How to get the conserved quantities of a integrable quantum system?

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Discussion Overview

The discussion revolves around methods for calculating conserved quantities in integrable quantum many-body models. Participants explore theoretical frameworks, particularly in the context of spin chains, and seek resources for further understanding.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Homework-related

Main Points Raised

  • One participant inquires about methods to calculate conserved quantities in integrable quantum systems and requests book recommendations.
  • Another participant recommends a book on integrable models, noting that for spin chains, conserved quantities can be derived from the trace of the monodromy matrix, leading to a transfer matrix that generates commuting charges.
  • The same participant explains that in a one-dimensional spin chain with SU(2) symmetry, the transfer matrix yields L-1 conserved quantities, with the Hamiltonian being one of them.
  • A later reply expresses gratitude for the explanation but indicates a lack of full understanding of the concepts, particularly the group theory aspects, while showing interest in the theory discussed.
  • Further inquiry is made about the conserved quantities in the Ising model and their expression using Pauli matrices.

Areas of Agreement / Disagreement

Participants generally agree on the relevance of the discussed book and the methods for deriving conserved quantities in spin chains, but there is no consensus on the specifics of the Ising model or its representation.

Contextual Notes

The discussion includes assumptions about familiarity with advanced concepts in quantum mechanics and group theory, which may not be universally understood by all participants.

Billy Yang
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If I have an arbitrary quantum many-body model, what is the method to calculate the the conserved quantities if the model is integrable. If it is hard to explain, can you recommend some relevant books for me? Thanks a lot!
 
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This book discusses lots of different types of integrable models, both classical and quantum. As far as I'm aware this is the best intro book.

http://www.cambridge.org/ie/academi...e-scattering-method-and-correlation-functions

Now, it's really only spin chains I'm familiar with, but in this case the conserved quantities are given by taking the trace of the monodromy matrix on the auxiliary space. This defines the transfer matrix which generates a tower of commuting charges, one of which the is the Hamiltonian of the system. The one-dimensional spin chain with L sites and SU(2) symmetry has L degrees of freedom, whereas the transfer matrix only gives you L-1 conserved quantities. By adding a component of spin, say ##S^z##, we obtain the full set of commuting charges, and the system is integrable.
 
Dear Maybe_Memorie:
Thanks for your elaborate response and it really helps me a lot, although I can't fully understand the concepts you mentioned. But I am interested in the theory you introduced, especially its group theory parts. Thanks again!
Billy
 
Maybe_Memorie said:
This book discusses lots of different types of integrable models, both classical and quantum. As far as I'm aware this is the best intro book.

http://www.cambridge.org/ie/academi...e-scattering-method-and-correlation-functions

Now, it's really only spin chains I'm familiar with, but in this case the conserved quantities are given by taking the trace of the monodromy matrix on the auxiliary space. This defines the transfer matrix which generates a tower of commuting charges, one of which the is the Hamiltonian of the system. The one-dimensional spin chain with L sites and SU(2) symmetry has L degrees of freedom, whereas the transfer matrix only gives you L-1 conserved quantities. By adding a component of spin, say ##S^z##, we obtain the full set of commuting charges, and the system is integrable.
Maybe_Memorie:
Could you please tell me what the conserved quantities are in an ising model and how to express it using Pauli matrix? I am especially interested in this.

Billy
 

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