Comp-phys-alps-users

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1244 discussions

Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 29, Issue 8
by João Manuel Viana Parente Lopes 03 Sep '08

03 Sep '08

Dear Matthias Troyer and Synge Todo, I'm sorry for the late response but I was away from my computer several days! Thank's for your help!! I increased the number of SWEEPS and I have finally found the square root behaviour of the error bars as a function of the number of SWEEPS. I imagine (I didn't had time to check yet) the method of estimation of the error bars makes an underestimation of the variance. Thanks again for your time João Lopes

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Re: [ALPS-users] First alps trials : Decreasing error bars
by João Manuel Viana Parente Lopes 29 Aug '08

29 Aug '08

On Aug 28, 2008, at 11:00 AM, comp-phys-alps-users- request(a)phys.ethz.ch wrote: > 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 > > 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. First alps trials (Jo?o Manuel Viana Parente Lopes) > 2. Re: First alps trials (Matthias Troyer) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 27 Aug 2008 23:56:53 +0100 > From: Jo?o Manuel Viana Parente Lopes <jvianalopes(a)gmail.com> > Subject: [ALPS-users] First alps trials > To: comp-phys-alps-users(a)phys.ethz.ch > Message-ID: <40B2C500-9E6E-45A9-A170-91187657132C(a)gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Dear colleagues, > > I'm making my first experiments with Alps... > I was comparing the average energy for small temperatures (T~ 0.01, J > = 1) in the 1D Heisenberg model > with the exact solution for small open linear chains using the loop > program with de SSE representation. > > I notice that I can not decrease the error bars by the increase of > the numbers of SWEEPS! > How can I decrease the error bars? > > Thanks in advance > > Jo?o Lopes > > PS: A sugestion: It would be very helpful if we could do a search in > the mailing list > Maybe this link could help: http://wiki.list.org/display/DOC/How+do+I > +make+the+archives+searchable > >

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First alps trials
by João Manuel Viana Parente Lopes 28 Aug '08

28 Aug '08

Dear colleagues, I'm making my first experiments with Alps... I was comparing the average energy for small temperatures (T~ 0.01, J = 1) in the 1D Heisenberg model with the exact solution for small open linear chains using the loop program with de SSE representation. I notice that I can not decrease the error bars by the increase of the numbers of SWEEPS! How can I decrease the error bars? Thanks in advance João Lopes PS: A sugestion: It would be very helpful if we could do a search in the mailing list Maybe this link could help: http://wiki.list.org/display/DOC/How+do+I +make+the+archives+searchable

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Correlation function and complex lattices
by sadegh raeisi 25 Aug '08

25 Aug '08

Dear all, I have defined a graphlattice which has 2 particles on each site. In other words the unit cell includes 2 vertices. But I encountered a problem using this lattice. the problems is about the correlation functions. For instance, when I want to calculate the <SzSz> correlation function( MEASURE_CORRELATIONS[Diagonal spin correlations]=Sz ) it seems that ALPS calculates the corresponding function between sites of the lattice instead of particles(vertices) on a sites. Also there is noway to calculate the correlation functons between particles on one site. I will be grateful if any one can help me. Best regards S. Raeisi ---------------------------------------------- Sadegh Raeisi Department of Physics Sharif University of Technology Quantum Information Group ----------------------------------------------

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Ising/Potts-like Heisenberg simulation
by Fritz Koermann 23 Aug '08

23 Aug '08

Hi, is it possible to define a kind of 'Ising-type' or Potts-like model for the 3D Heisenberg MC simulation as in PRB 72,134426, where the unit vectors are restricted to lie on a cone defined by a discrete spin-z-component Sz=-S,...+S? For S=1/2 this would correspond to the usual Ising model. Is it possible to define therefor a spin number, lets say S, so that the z-component is restricted to have a value between -S and +S where the x- and y-components are still chosen randomly? Best and thanks for the great support! Fritz --- Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1 D-40237 Düsseldorf Handelsregister B 2533 Amtsgericht Düsseldorf Geschäftsführung Prof. Dr. Jörg Neugebauer Prof. Dr. Anke R. Pyzalla Prof. Dr. Dierk Raabe Prof. Dr. Martin Stratmann Dipl.-Kfm. Herbert Wilk Ust.-Id.-Nr.: DE 11 93 58 514 Steuernummer: 105 5891 1000 -------------------------------------------------

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CECAM
by Matthias Troyer 17 Aug '08

17 Aug '08

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Re: [ALPS-users] correlation function+susceptibility
by Fritz Koermann 12 Aug '08

12 Aug '08

Dear Prof. Matthias Troyer, many thanks for your answer :)! > Do you want to measure the real-space correlation function or is the > magnetic susceptibility as an integrated measure enough? We would like to measure the real-space correlation function in order to separate between short- and long-range interactions and their influence on the internal energy. Is it possible to measure such a function using alps? I have two more minor questions concerning the output: Is the susceptibility \chi given out by alps equivalent to \chi=\beta*(<m^2>-<m>^2)? Is it possible to make a snapshot (spin position+spin alignment) of the spin system at a certain time-step? Again many, many thanks for your support. Best regards, Fritz Koermann --- Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1 D-40237 Düsseldorf Handelsregister B 2533 Amtsgericht Düsseldorf Geschäftsführung Prof. Dr. Jörg Neugebauer Prof. Dr. Anke R. Pyzalla Prof. Dr. Dierk Raabe Prof. Dr. Martin Stratmann Dipl.-Kfm. Herbert Wilk Ust.-Id.-Nr.: DE 11 93 58 514 Steuernummer: 105 5891 1000 -------------------------------------------------

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costume measurement
by sadegh raeisi 06 Aug '08

06 Aug '08

Dear all > I am using the ALPS to do my DMRG simulation and as a part of my > simulation I need to calculate the > correlation function between particles on different sites of a ladder, > but I encountered a problem defining > my custom measurements. Unfortunately, the corresponding section in > tutorial is empty. > I'll be grateful if you can help me to define my custom measurements. > Best regards, -- ---------------------------------------------- Sadegh Raeisi Department of Physics Sharif University of Technology Quantum Information Group ----------------------------------------------

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ALPS group on LinkedIn
by Matthias Troyer 27 Jul '08

27 Jul '08

Dear ALPS users and developers, I have created an ALPS group on the LinkedIn IT-networking site. Feel free to join using the link http://www.linkedin.com/e/gis/144124/5E1E716924F5 Matthias

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question about spin susceptibility
by Gang Chen 27 Jul '08

27 Jul '08

Hi All, Sorry to bother, I have a question about spin susceptibility. In my problem, the total spin is not a good quantum number. If I apply exact diagonalization code, how do I obtain spin susceptibility? One thing you might suggest is to measure total spin Sz (say the applied magnetic field is along z direction), and calculate \chi approximated as (<S_z>_h - <S_z>_{h=0}) /h. Then how to ask ALPS to measure <S_z>? Same question for quantum monte carlo. Could anyone be kind to offer a help? Thanks, -- GANG CHEN Department of Physics U.C. Santa Barbara

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