Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds

Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as $m_g < 1.2 \times 10^{-22}$ eV (Abbott et al., 2016). In the paper we analyze a potential to reduce upper bounds for graviton mass with future observational data on trajectories of bright stars near the Galactic Center. Since gravitational potentials are different for these two cases, expressions for relativistic advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume that trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. In contrast with our previous studies, where we present current constraints on parameters of Yukawa gravity (Borka et al., 2013) and graviton mass (Zakharov et al., 2016) from observations of S2 star, in the paper we express expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations. We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around $5 \times 10^{-23}$ eV or slightly better than current estimates obtained with LIGO observations.Comment: 16 pages, 1 Figure, 1 Table, corrected minor typo

Dynamics of the wakefield of a multi-petawatt, femtosecond laser pulse in a configuration with ultrarelativistic electrons

The wake field excitation in an unmagnetized plasma by a multi-petawatt, femtosecond, pancake-shaped laser pulse is described both analytically and numerically in the regime with ultrarelativistic electron jitter velocities, when the plasma electrons are almost expelled from the pulse region. This is done, for the first time, in fluid theory. A novel mathematical model is devised that does not break down for very intense pump strengths, in contrast to the standard approach that uses the laser field envelope and the ponderomotive guiding center averaging. This is accomplished by employing a three-timescale description, with the intermediate scale associated with the nonlinear phase of the electromagnetic wave and with the bending of its wave front. The evolution of the pulse and of its electrostatic wake are studied by the numerical solution in a two-dimensional geometry, with the spot diameter \geq 100 microns. It reveals that the optimum initial pulse length needs to be somewhat bigger than 1 micron (1-2 oscillations), as suggested by simple analytical local estimates, because the nonlocal plasma response tends to stretch very short pulses

Physical model of quantum-well infrared photodetectors

A fully quantum mechanical model for electron transport in quantum well infrared photodetectors is presented, based on a self-consistent solution of the coupled rate equations. The important macroscopic parameters like current density, responsivity and capture probability can be estimated directly from this first principles calculation. The applicability of the model was tested by comparison with experimental measurements from a GaAs/AlGaAs device, and good agreement was found. The model is general and can be applied to any other material system or QWIP design

FROM QGIS TO PYTHON: COMPARISON OF FREE AND OPEN TOOLS FOR STATISTICAL ANALYSIS OF CULTURAL HERITAGE AND DATA REPRESENTATION

The onset of the Covid pandemic in 2020 changed the approach to work, research, and study. This period has been a wake-up call for public administrations, the private sector, and the academic community, to digitise their data. In Italy, digital and information technologies for the protection and enhancement of cultural heritage, which were an imperative for more than a decade, have been accelerated. This paper aims to collect and to process openly available data on patrimony from OpenStreetMap and the Lombardian Geoportal. The study is divided into two phases: a simple statistical analysis of cultural heritage in Monza is obtained, and the results are presented graphically. Firstly, built-in tools and Python Console of QGIS are evaluated, to filter attributes and add geometrical values to the downloaded material. Secondly, plug-in DataPlotly and an online coding application named Replit are assessed. The results are presented and compared in terms of their flexibility, quality of visual representation, customisation, and simplicity of use. Tools developed through and for QGIS are easy to use and available to everyone. Additionally, coding applications can be integrated for more refined results. This approach fosters interdisciplinarity, bridges the gap between professionals and non-expert users of GIS, and opens a range of opportunities for future collaborations. The citizen, as a mapper, can be involved in the administrative decision-making process, contributing with data collected in situ. Collaboration between these two sides can potentially produce the better for evaluating the contemporary built environment and its undividable part of cultural heritage

DRAWINGS FOR THE REUSE OF NINETEENTH CENTURY GREENHOUSES IN THE GARDEN OF VILLA CICOGNA MOZZONI

The nineteenth-century greenhouses in the garden of Villa Cicogna Mozzoni are abandoned and dilapidated. Three greenhouses investigated for the research named A, B and C are positioned one above the other on the hill of the garden. They are historical examples of iron and glass structures with masonry walls leaning against the ground. They have undergone numerous modifications over time, as evidenced by archival documents. To create a preservation project for their reuse, bibliographical research was first collected. Secondly, direct and indirect surveys were carried out. The technical drawings were produced on a 1:50 scale using point clouds, orthophotos, sketches and direct measurements. Given the nature of the glass material of which these buildings are predominantly made, it was necessary to process the data obtained with the laser scanner and clean created noise points. Seemingly simple structures, greenhouses are complex buildings that require careful studies of humidity, temperature, irrigation, light and materials. For the presentation of different systems in the greenhouses, color-coded thematical drawings were created. Detailed drawings on a 1:20 scale examine the iron fixtures and manual mechanical system of the windows. Other characteristics were represented in the drawings, such as internal and external movements and communications between greenhouses. The survey and documentation were done to serve for the reuse project which aims to bring back the shine to these greenhouses so that they can be revitalized for botanical and educational activities

Optically pumped intersublevel midinfrared lasers based on InAs-GaAs quantum dots

We propose an optically pumped laser based on intersublevel transitions in InAs-GaAs pyramidal self-Assembled quantum dots. A theoretical rate equations model of the laser is given in order to predict the dependence of the gain on pumping flux and temperature. The energy levels and wave functions were calculated using the 8-band k . p method where the symmetry of the pyramid was exploited to reduce the computational complexity. Carrier dynamics in the laser were modeled by taking both electron-longitudinal optical phonon and electron-longitudinal acoustic phonon interactions into account. The proposed laser emits at 14.6 μm with a gain of g ≈ 570 cm(-1) at the pumping flux Φ= 10(24) cm(-2) s(-1) and a temperature of T = 77 K. By varying the size of the investigated dots, laser emission in the spectral range 13-21 μm is predicted. In comparison to optically pumped lasers based on quantum wells, an advantage of the proposed type of laser is a lower pumping flux, due to the longer carrier lifetime in quantum dots, and also that both surface and edge emission are possible. The appropriate waveguide and cavity designs are presented, and by comparing the calculated values of the gain with the estimated losses, lasing is predicted even at room temperature for all the quantum dots investigated

Investigation of thermal effects in quantum-cascade lasers

The development of a thermal model for quantum cascade lasers (QCLs) is presented. The model is used in conjunction with a self-consistent scattering rate calculation of the electron dynamics of an InGaAs-AlAsSb QCL to calculate the temperature distribution throughout the device which can be a limiting factor for high temperature operation. The model is used to investigate the effects of various driving conditions and device geometries, such as epilayer down bonding and buried heterostructures, on the active region temperature. It is found that buried heterostructures have a factor of eight decrease in thermal time constants compared to standard ridge waveguide structures in pulsed mode and allow a /spl sim/78% increase in heat sink temperature compared to epilayer down mounted devices in continuous-wave mode. The model presented provides a valuable tool for understanding the thermal dynamics inside a quantum cascade laser and will help to improve their operating temperatures

Evaluation of semiconductor devices for Electric and Hybrid Vehicle (EHV) ac-drive applications, volume 1

The results of evaluation of power semiconductor devices for electric hybrid vehicle ac drive applications are summarized. Three types of power devices are evaluated in the effort: high power bipolar or Darlington transistors, power MOSFETs, and asymmetric silicon control rectifiers (ASCR). The Bipolar transistors, including discrete device and Darlington devices, range from 100 A to 400 A and from 400 V to 900 V. These devices are currently used as key switching elements inverters for ac motor drive applications. Power MOSFETs, on the other hand, are much smaller in current rating. For the 400 V device, the current rating is limited to 25 A. For the main drive of an electric vehicle, device paralleling is normally needed to achieve practical power level. For other electric vehicle (EV) related applications such as battery charger circuit, however, MOSFET is advantageous to other devices because of drive circuit simplicity and high frequency capability. Asymmetrical SCR is basically a SCR device and needs commutation circuit for turn off. However, the device poses several advantages, i.e., low conduction drop and low cost