New multisymplectic approach to the Metric-Affine (Einstein-Palatini) action for gravity

TL;DR

This paper develops a covariant multisymplectic framework for the Einstein-Palatini gravity model, addressing its constraints and gauge symmetries, and establishing its equivalence with the Einstein-Hilbert formulation.

Contribution

It introduces a novel multisymplectic approach to the Metric-Affine action for gravity, including a detailed analysis of constraints and gauge symmetries.

Findings

Derived the covariant field equations using integrable distributions.

Constructed the multimomentum Hamiltonian formalism for the model.

Established the equivalence with the Einstein-Hilbert formulation.

Abstract

We present a covariant multisymplectic formulation for the Einstein-Palatini (or Metric-Affine) model of General Relativity (without energy-matter sources). As it is described by a first-order affine Lagrangian (in the derivatives of the fields), it is singular and, hence, this is a gauge field theory with constraints. These constraints are obtained after applying a constraint algorithm to the field equations, both in the Lagrangian and the Hamiltonian formalisms. In order to do this, the covariant field equations must be written in a suitable geometrical way, using integrable distributions which are represented by multivector fields of a certain type. We obtain and explain the geometrical and physical meaning of the Lagrangian constraints and we construct the multimomentum (covariant) Hamiltonian formalism. The gauge symmetries of the model are discussed in both formalisms and, from them, the equivalence with the Einstein-Hilbert model is established.