October 2015 - Comp-phys-alps-users

inhomogeneous Bose-Hubbard model with MPS
by Dominique Delande 09 Oct '15

09 Oct '15

Dear all, Since at least r7593 (end of July 2015), it is possible to study with MPS inhomogeneous systems, for example an 1D inhomogeneous Bose-Hubbard model with an harmonic trap by using 'inhomogeneous chain lattice' for the lattice and the following definition for the Hamiltonian <HAMILTONIAN name="harm boson Hubbard"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t" default="1"/> <PARAMETER name="V" default="0"/> <PARAMETER name="t'" default="0"/> <PARAMETER name="V'" default="0"/> <PARAMETER name="U" default="0"/> <PARAMETER name="t0" default="t"/> <PARAMETER name="t1" default="t'"/> <PARAMETER name="V0" default="V"/> <PARAMETER name="V1" default="V'"/> <PARAMETER name="K" default="0"/> <BASIS ref="boson"/> <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> <PARAMETER name="U#" default="U"/> <PARAMETER name="K#" default="K"/> -mu#*n(i)+U#*n(i)*(n(i)-1)/2+K#*n(i)*(x-0.5*(L-1))^2 </SITETERM> <BONDTERM source="i" target="j"> <PARAMETER name="t#" default="0"/> <PARAMETER name="V#" default="0"/> -t#*(bdag(i)*b(j)+bdag(j)*b(i)) + V#*n(i)*n(j) </BONDTERM> </HAMILTONIAN> I would like to use an inhomogeneous BONDTERM. I tried things like -(t#+tharm#*(i+j-L)^2)*(bdag(i)*b(j)+bdag(j)*b(i)) or -(t#+tharm#*(x-0.5*(L-1))^2)*(bdag(i)*b(j)+bdag(j)*b(i)) in the definition of the Hamiltonian, but they all produce error messages indicating that mps_optim cannot evaluate such a Hamiltonian. I thus have two questions: * Is inhomogeneous BONDTERM possible with MPS, and how to proceed? * MORE IMPORTANTLY: How can I figure out whether it is possible or not? I find nothing in the documentation, nothing in the Wiki. Is the only solution to look in the guts of the code, or to ask on the mailing list? Thanks a lot in advance for your help. Dominique -- Dominique Delande (Dominique.Delande(a)lkb.upmc.fr) Laboratoire Kastler-Brossel - Case 74 - Universite P. et M. Curie 4, place Jussieu, F-75252 Paris Cedex 05, FRANCE Phone : +33 1 44 27 27 97 - Fax : +33 1 44 27 38 45 Acces : Tour 13, Couloir 12-13, 3eme etage - Bureau 316

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A question about the DMRG of alps
by 郭怀明 06 Oct '15

06 Oct '15

Dear all, Recently I use dmrg of alps. I run three dmrg programs simultaneously and sometimes I get the following information, which stop the program. I raise a question: since the dmrg write files while it is running, is there a problem when several programs run? These program may wirte the same files to the same folder, which will cause a problem. (I use the alps in windows 7). Thank you very much. Sincerely, Huaiming Guo The group '/spectrum' does not exist. Traceback (most recent call last): File "C:\Program Files\VisTrails\Python27_64\lib\site-packages\pyalps\load.py" , line 269, in ReadDiagDataFromFile if 'results' in self.h5f.list_children(respath): PathNotFound: The group '/spectrum' does not exist.

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Defining lattice using graph
by Huaiming Guo 02 Oct '15

02 Oct '15

Dear All, I want to ask how to use graph to define the lattice. I write a graph file named as "a.xml". In the parameter file, I use: GRAPH="C:\alpsproject\lattice\a.xml"; . The a.xml file is as the following. However the output is "could not find". I want to ask how to use it. Thank you very much. Sincerely, Huaiming Guo <GRAPH dimension="2" vertices="8" edges="12"> <VERTEX id="1" type="0"><COORDINATE>0 0</COORDINATE></VERTEX> <VERTEX id="2" type="0"><COORDINATE>0 1</COORDINATE></VERTEX> <VERTEX id="3" type="0"><COORDINATE>1 0</COORDINATE></VERTEX> <VERTEX id="4" type="0"><COORDINATE>1 1</COORDINATE></VERTEX> <VERTEX id="5" type="0"><COORDINATE>2 0</COORDINATE></VERTEX> <VERTEX id="6" type="0"><COORDINATE>2 1</COORDINATE></VERTEX> <VERTEX id="7" type="0"><COORDINATE>3 0</COORDINATE></VERTEX> <VERTEX id="8" type="0"><COORDINATE>3 1</COORDINATE></VERTEX> <EDGE source="1" target="3" id="1" type="0" vector="1 0"/> <EDGE source="1" target="2" id="2" type="1" vector="0 1"/> <EDGE source="2" target="4" id="3" type="0" vector="1 0"/> <EDGE source="3" target="5" id="4" type="0" vector="1 0"/> <EDGE source="3" target="4" id="5" type="1" vector="0 1"/> <EDGE source="4" target="6" id="6" type="0" vector="1 0"/> <EDGE source="5" target="7" id="7" type="0" vector="1 0"/> <EDGE source="5" target="6" id="8" type="1" vector="0 1"/> <EDGE source="6" target="8" id="9" type="0" vector="1 0"/> <EDGE source="7" target="1" id="10" type="0" vector="1 0"/> <EDGE source="7" target="8" id="11" type="1" vector="0 1"/> <EDGE source="8" target="2" id="12" type="0" vector="1 0"/> </GRAPH>

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Re: [ALPS-users] Complex terms in DMRG
by Michele Dolfi 02 Oct '15

02 Oct '15

Hi, The error that you see is not an ALPS problem, but an error from the Python interpreter saying that the variable “I” is not defined. You just have to define the parameter as a string: ‘t0' :-1.0*I, becomes: ‘t0’ : '-1.0*I', Michele -- ETH Zurich Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland dolfim(a)phys.ethz.ch www.itp.phys.ethz.ch +41 44 633 78 56 phone +41 44 633 11 15 fax > On Oct 2, 2015, at 10:42 AM, Huaiming Guo <hmguo(a)buaa.edu.cn> wrote: > > Dear Michele Dolfi, > I use DMRG of alps with complex value. I use Complex=1 in the command line and that works. However when I use the expression in the python way, it return that “I is not defined”. I wonder how to write it in the python way. Thank you very much. > > Sincerely, > Huaiming Guo > <parm.py>

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