Local invariant cycle theorem

In mathematics, the local invariant cycle theorem was originally a conjecture of Griffiths^{[1] [2]} which states that, given a surjective proper map ${\displaystyle p}${\displaystyle p} from a Kähler manifold ${\displaystyle X}${\displaystyle X} to the unit disk that has maximal rank everywhere except over 0, each cohomology class on ${\displaystyle p^{-1}(t),t\neq 0}${\displaystyle p^{-1}(t),t\neq 0} is the restriction of some cohomology class on the entire ${\displaystyle X}${\displaystyle X} if the cohomology class is invariant under a circle action (monodromy action); in short,

${\displaystyle \operatorname {H} ^{*}(X)\to \operatorname {H} ^{*}(p^{-1}(t))^{S^{1}}}${\displaystyle \operatorname {H} ^{*}(X)\to \operatorname {H} ^{*}(p^{-1}(t))^{S^{1}}}

is surjective. The conjecture was first proved by Clemens. The theorem is also a consequence of the BBD decomposition.^[3]

Deligne also proved the following.^{[4] [5]} Given a proper morphism ${\displaystyle X\to S}${\displaystyle X\to S} over the spectrum ${\displaystyle S}${\displaystyle S} of the henselization of ${\displaystyle k[T]}${\displaystyle k[T]}, ${\displaystyle k}${\displaystyle k} an algebraically closed field, if ${\displaystyle X}${\displaystyle X} is essentially smooth over ${\displaystyle k}${\displaystyle k} and ${\displaystyle X_{\overline {\eta }}}${\displaystyle X_{\overline {\eta }}} smooth over ${\displaystyle {\overline {\eta }}}${\displaystyle {\overline {\eta }}}, then the homomorphism on ${\displaystyle \mathbb {Q} }${\displaystyle \mathbb {Q} }-cohomology:

${\displaystyle \operatorname {H} ^{*}(X_{s})\to \operatorname {H} ^{*}(X_{\overline {\eta }})^{\operatorname {Gal} ({\overline {\eta }}/\eta )}}${\displaystyle \operatorname {H} ^{*}(X_{s})\to \operatorname {H} ^{*}(X_{\overline {\eta }})^{\operatorname {Gal} ({\overline {\eta }}/\eta )}}

is surjective, where ${\displaystyle s,\eta }${\displaystyle s,\eta } are the special and generic points and the homomorphism is the composition ${\displaystyle \operatorname {H} ^{*}(X_{s})\simeq \operatorname {H} ^{*}(X)\to \operatorname {H} ^{*}(X_{\eta })\to \operatorname {H} ^{*}(X_{\overline {\eta }}).}${\displaystyle \operatorname {H} ^{*}(X_{s})\simeq \operatorname {H} ^{*}(X)\to \operatorname {H} ^{*}(X_{\eta })\to \operatorname {H} ^{*}(X_{\overline {\eta }}).}

• Hodge theory

• Beilinson, Alexander A.; Bernstein, Joseph; Deligne, Pierre (1982). "Faisceaux pervers". Astérisque (in French). 100. Paris: Société Mathématique de France. MR 0751966.
• Clemens, C. H. (1977). "Degeneration of Kähler manifolds". Duke Mathematical Journal. 44 (2). doi:10.1215/S0012-7094-77-04410-6. S2CID 120378293.
• Deligne, Pierre (1980). "La conjecture de Weil : II" (PDF). Publications Mathématiques de l'IHÉS. 52: 137–252. doi:10.1007/BF02684780. MR 0601520. S2CID 189769469. Zbl 0456.14014.
• Griffiths, Phillip A. (1970). "Periods of integrals on algebraic manifolds: Summary of main results and discussion of open problems". Bulletin of the American Mathematical Society. 76 (2): 228–296. doi:10.1090/S0002-9904-1970-12444-2 .
• Morrison, David R. The Clemens-Schmid exact sequence and applications, Topics in transcendental algebraic geometry (Princeton, N.J., 1981/1982), 101-119, Ann. of Math. Stud., 106, Princeton Univ. Press, Princeton, NJ, 1984. [1]

• Algebraic geometry stubs
• Theorems in algebraic geometry

• Articles with short description
• Short description matches Wikidata
• CS1 French-language sources (fr)
• All stub articles