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We are concerned with orderable groups and particularly those with orderings invariant not only under multiplication, but also under a given automorphism or family of automorphisms. Several applications to topology are given: we prove that…

Group Theory · Mathematics 2014-10-01 Dale Rolfsen , Bert Wiest

We use differential forms on loop spaces to prove that the fundamental group of certain geometric transformation groups is infinite. Examples include both finite and infinite dimensional Lie groups. The finite dimensional examples are the…

Differential Geometry · Mathematics 2025-10-03 Yoshiaki Maeda , Steven Rosenberg

This paper studies rotational virtual knot theory and its relationship with quantum link invariants. Every quantum link invariant for classical knots and links extends to an invariant of rotational virtual knots and links. The paper sets up…

Geometric Topology · Mathematics 2015-12-08 Louis H. Kauffman

This paper studies an algebraic invariant of virtual knots called the biquandle. The biquandle generalizes the fundamental group and the quandle of virtual knots. The approach taken in this paper to the biquandle emphasizes understanding…

Geometric Topology · Mathematics 2007-05-23 David Hrencecin , Louis H. Kauffman

Networks often possess mesoscale structures, and studying them can yield insights into both structure and function. It is most common to study community structure, but numerous other types of mesoscale structures also exist. In this paper,…

Physics and Society · Physics 2014-03-21 Sang Hoon Lee , Mihai Cucuringu , Mason A. Porter

Networks may, or may not, be wired to have a core that is both itself densely connected and central in terms of graph distance. In this study we propose a coefficient to measure if the network has such a clear-cut core-periphery dichotomy.…

Physics and Society · Physics 2007-05-23 Petter Holme

Let $\Gamma_g$ be the fundamental group of a closed connected orientable surface of genus $g\geq2$. We introduce a combinatorial structure of "core surfaces", that represent subgroups of $\Gamma_g$. These structures are (usually)…

Group Theory · Mathematics 2022-06-22 Michael Magee , Doron Puder

In this paper we describe the fundamental group-scheme of a proper variety fibered over an abelian variety with rationally connected fibers over an algebraically closed field. We use old and recent results for the Nori fundamental…

Algebraic Geometry · Mathematics 2020-04-10 Rodrigo Codorniu Cofré

We give a topological interpretation of the core group invariant of a surface embedded in S^4. We show that the group is isomorphic to the free product of the fundamental group of the double branch cover of S^4 with the surface as a…

Geometric Topology · Mathematics 2007-05-23 Jozef H. Przytycki , Witold Rosicki

We describe the structure of diffeological bundle of non formal classical pseudo-differential operators over formal ones, and its structure group. For this, we give few results on diffeological principal bundles with (a priori) no local…

Differential Geometry · Mathematics 2023-08-21 Jean-Pierre Magnot

We introduce several novel and computationally efficient methods for detecting "core--periphery structure" in networks. Core--periphery structure is a type of mesoscale structure that includes densely-connected core vertices and…

Discrete Mathematics · Computer Science 2016-11-08 Mihai Cucuringu , Puck Rombach , Sang Hoon Lee , Mason A. Porter

Starting from considering deeper relationship between conjugacy classes and irreducible representations of a finite group $G$, we find some quite simple $R-$matrice defined by using finite groups. This construction produces many sets (or…

Geometric Topology · Mathematics 2018-09-25 Zhi Chen

In many real network systems, nodes usually cooperate with each other and form groups, in order to enhance their robustness to risks. This motivates us to study a new type of percolation, group percolation, in interdependent networks under…

Physics and Society · Physics 2018-03-21 Zexun Wang , Dong Zhou , Yanqing Hu

Many real-world networks exhibit a multicores-periphery structure, with densely connected vertices in multiple cores surrounded by a general periphery of sparsely connected vertices. Identification of the multicores-periphery structure can…

Social and Information Networks · Computer Science 2019-05-08 Bowen Yan , Jianxi Luo

Networks can have various types of mesoscale structures. One type of mesoscale structure in networks is core-periphery structure, which consists of densely-connected core nodes and sparsely-connected peripheral nodes. The core nodes are…

Social and Information Networks · Computer Science 2025-06-17 Theodore Y. Faust , Mason A. Porter

The writhe polynomial is a fundamental invariant of an oriented virtual knot. We introduce a kind of local moves for oriented virtual knots called shell moves. The first aim of this paper is to prove that two oriented virtual knots have the…

Geometric Topology · Mathematics 2019-05-10 Takuji Nakamura , Yasutaka Nakanishi , Shin Satoh

We define formal orbifolds over an algebraically closed field of arbitrary characteristic as curves together with some branch data. Their \'etale coverings and their fundamental groups are also defined. These fundamental group approximates…

Algebraic Geometry · Mathematics 2015-12-11 Manish Kumar , A. J. Parameswaran

We consider the group of unrestricted virtual braids, describe its structure and explore its relations with fused links. Also, we define the groups of flat virtual braids and virtual Gauss braids and study some of their properties, in…

Geometric Topology · Mathematics 2016-03-04 Valeriy Bardakov , Paolo Bellingeri , Celeste Damiani

The knot group is the fundamental group of a knot or link complement. A necessary and sufficient conditions for a group to be realized as the knot group of some link was provided. This result was shown using the closed braid method.…

Geometric Topology · Mathematics 2025-02-25 Jumpei Yasuda

We show several geometric and algebraic aspects of a necklace: a link composed with a core circle and a series of circles linked to this core. We first prove that the fundamental group of the configuration space of necklaces (that we will…

Group Theory · Mathematics 2018-10-30 Paolo Bellingeri , Arnaud Bodin