Subsonic accretion and dynamical friction for a black hole moving through a self-interacting scalar dark matter cloud

We investigate the flow around a black hole moving through a cloud of self-interacting scalar dark matter. We focus on the large scalar mass limit, with quartic self-interactions, and on the subsonic regime. We show how the scalar field behaves as a perfect gas of adiabatic index $\gamma_{\rm ad}=2$ at large radii while the accretion rate is governed by the relativistic regime close to the Schwarzschild radius. We obtain analytical results thanks to large-radius expansions, which are also related to the small-scale relativistic accretion rate. We find that the accretion rate is greater than for collisionless particles, by a factor $c/c_s \gg 1$, but smaller than for a perfect gas, by a factor $c_s/c \ll 1$, where $c_s$ is the speed of sound. The dynamical friction is smaller than for a perfect gas, by the same factor $c_s/c \ll 1$, and also smaller than Chandrasekhar's result for collisionless particles, by a factor $c_s/(cC)$, where $C$ is the Coulomb logarithm. It is also smaller than for fuzzy dark matter, by a factor $v_0/c \ll 1$

Supersonic friction of a black hole traversing a self-interacting scalar dark matter cloud

Black Holes (BH) traversing a dark matter cloud made out of a self-interacting scalar soliton are slowed down by two complementary effects. At low subsonic speeds, the BH accretes dark matter and this is the only source of dragging along its motion, if we neglect the backreaction of the cloud self-gravity. The situation changes at larger supersonic speeds where a bow shock in front of the BH is created. This leads to the emergence of an additional friction term, associated with the gravitational and scalar pressure interactions and with the wake behind the moving BH. This is a long distance effect that can be captured by the hydrodynamical regime of the scalar flow far away from the BH. This dynamical friction term has the same form as the celebrated Chandrasekhar collisionless result, albeit with a well-defined Coulomb logarithm. Indeed the infra-red cut-off is naturally provided by the size of the scalar cloud, which is set by the scalar mass and coupling, whilst the ultra-violet behaviour corresponds to the distance from the BH where the velocity field is significantly perturbed by the BH. As a result, supersonic BH are slowed down by both the accretion drag and the dynamical friction. This effect will be potentially detectable by future gravitational wave experiments as it influences the phase of the gravitational wave signal from inspiralling binaries

Gravitational waves from binary black holes in a self-interacting scalar dark matter cloud

We investigate the imprints of accretion and dynamical friction on the gravitational-wave signals emitted by binary black holes embedded in a scalar dark matter cloud. As a key feature in this work, we focus on scalar fields with a repulsive self-interaction that balances against the self-gravity of the cloud. To a first approximation, the phase of the gravitational-wave signal receives extra correction terms at $-4$PN and $-5.5$PN orders, relative to the prediction of vacuum general relativity, due to accretion and dynamical friction, respectively. Future observations by LISA and B-DECIGO have the potential to detect these effects for a large range of scalar masses~$m_\mathrm{DM}$ and self-interaction couplings~$\lambda_4$; observations by ET and Advanced~LIGO could also detect these effects, albeit in a more limited region of parameter space. Crucially, we find that even if a dark matter cloud has a bulk density~$\rho_0$ that is too dilute to be detected via the effects of dynamical friction, the imprints of accretion could still be observable because it is controlled by the independent scale $\rho_a = 4 m_{\rm DM}^4 c^3/(3 \lambda_4 \hbar^3)$. In the models we consider, the infalling dark matter increases in density up to this characteristic scale $\rho_a$ near the Schwarzschild radius, which sets the accretion rate and its associated impact on the gravitational~waveform.Comment: 20 pages, 6 figures, 5 table

Matière noire scalaire auto-interagissante : du freinage gravitationnel aux prédictions sur les ondes gravitationnelles

The absence of direct observations of cold dark matter particles calls for a better understanding of alternative scenarios. In particular, scenarios involving ultralight bosons with a mass below 1 eV have experienced a resurgence of interest in recent years. They preserve the successes of the standard cold dark matter model at large scales but alter the dynamics at galactic scales. Including self-interactions to such scenarios endows dark matter with fluid-like behavior with non-negligible effective pressure, distinguishing it from the conventional ultralight dark matter. We investigated the accretion and dynamicalfriction applied on a black hole moving in a dark matter cloud, both in subsonic and supersonic regimes. Our findings reveal that while the subsonic regime primarily involves accretion, the supersonic regime introduces additional dynamical friction characterized by a term similar to the one obtained by Chandrasekhar for collisionless particles. Nonetheless, in both regimes, the magnitude of the accretion force and dynamical friction remains lower than that observed for cold or collisionless ultralight dark matter. In this framework, we analyzed the effects of these forces on the gravitational-wave signals emitted by binary black holes inside a self-interacting scalar field dark matter cloud. To a fist approximation, correction terms at -4PN and -5.5PN orders appear, exerting an influence on the phase of the gravitational-wave signal. Prospective observations by LISA and B-DECIGO have the potential to detect these effects across a broad spectrum of scalar masses and self-interaction couplings. Our analysis demonstrates that the instances in which the detection of these effects is most probable are Extreme Mass Ratio Inspirals (EMRIs) observed by LISA. Presently, this approach stands as the sole means to constrain self-interacting scalar dark matter with clouds smaller than 0.1 pc.L’absence d’observations directes de la matière noire froide motive une meilleure compréhension des scénarios alternatifs. En particulier, les scénarios impliquant des bosons ultralégers de masse inférieure à 1 eV ont connu un regain d’intérêt ces dernières années. Ils préservent les succès du modèle standard de matière noire froide à grande échelle, mais altèrent la dynamique aux échelles galactiques. L’ajout d’auto-interactions à de tels scénarios confère à la matière noire un comportement semblable à celui d’un fluide avec une pression effective non négligeable, la distinguant de la matière noire ultralégère conventionnelle. Nous avons étudié l’accrétion et la friction dynamique appliquée sur un trou noir se déplaçant dans un nuage de matière noire, tant dans le régime subsonique que supersonique. Nos résultats révèlent que si le régime subsonique implique principalement l’accrétion, le régime supersonique introduit une friction dynamique supplémentaire caractérisée par un terme similaire à celui obtenu par Chandrasekhar dans le cas de particules sans collisions. Néanmoins, dans les deux régimes, l’intensité de la force d’accrétion et de la friction dynamique reste inférieure à celle observée pour la matière noire froide ou ultra-légère sans collisions. En utilisant ces résultats, nous avons analysé les effets de ces forces sur les signaux d’ondes gravitationnelles émis par des binaires de trous noirs se trouvant à l’intérieur d’un nuage de matière noire scalaire auto-interagissant. En première approximation, des termes de correction aux ordres -4PN et -5.5PN apparaissent, exerçant une influence sur la phase du signal d’ondes gravitationnelles. Les observations prospectives de LISA et de B-DECIGO ont le potentiel de détecter ces effets sur un large spectre de masses scalaires et de couplages d’auto-interactions. Bien que des détecteurs tels que ET et Advanced LIGO puissent également identifier ces effets, leurs capacités de détection sont limitées à un espace de paramètres plus restreint. Notre analyse démontre que les cas où la détection de ces effets est la plus probable sont les Inspirales à Rapport de Mass Extrême (EMRIs) observées par LISA. Actuellement, cette approche est la seule permettant de contraindre la matière noire scalaire auto-interagissante ayant des nuages de dimensions inférieures à 0,1 pc

Matière noire scalaire auto-interagissante : du freinage gravitationnel aux prédictions sur les ondes gravitationnelles

The absence of direct observations of cold dark matter particles calls for a better understanding of alternative scenarios. In particular, scenarios involving ultralight bosons with a mass below 1 eV have experienced a resurgence of interest in recent years. They preserve the successes of the standard cold dark matter model at large scales but alter the dynamics at galactic scales. Including self-interactions to such scenarios endows dark matter with fluid-like behavior with non-negligible effective pressure, distinguishing it from the conventional ultralight dark matter. We investigated the accretion and dynamicalfriction applied on a black hole moving in a dark matter cloud, both in subsonic and supersonic regimes. Our findings reveal that while the subsonic regime primarily involves accretion, the supersonic regime introduces additional dynamical friction characterized by a term similar to the one obtained by Chandrasekhar for collisionless particles. Nonetheless, in both regimes, the magnitude of the accretion force and dynamical friction remains lower than that observed for cold or collisionless ultralight dark matter. In this framework, we analyzed the effects of these forces on the gravitational-wave signals emitted by binary black holes inside a self-interacting scalar field dark matter cloud. To a fist approximation, correction terms at -4PN and -5.5PN orders appear, exerting an influence on the phase of the gravitational-wave signal. Prospective observations by LISA and B-DECIGO have the potential to detect these effects across a broad spectrum of scalar masses and self-interaction couplings. Our analysis demonstrates that the instances in which the detection of these effects is most probable are Extreme Mass Ratio Inspirals (EMRIs) observed by LISA. Presently, this approach stands as the sole means to constrain self-interacting scalar dark matter with clouds smaller than 0.1 pc.L’absence d’observations directes de la matière noire froide motive une meilleure compréhension des scénarios alternatifs. En particulier, les scénarios impliquant des bosons ultralégers de masse inférieure à 1 eV ont connu un regain d’intérêt ces dernières années. Ils préservent les succès du modèle standard de matière noire froide à grande échelle, mais altèrent la dynamique aux échelles galactiques. L’ajout d’auto-interactions à de tels scénarios confère à la matière noire un comportement semblable à celui d’un fluide avec une pression effective non négligeable, la distinguant de la matière noire ultralégère conventionnelle. Nous avons étudié l’accrétion et la friction dynamique appliquée sur un trou noir se déplaçant dans un nuage de matière noire, tant dans le régime subsonique que supersonique. Nos résultats révèlent que si le régime subsonique implique principalement l’accrétion, le régime supersonique introduit une friction dynamique supplémentaire caractérisée par un terme similaire à celui obtenu par Chandrasekhar dans le cas de particules sans collisions. Néanmoins, dans les deux régimes, l’intensité de la force d’accrétion et de la friction dynamique reste inférieure à celle observée pour la matière noire froide ou ultra-légère sans collisions. En utilisant ces résultats, nous avons analysé les effets de ces forces sur les signaux d’ondes gravitationnelles émis par des binaires de trous noirs se trouvant à l’intérieur d’un nuage de matière noire scalaire auto-interagissant. En première approximation, des termes de correction aux ordres -4PN et -5.5PN apparaissent, exerçant une influence sur la phase du signal d’ondes gravitationnelles. Les observations prospectives de LISA et de B-DECIGO ont le potentiel de détecter ces effets sur un large spectre de masses scalaires et de couplages d’auto-interactions. Bien que des détecteurs tels que ET et Advanced LIGO puissent également identifier ces effets, leurs capacités de détection sont limitées à un espace de paramètres plus restreint. Notre analyse démontre que les cas où la détection de ces effets est la plus probable sont les Inspirales à Rapport de Mass Extrême (EMRIs) observées par LISA. Actuellement, cette approche est la seule permettant de contraindre la matière noire scalaire auto-interagissante ayant des nuages de dimensions inférieures à 0,1 pc

Matière noire scalaire auto-interagissante : du freinage gravitationnel aux prédictions sur les ondes gravitationnelles

L’absence d’observations directes de la matière noire froide motive une meilleure compréhension des scénarios alternatifs. En particulier, les scénarios impliquant des bosons ultralégers de masse inférieure à 1 eV ont connu un regain d’intérêt ces dernières années. Ils préservent les succès du modèle standard de matière noire froide à grande échelle, mais altèrent la dynamique aux échelles galactiques. L’ajout d’auto-interactions à de tels scénarios confère à la matière noire un comportement semblable à celui d’un fluide avec une pression effective non négligeable, la distinguant de la matière noire ultralégère conventionnelle. Nous avons étudié l’accrétion et la friction dynamique appliquée sur un trou noir se déplaçant dans un nuage de matière noire, tant dans le régime subsonique que supersonique. Nos résultats révèlent que si le régime subsonique implique principalement l’accrétion, le régime supersonique introduit une friction dynamique supplémentaire caractérisée par un terme similaire à celui obtenu par Chandrasekhar dans le cas de particules sans collisions. Néanmoins, dans les deux régimes, l’intensité de la force d’accrétion et de la friction dynamique reste inférieure à celle observée pour la matière noire froide ou ultra-légère sans collisions. En utilisant ces résultats, nous avons analysé les effets de ces forces sur les signaux d’ondes gravitationnelles émis par des binaires de trous noirs se trouvant à l’intérieur d’un nuage de matière noire scalaire auto-interagissant. En première approximation, des termes de correction aux ordres -4PN et -5.5PN apparaissent, exerçant une influence sur la phase du signal d’ondes gravitationnelles. Les observations prospectives de LISA et de B-DECIGO ont le potentiel de détecter ces effets sur un large spectre de masses scalaires et de couplages d’auto-interactions. Bien que des détecteurs tels que ET et Advanced LIGO puissent également identifier ces effets, leurs capacités de détection sont limitées à un espace de paramètres plus restreint. Notre analyse démontre que les cas où la détection de ces effets est la plus probable sont les Inspirales à Rapport de Mass Extrême (EMRIs) observées par LISA. Actuellement, cette approche est la seule permettant de contraindre la matière noire scalaire auto-interagissante ayant des nuages de dimensions inférieures à 0,1 pc.The absence of direct observations of cold dark matter particles calls for a better understanding of alternative scenarios. In particular, scenarios involving ultralight bosons with a mass below 1 eV have experienced a resurgence of interest in recent years. They preserve the successes of the standard cold dark matter model at large scales but alter the dynamics at galactic scales. Including self-interactions to such scenarios endows dark matter with fluid-like behavior with non-negligible effective pressure, distinguishing it from the conventional ultralight dark matter. We investigated the accretion and dynamicalfriction applied on a black hole moving in a dark matter cloud, both in subsonic and supersonic regimes. Our findings reveal that while the subsonic regime primarily involves accretion, the supersonic regime introduces additional dynamical friction characterized by a term similar to the one obtained by Chandrasekhar for collisionless particles. Nonetheless, in both regimes, the magnitude of the accretion force and dynamical friction remains lower than that observed for cold or collisionless ultralight dark matter. In this framework, we analyzed the effects of these forces on the gravitational-wave signals emitted by binary black holes inside a self-interacting scalar field dark matter cloud. To a fist approximation, correction terms at -4PN and -5.5PN orders appear, exerting an influence on the phase of the gravitational-wave signal. Prospective observations by LISA and B-DECIGO have the potential to detect these effects across a broad spectrum of scalar masses and self-interaction couplings. Our analysis demonstrates that the instances in which the detection of these effects is most probable are Extreme Mass Ratio Inspirals (EMRIs) observed by LISA. Presently, this approach stands as the sole means to constrain self-interacting scalar dark matter with clouds smaller than 0.1 pc

Subsonic accretion and dynamical friction for a black hole moving through a self-interacting scalar dark matter cloud

We investigate the flow around a black hole moving through a cloud of self-interacting scalar dark matter. We focus on the large scalar mass limit, with quartic self-interactions, and on the subsonic regime. We show how the scalar field behaves as a perfect gas of adiabatic index $\gamma_{\rm ad}=2$ at large radii while the accretion rate is governed by the relativistic regime close to the Schwarzschild radius. We obtain analytical results thanks to large-radius expansions, which are also related to the small-scale relativistic accretion rate. We find that the accretion rate is greater than for collisionless particles, by a factor $c/c_s \gg 1$, but smaller than for a perfect gas, by a factor $c_s/c \ll 1$, where $c_s$ is the speed of sound. The dynamical friction is smaller than for a perfect gas, by the same factor $c_s/c \ll 1$, and also smaller than Chandrasekhar's result for collisionless particles, by a factor $c_s/(cC)$, where $C$ is the Coulomb logarithm. It is also smaller than for fuzzy dark matter, by a factor $v_0/c \ll 1$

Supersonic friction of a black hole traversing a self-interacting scalar dark matter cloud

International audienceBlack Holes (BH) traversing a dark matter cloud made out of a self-interacting scalar soliton are slowed down by two complementary effects. At low subsonic speeds, the BH accretes dark matter and this is the only source of dragging along its motion, if we neglect the backreaction of the cloud self-gravity. The situation changes at larger supersonic speeds where a bow shock in front of the BH is created. This leads to the emergence of an additional friction term, associated with the gravitational and scalar pressure interactions and with the wake behind the moving BH. This is a long distance effect that can be captured by the hydrodynamical regime of the scalar flow far away from the BH. This dynamical friction term has the same form as the celebrated Chandrasekhar collisionless result, albeit with a well-defined Coulomb logarithm. Indeed the infra-red cut-off is naturally provided by the size of the scalar cloud, which is set by the scalar mass and coupling, whilst the ultra-violet behaviour corresponds to the distance from the BH where the velocity field is significantly perturbed by the BH. As a result, supersonic BH are slowed down by both the accretion drag and the dynamical friction. This effect will be potentially detectable by future gravitational wave experiments as it influences the phase of the gravitational wave signal from inspiralling binaries

Baryogenesis through asymmetric Hawking radiation from primordial black holes as dark matter

International audienceWe examine the extent to which primordial black holes (PBHs) can constitute the observed dark matter while also giving rise to the measured matter-antimatter asymmetry and account for the observed baryon abundance through asymmetric Hawking radiation generated by a derivative coupling of curvature to the baryon-lepton current. We consider both broad and monochromatic mass spectra for this purpose. For the monochromatic spectrum we find that the correct dark matter and baryon energy densities are recovered for peak masses of the spectrum of Mpk≥1012  kg whereas for the broad case the observed energy densities can be reproduced regardless of peak mass. Adopting some simplifications for the early-time expansion history as a first approximation, we also find that the measured baryon asymmetry can be recovered within an order of magnitude. We argue furthermore that the correct value of the baryon-lepton yield can in principle be retrieved for scenarios where a significant amount of the radiation is produced by PBH decay during or after reheating, as is expected when the decaying PBHs also cause reheating, or when an early matter-dominated phase is considered. We conclude from this first analysis that the model merits further investigation