Electromagnetic and Gravitational Waves on a de Sitter background

One of the longstanding problems of modern gravitational physics is the detection of gravitational waves, for which the standard theoretical analysis relies upon the split of the space-time metric into a background metric plus perturbation. However, as is well known, the background need not be Minkowskian in several cases of physical interest. Thus, we here investigate in more detail what happens if the background space-time has a non-vanishing Riemann curvature. In the case in which the de Donder gauge is imposed, its preservation under infinitesimal space-time diffeomorphisms is guaranteed if and only if the associated covector is ruled by a second-order hyperbolic operator. Moreover, since in this case the Ricci term of the wave equation has opposite sign with respect to the wave equation of Maxwell theory in the Lorenz gauge, it is possible to relate the solutions of the two problems. We solve completely the homogeneous vector wave equation of Maxwell theory in the Lorenz gauge when a de Sitter space-time is considered. The decoupling technique, analytic formulae and plots are original and have been first presented, in the literature, by Bini, Esposito and the author in Gen. Rel. Grav. 42, 51-61 (2010). Moreover, we solve explicitly the Einstein equations for metric perturbations on a de Sitter background. In fact, by using the Regge-Wheeler gauge, the coupled system of differential equations, to first-order in the metric perturbation, has been here solved in terms of the Heun general functions.Comment: 86 pages, 37 figures, Ph.D. thesis of the autho

Solution of Maxwell's equations on a de Sitter background

The Maxwell equations for the electromagnetic potential, supplemented by the Lorenz gauge condition, are decoupled and solved exactly in de Sitter space-time studied in static spherical coordinates. There is no source besides the background. One component of the vector field is expressed, in its radial part, through the solution of a fourth-order ordinary differential equation obeying given initial conditions. The other components of the vector field are then found by acting with lower-order differential operators on the solution of the fourth-order equation (while the transverse part is decoupled and solved exactly from the beginning). The whole four-vector potential is eventually expressed through hypergeometric functions and spherical harmonics. Its radial part is plotted for given choices of initial conditions. We have thus completely succeeded in solving the homogeneous vector wave equation for Maxwell theory in the Lorenz gauge when a de Sitter spacetime is considered, which is relevant both for inflationary cosmology and gravitational wave theory. The decoupling technique and analytic formulae and plots are completely original. This is an important step towards solving exactly the tensor wave equation in de Sitter space-time, which has important applications to the theory of gravitational waves about curved backgrounds.Comment: 11 pages, 5 figures, Latex. The presentation has been improved, and the title has been change

An Outline of A Concept of Operations fFor Integration of ATM and Air Transport into Multimodal Transport System for Door-fo-Door Travel

In the framework of the research activities supported by SESAR JU, dedicated research stream is devoted to investigation of integration of Air Traffic Management (ATM) and aviation into a wider transport system able to support the implementation of Door-to-Door (D2D) travel concept. In this framework, the project X-TEAM D2D (Extended ATM for Door-to-Door Travel) has been funded by SESAR JU under the call SESAR-ER4-10-2019: ATM Role in Intermodal Transport, with Grant Agreement n. 891061. The project aims defining, developing and initially validating a Concept of Operations (ConOps) for the seamless integration of ATM and air transport into an overall intermodal network, including other available transportation means (surface, water), to support the door-to-door connectivity, in up to 4 hours, between any location in Europe, in compliance with the target assigned by the ACARE SRIA FlightPath 2050 goals. The project is focused on the consideration of ConOps for ATM and air transport integration in intermodal transport network serving urban and extended urban (up to regional level) mobility, taking into account the transportation and passengers service scenarios envisaged for the next decades, according to baseline (2025), intermediate (2035) and final (2050) time horizons. In this paper, the outcomes of the first phase of the project activities, aimed to provide the initial definition (concept outline) of the proposed overall ConOps are illustrated, emphasizing the specific activities that have been carried out up to date and the related achievements. In addition, an outlook is provided in the paper on the next project activities, expected to be carried out towards the conclusion of the studies and the validation, by means of dedicated numerical simulation campaigns, of the proposed ConOps

EEG signal analysis for epileptic seizures detection by applying Data Mining techniques

seizures, which severely impact the quality of life of epilepsy patients and sometimes are accompanied by loss of consciousness. The most widely accepted and used tool by epileptologists to identify seizures and diagnose epilepsy is the ElectroEncephaloGram (EEG). Seizure detection on EEG signals is a long process, which is done manually by epileptologists. This paper describes how to analyze EEG signal using Data Mining methods and techniques with the main objective of automatically detect a seizure within EEG signals. We have designed and developed a multipurpose and extendable tool for feature extraction from time series data, named Training Builder. Our trained classifier, based on signal processing, sliding window paradigm, features extraction and selection, and Support Vector Machines, showed excellent results, reaching an accuracy of over 99% during the test made on publicly available EEG datasets

X-TEAM D2D Project: Designing and Validating a Concept of Operations for Door-To-Door Multimodal Transport

The project X-TEAM D2D (extended ATM for door-to-door travel) has been funded by SESAR JU in the framework of the research activities devoted to the investigation of integration of Air Traffic Management (ATM) and aviation into a wider transport system able to support the implementation of the door-to-door (D2D) travel concept. The project defines a concept for the seamless integration of ATM and Air Transport into an intermodal network, including other available transportation means, such as surface and waterways, to contribute to the 4 h door-to-door connectivity targeted by the European Commission in the ACARE SRIA FlightPath 2050 goals. In particular, the project focused on the design of a concept of operations for urban and extended urban (up to regional) integrated mobility, taking into account the evolution of transportation and passengers service scenarios for the next decades, according to baseline (2025), intermediate (2035) and final target (2050) time horizons. The designed ConOps encompassed both the transportation platforms integration concepts and the innovative seamless Mobility as a Service, integrating emerging technologies, such as Urban Air Mobility (e.g., electric vertical take-off and landing vehicles) and new mobility forms (e.g., micromobility vehicles) into the intermodal traffic network, including Air Traffic Management (ATM) and Unmanned Traffic Management (UTM). The developed concept has been evaluated against existing KPAs and KPIs, implementing both qualitative and quantitative performance assessment approaches, while also considering specific performance metrics related to transport integration efficiency from the passenger point of view, being the proposed solution designed to be centered around the passenger needs. The aim of this paper is to provide a description of the activities carried out in the project and to present at high level the related outcomes