|
|
| Line 1: |
Line 1: |
| {{for|duality over number fields|Artin–Verdier duality}}
| | Andrew Simcox is the name his parents gave him and he totally enjoys this title. The favorite hobby for him and his kids is to perform lacross and he would never give it up. My day occupation is a journey agent. For a whilst I've been in Mississippi but now I'm contemplating other options.<br><br>Feel free to surf to my web site - [http://www.prograd.uff.br/novo/facts-about-growing-greater-organic-garden authentic psychic readings] |
| In mathematics, '''Verdier duality''' is a duality in [[sheaf theory]] that generalizes [[Poincaré duality]] for [[manifold]]s. Verdier duality was introduced by {{harvs|txt|authorlink=Jean-Louis Verdier|last=Verdier|year1=1967|year2=1995}} as an analog for locally compact spaces of the [[coherent duality]] for schemes due to [[Grothendieck]]. It is commonly encountered when studying constructible or [[perverse sheaves]].
| |
| | |
| ==Verdier duality==
| |
| Verdier duality states that certain [[image functors for sheaves]] are actually [[adjoint functors]]. There are two versions.
| |
| | |
| '''Global Verdier duality''' states that the higher direct image functor with compact supports ''Rf''<sub>!</sub> has a right adjoint ''f''<sup>!</sup> in the derived category of sheaves, in other words
| |
| :<math>[Rf_!\mathcal{F},\mathcal{G}] \cong [\mathcal{F},f^!\mathcal{G}] . \,\!</math>
| |
| The exclamation mark is often pronounced "shriek" (slang for exclamation mark), and the maps called "''f'' shriek" or "''f'' lower shriek" and "''f'' upper shriek" – see also [[shriek map]]. | |
| | |
| '''Local Verdier duality''' states that
| |
| :<math>R\,\mathcal{H}om(Rf_!\mathcal{F},\mathcal{G}) \cong Rf_{\ast}R\,\mathcal{H}om(\mathcal{F},f^!\mathcal{G})</math>
| |
| in the [[derived category]] of sheaves of ''k'' modules over ''X''.
| |
| It is important to note that the distinction between the global and local versions is that the former relates maps between sheaves, whereas the latter relates sheaves directly and so can be evaluated locally. Taking global sections of both sides in the local statement gives global Verdier duality.
| |
| | |
| The '''dualizing complex''' ''D<sub>X</sub>'' on ''X'' is defined to be
| |
| :<math>\omega_X = p^!(k) , \,\!</math>
| |
| where ''p'' is the map from ''X'' to a point. Part of what makes Verdier duality interesting in the singular setting is that when ''X'' is not a manifold (a graph or singular algebraic variety for example) then the dualizing complex is not quasi-isomorphic to a sheaf concentrated in a single degree. From this perspective the derived category is necessary in the study of singular spaces.
| |
| | |
| If ''X'' is a finite dimensional locally compact space, and ''D''<sup>''b''</sup>(''X'') the bounded [[derived category]] of sheaves of abelian groups over ''X'', then the '''Verdier dual''' is a [[contravariant functor]]
| |
| | |
| :<math>D \colon D^b(X)\to D^b(X) \,\!</math>
| |
| | |
| defined by
| |
| | |
| :<math>D(\mathcal{F}) = R\,\mathcal{H}om(\mathcal{F}, \omega_X) . \,\!</math>
| |
| | |
| It has the following properties:
| |
| | |
| {{unordered list
| |
| |1= <math> D^2(\mathcal{F})\cong \mathcal{F}</math> for sheaves with constructible cohomology.
| |
| |2= (Intertwining of functors ''f''<sub>*</sub> and ''f''<sub>!</sub>) If ''f'' is a continuous map from ''X'' to ''Y'' then there is an isomorphism
| |
| :<math>D(Rf_{\ast}(\mathcal{F})) \cong Rf_!D(\mathcal{F})</math>.
| |
| }}
| |
| | |
| ==Poincaré duality==
| |
| [[Poincaré duality]] can be derived as a special case of Verdier duality. Here one explicitly calculates cohomology of a space using the machinery of [[sheaf cohomology]].
| |
| | |
| Suppose ''X'' is a compact ''n''-dimensional manifold, ''k'' is a field and ''k''<sub>X</sub> is the locally constant sheaf on ''X'' with coefficients in ''k''. Let ''f=p'' be the constant map. Global Verdier duality then states
| |
| :<math>[Rp_!k_X,k] \cong [k_X,p^!k] . \,\!</math>
| |
| To understand how Poincaré duality is obtained from this statement, it is perhaps easiest to understand both sides piece by piece. Let
| |
| :<math>k_X\to I^{\bullet}_X = I^0_X \to I^1_X \to \cdots </math>
| |
| be an injective resolution of the constant sheaf. Then by standard facts on right derived functors
| |
| :<math>Rp_!k_X=p_!I^{\bullet}_X=\Gamma_c(X;I^{\bullet}_X)</math>
| |
| is a complex whose cohomology is the compactly supported cohomology of ''X''. Since morphisms between complexes of sheaves (or vector spaces) themselves form a complex we find that
| |
| :<math>\mathrm{Hom}^{\bullet}(\Gamma_c(X;I^{\bullet}_X),k)= \cdots \to \Gamma_c(X;I^2_X)^{\vee}\to \Gamma_c(X;I^1_X)^{\vee}\to \Gamma_c(X;I^0_X)^{\vee}\to 0</math>
| |
| where the last non-zero term is in degree 0 and the ones to the left are in negative degree. Morphisms in the derived category are obtained from the [[homotopy category of chain complexes]] of sheaves by taking the zeroth cohomology of the complex, i.e.
| |
| :<math>[Rp_!k_X,k]\cong H^0(\mathrm{Hom}^{\bullet}(\Gamma_c(X;I^{\bullet}_X),k))=H^0_c(X;k_X)^{\vee}.</math>
| |
| | |
| For the other side of the Verdier duality statement above, we have to take for granted the fact that when ''X'' is a compact ''n''-dimensional manifold
| |
| :<math>p^!k=k_X[n],</math>
| |
| which is the dualizing complex for a manifold. Now we can re-express the right hand side as
| |
| :<math>[k_X,k_X[n]]\cong H^n(\mathrm{Hom}^{\bullet}(k_X,k_X))=H^n(X;k_X).</math>
| |
| We finally have obtained the statement that
| |
| :<math>H^0_c(X;k_X)^{\vee}\cong H^n(X;k_X).</math>
| |
| By repeating this argument with the sheaf ''k''<sub>X</sub> replaced with the same sheaf placed in degree ''i'' we get the classical Poincaré duality
| |
| :<math>H^i_c(X;k_X)^{\vee}\cong H^{n-i}(X;k_X).</math>
| |
| | |
| ==See also==
| |
| *[[Six operators]]
| |
| | |
| ==References==
| |
| <references />
| |
| * {{Citation | last1=Borel | first1=Armand | author1-link=Armand Borel | title=Intersection cohomology | publisher=Birkhäuser | location=Basel, Boston, Berlin | series=Progress in Mathematics | isbn=978-0-8176-3274-8 | year=1984}}
| |
| * {{Citation | last1=Gelfand | first1=Sergei I. | last2=Manin | first2=Yuri Ivanovich | author2-link=Yuri Ivanovich Manin | title=Homological algebra | isbn=978-3-540-65378-3 | year=1999 | publisher=Springer | location=Berlin}}
| |
| * {{Citation | last1=Grothendieck | first1=Alexandre | author1-link=Alexandre Grothendieck | title=Séminaire de Géométrie Algébrique du Bois Marie - 1965-66 - Cohomologie l-adique et Fonctions L - (SGA 5) | publisher=[[Springer-Verlag]] | location=Berlin, New York | series=Lecture notes in mathematics | isbn=978-3-540-08248-4 | year=1977 | volume=589 | pages=xii+484}}, Exposés I and II contain the corresponding theory in the étale situation
| |
| * {{Citation | last1=Iversen | first1=Birger | title=Cohomology of sheaves | publisher=[[Springer-Verlag]] | location=Berlin, New York | series=Universitext | isbn=978-3-540-16389-3 | id={{MathSciNet | id = 842190}} | year=1986}}
| |
| * {{Citation | last1=Kashiwara | first1=Masaki | last2=Schapira | first2=Pierre | author1-link=Masaki Kashiwara | title=Sheaves on Manifolds | isbn=3540518614 | year=2002 | publisher=Springer | location=Berlin}}
| |
| *{{Citation | last1=Verdier | first1=Jean-Louis | author1-link=Jean-Louis Verdier | editor-last=Springer | editor1-first=Tonny Albert | title=Proceedings of a Conference on Local Fields: NUFFIC Summer School held at Driebergen (The Netherlands) in 1966 | url=http://books.google.com/books?id=SW-mAAAAIAAJ | publisher=[[Springer-Verlag]] | location=Berlin, New York | isbn=978-3-540-03953-2 | id={{MR|0230732}} | year=1967 | chapter=A duality theorem in the etale cohomology of schemes | pages=184–198}}
| |
| *{{Citation | last1=Verdier | first1=Jean-Louis | author1-link=Jean-Louis Verdier | title=Séminaire Bourbaki, Vol. 9 | url=http://www.numdam.org/item?id=SB_1964-1966__9__337_0 | publisher=[[Société Mathématique de France]] | location=Paris | isbn=978-2-85629-042-2 | id={{MR|1610971}} | year=1995 | chapter=Dualité dans la cohomologie des espaces localement compacts | pages=Exp. No. 300, 337–349}}
| |
| | |
| {{DEFAULTSORT:Verdier Duality}}
| |
| [[Category:Topology]]
| |
| [[Category:Homological algebra]]
| |
| [[Category:Sheaf theory]]
| |
| [[Category:Duality theories]]
| |
Andrew Simcox is the name his parents gave him and he totally enjoys this title. The favorite hobby for him and his kids is to perform lacross and he would never give it up. My day occupation is a journey agent. For a whilst I've been in Mississippi but now I'm contemplating other options.
Feel free to surf to my web site - authentic psychic readings