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Calculation of Entropy
by Forwordom 15 Nov '12

15 Nov '12

Hi, ALPS users and developers I have two questions about calculation of entropy by using DMRG: (1)If I can calculate the entropy of system by DMRG and how to get final entropy data besides standard output in the screen? (2)What dependence of entropy on system's properties ? In other words if it is depend on gapped or gapless ,chain or quasi-1D system. I would be very grateful for your responce.

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Brains Chen wants to share new pictures with you
by Brains Chen 06 Nov '12

06 Nov '12

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Brains Chen wants to share new pictures with you
by Brains Chen 06 Nov '12

06 Nov '12

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Alps-user
by konefvitbka53＠gmail.com 02 Nov '12

02 Nov '12

Hi all, whether it is possible to calculate in algorithms of worm and sse model with two-particle transfer, and calculate stiffness.

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Maybe "honeycomb" definition is wrong in lattice lib (lattices.xml)
by kaveh edalat 01 Nov '12

01 Nov '12

Dear All I like to make a graphene bilayer. I wanted to use "honeycomb" definition in the lattice library but I found something strange! The strange thing is the definition of vertexes: <UNITCELL name="honeycomb" dimension="2"> <VERTEX><COORDINATE>0 0</COORDINATE></VERTEX> <VERTEX><COORDINATE>-0.288665771484375 0.5773468017578125</COORDINATE></VERTEX> ....... ...... </UNITCELL> I don't know how these two numbers "-0.288665771484375 0.5773468017578125" were generated ( they are near to "-1/(2*sqrt(3)), 1/sqrt(3)" !) I think if we suppose the vertex coordinate is defined according to the lattice vectors (.i.e. a1=[1 0], a2=[1/2 sqrt(3)/2]), then the correct numbers should be: "-1/3, 2/3" (-1/3*a1+2/3*a2). So the correct "UNITCELL" should be: <UNITCELL name="honeycomb" dimension="2"> <VERTEX><COORDINATE>0 0</COORDINATE></VERTEX> <VERTEX><COORDINATE>-1/3 2/3</COORDINATE></VERTEX> ....... ...... </UNITCELL> I checked the new "UNITCELL", and I found the lattice is more like to graphene. If I am wrong please correct me. Thanks Kaveh Edalat

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Edit Complex number
by Forwordom 30 Oct '12

30 Oct '12

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How can we visualize a lattice in ALPS?
by kaveh edalat 30 Oct '12

30 Oct '12

Dear All I want to make a new lattice, but before serious calculation, I like to see the lattice. I searched in the alps mailing list and I found that probably "lattice-preview" should be a tool for visualization of lattices in ALPS. But I have two problem: first, when simply I type "lattice-preview" in the terminal I receive the following error: /opt/alps/bin/lattice-preview: 30: /opt/alps/lib/python/alps/preview.py: Permission denied Is there anyone to know why I receive the error? second, If we suppose the "lattice-preview" works well, what is the input file for this program? thanks in advanced Kaveh Edalat

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Covariance matrix of RealVectorObservable
by Giuseppe Carleo 29 Oct '12

29 Oct '12

Dear all, I have got a question about the calculation of the covariance matrix of a vector observable (RealVectorObservable type, for example): Indeed I am able to compute the (jacknife-corrected) simple covariance of two given scalar observables in this simple way --------------- string filename = "simulation.task1.out.h5"; mcdata<double> obs1; mcdata<double> obs2; obs1.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable1")); obs2.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable2")); cout << "Covariance: " << obs1.covariance(obs2) << "\n\n"; --------------- However it is not entirely clear to me how to proceed when one instead has a single vector observable recorded in the hdf5 file and wants to compute to covariance matrix of its entries. In that case mcdata cannot be used any longer and digging into the code source I did not manage to find a method "covariance" implemented for other than mcdata-like scalar observables. Is there a handy solution already implemented for that? Thank you in advance! Regards, Giuseppe

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 79, Issue 6
by Forwordom 29 Oct '12

29 Oct '12

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Edit Complex number
by Forwordom 28 Oct '12

28 Oct '12

Hi alps users and developers I want to simulate a lattice phase transition in external magnetic along x,y,z direction by using dmrg.I have to couple site operator with external magnetic field. But how to edit a complex number in the ALPS models.xml to get site operator Sy=1/2i(Splus-Sminus). Thanks in advance for your reply.

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