Buryak–Rossi–Shadrin bihamiltonian conjecture for the DR hierarchy

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Let VV be the state space of a homogeneous cohomological field theory with homogeneous basis e1,…,eNe_1,\ldots,e_N, metric (ηαβ)(\eta^{\alpha\beta}), degrees deg⁡eα=qα\deg e_\alpha=q_\alpha, and parameters rγr^\gamma defined by r‾=rγeγ\overline r=r^\gamma e_\gamma. Set

μ=diag⁡(μ1,…,μN),μα=qα−δ2,\mu=\operatorname{diag}(\mu_1,\ldots,\mu_N),\qquad \mu_\alpha=q_\alpha-\frac{\delta}{2},

and let KDRK^\mathrm{DR} be the matrix differential operator defined from the DR hierarchy. Define

Aαβ:=ηβνc0,3(eν⊗eα⊗r‾).A^\beta_\alpha:=\eta^{\beta\nu}c_{0,3}(e_\nu\otimes e_\alpha\otimes\overline r).

For the DR Hamiltonians g‾α,d\overline g_{\alpha,d}, let {⋅,⋅}KDR\{\cdot,\cdot\}_{K^\mathrm{DR}} and {⋅,⋅}η−1∂x\{\cdot,\cdot\}_{\eta^{-1}\partial_x} denote the brackets induced by KDRK^\mathrm{DR} and the first Poisson operator η−1∂x\eta^{-1}\partial_x, respectively.

Buryak–Rossi–Shadrin's conjecture. The operator KDRK^\mathrm{DR} is Poisson and compatible with η−1∂x\eta^{-1}\partial_x. It endows the DR hierarchy with a bihamiltonian structure satisfying

{⋅,g‾α,d}KDR=(d+32+μα){⋅,g‾α,d+1}η−1∂x+Aαβ{⋅,g‾β,d}η−1∂x,d≥−1.\left\{\cdot,\overline g_{\alpha,d}\right\}_{K^\mathrm{DR}}=\left(d+\frac{3}{2}+\mu_\alpha\right)\left\{\cdot,\overline g_{\alpha,d+1}\right\}_{\eta^{-1}\partial_x}+A^\beta_\alpha\left\{\cdot,\overline g_{\beta,d}\right\}_{\eta^{-1}\partial_x},\qquad d\geq -1.

This conjecture proposes a second compatible Poisson structure for the DR hierarchy, making it bihamiltonian and providing a recursion among its Hamiltonian flows. The supplied text does not state whether it has been proved or disproved.

References

Primary source

Alexandr Buryak and Paolo Rossi, “Bihamiltonian structure of the DR hierarchy in the semisimple case”, arXiv:2408.12397 (2025).

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