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Critical spin chains and loop models with $U(n)$ symmetry
by Paul Roux, Jesper Lykke Jacobsen, Sylvain Ribault, Hubert Saleur
Submission summary
Authors (as registered SciPost users): | Sylvain Ribault · Paul Roux |
Submission information | |
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Preprint Link: | https://arxiv.org/abs/2404.01935v1 (pdf) |
Code repository: | https://gitlab.com/s.g.ribault/representation-theory.git |
Date submitted: | 2024-06-12 11:24 |
Submitted by: | Roux, Paul |
Submitted to: | SciPost Physics |
Ontological classification | |
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Academic field: | Physics |
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Approaches: | Theoretical, Computational |
Abstract
Starting with the Ising model, statistical models with global symmetries provide fruitful approaches to interesting physical systems, for example percolation or polymers. These include the $O(n)$ model (symmetry group $O(n)$) and the Potts model (symmetry group $S_Q$). Both models make sense for $n,Q\in \mathbb{C}$ and not just $n,Q\in \mathbb{N}$, and both give rise to a conformal field theory in the critical limit. Here, we study similar models based on the unitary group $U(n)$. We focus on the two-dimensional case, where the models can be described either as gases of non-intersecting orientable loops, or as alternating spin chains. This allows us to determine their spectra either by computing a twisted torus partition function, or by studying representations of the walled Brauer algebra. In the critical limit, our models give rise to a CFT with global $U(n)$ symmetry, which exists for any $n\in\mathbb{C}$. Its spectrum is similar to those of the $O(n)$ and Potts CFTs, but a bit simpler. We conjecture that the $O(n)$ CFT is a $\mathbb{Z}_2$ orbifold of the $U(n)$ CFT, where $\mathbb{Z}_2$ acts as complex conjugation.
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