Partition function for a mass dimension one fermionic field and the dark matter halo of galaxies

Abstract

This work study the finite temperature effects of a mass dimension one fermionic field, sometimes called Elko field. The equilibrium partition function was calculated by means of the imaginary time formalism and the result obtained was the same for a Dirac fermion field, even though the Elko field does not satisfy a Dirac like equation. The high and low temperature limits were obtained, and for the last case the degeneracy pressure due to Pauli exclusion principle can be responsible for the dark matter halos around galaxies to be greater than or of the same order of the galaxy radius. Also, for a light particle of about $0.1$eV and a density of just 0.1 particle per cubic centimeter, the value of the total dark matter mass due to Elko particles is of the same order of a typical galaxy. Such a result satisfactorily explains the dark matter as being formed just by Elko fermionic particles and also the existence of galactic halos that go beyond the observable limit.