Lasso Estimation of an Interval-Valued Multiple Regression Model

A multiple interval-valued linear regression model considering all the cross-relationships between the mids and spreads of the intervals has been introduced recently. A least-squares estimation of the regression parameters has been carried out by transforming a quadratic optimization problem with inequality constraints into a linear complementary problem and using Lemke's algorithm to solve it. Due to the irrelevance of certain cross-relationships, an alternative estimation process, the LASSO (Least Absolut Shrinkage and Selection Operator), is developed. A comparative study showing the differences between the proposed estimators is provided

Antiferromagnetism in four dimensions: search for non-triviality

We present antiferromagnetism as a mechanism capable of modifying substantially the phase diagram and the critical behaviour of statistical mechanical models. This is particularly relevant in four dimensions, due to the connection between second order transition points and the continuum limit as a quantum field theory. We study three models with an antiferromagnetic interaction: the Ising and the O(4) Models with a second neighbour negative coupling, and the \RP{2} Model. Different conclusions are obtained depending on the model.Comment: 4 pages LateX. Contribution to Lat9

Phase diagram of d=4 Ising Model with two couplings

We study the phase diagram of the four dimensional Ising model with first and second neighbour couplings, specially in the antiferromagnetic region, by using Mean Field and Monte Carlo methods. From the later, all the transition lines seem to be first order except that between ferromagnetic and disordered phases in a region including the first-neighbour Ising transition point.Comment: Latex file and 4 figures (epsfig required). It replaces the preprint entitled "Non-classical exponents in the d=4 Ising Model with two couplings". New analysis with more statistical data is performed. Final version to appear in Phys. Lett.

Functional Integral Bosonization for Impurity in Luttinger Liquid

We use a functional integral formalism developed earlier for the pure Luttinger liquid (LL) to find an exact representation for the electron Green function of the LL in the presence of a single backscattering impurity. This allows us to reproduce results (well known from the bosonization techniques) for the suppression of the electron local density of states (LDoS) at the position of the impurity and for the Friedel oscillations at finite temperature. In addition, we have extracted from the exact representation an analytic dependence of LDoS on the distance from the impurity and shown how it crosses over to that for the pure LL.Comment: 7 pages, 1 LaTeX produced figur

Assessing sea grass meadows condition at “El Río” Special Area of Conservation off “La Graciosa e Islotes del Norte de Lanzarote” Marine Reserve

Cymodosea nodosa meadows, known as ‘sebadales’ or ‘manchones’ at Canary Islands, represent EUNIS habitat type code A5.5311, called Macaronesian Cymodocea beds. As it’s described at European Union Habitats Directive (92/43/CEE) Annex 1, sea grass meadows belong to 1110 Sandbanks which are slightly covered by seawater all the time, within Natura 2000 Network. Several ‘sebadales’ throughout the archipelago are included in this Network as Special Areas of Conservation. Cymodosea nodosa is regionally included within the Canary Islands Protected Species List (Ley 4/2010), as a species ‘of interest to ecosystems of Canary Islands”, is usually found at a narrow depth range (10 to 20 m of depth) and, on the whole, best structured meadows are settled at sheltered bays, away from wave and current beating, flimsier at exposed areas. Deeper meadows are also sparser, being C. nodosa replaced by green algae Caulerpa prolifera and Caulerpa racemosa, although mixed algae-sea grass meadows are often found at different depths. The project Assessment of marine flora (‘sebadal’, ma¨erl, ‘mujo’) of ‘La Graciosa e Islotes del Norte de Lanzarote’ Marine Reserve, funded by ‘Viceconsejer´ıa de Pesca y Aguas de la Consejer´ıa de Agricultura, Ganader´ıa, Pesca y Aguas’, Canary Islands Government, has had the aim of assessing sea grass meadows condition and distribution at ‘El R´ıo’ Natura 2000 Network Special Area of Conservation, the channel between La Graciosa and Lanzarote. ‘LA GRACIOSA 1311’ cruise was performed within the framework of the project. First of all previous information on sea grass shallow distribution (up to a depth of 20 m) in the study area was reviewed. Afterwards, a tugged underwater video camera was used onboard of the Marine Reserve Surveillance Vessel to update cartographic info performing a grid of sampling stations, covering previously known distribution limits and verifying current presence/absence data and density. Furthermore, population parameters were obtained in order to assess ‘sebadal’ condition. Fixed stations were selected in regards to this process, and methodology applied on them was as follows: five radial arranged transects were performed, identifying fragmentation (it estimates meadow continuity regarding observed cover), density (mean value of several shoots number counts with 20 x 20 cm grids placed every 2 m), height (mean value in cm of 10 independent samples by transect) and fish and macroinvertebrate species richness for each transect. Graphic picture of sea grass density was made depending on two levels: low density level transects ( 10 shoots/grid ( 50 shoots/m2) and medium density level transects ( 10 shoots/grid ( 50 shoots/m2). Main study result is an estimate for the study region (‘El R´ıo’) and time of year of Cymodocea nodosa population total distribution cover which comes to 1.640.076 m2, including a higher density ‘sebadal’ of 178.256 m2

Effects of the anthropogenics pressures (marine litter) on the coastal ecosystems of the Marine Reserve “Isla de La Graciosa e islotes del norte de Lanzarote”

The European Marine Strategy Framework Directive (2008/56/EC) considers marine litter as one of its environmental descriptors, requiring the development and standardization of criteria and methodologies for its use to test the good environmental status of marine conditions. The assessment of the impact caused by litter accumulation in the shoreline lacked specific monitoring planning and had not been systematically performed to date in Canary Islands. During the project ”Evaluation of the effect of the anthropogenic pressures (marine litter in beaches and alteration of shallow seabed by boats anchoring) on the coastal ecosystems of the “Marine Reserve of Isla de La Graciosa e islotes del norte de Lanzarote (MRLG)” developed with the financial help of the Canary Islands Government (Council of Agriculture, Ranching, Fishing and Waters), two surveys were carried out, ”LA GRACIOSA 1310” and “LA GRACIOSA 1311”, both developed at MRLG and its vicinities. The aim has been to depict MRLG shoreline and to locate marine litter accumulation points the most, contributing with some tools to assess and manage the coastal ecosystems of the marine reserve. Total shoreline sampled at both surveys together was 38326 m, 1834 m at Alegranza, 1366 m at Monta˜na Clara, 24656 m at La Graciosa Island, and the rest, 10470 m, at the Lanzarote’s shoreline portion bathed by MRLG waters. Shoreline sampling was made qualitatively sorting the sampling stations, according to litter presence and distribution, by means of a upward numerical coding related to the type of waste or garbage found. Moreover, each station was additionally depicted according to the type of substrate as well as to the prevailing type of waste, defining what we named “transects”. To validate methodology to European standards, a more exhaustive experimental sampling was made in four transects identified as high density or high concentration of marine litter, following guidelines of a method developed for OSPAR maritime area during the first half of 2000 decade (OSPAR, 2007). It involves evaluating the possibilities and needs of adjustment of this methodology to the particular conditions of our region (Gonz´alez, et al., 2013 a and b). As preliminary results, the spatial distribution of garbage coastal accumulation will be shown in a cartographic base, expressed as relative abundance by island, according to a 4 degrees scale (no litter, low, medium and high litter presence) and according to the dominant kind of garbage in each transect. An example with one of the most densely occupied with trash transects is shown to illustrate a sampling method without the requirement of trash collection. This method uses a sampling unit of 1x1 m grid, divided in 10x10 cm subgrids. This grid is set parallel to sampling direction repeatedly. Distance between grids is determined by a randomizing software. Sampling direction zigzags from sea border to beach back shore, making 45° degrees angles. Subgrids occupied by trash are counted once the grid is set. Waste is depict and identified following a guide developed for this purpose by OSPAR in 2010

Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight

The first flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment recorded 16 radio signals that were emitted by cosmic-ray induced air showers. For 14 of these events, this radiation was reflected from the ice. The dominant contribution to the radiation from the deflection of positrons and electrons in the geomagnetic field, which is beamed in the direction of motion of the air shower. This radiation is reflected from the ice and subsequently detected by the ANITA experiment at a flight altitude of 36km. In this paper, we estimate the energy of the 14 individual events and find that the mean energy of the cosmic-ray sample is 2.9 EeV. By simulating the ANITA flight, we calculate its exposure for ultra-high energy cosmic rays. We estimate for the first time the cosmic-ray flux derived only from radio observations. In addition, we find that the Monte Carlo simulation of the ANITA data set is in agreement with the total number of observed events and with the properties of those events.Comment: Added more explanation of the experimental setup and textual improvement

Menus for Feeding Black Holes

Black holes are the ultimate prisons of the Universe, regions of spacetime where the enormous gravity prohibits matter or even light to escape to infinity. Yet, matter falling toward the black holes may shine spectacularly, generating the strongest source of radiation. These sources provide us with astrophysical laboratories of extreme physical conditions that cannot be realized on Earth. This chapter offers a review of the basic menus for feeding matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher

Cosmological distance indicators

We review three distance measurement techniques beyond the local universe: (1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and (3) HI intensity mapping. We describe the principles and theory behind each method, the ingredients needed for measuring such distances, the current observational results, and future prospects. Time delays from strongly lensed quasars currently provide constraints on $H_0$ with < 4% uncertainty, and with 1% within reach from ongoing surveys and efforts. Recent exciting discoveries of strongly lensed supernovae hold great promise for time-delay cosmography. BAO features have been detected in redshift surveys up to z <~ 0.8 with galaxies and z ~ 2 with Ly-$\alpha$ forest, providing precise distance measurements and $H_0$ with < 2% uncertainty in flat $\Lambda$CDM. Future BAO surveys will probe the distance scale with percent-level precision. HI intensity mapping has great potential to map BAO distances at z ~ 0.8 and beyond with precisions of a few percent. The next years ahead will be exciting as various cosmological probes reach 1% uncertainty in determining $H_0$, to assess the current tension in $H_0$ measurements that could indicate new physics.Comment: Review article accepted for publication in Space Science Reviews (Springer), 45 pages, 10 figures. Chapter of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Ag