Scalar Field Dark Matter Research Articles

Parametric resonance of gravitational waves in general scalar-tensor theories

Gravitational waves offer a potent mean to test the underlying theory of gravity. In general theories of gravity, such as scalar-tensor theories, one expects modifications in the friction term and the sound speed in the gravitational wave equation. In that case, rapid oscillations in such coefficients, e.g. due to an oscillating scalar field, may lead to narrow parametric resonances in the gravitational wave strain. We perform a general analysis of such possibility within DHOST theories. We use disformal transformations to find the theory space with larger resonances, within an effective field theory approach. We then apply our formalism to a non-minimally coupled ultra-light dark matter scalar field, assuming the presence of a primordial gravitational wave background, e.g., from inflation. We find that the resonant peaks in the spectral density may be detectable by forthcoming detectors such as LISA, Taiji, Einstein Telescope and Cosmic Explorer.

Accreting black holes in dark matter halos

We examine the thin accretion disk behaviors surrounding black holes embedded in cold dark matter halos and scalar field dark matter halos. We first calculate the event horizons and derive the equations of motion and effective potential in black hole geometries with different dark matter halos. We then compute the specific energy, specific angular momentum, and angular velocity of particles moving along circular orbits. We also derive the effective potentials to find the locations of the innermost stable circular orbit (ISCO) and compare them to the Schwarzschild and Kerr black holes without the dark matter halos. We also use the observed ISCO of the supermassive black hole at the Galactic Center of the Milky Way, Sagittarius A*, to constrain the dark matter halos. Published by the American Physical Society 2024

Scalar field dark matter around charged black holes

Scalar field dark matter around charged black holes

Hybrid model of condensate and particle dark matter: Linear perturbations in the hydrodynamic limit

We analyze perturbations of self-interacting, scalar field dark matter that contains modes in both a coherent condensate state and an incoherent particlelike state. Starting from the coupled equations for the condensate, the particles’ phase-space distribution, and their mutual gravitational potential, first derived from first principles in earlier work by the authors, we derive a hydrodynamic limit of two coupled fluids and study their linearized density perturbations in an expanding universe, also including particle pressure under an assumption for an equation of state consistent with the dynamical equations. We find that away from the condensate-only or particle-only limits, and for certain ranges of the parameters, such self-interacting mixtures can significantly enhance the density power spectrum above the standard linear ΛCDM value at localized wave numbers, even pushing structure formation into the nonlinear regime earlier than expected in ΛCDM for these scales. We also note that such mixtures can lead to degeneracies between models with different boson masses and self-coupling strengths, in particular, between self-coupled models and noncoupled fuzzy dark matter made up of heavier bosons. These findings open up the possibility of a richer phenomenology in scalar field dark matter models and could further inform efforts to place observational limits on their parameters. Published by the American Physical Society 2024

Possibility of the Traversable Wormholes in the Galactic Halos within 4D Einstein–Gauss–Bonnet Gravity

AbstractRecently, there has been significant interest regarding the regularization of a limit of Einstein–Gauss–Bonnet (EGB) gravity. This regularization involves re‐scaling the Gauss–Bonnet (GB) coupling constant as , which bypasses Lovelock's theorem and avoids Ostrogradsky instability. A noteworthy observation is that the maximally or spherically symmetric solutions for all the regularized gravities coincide in the scenario. Considering this, the wormhole solutions in the galactic halos are investigated based on three different choices of dark matter (DM) profiles, such as Universal Rotation Curve, Navarro–Frenk–White, and Scalar Field Dark Matter with the framework of EGB gravity. Also, the Karmarkar condition is used to find the exact solutions for the shape functions under different non‐constant redshift functions. The energy conditions for each DM profile are discussed and the influence of GB coefficient in violating energy conditions are noticed, especially null energy conditions. Further, some physical features of wormholes, viz. complexity factor, active gravitational mass, total gravitational energy, and embedding diagrams, have been explored.

Scalar field dark matter: impact of supernova-driven blowouts on the soliton structure of low-mass dark matter haloes

ABSTRACT We present the first study on the gravitational impact of supernova feedback in an isolated soliton and a spherically symmetric dwarf scalar field dark matter (SFDM) halo of virial mass $1\times 10^{10}\,\mathrm{M_\odot }$. We use a boson mass $m=10^{-22}\,\mathrm{eV\,c^{-2}}$ and a soliton core $r_\mathrm{ c} \approx 0.7$ kpc, comparable to typical half-light radii of Local Group dwarf galaxies. We simulate the rapid gas removal from the centre of the soliton by a concentric external time-dependent Hernquist potential. We explore two scenarios of feedback blowouts: (i) a massive single burst and (ii) multiple consecutive blowouts injecting the same total energy to the system, including various magnitudes for the blowouts in both scenarios. In all cases, we find one single blowout has a stronger effect on reducing the soliton central density. Feedback leads to central soliton densities that oscillate quasi-periodically for an isolated soliton and stochastically for an SFDM halo. The range in the density amplitude depends on the strength of the blowout; however, we observe typical variations of a factor of $\geqslant$2. One important consequence of the stochastic fluctuating densities is that, if we had no prior knowledge of the system evolution, we can only know the configuration profile at a specific time within some accuracy. By fitting soliton profiles at different times to our simulated structures, we found the (1$\sigma$) scatter of their time-dependent density profiles. For configurations within the 1$\sigma$ range, we find the inferred boson mass is typically less than 20 per cent different from the real value used in our simulations. Finally, we compare the observed dynamical masses of field dwarf galaxies in our Local Group with the implied range of viable solitons from our simulations and find good agreement.

Constraining self-interacting scalar field dark matter from the black hole shadow of the Event Horizon Telescope

Constraining self-interacting scalar field dark matter from the black hole shadow of the Event Horizon Telescope

Simple test with rotation curves for the multistate scalar field dark matter model

Simple test with rotation curves for the multistate scalar field dark matter model

TDiff invariant field theories for cosmology

We study scalar field theories invariant under transverse diffeomorphismsin cosmological contexts. We show that in the geometric optics approximation, the corresponding particles move along geodesics and contribute with the same active mass (energy) to the gravitational field as in Diff invariant theories. However, for low-frequency (super-Hubble) modes, the contributions to the energy-momentum tensor differ from that of Diff invariant theories. This opens up a wide range of possibilities for cosmological model building. As an example, we show that the simplest TDiff invariant scalar field theory with only kinetic term could drive inflation and generate a nearly scale invariant (red-tilted) spectrum of density fluctuations. We also present a detailed analysis of cosmological perturbations and show that the breaking of full Diff invariance generically induces new non-adiabatic pressure perturbations. A simple scalar field dark matter model based on a purely kinetic term that exhibits the same clustering properties as standard cold dark matter is also presented.

Kinetically coupled scalar fields model and cosmological tensions

ABSTRACT In this paper, we investigate the kinetically coupled early dark energy (EDE) and scalar field dark matter to address cosmological tensions. The EDE model presents an intriguing theoretical approach to resolving the Hubble tension, but it exacerbates the large-scale structure tension. We consider the interaction between dark matter and EDE, such that the drag of dark energy on dark matter suppresses structure growth, which can alleviate large-scale structure tension. We replace cold dark matter with scalar field dark matter, which has the property of suppressing structure growth on small scales. We employed the Markov Chain Monte Carlo method to constrain the model parameters, our new model reveals a non-zero coupling constant of 0.030 ± 0.026 at a 68 per cent confidence level. The coupled model yields the Hubble constant value of $72.38^{+0.71}_{-0.82}$ km s−1 Mpc−1, which resolves the Hubble tension. However, similar to the EDE model, it also obtains a larger S8 value compared to the ΛCDM model, further exacerbating the large-scale structure tension. The EDE model and the new model yield the best-fitting values of 0.8316 and 0.8146 for S8, respectively, indicating that the new model partially alleviates the negative effect of the EDE model. However, this signature disappears when comparing marginalized posterior probabilities, and both models produce similar results. The values obtained from the EDE model and the new model are $0.822^{+0.011}_{-0.0093}$ and $0.819^{+0.013}_{-0.0092}$, respectively, at a 68 per cent confidence level.

Short review of the main achievements of the scalar field, fuzzy, ultralight, wave, BEC dark matter model

The Scalar Field Dark Matter model has been known in various ways throughout its history; Fuzzy, BEC, Wave, Ultralight, Axion-like Dark Matter, etc. All of them consist in proposing that dark matter of the universe is a spinless field Φ that follows the Klein-Gordon (KG) equation of motion □Φ −dV/dΦ = 0, for a given scalar field potentialV. The difference between different models is sometimes the choice of the scalar field potentialV. In the literature we find that people usually work in the non-relativistic, weak-field limit of the Klein-Gordon equation, where it transforms into the Schrödinger equation and the Einstein equations into the Poisson equation, reducing the KG-Einstein system, to the Schrödinger-Poisson system. In this paper, we review some of the most interesting achievements of this model from the historical point of view and its comparison with observations, showing that this model could be the last answer to the question about the nature of dark matter in the universe.

Cosmological evolution of scalar field dark matter in the class code: Accuracy and precision of numerical solutions

Cosmological evolution of scalar field dark matter in the class code: Accuracy and precision of numerical solutions

Proca stars with dark photons from spontaneous symmetry breaking of the scalar field dark matter

Recently, the Scalar Field Dark Matter (SFDM) model (also known as Fuzzy, Wave, Bose-Einstein, Ultra-light Dark Matter) has gained a lot of attention because it has provided simpler and more natural explanations for various phenomena observed in galaxies, as a natural explanation for the center of galaxies, the number of satellite galaxies around their host and, more recently, a natural explanation for anomalous trajectories of satellite galaxies called Vast Polar Orbits (VPO) observed in various galaxies. In the present work we study the assumption that the SFDM is a type of charged dark boson whose gauge charge is associated with the Dark Photon (DP). Inspired by these results, we study the formation of compact bosonic objects, such as Boson Stars (BS) and focus on the possibility that, due to spontaneous U(1) SFDM symmetry breaking, the DP may acquire mass and form compact objects like Proca Stars (PS). If this is true, we can expect measurable effects on the electromagnetic field of the Standard Model (SM) of particles due to their interaction with the DP on the formation of compact objects.

Constraints via the Event Horizon Telescope for Black Hole Solutions with Dark Matter under the Generalized Uncertainty Principle Minimal Length Scale Effect

AbstractFour spherically symmetric but non‐asymptotically flat black hole solutions surrounded with spherical dark matter distribution perceived under the minimal length scale effect is derived via the generalized uncertainty principle. Here, the effect of this quantum correction, described by the parameter , is considered on a toy model galaxy with dark matter and the three well‐known dark matter distributions: the cold dark matter, scalar field dark matter, and the universal rotation curve. The aim is to find constraints to by applying these solutions to the known supermassive black holes: Sagittarius A (Sgr. A*) and Messier 87* (M87*), in conjunction with the available Event Horizon telescope. The effect of is then examined on the event horizon, photonsphere, and shadow radii, where unique deviations from the Schwarzschild case are observed. As for the shadow radii, bounds are obtained for the values of on each black hole solution at confidence level. The results revealed that under minimal length scale effect, black holes can give positive (larger shadow) and negative values (smaller shadow) of , which are supported indirectly by laboratory experiments and astrophysical or cosmological observations, respectively.

Upper limit on scalar field dark matter from LIGO-Virgo third observation run

Upper limit on scalar field dark matter from LIGO-Virgo third observation run

Accretion of self-interacting scalar field dark matter onto a Reissner-Nordström black hole

Accretion of self-interacting scalar field dark matter onto a Reissner-Nordström black hole

Logarithmically divergent friction on ultrarelativistic bubble walls

We calculate the friction experienced by ultrarelativistic bubble walls resulting from the 1 → 2 light-to-heavy transition process, with finite-wall-width effects fully taken into account. In this process, the light particle is excited from the order-parameter scalar field, while the two heavy particles are excitations of a dark matter scalar field. Unlike earlier estimates suggesting a friction scaling as γw 0, where γw represents the Lorentz factor of the wall velocity, our more precise numerical analysis reveals a logarithmic dependence of the friction on γw . We offer a numerical fit to capture this frictional pressure accurately. Our analysis verifies that the friction stemming from the 1 → 2 light-to-heavy transition is typically much smaller than the friction from the 1 → 1 transmission of the dark matter particles.

The MUSE-Faint survey

Aims. We use the stellar line-of-sight velocities of Antlia B (Ant B), a faint dwarf galaxy in the NGC 3109 association, to derive constraints on the fundamental properties of scalar field dark matter (SFDM), which was originally proposed to solve the small-scale problems faced by cold dark matter models. Methods. We used the first spectroscopic observations of Ant B, a distant (d ∼ 1.35 Mpc) faint dwarf (MV = −9.7, M⋆ ∼ 8 × 105 M⊙), from MUSE-Faint, a survey of ultra-faint dwarfs conducted using the Multi Unit Spectroscopic Explorer. By measuring the line-of-sight velocities of stars in the 1′×1′ field of view, we identified 127 stars as members of Ant B, which enabled us to model its dark matter density profile with the Jeans modelling code GRAVSPHERE. We implemented a model for SFDM into GRAVSPHERE and used this to place constraints on the self-coupling strength of this model. Results. We find a virial mass of M200 ≈ 1.66−0.92+2.51 × 109 M⊙ and a concentration parameter of c200 ≈ 17.38−4.20+6.06 for Ant B. These results are consistent with the mass-concentration relations in the literature. We constrain the characteristic length scale of the repulsive self-interaction RTF of the SFDM model to RTF ≲ 180 pc (68% confidence level), which translates to a self-coupling strength of g/m2c4 ≲ 5.2 × 10−20 eV−1 cm3. The constraint on the characteristic length scale of the repulsive self-interaction is inconsistent with the value required to match observations of the cores of dwarf galaxies in the Local Group, suggesting that the cored density profiles of those galaxies are not caused by SFDM.

Halo formation and evolution in scalar field dark matter and cold dark matter: New insights from the fluid approach

Halo formation and evolution in scalar field dark matter and cold dark matter: New insights from the fluid approach

Testing the mean field theory of scalar field dark matter

Scalar field dark matter offers an interesting alternative to the traditional WIMP dark matter picture. Astrophysical and cosmological simulations are useful to constraining the mass of the dark matter particle in this model. This is particularly true at low mass where the wavelike nature of the dark matter particle manifests on astrophysical scales. These simulations typical use a classical field approximation. In this work, we look at extending these simulations to include quantum corrections. We look into both the ways in which large corrections impact the predictions of scalar field dark matter, and the timescales on which these corrections grow large. Corrections tend to lessen density fluctuations and increase the effect of “quantum pressure”. During collapse, these corrections grow exponentially, quantum corrections would become important in about \sim 30∼30 dynamical times. This implies that the predictions of classical field simulations may differ from those with quantum corrections for systems with short dynamical times.