Enhanced area law in the Widom-Sobolev formula for the free Dirac operator in arbitrary dimension

Abstract: We prove a logarithmically enhanced area law for all R\'enyi entanglement entropies of the ground state of a free gas of relativistic Dirac fermions. Such asymptotics occur in any dimension if the modulus of the Fermi energy is larger than the mass of the particles and in the massless case at Fermi energy zero in one space dimension. In all other cases of mass, Fermi energy and dimension, the entanglement entropy grows no faster than the area of the involved spatial region. The result is established for a general class of test functions which includes the ones corresponding to R\'enyi entropies and relies on a recently proved extension of the Widom-Sobolev formula to matrix-valued symbols by the authors.