If you specify a bond type as in
<BONDTERM type="1" ...>
then you cannot use the # symbol in the coupling t# but need to write explicitly, e.g. t1
Matthias
On Feb 20, 2013, at 3:50 PM, Alex Petrescu tpetresc@gmail.com wrote:
Hi Matthias,
Thanks for your reply. Below is the simplest implementation that I could cook up with free spinless fermions on two sites with *directed* bonds. The output of sparsediag, including the error, is
parsing task files ... Starting task 1. Quantumnumber N going from 0 to 2 with increment 1 Cannot evaluate expression t# * 1 * 1
My short source is attached below. I hope that it's a quick task to figure out what is wrong with the implementation.
Thanks in advance, Alex
Alexandru Petrescu / Physics Department, Yale University
Code attachment
In <alps-dir>/lib/xml/lattices.xml I added
<GRAPH name="my 2-site" vertices="2"> <EDGE source="1" target="2" type="1"/> <EDGE source="2" target="1" type="2"/> </GRAPH> -------------------------------------------------------------------------
In <alps-dir>/lib/xml/models.xml,
<HAMILTONIAN name="free spinless fermions with bondterm type"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t" default="1"/> <BASIS ref="spinless fermion"/> <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> -mu#*n(i) </SITETERM> <BONDTERM type="1" source="i" target="j"> <PARAMETER name="t#" default="t"/> -t#*(cdag(i)*c(j)+cdag(j)*c(i)) </BONDTERM> <BONDTERM type="2" source="i" target="j"> <PARAMETER name="t#" default="t"/> -t#*(cdag(i)*c(j)+cdag(j)*c(i)) </BONDTERM> </HAMILTONIAN> ------------------------------------------------------------------------- The parameter file is
LATTICE="my 2-site";
MODEL="free spinless fermions with bondterm type" NUMBER_EIGENVALUES = 1 CONSERVED_QUANTUMNUMBERS="N" MEASURE_ENERGY = true
t = 3.0; V = 0.0;
{mu=0.00}
If instead "spinless fermions" with V=0 are used in the parameter file, sparsediag works, but all energies come out to be 0.