Dear Niall,

Although the transverse-field Ising model is not defined in models.xml explicitly, it is already included as a special case (ie. Jxy = 0) of the model "spin". The strength of transverse field is specified by a parameter "Gamma".

Best, Synge Todo

From: Niall Moran nmoran@thphys.nuim.ie Date: Thu, 20 Sep 2007 17:11:31 +0100

Hi all,

I am trying to do some quantum Monte Carlo simulations on a simple 1D Ising model with a transverse field. I could not find any Ising model specified in the standard models.xml file. I created a file called ising_model.xml with contents listed below. Could anyone verify if this is correct as I am new to this and do not fully understand how to specify models.

Kind Regards,

Niall.

<MODELS> <SITEBASIS name="spin"> <PARAMETER name="local_spin" default="local_S"/> <PARAMETER name="local_S" default="1/2"/> <QUANTUMNUMBER name="S" min="local_spin" max="local_spin"/> <QUANTUMNUMBER name="Sz" min="-S" max="S"/> <OPERATOR name="Splus" matrixelement="sqrt(S*(S+1)-Sz*(Sz+1))"> <CHANGE quantumnumber="Sz" change="1"/> </OPERATOR> <OPERATOR name="Sminus" matrixelement="sqrt(S*(S+1)-Sz*(Sz-1))"> <CHANGE quantumnumber="Sz" change="-1"/> </OPERATOR> <OPERATOR name="Sz" matrixelement="Sz"/> </SITEBASIS>

<BASIS name="spin"> <SITEBASIS ref="spin"> <PARAMETER name="local_spin" value="local_S#"/> <PARAMETER name="local_S#" value="local_S"/> <PARAMETER name="local_S" value="1/2"/> </SITEBASIS> <CONSTRAINT quantumnumber="Sz" value="Sz_total"/> </BASIS>

<SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR>

<HAMILTONIAN name="ising_spin"> <PARAMETER name="h" default="0"/> <BASIS ref="spin"/> <SITETERM site="i"> <PARAMETER name="h" default="h"/> -h*Sx(i) </SITETERM> <BONDTERM source="i" target="j"> <PARAMETER name="J" default="J"/> -J*Sz(i)*Sz(j) </BONDTERM> </HAMILTONIAN> </MODELS>