Monitoring and understanding crustal deformation by means of GPS and InSAR data

Monitoring deformation of the Earth’s crust by using data acquired by both the GNSS and SAR techniques allows describing crustal movements with high spatial and temporal resolution. This is a key contribution for achieving a deeper and better insight of geodynamic processes. Combination of the two techniques provides a very powerful means, however, before combing the different data sets it is important to properly understand their respective contribution. For this purpose, strictly simultaneous and long time series would be necessary. This is not, in general, a common case due to the relatively long SAR satellites revisit time. A positive exception is represented by the data set of COSMO SKYMed (CSK) images made available for this study by the Italian Space Agency (ASI). The flyover area encompass the city of Bologna and the smaller nearby town of Medicina where permanent GPS stations are operational. At the times of the CSK flyovers, we compared the GPS and SAR Up and East coordinates of a few stations as well as differential tropospheric delays derived by both techniques. The GPS time series were carefully screened and corrected for the presence of discontinuities by adopting a dedicated statistical procedure. The comparisons of both the estimated deformation and the tropospheric delays are encouraging and highlight the need for having available a more evenly sampled SAR data set

Designing the master schedule for demand-adaptive transit systems

Abstract Demand-Adaptive Systems (DAS) display features of both traditional fixed-line bus services and purely on-demand systems such as dial-a-ride, that is they offer demand-responsive services within the framework of traditional scheduled bus transportation. A DAS bus line serves, on one hand, a given set of compulsory stops according to a predefined schedule specifying the time windows associated with each, providing the traditional use of the transit line, without requiring any reservation. On the other hand, passengers may also issue requests for transportation between two desired, optional, stops, which induces detours in the vehicle routes. The design of a DAS line is a complex planning operation that requires to determine not only its design in terms of selecting the compulsory stops, but also its master schedule in terms of the time windows associated with the compulsory stops. Designing a DAS thus combines elements of strategic and tactical planning. In this paper we focus on determining a master-schedule for a single DAS line. We propose a mathematical description and a solution framework based on the estimation of a number of statistical parameters of the demand and the DAS line service. Results of numerical experiments are also given and analyzed

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Space geodetic activities, from the early days to present, with focus on the northeastern Adriatic

It has become of greatest importance to monitor and understand how the dynamics of the System Earth works. Geodesy has gone far beyond the provision of a static knowledge of the Earth\u2019s geometric and physical parameters and with the development of high-accuracy satellite and space techniques and increased measurement capability, this discipline is now providing observations of changes in the Earth\u2019s shape, gravity field and rotation which are essential for Earth system science. In a short historical excursus of the main space geodetic techniques, we review achievements in the determination and study of Earth\u2019s crustal deformation and sea-level change/variations. Focus is given to geodetic research activities developed in northeastern Italy

Towards designing flexible transportation system

http://transp-or2.epfl.ch/tristan/FullPapers/134Errico.pd

A Benders Decomposition Approach for the Symmetric TSP with Generalized Latency Arising in the Design of Semiflexible Transit Systems

We present the symmetric traveling salesman problem with generalized latency (TSP-GL) a new problem arising in the planning of the important class of semiflexible transit systems. The TSP-GL can be seen as a very challenging variant of the symmetric traveling salesman problem (S-TSP), where the objective function combines the usual cost of the circuit with a routing component accounting for the passenger travel times. The main contributions of the paper include the formulation of the problems in terms of mul- ticommodity flows, the study of its mathematical properties, and the introduction of a branch-and-cut approach based on Benders reformulation taking advantage of properties that relate the feasible region of the TSP-GL and the S-TSP polyhedron. An extensive com- putational experimentation compares a number of variants of the proposed algorithm, as well as a commercial solver. These experiments show that the method we propose signif- icantly outperforms a well-known commercial solver and obtains good-quality solutions to realistically sized instances within short computational times

A proposal for the evaluation of demand-adaptive transit systems

none4https://www.cirrelt.ca/DocumentsTravail/CIRRELT-2008-56.pdfnoneT. G. Crainic; F. Errico; F. Malucelli; M. NonatoT. G., Crainic; F., Errico; F., Malucelli; Nonato, Maddalen