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<p>It wasn't very hard to define such a quantum number, but it seems like it actually makes the simulation run much slower. I suppose this is because another quantum number needs to be stored which leads to a larger basis size again? On the other hand, I can
think of no way to properly define the spin operators without using the quantum numbers S, Sz... <br>
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<p>Many thanks,<br>
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<p>Axel<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>Från:</b> Comp-phys-alps-users <comp-phys-alps-users-bounces@lists.phys.ethz.ch> för Matthias Troyer <troyer@phys.ethz.ch><br>
<b>Skickat:</b> den 17 januari 2017 19:42<br>
<b>Till:</b> comp-phys-alps-users@lists.phys.ethz.ch<br>
<b>Ämne:</b> Re: [ALPS-users] Conserve quantum number for composite unit cell</font>
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<div>You need to define a new combined quantum number, which is changed by the training and lowering operators for both types of particles.
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<div class="">On 17 Jan 2017, at 08:54, Michele Dolfi <<a href="mailto:dolfim@phys.ethz.ch" class="">dolfim@phys.ethz.ch</a>> wrote:</div>
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<div class="" style="word-wrap:break-word">I hope somebody else could give you a better answer, but I don’t think this is possible out of the box, and I’m not 100% sure it is at all possible in the way you think about it.
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<div class="">What I would try is away to play around with a new model definition where you make a composite quantum number explicit.</div>
<div class="">The "fermion Hubbard” and “alternative fermion Hubbard” could be of inspiration for how to conserve N and/or Sz instead of Nup and/or Ndown.</div>
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<div class="">Best,</div>
<div class="">Michele</div>
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<div class="">On Jan 17, 2017, at 4:10 PM, Axel Gagge <<a href="mailto:axel.gagge@fysik.su.se" class="">axel.gagge@fysik.su.se</a>> wrote:</div>
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Hello, I just wanted to ask if it is possible to preserve a combination of quantum numbers such as the total number of excitations:<br class="">
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N = \sum_{bosonic sites} n_j + 1/2 \sum_{spinful sites} s_z<br class="">
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and what the syntax for this would be? I guess that one option would be to define a new quantum number and let Splus raise it by 1/2 but I just thought that I would check this with you first!<br class="">
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Otherwise, thank you for an excellent library! I have had no problems so far with the new release.<br class="">
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Thanks,<br class="">
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/Axel Gagge<br class="">
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First year PhD Student, Stockholm University<br class="">
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