Abstract

It has recently been proven that in rank three tensor models, the antisymmetric and symmetric traceless sectors both support a large N expansion dominated by melon diagrams [1]. We show how to extend these results to the last irreducible O(N) tensor representation available in this context, which carries a two-dimensional representation of the symmetric group S3. Along the way, we emphasize the role of the irreducibility condition: it prevents the generation of vector modes which are not compatible with the large N scaling of the tensor interaction. This example supports the conjecture that a melonic large N limit should exist more generally for higher rank tensor models, provided that they are appropriately restricted to an irreducible subspace.

Highlights

  • Some properties of the celebrated SYK models [27,28,29,30] in the familiar context of large N quantum mechanics

  • It has recently been proven that in rank three tensor models, the antisymmetric and symmetric traceless sectors both support a large N expansion dominated by melon diagrams [1]

  • We emphasize the role of the irreducibility condition: it prevents the generation of vector modes which are not compatible with the large N scaling of the tensor interaction. This example supports the conjecture that a melonic large N limit should exist more generally for higher rank tensor models, provided that they are appropriately restricted to an irreducible subspace

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Summary

Rank-3 tensor models with complete interaction

We consider a bosonic theory in zero dimension with O(N ) global symmetry. The degrees of freedom are organized into a real rank-3 tensor Ta1a2a3 transforming as a product of three fundamental representations:. As standard in the literature, we will represent the interaction kernel as an ordinary fourvalent vertex, or as a stranded diagram — as shown in figure 1. Is the complete graph on four vertices, we propose to call such an interaction a complete interaction.5 By this definition, there exists other complete interactions (for instance the O(N )3-invariant interaction of [9]) that one might want to include in the action. There exists other complete interactions (for instance the O(N )3-invariant interaction of [9]) that one might want to include in the action They all become equivalent upon reduction to a tensor in a fixed irreducible representation of S3, so it is sufficient for our purpose to consider only one such interaction

Vector modes and trace instability
Irreducible tensors
Tensor model with mixed permutation symmetry
Feynman expansion and amplitudes
Feynman maps
Stranded graphs
General form of a two-point function
Tadpole maps
Elementary melon maps
Melon-tadpole two-point function
Existence of the large N expansion
Dominance of melon diagrams
Conclusion
Full Text
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