November 2013 - Comp-phys-alps-users

Inconsistent comment in generate_spline_matrix in the DMFT folder
by Kuangshing Chen 22 Jul '15

22 Jul '15

Hi, The function generate_spline_matrix in fouriertransform.C in the dmft folder shows the comments as follows: // A is the matrix whose inverse defines spline_matrix // // 6 6 // 1 4 1 // 1 4 1 // A = ... // // 1 4 1 // -2 0 0 2 However, the following codes, dense_matrix A = 4*dt/6.*boost::numeric::ublas::identity_matrix<double>(Np1); for (int i=1; i<Np1-1; i++) { A(i,i-1) = dt/6.; A(i,i+1) = dt/6.; } A(0,0) = 1.; A(0, Np1-1) = 1.; A(Np1-1, 0) = -2.*dt/6.; A(Np1-1, 1) = -1.*dt/6.; A(Np1-1, Np1-2) = 1*dt/6.; A(Np1-1, Np1-1) = 2*dt/6.; the red lines will make the matrix looks like // 6 6 // 1 4 1 // 1 4 1 // A = ... // // 1 4 1 // -2 *-1* *1* 2 Is the comment correct or the code correct? Any reference for this algorithm? Thank you, Kuang-Shing Chen

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Question about CONSERVED_QUANTUMNUMBERS in DMRG code
by Rafał 18 Nov '13

18 Nov '13

Dear all ALPS users, I have following questions to the DMRG tutorials. Why there is N in a line: 'CONSERVED_QUANTUMNUMBERS' : 'N,Sz', I understand that Sz stands for conserved quantum number but spin model on the open chain lattice does not have quantum number called N. Is this N added to 'CONSERVED_QUANTUMNUMBERS' just in case someone may use some bosonic model? Bests, Rafał

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poor performance of DMRG on Ising chain
by Emanuele Levi 15 Nov '13

15 Nov '13

Dear ALPS users, I am checking the performance of the DMRG application of ALPS on a simple Ising chain with periodic boundary conditions. The program seems not to be able to converge to the right ground state, even for lengths of the chain such as L=6,8,.. Comparing to the results of the sparsdiag algorithm included in the package the ground state energies are very different. Does anyone know why it is so? Any idea on how to overcome this problem? Thank you in advance. -- Dr Emanuele Levi emanuele.levi(a)gmail.com

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compile alps on cray xc30 machine
by Jia Chen 15 Nov '13

15 Nov '13

Hello, I am new to alps. Now I am trying to compile the code on a cray xc30 machine. Following the procedure on website. But when I compile by make, I always get error message "/usr/bin/ld: attempted static link of dynamic object `../src/alps/libalps.so.2.2.b1' make[2]: *** [tool/archive] Error 1" I hope some one here has experience of dealing with this type of problem and can help me out here. Regards -- Jia Chen

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Saving one parameter / Observables in Python
by Peter Bröcker 11 Nov '13

11 Nov '13

Good morning, I have two questions that I could not find an answer to. In my simulation, I would like to save one or more parameter that I adjust while it's running. This parameter is not an observable, but I could of course pretend that it is and save only one value. I am wondering though if there is not a more elegant way to handle this. My other question is related to the analysis of data. I would like to know how many entries a given observable has. In my code, I use the RealObservable class and the count() function to find the number of measurements. What is the equivalent way of doing so in python? Thank you very much in advance and best regards, Peter

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s-wave pair field correlation function in fullED
by Vladimir Iglovikov 09 Nov '13

09 Nov '13

[1] I am trying to compute s-wave pair field correlation function, using full diagonalization routine for the fermionic Hubbard model. This function is defined as: P_s = \langle \Delta^{\dagger} \Delta + \Delta \Delta^{\dagger} \rangle, where \Delta^{\dagger} = \frac {1} {\sqrt{N}} \sum_{k} c^{\dagger}_{n \uparrow} c^{\dagger}_{n \downarrow} And I can not figure out how to measure this. [2] How do I measure Kinetic energy? When I am trying use: 'MEASURE_AVERAGE[kinetic-energy]' : 'fermion_kinetic_energy' I get error: Cannot evaluate expression 0.333333 * fermion_kinetic_energy(i) Here is my model definition: ------------------------------ <MODELS> <SITEBASIS name="fermion"> <QUANTUMNUMBER name="Nup" min="0" max="1" type="fermionic"/> <QUANTUMNUMBER name="Ndown" min="0" max="1" type="fermionic"/> <OPERATOR name="Splus" matrixelement="1"> <CHANGE quantumnumber="Ndown" change="-1"/> <CHANGE quantumnumber="Nup" change="1"/> </OPERATOR> <OPERATOR name="Sminus" matrixelement="1"> <CHANGE quantumnumber="Nup" change="-1"/> <CHANGE quantumnumber="Ndown" change="+1"/> </OPERATOR> <OPERATOR name="Sz" matrixelement="(Nup-Ndown)/2"/> <OPERATOR name="Nup" matrixelement="Nup"/> <OPERATOR name="Ndown" matrixelement="Ndown"/> <OPERATOR name="N" matrixelement="Nup+Ndown"/> <OPERATOR name="c_down" matrixelement="1"> <CHANGE quantumnumber="Ndown" change="-1"/> </OPERATOR> <OPERATOR name="cdag_down" matrixelement="1"> <CHANGE quantumnumber="Ndown" change="1"/> </OPERATOR> <OPERATOR name="c_up" matrixelement="1"> <CHANGE quantumnumber="Nup" change="-1"/> </OPERATOR> <OPERATOR name="cdag_up" matrixelement="1"> <CHANGE quantumnumber="Nup" change="1"/> </OPERATOR> <OPERATOR name="n" matrixelement="Nup+Ndown"/> <OPERATOR name="n_up" matrixelement="Nup"/> <OPERATOR name="n_down" matrixelement="Ndown"/> <OPERATOR name="double_occupancy" matrixelement="Nup*Ndown"/> </SITEBASIS> <BONDOPERATOR name="fermion_hop" source="x" target="y"> cdag_up(x)*c_up(y)+cdag_up(y)*c_up(x)+cdag_down(x)*c_down(y)+cdag_down(y)*c_down(x) </BONDOPERATOR> <GLOBALOPERATOR name="fermion_kinetic_energy"> <BONDTERM type="0" source="i" target="j"> -t*fermion_hop(i,j) </BONDTERM> </GLOBALOPERATOR> <BASIS name="fermion"> <SITEBASIS type="1" ref="fermion"/> <SITEBASIS type="2" ref="fermion"/> <SITEBASIS type="3" ref="fermion"/> <CONSTRAINT quantumnumber="Nup" value="Nup_total"/> <CONSTRAINT quantumnumber="Ndown" value="Ndown_total"/> <CONSTRAINT quantumnumber="N" value="N_total"/> <CONSTRAINT quantumnumber="Sz" value="Sz_total"/> </BASIS> <HAMILTONIAN name="fermionic Hubbard"> <PARAMETER name="mu" default="0"/> <PARAMETER name="t" default="1"/> <PARAMETER name="U" default="0"/> <BASIS ref="fermion"/> <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> <PARAMETER name="U#" default="U"/> +U# * (n_up(i) - 0.5) * (n_down(i) - 0.5) - mu# * n(i) </SITETERM> <BONDTERM source="i" target="j"> -t*fermion_hop(i, j) </BONDTERM> </HAMILTONIAN> </MODELS> ----------------------- Lattice definition: ----------------------- <LATTICES> <LATTICE name="square" dimension="2"> <PARAMETER name="a" default="1"/> <BASIS> <VECTOR> a 0 </VECTOR> <VECTOR> 0 a </VECTOR> </BASIS> <RECIPROCALBASIS> <VECTOR>2*pi/a 0</VECTOR> <VECTOR>0 2*pi/a</VECTOR> </RECIPROCALBASIS> </LATTICE> <UNITCELL name="Lieb" dimension="2"> <VERTEX id="1" type="1"> <COORDINATE>0 0</COORDINATE> </VERTEX> <VERTEX id="2" type="2"> <COORDINATE>0.5 0</COORDINATE> </VERTEX> <VERTEX id="3" type="3"> <COORDINATE>0 0.5</COORDINATE> </VERTEX> <EDGE> <SOURCE vertex="1" offset="0 0"/> <TARGET vertex="2" offset="0 0"/> </EDGE> <EDGE> <SOURCE vertex="1" offset="0 0"/> <TARGET vertex="3" offset="0 0"/> </EDGE> <EDGE> <SOURCE vertex="1" offset="1 0"/> <TARGET vertex="2" offset="0 0"/> </EDGE> <EDGE> <SOURCE vertex="1" offset="0 1"/> <TARGET vertex="3" offset="0 0"/> </EDGE> </UNITCELL> <LATTICEGRAPH name="Lieb" vt_skip="true"> <FINITELATTICE> <LATTICE ref="square"/> <EXTENT dimension="1" size="nx"/> <EXTENT dimension="2" size="ny"/> <BOUNDARY type="periodic" /> </FINITELATTICE> <UNITCELL ref="Lieb"/> </LATTICEGRAPH> </LATTICES>

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