Higher rank sheaves on threefolds and functional equations
    
    
  
  
  
      
      
      
        
Épijournal de Géométrie Algébrique, Tome 3 (2019)
    
  
  
  
  
  
    
      
      
        
      
      
      
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              We consider the moduli space of stable torsion free sheaves of any rank on a smooth projective threefold. The singularity set of a torsion free sheaf is the locus where the sheaf is not locally free. On a threefold it has dimension $\leq 1$. We consider the open subset of moduli space consisting of sheaves with empty or 0-dimensional singularity set. For fixed Chern classes $c_1,c_2$ and summing over $c_3$, we show that the generating function of topological Euler characteristics of these open subsets equals a power of the MacMahon function times a Laurent polynomial. This Laurent polynomial is invariant under $q \leftrightarrow q^{-1}$ (upon replacing $c_1 \leftrightarrow -c_1$). For some choices of $c_1,c_2$ these open subsets equal the entire moduli space. The proof involves wall-crossing from Quot schemes of a higher rank reflexive sheaf to a sublocus of the space of Pandharipande-Thomas pairs. We interpret this sublocus in terms of the singularities of the reflexive sheaf.
            
            
            
          
        
      @article{10_46298_epiga_2019_volume3_4375,
     author = {Gholampour, Amin and Kool, Martijn},
     title = {Higher rank sheaves on threefolds and functional equations},
     journal = {\'Epijournal de G\'eom\'etrie Alg\'ebrique},
     publisher = {mathdoc},
     volume = {3},
     year = {2019},
     doi = {10.46298/epiga.2019.volume3.4375},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.46298/epiga.2019.volume3.4375/}
}
                      
                      
                    TY - JOUR AU - Gholampour, Amin AU - Kool, Martijn TI - Higher rank sheaves on threefolds and functional equations JO - Épijournal de Géométrie Algébrique PY - 2019 VL - 3 PB - mathdoc UR - http://geodesic.mathdoc.fr/articles/10.46298/epiga.2019.volume3.4375/ DO - 10.46298/epiga.2019.volume3.4375 LA - en ID - 10_46298_epiga_2019_volume3_4375 ER -
%0 Journal Article %A Gholampour, Amin %A Kool, Martijn %T Higher rank sheaves on threefolds and functional equations %J Épijournal de Géométrie Algébrique %D 2019 %V 3 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.46298/epiga.2019.volume3.4375/ %R 10.46298/epiga.2019.volume3.4375 %G en %F 10_46298_epiga_2019_volume3_4375
Gholampour, Amin; Kool, Martijn. Higher rank sheaves on threefolds and functional equations. Épijournal de Géométrie Algébrique, Tome 3 (2019). doi: 10.46298/epiga.2019.volume3.4375
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