Dear all,
I was trying to specify the number of eigenvalues calculated by sparsediag, using
NUMBER_EIGENVALUES=1
as described here: http://alps.comp-phys.org/mediawiki/index.php/Documentation:sparsediag
However, sparsediag nevertheless calculates the lowest eigenvalue for each wavevector. Does this option no longer work? The problem persists even for a simple test case:
LATTICE="chain lattice" MODEL="spin"
local_S=0.5 Jxy=0.0 Jz="-1.0" Gamma=0.5
NUMBER_EIGENVALUES=1
MEASURE_CORRELATIONS[Diagonal spin correlations]=Sz MEASURE_CORRELATIONS[Offdiagonal spin correlations]="Splus:Sminus"
{L=20;}
A second question pertains to the output of sparsediag. With the above input file, the results contain the line
<PARAMETER name="TOTAL_MOMENTUM">5.7595865315812870833</PARAMETER>
However, I have not specified TOTAL_MOMENTUM...
Any help is appreciated.
Best regards,
Martin Hohenadler
On Dec 4, 2010, at 8:46 AM, Martin Hohenadler wrote:
Dear all,
I was trying to specify the number of eigenvalues calculated by sparsediag, using
NUMBER_EIGENVALUES=1
as described here: http://alps.comp-phys.org/mediawiki/index.php/Documentation:sparsediag
However, sparsediag nevertheless calculates the lowest eigenvalue for each wavevector.
NUMBER_EIGENVALUES specifies the number of eigenvalues that should be calculated in each symmetry sector. If you don't want that then you can set the value of TOTAL_MOMENTUM to restrict the calculation to one momentum sector.
A second question pertains to the output of sparsediag. With the above input file, the results contain the line
<PARAMETER name="TOTAL_MOMENTUM">5.7595865315812870833</PARAMETER>
This is because it uses translational symmetry and diagonalizes the Hamiltonian in each symmetry sector, looping over all values of TOTAL_MOMENTUM.
Matthias
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