- Comp-phys-alps-users - lists.phys.ethz.ch

size of prob table is zero
by Tadeusz Wasiutyński 10 Feb '16

10 Feb '16

Dears, when running dirloop_sse on the following data containing 15 centers: ------------------------------------------ import pyalps import matplotlib.pyplot as plt import pyalps.plot parms = [] for t in [1.0, 2.0, 3.0, 4.0]: parms.append( { 'LATTICE' : "Mn9W6", 'LATTICE_LIBRARY' : "mn9w6-graph.xml", 'MODEL' : "spin", 'CONSERVED_QUANTUMNUMBERS' : 'Sz', 'local_S0' : 0.5, 'local_S1' : 0.5, 'J0' : 13.0, 'J1' : 27.8, 'D' : -0.02, 'T' : t, 'h' : 0, 'ALGORITHM' : "dirloop_sse", 'THERMALIZATION' : 100000, 'SWEEPS' : 8200000, } ) ---------------------------------------------- everything goes smoothly. When either of spins is raised the following error occurs: size of prob table is zero On the other hand loop algorithm runs without problems. Any idea what is going here? regards -- Tadeusz Wasiutyński

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Correlation of two bond operators in mps_optim
by Michael Pasek 10 Feb '16

10 Feb '16

Dear all, I am trying to compute the correlation of two bond operators as follows: p['MEASURE_CORRELATIONS[custom op]'] = 'cppdag:cpp' where cpp and cppdag are define in mymodel.xml as: <BONDOPERATOR name="cpp" source="x" target="y"> c_up(x)*bdag(x)*c_up(y)*bdag(y) </BONDOPERATOR> <BONDOPERATOR name="cppdag" source="x" target="y"> b(x)*cdag_up(x)*b(y)*cdag_up(y) </BONDOPERATOR> where bdag, b, cdag_up and c_up are the usual boson, fermion creation-annihilation operators. Disappointingly, in this case mps_optim only outputs a single number for the correlation measurement. If I try instead to compute the correlation 'oppdag:opp' with <BONDOPERATOR name="opp" source="x" target="y"> bdag(x)*c_up(y) </BONDOPERATOR> <BONDOPERATOR name="oppdag" source="x" target="y"> cdag_up(x)*b(y) </BONDOPERATOR> ... I get a 4x4 matrix (i,i+1,j,j+1) as expected. So the problem seems to come from computing the correlation of bond operators that are products of more than two site operators. Is this measurement expected to fail with mps_optim, or am I doing something wrong? Thank you for your help. Michael

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compute the kinetic energy
by 北尘心 09 Feb '16

09 Feb '16

Hi, Thank you very much for your suggestion and detailed explanation. Yours sincerely, Xingbo Wei Zhejiang Normal Universtiy, Jinhua, 230014, China

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compute the kinetic energy
by 北尘心 09 Feb '16

09 Feb '16

Dear all, I am trying to compute the kinetic energy in the hubbard model by means of mps or dmrg code .Can mps or dmrg code measure it directly?If it can, how should I set in model and custom measurements ? Yours sincerely, Xingbo Wei Zhejiang Normal Universtiy, Jinhua, 230014, China

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 119, Issue 2
by Wang Lei 06 Feb '16

06 Feb '16

> On Feb 6, 2016, at 12:00 PM, comp-phys-alps-users-request(a)lists.phys.ethz.ch wrote: > > Send Comp-phys-alps-users mailing list submissions to > comp-phys-alps-users(a)lists.phys.ethz.ch > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.phys.ethz.ch/listinfo/comp-phys-alps-users > or, via email, send a message with subject or body 'help' to > comp-phys-alps-users-request(a)lists.phys.ethz.ch > > You can reach the person managing the list at > comp-phys-alps-users-owner(a)lists.phys.ethz.ch > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Comp-phys-alps-users digest..." > > > Today's Topics: > > 1. Topological properties and exact diagonalization > (Marco Di Liberto) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 5 Feb 2016 18:53:10 +0100 > From: Marco Di Liberto <m.f.diliberto(a)uu.nl> > To: "comp-phys-alps-users(a)lists.phys.ethz.ch" > <comp-phys-alps-users(a)lists.phys.ethz.ch> > Subject: [ALPS-users] Topological properties and exact diagonalization > Message-ID: > <CAN_y_feEzPAB-EoNTYQrmnF__O+O+gWgZW9HSgF0-XGvgttDnQ(a)mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Hi, > > I am wondering whether it is easily possible to extract topological > quantities, like the chern number, for a many-body system using the exact > diagonalization routines of alps. > To compute the Chern number in ED you can apply twisted boundary condition to a torus; compute wave function overlaps on a mesh; then sum them up. However, this is is not easily done with ALPS-ED. Another option to extract topological quantities is to insert flux to a cylindrical system and observe charge pumping from physical observables such as occupation number. > Moreover, can one get the wavefunction components from the exact > diagonalization routines? By setting “PRINT_EIGENVECTORS” to true, one can print out the basis and wavefunctions. > Regards, > > --- > Marco Di Liberto >

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Topological properties and exact diagonalization
by Marco Di Liberto 05 Feb '16

05 Feb '16

Hi, I am wondering whether it is easily possible to extract topological quantities, like the chern number, for a many-body system using the exact diagonalization routines of alps. Moreover, can one get the wavefunction components from the exact diagonalization routines? Regards, --- Marco Di Liberto

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DMRG Crashing frequently
by T.J.Hewitt 03 Feb '16

03 Feb '16

Dear ALPS users, I've been having issues with the stability of the DMRG program provided by ALPS (2.2.b4). The program has been crashing quite frequently. I can run maybe 3-5 simulations before the program crashes. I had no problems with the program when a started using ALPS a few months ago. Unfortunately the crash seems to also take other applications with it, in that other programs will cease to start or function properly. Such programs include dnf, Problem Reporting, logs, gedit and gnome-shell. In order to get everything working correctly a full system reboot is needed. I can't find much in the way of error information. Problem Reporting tells me a segmentation fault occurred and the terminal output gives an std::bad_alloc error. Often a crash will cause the computer to freeze for several minutes before it starts working again. The crashes occur on simple programs, even those provided in the ALPS DMRG Tutorials. I've tried recompiling and rebuilding ALPS from scratch but it still results in the same crashing of DMRG. I'm using a Fedora 22 system and I followed the ALPS installation instructions along with those given here<https://lists.phys.ethz.ch/pipermail/comp-phys-alps-users/2013/002005.html>. Although I edited a few make files so the cmake commands would correctly find the lapack and lpsolve libraries. Perhaps I missed an error or warning during the build process or there is an incompatibility between Fedora 22 and ALPS. I've tried looking through the logs and error reports to find a clue but have come up with very little. I've also had a look through the mailing list archives to see if anyone else has had an issue such as this but I was able to find anything. I can post any logs or error reports if needed. Does anyone experienced an issue such as this or have a suggestion about it? Thanks, Tyler Hewitt

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a problem when i use 2 band chain lattice
by 北尘心 27 Jan '16

27 Jan '16

Dear all, I want to use 2 band chain lattice (there are three edge types in unitcell) in my hubbard model which is in lattices.xml file. I build the lattice according to guidance in the website: <LATTICES> <LATTICE name="chain lattice" dimension="1"> <PARAMETER name="a" default="1"/> <BASIS><VECTOR>a</VECTOR></BASIS> <RECIPROCALBASIS><VECTOR>2*pi/a</VECTOR></RECIPROCALBASIS> </LATTICE> <UNITCELL name="2band1d" dimension="1"> <VERTEX type="0"/> <VERTEX type="1"/> <EDGE type="0"><SOURCE vertex="1" offset="0"/><TARGET vertex="2" offset="0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0"/><TARGET vertex="1" offset="1"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0"/><TARGET vertex="2" offset="1"/></EDGE> </UNITCELL> <LATTICEGRAPH name = "2 band chain lattice"> <FINITELATTICE> <LATTICE ref="chain lattice"/> <EXTENT dimension="1" size ="L"/> <BOUNDARY type="periodic"/> </FINITELATTICE> <UNITCELL ref="2band1d"/> </LATTICEGRAPH> </LATTICES> Because there are three edge types in unitcell , i wonder what I should do to design hopping in my model. I design two solutions ,like : <HAMILTONIAN name="boson Hubbard"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t0" default="1"/> <PARAMETER name="t1" default="2"/> <PARAMETER name="t2" default="3"/> <PARAMETER name="U" default="0"/> <BASIS ref="boson"/> <SITETERM site="i"> -mu*n(i)+U*bdag(i)*bdag(i)*b(i)*b(i)/2 </SITETERM> <BONDTERM type="0" source="i" target="j"> -t0*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> <BONDTERM type="1" source="i" target="j"> -t1*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> <BONDTERM type="2" source="i" target="j"> -t2*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> </HAMILTONIAN> and <HAMILTONIAN name="boson Hubbard"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t0" default="1"/> <PARAMETER name="t1" default="2"/> <PARAMETER name="t2" default="3"/> <PARAMETER name="U" default="0"/> <BASIS ref="boson"/> <SITETERM site="i"> -mu*n(i)+U*bdag(i)*bdag(i)*b(i)*b(i)/2 </SITETERM> <BONDTERM source="i" target="j"> -t0*(bdag(i)*b(j)+bdag(j)*b(i))-t1*(bdag(i)*b(j)+bdag(j)*b(i))-t2*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> </HAMILTONIAN> I want to know my two design which one is correct? Yours sincerely, Xingbo Wei Zhejiang Normal Universtiy, Jinhua, 230014, China

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sawtooth lattice
by 北尘心 27 Jan '16

27 Jan '16

Dear ALPS community, I have some problems about sawtooth lattice, which is shown in paper 'Bose condensation in flat bands (PhysRevB.82.184502)'. After having canvassed the ALPS tutorial, I construct an one-dimensional lattice with nearest-nearest neighbor hopping and next-nearest neighbor hopping, which is equivalent to the sawtooth lattice. Unfortunately, I still can't follow Fig4(b) of Phys. Rev. B 82, 184502 (2010). The job, lattices.xml and models.xml are shown as follows. I don't know what's wrong with my codes. Could you give me any suggestions ? Thank you very much ! ------------------------------------------------------------------------------------------------------------- job: LATTICE_LIBRARY="lattices.xml" MODEL_LIBRARY="models.xml" LATTICE="sawtooth open chain lattice"; MODEL="sawtooth boson Hubbard"; SWEEPS=20; MAXSTATES=200; T=0; t=1.0 t'=sqrt(2) U=1.0; MEASURE_LOCAL[n_density]=n MEASURE_CORRELATIONS[n_correlation]="n:n" CONSERVED_QUANTUMNUMBERS="N"; {L=40,N_total=20,Nmax=20;} {L=40,N_total=21,Nmax=21;} {L=40,N_total=22,Nmax=22;} {L=40,N_total=23,Nmax=23;} {L=40,N_total=24,Nmax=24;} ------------------------------------------------------------------------------------------------------------- lattice.xml: <LATTICES> <LATTICE name="chain lattice" dimension="1"> <PARAMETER name="a" default="1"/> <BASIS><VECTOR>a</VECTOR></BASIS> <RECIPROCALBASIS><VECTOR>2*pi/a</VECTOR></RECIPROCALBASIS> </LATTICE> <UNITCELL name="sawtooth" dimension="1"> <VERTEX id="1" type="0"><COORDINATE>0 </COORDINATE></VERTEX> <VERTEX id="2" type="1"><COORDINATE>0.5 </COORDINATE></VERTEX> <EDGE type="0"><SOURCE vertex="1" offset="0"/><TARGET vertex="2" offset="0"/></EDGE> <EDGE type="1"><SOURCE vertex="1" offset="0"/><TARGET vertex="1" offset="1"/></EDGE> <EDGE type="2"><SOURCE vertex="2" offset="0"/><TARGET vertex="1" offset="1"/></EDGE> </UNITCELL> <LATTICEGRAPH name = "sawtooth open chain lattice"> <FINITELATTICE> <LATTICE ref="chain lattice"/> <EXTENT dimension="1" size ="L"/> <BOUNDARY type="open"/> </FINITELATTICE> <UNITCELL ref="sawtooth"/> </LATTICEGRAPH> </LATTICES> ------------------------------------------------------------------------------------------------------------- model.xml: <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"/> </SITEBASIS> <HAMILTONIAN name="sawtooth boson Hubbard"> <PARAMETER name="t" default="1"/> <PARAMETER name="t'" default="0"/> <PARAMETER name="U" default="0"/> <BASIS ref="boson"/> <SITETERM site="i"> U*bdag(i)*bdag(i)*b(i)*b(i)/2 </SITETERM> <BONDTERM type="0" source="i" target="j"> -t'*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> <BONDTERM type="1" source="i" target="j"> -t*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> <BONDTERM type="2" source="i" target="j"> -t'*(bdag(i)*b(j)+bdag(j)*b(i)) </BONDTERM> </HAMILTONIAN> ------------------------------------------------------------------------------------------------------------- Best regards, Xiaofan Zhou

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Negative Truncation error calculated by DMRG algorithm
by T.J.Hewitt 25 Jan '16

25 Jan '16

Dear ALPS users, I've been using the DMRG algorithm provided by ALPS to calculate energies and spin gaps for simple quantum systems. I've noticed that the value calculated for the truncation error comes out to be negative for some of the iterations. These specific instances have very small values, typically 10^-16, 10^-17 and 10^-18. My understanding of the truncation error is that it is the sum of the probabilities of the truncated states, thus always producing a positive value. So I'm not sure how a negative truncation error is occurring. It seems to occur on any DMRG program I run, even the simple ones provided in the DMRG tutorials. Perhaps it is a quirk of the algorithm or how the computer is handling some rounding. I found message on the mailing list archives about this exact question but it was never answered. I've attached some output data. I used the program 'spin_one_half.py' straight from the first DMRG tutorial here<http://alps.comp-phys.org/mediawiki/index.php/ALPS_2_Tutorials:DMRG-01_DMRG>, unmodified, to produce the provided output. Any insight and advice is much appreciated. Thanks. Regards, Tyler

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