4,634 research outputs found
Multimetric Supergravities
Making use of integral forms and superfield techniques we propose
supersymmetric extensions of the multimetric gravity Lagrangians in dimensions
one, two, three and four. The supersymmetric interaction potential covariantly
deforms the bosonic one, producing in particular suitable super-symmetric
polynomials generated by the Berezinian. As an additional application of our
formalism we construct supersymmetric multi-Maxwell theories in dimensions
three and four.Comment: 37 pages, Latex2e, no figure
Fluvial dynamics and watermills location in Basilicata (Southern Italy)
Watermills (grain mills, waulk mills, olive mills, sawmills and
threshing machines) operated in the Basilicata Region from the Roman
Period until the early decades of the twentieth century, representing an
important feature of waterways that is today almost totally forgotten. Using
documentary sources, ancient maps and field survey it is possible to
catalogue and identify the location of these ancient hydraulic structures.
Watermills were usually placed far enough away from the river to avoid
inundation during floods, and near natural knickpoints or artificial steps
in the river long profile that were created by mill engineers. Mill construction
often had significant impacts on a rivers morphology, because
it was necessary to divert the river discharge towards the mill wheel, to
drive the grain-grinding mechanism. Watermill typological variations
have been examined in relation to variations in river pattern to assess
the ways in which the hydrographic and hydrological settings of the Basilicata
Region have affected mill siting and operation. Most Basilicata
watermills were built with a horizontal water-wheel and a tower. The
characteristics of the tower and the associated hydraulic structures varied
according to the environmental setting. Finally, mill positions define
also the locations on the river system that have already been used
to exploit hydraulic power and thus could be useful for future use in the
micro-hydroelectric secto
The Fermi blazars' divide based on the diagnostic of the SEDs peak frequencies
We have studied the quasi-simultaneous Spectral Energy Distributions (SED) of
48 LBAS blazars, detected within the three months of the LAT Bright AGN Sample
(LBAS) data taking period, combining Fermi and Swift data with radio
NIR-Optical and hard-X/gamma-ray data. Using these quasi-simultaneous SEDs,
sampling both the low and the high energy peak of the blazars broad band
emission, we were able to apply a diagnostic tool based on the estimate of the
peak frequencies of the synchrotron (S) and Inverse Compton (IC) components.
Our analysis shows a Fermi blazars' divide based on the peak frequencies of the
SED. The robust result is that the Synchrotron Self Compton (SSC) region
divides in two the plane were we plot the peak frequency of the synchrotron SED
vs the typical Lorentz factor of the electrons most contributing to the
synchrotron emission and to the inverse Compton process. Objects within or
below this region, radiating likely via the SSC process, are
high-frequency-peaked BL Lac object (HBL), or low/intermediate-frequency peaked
BL Lac object (LBL/IBL). All of the IBLs/LBLs within or below the SSC region
are not Compton dominated. The objects lying above the SSC region, radiating
likely via the External radiation Compton (ERC) process, are Flat Spectrum
Radio Quasars and IBLs/LBLs. All of the IBLs/LBLs in the ERC region show a
significant Compton dominance.Comment: Contribution to the Workshop SciNeGHe 2009/Gamma-ray Physics in the
LHC era (Assisi - Italy, Oct. 7-9 2009
Analysis of the Spectral Energy Distributions of Fermi bright blazars
Blazars are a small fraction of all extragalactic sources but, unlike other
objects, they are strong emitters across the entire electromagnetic spectrum.
In this study we have conducted a detailed investigation of the broad-band
spectral properties of the gamma-ray selected blazars of the Fermi-LAT Bright
AGN Sample (LBAS). By combining the accurately estimated Fermi gamma-ray
spectra with Swift, radio, NIR-Optical and hard-X/gamma-ray data, collected
within three months of the LBAS data taking period, we were able to assemble
high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48
LBAS blazars.Comment: 6 pages, 8 figures, "2009 Fermi Symposium", "eConf Proceedings
C091122
Mathematical Support to Braneworld Theory
The braneworld theory appear with the purpose of solving the problem of the
hierarchy of the fundamental interactions. The perspectives of the theory
emerge as a new physics, for example, deviation of the law of Newton's gravity.
One of the principles of the theory is to suppose that the braneworld is local
submanifold in a space of high dimension, the bulk, solution of Einstein's
equations in high dimension. In this paper we approach the mathematical
consistency of this theory with a new proof of the fundamental theorem of
submanifolds for case of semi-Riemannian manifolds. This theorem consist an
essential mathematical support for this new theory. We find the integrability
conditions for the existence of space-time submanifolds in a pseudo-Euclidean
space.
Keywords: Submanifolds, Braneworld, Pseudo-Riemannian geometryComment: 10 page
The Embedding of Schwarzschild in Braneworld
The braneworlds models were inspired partly by Kaluza-Klein's theory, where
both the gravitational and the gauge fields are obtained from the geometry of a
higher dimensional space. The positive aspects of these models consist in
perspectives of modifications it could bring in to particle physics, such as:
unification in a TeV scale, quantum gravity in this scale and deviation of
Newton's law for small distances. One of the principles of these models is to
suppose that all space-times can be embedded in a bulk of higher dimension. The
main result in these notes is a theorem showing a mathematical inconsistency of
the Randall-Sundrum braneworld model, namely that the Schwarzschild space-time
cannot be embedded locally and isometrically in a five dimensional bulk with
constant curvature,(for example AdS-5). From the point of view of
semi-Riemannian geometry this last result represents a serious restriction to
the Randall-Sundrum's braneworld model.Comment: Published in the Int. J. Theor. Phys, 200
Achilles Tendon mechanical behavior and ankle joint function at the walk-to-run transition
Walking at speeds higher than transition speed is associated with a decrease in the plantar-flexor muscle fibres' ability to produce force and, potentially, to an impaired behaviour of the muscle-tendon unit (MTU) elastic components. This study aimed to investigate the ankle joint functional indexes and the Achilles tendon mechanical behaviour (changes in AT force and power) to better elucidate the mechanical determinants of the walk-to-run transition. Kinematics, kinetic and ultrasound data of the gastrocnemius medialis (GM) were investigated during overground walking and running at speeds ranging from 5-9 km·h-1. AT and GM MTU force and power were calculated during the propulsive phase; the ankle joint function indexes (damper, strut, spring and motor) were obtained using a combination of kinetic and kinematic data. AT force was larger in running at speeds > 6.5 km/h. The contribution of AT to the total power provided by the GM MTU was significantly larger in running at speeds > 7.5 km/h. The spring and strut indexes of the ankle were significantly larger in running at speeds > 7.5 km/h. These data suggest that the walk-to-run transition could (at least partially) be explained by the need to preserve AT mechanical behaviour and the ankle spring function
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