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Modularity (networks)
Modularity is a measure of the structure of networks or graphs which measures the strength of division of a network into modules (also called groups, clusters or communities). Networks with high modularity have dense connections between the nodes within modules but sparse connections between nodes in different modules. Modularity is often used in optimization methods for detecting community structure in networks. Biological networks, including animal brains, exhibit a high degree of modularity. However, modularity maximization is not statistically consistent, and finds communities in its own null model, i.e. fully random graphs, and therefore it cannot be used to find statistically significant community structures in empirical networks. Furthermore, it has been shown that modularity suffers a resolution limit and, therefore, it is unable to detect small communities. Motivation Many scientifically important problems can be represented and empirically studied using networks. For e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gephi 0
Gephi ( ) is an open-source network theory, network analysis and network visualization, visualization software package written in Java on the NetBeans platform. History Initially developed by students of the University of Technology of Compiègne (UTC) in France, Gephi has been selected for the Google Summer of Code in 2009, 2010, 2011, 2012, and 2013. Its last version, 0.10.1 has been launched in 2023. Previous versions are 0.6.0 (2008), 0.7.0 (2010), 0.8.0 (2011), 0.8.1 (2012), 0.8.2 (2013), 0.9.0 (2015), 0.9.1 (2016) and 0.9.2 (2017). The Gephi Consortium, created in 2010, is a French non-profit corporation which supports development of future releases of Gephi. Members include SciencesPo, Linkfluence, WebAtlas, and Quid (encyclopedia), Quid. Gephi is also supported by a large community of users, structured on a discussion group and a forum and producing numerous blogposts, papers and tutorials. In November 2022, a lightweight web version of Gephi, Gephi lite, was announced. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamiltonian (quantum Mechanics)
In quantum mechanics, the Hamiltonian of a system is an operator corresponding to the total energy of that system, including both kinetic energy and potential energy. Its spectrum, the system's ''energy spectrum'' or its set of ''energy eigenvalues'', is the set of possible outcomes obtainable from a measurement of the system's total energy. Due to its close relation to the energy spectrum and time-evolution of a system, it is of fundamental importance in most formulations of quantum theory. The Hamiltonian is named after William Rowan Hamilton, who developed a revolutionary reformulation of Newtonian mechanics, known as Hamiltonian mechanics, which was historically important to the development of quantum physics. Similar to vector notation, it is typically denoted by \hat, where the hat indicates that it is an operator. It can also be written as H or \check. Introduction The Hamiltonian of a system represents the total energy of the system; that is, the sum of the kine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Theory
In mathematics, computer science, and network science, network theory is a part of graph theory. It defines networks as Graph (discrete mathematics), graphs where the vertices or edges possess attributes. Network theory analyses these networks over the symmetric relations or directed graph, asymmetric relations between their (discrete) components. Network theory has applications in many disciplines, including statistical physics, particle physics, computer science, electrical engineering, biology, archaeology, linguistics, economics, finance, operations research, climatology, ecology, public health, sociology, psychology, and neuroscience. Applications of network theory include Logistics, logistical networks, the World Wide Web, Internet, gene regulatory networks, metabolic networks, social networks, epistemological networks, etc.; see List of network theory topics for more examples. Euler's solution of the Seven Bridges of Königsberg, Seven Bridges of Königsberg problem is c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percolation Theory
In statistical physics and mathematics, percolation theory describes the behavior of a network when nodes or links are added. This is a geometric type of phase transition, since at a critical fraction of addition the network of small, disconnected clusters merge into significantly larger Glossary of graph theory, connected, so-called spanning clusters. The applications of percolation theory to materials science and in many other disciplines are discussed here and in the articles Network theory and Percolation (cognitive psychology). Introduction A representative question (and the etymology, source of the name) is as follows. Assume that some liquid is poured on top of some porosity, porous material. Will the liquid be able to make its way from hole to hole and reach the bottom? This physical question is mathematical model, modelled mathematically as a Grid graph, three-dimensional network of graph (discrete mathematics), vertices, usually called "sites", in which the graph (dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Model
In mathematics, for example in the study of statistical properties of graphs, a null model is a type of random object that matches one specific object in some of its features, or more generally satisfies a collection of constraints, but which is otherwise taken to be an unbiasedly random structure. The null model is used as a term of comparison, to verify whether the object in question displays some non-trivial features (properties that wouldn't be expected on the basis of chance alone or as a consequence of the constraints), such as community structure in graphs. An appropriate null model behaves in accordance with a reasonable null hypothesis for the behavior of the system under investigation. One null model of utility in the study of complex networks is that proposed by Newman and Girvan, consisting of a randomized version of an original graph G, produced through edges being rewired at random, under the constraint that the expected degree of each vertex matches the degree of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Community Structure
In the study of complex networks, a network is said to have community structure if the nodes of the network can be easily grouped into (potentially overlapping) sets of nodes such that each set of nodes is densely connected internally. In the particular case of ''non-overlapping'' community finding, this implies that the network divides naturally into groups of nodes with dense connections internally and sparser connections between groups. But ''overlapping'' communities are also allowed. The more general definition is based on the principle that pairs of nodes are more likely to be connected if they are both members of the same community(ies), and less likely to be connected if they do not share communities. A related but different problem is community search, where the goal is to find a community that a certain vertex belongs to. Properties In the study of networks, such as computer and information networks, social networks and biological networks, a number of different chara ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leiden Algorithm
The Leiden algorithm is a community detection algorithm developed by Traag ''et al'' at Universiteit Leiden, Leiden University. It was developed as a modification of the Louvain method. Like the Louvain method, the Leiden algorithm attempts to optimize Modularity (networks), modularity in extracting communities from networks; however, it addresses key issues present in the Louvain method, namely poorly connected communities and the Modularity (networks)#Resolution limit, resolution limit of modularity. Improvement over Louvain method Broadly, the Leiden algorithm uses the same two primary phases as the Louvain algorithm: a local node moving step (though, the method by which nodes are considered in Leiden is more efficient) and a graph aggregation step. However, to address the issues with poorly-connected communities and the merging of smaller communities into larger communities (the resolution limit of modularity), the Leiden algorithm employs an intermediate refinement phas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louvain Method
The Louvain method for community detection is a Greedy algorithm, greedy optimization method intended to extract non-overlapping communities from large Graph (discrete mathematics), networks created by Vincent Blondel, Blondel ''et al''. from the Université catholique de Louvain, University of Louvain (the source of this method's name). Modularity optimization The inspiration for this method of Community structure, community detection is the optimization of Modularity (networks), modularity as the algorithm progresses. Modularity is a scale value between −1 (non-modular clustering) and 1 (fully modular clustering) that measures the relative density of edges inside communities with respect to edges outside communities. Optimizing this value theoretically results in the best possible grouping of the nodes of a given network. But because going through all possible configurations of the nodes into groups is impractical, heuristic algorithms are used. In the Louvain Method of comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-loop
In graph theory, a loop (also called a self-loop or a ''buckle'') is an edge that connects a vertex to itself. A simple graph contains no loops. Depending on the context, a graph or a multigraph may be defined so as to either allow or disallow the presence of loops (often in concert with allowing or disallowing multiple edges between the same vertices): * Where graphs are defined so as to ''allow'' loops and multiple edges, a graph without loops or multiple edges is often distinguished from other graphs by calling it a ''simple graph''. * Where graphs are defined so as to ''disallow'' loops and multiple edges, a graph that does have loops or multiple edges is often distinguished from the graphs that satisfy these constraints by calling it a ''multigraph'' or ''pseudograph''. In a graph with one vertex, all edges must be loops. Such a graph is called a bouquet. Degree For an undirected graph, the degree of a vertex is equal to the number of adjacent vertices. A special case ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simulated Annealing
Simulated annealing (SA) is a probabilistic technique for approximating the global optimum of a given function. Specifically, it is a metaheuristic to approximate global optimization in a large search space for an optimization problem. For large numbers of local optima, SA can find the global optimum. It is often used when the search space is discrete (for example the traveling salesman problem, the boolean satisfiability problem, protein structure prediction, and job-shop scheduling). For problems where finding an approximate global optimum is more important than finding a precise local optimum in a fixed amount of time, simulated annealing may be preferable to exact algorithms such as gradient descent or branch and bound. The name of the algorithm comes from annealing in metallurgy, a technique involving heating and controlled cooling of a material to alter its physical properties. Both are attributes of the material that depend on their thermodynamic free energy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spin Glass
In condensed matter physics, a spin glass is a magnetic state characterized by randomness, besides cooperative behavior in freezing of spins at a temperature called the "freezing temperature," ''T''f. In ferromagnetic solids, component atoms' magnetic spins all align in the same direction. Spin glass when contrasted with a ferromagnet is defined as " disordered" magnetic state in which spins are aligned randomly or without a regular pattern and the couplings too are random. A spin glass should not be confused with a " spin-on glass". The latter is a thin film, usually based on SiO2, which is applied via spin coating. The term "glass" comes from an analogy between the ''magnetic'' disorder in a spin glass and the ''positional'' disorder of a conventional, chemical glass, e.g., a window glass. In window glass or any amorphous solid the atomic bond structure is highly irregular; in contrast, a crystal has a uniform pattern of atomic bonds. In ferromagnetic solids, magnetic sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Partitioned Network
Partition may refer to: Arts and entertainment Film and television * ''Partition'' (1987 film), directed by Ken McMullen * ''Partition'' (2007 film), directed by Vic Sarin * '' Partition: 1947'', or ''Viceroy's House'', a 2017 film Music * Partition (music), a segment created from a set * "Partition" (song), by Beyoncé, 2014 * ''Partition'', soundtrack to the 2007 film by Brian Tyler Law and politics * Partition (law), the division of an estate * Partition (politics), a change of political borders, including: ** Partition of India ** Partition of Ireland ** Partitions of Poland Science and technology Computing * Disk partitioning, the division of a hard disk drive * Memory partition, a memory management technique * Partition (database), the division of a logical database * Logical partition, a subset of a computer's resources, virtualized as a separate computer * Binary space partitioning, in computer science * Partition problem, in number theory and computer science Math ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
