Two characterization of BV functions on Carnot groups via the heat semigroup

In this paper we provide two different characterizations of sets with finite perimeter and functions of bounded variation in Carnot groups, analogous to those which hold in Euclidean spaces, in terms of the short-time behaviour of the heat semigroup. The second one holds under the hypothesis that the reduced boundary of a set of finite perimeter is rectifiable, a result that presently is known in Step 2 Carnot groups

Dispersion managed mode-locking dynamics in a Ti:Sapphire laser

We present what is to our knowledge the most complete 1-D numerical analysis of the evolution and the propagation dynamics of an ultrashort laser pulse in a Ti:Sapphire laser oscillator. This study confirms the dispersion managed model of mode-locking, and emphasizes the role of the Kerr nonlinearity in generating mode-locked spectra with a smooth and well-behaved spectral phase. A very good agreement with preliminary experimental measurements is found.Comment: 11 pages, 4 figures, submitted to Optics Letter

Substructures in lens galaxies: PG1115+080 and B1555+375, two fold configurations

We study the anomalous flux ratio which is observed in some four-image lens systems, where the source lies close to a fold caustic. In this case two of the images are close to the critical curve and their flux ratio should be equal to unity, instead in several cases the observed value differs significantly. The most plausible solution is to invoke the presence of substructures, as for instance predicted by the Cold Dark Matter scenario, located near the two images. In particular, we analyze the two fold lens systems PG1115+080 and B1555+375, for which there are not yet satisfactory models which explain the observed anomalous flux ratios. We add to a smooth lens model, which reproduces well the positions of the images but not the anomalous fluxes, one or two substructures described as singular isothermal spheres. For PG1115+080 we consider a smooth model with the influence of the group of galaxies described by a SIS and a substructure with mass ∼105 M ⊙ as well as a smooth model with an external shear and one substructure with mass ∼108 M ⊙. For B1555+375 either a strong external shear or two substructures with mass ∼107 M ⊙ reproduce the data quite wel

Constraining warm dark matter using QSO gravitational lensing

Warm dark matter (WDM) has been invoked to resolve apparent conflicts of cold dark matter (CDM) models with observations on subgalactic scales. In this work, we provide a new and independent lower limit for the WDM particle mass (e.g. sterile neutrino) through the analysis of image fluxes in gravitationally lensed quasi-stellar objects (QSOs). Starting from a theoretical unperturbed cusp configuration, we analyse the effects of intergalactic haloes in modifying the fluxes of QSO multiple images, giving rise to the so-called anomalous flux ratio. We found that the global effect of such haloes strongly depends on their mass/abundance ratio and it is maximized for haloes in the mass range 106-108 M⊙. This result opens up a new possibility to constrain CDM predictions on small scales and test different warm candidates, since free streaming of WDM particles can considerably dampen the matter power spectrum in this mass range. As a consequence, while a (Λ)CDM model is able to produce flux anomalies at a level similar to those observed, a WDM model, with an insufficiently massive particle, fails to reproduce the observational evidences. Our analysis suggests a lower limit of a few keV (mν∼ 10) for the mass of WDM candidates in the form of a sterile neutrino. This result makes sterile neutrino WDM less attractive as an alternative to CDM, in good agreement with previous findings from Lyman α forest and cosmic microwave background analysi

Optimal Monetary Rules: The Case of Brazil

Within a dynamic programming approach we derive an optimal rule for the central bank to attain it's inflation targeting goals. The short-run nominal interest rate is used as an instrument to achieve monetary objectives. The model is tested for the Brazilian economy and compared with results found for other countries. Evidence for the estimated feedback interest rule for the Central Bank suggests that the cost of reducing inflation in an open economy is lower than that of a closed economy.

La fiesta patronal de Xico, Veracruz.Tradición oral y festividad

Se describen algunos aspectos dela fiesta patronal en Santa María Magdalena enXico, Veracruz, particularmente los elementosculturales indígenas incorporados a la culturafestiva xiqueña bajo los términos de «tradiciónoral». Además de constatar su presencia deestos elementos culturales, se observa que sevan ocultando cada vez más, incluso puedepensarse que su transformación apunta envarios casos hacia su pérdida u olvido. Eltrabajo estuvo enfocado de manera particularal arco floral y al mito-narración de Juan delMonte y a las vivencias de identidad quegenera los relatos sobre la imagen de SantaMaría Magdalena

The effect of low-mass substructures on the cusp lensing relation

It has been argued that the flux anomalies detected in gravitationally lensed quasi-stellar objects (QSOs) are evidence for substructures in the foreground lensing haloes. In this paper, we investigate this issue in greater detail, focusing on the cusp relation which corresponds to images of a source located to the cusp of the inner caustic curve. We use numerical simulations combined with a Monte Carlo approach to study the effects of the expected power-law distribution of substructures within Λ cold dark matter (ΛCDM) haloes on the multiple images. Generally, the high number of anomalous flux ratios in the cusp configurations is unlikely to be explained by ‘simple' perturbers (subhaloes) inside the lensing galaxy, modelled by either point masses or extended Navarro, Frenk & White subhaloes. We considered in our analysis a mass range of 105-107 M⊙ for the subhaloes. We also demonstrate that including the effects of the surrounding mass distribution, such as other galaxies close to the primary lens, does not change the results. We conclude that triple images of lensed QSOs do not show any direct evidence for dark dwarf galaxies such as CDM substructur