[ALPS-users] NUMBER_EIGENVALUES and TOTAL_MOMENTUM (ALPS 2)

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