Fraction Of Dark Matter Research Articles

Manifestation of antiquark nuggets in collisions with the Earth

Antiquark nuggets are hypothetical compact composite objects conjectured to account for a significant fraction of dark matter in the Universe. In contrast to quark nuggets, these objects consist of antimatter. They may remain undetected if they possess a sufficiently small cross section relative to their mass. In this paper, we investigate the allowed region in the parameter space of this model that is consistent with the observed neutrino flux from the Sun and the Earth, and the nonobservation of seismic events with specific signatures of dark matter particles. We found the allowed values of the antibaryon charge number in this model to be in the interval 2×1024<A<8×1025, while the probability of nucleon annihilation upon collisions with the antiquark core is constrained by 0.1≲κ<0.25. These values of A and κ are, however, constrained by the IceCube experiment and nonobservation of impacts of antiquark nuggets on humans. Although very large values of the antibaryon charge, A>1033, are not fully excluded by the present study, we show that they conflict with the nonobservation of rare catastrophic explosionlike events on the Earth. Published by the American Physical Society 2025

Early formation of supermassive black holes from the collapse of strongly self-interacting dark matter

Evidence for high-redshift supermassive black holes challenges standard scenarios for how such objects form in the early universe. Here, we entertain the possibility that a fraction of the cosmological dark matter could be ultra-strongly self interacting. This would imply that gravothermal collapse occur at early times in the cores of dark matter halos, followed by accretion. We study under which conditions on the abundance and interaction strength and structure of such ultra self-interacting dark matter the black holes resulting from the end-point of gravothermal core collapse can seed the observed, early-forming supermassive black holes. We find, depending on the velocity dependence of the self-interaction cross section, a bimodal structure in the favored parameter space, where data points to either a small collapsing dark matter fraction with a large cross section, or a large fraction and a relatively small cross section. While self-interaction cross sections with different velocity dependence can explain observations, we find that the best, self-consistent results correspond to a Rutherford-like self-interaction, typical of long-range dark-sector forces with light mediators. We discuss complementary observational probes if this scenario is realized in nature, focusing especially on the expected intermediate mass black holes predicted to exist in smaller galaxies.

Primordial black hole formation in a dust bouncing model

Linear scalar cosmological perturbations have increasing spectra in the contracting phase of bouncing models. We study the conditions for which these perturbations may collapse into primordial black holes and the hypothesis that these objects constitute a fraction of dark matter. We compute the critical density contrast that describes the collapse of matter perturbations in the flat-dust bounce model with a parametric solution, obtained from the Lemaitre-Tolman-Bondi metric that represents the spherical collapse. We discuss the inability of the Newtonian gauge to describe perturbations in contracting models as the perturbative hypothesis does not hold in such cases. We carry the calculations for a different Gauge choice and compute the perturbations' power spectra numerically. Finally, assuming a Gaussian distribution, we compute the primordial black hole abundance with the Press-Schechter formalism and compare it with observational constraints. From our analysis, we conclude that the primordial black hole formation in a dust-dominated contracting phase does not lead to a significant mass fraction of primordial black holes in dark matter today.

Attenuation of cosmic ray electron boosted dark matter

We consider a model of boosted dark matter (DM), where a fraction of DM is upscattered to relativistic energies by cosmic ray electrons. Such interactions responsible for boosting the DM also attenuate its flux at the Earth. Considering a simple model of constant interaction cross section, we make analytical estimates of the variation of the attenuation ceiling with the DM mass and confirm it numerically. We then extend our analysis to a Z′-mediated leptophilic DM model. We show that the attenuation ceiling remains nearly model independent for DM and mediator particles heavier than the electron, challenging some previous discussions on this topic. Using the XENONnT direct detection experiment, we illustrate how constraints based on energy-dependent scattering can significantly differ from those based on an assumed constant cross section. This highlights the importance of reevaluating these constraints in the context of specific models. Published by the American Physical Society 2024

The density profile of Milky Way dark matter halo constrained from the OGLE microlensing sky map

We report the detection of a core with a size of 282 $^ $ pc in the center of Milky Way dark matter halo at the $68<!PCT!>$ confidence level. It was detected using the microlensing event-rate sky map data from the optical gravitational lensing experiment (OGLE) survey. We applied the spatial information of the microlensing sky map and modeled it with the detailed Milky Way dark matter halo core-cusp profile, and with the fraction of dark matter in the form of mini dark matter structure (MDMS; $f_ MDMS MDMS DM $) such as a primordial black hole, Earth-mass subhalos, or floating planets. This sky map can simultaneously constrain $f_ MDMS $ and the core size without a strong degeneracy while fully considering the mass function of Milky Way stellar components from the bulge and disk.

Dynamics of cosmological phase crossover during Bose–Einstein condensation of dark matter in Tsallis cosmology

During the cosmic evolution process, as the temperature of a cosmological boson gas falls below a certain threshold, a Bose–Einstein condensation process can occur at various points throughout the cosmic history of the Universe. In this model, dark matter, conceptualized as a non-relativistic, Newtonian gravitational condensate is governed by the Gross–Pitaevskii–Poisson system. In our present study, we investigate the Bose–Einstein condensation process of bosonic DM by treating it as an approximate first-order phase transition within a modified cosmological framework, known as Tsallis cosmology. We examine the evolution of relevant physical quantities characterizing the evolution dynamics of the Universe, including energy density, temperature, redshift, scale factor, Hubble parameter, and dimensionless deceleration parameter before, during, and following the Bose–Einstein condensation phase transition takes place. Additionally, we especially investigate the specific era of the evolution of the Universe characterized by a mixture of normal and condensate phases of dark matter. We analyze the behavior of temporal evolution of an important time-dependent parameter, called the condensate dark matter fraction throughout the condensation process and find the time duration of condensation of dark matter in the Tsallis cosmological model. We see that the presence of Bose–Einstein condensate dark matter in the framework of Tsallis-modified cosmology significantly alters the cosmological evolution of the Universe as compared to the standard model of cosmology. We also find for a typical value of Tsallis non-extensive parameter β=0.35, the model could explain an accelerated Universe without invoking any additional energy component and solve the age problem of our Universe.

High-redshift, Small-scale Tests of Ultralight Axion Dark Matter Using Hubble and Webb Galaxy UV Luminosities

We calculate the abundance of UV-bright galaxies in the presence of ultralight axion (ULA) dark matter (DM), finding that axions suppress their formation with a non-trivial dependence on redshift and luminosity. We set limits on axion DM using UV luminosity function (UVLF) data, excluding a single axion as all the DM for m ax < 10−21.6 eV and limiting axions with −26≤log(max/eV)≤−23 to be less than 22% of the DM (both at 95% credibility). These limits use UVLF measurements from 24,000 sources from the Hubble Space Telescope (HST) at redshifts 4 ≤ z ≤ 10. We marginalize over a parametric model connecting halo mass and UV luminosity. Our results bridge a window in axion mass and fraction previously unconstrained by cosmological data, between large-scale cosmic microwave background and galaxy clustering and the small-scale Lyα forest. These high-z measurements provide a powerful consistency check of low-z tests of axion DM, including the recent hint for a sub-dominant ULA DM fraction in Lyα forest data. We also consider a sample of 25 spectroscopically confirmed high-z galaxies from the James Webb Space Telescope (JWST), finding these data to be consistent with HST. Combining HST and JWST UVLF data does not improve our constraints beyond HST alone, but future JWST measurements have the potential to improve these results. We also find an excess of low-mass halos (<109 M ⊙) at z < 3, which could be probed by subgalactic structure probes (e.g., stellar streams, satellite galaxies, and strong lensing).

How Do Primordial Black Holes Change the Halo Mass Function and Structure?

We examine the effects of massive primordial black holes (PBHs) on cosmic structure formation, employing both a semianalytical approach and cosmological simulations. Our simulations incorporate PBHs with a monochromatic mass distribution centered around 106 M ⊙, constituting a fraction of 10−2 to 10−4 of the dark matter (DM) in the Universe, with the remainder being collisionless particle DM. Additionally, we conduct a ΛCDM simulation for comparative analysis with runs that include PBHs. At smaller scales, halos containing PBHs exhibit similar density and velocity dispersion profiles to those without PBHs. Conversely, at larger scales, PBHs can expedite the formation of massive halos and reside at their centers owing to the “seed effect.” To analyze the relative distribution of PBH host halos compared to non-PBH halos, we apply nearest neighbor statistics. Our results suggest that PBH host halos, through gravitational influence, significantly impact the structure formation process, compared to the ΛCDM case, by attracting and engulfing nearby newly formed minihalos. Should PBHs constitute a fraction of DM significantly larger than ∼10−3, almost all newly formed halos will be absorbed by PBH-seeded halos. Consequently, our simulations predict a bimodal feature in the halo mass function, with most of the massive halos containing at least one PBH at their core and the rest being less massive non-PBH halos.

Curbing PBHs with PTAs

Sizeable primordial curvature perturbations needed to seed a population of primordial black holes (PBHs) will be accompanied by a scalar-induced gravitational wave signal that can be detectable by pulsar timing arrays (PTA). We derive conservative bounds on the amplitude of the scalar power spectrum at the PTA frequencies and estimate the implied constraints on the PBH abundance. We show that only a small fraction of dark matter can consist of stellar mass PBHs when the abundance is calculated using threshold statistics. The strength and the shape of the constraint depend on the shape of the power spectrum and the nature of the non-Gaussianities. We find that constraints on the PBH abundance arise in the mass range 0.1-103 M ⊙, with the sub-solar mass range being constrained only for narrow curvature power spectra. These constraints are softened when positive non-Gaussianity is introduced and can be eliminated when f NL ≳ 5. On the other hand, if the PBH abundance is computed via the theory of peaks, the PTA constraints on PBHs are significantly relaxed, signalling once more the theoretical uncertainties in assessing the PBH abundance.We further discuss how strong positive non-Gaussianites can allow for heavy PBHs to potentially seed supermassive BHs.

Gravitational Wave Constraints on Planetary-Mass Primordial Black Holes Using LIGO O3a Data.

Gravitational waves from subsolar mass inspiraling compact objects would provide almost smoking-gun evidence for primordial black holes (PBHs). We perform the first search for inspiraling planetary-mass compact objects in equal-mass and highly asymmetric mass-ratio binaries using data from the first half of the LIGO-Virgo-KAGRA third observing run. Though we do not find any significant candidates, we determine the maximum luminosity distance reachable with our search to be of O(0.1-100) kpc, and corresponding model-independent upper limits on the merger rate densities to be O(10^{3}-10^{-7}) kpc^{-3} yr^{-1} for systems with chirp masses of O(10^{-4}-10^{-2})M_{⊙}, respectively. Furthermore, we interpret these rate densities as arising from PBH binaries and constrain the fraction of dark matter that such objects could comprise. For equal-mass PBH binaries, we find that these objects would compose less than 4%-100% of DM for PBH masses of 10^{-2}M_{⊙} to 2×10^{-3}M_{⊙}, respectively. For asymmetric binaries, assuming one black hole mass corresponds to a peak in the mass function at 2.5M_{⊙}, a PBH dark-matter fraction of 10% and a second, much lighter PBH, we constrain the mass function of the second PBH to be less than 1 for masses between 1.5×10^{-5}M_{⊙} and 2×10^{-4}M_{⊙}. Our constraints, recently released, are robust enough to be applied to any PBH or exotic compact object binary formation models, and complement existence microlensing results.

Color-flavor locked strange stars admixed with mirror dark matter and the observations of compact stars

We investigate the structure and the tidal deformability of the color-flavor locked strange stars admixed with mirror dark matter. Assuming the stars in the GW170817 event have a mirror-dark-matter core or a mirror-dark-matter halo, the observations of the central compact object within the supernova remnant HESS J1731-347 and the compact objects in the GW190814 and GW170817 events could be explained simultaneously with a pairing gap much smaller than 200 MeV. In contrast, a pairing gap larger than about 200 MeV must be employed without the consideration of a mirror-dark-matter core (halo). More importantly, we find that for the case of the quartic coefficient a 4 < 0.589, if the mass fraction of the mirror dark matter (fD ) of the compact stars in GW170817 is in a certain range (eg., 22.8% < fD < 77.2% for a 4 = 0.55), the minimum allowed value of the pairing gap could be less than 46.5 MeV (i.e., one half of the value of the strange quark mass which is taken as 93 MeV in this paper), which leads to the result that all astrophysical observations mentioned above could be satisfied without violating the conformal bound or the recently proposed positive trace anomally bound.

Impact of primordial black hole dark matter on gas properties at very high redshift: Semianalytical model

Context. Primordial black holes (PBHs) have been proposed as potential candidates for dark matter (DM) and have garnered significant attention in recent years. Aims. Our objective is to delve into the distinct impact of PBHs on the gas properties and their potential role in shaping the cosmic structure. Specifically, we aim to analyze the evolving gas properties while considering the presence of accreting PBHs with varying monochromatic masses and in different quantities. By studying the feedback effects produced by this accretion, our final goal is to assess the plausibility of PBHs as candidates for DM. Methods. We developed a semianalytical model that works on top of the CIELO hydrodynamical simulation around z ∼ 23. This model enables a comprehensive analysis of the evolution of gas properties affected by PBHs. Our focus lies on the temperature and hydrogen abundances, with specific emphasis on the region closest to the halo center. We explore PBH masses of 1, 33, and 100 M⊙, located within mass windows in which a substantial fraction of DM could exist in the form of PBHs. We investigated various DM fractions composed of these PBHs (fPBH &gt; 10−4). Results. Our findings suggest that PBHs with masses of 1 M⊙ and fractions greater than or equal to approximately 10−2 would be ruled out due to the significant changes induced in the gas properties. The same applies to PBHs with a mass of 33 M⊙ and 100 M⊙ and fractions greater than approximately 10−3. These effects are particularly pronounced in the region nearest to the halo center, potentially leading to delayed galaxy formation within halos.

Search for Gravitational-lensing Signatures in the Full Third Observing Run of the LIGO–Virgo Network

Gravitational lensing by massive objects along the line of sight to the source causes distortions to gravitational wave (GW) signals; such distortions may reveal information about fundamental physics, cosmology, and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO-Virgo network. We search for repeated signals from strong lensing by (1) performing targeted searches for subthreshold signals, (2) calculating the degree of overlap among the intrinsic parameters and sky location of pairs of signals, (3) comparing the similarities of the spectrograms among pairs of signals, and (4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by (1) frequency-independent phase shifts in strongly lensed images, and (2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the nondetection of GW lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects.

Primordial Black Hole Dark Matter Simulations Using PopSyCLE

Primordial black holes (PBHs), theorized to have originated in the early Universe, are speculated to be a viable form of dark matter. If they exist, they should be detectable through photometric and astrometric signals resulting from gravitational microlensing of stars in the Milky Way. Population Synthesis for Compact-object Lensing Events, or PopSyCLE, is a simulation code that enables users to simulate microlensing surveys, and is the first of its kind to include both photometric and astrometric microlensing effects, which are important for potential PBH detection and characterization. To estimate the number of observable PBH microlensing events, we modify PopSyCLE to include a dark matter halo consisting of PBHs. We detail our PBH population model, and demonstrate our PopSyCLE + PBH results through simulations of the Optical Gravitational Lensing Experiment-IV (OGLE-IV) and Nancy Grace Roman Space Telescope (Roman) microlensing surveys. We provide a proof-of-concept analysis for adding PBHs into PopSyCLE, and thus include many simplifying assumptions, such as f DM, the fraction of dark matter composed of PBHs, and m¯PBH , mean PBH mass. Assuming m¯PBH=30 M ⊙, we find ∼3.6f DM times as many PBH microlensing events than stellar evolved black hole events, a PBH average peak Einstein crossing time of ∼91.5 days, estimate on order of 102 f DM PBH events within the 8 yr OGLE-IV results, and estimate Roman to detect ∼1000f DM PBH microlensing events throughout its planned microlensing survey.

More on black holes perceiving the dark dimension

In the last two years, the dark dimension scenario has emerged as focal point of many research interests. In particular, it functions as a stepping stone to address the cosmological hierarchy problem and provides a colosseum for dark matter contenders. We reexamine the possibility that primordial black holes (PBHs) perceiving the dark dimension could constitute all of the dark matter in the Universe. We reassess limits on the abundance of PBHs as dark matter candidates from γ-ray emission resulting from Hawking evaporation. We reevaluate constraints from the diffuse γ-ray emission in the direction of the Galactic Center that offer the best and most solid upper limits on the dark matter fraction composed of PBHs. The revised mass range that allows PBHs to assemble all cosmological dark matter is estimated to be 1015≲MBH/g≲1021. We demonstrate that, due to the constraints from γ-ray emission, quantum corrections due to the speculative memory burden effect do not modify this mass range. We also investigate the main characteristics of PBHs that are localized in the bulk. We show that PBHs localized in the bulk can make all cosmological dark matter if 1011≲MBH/g≲1021. Finally, we comment on the black holes that could be produced if one advocates a space with two boundaries for the dark dimension. Published by the American Physical Society 2024

Cosmic microwave background constraints on extended dark matter objects

Primordially formed extended dark objects would accrete baryonic matter and impact the ionisation history of the Universe. Insisting on consistency with the anisotropies of the cosmic microwave background, we derive constraints on the dark matter fraction for various classes of objects, of different sizes. We introduce a novel scaling technique to speed up numerical calculations and release our calculation framework in the form of a Mathematica notebook. Conservatively, we focus on spherical accretion and collisional ionisation. We find strong constraints limiting the dark matter fraction to subpercent level for objects of up to 104 AU in size.

Feedback in the dark: a critical examination of CMB bounds on primordial black holes

If present in the early universe, primordial black holes (PBHs) would have accreted matter and emitted high-energy photons, altering the statistical properties of the Cosmic Microwave Background (CMB). This mechanism has been used to constrain the fraction of dark matter that is in the form of PBHs to be much smaller than unity for PBH masses well above one solar mass. Moreover, the presence of dense dark matter mini-halos around the PBHs has been used to set even more stringent constraints, as these would boost the accretion rates.In this work, we critically revisit CMB constraints on PBHs taking into account the role of the local ionization of the gas around them. We discuss how the local increase in temperature around PBHs can prevent the dark matter mini-halos from strongly enhancing the accretion process, in some cases significantly weakening previously derived CMB constraints. We explore in detail the key ingredients of the CMB bound and derive a conservative limit on the cosmological abundance of massive PBHs.

Radial Oscillations of Strange Quark Stars Admixed with Dark Matter

We investigate the equilibrium structure and radial oscillations of strange quark stars admixed with fermionic dark matter. For strange quark matter, we employ a stiff equation of state from a color-superconductivity improved bag model. For dark matter, we adopt the cold free Fermi gas model. We rederive and numerically solve the radial oscillation equations of two-fluid stars based on general relativity, in which the dark matter and strange quark matter couple through gravity and oscillate with the same frequency. Our results show that the stellar maximum mass and radius are reduced by inclusion of dark matter. As to the fundamental mode of the radial oscillations, the frequency f0 is also reduced comparing to pure strange stars, and f02 reaches the zero point at the maximum stellar mass with dM/dϵq,c=0. Therefore, the stability criteria f02&gt;0 and dM/dϵq,c&gt;0 are consistent in our dark matter-mixed strange quark stars with a fixed fraction of dark matter. We also find a discontinuity of f0 as functions of the stellar mass, in contrast to the continuous function in pure strange stars. And it is also accompanied with discontinuity of the oscillation amplitudes as well as a discontinuous in-phase-to-out-phase transition between oscillations of dark matter and strange quark matter.

No massive black holes in the Milky Way halo.

The gravitational wave detectors have shown a population of massive black holes that do not resemble those observed in the Milky Way1-3 and whose origin is debated4-6. According to a possible explanation, these black holes may have formed from density fluctuations in the early Universe (primordial black holes)7-9, and they should comprise several to 100% of dark matter to explain the observed black hole merger rates10-12. If these black holes existed in the Milky Way dark matter halo, they would cause long-timescale gravitational microlensing events lasting years13. The previous experiments were not sufficiently sensitive to such events14-17. Here we present the results of the search for long-timescale microlensing events among the light curves of nearly 80 million stars located in the Large Magellanic Cloud that were monitored for 20 years by the Optical Gravitational Lensing Experiment survey18. We did not find any events with timescales longer than 1 year, whereas all shorter events detected may be explained by known stellar populations. We find that compact objects in the mass range from 1.8 × 10-4M⊙ to 6.3M⊙ cannot make up more than 1% of dark matter, and those in the mass range from 1.3 × 10-5M⊙ to 860 M⊙ cannot make up more than 10% of dark matter. Thus, primordial black holes in this mass range cannot simultaneously explain a substantial fraction of dark matter and gravitational wave events.

Probing ultralight primordial black hole dark matter with XMM telescopes

Primordial black holes (PBHs), originating from the gravitational collapse of large overdensities in the early Universe, emerge as a compelling dark matter (DM) candidate across a broad mass range. Of particular interest are ultra-light PBHs with masses around 1014 to 1017 g, which are typically probed by searching their evaporation products. Using the soft X-ray signal measured by the XMM telescopes, we derive constraints on the fraction of PBHs dark matter with masses in the range 1015-1016 g. We find that observations exclude fraction f>10−6 at 95% C.L. for mass MPBH=1015 g.