Tree-level Scattering Amplitudes via Homotopy Transfer

Dec 14, 2023
72 pages
e-Print:
Report number:
  • HU-EP-23/67-RTG

Citations per year

202320242025041
Abstract: (arXiv)
We formalize the computation of tree-level scattering amplitudes in terms of the homotopy transfer of homotopy algebras, illustrating it with scalar ϕ3\phi^3 and Yang-Mills theory. The data of a (gauge) field theory with an action is encoded in a cyclic homotopy Lie or LL_{\infty} algebra defined on a chain complex including a space of fields. This LL_{\infty} structure can be transported, by means of homotopy transfer, to a smaller space that, in the massless case, consists of harmonic fields. The required homotopy maps are well-defined since we work with the space of finite sums of plane-wave solutions. The resulting LL_{\infty} brackets encode the tree-level scattering amplitudes and satisfy generalized Jacobi identities that imply the Ward identities. We further present a method to compute color-ordered scattering amplitudes for Yang-Mills theory, using that its LL_{\infty} algebra is the tensor product of the color Lie algebra with a homotopy commutative associative or CC_{\infty} algebra. The color-ordered scattering amplitudes are then obtained by homotopy transfer of CC_{\infty} algebras.
Note:
  • 72 pages, v2: introduction improved, references added
  • gauge field theory: Yang-Mills
  • algebra: Lie
  • homotopy
  • scattering amplitude
  • tree approximation
  • color
  • Jacobi identity
  • plane wave
  • cyclic
  • Ward identity
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