arXiv subjects

Giancarlo Cella

Publications and source records attributed to Giancarlo Cella.

13 recordsLinked to original sources

arXiv2026

Challenges and Opportunities of Gravitational Wave Searches above 10 kHz

The first direct measurement of gravitational waves by the LIGO and Virgo collaborations has opened up new avenues to explore our Universe. This white paper outlines the challenges and gains expected in gravitational-wave searches at frequencies above the LIGO/Virgo band. The scarcity of possible astrophysical sources in most of this frequency range provides a unique opportunity to discover physics beyond the Standard Model operating both in the early and late Universe, and we highlight some of the most promising of these sources. We review several detector concepts that have been proposed to take up this challenge, and compare their expected sensitivity with the signal strength predicted in various models. This report is the summary of a series of workshops on the topic of high-frequency gravitational wave detection, held in 2019 (ICTP, Trieste, Italy), 2021 (online) and 2023 (CERN, Geneva, Switzerland).

gr-qc↗

arXiv2023

Detecting non-Gaussian gravitational wave backgrounds: a unified framework

We describe a novel approach to the detection and parameter estimation of a non\textendash Gaussian stochastic background of gravitational waves. The method is based on the determination of relevant statistical parameters using importance sampling. We show that it is possible to improve the Gaussian detection statistics, by simulating realizations of the expected signal for a given model. While computationally expensive, our method improves the detection performance, leveraging the prior knowledge on the expected signal, and can be used in a natural way to extract physical information about the background. We present the basic principles of our approach, characterize the detection statistic performances in a simplified context and discuss possible applications to the detection of some astrophysical foregrounds. We argue that the proposed approach, complementarily to the ones available in literature might be used to detect suitable astrophysical foregrounds by currently operating and future gravitational wave detectors.

gr-qc↗

arXiv2023

Improved detection statistics for non Gaussian gravitational wave stochastic backgrounds

In a recent paper we described a novel approach to the detection and parameter estimation of a non-Gaussian stochastic background of gravitational waves. In this work we propose an improved version of the detection procedure, preserving robustness against imperfect noise knowledge at no cost of detection performance: in the previous approach, the solution proposed to ensure robustness reduced the performances of the detection statistics, which in some cases (namely, mild non-Gaussianity) could be outperformed by Gaussian ones established in literature. We show, through a simple toy model, that the new detection statistic performs better than the previous one (and than the Gaussian statistic) everywhere in the parameter space. It approaches the optimal Neyman-Pearson statistics monotonically with increasing non-Gaussianity and/or number of detectors. In this study we discuss in detail its efficiency. This is a second, important step towards the implementation of a nearly--optimal detection procedure for a realistic non-Gaussian stochastic background. We discuss the relevance of results obtained in the context of the toy model used, and their importance for understanding a more realistic scenario.

gr-qc↗

arXiv2022

Prospects for multi-messenger detection of binary neutron star mergers in the fourth LIGO-Virgo-KAGRA observing run

The joint detection of GW170817 and GRB 170817A opened the era of multi-messenger astronomy with gravitational waves (GWs) and provided the first direct probe that at least some binary neutron star (BNS) mergers are progenitors of short gamma-ray bursts (S-GRBs). In the next years, we expect to have more multi-messenger detections of BNS mergers, thanks to the increasing sensitivity of GW detectors. Here, we present a comprehensive study on the prospects for joint GW and electromagnetic observations of merging BNSs in the fourth LIGO--Virgo--KAGRA observing run with \emph{Fermi}, \emph{Swift}, INTEGRAL and SVOM. This work combines accurate population synthesis models with simulations of the expected GW signals and the associated S-GRBs, considering different assumptions about the GRB jet structure. We show that the expected rate of joint GW and electromagnetic detections could be up to $\sim$ 6 yr$^{-1}$ when \emph{Fermi}/GBM is considered. Future joint observations will help us to better constrain the association between BNS mergers and S-GRBs, as well as the geometry of the GRB jets.

astro-ph.HE↗

arXiv2021

Impact of a modified Entropy-Area law on Schwarzschild-de Sitter metric

Based on the perspective that continuum gravitational physics is an emergent quantum gravitational phenomenon, and that spacetime thermodynamic is the natural langauge in which it can be described, we derive a modified Schwarzschild-de Sitter geometry in static coordinates from quantum gravity inspired logarithmic corrections to the entropy-area law. The resulting quantum corrections to classical geometry can be encoded in explicitly radius dependent black hole and cosmological constant parameters. By considering the pure black hole case we study linear perturbations on this modified background, obtaining corrections to the black hole quasi-normal modes suppressed by the square of the ratio between the Planck length and the Schwarzschild radius.

gr-qc↗

arXiv2021

Searching for very-high-energy electromagnetic counterparts to gravitational-wave events with the Cherenkov Telescope Array

The detection of electromagnetic (EM) emission following the gravitational wave (GW) event GW170817 opened the era of multi-messenger astronomy with GWs and provided the first direct evidence that at least a fraction of binary neutron star (BNS) mergers are progenitors of short Gamma-Ray Bursts (GRBs). GRBs are also expected to emit very-high energy (VHE, > 100 GeV) photons, as proven by the recent MAGIC and H.E.S.S. observations. One of the challenges for future multi-messenger observations will be the detection of such VHE emission from GRBs in association with GWs. In the next years, the Cherenkov Telescope Array (CTA) will be a key instrument for the EM follow-up of GW events in the VHE range, owing to its unprecedented sensitivity, rapid response, and capability to monitor a large sky area via scan-mode operation. We present the CTA GW follow-up program, with a focus on the searches for short GRBs possibly associated with BNS mergers. We investigate the possible observational strategies and we outline the prospects for the detection of VHE EM counterparts to transient GW events.

astro-ph.HE↗

arXiv2019

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. This paper is based on a submission (v1) in response to the Call for White Papers for the Voyage 2050 long-term plan in the ESA Science Programme. ESA limited the number of White Paper authors to 30. However, in this version (v2) we have welcomed as supporting authors participants in the Workshop on Atomic Experiments for Dark Matter and Gravity Exploration held at CERN: ({\tt https://indico.cern.ch/event/830432/}), as well as other interested scientists, and have incorporated additional material.

gr-qc↗

arXiv2019

The gravitational-wave follow-up program of the Cherenkov Telescope Array

The birth of gravitational-wave / electromagnetic astronomy was heralded by the joint observation of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced LIGO and Advanced Virgo, GW170817, and of gamma-rays from the short gamma-ray burst GRB170817A by the Fermi Gamma-ray Burst Monitor (GBM) and INTEGRAL. This detection provided the first direct evidence that at least a fraction of BNSs are progenitors of short GRBs. GRBs are now also known to emit very-high-energy (VHE, > 100 GeV) photons as has been shown by recent independent detections of the GRBs 1901114C and 180720B by the ground-based gamma-ray detectors MAGIC and H.E.S.S. In the next years, the Cherenkov Telescope Array (CTA) will boost the searches for VHE counterparts thanks to its unprecedented sensitivity, rapid response and capability to monitor large sky areas via survey-mode operation. In this contribution, we present the CTA program of observations following the detection of GW events. We discuss various follow-up strategies and links to multi-wavelength and multi-messenger observations. Finally we outline the capabilities and prospects of detecting VHE emission from GW counterparts.

astro-ph.HE↗

arXiv2018

Searching for Gamma-Ray counterparts to Gravitational Waves from merging binary neutron stars with the Cherenkov Telescope Array

The merger of binary neutron star (BNS) systems are predicted to be progenitors of short gamma-ray bursts (GRBs); the definitive probe of this association came with the recent detection of gravitational waves (GWs) from a BNS merger by Advanced LIGO and Advanced Virgo (GW170817), in coincidence with the short GRB 170817A observed by Fermi-GBM and INTEGRAL. Short GRBs are also expected to emit very-high energy (VHE, > 100 GeV) photons and VHE electromagnetic (EM) upper limits have been set with observations performed by ground-based gamma-ray detectors and during the intense EM follow-up campaign associated with GW170817/GRB 170817A. In the next years, the searches for VHE EM counterparts will become more effective thanks to the Cherenkov Telescope Array (CTA): this instrument will be fundamental for the EM follow-up of transient GW events at VHE, owing to its unprecedented sensitivity, rapid response (few tens of seconds) and capability to monitor large sky areas via survey-mode operation. We present a comprehensive study on the prospects for joint GW and VHE EM observations of merging BNSs with Advanced LIGO, Advanced Virgo and CTA, based on detailed simulations of the multi-messenger emission and detection. We propose a new observational strategy optimized on the prior assumptions about the EM emission. The method can be further generalized to include other electromagnetic emission models. According to this study CTA will cover most of the region of the GW skymap for the intermediate and most energetic on-axis GRBs associated to the GW event. We estimate the expected joint GW and VHE EM detection rates and we found this rate goes from 0.08 up to 0.5 events per year for the most energetic EM sources.

astro-ph.HE↗

arXiv2016

Prospects for joint observations of gravitational waves and gamma rays from merging neutron star binaries

The detection of the events GW150914 and GW151226, both consistent with the merger of a binary black hole system (BBH), opened the era of gravitational wave (GW) astronomy. Besides BBHs, the most promising GW sources are the coalescences of binary systems formed by two neutron stars or a neutron star and a black hole. These mergers are thought to be connected with short Gamma Ray Bursts (GRBs), therefore combined observations of GW and electromagnetic (EM) signals could definitively probe this association. We present a detailed study on the expectations for joint GW and high-energy EM observations of coalescences of binary systems of neutron stars with Advanced Virgo and LIGO and with the \emph{Fermi} gamma-ray telescope. To this scope, we designed a dedicated Montecarlo simulation pipeline for the multimessenger emission and detection by GW and gamma-ray instruments, considering the evolution of the GW detector sensitivities. We show that the expected rate of joint detection is low during the Advanced Virgo and Advanced LIGO 2016-2017 run; however, as the interferometers approach their final design sensitivities, the rate will increase by $\sim$ a factor of ten. Future joint observations will help to constrain the association between short GRBs and binary systems and to solve the puzzle of the progenitors of GWs. Comparison of the joint detection rate with the ones predicted in this paper will help to constrain the geometry of the GRB jet.

astro-ph.HE↗

arXiv2015

(Almost-)blind locking algorithm for high finesse suspended optical cavities

Suspended resonant optical cavities are basic building blocks for several experimental devices. An important issue is the control strategy required to bring them in the resonant or slightly detuned configuration needed for their operation, the so-called \textit{ locking} procedure. This can be obtained with a feedback strategy, but the error signal needed is tipically available only when the cavity is near the resonance with a precision of the order $ΔL\simeqλ_{\ell}{\cal F}^{-1}$, where ${\cal F}$ is the cavity finesse and $λ_{\ell}$ is the laser's wavelength. When the mirrors are freely swinging the locking can be attempted only in the short time windows when this condition is verifyed. Tipically this means that the procedure must be repeated several times, and that large forces must be applied. In this paper we describe a different strategy, which tries to take advantage by the fact that the dynamics of the mirrors is known at least in an approximate way. We argue that the locking procedure considered can be more efficient compared with the naive one, with a reduced needed maximal feedback. Finally we discuss possible generalizations and we point to future investigations.

physics.ins-det↗

arXiv2007

Prospects for Stochastic Background Searches Using Virgo and LSC Interferometers

We consider the question of cross-correlation measurements using Virgo and the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search for a stochastic gravitational-wave background. We find that inclusion of Virgo into the network will substantially improve the sensitivity to correlations above 200 Hz if all detectors are operating at their design sensitivity. This is illustrated using a simulated isotropic stochastic background signal, generated with an astrophysically-motivated spectrum, injected into 24 hours of simulated noise for the LIGO and Virgo interferometers.

gr-qc↗

arXiv1994

QCD corrections to electroweak processes in an unconventional scheme: application to the b -> s gamma decay

In this work we give a detailed description of a method for the calculation of QCD corrections to electroweak processes in dimensional regularization that does not require any definition of the gamma_5 matrix in d dimensions. This method appears particularly convenient in order to limit the algebraic complexity of higher order calculations. As an example, we compute the leading logarithmic corrections to the b -> s gamma decay.

hep-ph↗