Alain Blanchard
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View article: Cosmological implications of the <i>Gaia</i> Milky Way declining rotation curve
Cosmological implications of the <i>Gaia</i> Milky Way declining rotation curve Open
Although the existence of dark matter has been widely acknowledged in the cosmology community, its nature remains unknown despite decades of research. This calls into questions its very existence. This never-ending search for dark matter h…
View article: Muon Anomalous Magnetic Moment and Right-Handed Sterile Neutrino
Muon Anomalous Magnetic Moment and Right-Handed Sterile Neutrino Open
The muon’s magnetic moment is a fundamental quantity in particle physics and the observed deviation of its value from the prediction of quantum electrodynamics motivated investigations beyond the Standard Model (SM). In this study, we util…
View article: Euclid: Forecasts on $Λ$CDM consistency tests with growth rate data
Euclid: Forecasts on $Λ$CDM consistency tests with growth rate data Open
The large-scale structure (LSS) of the Universe is an important probe for deviations from the canonical cosmological constant $Λ$ and cold dark matter ($Λ$CDM) model. A statistically significant detection of any deviations would signify th…
View article: The Fallacies of ΛCDM Falsifications
The Fallacies of ΛCDM Falsifications Open
In recent years, numerous arguments have emerged suggesting that the Lambda Cold Dark Matter (ΛCDM) model may be inconsistent with observational data, requiring more or less radical revisions. Notable examples include the “Hubble tension”—…
View article: Phase Diffusion of Light Immersed In Quantum Tides: Open Quantum System Approach
Phase Diffusion of Light Immersed In Quantum Tides: Open Quantum System Approach Open
The interaction between quantum gravitational waves (GWs) and electromagnetic (EM) fields is investigated within the open quantum system formalism, where GWs are considered as a heat bath reservoir occupying a generic state $\hatρ_{\text{g…
View article: Probing the Distance Duality Relation with Machine Learning and Recent Data
Probing the Distance Duality Relation with Machine Learning and Recent Data Open
The distance duality relation (DDR) relates two independent ways of measuring cosmological distances, namely the angular diameter distance and the luminosity distance. These can be measured with baryon acoustic oscillations (BAO) and Type …
View article: Generation of the CMB cosmic Birefringence through Axion-like particles, Sterile and Active neutrinos
Generation of the CMB cosmic Birefringence through Axion-like particles, Sterile and Active neutrinos Open
The cosmic birefringence (CB) angle refers to the rotation of the linear polarization plane of Cosmic Microwave Background (CMB) radiations when parity-violating theories are considered. We analyzed the Quantum Boltzmann equation for an en…
View article: Cosmological implications of the Gaia Milky Way declining rotation curve
Cosmological implications of the Gaia Milky Way declining rotation curve Open
Although the existence of dark matter has been widely acknowledged in the cosmology community, it is as yet unknown in nature, despite decades of research, which questions its very existence. This never-ending search for dark matter leads …
View article: <i>Euclid</i> preparation
<i>Euclid</i> preparation Open
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 expecte…
View article: Cosmological measurement of the gravitational constant $G$ using the CMB, the BAO and the BBN
Cosmological measurement of the gravitational constant $G$ using the CMB, the BAO and the BBN Open
Recent cosmological observations have provided numerous new observations with increasing precision that have led to the era of precision cosmology. The exquisite quality of these observations opens new possibilities towards measuring funda…
View article: ΛCDM is alive and well
ΛCDM is alive and well Open
Despite its successes, the CDM model faces several tensions with recent cosmological data and their increased accuracy. The mismatch between the values of the Hubble constant obtained from {some} direct distance ladder measurements a…
View article: Revisiting van Citter-Zernike correlations in the presence of primordial gravitational waves
Revisiting van Citter-Zernike correlations in the presence of primordial gravitational waves Open
In this paper, we develop a quantum field theory framework to describe the interaction between a gravitational wave (GW) background and an electromagnetic (EM) field emitted from a distant celestial source, such as a star. We demonstrate t…
View article: <i>Euclid</i>: Validation of the MontePython forecasting tools
<i>Euclid</i>: Validation of the MontePython forecasting tools Open
Context . The Euclid mission of the European Space Agency will perform a survey of weak lensing cosmic shear and galaxy clustering in order to constrain cosmological models and fundamental physics. Aims . We expand and adjust the mock Eucl…
View article: Euclid: Validation of the MontePython forecasting tools
Euclid: Validation of the MontePython forecasting tools Open
The Euclid mission of the European Space Agency will perform a survey of weak lensing cosmic shear and galaxy clustering in order to constrain cosmological models and fundamental physics. We expand and adjust the mock Euclid likelihoods of…
View article: The Role of Cross-Correlations in the Multi-Tracer Area
The Role of Cross-Correlations in the Multi-Tracer Area Open
Mapping the same volume of space with different tracers allows us to obtain information through estimated quantities exploiting the multi-tracer technique. Indeed, the cross-correlation of different probes provides information that cannot …
View article: Cluster counts
Cluster counts Open
Despite the success of the Lambda cold dark matter (ΛCDM) cosmological model, current estimations of the amplitude of matter fluctuations ( σ 8 ) show an appreciable difference between its value inferred from the cosmic microwave backgroun…
View article: $Λ$CDM is alive and well
$Λ$CDM is alive and well Open
The $Λ$CDM model faces several tensions with recent cosmological data and their increased accuracy. The mismatch between the values of the Hubble constant $H_0$ obtained from direct distance ladder measurements and from the cosmic microwav…
View article: Can Dark Energy Emerge from a Varying G and Spacetime Geometry?
Can Dark Energy Emerge from a Varying G and Spacetime Geometry? Open
The accelerated expansion of the universe implies the existence of an energy contribution known as dark energy. Associated with the cosmological constant in the standard model of cosmology, the nature of this dark energy is still unknown. …
View article: Cluster counts III. $Λ$CDM extensions and the cluster tension
Cluster counts III. $Λ$CDM extensions and the cluster tension Open
In this work, we examine whether further extensions to the $Λ$CDM model could alleviate the $σ_8$ tension. For that, we derive constraints on the parameters subject of the discrepancy, using CMB $C_{\ell}$ combined with cluster counts SZ s…
View article: Testing fundamental cosmological assumptions with Euclid
Testing fundamental cosmological assumptions with Euclid Open
The forthcoming Euclid survey will be able to map the large scale structure with unprecedented precision, with the aim of tightly constraining the standard cosmological model and its most common extensions. The great sensitivity of Euclid …
View article: Sensing Quantum Nature of Primordial Gravitational Waves Using Electromagnetic Probes
Sensing Quantum Nature of Primordial Gravitational Waves Using Electromagnetic Probes Open
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 interac…
View article: Closing up the cluster tension?
Closing up the cluster tension? Open
The excellent measurements of the cosmic microwave background (CMB) fluctuations by Planck allow us to tightly constrain the amplitude of matter fluctuations at redshift ∼1100 in the Λ-cold dark matter (ΛCDM) model. This amplitude can be e…
View article: <i>Euclid</i> preparation
<i>Euclid</i> preparation Open
The combination and cross-correlation of the upcoming Euclid data with cosmic microwave background (CMB) measurements is a source of great expectation since it will provide the largest lever arm of epochs, ranging from recombination to str…
View article: <i>Euclid</i>: Constraining dark energy coupled to electromagnetism using astrophysical and laboratory data
<i>Euclid</i>: Constraining dark energy coupled to electromagnetism using astrophysical and laboratory data Open
In physically realistic, scalar-field-based dynamical dark energy models (including, e.g., quintessence), one naturally expects the scalar field to couple to the rest of the model’s degrees of freedom. In particular, a coupling to the elec…
View article: Validating the Fisher approach for stage IV spectroscopic surveys
Validating the Fisher approach for stage IV spectroscopic surveys Open
In recent years, forecasting activities have become an important tool in designing and optimising large-scale structure surveys. To predict the performance of such surveys, the Fisher matrix formalism is frequently used as a fast and easy …
View article: Closing up the cluster tension?
Closing up the cluster tension? Open
The excellent measurements of the cosmic microwave background (CMB)\nfluctuations by Planck allow us to tightly constrain the amplitude of matter\nfluctuations at redshift $\\sim 1100$ in the $\\Lambda$-cold dark matter\n($\\Lambda$CDM) mo…