<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Note that by default mps_evolve only works for nearest neighbors lattices.</div><div class="">In higher dimensions this is not the case, since the lattice is unrolled into a one dimensional chain with longer range interactions.</div><div class=""><br class=""></div><div class="">We have a second flavor of the time evolution algorithm for these cases, you can use it via the parameter:</div><div class="">te_type=mpo</div><div class="">Quite some improvements to this variant was introduced in ALPS 2.3, so I suggest you to use that version.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Best,</div><div class="">Michele</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On 8 Jul 2017, at 00:11, H <<a href="mailto:w.boson@gmail.com" class="">w.boson@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Dear <span style="font-size:12.8px" class="">Michele,</span><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">I am in strong need of simulating the dynamics of higher dimensional but small systems.</span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">I tried use mps_evolve on a trivial 2D system, but I cannot get it to work.</span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">I put a particle on the corner of a LxW lattice, and measure <n> at its neighbor site as a function of time. </span></div><div class=""><span style="font-size:12.8px" class="">The matlab code and the python (alps) codes are attached.</span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">When L=3, W=1, for 1D system, they agree quite well:</span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class=""><span id="cid:ii_15d1f16277de8c99"><1D.jpg></span><span id="cid:ii_15d1f16672089d0e"><image.png></span><br class=""></span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">When L=W=3, they are completely different (left is the correct result from matlab):</span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class=""><span id="cid:ii_15d1f17554f5c8c1"><2D.jpg></span><span id="cid:ii_15d1f185696a351e"><image.png></span><br class=""></span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class="">Is there something I am missing? I think I have installed the newest version:</span></div><div class=""><span style="font-variant-ligatures:no-common-ligatures;font-family:Menlo;font-size:11px" class="">ALPS/MPS Time Evolution version MAQUIS repo r4143 (2013-2014)</span></div>
<div class=""><span style="font-size:12.8px" class=""><br class=""></span></div><div class=""><span style="font-size:12.8px" class=""><br class=""></span></div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Thu, Jul 6, 2017 at 2:37 PM, Michele Dolfi <span dir="ltr" class=""><<a href="mailto:dolfim@phys.ethz.ch" target="_blank" class="">dolfim@phys.ethz.ch</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Hello,<div class=""><br class=""></div><div class="">Yes, the code can handle 2d systems.</div><div class="">Yes, to use it you just have to specify the lattice.</div><div class=""><br class=""></div><div class="">Which sizes do you want to run?</div><div class="">Unfortunately running higher dimensional DMRG simulations is a highly non trivial task.</div><div class="">Special care has to be taken for understanding the convergence with respect to the number of sweeps and the MPS bond dimension.</div><div class="">For an example on how to treat it for “just ladders”, you can have a look here: <a href="https://doi.org/10.1103/PhysRevB.92.195139" target="_blank" class="">https://doi.org/10.1103/<wbr class="">PhysRevB.92.195139</a></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Best regards,</div><div class="">Michele</div><div class=""><br class=""></div><div class=""><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class=""><div class="h5"><div class="">On 6 Jul 2017, at 06:32, H <<a href="mailto:w.boson@gmail.com" target="_blank" class="">w.boson@gmail.com</a>> wrote:</div><br class="m_-2533389208021014861Apple-interchange-newline"></div></div><div class=""><div class=""><div class="h5"><div dir="ltr" class="">Dear Michele or others,<div class=""><br class=""></div><div class="">In your paper (arXiv:1407.0872)'s abstract you mentioned the MPS code can handle 2D system. Is it as simple as setting the 'LATTICE' parameter to "open square lattice", or do I need to build a custom 1D lattice with long-range coupling?</div><div class=""><br class=""></div><div class="">I tried setting 'LATTICE' to "open square lattice" but the results seems different from my ED result. The system is spinful fermionic. Could it be due to fermion signs not properly taken care of internally?</div><div class=""><br class=""></div><div class="">Ultimately I need to simulate a small 3D system (3x3x3). Can I use the internal cubic lattice or do I need to build a custom 1D lattice with long-range coupling?</div></div>
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