invariant field
21Casson invariant — In 3 dimensional topology, a part of the mathematical field of geometric topology, the Casson invariant is an integer valued invariant of oriented integral homology 3 spheres, introduced by Andrew Casson.Kevin Walker (1992) found an extension to… …
22Modular invariant of a group — In mathematics, a modular invariant of a group is an invariant of a finite group acting on a vector space of positive characteristic (usually dividing the order of the group). The study of modular invariants was originated in about 1914 by… …
23Lagrange invariant — In optics the Lagrange invariant is a measure of the light propagating through an optical system. It is defined by , where y and u are the marginal ray height and angle respectively, and ȳ and ū are the chief ray height and angle. n is the… …
24Vector field — In mathematics a vector field is a construction in vector calculus which associates a vector to every point in a (locally) Euclidean space.Vector fields are often used in physics to model, for example, the speed and direction of a moving fluid… …
25Yamabe invariant — In mathematics, in the field of differential geometry, the Yamabe invariant (also referred to as the sigma constant) is a real number invariant associated to a smooth manifold that is preserved under diffeomorphisms. It was first written down… …
26Electric displacement field — In physics, the electric displacement field, denoted as , is a vector field that appears in Maxwell s equations. It accounts for the effects of free charges within materials. D stands for displacement, as in the related concept of displacement… …
27Arf invariant (knot) — In the mathematical field of knot theory, the Arf invariant of a knot, named after Cahit Arf, is a knot invariant obtained from a quadratic form associated to a Seifert surface. If F is a Seifert surface of a knot, then the homology group H1( F …
28Mason's Invariant — Introduction When trying to solve a seemingly difficult problem, Sam said to concentrate on the easier ones first; the rest, including the hardest ones, will follow, recalled Andrew Viterbi, co founder and former vice president of Qualcomm. He… …
29Arf invariant — In mathematics, the Arf invariant, named after Turkish mathematician Cahit Arf, who introduced it in 1941, is an element of F2 associated to a non singular quadratic form over the field F2 with 2 elements, equal to the most common value of the… …
30Knot invariant — In the mathematical field of knot theory, a knot invariant is a quantity (in a broad sense) defined for each knot which is the same for equivalent knots. The equivalence is often given by ambient isotopy but can be given by homeomorphism. Some… …
