Standard-form classification conjecture for tau-symmetric RH perturbations

Let a τ\tau-symmetric Hamiltonian perturbation of the Riemann--Hopf hierarchy be written in generalized standard form, with first Hamiltonian

H~1=(w36ϵ2a024w12+k4ϵkμPk,l(μ)2μ1=μ2,m1(μ)=0αμwμ)dx.\widetilde{H}_1=\int\left(\frac{w^3}{6}-\epsilon^2\frac{a_0}{24}w_1^2+\sum_{k\geq 4}\epsilon^k\sum_{\substack{\mu\in\mathcal{P}_k,\,l(\mu)\geq 2\\ \mu_1=\mu_2,\,m_1(\mu)=0}}\alpha_\mu w_\mu\right)dx.

Here Pk\mathcal{P}_k denotes the set of partitions of kk, l(μ)l(\mu) their length, m1(μ)m_1(\mu) the multiplicity of 11, and wμ:=iwμiw_\mu:=\prod_i w_{\mu_i}. Standard-form classification conjecture. If a0=0a_0=0, then αμ=0\alpha_\mu=0 for all μ\mu. If a00a_0\neq0, then a0,α(22),α(23),a_0,\alpha_{(2^2)},\alpha_{(2^3)},\ldots uniquely determine all other αμ\alpha_\mu, all αμ\alpha_\mu vanish when μ|\mu| is odd, and arbitrary values of a0Ca_0\in\mathbb{C}^* and α(22),α(23),C\alpha_{(2^2)},\alpha_{(2^3)},\ldots\in\mathbb{C} are allowed. The supplied text gives this as a conjectural statement, with no resolution evidence.

Sources & referencesView supporting material

Primary source

Alexandr Buryak, Jianghao Xu and Di Yang, “Bihamiltonian tests for integrable systems associated to rank-1 F-CohFTs”, arXiv:2601.13203 (2026).

Additional references

2 papers in this index state this conjecture (2016–2026). The statement above is taken from the most recent of them; the others are arXiv:1609.04059.

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