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相交系和Snevily猜想 Introduction Intersectiontheoryisabranchoftopologythatstudiesthepropertiesofintersectionsofsubspacesormanifoldsinatopologicalspace.Theintersectiontheoryisapowerfultoolforstudyingalgebraicanddifferentialgeometry,amongotherfields.Oneofthefundamentalproblemsinintersectiontheoryistodeterminethenumberofpointsofintersectionbetweentwosubspacesormanifolds. Inthispaper,wewillfocusontheintersectiontheoryofalgebraicvarieties,whicharethezerosetsofpolynomialequationsinseveralvariables.Wewilldiscusstheconceptofacompleteintersection,whichisaspecialtypeofalgebraicvarietythathasacertainnumberofpointsofintersectionwithothervarieties.WewillalsoconsidertheSnevilyconjecture,whichisaconjectureinintersectiontheorythatrelatesthenumberofpointsofintersectiononacompleteintersectionwiththenumberofpointsontheambientspace. CompleteIntersection Acompleteintersectionisaprojectivevarietythatcanbedefinedastheintersectionofacertainnumberofhypersurfacesinprojectivespace.Inotherwords,acompleteintersectionisthezerosetofasystemofpolynomialequationsofdegreed,wherethenumberofequationsisequaltothedimensionoftheambientspace.Forexample,acompleteintersectionoftwoquadricsinprojectivethree-spaceisasurfacethatistheintersectionoftwoquadraticsurfaces. Thefundamentaltheoremofintersectiontheorystatesthatthenumberofpointsofintersectionbetweenacompleteintersectionandanotheralgebraicvarietyinprojectivespaceisequaltotheproductofthedegreesofthevarieties.Inotherwords,ifXandYaretwoprojectivevarietiesofdegreesdande,respectively,andifXandYintersecttransversely,thenthenumberofpointsofintersectionbetweenXandYisgivenbydtimese. SnevilyConjecture TheSnevilyconjectureisaconjectureinintersectiontheorythatrelatesthenumberofpointsofintersectiononacompleteintersectionwiththenumberofpointsontheambientspace.Moreprecisely,theconjecturestatesthatgivenacompleteintersectionofdegreedinprojectiven-space,thenumberofintersectionpointswithanothervarietyofdegreeeisequaltothesumoftheintersectionpointsoftheambientspaceofdegreed+e-n. Th