February 2010 - Comp-phys-alps-users

Problems with worms??
by Jakub Zakrzewski 27 Oct '10

27 Oct '10

Hello, Sometimes QMC worm code (used on Bose-Hubbard) terminates with the following error: here come first earlier succesful simulations then ... Created run 85 remote on Host ID: 84 Created run 86 remote on Host ID: 85 Created run 87 remote on Host ID: 86 Created run 88 remote on Host ID: 87 All processes have been assigned Checking if Simulation 1 is finished: not yet, next check in 120 seconds ( 0% done). q = -0 state1 = 0 state2 = 0 bond_type = 0 zero matrix element in remove_jump application called MPI_Abort(MPI_COMM_WORLD, -2) - process 67 Could somebody advice what I can do? Best regards Kuba

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sigma_y interaction
by Fernando Cucchietti 28 Feb '10

28 Feb '10

Hello, I probably know the answer to this already, but just wanted to check: I would like to use the Montecarlo code to simulate a system with a Hamiltonian that has the Sy operator, that is Sy=-I/2(Splus-Sminus). The worm and sse codes return a runtime error "can not convert complex number into real one". If I don't include de I constant (or (0.,1.) ) in the model.xml file the code starts, but then complains that it cannot simulate this term (which without the complex unit is non-Hermitian). I cannot rotate my basis because I also have the Sx operator, so I am stuck with Sy. Is there a way to do this? It looks like a no-no... Thanks Fernando -- ============================== Fernando Cucchietti Research Fellow ICFO-Institut de Ciencies Fotoniques Mediterranean Technology Park Av. Canal Olimpic s/n 08860 Castelldefels (Barcelona), Spain ============================== 1+1=3, for large values of 1 ------------------------------

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Exact Diagonalization for Bose-Hubbard
by Vipin Varma 19 Feb '10

19 Feb '10

Hi I am trying the Lanczos method for solving the Bose-Hubbard model on a square lattice, to get the t/U dependence of the ground state energy per site. I tried a simple 2x1 cluster with open and periodic boundary conditions and I get a linear dependence for the energy on t/U; analytically (which I am reasonably sure is correct), I get a parabolic dependence for the energy on t/U, if I consider 2 bosons over 2 sites. Here is my parameter file: /////////////////////////// LATTICE_LIBRARY="../lattices.xml"; LATTICE="square lattice"; MODEL_LIBRARY="../models.xml"; MODEL="boson Hubbard"; U = 1; Nmax = 2; L=2; W =1; {t=0.1;} {t=0.01;} {t=0.02;} {t=0.03;} {t=0.04;} {t=0.05;} {t=0.06;} {t=0.07;} {t=0.08;} {t=0.09;} /////////////////// I have tried Nmax = 2,4,6, but all give me a linear dependence; also strangely, the energy range does not change much when I vary the value of U by orders of magnitude. I guess I am missing something simple. Any ideas will be appreciated. Vipin

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Python distributions
by Matthias Troyer 05 Feb '10

05 Feb '10

Dear ALPS developers and users, Since ALPS 2.0, to be released later this year in a beta version, will rely heavily on Python for data analysis I want to start a survey about the Python distributions you are using. We might be able to prepare compiled binary installation packages for the most common combinations of OS/compiler/Python distribution. Please reply to the list with the Python distribution you are using if you feel strongly about that distribution you are using now and don't want to change it when using ALPS 2.0 in the future. Matthias PS: you will always be able to compile ALPS from source against any distribution, but many people prefer the new binary installations that can be installed in less than a minute.

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