Enis Belgacem
A5076550948- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Black Holes and Theoretical Physics
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Superconducting and THz Device Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Noncommutative and Quantum Gravity Theories
- Stochastic processes and financial applications
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Geophysics and Sensor Technology
- Seismic Waves and Analysis
- Advanced Fiber Optic Sensors
- Complex Systems and Time Series Analysis
- Adaptive optics and wavefront sensing
- Relativity and Gravitational Theory
- Planetary Science and Exploration
University of Geneva
2016-2023
Utrecht University
2021-2023
Instituto de Física Teórica
2021
The Einstein Telescope (ET), a proposed European ground-based gravitational-wave detector of third-generation, is an evolution second-generation detectors such as Advanced LIGO, Virgo, and KAGRA which could be operating in the mid 2030s. ET will explore universe with gravitational waves up to cosmological distances. We discuss its main scientific objectives potential for discoveries astrophysics, cosmology fundamental physics.
Abstract The Einstein Telescope (ET), the European project for a third-generation gravitational-wave detector, has reference configuration based on triangular shape consisting of three nested detectors with 10 km arms, where each detector 'xylophone' made an interferometer tuned toward high frequencies, and low frequencies working at cryogenic temperature. Here, we examine scientific perspectives under possible variations this design. We perform detailed evaluation science case single...
Modifications of General Relativity leave their imprint both on the cosmic expansion history through a non-trivial dark energy equation state, and evolution cosmological perturbations in scalar tensor sectors. In particular, modification sector gives rise to notion gravitational-wave (GW) luminosity distance, different from standard electromagnetic that can be studied with sirens at GW detectors such as LISA or third-generation ground based experiments. We discuss predictions for modified...
Even if the fundamental action of gravity is local, corresponding quantum effective action, that includes effect fluctuations, a nonlocal object. These nonlocalities are well understood in ultraviolet regime but much less infrared, where they could principle give rise to important cosmological effects. Here we systematize and extend previous work our group, which it assumed mass scale Λ dynamically generated giving terms gravity. We detailed discussion conceptual aspects related (including...
The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about fundamental theory of nature at play in extreme gravity regime, where gravitational interaction is both strong and dynamical. In this white paper, Fundamental Physics Working Group LISA Consortium summarizes current topics physics observations GWs can be expected provide key input. We briefest reviews then delineate avenues for future research directions discuss connections between working group, other...
In modified gravity the propagation of gravitational waves (GWs) is in general different from that relativity. As a result, luminosity distance for GWs can differ electromagnetic signals, and affected both by dark energy equation state $w_{\rm DE}(z)$ function $\delta(z)$ describing propagation. We show effect dominates over state, making it easier to distinguish model $\Lambda$CDM. illustrate this using nonlocal modification gravity, has been shown fit remarkably well CMB, SNe, BAO...
Studies of dark energy at advanced gravitational-wave (GW) interferometers normally focus on the equation state ${w}_{\mathrm{DE}}(z)$. However, modified gravity theories that predict a nontrivial generically also deviations from general relativity in propagation GWs across cosmological distances, even where speed is equal to $c$. We find that, generic models, effect GW dominates over ${w}_{\mathrm{DE}}(z)$, making crucial observable for studies with standard sirens. present convenient...
Abstract The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response Moon gravitational waves (GWs). Given size and expected noise produced by lunar seismic background, LGWA would be able observe GWs from about 1 mHz Hz. This make missing link between space-borne detectors like LISA with peak sensitivities around few millihertz future terrestrial Einstein Telescope or Cosmic Explorer. In this article, we provide first...
Gravitational-wave (GW) detectors can contribute to the measurement of cosmological parameters and testing dark-energy sector alternatives $\Lambda$CDM, by using standard sirens. In this paper we focus on binary neutron stars with a counterpart detected through gamma-ray burst (GRB), both at second-generation network made advanced LIGO+advanced Virgo+LIGO India+Kagra, third-generation (3G) detectors, discussing in particular cases single Einstein Telescope (ET), ET plus two Cosmic Explorer...
The next generation of ground-based gravitational-wave detectors will observe coalescences black holes and neutron stars throughout the cosmos, thousands them with exceptional fidelity. Science Book is result a 3-year effort to study science capabilities networks detectors. Such would make it possible address unsolved problems in numerous areas physics astronomy, from Cosmology Beyond Standard Model particle physics, how they could provide insights into workings strongly gravitating systems,...
The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate universe, and understand stochastic gravitational-wave backgrounds their implications for early universe particle physics, from MeV Planck scale. However, range potential applications gravitational wave observations extends well beyond these objectives. This publication presents a summary state art in LISA cosmology, theory methods, identifies new opportunities use...
Recent work has shown that modified gravitational wave (GW) propagation can be a powerful probe of dark energy and gravity, specific to GW observations. We use the technique Gaussian processes, which allows reconstruction function from data without assuming any parametrization, measurements luminosity distance simulated joint GW-gamma-ray-burst detections, combined with electromagnetic by survey (DES). For events, we consider both second-generation LIGO/Virgo/Kagra (HVLKI) network,...
We describe the signatures of a circularly polarized gravitational-wave background on timing residuals obtained with pulsar-timing arrays. Most generally, circular polarization will depend direction, and we this angular dependence in terms spherical harmonics. While amplitude monopole (the overall chirality background) cannot be detected, measures anisotropy are theoretically conceivable. provide expressions for minimum-variance estimators circular-polarization anisotropy. evaluate smallest...
We provide a detailed derivation of the spectral density stochastic background generated by superposition coalescing compact binaries. show how expression often used in literature emerges from an average over extrinsic parameters binaries (times arrival, polarization angles, arrival directions and orbit inclinations) Stokes related to circular linear are set zero such averaging procedure. then consider effect shot noise, i.e. fact that for finite number sources these averages only...
The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response Moon gravitational waves (GWs). Given size and expected noise produced by lunar seismic background, LGWA would be able observe GWs from about 1 mHz Hz. This make missing link between space-borne detectors like LISA with peak sensitivities around few millihertz future terrestrial Einstein Telescope or Cosmic Explorer. In this article, we provide first comprehensive...
We study the impact of limit on $|\dot{G}|/G$ from Lunar Laser Ranging "nonlocal gravity", i.e. models quantum effective action gravity that include nonlocal terms relevant in infrared, such as "RR" and "RT" proposed by our group, Deser-Woodard (DW) model. elaborate analysis Barreira et al. [1] we confirm their findings (under plausible assumptions absence strong backreaction non-linear structures), RR model is ruled out. also show mechanism "perfect screening for free" suggested DW actually...
We provide a systematic and updated discussion of research line carried out by our group over the last few years, in which gravity is modified at cosmological distances introduction nonlocal terms, assumed to emerge an effective level from infrared behavior quantum theory. The requirement producing viable cosmology turns be very stringent basically selects unique model, term describes mass for conformal mode. discuss how such specific structure could fundamental local theory gravity, we...
Local measurements of the Hubble parameter obtained from distance ladder at low redshift are in tension with global values inferred cosmological standard rulers. A key role is played by assumptions on history, particular origin dark energy. Here we consider a scenario where energy originates amplification quantum fluctuations light field inflation. We show that spatial correlations inherited inflationary can reduce down to one deviation, thus relieving problem respect model. Upcoming...
Abstract The interaction of a gravitational wave (GW) with an elastic body is usually described in terms GW “force” driving the oscillations body's normal modes. However, this description only possible for frequencies which response dominated by few At higher modes blend into quasi-continuum and field-theoretical description, as pioneered Dyson already 1969, becomes necessary. since metric perturbation h μν intrinsically relativistic object, consistent coupling to GWs can be obtained within...
Abstract Recently, detailed studies have been made to compare the performance of European next generation GW observatory Einstein Telescope (ET) in a single-site triangular configuration with featuring two L-shaped detectors different sites, still taken all other ET characteristics except for geometry, particular, underground and composed low-frequency interferometer working at cryogenic temperatures high-frequency room temperature. Here we study further possibility network, by single...
We discuss a modified gravity model which fits cosmological observations at level statistically indistinguishable from $\Lambda$CDM and the same time predicts very large deviations General Relativity (GR) in propagation of gravitational waves (GWs) across distances. The is variant RT nonlocal proposed developed by our group, with initial conditions set during inflation, GW luminosity distance that, redshifts accessible to LISA or third-generation detector such as Einstein Telescope (ET), can...
Abstract The origin of dark energy driving the accelerated expansion universe is still mysterious. We explore possibility that fluctuates, resulting in spatial correlations. Due to these fluctuations, Hubble rate itself becomes a fluctuating quantity. discuss effect this has on measurements type Ia supernovae, which are used constrain luminosity distance. show distance affected by correlations several ways. First, dressed thereby differing from standard ΛCDM. Second, angular become visible...