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2 Beilinson Monads and $\mathrm{Coh}(\mathbb{P}^m)$
 2.1 Operations

2 Beilinson Monads and $\mathrm{Coh}(\mathbb{P}^m)$

2.1 Operations

2.1-1 TwistedOmegaModule
‣ TwistedOmegaModule( A, i )( operation )

Returns: graded lp

The input is a graded exterior algebra A and an integer i. The output is the graded A-lp \omega_A(i).

2.1-2 TwistedGradedFreeModule
‣ TwistedGradedFreeModule( S, i )( operation )

Returns: graded lp

The input is a graded polynomial ring S and an integer i. The output is the graded S-lp S(i). The sheafification of S(i) is the structure sheaf \mathcal{O}_{\mathbb{P}^m}(i).

2.1-3 TwistedCotangentModule
‣ TwistedCotangentModule( S, i )( operation )

Returns: graded lp

The input is a graded polynomial ring S and an integer i. The output is the graded S-lp \Omega^i(i). The sheafification of \Omega^i(i) is the twisted cotangent sheaf \Omega^i_{\mathbb{P}^m}(i).

2.1-4 TwistedCotangentModuleAsChain
‣ TwistedCotangentModuleAsChain( S, i )( operation )

Returns: chain complex

The input is a graded polynomial ring S and an integer i. The output is the chain complex of S-lp's whose objects are direct sums of twists of S and its homology at 0 is \Omega^i(i). I.e., a chain complex that is quasi-isomorphic to \Omega^i(i).

2.1-5 TwistedCotangentModuleAsCochain
‣ TwistedCotangentModuleAsCochain( S, i )( operation )

Returns: cochain complex

The input is a graded polynomial ring S and an integer i. The output is the chain complex of S-lp's whose objects are direct sums of twists of S and its homology at 0 is \Omega^i(i). I.e., a chain complex that is quasi-isomorphic to \Omega^i(i).

2.1-6 BasisBetweenTwistedOmegaModules
‣ BasisBetweenTwistedOmegaModules( A, i, j )( operation )

Returns: a list

The input is a graded exterior ring A := KoszulDualRing(S) with S:=k[x_0,\dots,x_m] and two integers i,j with i\geq j. The output is a basis of the external hom: \mathrm{Hom}_A(\omega_A(i), \omega_A(j)). If we denote the indeterminates of A by e_0,\dots, e_m and the \ell'th entry of the output by \sigma_{ij}^{\ell} then we have \sigma_{i+1,i}^{\ell}=e_{\ell-1}, thus \sigma_{i+1,i}^{\ell_1} \sigma_{i,i-1}^{\ell_2}= -\sigma_{i+1,i}^{\ell_2} \sigma_{i,i-1}^{\ell_1}.

2.1-7 BasisBetweenTwistedGradedFreeModules
‣ BasisBetweenTwistedGradedFreeModules( S, i, j )( operation )

Returns: a list

The input is a graded polynomial ring S=k[x_0, \dots, x_m] and two integers i,j with i\leq j. The output is a basis of the external hom: \mathrm{Hom}_S(S(i), S(j)). If we denote the \ell'th entry of the output by \psi_{ij}^{\ell} then we have \psi_{i-1,i}^{\ell}=x_{\ell-1}, thus \psi_{i-1,i}^{\ell_1} \psi_{i,i+1}^{\ell_2}= \psi_{i-1,i}^{\ell_2} \psi_{i,i+1}^{\ell_1}.

2.1-8 BasisBetweenTwistedCotangentModulesAsGLP
‣ BasisBetweenTwistedCotangentModulesAsGLP( S, i, j )( operation )

Returns: a list

The input is a graded polynomial ring S=k[x_0, \dots, x_m] and two integers 0\leq j \leq i \leq m. The output is a basis of the external hom: \mathrm{Hom}_S(\Omega^i(i), \Omega^i(j)). If we denote the \ell'th entry of the output by \varphi_{ij}^{\ell} then we have \varphi_{i+1,i}^{\ell} \varphi_{i,i-1}^{\ell}=0 and \varphi_{i+1,i}^{\ell_1} \varphi_{i,i-1}^{\ell_2}= -\varphi_{i+1,i}^{\ell_2} \varphi_{i,i-1}^{\ell_1}.

2.1-9 BeilinsonReplacement
‣ BeilinsonReplacement( M )( attribute )

Returns: a chain or cochain complex

The input is graded S-lp, graded A-lp, chain complex or cochain complex of S-lp's. The output is a Beilinson monad of M.

2.1-10 BeilinsonReplacement
‣ BeilinsonReplacement( phi )( attribute )

Returns: a chain or cochain complex

The input is graded S-lp morphism, graded A-lp morphism, chain morphism or cochain morphism of S-lp's. The output is a Beilinson monad morphism of \phi.

2.1-11 MorphismFromGLPToZerothObjectOfBeilinsonReplacement
‣ MorphismFromGLPToZerothObjectOfBeilinsonReplacement( M )( attribute )

Returns: a morphism

The input is graded S-lp M. The output is a morphism from the sheafification of M to the sheafification of the 0'th object of its Beilinson replacement. This morphism induces a quasi-isomorphism from sheafification of M considered as a chain complex concentrated in degree 0 to the sheafification of the Beilinson replacement of M.

2.1-12 MorphismFromGLPToZerothHomologyOfBeilinsonReplacement
‣ MorphismFromGLPToZerothHomologyOfBeilinsonReplacement( M )( attribute )

Returns: a morphism

The input is graded S-lp M. The output is an isomorphism from the Sheafification of M to the sheafification of the 0'th homology of its Beilinson replacement.

2.1-13 MorphismFromZerothObjectOfBeilinsonReplacementToGLP
‣ MorphismFromZerothObjectOfBeilinsonReplacementToGLP( M )( attribute )

Returns: a morphism

The input is graded S-lp M. The output is a morphism from the sheafification of the 0'th object of the Beilinson replacement of M to the sheafification of M. This morphism induces a quasi-isomorphism from the sheafification of the Beilinson replacement of M to sheafification of M considered as a chain complex concentrated in degree 0.

2.1-14 MorphismFromZerothHomologyOfBeilinsonReplacementToGLP
‣ MorphismFromZerothHomologyOfBeilinsonReplacementToGLP( M )( attribute )

Returns: a morphism

The input is graded S-lp M. The output is an isomorphism from the the sheafification of the 0'th homology of its Beilinson replacement to Sheafification of M.

2.1-15 ShowMatrix
‣ ShowMatrix( M )( function )

Returns: nothing

The inpute is a homalg matrix or anything that has attribute UnderlyingMatrix. It views the entries using the browse package. To quit: q+y.

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