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Off diagonal measurements in QMC
by Fernando Cucchietti 28 Nov '09

28 Nov '09

Hello all, I am learning how to use the ALPS applications. I had reasonable success with DMRG with which I am experienced, however I was trying to study two dimensional systems with QMC and I ran into a problem: The ALPS application complains that it will not measure off-diagonal observables such as sigma_x, even less for two operators like sigma^plus_i sigma^minus_j. It measures without any problems sigma_z and correlations of sigma_z operators. Now, my ignorance of QMC is such that I don't know if this is an intrinsic limitation of Quantum Montecarlo algorithms or just of the particular example application distributed with ALPS -- this is my first question. My second question is: if it is possible to measure e.g. sigma_x, could you give me a rough estimate of how difficult could it be to implement it with the libraries? Thanks in advance, Fernando Cucchietti

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worm and dirloop_sse for Bose-Hubbard model
by Fu-Jiun Jiang ITP 26 Nov '09

26 Nov '09

Dear ALPS users For the extended Bose-Hubbard H = -t\sum_{<i,j>} a^{\dagger}_i a_j +\frac{U}{2}\sum_{i}n_i(n_i-1) + V\sum_{<i,j>}n_in_j -\mu\sum_{i}n_i, I wonder why worm and dirloop_sse in ALPS show two completely different results? Another technique problem as follows. Can one change parameters Nmax = 2 or NONLOCAL = 0 in the tutorial? I am not sure what's the impact of these two parameters. Any help will be greatly appreciated. THANKS! Sincerely, Fu-Jiun

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Bls: Comp-phys-alps-users Digest, Vol 44, Issue 8
by Muhammad Rofiq 25 Nov '09

25 Nov '09

I used the Heisenberg model for S = 1/2 such as done on experiment, but I still having difficulty to make couling of lattice cubic, my lattice stucture is like in enclosure file --- Pada Sel, 24/11/09, comp-phys-alps-users-request(a)phys.ethz.ch <comp-phys-alps-users-request(a)phys.ethz.ch> menulis: Dari: comp-phys-alps-users-request(a)phys.ethz.ch <comp-phys-alps-users-request(a)phys.ethz.ch> Judul: Comp-phys-alps-users Digest, Vol 44, Issue 8 Kepada: comp-phys-alps-users(a)phys.ethz.ch Tanggal: Selasa, 24 November, 2009, 6:00 PM Send Comp-phys-alps-users mailing list submissions to comp-phys-alps-users(a)phys.ethz.ch To subscribe or unsubscribe via the World Wide Web, visit https://webmail.phys.ethz.ch/mailman/listinfo/comp-phys-alps-users or, via email, send a message with subject or body 'help' to comp-phys-alps-users-request(a)phys.ethz.ch You can reach the person managing the list at comp-phys-alps-users-owner(a)phys.ethz.ch Message: 3 Date: Tue, 24 Nov 2009 08:44:53 +0800 (SGT) From: Muhammad Rofiq <roq_4q(a)yahoo.co.id> Subject: [ALPS-users] lattice.... To: comp-phys-alps-users(a)phys.ethz.ch Message-ID: <550593.22765.qm(a)web76516.mail.sg1.yahoo.com> Content-Type: text/plain; charset="iso-8859-1" Dear all,, When I simulate the susceptibility of Cd0.3Mn0.7Te, I had a problem of my results. The result has obtained not to synchronize with theory. I get 5K of Neel Temperature, while the theory is 23 of Neel Temperature. is there's any mistake with my cubic lattice? my cubic lattice is : <LATTICES> <GRAPH name="latiskubik"> ?<VERTEX id="1" type="0"/> <VERTEX id="2" type="0"/><VERTEX id="3" type="1"/> ?<VERTEX id="4" type="0"/><VERTEX id="5" type="0"/> <VERTEX id="6" type="0"/> ?<VERTEX id="7" type="0"/> <VERTEX id="8" type="1"/> <VERTEX id="9" type="0"/> ?<VERTEX id="10" type="0"/> ?<EDGE type="0" source="1" target="2"/><EDGE type="1" source="2" target="3"/> ?<EDGE type="0" source="4" target="1"/><EDGE type="1" source="3" target="4"/> ?<EDGE type="0" source="5" target="4"/><EDGE type="1" source="6" target="3"/> ?<EDGE type="0" source="5" target="6"/><EDGE type="1" source="7" target="8"/> ?<EDGE type="0" source="6" target="7"/><EDGE type="1" source="8" target="5"/> ?<EDGE type="0" source="9" target="10"/><EDGE type="1" source="8" target="9"/> ?<EDGE type="0" source="10" target="7"/> </GRAPH> </LATTICES> Thanks before,, Buat sendiri desain eksklusif Messenger Pingbox Anda sekarang! Membuat tempat chat pribadi di blog Anda sekarang sangatlah mudah. http://id.messenger.yahoo.com/pingbox/

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lattice....
by Muhammad Rofiq 24 Nov '09

24 Nov '09

Dear all,, When I simulate the susceptibility of Cd0.3Mn0.7Te, I had a problem of my results. The result has obtained not to synchronize with theory. I get 5K of Neel Temperature, while the theory is 23 of Neel Temperature. is there's any mistake with my cubic lattice? my cubic lattice is : <LATTICES> <GRAPH name="latiskubik"> <VERTEX id="1" type="0"/> <VERTEX id="2" type="0"/><VERTEX id="3" type="1"/> <VERTEX id="4" type="0"/><VERTEX id="5" type="0"/> <VERTEX id="6" type="0"/> <VERTEX id="7" type="0"/> <VERTEX id="8" type="1"/> <VERTEX id="9" type="0"/> <VERTEX id="10" type="0"/> <EDGE type="0" source="1" target="2"/><EDGE type="1" source="2" target="3"/> <EDGE type="0" source="4" target="1"/><EDGE type="1" source="3" target="4"/> <EDGE type="0" source="5" target="4"/><EDGE type="1" source="6" target="3"/> <EDGE type="0" source="5" target="6"/><EDGE type="1" source="7" target="8"/> <EDGE type="0" source="6" target="7"/><EDGE type="1" source="8" target="5"/> <EDGE type="0" source="9" target="10"/><EDGE type="1" source="8" target="9"/> <EDGE type="0" source="10" target="7"/> </GRAPH> </LATTICES> Thanks before,, Buat sendiri desain eksklusif Messenger Pingbox Anda sekarang! Membuat tempat chat pribadi di blog Anda sekarang sangatlah mudah. http://id.messenger.yahoo.com/pingbox/

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A problem with LAPACK_SUPPORT in ALPS library installation
by 周振肖 23 Nov '09

23 Nov '09

Hi all, Thers is a confusing problem when I try to install the ALPS library. The configure line I used: ./configure --prefix=/home/gontp/app/alps1 --with-boost=/home/gontp/app/boost_1_33_1 --with-blas-dir=/usr/lib --with-blas="-lblas -lf2c" --with-lapack-dir=/usr/lib --with-lapack="-llapack -lblas -lf2c" CXXFLAGS="-O2 -g" CXX=g++ the liblapack.a and libblas.a are already included in the /usr/lib but the result is always like this Summary of configuration: ALPS version 1.3.4 prefix /home/gontp/app/alps1 compiler type gnu [g++] optimization yes exceptions yes warnings no Boost version 1_33 MPI support no HDF5 support no LAPACK support no SQLite support no XML parser native Documentation no *with LAPACK_support no * Is there anything wrong in my configure line? Thank you PS: Linux=Ubuntu 9.04 and the g++ version=4.3.3 -- Zhou Zhen-Xiao Group of Theoretical Nuclear Physics School of Nuclear Science and Technology Lanzhou University China

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Bilayer Heisenberg model
by Fu-Jiun Jiang ITP 18 Nov '09

18 Nov '09

Dear all If I want to study bilayer Heisenberg model, what's wrong with the following Hamiltonian (the error message read " bad lexical cast: source type value could not be interpreted as target ")? Many thanks in advance. <PARAMETER name="Az" default="Q"/> <PARAMETER name="Axy" default="Az"/> <PARAMETER name="Q" default="1"/> <PARAMETER name="A1z" default="Q2"/> <PARAMETER name="A1xy" default="Q3"/> <PARAMETER name="h" default="h1"/> <BASIS ref="spin"/> <SITETERM site="i"> -h1*Sz(i) </SITETERM> <BONDTERM type="1" source="i" target="j"> Az*Sz(i)*Sz(j)+Axy*exchange_xy(i,j) </BONDTERM> <BONDTERM type="0" source="i" target="j"> A1z*Sz(i)*Sz(j)+A1z*A1xy*exchange_xy(i,j) </BONDTERM> Sincerely, Fu-Jiun

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honeycomb lattices
by Fu-Jiun Jiang ITP 14 Nov '09

14 Nov '09

Hello all Can some experts kindly tell me how to construct a honeycomb lattice in ALPS so that an area with Lx = Ly = L contains 2L^2 spins? Thanks. Sincerely, Fu-Jiun

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Lattice graph.
by Michal Maik 06 Nov '09

06 Nov '09

Hi, I'm a new user to the Alps program, so this may be a trivial question. I have gone through most of the tutorials and I'm getting familiar with the program. One thing I can't figure out is how to display a picture of the lattice that I define. What I mean is how do I go from the hml code for a lattice to to a graph of it? What program can I use to display it? For example, in the tutorial you write: <GRAPH vertices="5" edges="5"> <EDGE source="1" target="2"/> <EDGE source="2" target="3"/> <EDGE source="1" target="4"/> <EDGE source="2" target="5"/> <EDGE source="4" target="5"/> </GRAPH> Then you show what this lattice looks like. How can I get that picture to display? My main concern is that since I'm new to the program I would like to see if a lattice that I think I have defined is actually the lattice that I want. Thanks.

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structure function in alps
by Fu-Jiun Jiang ITP 06 Nov '09

06 Nov '09

Dear all I got two quick questions for you as follows. 1. Can one force Alps to measure only k = 0 or k = \pi/2 part of the structure function? Looking into the code, I know how this can be done in the sse_dirloop code (one just cooks up his/her measurements) , how about the looper? 2. Does alps already take into account the prefactor for each type of sublattices when measure the structure function. For example, for honeycomb lattice, since one got two type of sublattices, it is useful to use +1 for one type sublattice and -1 for another type of sublattice. Sincerely, FJ

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A looper question: "Binder ratio of Generalized Magnetization"==""Binder ratio of Staggered Magnetization"" for antiferromagnetic models?
by Prsa Krunoslav 05 Nov '09

05 Nov '09

Dear ALPS maintainers and users, Thanks for your generous help and advice. I would like to calculate the Neel temperature of a 3D antiferromagnet within the Heisenberg model using the looper application as a function of ratio of the two main interactions, J2/J1. The Binder ratio B(T) for different system dimensions L seems like the easiest way to calculate the transition temperature. Both interactions are unfortunately antiferromagnetic, giving rise to a small frustration. The lattice is not bipartite anymore as soon as the J2 is introduced. This removes the possibility of using the staggered magnetization Ms, Ms^2, Ms^4 and the Binder ratio Bs=<Ms^4>/(<Ms^2>)^2. However, there is an additional observable still available called the "Generalized magnetization", its square, etc. Does its Binder ratio (observable "Binder Ratio of Generalized Magnetization") correspond to the Binder ratio for staggered magnetizations for antiferromagnetic models? Does this hold if the classical ground state of the given model is, say, spiral? I.e. can I in principle use this observable to determine the order transitions for all possible models? I am thankful for any help you may provide. All the best. Kruno --------------------------------------------- Krunoslav Prsa, PhD student, Laboratory for neutron scattering, ETH Zurich and Paul Scherrer Institute CH-5232 Villigen-PSI, Switzerland tel:+41 56 310 20 91 ---------------------------------------

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