On Some Results in Fuzzy Length Space

In this paper, depending on the notion of fuzzy length space we define the Cartesian product of two fuzzy length spaces. we proved that the Cartesian product of two fuzzy length spaces is a fuzzy length space. More accurately, the Cartesian product of two complete fuzzy length spaces is proved to be a complete fuzzy length space. Furthermore, the definitions of sequentially fuzzy compact fuzzy length space, countably fuzzy compact fuzzy length space, locally fuzzy compact fuzzy length space are introduced, and theorems related to them are proved.

Fuzzy Open Mapping and Fuzzy Closed Graph Theorems in Fuzzy Length Space

The theory of fuzzy set includes many aspects that regard important and significant in different fields of science and engineering in addition to there applications. Fuzzy metric and fuzzy normed spaces are essential structures in the fuzzy set theory. The concept of fuzzy length space has been given analogously and the properties of this space are studied few years ago. In this work, the definition of a fuzzy open linear operator is presented for the first time and the fuzzy Barise theorem is established to prove the fuzzy open mapping theorem in a fuzzy length space. Finally, the definition of a fuzzy closed linear operator on fuzzy length space is introduced to prove the fuzzy closed graph theorem.

The length metric on the set of orthogonal projections and new estimates in the subspace perturbation problem

We consider the problem of variation of spectral subspaces for bounded linear self-adjoint operators in a Hilbert space. Using metric properties of the set of orthogonal projections as a length space, we obtain a new estimate on the norm of the operator angle associated with two spectral subspaces for isolated parts of the spectrum of the perturbed and unperturbed operators, respectively. In particular, recent results by Kostrykin, Makarov and Motovilov from [Proc. Amer. Math. Soc. 131, 3469–3476] and [Trans. Amer. Math. Soc. 359, 77–89] are strengthened.

The gradient structure of the mean curvature flow

The concept of curve of maximal slope, a generalized notion of gradient flow, is extended to the setting of length spaces, which includes all metric spaces. This extended definition is used to show that curves of maximal slope in a metric space do not depend on the full metric, but only on the concept of curve length generated by it. Subsequently, it is shown that a length space can be constructed to describe

The Boundary at Infinity of a Rough CAT(0) Space

We develop the boundary theory of rough CAT(0) spaces, a class of length spaces that contains both Gromov hyperbolic length spaces and CAT(0) spaces. The resulting theory generalizes the common features of the Gromov boundary of a Gromov hyperbolic length space and the ideal boundary of a complete CAT(0) space. It is not assumed that the spaces are geodesic or proper