mathematica Pannonica
Authors:
Xiaoqiang Xie
,
Xi Fu
, and
Changmin Li

In this paper, we show a Marcinkiewicz type interpolation theorem for Orlicz spaces. As an application, we obtain an existence result for a parabolic equation in divergence form.

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# Convex Bodies of Constant Width in Spaces of Constant Curvature and the Extremal Area of Reuleaux Triangles

Studia Scientiarum Mathematicarum Hungarica
Authors:
Károly J. Böröczky
and
Ádám Sagmeister

Extending Blaschke and Lebesgue’s classical result in the Euclidean plane, it has been recently proved in spherical and the hyperbolic cases, as well, that Reuleaux triangles have the minimal area among convex domains of constant width D. We prove an essentially optimal stability version of this statement in each of the three types of surfaces of constant curvature. In addition, we summarize the fundamental properties of convex bodies of constant width in spaces of constant curvature, and provide a characterization in the hyperbolic case in terms of horospheres.

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