arXiv subjects

B. Lamine

Publications and source records attributed to B. Lamine.

9 recordsLinked to original sources

arXiv2024

Euclid preparation. Improving cosmological constraints using a new multi-tracer method with the spectroscopic and photometric samples

Future data provided by the Euclid mission will allow us to better understand the cosmic history of the Universe. A metric of its performance is the figure-of-merit (FoM) of dark energy, usually estimated with Fisher forecasts. The expected FoM has previously been estimated taking into account the two main probes of Euclid, namely the three-dimensional clustering of the spectroscopic galaxy sample, and the so-called 3x2pt signal from the photometric sample (i.e., the weak lensing signal, the galaxy clustering, and their cross-correlation). So far, these two probes have been treated as independent. In this paper, we introduce a new observable given by the ratio of the (angular) two-point correlation function of galaxies from the two surveys. For identical (normalised) selection functions, this observable is unaffected by sampling noise, and its variance is solely controlled by Poisson noise. We present forecasts for Euclid where this multi-tracer method is applied and is particularly relevant because the two surveys will cover the same area of the sky. This method allows for the exploitation of the combination of the spectroscopic and photometric samples. When the correlation between this new observable and the other probes is not taken into account, a significant gain is obtained in the FoM, as well as in the constraints on other cosmological parameters. The benefit is more pronounced for a commonly investigated modified gravity model, namely the $\gamma$ parametrisation of the growth factor. However, the correlation between the different probes is found to be significant and hence the actual gain is uncertain. We present various strategies for circumventing this issue and still extract useful information from the new observable.

astro-ph.CO↗

arXiv2021

Sensing Quantum Nature of Primordial Gravitational Waves Using Electromagnetic Probes

Based on optical medium analogy, we establish a formalism to describe the interaction between an electromagnetic (EM) system with gravitational waves (GWs) background. After a full discussion on the classical treatment of the EM-GW interaction and finding the EM field mode-functions in the presence of the magneto-dielectric media caused by GWs, the governing quantum interaction Hamiltonian is obtained. Investigation of the optical quadrature variance as well as the visibility of a laser field interacting with the multi-mode squeezed primordial gravitational waves imply that the inflationary primordial gravitational waves (PGWs) act as a decoherence mechanism that destroy EM coherency after a characteristic time scale, $\tau_{c}$, which depends on the inflationary parameters $(\beta,\beta_s,r)$, or equivalently, the fractional energy density of PGWs, $\Omega_{gw,0}$. The decoherency mechanism overcomes the coherent effects, such as revivals of optical squeezing, thus leaving their confirmation out of reach. Influenced by the continuum of the squeezed PGWs, the laser field suffers a line-width broadening by $\gamma= \tau_{\text{c}}^{-1}$. The most peculiar property of the EM spectrum is the apparition of side bands at $\omega\sim \omega_0\pm 1.39 \tau_c^{-1}$Hz, stemming from the squeezed nature of PGWs. The laser phase noise induced by the squeezed PGWs grows with time squarely, $\Delta\phi=(t/\tau_c)^2$, that can most possibly be sensed within a finite flight time.

gr-qc↗

arXiv2014

Tests of Gravitation at Solar System scales beyond the PPN formalism

In this communication, the current tests of gravitation available at Solar System scales are recalled. These tests rely mainly on two frameworks: the PPN framework and the search for a fifth force. Some motivations are given to look for deviations from General Relativity in other frameworks than the two extensively considered. A recent analysis of Cassini data in a MOND framework is presented. Furthermore, possibilities to constrain Standard Model Extension parameters using Solar System data are developed.

gr-qc↗

arXiv2013

How to test SME with space missions ?

In this communication, we focus on possibilities to constrain SME coefficients using Cassini and Messenger data. We present simulations of radioscience observables within the framework of the SME, identify the linear combinations of SME coefficients the observations depend on and determine the sensitivity of these measurements to the SME coefficients. We show that these datasets are very powerful for constraining SME coefficients.

gr-qc↗

arXiv2013

Simulations of Solar System observations in alternative theories of gravity

In this communication, we focus on the possibility to test General Relativity (GR) with radioscience experiments. We present simulations of observables performed in alternative theories of gravity using a software that simulates Range/Doppler signals directly from the space time metric. This software allows one to get the order of magnitude and the signature of the modifications induced by an alternative theory of gravity on radioscience signals. As examples, we present some simulations for the Cassini mission in Post-Einsteinian gravity (PEG) and with Standard Model Extension (SME).

gr-qc↗

arXiv2012

Radioscience simulations in General Relativity and in alternative theories of gravity

In this paper, we focus on the possibility to test General Relativity in the Solar System with radioscience measurements. To this aim, we present a new software that simulates Range and Doppler signals directly from the space-time metric. This flexible approach allows one to perform simulations in General Relativity and in alternative metric theories of gravity. In a second step, a least-squares fit of the different initial conditions involved in the situation is performed in order to compare anomalous signals produced by a given alternative theory with the ones obtained in General Relativity. This software provides orders of magnitude and signatures stemming from hypothetical alternative theories of gravity on radioscience signals. As an application, we present some simulations done for the Cassini mission in Post-Einsteinian Gravity and in the context of MOND External Field Effect. We deduce constraints on the Post-Einsteinian parameters but find that the considered arc of the Cassini mission is not useful to constrain the MOND External Field Effect.

gr-qc↗

arXiv2011

Testing Gravitation in the Solar System with Radio Science experiments

The laws of gravitation have been tested for a long time with steadily improving precision, leading at some moment of time to paradigmatic evolutions. Pursuing this continual effort is of great importance for science. In this communication, we focus on Solar System tests of gravity and more precisely on possible tests that can be performed with radio science observations (Range and Doppler). After briefly reviewing the current tests of gravitation at Solar System scales, we give motivations to continue such experiments. In order to obtain signature and estimate the amplitude of anomalous signals that could show up in radio science observables because of modified gravitational laws, we developed a new software that simulates Range/Doppler signals. We present this new tool that simulates radio science observables directly from the space-time metric. We apply this tool to the Cassini mission during its cruise from Jupiter to Saturn and derive constraints on the parameters entering alternative theories of gravity beyond the standard Parametrized Post Newtonian theory.

gr-qc↗

arXiv2011

Testing gravity law in the solar system

The predictions of General relativity (GR) are in good agreement with observations in the solar system. Nevertheless, unexpected anomalies appeared during the last decades, along with the increasing precision of measurements. Those anomalies are present in spacecraft tracking data (Pioneer and flyby anomalies) as well as ephemerides. In addition, the whole theory is challenged at galactic and cosmic scales with the dark matter and dark energy issues. Finally, the unification in the framework of quantum field theories remains an open question, whose solution will certainly lead to modifications of the theory, even at large distances. As long as those "dark sides" of the universe have no universally accepted interpretation nor are they observed through other means than the gravitational anomalies they have been designed to cure, these anomalies may as well be interpreted as deviations from GR. In this context, there is a strong motivation for improved and more systematic tests of GR inside the solar system, with the aim to bridge the gap between gravity experiments in the solar system and observations at much larger scales. We review a family of metric extensions of GR which preserve the equivalence principle but modify the coupling between energy and curvature and provide a phenomenological framework which generalizes the PPN framework and "fifth force" extensions of GR. We briefly discuss some possible observational consequences in connection with highly accurate ephemerides.

gr-qc↗

arXiv2011

Large scale EPR correlations and cosmic gravitational waves

We study how quantum correlations survive at large scales in spite of their exposition to stochastic backgrounds of gravitational waves. We consider Einstein-Podolski-Rosen (EPR) correlations built up on the polarizations of photon pairs and evaluate how they are affected by the cosmic gravitational wave background (CGWB). We evaluate the quantum decoherence of the EPR correlations in terms of a reduction of the violation of the Bell inequality as written by Clauser, Horne, Shimony and Holt (CHSH). We show that this decoherence remains small and that EPR correlations can in principle survive up to the largest cosmic scales.

gr-qc↗