Junya Takahashi

Pareto optimality for multiobjective linear fractional programming problems with fuzzy parameters

Abstract We focus on multiobjective linear fractional programming problems with fuzzy parameters and extend the ordinary Pareto optimality concepts based on the concepts of possibility and necessity for fuzzy numbers. Using the four indices for ranking two fuzzy numbers, four types of Pareto optimality are defined, and the relationships among them are examined in detail. These concepts can be viewed as quite generalized versions of the well-known Pareto optimality concepts, and the generalized Pareto optimal solutions for the multiobjective linear fractional programming problems with fuzzy parameters may be obtained on the basis of the simplex method of linear programming.

Collapsing of connected sums and the eigenvalues of the Laplacian

Abstract We study the behavior of the eigenvalues of the Laplacian acting on functions when one side of a connected sum of two closed Riemannian manifolds collapses to a point. We prove that the eigenvalues converge to those of the limit space, by using the method of Anne and Colbois. From this, we obtain a gluing theorem for the eigenvalues.

Finding Shortest Non-Crossing Rectilinear Paths in Plane Regions

Let A be a plane region which is bounded by an outer rectangle and an inner one and has r rectangular obstacles inside the region. Let k terminal pairs lie on the outer and inner rectangular boundaries. This paper presents an efficient algorithm which finds k “non-crossing” rectilinear paths in the plane region A, each connecting a terminal pair without passing through any obstacles, whose total length is minimum. Non-crossing paths may share common points or line segments but do not cross each other in the plane. The algorithm runs in time O(n log n) where n=r+k.

Algorithms for Finding Non-Crossing Paths with Minimum Total Length in Plane Graphs

Let G be an undirected plane graph with non-negative edge length, and let k terminal pairs lie on two specified face boundaries. This paper presents an algorithm for finding k “non-crossing paths” in G, each connecting a terminal pair, whose total length is minimum. Here “non-crossing paths” may share common vertices or edges but do not cross each other in the plane. The algorithm runs in time O(n log n) where n is the number of vertices in G.

Partial collapsing and the spectrum of the Hodge–de Rham operator

The goal of the present paper is to calculate the limit spectrum of the Hodge-de Rham operator under the perturbation of collapsing one part of a manifold obtained by gluing together two manifolds with the same boundary. It appears to take place in the general problem of blowing up conical singularities as introduced in \cite{Maz} and \cite{Row1,Row2}.