Results for "G. De Rosa"

total 131566took 0.13s
Close and distant reprocessing media in Mkn509 studied with BeppoSAXSep 25 2003We present the broad band analysis of two BeppoSAX observations of the Sy 1 Mkn509. In 2000 the source was in a typical flux state, F{2-10keV}=2.7x10^{-11}erg cm^{-2} s^{-1}, while in 1998 it was found in a high flux state, F{2-10keV}=5.7x10^{-11} erg ... More
Clearing up the clouds around NGC 4151: evidence of a highly ionized absorberAug 29 2005The Seyfert 1 galaxy NGC4151 is characterized by complex X-ray absorption, well described by a dual absorber, composed of a uniform mildly ionized gas and a cold system that partially covers the central source. However, in one of the 5 BeppoSAX observations, ... More
The impact of a non-universal Initial Mass Function on the Star Formation Histories of Early-Type GalaxiesJan 29 2013Recent results on the non-universality of the Initial Mass Function (IMF) have shown strong evidence of IMF variations with galaxy velocity dispersion, with a corresponding impact on other stellar population parameters, line indices and colours. Using ... More
Dissecting the size evolution of elliptical galaxies since z~1: puffing up vs minor merging scenariosFeb 16 2011May 09 2011We have explored the buildup of the local mass-size relation of elliptical galaxies using two visually classified samples. At low redshift we compiled a subsample of 2,656 elliptical galaxies from SDSS, whereas at higher redshift (up to z~1) we extracted ... More
On the Helicity conservation for the incompressible Euler equationsDec 03 2018In this work we investigate the helicity regularity for weak solutions of the incompressible Euler equations. To prove regularity and conservation of the helicity we will use two different approaches: in the first we threat the velocity $u$ and its $curl\, ... More
Minimization of anisotropic energies in classes of rectifiable varifoldsNov 23 2016We consider the minimization problem of an anisotropic energy in classes of $d$-rectifiable varifolds in $\mathbb R^n$, closed under Lipschitz deformations and encoding a suitable notion of boundary. We prove that any minimizing sequence with density ... More
Confidence Decision Trees via Online and Active Learning for Streaming (BIG) DataApr 12 2016Decision tree classifiers are a widely used tool in data stream mining. The use of confidence intervals to estimate the gain associated with each split leads to very effective methods, like the popular Hoeffding tree algorithm. From a statistical viewpoint, ... More
The missing matter problem: from the dark matter search to alternative hypothesesOct 23 2011Nov 07 2011Dark matter is among the most important open problems in both astrophysics and particle physics. We review the status of art of dark matter search at theoretical and experimental level discussing also alternative hypotheses.
The link between the Star Formation History and [alpha/Fe]Aug 31 2011(Abridged) The abundance ratios between key elements such as iron and alpha-process elements carry a wealth of information on the star formation history (SFH) of galaxies. So far, simple chemical evolution models have linked [alpha/Fe] with the SFH timescale, ... More
SPIDER II - The Fundamental Plane of Early-type Galaxies in grizYJHKDec 23 2009Jun 03 2010We present a complete analysis of the Fundamental Plane of early-type galaxies (ETGs) in the nearby universe. The sample, as defined in paper I, comprises 39,993 ETGs located in environments covering the entire domain in local density (from field to cluster). ... More
The Fundamental Plane of Elliptical Galaxies in Compact GroupsApr 19 2001We present a study focusing on the nature of compact groups through the study of their elliptical galaxies. We determine velocity dispersions ($\sigma$) for 18 18 bright elliptical galaxies located in the core of Hickson compact groups and a control sample ... More
A Principal Component Analysis approach to the Star Formation History of elliptical galaxies in Compact GroupsNov 27 2005May 26 2006(Abridged) Environmental differences in the stellar populations of early-type galaxies are explored using principal component analysis (PCA), focusing on differences between elliptical galaxies in Hickson Compact Groups (HCGs) and in the field. The method ... More
Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population StudySep 18 2006We present the results of a study comparing the stellar populations in the elliptical galaxies of Hickson Compact Groups (HCGs) with those in low density environments. Three different population synthesis models and stellar population analyses are used ... More
Gamma Ray Bursts Scaling Relations to test cosmological modelsJun 28 2012Jun 29 2012Gamma ray burst (GRBs) can be used to constrain cosmological parameters from medium up to very high redshift. These powerful systems could be the further reliable distance indicators after SNeIa supernovae. We consider GRBs samples to achieve the luminosity ... More
XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11Sep 01 2005We report on the XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11. Data from the EPIC/p-n camera, the Reflection Gratings Spectrometers (RGS) and the Optical Monitor (OM) have been analyzed. The p-n spectrum is well fitted by a power ... More
The SDSS-UKIDSS Fundamental Plane of Early-type GalaxiesJul 24 2008We derive the Fundamental Plane (FP) relation for a sample of 1430 early-type galaxies in the optical (r band) and the near-infrared (K band), by combining SDSS and UKIDSS data. With such a large, homogeneous dataset, we are able to assess the dependence ... More
X-ray absorption lines suggest matter infalling onto the central black-hole of Mrk 509Jun 28 2005Evidence for both red- and blue-shifted absorption lines due to ionized Fe in the X-ray spectrum of the Seyfert 1 galaxy Mrk 509 are reported. These features appear to be transient on time-scales as short as ~20 ks, and have been observed with two different ... More
Cosmological implications of a class of SO(10) modelsMay 02 1997The cosmological implications of a class of SO(10) models are discussed. In particular we show how a good prediction for neutrino masses is obtained in order to fit with the MSW mechanism to explain the solar neutrino flux deficit and with the predicted ... More
The particle-hole transformation, supersymmetry and achiral boundaries of the open Hubbard modelDec 10 2014Apr 13 2015We show that the particle-hole transformation in the Hubbard model has a crucial role in relating Shastry's R-matrix to the AdS/CFT S-matrix. In addition, we construct an achiral boundary for the open Hubbard chain which possesses twisted Yangian symmetry. ... More
Absence of bubbling phenomena for non convex anisotropic nearly umbilical and quasi Einstein hypersurfacesMar 24 2018We prove that, for every closed (not necessarily convex) hypersurface $\Sigma$ in $\mathbb{R}^{n+1}$ and every $p>n$, the $L^p$-norm of the trace-free part of the anisotropic second fundamental form controls from above the $W^{2,p}$-closeness of $\Sigma$ ... More
Superradiant amplification by stars and black holesFeb 24 2016In this thesis we study the phenomenon of superradiance and its implications to the stability of black-holes (BH) and perfect-fluid stars. Superradiance is a radiation enhancement process that involves rotating dissipative systems. In BH spacetimes, superradiance ... More
Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum MechanicsSep 28 2005Apr 04 2006We consider Noncommutative Quantum Mechanics with phase space noncommutativity. In particular, we show that a scaling of variables leaves the noncommutative algebra invariant, so that only the self-consistent effective parameters of the model are physically ... More
Monitoring the temperature and reverberation delay of the circumnuclear hot dust in NGC 4151Apr 27 2015A hot, dusty torus located around the outer edge of the broad-line region of AGNs is a fundamental ingredient in unified AGN models. While the existence of circumnuclear dust around AGNs at pc-scale radii is now widely accepted, questions about the origin, ... More
The extremal black hole bombDec 09 2009Jun 02 2010We analyze the spectrum of massive scalar bound states in the background of extremal Kerr black holes, focusing on modes in the superradiant regime, which grow exponentially in time and quickly deplete the black hole's mass and spin. Previous analytical ... More
Superradiance in the skyDec 06 2016We discuss the conditions under which plane electromagnetic and gravitational waves can be amplified by a rotating black hole due to superradiant scattering. We show, in particular, that amplification can occur for low-frequency waves with an incidence ... More
Testing black hole superradiance with pulsar companionsJan 29 2015Aug 13 2015We show that the magnetic dipole and gravitational radiation emitted by a pulsar can undergo superradiant scattering off a spinning black hole companion. We find that the relative amount of superradiant modes in the radiation depends on the pulsar's angular ... More
Boosted black string bombsSep 19 2012Feb 11 2013We study the formation of superradiant bound states for massive scalar fields in five-dimensional rotating black string geometries with a non-vanishing Kaluza-Klein momentum along the compact direction. Even though all Kaluza-Klein modes may form bound ... More
Discovery of true, likely and possible symbiotic stars in the dwarf spheroidal NGC 205Nov 19 2014In this paper we discuss the photometric and spectroscopic observations of newly discovered (symbiotic) systems in the dwarf spheroidal galaxy NGC 205. The Gemini Multi-Object Spectrograph on-off band [O III] 5007 A emission imaging highlighted several ... More
Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)Nov 13 2002We report on the discovery of recently ionized hydrogen-deficient gas in the immediate circumstellar environment of the final helium shell flash star V4334 Sgr (Sakurai's object). On spectra obtained with FORS2 multi-object spectroscopy we have found ... More
An XMM-Newton observation of Ark 120: the X-ray spectrum of a `bare' Seyfert 1 nucleusFeb 27 2004Mar 02 2004We report on a long (100 ks) XMM-Newton observation of the bright Seyfert 1 galaxy Arakelian 120. The source previously showed no signs of intrinsic reddening in its infrared-ultraviolet continuum and previous observations had shown no evidence for ionized ... More
Crystal structure and physical properties of EuPtIn$_{4}$ intermetallic antiferromagnetApr 07 2014We report the synthesis of EuPtIn$_{4}$ single crystalline platelets by the In-flux technique. This compound crystallizes in the orthorhombic Cmcm structure with lattice parameters $a=4.542(1)$ \AA, $b=16.955(2)$ \AA$\,$ and $c=7.389(1)$ \AA. Measurements ... More
Sistemas C-ortocéntricos, bisectrices y euclidianidad en planos de MinkowskiAug 21 2014Mediante el estudio de propiedades geom\'etricas de los sistemas C-ortoc\'entricos, relacionadas con las nociones de ortogonalidad (Birkhoff, is\'osceles, cordal), bisectriz (Busemann, Glogovskij) y l\'inea soporte a una circunferencia, se muestran nueve ... More
Equivalence of the ellipticity conditions for geometric variational problemsOct 16 2018Nov 11 2018We exploit the so called atomic condition, recently defined by De Philippis, De Rosa, and Ghiraldin in [Comm. Pure Appl. Math.] and proved to be necessary and sufficient for the validity of the anisotropic counterpart of the Allard rectifiability theorem. ... More
Regularity in time of Hölder solutions of Euler and hypodissipative Navier-Stokes equationsNov 30 2018In this work we investigate some regularization properties of the incompressible Euler equations and of the fractional Navier-Stokes equations where the dissipative term is given by $(-\Delta)^\alpha$, for a suitable power $\alpha \in (0,\frac{1}{2})$ ... More
C-orthocenter and C-orthocentric systems in Minkowski planesAug 31 2014Usando la noci\'on de C-ortocentro se extienden, a planos de Minkowski en general, nociones de la geometr\'ia cl\'asica relacionadas con un tri\'angulo, como por ejemplo: puntos de Euler, tri\'angulo de Euler, puntos de Poncelet. Se muestran propiedades ... More
On a question of D. SerreMar 15 2019In this paper we give a negative answer to the question posed in [15, Open Question 2.1] about possible gains of integrability of determinants of divergence-free, non-negative definite matrix-fields. We also analyze the case in which the matrix-field ... More
Noncommutative Gravitational Quantum WellMay 06 2005We study noncommutative geometry at the Quantum Mechanics level by means of a model where noncommutativity of both configuration and momentum spaces is considered. We analyze how this model affects the problem of the two-dimensional gravitational quantum ... More
A tale of a rich cluster at z$\sim$0.8 as seen by the Star Formation Histories of its ETGsOct 20 2014We present a detailed stellar population analysis for a sample of 24 early-type galaxies belonging to the rich cluster RXJ0152.7-1357 at z=0.83. We have derived the age, metallicity, abundance pattern and star formation history for each galaxy individually, ... More
SPIDER X - Environmental effects in central and satellite early-type galaxies through the stellar fossil recordAug 28 2014A detailed analysis of how environment affects the star formation history of early-type galaxies (ETGs) is undertaken via high signal to noise ratio stacked spectra obtained from a sample of 20,977 ETGs (morphologically selected) from the SDSS-based SPIDER ... More
SPIDER - III. Environmental Dependence of the Fundamental Plane of Early-type GalaxiesMar 04 2010Jun 29 2010We analyse the Fundamental Plane (FP) relation of $39,993$ early-type galaxies (ETGs) in the optical (griz) and $5,080$ ETGs in the Near-Infrared (YJHK) wavebands, forming an optical$+$NIR sample of $4,589$ galaxies. We focus on the analysis of the FP ... More
New estimates of the CMB angular power spectra from the WMAP 5 yrs low resolution dataApr 05 2009Aug 05 2009A Quadratic Maximum Likelihood (QML) estimator is applied to the WMAP 5 year low resolution maps to compute the CMB angular power spectra at large scales for both temperature and polarization. Estimates and error bars for the six angular power spectra ... More
Superdense massive galaxies in the Nearby UniverseJan 08 2009Superdense massive galaxies (r_e~1 kpc; M~10^{11} Msun) were common in the early universe (z>1.5). Within some hierarchical merging scenarios, a non-negligible fraction (1-10%) of these galaxies is expected to survive since that epoch retaining their ... More
Low-temperature spectroscopy of the $^{12}$C$_2$H$_2$ ($\upsilon_1 +\upsilon_3$) band in a helium buffer gasOct 20 2014Buffer gas cooling with a $^4$He gas is used to perform laser-absorption spectroscopy of the $^{12}$C$_2$H$_2$ ($\nu_1+\nu_3$) band at cryogenic temperatures. Doppler thermometry is first carried out to extract translational temperatures from the recorded ... More
The star formation histories of fossil group galaxiesSep 28 2009A comparison is carried out among the star formation histories of early-type galaxies (ETG) in fossil groups, clusters and low density environments. Although they show similar evolutionary histories, a significant fraction of the fossils are younger than ... More
Modeling the flaring activity of the high z, hard X-ray selected blazar IGR J22517+2217Dec 02 2011We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray data from INTEGRAL and Swift-BAT survey, to investigate the physical properties of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217, through the modelization ... More
On the Radial Stellar Content of Early-Type Galaxies as a Function of Mass and EnvironmentAug 03 2011Using optical-optical and optical-NIR colors, we analyze the radial dependence of age and metallicity inside massive (M* > 10^10.5 MSun), low-redshift (z<0.1), early-type galaxies (ETGs), residing in both high-density group regions and the field. On average, ... More
A new generation photodetector for astroparticle physics: the VSiPMTJul 10 2014Jul 17 2014The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design we proposed for a revolutionary photon detector. The main idea is to replace the classical dynode chain of a PMT with a SiPM (G-APD), the latter acting as an electron detector and ... More
The broad band spectrum and variability of NGC 4151 observed by BeppoSAXNov 15 2006We present an analysis of all SAX observations of NGC 4151. This source was observed 5 times from 1996 to 2001 with durations ranging from a day to four days. The intrinsic continuum, is absorbed at low energies by a complex system: a cold patchy absorber ... More
Compact Galaxies at Intermediate Redshifts Quench Faster than Normal-sized GalaxiesJan 11 2019Massive quiescent compact galaxies have been discovered at high redshifts, associated with rapid compaction and cessation of star formation (SF). In this work we set out to quantify the time-scales in which SF is quenched in compact galaxies at intermediate ... More
Gravitational Quantum WellDec 07 2005Jan 27 2006We discuss the implications of a model of noncommutative Quantum Mechanics where noncommutativity is extended to the phase space. We analyze how this model affects the problem of the two-dimensional gravitational quantum well and use the latest experimental ... More
Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion RelationDec 20 2004May 11 2005We study the recently proposed Lorentz-violating dispersion relation for fermions and show that it leads to two distinct cubic operators in the momentum. We compute the leading order terms that modify the non-relativistic equations of motion and use experimental ... More
A GRID solution for Gravitational Waves Signal Analysis from Coalescing Binaries: preliminary algorithms and testsMay 29 2003The analysis of data coming from interferometric antennas for gravitational waves detection may require a huge amount of computing power. The usual approach to the detection strategy is to set-up computer farms able to perform several tasks in parallel, ... More
High-energy monitoring of Seyfert galaxies: the case of NGC 4593Oct 07 2015We discuss preliminary results from a joint XMM-Newton and NuSTAR monitoring program on the active galactic nucleus NGC 4593, consisting of 5x20 ks observations, spaced by two days, performed in January 2015. The source is found to be variable, both in ... More
An intermediate black hole spin in the NLS1 galaxy SWIFT J2127.4+5654: chaotic accretion or spin energy extraction?May 18 2009We have observed the hard X-ray selected Narrow-Line Seyfert 1 galaxy SWIFT J2127.4+5654 with Suzaku. We report the detection of a broad relativistic iron emission line from the inner accretion disc. By assuming that the inner edge of the accretion disc ... More
Young ages and other intriguing properties of massive compact galaxies in the Local UniverseMar 12 2012We characterize the kinematics, morphology, stellar populations and star formation histories of a sample of massive compact galaxies in the nearby Universe, which might provide a closer look to the nature of their high redshift (z > 1.0) massive counterparts. ... More
The BeppoSAX broad-band spectrum and variability of the Seyfert 1 NGC 3783Mar 20 2002BeppoSAX observed the Seyfert 1 galaxy NGC 3783 for ~ 5 days from 1998 June 6 to 1998 June 10. The average flux during the observation was F(2-10 keV) ~ 6 X 10^{-11} erg cm^-2 s^-1. The long exposure provided a very high quality spectrum that exhibits ... More
High-energy monitoring of NGC 4593 II. Broadband spectral analysis: testing the two-corona modelDec 07 2018It is widely believed that the primary X-ray emission of AGN is due to the Comptonisation of optical-UV photons from a hot electron corona, while the origin of the 'soft-excess' is still uncertain and matter of debate. A second Comptonisation component, ... More
On The Nature of Fossil Galaxy GroupsSep 17 2009We present a new sample of 25 fossil groups (FGs) at z < 0.1, along with a control sample of seventeen bright ellipticals located in non-fossil systems. Both the global properties of FGs (e.g. X-ray luminosity) as well as the photometric properties (i.e. ... More
High-energy monitoring of NGC 4593 with XMM-Newton and NuSTAR. X-ray spectral analysisAug 09 2016We present results from a joint Xmm-Newton/NuSTAR monitoring of the Seyfert 1 NGC 4593, consisting of 5x20 ks simultaneous observations spaced by two days, performed in January 2015. The source is variable, both in flux and spectral shape, on time-scales ... More
On the Nature of Fossil Galaxy Groups: Are they really fossils ?Dec 15 2008We use SDSS-DR4 photometric and spectroscopic data out to redshift z~0.1 combined with ROSAT All Sky Survey X-ray data to produce a sample of twenty-five fossil groups (FGs), defined as bound systems dominated by a single, luminous elliptical galaxy with ... More
Quantum and Classical divide: the gravitational caseAug 01 2005Nov 18 2005We study the transition between quantum and classical behavior of particles in a gravitational quantum well. We analyze how an increase in the particles mass turns the energy spectrum into a continuous one, from an experimental point of view. We also ... More
Warm InflectionOct 30 2012Jan 14 2013While ubiquitous in supersymmetric and string theory models, inflationary scenarios near an inflection point in the scalar potential generically require a severe fine-tuning of a priori unrelated supersymmetry breaking effects. We show that this can be ... More
The Life of Lazarillo de Tormes and of His Machine Learning AdversitiesNov 16 2016Summit work of the Spanish Golden Age and forefather of the so-called picaresque novel, The Life of Lazarillo de Tormes and of His Fortunes and Adversities still remains an anonymous text. Although distinguished scholars have tried to attribute it to ... More
Conditional probability calculation using restricted Boltzmann machine with application to system identificationJun 07 2018There are many advantages to use probability method for nonlinear system identification, such as the noises and outliers in the data set do not affect the probability models significantly; the input features can be extracted in probability forms. The ... More
The partition algebra and the Kronecker coefficientsOct 20 2012Feb 25 2013We propose a new approach to study the Kronecker coefficients by using the Schur-Weyl duality between the symmetric group and the partition algebra. We explain the limiting behavior and associated bounds in the context of the partition algebra. Our analysis ... More
A Near-coplanar Stellar Flyby of the Planet Host Star HD 106906Feb 26 2019We present an investigation into the kinematics of HD 106906 using the newly released Gaia DR2 catalog to search for close encounters with other members of the Scorpius-Centaurus (Sco-Cen) association. HD 106906 is an eccentric spectroscopic binary that ... More
Online Open World RecognitionApr 08 2016As we enter into the big data age and an avalanche of images have become readily available, recognition systems face the need to move from close, lab settings where the number of classes and training data are fixed, to dynamic scenarios where the number ... More
Improved stability of optimal traffic pathsJan 25 2017Models involving branched structures are employed to describe several supply-demand systems such as the structure of the nerves of a leaf, the system of roots of a tree and the nervous or cardiovascular systems. Given a flow (traffic path) that transports ... More
A Survey of Security Assessment OntologiesJun 29 2017A literature survey on ontologies concerning the Security Assessment domain has been carried out to uncover initiatives that aim at formalizing concepts from the Security Assessment field of research. A preliminary analysis and a discussion on the selected ... More
Stability for the mailing problemJan 17 2018We prove that optimal traffic plans for the mailing problem in $\mathbb{R}^d$ are stable with respect to variations of the given coupling, above the critical exponent $\alpha=1-1/d$, thus solving an open problem stated in the book "Optimal transportation ... More
Data-Driven Fuzzy Modeling Using Deep LearningFeb 23 2017Fuzzy modeling has many advantages over the non-fuzzy methods, such as robustness against uncertainties and less sensitivity to the varying dynamics of nonlinear systems. Data-driven fuzzy modeling needs to extract fuzzy rules from the input/output data, ... More
SPIDER VIII - Constraints on the Stellar Initial Mass Function of Early-type Galaxies from a Variety of Spectral FeaturesMay 10 2013May 29 2013We perform a spectroscopic study to constrain the stellar Initial Mass Function (IMF) by using a large sample of 24,781 early-type galaxies from the SDSS-based SPIDER survey. Clear evidence is found of a trend between IMF and central velocity dispersion, ... More
Systematic variation of the stellar Initial Mass Function with velocity dispersion in early-type galaxiesJun 07 2012Oct 11 2012An essential component of galaxy formation theory is the stellar initial mass function (IMF), that describes the parent distribution of stellar mass in star forming regions. We present observational evidence in a sample of early-type galaxies (ETGs) of ... More
Spheroid's Panchromatic Investigation in Different Environmental Regions (SPIDER) - I. Sample and galaxy parameters in the grizYJHK wavebandsDec 23 2009Jun 03 2010This is the first paper of a series presenting a Spheroid's Panchromatic Investigation in Different Environmental Regions (SPIDER). The sample of spheroids consists of 5,080 bright (Mr<-20) Early-Type galaxies (ETGs), in the redshift range of 0.05 to ... More
SPIDER - IV. Optical and NIR color gradients in Early-type galaxies: New Insights into Correlations with Galaxy PropertiesJun 21 2010Sep 17 2010We present an analysis of stellar population gradients in 4,546 Early-Type Galaxies with photometry in $grizYHJK$ along with optical spectroscopy. A new approach is described which utilizes color information to constrain age and metallicity gradients. ... More
Rectifiability of varifolds with locally bounded first variation with respect to anisotropic surface energiesSep 07 2016Sep 15 2016We extend Allard's celebrated rectifiability theorem to the setting of varifolds with locally bounded first variation with respect to an anisotropic integrand. In particular, we identify a sufficient and necessary condition on the integrand to obtain ... More
Discovery of three z>6.5 quasars in the VISTA Kilo-degree Infrared Galaxy (VIKING) surveyNov 14 2013Dec 18 2013Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z~6.4, a limit set ... More
Co-substitution effects on the Fe-valence in the BaFe2As2 superconducting compound: A study of hard x-ray absorption spectroscopyJul 05 2011Dec 20 2011The Fe K X-ray absorption near edge structure (XANES) of BaFe2-xCoxAs2 superconductors was investigated. No appreciable alteration in shape or energy position of this edge was observed with Co substitution. This result provides experimental support to ... More
Testing Comptonizing coronae on a long BeppoSAX observation of the Seyfert 1 galaxy NGC 5548Apr 10 2000We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548, allowing for different geometries of the scattering region, different temperatures of the input soft photon field and different viewing ... More
A direct approach to Plateau's problem in any codimensionJan 28 2015This paper aims to propose a direct approach to solve the Plateau's problem in codimension higher than one. The problem is formulated as the minimization of the Hausdorff measure among a family of $d$-rectifiable closed subsets of $\mathbb R^n$: following ... More
Rectifiability of varifolds with locally bounded first variation with respect to anisotropic surface energiesSep 07 2016Nov 14 2016We extend Allard's celebrated rectifiability theorem to the setting of varifolds with locally bounded first variation with respect to an anisotropic integrand. In particular, we identify a sufficient and necessary condition on the integrand to obtain ... More
A direct approach to the anisotropic Plateau's problemFeb 28 2016We prove a compactness principle for the anisotropic formulation of the Plateau's problem in codimension one, along the same lines of previous works of the authors [DGM14, DPDRG15]. In particular, we perform a new strategy for proving the rectifiability ... More
Ill-posedness of Leray solutions for the ipodissipative Navier-Stokes equationsAug 17 2017We prove the ill-posedness of Leray solutions to the Cauchy problem for the ipodissipative Navier--Stokes equations, when the dissipative term is a fractional Laplacian $(-\Delta)^\alpha$ with exponent $\alpha < \frac{1}{5}$. The proof follows the ''convex ... More
The Area Blow Up set for bounded mean curvature submanifolds with respect to elliptic surface energy functionalsJan 11 2019In this paper we investigate the "area blow-up" set of a sequence of smooth co-dimension one manifolds whose first variation with respect to an anisotropic integral is bounded. Following the ideas introduced by White in (J. Differential Geom., 2016), ... More
Testing Comptonisation models using BeppoSAX observations of Seyfert 1 galaxiesApr 11 2001We have used realistic Comptonization models to fit high quality BeppoSAX data of 6 Seyfert galaxies. Our main effort was to adopt a Comptonization model taking into account the anisotropy of the soft photon field. The most important consequence is a ... More
Testing Comptonization models using BeppoSAX observations of Seyfert 1 galaxiesJan 13 2001We used high quality BeppoSAX data of 6 Seyfert galaxies to test realistic thermal Comptonization models. Our main effort was to adopt a Comptonization model taking into account the anisotropy of the soft photon field. The best fit parameter values of ... More
A Self-Consistent Test of Comptonisation Models Using Bepposax Observations of Seyfert GalaxiesJun 27 2000We test accurate models of Comptonisation spectra over BeppoSAX observations of Seyfert galaxies focusing on the long look at NGC 5548. The hot plasma temperature derived with these models is significantly higher than that obtained fitting the same data ... More
Testing gravitational theories using Eccentric Eclipsing Detached BinariesJul 23 2012In this paper we compare the effects of different theories of gravitation on the apsidal motion of a sample of Eccentric Eclipsing Detached Binary stars. The comparison is performed by using the formalism of the Post-Newtonian parametrization to calculate ... More
Broad band spectral properties of Seyfert 1 galaxies observed with BeppoSAXAug 31 1999We will present some results on the broad--band observations of BeppoSAX of the bright Seyfert galaxies NGC 4151 and NGC 5548.
A self-consistent test of Comptonization models using a long BeppoSAX observation of NGC 5548Apr 10 2000We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548. The data are well represented by a plane parallel corona with an inclination angle of 30$^{\circ}$, a soft photon temperature of 5 eV and ... More
Bright [CII] and dust emission in three z>6.6 quasar host galaxies observed by ALMANov 23 2015We present ALMA detections of the [CII] 158 micron emission line and the underlying far-infrared continuum of three quasars at 6.6<z<6.9 selected from the VIKING survey. The [CII] line fluxes range between 1.6-3.4 Jy km/s ([CII] luminosities ~(1.9-3.9)x10^9 ... More
Existence results for minimizers of parametric elliptic functionalsApr 25 2017Feb 14 2019We prove a compactness principle for the anisotropic formulation of the Plateau problem in any codimension, in the same spirit of the previous works of the authors \cite{DelGhiMag,DePDeRGhi,DeLDeRGhi16}. In particular, we perform a new strategy for the ... More
Resonant particle production in branoniumNov 05 2007Apr 23 2008We study the mechanism of particle production in the world-volume of a probe anti D6-brane (or D6 with SUSY breaking) moving in the background created by a fixed stack of $D6$-branes. We show that this may occur in a regime of parametric resonance when ... More
Inflation in non-minimal matter-curvature coupling theoriesNov 07 2016We study inflationary scenarios driven by a scalar field in the presence of a non-minimal coupling between matter and curvature. We show that the Friedmann equation can be significantly modified when the energy density during inflation exceeds a critical ... More
Fluctuation-dissipation dynamics of cosmological scalar fieldsDec 17 2014May 05 2015We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within ... More
Can dark matter drive electroweak symmetry breaking?Nov 21 2018We consider the possibility of an oscillating scalar field accounting for dark matter and dynamically controlling the spontaneous breaking of the electroweak symmetry through a Higgs-portal coupling. This requires a late decay of the inflaton field, such ... More
The Changing-Look Quasar Mrk 590 is AwakeningOct 15 2018Mrk 590 was originally classified as a Seyfert 1 galaxy, but then it underwent dramatic changes: the nuclear luminosity dropped by over two orders of magnitude and the broad emission lines all but disappeared from the optical spectrum. Here we present ... More
The fate of high-redshift massive compact galaxiesJan 15 2016Feb 16 2016Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disk decomposition ... More
Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound statesOct 20 2011Feb 14 2012We study the propagation of a massive vector or Proca field on the Schwarzschild spacetime. The field equations are reduced to a one-dimensional wave equation for the odd-parity part of the field and two coupled equations for the even-parity part of the ... More
SO(10): a possible Scenario for new Physics in the Neutrino Sector and BaryogenesisMar 27 1995The implications on neutrino physics and on the dynamical generation of the baryonic asymmetry of a class of $SO(10)$ non-supersymmetric models are discussed.