arXiv subjects

Jamal Mimouni

Publications and source records attributed to Jamal Mimouni.

12 recordsLinked to original sources

arXiv2026

Constraining Cosmological Parameters From Statistical Superluminal Effects Without a Distance Ladder

We employ a statistical approach to study apparent superluminal motion of luminous sources in an expanding flat Friedmann--Lemaître--Robertson--Walker universe, explicitly incorporating cosmological effects through the comoving distance at the emission time. Probability Density Functions (PDFs) of the apparent angular velocity are derived under minimal assumptions regarding source orientations and intrinsic peculiar velocity distributions. We show that the apparent angular velocity distributions and their associated statistical observables are sensitive to cosmological parameters $Ω_{Λ,0}$ and the Hubble parameter $H_0$. Using suitably defined observables, we construct correlated constraints in the $(Ω_{Λ,0}, H_0)$ parameter space and demonstrate that combining measurements at different redshifts effectively breaks the resulting degeneracy. Apparent superluminal motion thus provides a complementary kinematic consistency test for cosmological models.

gr-qc↗

arXiv2024

Non-Radial Free Geodesics. II. In Spatially Curved FLRW Spacetime

This paper presents an in-depth exploration of timelike free geodesics in spatially curved Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime. A unified approach for these geodesics encompassing both radial and non-radial trajectories across Euclidean, spherical, and hyperbolic geometries is employed. Using the symmetry properties of the system, two constants of motion related to this dynamical system are derived. This treatment facilitates the explicit computation of radial and angular peculiar velocities, along with the evolution of the comoving radial distance and angle over time. The study introduces three distinct methods for characterizing geodesic solutions, further delving into the flatness limit, the null geodesic limit, the radial geodesic limit, the comoving geodesic limit, and the circular orbits. Additionally, we analyze Killing vectors, reflecting the symmetries inherent in the dynamical system. This study provides a more profound understanding of the behavior of free particles as observed from a comoving reference frame.

gr-qc↗

arXiv2024

Non-Radial Free Geodesics. I. In Spatially Flat FLRW Spacetime

This paper provides an analytical examination of non-radial geodesics within the context of the spatially flat Friedmann Lemaître Robertson Walker (FLRW) spacetime. Using the symmetry properties of the system, two constants of motion related to this dynamical system are derived. This treatment enables us to explicitly compute the radial and angular peculiar velocities, as well as the evolution of the comoving radial distance and angle over time. The study introduces three distinct methods to characterize geodesic solutions, and additionally examines the radial geodesic limit, the null geodesic limit, and the comoving geodesic limit. Additionally, the paper investigates both non-radial and radial free geodesics within the Lambda Cold Dark Matter (ΛCDM) model, presenting detailed results and discussions. Lastly, we explore the total angle swept by a free particle from the initial singularity to infinity as measured by a comoving observer, offering insights into the dynamics of free particles in FLRW spacetime.

gr-qc↗

arXiv2024

Studying the Behavior of Radial Free Geodesics in ΛCDM Model

This paper presents an analytical study of the behavior of radial free-geodesics in the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime within the Lambda Cold Dark Matter (ΛCDM) model. Using the radial free motion solutions, we provide two methods for characterizing the geodesics and defines a general formula that encapsulates all possible solutions, determined by two initial conditions. We show that the past light cone, event horizon, and particle horizon, can be considered as special cases of this overarching formula. Furthermore, the paper explores the free geodesics within the currently accepted cosmological model based on the recent Planck results, thoroughly examining the various possible geodesic scenarios.

gr-qc↗

arXiv2022

Launching the VASCO citizen science project

The Vanishing & Appearing Sources during a Century of Observations (VASCO) project investigates astronomical surveys spanning a time interval of 70 years, searching for unusual and exotic transients. We present herein the VASCO Citizen Science Project, which can identify unusual candidates driven by three different approaches: hypothesis, exploratory, and machine learning, which is particularly useful for SETI searches. To address the big data challenge, VASCO combines three methods: the Virtual Observatory, user-aided machine learning, and visual inspection through citizen science. Here we demonstrate the citizen science project and its improved candidate selection process, and we give a progress report. We also present the VASCO citizen science network led by amateur astronomy associations mainly located in Algeria, Cameroon, and Nigeria. At the moment of writing, the citizen science project has carefully examined 15,593 candidate image pairs in the data (ca. 10% of the candidates), and has so far identified 798 objects classified as "vanished". The most interesting candidates will be followed up with optical and infrared imaging, together with the observations by the most potent radio telescopes.

astro-ph.IM↗

arXiv2022

On making physics relevant to society in general and to scientists in particular: Closing the epistemic gap

Physics has a bad press: it is seen by a majority of people as a boring discipline ever since their High School days. There is no glamour to it, just toil and pain, and for many who engaged in it, the end sight is often unemployment. Could it be that physicists don't know how to communicate what their discipline entails to? I will be tackling the problematic of making physics relevant to society and to the scientists in general. I will also be dealing with the methodological and educational aspects of teaching and practicing physics, and the need to close the epistemic gap between physics teaching and the physicist's understanding ... By the way, do physicists understand physics?

physics.ed-ph↗

arXiv2022

ASFAP Working Group Summary of Societal Engagements

The second African Conference of Fundamental and Applied Physics (ACP2021) took place in the week of March 7-11, 2022. During this conference, all the African Strategy for Fundamental and Applied Physics (ASFAP) working groups had been reserved specials sessions to discuss their scope, activities (past & current) and topics of common interests. The aim of this report is to summarize the discussion of the ASFAP working groups in societal engagements, namely Physics Education, Community Engagement, Young Physicists and Women in Physics. The recommendations for future activities in societal engagements are summarised in the report as well.

physics.soc-ph↗

arXiv2022

Is there a background population of high-albedo objects in geosynchronous orbits around Earth?

Old, digitized astronomical images taken before the human spacefaring age offer a unique view of the sky devoid of known artificial satellites. In this paper, we have carried out the first optical searches ever for non-terrestrial artifacts near the Earth following the method proposed in Villarroel et al. (2022). We use images contained in the First Palomar Sky Survey to search for simultaneous (during a plate exposure time) transients that in addition to being point-like, are aligned. We provide a shortlist of the most promising candidates of aligned transients, that must be examined with the help of a microscope to separate celestial sources from plate defects with coincidentally star-like brightness profiles. We further explore one possible, but not unique, interpretation in terms of fast reflections off high-albedo objects in geosynchronous orbits around Earth. If a future study rules out each multiple transient candidate, the estimated surface density becomes an upper limit of $<10^{-9}$ objects km$^{-2}$ non-terrestrial artifacts in geosynchronous orbits around Earth. Finally, we conclude that observations and analysis of multiple, simultaneously appearing and vanishing light sources on the sky merit serious further attention, regardless of their origin.

astro-ph.EP↗

arXiv2021

A 331 Model for Lepton Flavor Universality Violation in $B$ Decays

Lepton Flavor Universality Violation (LFUV) in $B$ decays in both neutral $b\rightarrow s l^+ l^-$ and charged $b\rightarrow cl\barν_{l}$ processes observed in the ratios $R_{K^{(*)}}$ and $R_{D^{(*)}}$ is investigated in the framework of a model based on the extended symmetry gauge $SU(3)_{C}\otimes SU(3)_{L}\otimes U(1)_{X}$ whose leptonic sector consists of five triplets. It is shown that in order to explain the experimentally observed deviations from the Standard Model in these flavor changing transitions, a non-minimal version of the model has to be considered. We investigate the ability of this model in accommodating the model-independent scenarios currently favored by global fits.

hep-ph↗

arXiv2020

Lepton Flavor Universality Violation in a 331 Model in $b\rightarrow s l^+ l^-$ Processes

Lepton Flavor Universality Violation (LFUV) in $b\rightarrow s l^+ l^-$ processes is investigated in the context of a 331 model. It is shown that in order to explain the experimentally observed deviations from the Standard Model in these FCNC transitions, a non-minimal version of the model has to be considered. We investigate the ability of this model in accomodating the model-independant scenarios currently favored by global fits.

hep-ph↗

arXiv2018

Development in Astronomy and Space Science in Africa

The development of astronomy and space science in Africa has grown significantly over the past few years. These advancements make the United Nations Sustainable Development Goals more achievable, and open up the possibility of new beneficial collaborations.

astro-ph.IM↗

arXiv2003

Supernova Neutrino Spectrum with Matter and Spin Flavor Precession Effects

We consider Majorana neutrino conversions inside supernovae by taking into account both flavor mixing and the neutrino magnetic moment. We study the adiabaticity of various possible transitions between the neutrino states for both normal and inverted hierarchy within the various solar neutrino problem solutions. From the final mass spectrum within diffrent scenarios, we infer the consequences of the various conversion effects on the neutronization peak, the nature of final spectra, and the possible Earth matter effect on the final fluxes. This enable us to check the sensibility of the SN neutrino flux on magnetic moment interaction, and narrow down possible scenarios which depend on: the mass spectrum normal or inverted, the solution of the solar neutrino problem; and the value of MuxB.

astro-ph↗