|
List Of Things Named After Ernst Witt
{{Short description, none These are things named after Ernst Witt, a German mathematician. * Bourbaki–Witt theorem * Hall–Witt identity * Hasse–Witt matrix **Hasse–Witt invariant * Poincaré–Birkhoff–Witt theorem, usually known as the PBW theorem * Shirshov–Witt theorem * Witt algebra * Witt decomposition * Witt design (Witt geometry) * Witt group * Witt index * Witt polynomial * Witt ring ** Grothendieck-Witt ring * Witt scheme * Witt's theorem * Witt vector **Witt vector cohomology In mathematics, Witt vector cohomology was an early ''p''-adic cohomology theory for algebraic varieties introduced by . Serre constructed it by defining a sheaf of truncated Witt rings ''W'n'' over a variety ''V'' and then taking the inverse l ... Witt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ernst Witt
Ernst Witt (26 June 1911 – 3 July 1991) was a German mathematician, one of the leading algebraists of his time. Biography Witt was born on the island of Alsen, then a part of the German Empire. Shortly after his birth, his parents moved the family to China to work as missionaries, and he did not return to Europe until he was nine. After his schooling, Witt went to the University of Freiburg and the University of Göttingen. He joined the NSDAP (Nazi Party) and was an active party member. Witt was awarded a Ph.D. at the University of Göttingen in 1934 with a thesis titled: "Riemann-Roch theorem and zeta-Function in hypercomplexes" (Riemann-Rochscher Satz und Zeta-Funktion im Hyperkomplexen) that was supervised by Gustav Herglotz with Emmy Noether suggesting the top for the doctorate. He qualified to become a lecturer and gave guest lectures in Göttingen and Hamburg. He became associated with the team led by Helmut Hasse who led his habilitation. In June 1936 gave his habil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Design
250px, thumbnail, The Fano plane is a Steiner triple system S(2,3,7). The blocks are the 7 lines, each containing 3 points. Every pair of points belongs to a unique line. In combinatorial mathematics, a Steiner system (named after Jakob Steiner) is a type of block design, specifically a t-design with λ = 1 and ''t'' = 2 or (recently) ''t'' ≥ 2. A Steiner system with parameters ''t'', ''k'', ''n'', written S(''t'',''k'',''n''), is an ''n''-element set ''S'' together with a set of ''k''-element subsets of ''S'' (called blocks) with the property that each ''t''-element subset of ''S'' is contained in exactly one block. In an alternate notation for block designs, an S(''t'',''k'',''n'') would be a ''t''-(''n'',''k'',1) design. This definition is relatively new. The classical definition of Steiner systems also required that ''k'' = ''t'' + 1. An S(2,3,''n'') was (and still is) called a ''Steiner triple'' (or ''triad'') ''system'', while an S(3,4,''n'') is called a ''Steiner quadr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Scheme
In mathematics, a Witt vector is an infinite sequence of elements of a commutative ring. Ernst Witt showed how to put a ring structure on the set of Witt vectors, in such a way that the ring of Witt vectors W(\mathbb_p) over the finite field of order p is the ring of p-adic integers. They have a highly non-intuitive structure upon first glance because their additive and multiplicative structure depends on an infinite set of recursive formulas which do not behave like addition and multiplication formulas for standard p-adic integers. The main idea behind Witt vectors is instead of using the standard p-adic expansiona = a_0+a_1p+a_2p^2 + \cdotsto represent an element in \mathbb_p, we can instead consider an expansion using the Teichmüller character\omega: \mathbb_p^* \to \mathbb_p^*which sends each element in the solution set of x^-1 in \mathbb_p to an element in the solution set of x^-1 in \mathbb_p. That is, we expand out elements in \mathbb_p in terms of roots of unity instead of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Group
In mathematics, a Witt group of a field (mathematics), field, named after Ernst Witt, is an abelian group whose elements are represented by symmetric bilinear form, symmetric bilinear forms over the field. Definition Fix a field ''k'' of characteristic (algebra), characteristic not equal to two. All vector spaces will be assumed to be finite-dimension (vector space), dimensional. We say that two spaces equipped with symmetric bilinear forms are equivalent if one can be obtained from the other by adding a metabolic quadratic space, that is, zero or more copies of a hyperbolic plane (quadratic forms), hyperbolic plane, the non-degenerate two-dimensional symmetric bilinear form with a norm 0 vector.Milnor & Husemoller (1973) p. 14 Each class is represented by the core form of a Witt decomposition.Lorenz (2008) p. 30 The Witt group of ''k'' is the abelian group ''W''(''k'') of equivalence classes of non-degenerate symmetric bilinear forms, with the group operation correspo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Vector
In mathematics, a Witt vector is an infinite sequence of elements of a commutative ring. Ernst Witt showed how to put a ring structure on the set of Witt vectors, in such a way that the ring of Witt vectors W(\mathbb_p) over the finite field of order p is the ring of p-adic integers. They have a highly non-intuitive structure upon first glance because their additive and multiplicative structure depends on an infinite set of recursive formulas which do not behave like addition and multiplication formulas for standard p-adic integers. The main idea behind Witt vectors is instead of using the standard p-adic expansiona = a_0+a_1p+a_2p^2 + \cdotsto represent an element in \mathbb_p, we can instead consider an expansion using the Teichmüller character\omega: \mathbb_p^* \to \mathbb_p^*which sends each element in the solution set of x^-1 in \mathbb_p to an element in the solution set of x^-1 in \mathbb_p. That is, we expand out elements in \mathbb_p in terms of roots of unity instead of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Polynomial
In mathematics, a Witt vector is an infinite sequence of elements of a commutative ring. Ernst Witt showed how to put a ring structure on the set of Witt vectors, in such a way that the ring of Witt vectors W(\mathbb_p) over the finite field of order p is the ring of p-adic integers. They have a highly non-intuitive structure upon first glance because their additive and multiplicative structure depends on an infinite set of recursive formulas which do not behave like addition and multiplication formulas for standard p-adic integers. The main idea behind Witt vectors is instead of using the standard p-adic expansiona = a_0+a_1p+a_2p^2 + \cdotsto represent an element in \mathbb_p, we can instead consider an expansion using the Teichmüller character\omega: \mathbb_p^* \to \mathbb_p^*which sends each element in the solution set of x^-1 in \mathbb_p to an element in the solution set of x^-1 in \mathbb_p. That is, we expand out elements in \mathbb_p in terms of roots of unity instead of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Index
:''"Witt's theorem" or "the Witt theorem" may also refer to the Bourbaki–Witt fixed point theorem of order theory.'' In mathematics, Witt's theorem, named after Ernst Witt, is a basic result in the algebraic theory of quadratic forms: any isometry between two subspaces of a nonsingular quadratic space over a field ''k'' may be extended to an isometry of the whole space. An analogous statement holds also for skew-symmetric, Hermitian and skew-Hermitian bilinear forms over arbitrary fields. The theorem applies to classification of quadratic forms over ''k'' and in particular allows one to define the Witt group ''W''(''k'') which describes the "stable" theory of quadratic forms over the field ''k''. Statement Let be a finite-dimensional vector space over a field ''k'' of characteristic different from 2 together with a non-degenerate symmetric or skew-symmetric bilinear form. If is an isometry between two subspaces of ''V'' then ''f'' extends to an isometry of ''V''. Witt's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Group
In mathematics, a Witt group of a field (mathematics), field, named after Ernst Witt, is an abelian group whose elements are represented by symmetric bilinear form, symmetric bilinear forms over the field. Definition Fix a field ''k'' of characteristic (algebra), characteristic not equal to two. All vector spaces will be assumed to be finite-dimension (vector space), dimensional. We say that two spaces equipped with symmetric bilinear forms are equivalent if one can be obtained from the other by adding a metabolic quadratic space, that is, zero or more copies of a hyperbolic plane (quadratic forms), hyperbolic plane, the non-degenerate two-dimensional symmetric bilinear form with a norm 0 vector.Milnor & Husemoller (1973) p. 14 Each class is represented by the core form of a Witt decomposition.Lorenz (2008) p. 30 The Witt group of ''k'' is the abelian group ''W''(''k'') of equivalence classes of non-degenerate symmetric bilinear forms, with the group operation correspo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt's Theorem
:''"Witt's theorem" or "the Witt theorem" may also refer to the Bourbaki–Witt fixed point theorem of order theory.'' In mathematics, Witt's theorem, named after Ernst Witt, is a basic result in the algebraic theory of quadratic forms: any isometry between two subspaces of a nonsingular quadratic space over a field ''k'' may be extended to an isometry of the whole space. An analogous statement holds also for skew-symmetric, Hermitian and skew-Hermitian bilinear forms over arbitrary fields. The theorem applies to classification of quadratic forms over ''k'' and in particular allows one to define the Witt group ''W''(''k'') which describes the "stable" theory of quadratic forms over the field ''k''. Statement Let be a finite-dimensional vector space over a field ''k'' of characteristic different from 2 together with a non-degenerate symmetric or skew-symmetric bilinear form. If is an isometry between two subspaces of ''V'' then ''f'' extends to an isometry of ''V''. Witt's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bourbaki–Witt Theorem
In mathematics, the Bourbaki–Witt theorem in order theory, named after Nicolas Bourbaki and Ernst Witt, is a basic fixed point theorem for partially ordered sets. It states that if ''X'' is a non-empty chain complete poset, and f : X \to X such that f (x) \geq x for all x, then ''f'' has a fixed point. Such a function ''f'' is called ''inflationary'' or ''progressive''. Special case of a finite poset If the poset ''X'' is finite then the statement of the theorem has a clear interpretation that leads to the proof. The sequence of successive iterates, : x_=f(x_n), n=0,1,2,\ldots, where ''x''0 is any element of ''X'', is monotone increasing. By the finiteness of ''X'', it stabilizes: : x_n=x_, for ''n'' sufficiently large. It follows that ''x''∞ is a fixed point of ''f''. Proof of the theorem Pick some y \in X. Define a function ''K'' recursively on the ordinals as follows: :\,K(0) = y :\,K( \alpha+1 ) = f( K( \alpha ) ). If \beta is a limit ordinal, then b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Witt Algebra
In mathematics, the complex Witt algebra, named after Ernst Witt, is the Lie algebra of meromorphic vector fields defined on the Riemann sphere that are holomorphic except at two fixed points. It is also the complexification of the Lie algebra of polynomial vector fields on a circle, and the Lie algebra of derivations of the ring C 'z'',''z''−1 There are some related Lie algebras defined over finite fields, that are also called Witt algebras. The complex Witt algebra was first defined by Cartan (1909), and its analogues over finite fields were studied by Witt in the 1930s. Basis A basis for the Witt algebra is given by the vector fields L_n=-z^ \frac, for ''n'' in ''\mathbb Z''. The Lie bracket of two vector fields is given by : _m,L_n(m-n)L_. This algebra has a central extension called the Virasoro algebra that is important in two-dimensional conformal field theory and string theory. Note that by restricting ''n'' to 1,0,-1, one gets a subalgebra. Taken over th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shirshov–Witt Theorem
In mathematics, a free Lie algebra over a field ''K'' is a Lie algebra generated by a set ''X'', without any imposed relations other than the defining relations of alternating ''K''-bilinearity and the Jacobi identity. Definition The definition of the free Lie algebra generated by a set ''X'' is as follows: : Let ''X'' be a set and i\colon X \to L a morphism of sets ( function) from ''X'' into a Lie algebra ''L''. The Lie algebra ''L'' is called free on ''X'' if i is the universal morphism; that is, if for any Lie algebra ''A'' with a morphism of sets f\colon X \to A, there is a unique Lie algebra morphism g\colon L\to A such that f = g \circ i. Given a set ''X'', one can show that there exists a unique free Lie algebra L(X) generated by ''X''. In the language of category theory, the functor sending a set ''X'' to the Lie algebra generated by ''X'' is the free functor from the category of sets to the category of Lie algebras. That is, it is left adjoint to the forgetful fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |