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Fusion rules and structure constants of E-series minimal models
by Rongvoram Nivesvivat, Sylvain Ribault
Submission summary
| Authors (as registered SciPost users): | Rongvoram Nivesvivat · Sylvain Ribault |
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| Preprint Link: | https://arxiv.org/abs/2502.14295v3 (pdf) |
| Date accepted: | May 15, 2025 |
| Date submitted: | May 8, 2025, 8:13 a.m. |
| Submitted by: | Rongvoram Nivesvivat |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
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| Approach: | Theoretical |
Abstract
In the ADE classification of Virasoro minimal models, the E-series is the sparsest: their central charges $c=1-6\frac{(p-q)^2}{pq}$ are not dense in the half-line $c\in (-\infty,1)$, due to $q=12,18,30$ taking only 3 values -- the Coxeter numbers of $E_6, E_7, E_8$. The E-series is also the least well understood, with few known results beyond the spectrum. Here, we use a semi-analytic bootstrap approach for numerically computing 4-point correlation functions. We deduce non-chiral fusion rules, i.e. which 3-point structure constants vanish. These vanishings can be explained by constraints from null vectors, interchiral symmetry, simple currents, extended symmetries, permutations, and parity, except in one case for $q=30$. We conjecture that structure constants are given by a universal expression built from the double Gamma function, times polynomial functions of $\cos(\pi\frac{p}{q})$ with values in $\mathbb{Q}\big(\cos(\frac{\pi}{q})\big)$, which we work out explicitly for $q=12$. We speculate on generalizing E-series minimal models to generic integer values of $q$, and recovering loop CFTs as $p,q\to \infty$.
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List of changes
Changes according to Jiaxin Qiao's report
- Our numerical bootstrap results imply that the E-series minimal models' spectra always yield a unique solution to the crossing-symmetry equation. Therefore, this allows us to uniquely factorize the 4-point structure constants into the 3-point structure constants up to some field renormalizations. (This uniqueness is a numerical result, we do not have a proof.)
We have added these details at the beginning of Section 4.1.
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We have corrected the parity of $s$ in last term of (1.5a) as suggested.
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The spectrum for the case $q =12$ is block-diagonal w.r.t to the Ising category whereas the spectrum for the case $q =30$ is block-diagonal w.r.t to the Lee-Yang category.
This has been clarified after equation (1.6).
- To obtain the PSU(n) CFT, we need to assume that the first Kac indices $r$ increases as $q$ is increased.
To make our speculation clearer, we have added the equations (1.11), (1.12), and (1.13), which speculate how to obtain the $PSU(n)$ CFT as the non-rational limit of generalizations of E-series minimal models.
- We have clarified that the non-chiral fusion rules of $V_{1,2}^d$ are not an assumption.
The non-chiral fusion rules of $V_{1,2}^d$ can be fully determined by using the constraints from the null vectors, the crossing-symmetry equation, and the single-valuedness. Then, the resulting non-chiral fusion rules of $V_{1,2}^d$ produce the primary fields that are allowed by the chiral fusion rules of $R_{1, 2}$.
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For computing the non-chiral fusion rules, the bootstrap uses the spectrum and the constraints from the null vectors (chiral fusion rules) as the only inputs. Then, we check that the resulting non-chiral fusion rules agree with the extended symmetries and the non-standard constraints in Section 2. For deducing the analytic structure constants, the inputs to the bootstrap are the non-chiral fusion rules, which reduce the number of unknowns in the crossing-symmetry equation and allow us to easily access numerical results at high-precision. All of the above has been clarified at the end of Section 1.4, after equation (1.18).
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See point 6.
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We have rewritten 2-point structure constants as simply structure constants since $c_{1, 2, 2}$ and $c_{1, 3, 3}$ on the table (4.9) are the structure constants of the three-point functions $<V_{1,s}V_{2,s'}V_{2,s''} $ and $<V_{1,s}V_{3,s'}V_{3,s''} $.
Changes according to Connor Behan's report
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We have added the reference for the three-point functions in the A- and D-series in the second point of the 4 items on page, citing as "reference [2] and references therein".
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On page 3, we have itemized why the E-series minimal models are not fully solved, and we have added reference [3], which discuss how to compute the models' three-point functions on a case-by-case basis.
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At the end of Section 2.3 we have stated more explicitly that a simple current can be interpreted as an extended $\mathbb{Z}_2$ symmetry, and that Section 2.4 deals with extended symmetries that are not simple currents.
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We have clarified this point.
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We have added equations (1.11), (1.12), and (1.13) to clarified our speculation on obtaining the $PSU(n)$ CFT as non-rational limits.
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On page 9, under the equation (2.7), we have clarified why we choose $r \leq q/2$ except for the case $q = 12$.
We make an exception for the case $q = 12$ because we want all three-point functions to obey our convention for the parity constraints for any $q$: any allowed even coupling also comes with an allowed odd coupling.
For $q = 12$, the case $r = 7$ belongs to the identity sector of the extended symmetry (1.6) whereas $r=5$ belongs to the $\epsilon$. This makes three-point functions for the case $q =12$ agree with our convention for the parity constraints.
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We have clarified that the convention for the parity $s1 + s2 + s3$ under the equation (2.11). For this parity, we use the notations (1.5) wherein the Kac indices $s_i$ are integers for both diagonal and non-diagonal fields.
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We have stressed that we write the superscript $e$ in the non-chiral fusion rules when both even and odd parities are allowed.
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We have explained after (4.3) why the structure constants on the table (4.9) only depends on the second indices through signs.
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We have corrected these typos.
Published as SciPost Phys. 18, 163 (2025)
