Dear Zhenya,

Many thanks!! It is not ugly it is beautiful and it works !!

All the best

jakub

Message: 3 Date: Fri, 27 Mar 2009 21:48:00 +0100 From: Evgeny Burovskiy burovski@alumni.umass.edu Subject: Re: [ALPS-users] working on alps code To: comp-phys-alps-users@phys.ethz.ch Message-ID: 49CD3B80.9080803@physik.uni-greifswald.de Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Dear Jakub,

...

So I guess from examples .. but I cannot guess everything. To be specific. I run QMC codes for Bose-Hubbard. I know how to get occupation at different sides (for inhomogenous model, e.g. with harmonic trap and/or disorder), call them <n_i>. But I am interested in second moment <n_i^2>

There is a solution which looks ugly, but works :

patch the definition of the site basis of the model you're working with. In your example, Bose-Hubbard Hamiltonian uses the basis called "boson". Go to models.xml file and then add a line to the SITEBASIS definition:

<SITEBASIS name="boson"> <PARAMETER name="Nmax" default="infinity"/> <QUANTUMNUMBER name="N" min="0" max="Nmax"/> <OPERATOR name="bdag" matrixelement="sqrt(N+1)"> <CHANGE quantumnumber="N" change="1"/> </OPERATOR> <OPERATOR name="b" matrixelement="sqrt(N)"> <CHANGE quantumnumber="N" change="-1"/> </OPERATOR> <OPERATOR name="n" matrixelement="N"/> <OPERATOR name="n2" matrixelement="N*N"/> <!-- added --> </SITEBASIS>

Like I said, it's ugly, but it works. And, like you, I'd be very much interested in learning how to add measurements properly, without dirty tricks :).

Best,

Zhenya

End of Comp-phys-alps-users Digest, Vol 36, Issue 16

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