A second order cone formulation of continuous CTA model

The final publication is available at link.springer.comIn this paper we consider a minimum distance Controlled Tabular Adjustment (CTA) model for statistical disclosure limitation (control) of tabular data. The goal of the CTA model is to find the closest safe table to some original tabular data set that contains sensitive information. The measure of closeness is usually measured using l1 or l2 norm; with each measure having its advantages and disadvantages. Recently, in [4] a regularization of the l1 -CTA using Pseudo-Huber func- tion was introduced in an attempt to combine positive characteristics of both l1 -CTA and l2 -CTA. All three models can be solved using appro- priate versions of Interior-Point Methods (IPM). It is known that IPM in general works better on well structured problems such as conic op- timization problems, thus, reformulation of these CTA models as conic optimization problem may be advantageous. We present reformulation of Pseudo-Huber-CTA, and l1 -CTA as Second-Order Cone (SOC) op- timization problems and test the validity of the approach on the small example of two-dimensional tabular data set.Peer ReviewedPostprint (author's final draft

Constraints on the Wtb vertex from early LHC data

We use the recent measurements of top quark decay asymmetries in ATLAS and the t-channel single top cross section in CMS to set the first combined LHC limits on the Wtb vertex. This combination allows to obtain much better limits than the separate measurements. The resulting constraints are comparable, although still weaker, than the ones obtained using Tevatron data with much more statistics.Comment: RevTeX 4 page

Telescope performance and image simulations of the balloon-borne coded-mask protoMIRAX experiment

In this work we present the results of imaging simulations performed with the help of the GEANT4 package for the protoMIRAX hard X-ray balloon experiment. The instrumental background was simulated taking into account the various radiation components and their angular dependence, as well as a detailed mass model of the experiment. We modeled the meridian transits of the Crab Nebula and the Galatic Centre region during balloon flights in Brazil ($\sim -23^{\circ}$ of latitude and an altitude of $\sim 40 \thinspace$ km) and introduced the correspondent spectra as inputs to the imaging simulations. We present images of the Crab and of three sources in the Galactic Centre region: 1E 1740.7-2942, GRS 1758-258 and GX 1+4. The results show that the protoMIRAX experiment is capable of making spectral and timing observations of bright hard X-ray sources as well as important imaging demonstrations that will contribute to the design of the MIRAX satellite mission.Comment: 9 figure

Restrictions on the coherence of the ultrafast optical emission from an electron-hole pairs condensate

We report on the transfer of coherence from a quantum-well electron-hole condensate to the light it emits. As a function of density, the coherence of the electron-hole pair system evolves from being full for the low density Bose-Einstein condensate to a chaotic behavior for a high density BCS-like state. This degree of coherence is transfered to the light emitted in a damped oscillatory way in the ultrafast regime. Additionally, the photon field exhibits squeezing properties during the transfer time. We analyze the effect of light frequency and separation between electron and hole layers on the optical coherence. Our results suggest new type of ultrafast experiments for detecting electron-hole pair condensation.Comment: 4 pages,3 figures, to be published in Physical Review Letters. Minor change

Bilayer graphene: gap tunability and edge properties

Bilayer graphene -- two coupled single graphene layers stacked as in graphite -- provides the only known semiconductor with a gap that can be tuned externally through electric field effect. Here we use a tight binding approach to study how the gap changes with the applied electric field. Within a parallel plate capacitor model and taking into account screening of the external field, we describe real back gated and/or chemically doped bilayer devices. We show that a gap between zero and midinfrared energies can be induced and externally tuned in these devices, making bilayer graphene very appealing from the point of view of applications. However, applications to nanotechnology require careful treatment of the effect of sample boundaries. This being particularly true in graphene, where the presence of edge states at zero energy -- the Fermi level of the undoped system -- has been extensively reported. Here we show that also bilayer graphene supports surface states localized at zigzag edges. The presence of two layers, however, allows for a new type of edge state which shows an enhanced penetration into the bulk and gives rise to band crossing phenomenon inside the gap of the biased bilayer system.Comment: 8 pages, 3 fugures, Proceedings of the International Conference on Theoretical Physics: Dubna-Nano200

Statistical mapping of sheet aiquile SE-20-9 (national map) making use of ERTS images

New possibilities of remote sensing by means of satellites to do research on natural resources are reported. These images make it possible to carry out integrated studies of natural resources in the shortest time possible and with small investments. Various maps and a complete description of each are included. With the use of these satellites, scientists can hopefully plan development projects at the national level

Higher particle form factors of branch point twist fields in integrable quantum field theories

In this paper we compute higher particle form factors of branch point twist fields. These fields were first described in the context of massive 1+1-dimensional integrable quantum field theories and their correlation functions are related to the bi-partite entanglement entropy. We find analytic expressions for some form factors and check those expressions for consistency, mainly by evaluating the conformal dimension of the corresponding twist field in the underlying conformal field theory. We find that solutions to the form factor equations are not unique so that various techniques need to be used to identify those corresponding to the branch point twist field we are interested in. The models for which we carry out our study are characterized by staircase patterns of various physical quantities as functions of the energy scale. As the latter is varied, the beta-function associated to these theories comes close to vanishing at several points between the deep infrared and deep ultraviolet regimes. In other words, renormalisation group flows approach the vicinity of various critical points before ultimately reaching the ultraviolet fixed point. This feature provides an optimal way of checking the consistency of higher particle form factor solutions, as the changes on the conformal dimension of the twist field at various energy scales can only be accounted for by considering higher particle form factor contributions to the expansion of certain correlation functions.Comment: 25 pages, 4 figures; v2 contains small correction

XMM-Newton and Chandra observations of G272.2-3.2. Evidence of stellar ejecta in the central region

We aim to study the spatial distribution of the physical and chemical properties of the X-ray emitting plasma of the supernova remnant G272.2-3.2, in order to get important constraints on its ionization stage, on the progenitor supernova explosion, and the age of the remnant. We report combined XMM-Newton and Chandra images, median photon energy map, silicon and sulfur equivalent width maps, and a spatially resolved spectral analysis for a set of regions of the remnant. Complementary radio and H{\alpha} observations, available in the literature, are also used to study the multi-wavelength connection of all detected emissions. The X-ray morphology of the remnant displays an overall structure with an almost circular appearance, a centrally brightened hard region, with a peculiar elongated hard structure oriented along the northwest-southeast direction of the central part. The X-ray spectral study of the regions shows distinct K{\alpha} emission-line features of metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by an absorbed VNEI thermal plasma model, which produces elevated abundances of Si, S, and Fe in the circular central region, typical of ejecta material. The values of abundances found in the central region of the SNR favor a Type Ia progenitor for this remnant. The outer region shows abundances below the solar value, as expected if the emission arises from the shocked ISM. The relatively low ionization timescales suggests non-equilibrium ionization. We identify the location of the contact discontinuity. Its distance to the outer shock is higher than expected for expansion in a uniform media, what suggests that the remnant spent most of its time in a more dense medium.Comment: 9 pages, 7 figures. Accepted for publication in A&