8,801 research outputs found
Light custodians in natural composite Higgs models
We present a class of composite Higgs models arising from a warped extra
dimension that can satisfy all the electroweak precision tests in a significant
portion of their parameter space. A custodial symmetry plays a crucial role in
keeping the largest corrections to the electroweak observables below their
experimental limits. In these models the heaviness of the top quark is not only
essential to trigger the electroweak symmetry breaking, but it also implies
that the lowest top resonance and its custodial partners, the custodians, are
significantly lighter than the other resonances. These custodians are the
trademark of these scenarios. They are exotic colored fermions of
electromagnetic charges 5/3, 2/3 and -1/3, with masses predicted roughly in the
range 500-1500 GeV. We discuss their production and detection at the LHC.Comment: 23 pages, 2 figure
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Absolute single photoionization cross-sections of Br3+: Experiment and theory
Absolute single photoionization cross section measurements for Br3+ ions are reported in the photon energy range 44.79-59.54 eV at a photon energy resolution of 21 ±3 meV. Measurements were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Numerous resonance features in the experimental spectrum are assigned and their energies and quantum defect values are tabulated. The cross-section measurements are also compared with Breit-Pauli R-matrix calculations with suitable agreement over the photon energy range investigated. Analysis of the measured spectrum including Rydberg resonance series identifications produced a new emperical determination of the ionizational potential of Br3+ of 46.977 ± 0.050 eV, which is 805 meV lower than the most recently published value of 47.782 eV. This disparity between our determination and the earlier published value is similar to an 843 meV shift in the accepted ionization potential published for iso-electronic Se2+ as part of this same research program
Wide-Field Survey of Emission-line Stars in IC 1396
We have made an extensive survey of emission-line stars in the IC 1396 HII
region to investigate the low-mass population of pre-main sequence (PMS) stars.
A total of 639 H-alpha emission-line stars were detected in an area of 4.2
deg^2 and their i'-photometry was measured. Their spatial distribution exhibits
several aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the HII region (Rim B and SFO 37, 38, 39, 41), and near
HD 206267, which is the main exciting star of the HII region. Based on the
extinction estimated from the near-infrared (NIR) color-color diagram, we have
selected pre-main sequence star candidates associated with IC 1396. The age and
mass were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. Most of our PMS candidates have ages of <
3 Myr and masses of 0.2-0.6 Mo. Although it appears that only a few stars were
formed in the last 1 Myr in the east region of the exciting star, the age
difference among subregions in our surveyed area is not clear from the
statistical test. Our results may suggest that massive stars were born after
the continuous formation of low-mass stars for 10 Myr. The birth of the
exciting star could be the late stage of slow but contiguous star formation in
the natal molecular cloud. It may have triggered to form many low-mass stars at
the dense inhomogeneity in and around the HII region by a radiation-driven
implosion.Comment: 48 pages, 12 figures, 5 tables, accepted for publication in A
Prescriptivo y simulación: etiquetaje de la eficiencia energética del edifício comercial “Torre Plaza Shopping”, Passo Fundo, RS, Brasil en función de las dos metodologías de la reglamentación brasileña – RTQ – C
El trabajo estudia la panorámica de la Eficiencia Energética, tomando em cuenta - y enfatizando el programa brasileño del INMETRO, PROCEL Edifica, contenido en la norma Requisitos Técnicos de Calidad para el Nivel de Eficiencia Energética de Edificios Comerciales, de Servicios y Públicos (RTQ –C). Con esse tema en mente, han sido consultadas algunas normativas mundiales y ha sido hecho un profundo estudio de la reglamentación brasileña vinculada. Para la mejor comprensión de la normativa, ha sido elegida una edificación comercial emblemática, en altura, en la ciudad de Passo Fundo, RS, Brasil, para ilustrar la perspectiva del programa. El edificio ha sido clasificado de acuerdo a lãs dos metodologías presentadas por la reglamentación respectiva: el Método Prescriptivo y el Método de Simulación. Se ha podido así investigar las peculiaridades de cada metodología y de la propia reglamentación en sí, basándose en el caso de estudio especifico: edificios comerciales, en altura, en el sur de Brasil, resultando en la clasificación del nivel de eficiencia energética de la edificación de referencia. Finalmente, después de haberse hecho todos los levantamientos, cálculos y simulaciones, bajo la luz de la clasificación de la edificación por los dos métodos, se han podido comparar los resultados. Se llega así a la conclusión de que el Método Prescriptivo es menos preciso y necesita de gran dedicación por parte del evaluador para elaborar todos los cálculos y levantamientos necesarios. Sin embargo, es uma herramienta más rápida y accesible a los profesionales. La Simulación, por otro lado, es una metodología más precisa y llega a niveles de análisis que el Método Prescriptivo no alcanza; no obstante, es todavía una herramienta poco conocida em Brasil y que necesita de un gran aporte financiero inicial, lo que la mantiene limitada por tanto, a grandes estudios de Construcción Civil o a Laboratorios Universitarios.Postprint (published version
Quintessential inflation from 5D warped product spaces on a dynamical foliation
Assuming the existence of a 5D purely kinetic scalar field on the class of
warped product spaces we investigate the possibility of mimic both an
inflationary and a quintessential scenarios on 4D hypersurfaces, by
implementing a dynamical foliation on the fifth coordinate instead of a
constant one. We obtain that an induced chaotic inflationary scenario with a
geometrically induced scalar potential and an induced quasi-vacuum equation of
state on 4D dynamical hypersurfaces is possible. While on a constant foliation
the universe can be considered as matter dominated today, in a family of 4D
dynamical hypersurfaces the universe can be passing for a period of accelerated
expansion with a deceleration parameter nearly -1. This effect of the dynamical
foliation results negligible at the inflationary epoch allowing for a chaotic
scenario and becomes considerable at the present epoch allowing a
quintessential scenario.Comment: 7 pages, 1 figure Accepted for publication in Modern Physics Letters
Effective Monopoles within Thick Branes
The monopole mass is revealed to be considerably modified in the thick
braneworld paradigm, and depends on the position of the monopole in the brane
as well. Accordingly, the monopole radius continuously increases, leading to an
unacceptable setting that can be circumvented when the brane thickness has an
upper limit. Despite such peculiar behavior, the quantum corrections accrued --
involving the classical monopole solution -- are shown to be still under
control. We analyze the monopole's peculiarities also taking into account the
localization of the gauge fields. Furthermore, some additional analysis in the
thick braneworld context and the similar behavior evinced by the topological
string are investigated.Comment: 7 pages, 1 figur
A New Method for the Assessment of Age and Age-Spread of Pre-Main Sequence Stars in Young Stellar Associations of the Magellanic Clouds
We present a new method for the evaluation of the age and age-spread among
pre-main-sequence (PMS) stars in star-forming regions in the Magellanic Clouds,
accounting simultaneously for photometric errors, unresolved binarity,
differential extinction, stellar variability, accretion and crowding. The
application of the method is performed with the statistical construction of
synthetic color-magnitude diagrams using PMS evolutionary models. We convert
each isochrone into 2D probability distributions of artificial PMS stars in the
CMD by applying the aforementioned biases that dislocate these stars from their
original CMD positions. A maximum-likelihood technique is then applied to
derive the probability for each observed star to have a certain age, as well as
the best age for the entire cluster. We apply our method to the photometric
catalog of ~2000 PMS stars in the young association LH 95 in the LMC, based on
the deepest HST/ACS imaging ever performed toward this galaxy, with a detection
limit of V~28, corresponding to M~0.2 Msun. Our treatment shows that the age
determination is very sensitive to the considered grid of evolutionary models
and the assumed binary fraction. The age of LH 95 is found to vary from 2.8 Myr
to 4.4 Myr, depending on these factors. Our analysis allows us to disentangle a
real age-spread from the apparent CMD-broadening caused by the physical and
observational biases. We find that LH 95 hosts an age-spread well represented
by a gaussian distribution with a FWHM of the order of 2.8 Myr to 4.2 Myr
depending on the model and binary fraction. We detect a dependence of the
average age of the system with stellar mass. This dependence does not appear to
have any physical meaning, being rather due to imperfections of the PMS
evolutionary models, which tend to predict lower ages for the intermediate
masses, and higher ages for low-mass stars.Comment: 19 pages, 16 figures, accepted for publication by the Astrophysical
Journa
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