i1 : X = specialGushelMukaiFourfold("21",ZZ/33331);
o1 : ProjectiveVariety, GM fourfold containing a surface of degree 12 and sectional genus 5
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i2 : describe X
o2 = Special Gushel-Mukai fourfold of discriminant 26(')
containing a surface in PP^8 of degree 12 and sectional genus 5
cut out by 16 hypersurfaces of degree 2
and with class in G(1,4) given by 7*s_(3,1)+5*s_(2,2)
Type: ordinary
(case 21 of Table 1 in arXiv:2002.07026)
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i3 : Y = grassmannianHull X;
o3 : ProjectiveVariety, 5-dimensional subvariety of PP^8
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i4 : isSubset(X,Y)
o4 = true
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i5 : Y!
dim:.................. 5
codim:................ 3
degree:............... 5
sectional genus:...... 1
generators:........... 2^5
linear normality:..... true
connected components:. 1
purity:............... true
dim sing. l.:......... -1
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