CMBAnisotropies and Inflation fromNon-Standard Spinors

The apparent alignment of the cosmic microwave background multipoles on large scales challenges the standard cosmological model. Scalar field inflation is isotropic and cannot account for the observed alignment. We explore the imprints, a non-standard spinor driven inflation would leave on the cosmic microwave background anisotropies. We show it is natural to expect an anisotropic inflationary expansion of the Universe which has the effect of suppressing the low multipole amplitude of the primordial power spectrum, while at the same time to provide the usual inflationary features. Inflation is a successful theory to explain many cosmological puzzles. However, one does not really know what has driven it, since it most probably occurred near the scale of grand unification, hence far beyond the standard model of particle physics. In this letter we study the possibility of non-standard spinors to drive inflation and investigate the possible imprints of such spinors on the Cosmic Microwave Background (CMB) anisotropies. In fact, we consider the possibility that such an effect has already been detected, in the form of the Axis of Evil: an apparent alignment of the CMB multipoles on very large scales [1,2,3]. While a scalar field driven inflationary epoch is naturally isotropic, an anisotropic expansion might occur within a more complex model. This may lead to the existence of a preferred direction in the primordial power spectrum. Although the statistical significance of such preferred direction is hard to quantify, a variety of models have been put forward to explain this phenomenon [4,5,6,7,8,9,10,11,12]. These are motivated since the large scale anisotropy claimed by [13] in the CMB quadrupole and octupole seems to be present at several cosmological scales and observations. In particular the quadrupole and octupole seem also to align Email addresses: [email protected] (Christian G. Böhmer), [email protected] (David F. Mota). with the dipole [14]. Recently, there are claims that such alignment even extends to higher multipoles [15]. Furthermore, the polarization of radio galaxies and the optical polarizations of quasars also indicate a preferred direction pointing at the same direction [16]. Finally, there are several indications from the SDSS data that deviations from isotropy and homogeneity are also present at cluster and galactic scales [17]. Hence, there is an entire set of observations that disfavor isotropy at high confidence level. As for the non-standard Wigner class spinors, we consider a spin one half matter field with mass dimension one, named elko spinors [18]. These spinors are based on the eigenspinors of the charge conjugation operator. The resulting field theory has the unusual property (CPT ) = −I [35]. This particular model belongs to a wider class of so-called flagpole spinors [19]. The spinors have mass dimension one and therefore the only power counting renormalizable interactions of this field with standard matter take place through the Higgs doublet or with gravity [18]. Consider the lefthanded part φL of Dirac spinor ψ in Weyl representation, then an elko spinor is defined by [18]