553 research outputs found
INTERNATIONAL SCHOOL ON ASTROPHYSICAL RELATIVITY "John Archibald Wheeler", ERICE
No full textI. CIUFOLINI e' il direttore, con R. Matzner, della scuola "INTERNATIONAL SCHOOL ON ASTROPHYSICAL RELATIVITY "John Archibald Wheeler" di Erice (e' stato anche il direttore del primo corso nel 2006)
General Relativity and John Archibald Wheeler.
No full textObservational and experimental data pertaining to gravity and cosmology are changing our view of the Universe. General relativity is a fundamental key for the understanding of these observations and its theory is undergoing a continuing enhancement of its intersection with observational and experimental data. These data include direct observations and experiments carried out in our solar system, among which there are direct gravitational wave astronomy, frame dragging and tests of gravitational theories from solar system and spacecraft observations. This book explores John Archibald Wheeler's seminal and enduring contributions in relativistic astrophysics and includes: the General Theory of Relativity and Wheeler's influence; recent developments in the confrontation of relativity with experiments; the theory describing gravitational radiation, and its detection in Earth-based and space-based interferometer detectors as well as in Earth-based bar detectors; the mathematical description of the initial value problem in relativity and applications to modeling gravitational wave sources via computational relativity; the phenomenon of frame dragging and its measurement by satellite observations. All of these areas were of direct interest to Professor John A. Wheeler and were seminally influenced by his ideas
First Course of the INTERNATIONAL SCHOOL ON ASTROPHYSICAL RELATIVITY "John Archibald Wheeler", ERICE
No full textI. CIUFOLINI e' stato il direttore del primo CORSO della scuola: INTERNATIONAL SCHOOL ON ASTROPHYSICAL RELATIVITY "John Archibald Wheeler" ad Eric
International School of Astrophysical Relativity “John Archibald Wheeler” (Ettore Majorana Centre, Erice)
No full textOrganizzazione e direzione della International School of Astrophysical Relativity “John Archibald Wheeler” (Ettore Majorana Centre, Erice
Frontiers in numerical gravitational astrophysics
No full textThis Course has the scope to gather some of the best experts in computational simulations for the study of gravitating systems in astrophysics, to allow them to present their knowledge and expertise to deeply motivated students at the graduate level, as well as young researchers.
The main aim of the Course is that of clarifying whether and when the classic Newtonian approach fails and General Relativity is needed to approach reliably the complicated non-linear aspects of the physics involved. Consequently, the differences in the numerical and computational schemes approaches in the classic and relativistic cases will be illustrated and discussed. A small fraction of time is dedicated to the handling and visualization of the huge amount of data output
A new laser-ranged satellite for General Relativity and space geodesy: III. De Sitter effect and the LARES 2 space experiment
No full textIn two previous papers we presented the LARES 2 space experiment aimed at a very accurate test of frame-dragging and at other tests of fundamental physics and measurements of space geodesy and geodynamics. We presented the error sources of the LARES 2 experiment, its error budget and Monte Carlo simulations and covariance analyses confirming an accuracy of a few parts in one thousand in the test of frame-dragging. Here we discuss the impact of the orbital perturbation known as the de Sitter effect, or geodetic precession, in the error budget of the LARES 2 frame-dragging experiment. We show that the uncertainty in the de Sitter effect has a negligible impact in the final error budget because of the very accurate results now available for the test of the de Sitter precession and because of its very nature. The total error budget in the LARES 2 test of frame-dragging remains at a level of the order of 0.2 % , as determined in the first two papers of this series
Gamma Test Dataset
No full textThis set of data houses the 5000 graphs used for testing the gamma model that has been trained on the gamma dataset. It houses topologies generated via SNR-BA [1] with nodes scattered uniformly randomly with a minimum radius of 100km between them over a grid the size of north america. The throughput labels are calculated via maximising the routing and wavelength assignment with zero blocking using first-fit k-shortest-paths and implementing the physical layer impairments using the gaussian noise model.
[1] R. Matzner, D. Semrau, R. Luo, G. Zervas, and P. Bayvel, ‘Making intelligent topology design choices: understanding structural and physical property performance implications in optical networks [Invited]’, J. Opt. Commun. Netw., JOCN, vol. 13, no. 8, pp. D53–D67, Aug. 2021, doi: 10.1364/JOCN.423490.</p
The LARES Space Experiment: LARES Orbit, Error Analysis and Satellite Structure
No full textThe LARES space experiment, by the Italian Space Agency (ASI), is based on the launch of a new laser ranged satellite, called LARES (LAser RElativity Satellite), using the new launch vehicle VEGA (Veicolo Europeo di Generazione. Avanzata, provided by ESA). LARES will have an altitude of about 1,450 km, orbital inclination of about 71. 5∘ and nearly zero eccentricity. The LARES satellite together with the satellites LAGEOS (LAser GEOdynamics Satellite launched by NASA) and LAGEOS 2 (built by ASI and launched by NASA and ASI) and with improved GRACE (Gravity Recovery and Climate Experiment, a NASA/DLR, German Space Agency, mission) Earth’s gravity field models will allow a measurement of the Earth’s gravitomagnetic field and of Lense–Thirring effect with an uncertainty of a few percent. After a description of the LARES experiment and of the orbit of LARES, we present an analysis of the main error sources affecting the measurement of gravitomagnetism; these are due to the uncertainties in the Earth’s gravitational field, and in particular to the Earth’s even zonal harmonics, to the time dependent Earth’s gravitational field, and in particular to dot{J}6 and to the K 1 tide. We also discuss the effect of particle drag and the error due to the uncertainties in the measurement of the orbital inclination. We finally describe some technical and engineering aspects of the LARES mission, and in particular: the laser ranging technique, the cube corner reflectors and the satellite body. We conclude with a brief discussion of LARES separation system and the selected launcher
Alpha Test Datset
No full textThis set of data houses the 6000 graphs used for testing the beta model that has been trained on the beta dataset. It houses topologies generated via SNR-BA [1] with nodes scattered uniformly randomly with a minimum radius of 100km between them over a grid the size of north america. The throughput labels are calculated via maximising the routing and wavelength assignment with zero blocking using an integer linear programming formulation and implementing the physical layer impairments using the gaussian noise model.
[1] R. Matzner, D. Semrau, R. Luo, G. Zervas, and P. Bayvel, ‘Making intelligent topology design choices: understanding structural and physical property performance implications in optical networks [Invited]’, J. Opt. Commun. Netw., JOCN, vol. 13, no. 8, pp. D53–D67, Aug. 2021, doi: 10.1364/JOCN.423490.</p
Beta Test Dataset
No full textThis set of data houses the 5000 graphs used for testing the beta model that has been trained on the beta dataset. It houses topologies generated via SNR-BA [1] with nodes scattered uniformly randomly with a minimum radius of 100km between them over a grid the size of north america. The throughput labels are calculated via maximising the routing and wavelength assignment with zero blocking using first-fit k-shortest-paths and implementing the physical layer impairments using the gaussian noise model.
[1] R. Matzner, D. Semrau, R. Luo, G. Zervas, and P. Bayvel, ‘Making intelligent topology design choices: understanding structural and physical property performance implications in optical networks [Invited]’, J. Opt. Commun. Netw., JOCN, vol. 13, no. 8, pp. D53–D67, Aug. 2021, doi: 10.1364/JOCN.423490.
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