The Andreev-Koebe-Thurston circle packing theorem is generalized and improved in two ways. First, we get simultaneous circle packings of the map and its dual map so that, in the corresponding straight-line representations of the map and the dual, any two edges dual to each other are perpendicular. Necessary and sufficient condition for a map to have such a primal-dual circle packing representat...

In Section 2, we give preliminaries on f-Kenmotsu manifolds. The concept of f-Kenmotsu manifold, where f is a real constant, appears for the first time in the paper of Jannsens and Vanhecke 1 . More recently, Olszak and Roşca 2 defined and studied the f-Kenmotsu manifold by the formula 2.3 , where f is a function on M such that df ∧ η 0. Here, η is the dual 1-form corresponding to the character...

We compute the number of self-dual rooted maps with n edges. We also compute the number of 2-connected and 3-connected selfdual rooted maps, and show that the latter are counted by the Fine numbers. © 2013 Elsevier Ltd. All rights reserved.

A restriction category is an abstract formulation for a category of partial maps, defined in terms of certain specified idempotents called the restriction idempotents. All categories of partial maps are restriction categories; conversely, a restriction category is a category of partial maps if and only if the restriction idempotents split. Restriction categories facilitate reasoning about parti...

We investigate the end spaces of infinite dual graphs. We show that there exists a natural homeomorphism between the end spaces of a graph and its dual, and that this homeomorphism maps thick ends to thick ends. Along the way, we prove that Tutte-connectivity is invariant under taking

We study an area preserving map of the exterior of a smooth convex curve in the hyperbolic plane, defined by a natural geometrical construction and called the dual billiard map. We consider two problems: stability and the area spectrum. The dual billiard map is called stable if all its orbits are bounded. We show that both stable and unstable behaviours may occur. If the map at infinity has a h...

The notion of strongly Lie zero-product preserving maps on normed algebras as a generalization of Lie zero-product preserving maps are dened. We give a necessary and sufficient condition from which a linear map between normed algebras to be strongly Lie zero-product preserving. Also some hereditary properties of strongly Lie zero-product preserving maps are presented. Finally the second dual of...

Given a self–dual map on the sphere, the collection of its self– dual permutations generates a transformation group in which the map automorphism group appears as a subgroup of index two. A careful examination of this pairing yields direct constructions of self–dual maps and provides a classification of self–dual maps.

We formulate and study a new coarse (co-)assembly map. It involves a modification of the Higson corona construction and produces a map dual in an appropriate sense to the standard coarse assembly map. The new assembly map is shown to be an isomorphism in many cases. For the underlying metric space of a group, the coarse co-assembly map is closely related to the existence of a dual Dirac morphis...

introduce a multi-scale metric on a space equipped with a diffusion semigroup. We prove, under some technical conditions, that the norm dual to the space of Lipschitz functions with respect to this metric is equivalent to two other norms, one of which is a weighted sum of the averages at each scale, and one of which is a weighted sum of the difference of averages across scales. The notion of 's...