Probing Extreme-Density Matter with Gravitational Wave Observations of Binary Neutron Star Merger Remnants

We present a proof-of-concept study, based on numerical-relativity simulations, of how gravitational waves (GWs) from neutron star merger remnants can probe the nature of matter at extreme densities. Phase transitions and extra degrees of freedom can emerge at densities beyond those reached during the inspiral, and typically result in a softening of the equation of state (EOS). We show that such physical effects change the qualitative dynamics of the remnant evolution, but they are not identifiable as a signature in the GW frequency, with the exception of possible black-hole formation effects. The EOS softening is, instead, encoded in the GW luminosity and phase and is in principle detectable up to distances of the order of several Mpcs with advanced detectors and up to hundreds of Mpcs with third generation detectors. Probing extreme-density matter will require going beyond the current paradigm and developing a more holistic strategy for modeling and analyzing postmerger GW signals.Comment: 5 pages, 3 figures. Matches version accepted on ApJ

TIGER: A data analysis pipeline for testing the strong-field dynamics of general relativity with gravitational wave signals from coalescing compact binaries

The direct detection of gravitational waves with upcoming second-generation gravitational wave detectors such as Advanced LIGO and Virgo will allow us to probe the genuinely strong-field dynamics of general relativity (GR) for the first time. We present a data analysis pipeline called TIGER (Test Infrastructure for GEneral Relativity), which is designed to utilize detections of compact binary coalescences to test GR in this regime. TIGER is a model-independent test of GR itself, in that it is not necessary to compare with any specific alternative theory. It performs Bayesian inference on two hypotheses: the GR hypothesis $\mathcal{H}_{\rm GR}$, and $\mathcal{H}_{\rm modGR}$, which states that one or more of the post-Newtonian coefficients in the waveform are not as predicted by GR. By the use of multiple sub-hypotheses of $\mathcal{H}_{\rm modGR}$, in each of which a different number of parameterized deformations of the GR phase are allowed, an arbitrarily large number of 'testing parameters' can be used without having to worry about a model being insufficiently parsimonious if the true number of extra parameters is in fact small. TIGER is well-suited to the regime where most sources have low signal-to-noise ratios, again through the use of these sub-hypotheses. Information from multiple sources can trivially be combined, leading to a stronger test. We focus on binary neutron star coalescences, for which sufficiently accurate waveform models are available that can be generated fast enough on a computer to be fit for use in Bayesian inference. We show that the pipeline is robust against a number of fundamental, astrophysical, and instrumental effects, such as differences between waveform approximants, a limited number of post-Newtonian phase contributions being known, the effects of neutron star spins and tidal deformability on the orbital motion, and instrumental calibration errors.Comment: 12 pages, 9 figures. Version as appears in Phys. Rev.

Cosmological inference using only gravitational wave observations of binary neutron stars

Gravitational waves emitted during the coalescence of binary neutron star systems are self-calibrating signals. As such, they can provide a direct measurement of the luminosity distance to a source without the need for a cross-calibrated cosmic distance-scale ladder. In general, however, the corresponding redshift measurement needs to be obtained via electromagnetic observations since it is totally degenerate with the total mass of the system. Nevertheless, Fisher matrix studies have shown that, if information about the equation of state of the neutron stars is available, it is possible to extract redshift information from the gravitational wave signal alone. Therefore, measuring the cosmological parameters in pure gravitational-wave fashion is possible. Furthermore, the huge number of sources potentially observable by the Einstein Telescope has led to speculations that the gravitational wave measurement is potentially competitive with traditional methods. The Einstein Telescope is a conceptual study for a third generation gravitational wave detector which is designed to yield 10^3–10^7 detections of binary neutron star systems per year. This study presents the first Bayesian investigation of the accuracy with which the cosmological parameters can be measured using information coming only from the gravitational wave observations of binary neutron star systems by the Einstein Telescope. We find, by direct simulation of 10^3 detections of binary neutron stars, that, within our simplifying assumptions, H_0, Ω_m, Ω_Λ, w_0 and w_1 can be measured at the 95% level with an accuracy of ∼8% , 65%, 39%, 80% and 90%, respectively. We also find, by extrapolation, that a measurement accuracy comparable with current measurements by Planck is possible if the number of gravitational wave events observed is O(10^(6–7)) . We conclude that, while not competitive with electromagnetic missions in terms of significant digits, gravitational waves alone are capable of providing a complementary determination of the dynamics of the Universe

Cosmological inference using only gravitational wave observations of binary neutron stars

Gravitational waves emitted during the coalescence of binary neutron star systems are self- calibrating signals. As such, they can provide a direct measurement of the luminosity distance to a source without the need for a cross-calibrated cosmic distance-scale ladder. In general, how- ever, the corresponding redshift measurement needs to be obtained via electromagnetic observations since it is totally degenerate with the total mass of the system. Nevertheless, Fisher matrix studies have shown that, if information about the equation of state of the neutron stars is available, it is possible to extract redshift information from the gravitational wave signal alone. Therefore, measuring the cosmological parameters in pure gravitational-wave fashion is possible. Furthermore, the huge number of sources potentially observable by the Einstein Telescope has led to speculations that the gravitational wave measurement is potentially competitive with traditional methods. The Einstein Telescope is a conceptual study for a third generation gravitational wave detector which is designed to yield 103 − 107 detections of binary neutron star systems per year. This study presents the first Bayesian investigation of the accuracy with which the cosmological parameters can be measured using information coming only from the gravitational wave observations of binary neutron star systems by Einstein Telescope. We find, by direct simulation of 103 detections of binary neutron stars, that, within our simplifying assumptions, H0, Ωm, ΩΛ, w0 and w1 can be measured at the 95% level with an accuracy of ∼ 8%,65%,39%,80% and 90%, respectively. We also find, by extrapolation, that a measurement accuracy comparable with current measurements by Planck is possible if the number of gravitational wave events observed is O(10^{6−7}).We conclude that, while not competitive with electro-magnetic missions in terms of significant digits, gravitational wave alone are capable of providing a complementary determination of the dynamics of the Universe

Trasporti e turismo in epoca di emergenza sanitaria Covid-19. Il caso dei vouchers in alternativa ai rimborsi in denaro di titoli di viaggio, di soggiorno e di pacchetti turistici.

Il lavoro esamina brevemente l'impatto dell'attuale emergenza sanitaria COVID-19, che ha portato a restrizioni di viaggio in tutto il mondo senza precedenti e ha causato quasi un arresto dei viaggi in Europa, su vettori, organizzatori di pacchetti turistici e fornitori di altri servizi turistici come parte di pacchetti turistici. Ci\uf2 nonostante, l'attuale normativa dell'UE, che prevede una serie di diritti per passeggeri e viaggiatori, rimane pienamente applicabile. In base a tale normativa, in caso di cancellazione di un viaggio o di un pacchetto turistico, i passeggeri e i viaggiatori hanno diritto a ottenere un rimborso. Tale rimborso pu\uf2 essere effettuato tramite un voucher, ma solo con l\u2019accordo del consumatore. Ebbene, in Italia l'articolo 88-bis del d.l. 18/2020 non offre ai passeggeri e ai viaggiatori la scelta tra il rimborso in contanti e il rimborso sotto forma di buoni. L'articolo esamina i profili di contrasto tra tale disposizione nazionale e le norme nonch\ue9 i principi generali dell'UE.The work briefly examines the impact of the current COVID-19 health emergency, which has led to unprecedented worldwide travel restrictions and have caused almost a standstill of travels in Europe, on carriers, organisers of package tours and providers of other tourism services as part of package tours. Nonetheless, the current EU legislation, which provides for a set of rights for passengers and travelers, remains fully applicable. According to such legislation, in the event of a cancellation by the carrier or if a package trip is cancelled, passengers and travelers have the right to obtain a reimbursement. Such reimbursement can be made by means of a voucher only if the consumer agrees. Well, in Italy Article 88-bis of law decree 18/2020 doesn\u2019t give passengers and travelers the choice between cash reimbursement and reimbursement in the form of a voucher. The article questions if such national provision is incompatible with EU law and general principles

FORCE- AND POWER-TIME RELATIONSHIP,EMG RESPONSES IN CONCENTRIG AND ISOMETRIC CONDITIONS,EFFECTS OF TRAINING AND INDIVIDUAL CRARACTERISTICS

Introduction The relationship between EHG (temporal pattern, IEMG, power spectra ) and the biomechanical parameter in isometric and dynamic muscle tension represents an essential method in the analysis of the specificity of training effects and of the individual characteristics in motor control modelling and in practical motor learning. METHODS Force-time, power-time relationships under concentric and isometric conditions (MVC) with and without preloading were determined. For EHG purpose, surface electrodes (O= 5 mm; interelectrode distance 40 mm) were placed over the belly of each muscle (Tric.br.;Bic.br.; Delt.an.; Pect.ma.). Bipolar myoelectrical potentials were recorded with the passive electrode placed between the two actives: signals were preamplified and band-pass filtered (CMRRT 70 db, BP= 10 Hz- 1 KHz: Zin=1,5 MR. gain= 1000). EMG signals and the force were digitized on-line with a sampling frequency of 1000 Hz. For time structure analysis EMG signals were full-wave rectified and bandpass filtered (20-70 Hz) to obtain envelop curve patterns of each muscle. Power spectra analysis (median frequency MF) were performed using 1024 and pl2 data points. 3 groups (n=4) of sport students were involved in the investigation. Subjects performed a 8 week training period under different loading conditions. RESULTS # In the concentric tasks subjects show individual strategies in the muscular coordination patterns dependent on the load intensity. # Differences in the muscular interactivity pattern are not necessarily matching similar variation in the mechanical output. # For increasing loads there is a linear relationship between muscular activation level and mechanical power output. # In the power spectra, trends are consistent but also discontinuous. Median frequency could possibly indicate that some subjects have resources in motor units recruitment . # Other considerations are discussed referring to the muscular activation and the isometric MVC under preloading conditions

A Mock Data Challenge for the Einstein Gravitational-Wave Telescope

Einstein Telescope (ET) is conceived to be a third generation gravitational-wave observatory. Its amplitude sensitivity would be a factor ten better than advanced LIGO and Virgo and it could also extend the low-frequency sensitivity down to 1--3 Hz, compared to the 10--20 Hz of advanced detectors. Such an observatory will have the potential to observe a variety of different GW sources, including compact binary systems at cosmological distances. ET's expected reach for binary neutron star (BNS) coalescences is out to redshift $z\simeq 2$ and the rate of detectable BNS coalescences could be as high as one every few tens or hundreds of seconds, each lasting up to several days. %in the sensitive frequency band of ET. With such a signal-rich environment, a key question in data analysis is whether overlapping signals can be discriminated. In this paper we simulate the GW signals from a cosmological population of BNS and ask the following questions: Does this population create a confusion background that limits ET's ability to detect foreground sources? How efficient are current algorithms in discriminating overlapping BNS signals? Is it possible to discern the presence of a population of signals in the data by cross-correlating data from different detectors in the ET observatory? We find that algorithms currently used to analyze LIGO and Virgo data are already powerful enough to detect the sources expected in ET, but new algorithms are required to fully exploit ET data.Comment: accepted for publication in Physical Review D -- 18 pages, 8 figure