Non-standard Dirac adjoint spinor: The emergence of a new dual

In this present communication we provide a new derivation of the Dirac dual structure by employing a different approach from the originally proposed. Following a general and rigorous mathematical process to compute the dual structure, we investigate if is possible to break the existing "rigidity" in its primordial formulation. For this task, firstly, we look towards to understand the core of the Dirac spinors construction and then, we suggest to built an alternative dual structure for the Dirac spinor, which preserve an invariant norm under any $SL(2,\mathcal{C})$ transformation. Finally, we verify if the prominent physical contents are maintained or if it is affected by such construction.Comment: 7 pages, 0 figure

A-term inflation and the MSSM

The parameter space for A-term inflation is explored with $W=\lambda_p \phi^p/(p M_P^{p-3})$. With p=6 and \lambda_p~1, the observed spectrum and spectral tilt can be obtained with soft mass of order 10^2 GeV but not with a much higher mass. The case p=3 requires \lambda_p~10^{-9} to 10^{-12}. The ratio m/A requires fine-tuning, which may be justified on environmental grounds. An extension of the MSSM to include non-renormalizable terms and/or Dirac neutrino masses might support either A-term inflation or modular inflation.Comment: 10 pages, 3 figures; Comments added, typos correcte

Type-4 spinors: transmuting from Elko to single-helicity spinors

In this communication we briefly report an unexpected theoretical discovery which emerge from the mapping of Elko mass-dimension-one spinors into single helicity spinors. Such procedure unveils a class of spinor which is classified as type-4 spinor field within Lounesto classification. In this paper we explore the underlying physical and mathematical contents of the type-4 spinor.Comment: 9 pages, 0 figure

Topological Quintessence

A global monopole (or other topological defect) formed during a recent phase transition with core size comparable to the present Hubble scale, could induce the observed accelerating expansion of the universe. In such a model, topological considerations trap the scalar field close to a local maximum of its potential in a cosmologically large region of space. We perform detailed numerical simulations of such an inhomogeneous dark energy system (topological quintessence) minimally coupled to gravity, in a flat background of initially homogeneous matter. We find that when the energy density of the field in the monopole core starts dominating the background density, the spacetime in the core starts to accelerate its expansion in accordance to a \Lambda CDM model with an effective inhomogeneous spherical dark energy density parameter \Omega_\Lambda(r). The matter density profile is found to respond to the global monopole profile via an anti-correlation (matter underdensity in the monopole core). Away from the monopole core, the spacetime is effectively Einstein-deSitter (\Omega_\Lambda(r_{out}) -> 0) while at the center \Omega_\Lambda(r ~ 0) is maximum. We fit the numerically obtained expansion rate at the monopole core to the Union2 data and show that the quality of fit is almost identical to that of \Lambda CDM. Finally, we discuss potential observational signatures of this class of inhomogeneous dark energy models.Comment: Accepted in Phys. Rev. D (to appear). Added observational bounds on parameters. 10 pages (two column revtex), 6 figures. The Mathematica files used to produce the figures of this study may be downloaded from http://leandros.physics.uoi.gr/topquin

Polynomial Approximants for the Calculation of Polarization Profiles in the \ion{He}{1} 10830 \AA Multiplet

The \ion{He}{1} multiplet at 10830 \AA is formed in the incomplete Paschen-Back regime for typical conditions found in solar and stellar atmospheres. The positions and strengths of the various components that form the Zeeman structure of this multiplet in the Paschen-Back regime are approximated here by polynomials. The fitting errors are smaller than $\sim10^{-2}$ m\AA in the component positions and $\sim10^{-3}$ in the relative strengths. The approximant polynomials allow for a very fast implementation of the incomplete Paschen-Back regime in numerical codes for the synthesis and inversion of polarization profiles in this important multiplet.Comment: ApJ Supplements (in press

Signatures of Incomplete Paschen-Back Splitting in the Polarization Profiles of the He I 10830 multiplet

We investigate the formation of polarization profiles induced by a magnetic field in the He I multiplet at 1083,0 nm . Our analysis considers the Zeeman splitting in the incomplete Paschen-Back regime. The effects turn out to be important and produce measurable signatures on the profiles, even for fields significantly weaker than the level-crossing field ($\sim$400 G). When compared to profiles calculated with the usual linear Zeeman effect, the incomplete Paschen-Back profiles exhibit the following conspicuous differences: a) a non-Doppler blueshift of the Stokes V zero-crossing wavelength of the blue component; b) area and peak asymmetries, even in the absence of velocity and magnetic gradients; c) a $\sim$25% reduction in the amplitude of the red component. These features do not vanish in the weak field limit. The spectral signatures that we analyze in this paper may be found in previous observations published in the literature.Comment: Accepted for publication in The Astrophysical Journa