Spacetime metric from linear electrodynamics

The Maxwell equations are formulated on an arbitrary (1+3)-dimensional manifold. Then, imposing a (constrained) linear constitutive relation between electromagnetic field $(E,B)$ and excitation $({\cal D},{\cal H})$, we derive the metric of spacetime therefrom.Comment: 4 pages' latex-scrip

The fitting of multifunctions : an approach to nonparametric multimodal regression.

In the last decades a lot of research has been devoted to smoothing in the sense of nonparametric regression. However, this work has nearly exclusively concentrated on fitting regression functions. When the conditional distribution of y|x is multimodal, the assumption of a functional relationship y = m(x) + noise might be too restrictive. We introduce a nonparametric approach to fit multifunctions, allowing to assign a set of output values to a given x. The concept is based on conditional mean shift, which is an easily implemented tool to detect the local maxima of a conditional density function. The methodology is illustrated by environmental data examples

Wilson Fermions and Axion Electrodynamics in Optical Lattices

The formulation of massless relativistic fermions in lattice gauge theories is hampered by the fundamental problem of species doubling, namely, the rise of spurious fermions modifying the underlying physics. A suitable tailoring of the fermion masses prevents such abundance of species, and leads to the so-called Wilson fermions. Here we show that ultracold atoms provide us with the first controllable realization of these paradigmatic fermions, thus generating a quantum simulator of fermionic lattice gauge theories. We describe a novel scheme that exploits laser-assisted tunneling in a cubic optical superlattice to design the Wilson fermion masses. The high versatility of this proposal allows us to explore a variety of interesting phases in three-dimensional topological insulators, and to test the remarkable predictions of axion electrodynamics.Comment: RevTex4 file, color figures, slightly longer than the published versio

Pairing of 1D Bose-Fermi mixtures with unequal masses

We have considered one-dimensional Bose-Fermi mixture with equal densities and unequal masses using numerical density matrix renormalization group (DMRG). For the mass ratio of K-Rb mixture and attraction between bosons and fermions, we determined the phase diagram. For weak boson-boson interactions, there is a direct transition between two-component Luttinger liquid and collapsed phases as the boson-fermion attraction is increased. For strong enough boson-boson interactions, we find an intermediate "paired" phase, which is a single-component Luttinger liquid of composite particles. We investigated correlation functions of such a "paired" phase, studied the stability of "paired" phase to density imbalance, and discussed various experimental techniques which can be used to detect it.Comment: 7 pages, 5 figure

Naturwall: active timber wall for renovation of existent buildings

The renovation of old buildings is actually the challenge to cope with increased effort in order to reduce climate global change, channeling more investment and awareness in this sense, defining more experimentations and find innovative solutions. The difficulty of carrying out an intervention on the existing buildings necessarily arise from the lack of information on the existing structure and the lack of coordinated processes between the multidisciplinary skills involved, as well as a difficulty to optimize the process that would make it even more competitive on the renovation work instead on the new construction. Naturwall is an innovative energy saving system for existent buildings by using wood in multifunctional components able to mitigate the environmental effort in building management. The project meant to introduce an industrialized design method in the renovation of existing build environment that highlights opportunities gave by "off site" production and parametric design approach, without neglecting the aesthetical values and the possibility to change the architectural image of residential and non residential constructions. The project aims to create a representative model of solution that will be promoted in Italy and widespread in other similar contex

Stripe-tetragonal phase transition in the 2D Ising model with dipole interactions: Partition-function zeros approach

We have performed multicanonical simulations to study the critical behavior of the two-dimensional Ising model with dipole interactions. This study concerns the thermodynamic phase transitions in the range of the interaction \delta where the phase characterized by striped configurations of width h=1 is observed. Controversial results obtained from local update algorithms have been reported for this region, including the claimed existence of a second-order phase transition line that becomes first order above a tricritical point located somewhere between \delta=0.85 and 1. Our analysis relies on the complex partition function zeros obtained with high statistics from multicanonical simulations. Finite size scaling relations for the leading partition function zeros yield critical exponents \nu that are clearly consistent with a single second-order phase transition line, thus excluding such tricritical point in that region of the phase diagram. This conclusion is further supported by analysis of the specific heat and susceptibility of the orientational order parameter.Comment: to appear in Phys. Rev.

Fundamentals of color teaching in post-graduate education

In this research we present a framework on the theory of color culture and science education in the context of a master program in Color De sign & Technology organized in Italy since 2014. Th e master is organize d in three main phases Fundamentals, Project Work and Internship. The first phase is composed of lectures and theoretical lessons that gives the students a base from theory and technique, relating to disciplines such as physics, optics, colorimetry, psych ology and perception . Fundamentals give all the base knowledge that the students are then asked to integrate in the project works, to propose and develop color projects for different design assignments , and in the Internship, that establish a link between the academia and compan ies who work with color in various fields like design, architecture, textiles and paints. Here the F undamentals will allow the students to build up their future professional experience in the chosen field

The pseudomorphic to bulk fcc phase transition of thin Ni films on Pd(100)

We have measured the transformation of pseudomorphic Ni films on Pd(100) into their bulk fcc phase as a function of the film thickness. We made use of x-ray diffraction and x-ray induced photoemission to study the evolution of the Ni film and its interface with the substrate. The growth of a pseudomorphic film with tetragonally strained face centered symmetry (fct) has been observed by out-of-plane x-ray diffraction up to a maximum thickness of 10 Ni layers (two of them intermixed with the substrate), where a new fcc bulk-like phase is formed. After the formation of the bulk-like Ni domains, we observed the pseudomorphic fct domains to disappear preserving the number of layers and their spacing. The phase transition thus proceeds via lateral growth of the bulk-like phase within the pseudomorphic one, i.e. the bulk-like fcc domains penetrate down to the substrate when formed. This large depth of the walls separating the domains of different phases is also indicated by the strong increase of the intermixing at the substrate-film interface, which starts at the onset of the transition and continues at even larger thickness. The bulk-like fcc phase is also slightly strained; its relaxation towards the orthomorphic lattice structure proceeds slowly with the film thickness, being not yet completed at the maximum thickness presently studied of 30 Angstrom (i.e. about 17 layers).Comment: 8 pages, 7 figure

Spatial–Spectral Evidence of Glare Influence on Hyperspectral Acquisitions

Glare is an unwanted optical phenomenon which affects imaging systems with optics. This paper presents for the first time a set of hyperspectral image (HSI) acquisitions and measurements to verify how glare affects acquired HSI data in standard conditions. We acquired two ColorCheckers (CCs) in three different lighting conditions, with different backgrounds, different exposure times, and different orientations. The reflectance spectra obtained from the imaging system have been compared to pointwise reference measures obtained with contact spectrophotometers. To assess and identify the influence of glare, we present the Glare Effect (GE) index, which compares the contrast of the grayscale patches of the CC in the hyperspectral images with the contrast of the reference spectra of the same patches. We evaluate, in both spatial and spectral domains, the amount of glare affecting every hyperspectral image in each acquisition scenario, clearly evidencing an unwanted light contribution to the reflectance spectra of each point, which increases especially for darker pixels and pixels close to light sources or bright patche