Abstract

We establish an all-loop conformal Yangian symmetry for the full set of planar amplitudes in the recently proposed integrable bi-scalar field theory in four dimensions. This chiral theory is a particular double scaling limit of γ-twisted weakly coupled mathcal{N}=4 SYM theory. Each amplitude with a certain order of scalar particles is given by a single fishnet Feynman graph of disc topology cut out of a regular square lattice. The Yangian can be realized by the action of a product of Lax operators with a specific sequence of inhomogeneity parameters on the boundary of the disc. Based on this observation, the Yangian generators of level one for generic bi-scalar amplitudes are explicitly constructed. Finally, we comment on the relation to the dual conformal symmetry of these scattering amplitudes.

Highlights

  • For their computation, a few very promising ideas have been proposed, such as the pentagon OPE of [10] for instance

  • The Yangian symmetry has been well established as a symmetry of tree-level scattering amplitudes, but its generalization to higher loop orders is hindered by IR singularities which, being regularized, destroy this symmetry [13, 14]

  • As we will show in this paper, an all-loop Yangian symmetry can be constructed for the case of scalar amplitudes within the recently proposed, by one of the authors and O

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Summary

Yangian invariants and monodromy matrix

We briefly review the construction of Yangian invariants before specifying it to the case of the conformal algebra so(2, 4). The algebra given by the RTT-relation possesses a comultiplication structure This means that the matrix product of several Lax operators (each acting on its own spin chain site) respects (2.1). As was shown in [26, 27], the eigenvalue problem for an inhomogeneous monodromy constructed out of Lax operators, i.e. provides a natural way to obtain Yangian invariants |λ; inv , which live on n sites of a noncompact spin chain. Provides a natural way to obtain Yangian invariants |λ; inv , which live on n sites of a noncompact spin chain Both sides of eq (2.4) are matrices and 1 denotes the identity matrix. In this case xμi are the usual position space coordinates

Conformal Lax operator
Yangian symmetry of bi-scalar fishnet graphs: regular boundary
Cross integral
Double-cross integral
Multiloop integrals
Yangian symmetry of bi-scalar fishnet graphs: irregular boundary
Scattering amplitudes and cuts of fishnet graphs
Fishnet graphs and first realization of the Yangian
First realization
Pedagogic examples: cross and double cross
Monodromy expansion
Dual conformal symmetry and the Yangian in momentum space
10 Discussion and outlook
A Cyclicity
B Expansion of monodromy eigenvalue
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