Universal formula for the energy-momentum tensor via a flow equation in the Gross-Neveu model

For the fermion field in the two-dimensional Gross-Neveu model, we introduce a flow equation that allows a simple 1/N expansion. By employing the 1/N expansion, we examine the validity of a universal formula for the energy-momentum tensor which is based on the small flow-time expansion.We confirm that the formula reproduces a correct normalization and the conservation law of the energy-momentum tensor by computing the translation Ward-Takahashi relation in the leading non-trivial order in the 1/N expansion. Also, we confirmthat the expectation value at finite temperature correctly reproduces thermodynamic quantities. These observations support the validity of a similar construction of the energy-momentum tensor via the gradient/Wilson flow in lattice gauge theory.