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Higgs effective potential in a perturbed Robertson-Walker background

Titulo: 
Higgs effective potential in a perturbed Robertson-Walker background
Autores: 
Maroto, AL; Prada, F
Resumen: 
We calculate the one-loop effective potential of a scalar field in a Robertson-Walker background with scalar metric perturbations. A complete set of orthonormal solutions of the perturbed equations is obtained by using the adiabatic approximation for comoving observers. After analyzing the problem of renormalization in inhomogeneous backgrounds, we get the explicit contribution of metric perturbations to the effective potential. We apply these results to the Standard Model Higgs field and evaluate the effects of metric perturbations on the Higgs mass and on its vacuum expectation value. Space-time variations are found, which are proportional to the gravitational slip parameter, with a typical amplitude of the order of Delta phi/phi similar or equal to 10(-11) on cosmological scales. We also discuss possible astrophysical signatures in the Solar System and in the Milky Way that could open new possibilities to explore the symmetry breaking sector of the electroweak interactions.
Autor principal: 
Maroto, AL
Autor/es del IAA: 
Prada, Francisco
DOI: 
10.1103/PhysRevD.90.123541
Revista: 
PHYSICAL REVIEW D
Fecha de publicación: 
2014/12/31
Volumen: 
90
Issue: 
12
Tipo de documento: 
Article
Número de artículo: 
123541

PPAK Wide field Integral Field Spectroscopy of NGC 628-III. Stellar population properties

Titulo: 
PPAK Wide field Integral Field Spectroscopy of NGC 628-III. Stellar population properties
Autores: 
Sanchez-Blazquez, P; Rosales-Ortega, F; Diaz, A; Sanchez, SF
Resumen: 
We present a stellar population analysis of the nearby, face-on, SA(s)c galaxy, NGC 628, which is part of the PPAK Integral Field Spectroscopy Nearby Galaxies Survey. The data cover a field of view of similar to 6 arcmin in diameter with a sampling of similar to 2.7 arcsec per spectrum and a wavelength range (3700-7000 angstrom). We apply spectral inversion methods to derive 2D maps of star formation histories and chemical enrichment. We present maps of the mean (luminosity- and mass-weighted) age and metallicity that reveal the presence of structures such as a nuclear ring, previously seen in molecular gas. The disc is dominated in mass by an old stellar component at all radii sampled by our data, while the percentage of young stars increase with radius. The mean stellar age and metallicity profiles have a two defined regions, an inner one with flatter gradients (even slightly positive) and an external one with a negative, steeper one, separated at similar to 60 arcsec. This break in the profiles is more prominent in the old stellar component. The young component shows a metallicity gradient that is very similar to that of the gas, and that is flatter in the whole disc. The agreement between the metallicity gradient of the young stars and the gas, and the recovery of the measured colours from our derived star formation histories validate the techniques to recover the age-metallicity and the star formation histories in disc galaxies from integrated spectra. We speculate about the possible origin of the break and conclude that the most likely scenario is that we are seeing, in the centre of NGC 628, a dissolving bar, as predicted in some numerical simulations.
Autor principal: 
Sanchez-Blazquez, P
Autor/es del IAA: 
Sanchez, S. F.
DOI: 
10.1093/mnras/stt1984
Revista: 
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Fecha de publicación: 
2014/01
Volumen: 
437
Issue: 
2
Páginas: 
1534-1548
Tipo de documento: 
Article
Palabras clave: 
galaxies: abundances; galaxies: evolution; galaxies: formation; galaxies: spiral; galaxies: stellar content

Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf

Titulo: 
Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf
Autores: 
Anglada-Escude, G; Arriagada, P; Tuomi, M; Zechmeister, M; Jenkins, S; Ofir, A; Dreizler, S; Gerlach, E; Marvin, CJ; Reiners, A; Jeffers, SV; Butler, RP; Vogt, SS; Amado, PJ; Rodriguez-Lopez, C; Berdinas, ZM; Morin, J; Crane, JD; Shectman, SA; Thompson, IB; Diaz, M; Rivera, E; Sarmiento, LF; Jones, HRA
Resumen: 
Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this Letter, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS (High Accuracy Radial velocity Planet Searcher), High Resolution Echelle Spectrometer (HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 d using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival All Sky Automated Survey (ASAS-3) photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seem a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.
Autor principal: 
Anglada-Escude, G
Autor/es del IAA: 
Amado, P. J.; Rodriguez-Lopez, C.; Berdinas, Z. M.
DOI: 
10.1093/mnrasl/slu076
Revista: 
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Fecha de publicación: 
2014/09/01
Volumen: 
443
Issue: 
1
Páginas: 
L89-L93
Tipo de documento: 
Article
Palabras clave: 
techniques: radial velocities; stars: individual: Kapteyn's star; planetary systems

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