Matter Domination Research Articles

Constraints on primordial black holes for nonstandard cosmologies

We study how the bounds on the abundance of Primordial Black Holes (PBHs) and the constraints on power spectrum are modified if a non-standard evolution phase takes place between the end of inflation and the Standard radiation-dominated (RD) universe after inflation. The constraints on PBH abundance and power spectrum are computed using the new, freely available, https://github.com/TadeoDGAguilar/PBHBeta PBHBeta library, which accounts for the effects of non-standard expansion and specific criteria for PBH formation in such non-standard scenarios. As working examples, we consider three different cases: a pure matter-dominated (MD) phase, a scalar field-dominated (φD) universe, and a stiff fluid-dominated (SD) scenario.While the background expansion is the same for the MD and φD scenarios, the PBH formation criteria lead to different constraints to power spectrum. On the other hand, the duration of the non-standard expansion phase alters the bounds, with longer MD periods resulting in weaker constraints on power spectrum, and longer SD scenarios leading to an enhanced abundance due to the dust-like redshifting of PBHs. The modifications to the constraints are reported in all cases and we highlight those where the power spectrum may be significantly constrained.

Explaining PTA data with inflationary GWs in a PBH-dominated universe

We show that an ultralight primordial black hole (PBH) dominated phase makes blue-tilted inflationary gravitational waves (BGW) compatible with the recent detection of an nHz stochastic GW background by pulsar-timing arrays (PTAs), for high reheating temperatures. This PBH-dominated phase suppresses the BGW spectrum via entropy dilution, making it consistent with strong constraints from LIGO O3 and BBN. A future observation of such GW spectral features at mid or high frequencies can strongly constrain the possible mass range of PBHs. Since PBHs can exhibit various other unique signatures, they can be distinguished from spectra generated by other types of matter domination or exotic physics. Therefore, while important for studying GWs in the nHz range, the recent PTA result also sets the stage for testing and constraining various well-studied mechanisms following a PBH domination, using low-frequency measurements and correlated observations of unique high-frequency GW spectral features.

How many new particles do we need?

The Standard Model of particle physics (SM) and Einstein general relativity are extremely successful in describing almost all phenomena observed in Nature so far, spanning distances from a fraction of Fermi to thousands of megaparsec (Mpc). In this review article, the author deliberates on the question formulated in the title, given that the SM does not allow neutrino oscillations, does not have a candidate for dark matter in the Universe, and does not explain the observed cosmological dominance of matter over antimatter.

Quantification of the Few Parameters and Metallic Elements in the Quaternary Sediments of “Baie Du Repos” and their Interrelation

Mauritania is a fishing country. However, the Mauritanian coast is increasingly exposed to environmental issues mainly due to anthropogenic activities such as the mining, gas, oil, and fishing industries, as well as new agricultural practices that unreasonably use inputs. Environmental monitoring of the Mauritanian coast faces several challenges; thus, improving the fisheries sector begins with enhancing the state of marine ecosystems and implementing environmental monitoring adapted to climatic conditions and local needs. This study aims to evaluate the quality of the sediments of the “Baie du Repos” in the town of Nouadhibou, Mauritania, through the study of organic matter and the quantification of trace metallic elements in the Quaternary sediments of the Bay. Six samples deemed representative of this Bay were taken and transported to the laboratory. The physicochemical analysis of these samples shows that the superficial horizons of 30 cm depth have overall organic matter contents higher than the average threshold value proposed by the literature for 4 out of 6 of the points studied. The contents recorded for the different metallic trace elements indicate that point 1 is the most exposed to contamination, with the highest concentrations of cadmium, lead, copper, iron, and zinc. The ACP (Principal Component Analysis) showed that the metallic trace elements Pb, Cu, Fe, Cd, and Zn are closely related and evolve positively in the same direction. Additionally, it was found that the points studied are divided into three groups: Group 1 contains only point 1, which is the most exposed to contamination by these toxic elements (Pb, Cu, Zn, Fe, and Cd). Group 2 contains points 3, 5, and 6, which are moderately contaminated by metallic elements with a significant dominance of organic matter (OM). Finally, Group 3 is the least contaminated, with a very high content of organic matter (OM).

Dissipative dark cosmology: From early matter dominance to delayed compact objects

We demonstrate a novel mechanism for producing dark compact objects and black holes through a dark sector, where all the dark matter can be dissipative. Heavy dark sector particles with masses above 104 GeV can come to dominate the Universe and yield an early matter-dominated era before big bang nucleosynthesis (BBN). Density perturbations in this epoch can grow and collapse into tiny dark matter halos, which cool via self-interactions. The typical halo size is set by the Hubble length once perturbations begin growing, offering a straightforward prediction of the halo size and evolution depending on one’s choice of dark matter model. Once these primordial halos have formed, a thermal phase transition can then shift the Universe back into radiation domination and standard cosmology. These halos can continue to collapse after BBN, resulting in the late-time formation of fragmented dark compact objects and sub-solar-mass primordial black holes. We find that these compact objects can constitute a sizable fraction of all of dark matter. The resulting fragments can have masses between 1020 and 1032 g, with radii ranging from 10−2 to 105 m, while the black holes can have masses between 108 and 1034 g. Furthermore, a unique feature of this model is the late-time formation of black holes which can evaporate today. We compare where these objects lie with respect to current primordial black hole and massive (astrophysical) compact halo object constraints. Published by the American Physical Society 2024

Dark matter from phase transition generated PBH evaporation with gravitational waves signatures

We study the possibility of generating dark matter (DM) purely from ultralight primordial black hole (PBH) evaporation with the latter being produced from a first order phase transition (FOPT) in the early Universe. If such ultralight PBH leads to an early matter domination, it can give rise to a doubly peaked gravitational wave (GW) spectrum in Hz-kHz ballpark with the low frequency peak generated from PBH density fluctuations being within near future experimental sensitivity. In the subdominant PBH regime, the FOPT generated GW spectrum comes within sensitivity due to absence of entropy dilution. In both the regimes, PBH mass from a few kg can be probed by GW experiments like BBO, ET, CE, UDECIGO etc. while DM mass gets restricted to the superheavy ballpark in the PBH dominance case. Apart from distinct DM mass ranges in the two scenarios, GW observations can differentiate by measuring their distinct spectral shapes. Published by the American Physical Society 2024

Probing SUSY at gravitational wave observatories

Under the assumption that the recent pulsar timing array evidence for a stochastic gravitational wave (GW) background at nanohertz frequencies is generated by metastable cosmic strings, we analyze the potential of present and future GW observatories for probing the change of particle degrees of freedom caused, e.g., by a supersymmetric (SUSY) extension of the Standard Model (SM). We find that signs of the characteristic doubling of degrees of freedom predicted by SUSY could be detected at Einstein Telescope and Cosmic Explorer even if the masses of the SUSY partner particles are as high as about 104 TeV, far above the reach of any currently envisioned particle collider. We also discuss the detection prospects for the case that some entropy production, e.g. from a late decaying modulus field inducing a temporary matter domination phase in the evolution of the universe, somewhat dilutes the GW spectrum, delaying discovery of the stochastic GW background at LIGO-Virgo-KAGRA. In our analysis we focus on SUSY, but any theory beyond the SM predicting a significant increase of particle degrees of freedom could be probed this way.

Dark matter from mediator decay in early matter domination

We study dark matter production from mediator decays in scenarios with an epoch of early matter domination. Particles that mediate interactions between dark matter and the standard model particles are kinematically accessible to the thermal bath as long as their mass is below the reheating temperature of the Universe after inflation. Decay of on-shell mediators can then lead to copious production of dark matter during early matter domination or a preceding radiation-dominated phase. In particular, for mediators that are charged under the standard model, it can exceed the standard freeze-in channel due to inverse annihilations at much lower temperatures (often by many orders of magnitude). The requirement to obtain the correct relic abundance severely constrains the parameter space for dark matter masses above a few TeV. Published by the American Physical Society 2024

Observational constraints on the emergent universe with non-linear equation of state and interacting fluids

We investigate a flat emergent universe (EU) with a nonlinear equation of state equivalent to three different composition of fluids. In the EU initially, the evolution of the universe began with no interaction but as time evolves an interaction sets in among the three fluids leading to the observed universe. The characteristic of an EU is that it is a singularity free universe that evolves with all the basic features of the early evolution. For a given nonlinear equation of state parameter, it permits a universe with three different fluids, we get a universe with dark energy, cosmic string, and radiation domination to begin with which at a later epoch transits into a universe with three different fluids with matter domination (baryonic as well as dark matter) and dark energy for a given interaction strength among the cosmic fluids. The evolution of the universe is probed with exponential interactions to obtain a universe with late acceleration. The model parameters are constrained using the observed Hubble data and Type Ia Supernova (SnIa) data from the Pantheon data set. An interacting EU transforms to a matter dominated phase with DE accommodating the present universe satisfactorily. The stability of the cosmological model is also discussed.

A record of change in oyster environment through high-resolution geochemical analysis of Late-Holocene sediments from Coastal Ghana

The near-coast environments where oysters occur are among the most impacted by humans globally, especially during the Late-Holocene. Yet, in West Africa, there is no documented historical record of change in these environments. We provide insight into the changing geochemical conditions of two oyster environments through high-resolution analysis of total organic carbon (C), total nitrogen (N), carbon and nitrogen isotope ratios (δ13C, δ15N), and trace elements, in two cores retrieved from the Densu estuary and the Anyanui (Keta) Creek in Ghana. Drastic shifts in sedimentation rate occurred in the Keta and Densu cores around 1996 CE and 960 CE respectively. At these times, comparatively, low levels of C and N were found in the Densu core. Increasing C and N levels and decreasing δ13C upcore aligned with the observed shift in sedimentation rate in the Keta core. The C/N ratios in the Keta core suggest allochthonous organic matter (OM) dominance in the creek. The Densu core showed periodic changes in C/N ratios from very high values (>20) between 1918 BCE and 1321 BCE, to values between 20 and 11 between 1321 BCE and 1977 CE and below 10 from the late 1970s CE to the present day, suggesting a varying degree of transformation in the catchment basin. Extremely high Sulfur (S) and moderate to significant Iron (Fe) increases suggest reducing conditions in the Keta sediments. Moderate Calcium (Ca), Zinc (Zn), and Strontium (Sr) concentrations in the upper part of the Densu core suggest a stronger influence of marine processes in the Densu in recent times. The findings reflect the impacts of catchment basin modification on the health of the two coastal environments, likely to impact the growth, productivity, and sustainability of the fishery of the West African mangrove Oyster.

Signature of nonminimal scalar-gravity coupling with an early matter domination on the power spectrum of gravitational waves

The signal strength of primordial gravitational waves experiencing an epoch of early scalar domination, due to an oscillating scalar field, is reduced with respect to radiation domination. In this paper, we demonstrate that the specific pattern of this reduction is sensitive to the coupling between the dominant field and gravity. When this coupling is zero, the impact of early-matter domination on gravitational waves is solely attributed to the alteration of the Hubble parameter and the scale factor. In the presence of nonzero couplings, on the other hand, the evolution of primordial gravitational waves is directly affected as well, resulting in a distinct steplike feature in the power spectrum of the gravitational wave as a function of frequency. This feature serves as a smoking gun signature of this model. Although the aforementioned results are obtained numerically, we also provide an analytical expression of the power spectrum to illustrate its dependence on the model parameters and initial conditions. Furthermore, we provide analytical relations that specify the frequency interval in which the step occurs. We compare the analytical estimates with numerical analysis and show they match well. Published by the American Physical Society 2024

Gravitational wave signals from early matter domination: interpolating between fast and slow transitions

An epoch of matter domination in the early universe can enhance the primordial stochastic gravitational wave signal, potentially making it detectable to upcoming gravitational wave experiments. However, the resulting gravitational wave signal is quite sensitive to the end of the early matter-dominated epoch. If matter domination ends gradually, a cancellation results in an extremely suppressed signal, while in the limit of an instantaneous transition, there is a resonant-like enhancement. The end of the matter dominated epoch cannot be instantaneous, however, and previous analyses have used a Gaussian smoothing technique to account for this, and consider only a limited regime around the fast transition limit. In this work, we present a study of the enhanced gravitational wave signal from early matter domination without making either approximation and show how the signal smoothly evolves from the strongly suppressed to strongly enhanced regimes.

Deciphering the intricate link between watershed-level land use changes and reservoir eutrophication in central Argentina over the 20th-21st century

In Anthropocene, unbalances of the water cycle have created a severe threat to the supply of this crucial element for current and future generations. In addition, water quality degradation has been promoted by the land-use change from natural ecosystems to urbanized and industrialized areas, favoring the nutrient input into water bodies. In the last two decades, the San Roque reservoir (SRr), situated in central Argentina, has become hypereutrophic. In this work, we proposed an integrated study strategy that included a multiproxy examination of the reservoir sedimentary record and a study of land-use changes, in order to: 1) link land-use change to primary productivity of the SRr over the last 100 years; and 2) identify the processes involved in the SRr's environmental evolution prior and after urban expansion occurred by 1980 CE. Results allow to recognize two distinctive scenarios: a) Pre-urban scenario (1898–1983 CE) reflected by a dominance of allochthonous organic matter in the sedimentary record derived from the catchment's deforestation and, b) A transition towards increasing lake internal productivity (1984–2018 CE), resulting in a eutrophic state with cyanobacteria dominance due to catchment urban densification, particularly in the peri-lacustrine area. This work constitutes a novel tool by combining a paleolimnological approach with demographic analysis to accurately track the consequences of land use change on the water body and, in addition, provide the basis for modeling future scenarios.

Hunting WIMPs with LISA: correlating dark matter and gravitational wave signals

The thermal freeze-out mechanism in its classical form is tightly connected to physics beyond the Standard Model around the electroweak scale, which has been the target of enormous experimental efforts. In this work we study a dark matter model in which freeze-out is triggered by a strong first-order phase transition in a dark sector, and show that this phase transition must also happen close to the electroweak scale, i.e. in the temperature range relevant for gravitational wave searches with the LISA mission. Specifically, we consider the spontaneous breaking of a U(1)′ gauge symmetry through the vacuum expectation value of a scalar field, which generates the mass of a fermionic dark matter candidate that subsequently annihilates into dark Higgs and gauge bosons. In this set-up the peak frequency of the gravitational wave background is tightly correlated with the dark matter relic abundance, and imposing the observed value for the latter implies that the former must lie in the milli-Hertz range. A peculiar feature of our set-up is that the dark sector is not necessarily in thermal equilibrium with the Standard Model during the phase transition, and hence the temperatures of the two sectors evolve independently. Nevertheless, the requirement that the universe does not enter an extended period of matter domination after the phase transition, which would strongly dilute any gravitational wave signal, places a lower bound on the portal coupling that governs the entropy transfer between the two sectors. As a result, the predictions for the peak frequency of gravitational waves in the LISA band are robust, while the amplitude can change depending on the initial dark sector temperature.

Cosmic acceleration & deceleration with f(R,T) gravity

This study includes the cosmic evolution and the potential periodicity of the universe. It employs a periodic varying deceleration parameter (PVDP) within the framework of [Formula: see text] theory of gravity, with a specific focus on the Bianchi-II model. We explore the dynamic nature of the universe, with physical and geometrical properties within this theoretical framework. We have also analyzed the cosmographic parameters, including jerk, snap, and lerk, for deeper insights into the universe’s evolution and behavior. Utilizing state finder diagrams and the Om diagnostic (which illustrates the variation of [Formula: see text] with redshift) signifying a shift from matter dominance to a stronger influence of dark energy (DE), we construct a comprehensive map of the universe’s trajectory and behavior. By employing the Bianchi-II model within the [Formula: see text] theory, our proposed model helps us in understanding the universe’s oscillatory patterns and underlying mechanisms. This research significantly contributes to our understanding of cosmic evolution and periodicity within the [Formula: see text] theory.

Dynamics of inspiraling dark energy

We investigate the dynamics of a multifield dark energy model, which arises from certain rapid-turning and inspiraling trajectories in field space. We find the speed of sound cs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c_s$$\\end{document} of the dark energy perturbations around the background and show that cs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c_s$$\\end{document} is monotonically decreasing with time. Furthermore, it has a positive-definite lower bound that implies a certain clustering scale. We also extend the previously known background solution for dark energy to an exact solution that includes matter. This allows us to address the implications of our model for two cosmological tensions. More precisely, we argue that the σ8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma _8$$\\end{document} tension can be alleviated generically, while reducing the Hubble tension requires certain constraints on the parameter space of the model. Notably, a necessary condition for alleviating the Hubble tension is that the transition from matter domination to the dark energy epoch begins earlier than in Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM.

Simulations of gravitational heating due to early matter domination

In cosmologies with an early matter-dominated era (EMDE) prior to Big Bang nucleosynthesis, the boosted growth of small-scale matter perturbations during the EMDE leads to microhalo formation long before halos would otherwise begin to form. For a range of models, halos can even form during the EMDE itself. These halos would dissipate at the end of the EMDE, releasing their gravitationally heated dark matter and thereby imprintinga free-streaming cut-off on the matter power spectrum.We conduct the first cosmological N-body simulations of the formation and evaporation of halos during and after an EMDE.We show that in these scenarios, the free-streaming cut-off after the EMDE can be predicted accurately from the linear matter power spectrum. Although the free streaming can erase much of the EMDE-driven boost to density perturbations, we use our findings to show that the (re-)formation of halos after the EMDE nevertheless proceeds before redshift ∼ 1000. Early-forming microhalos are a key observational signature of an EMDE, and our prescription for the impact of gravitational heating will allow studies of the observational status and prospects of EMDE scenarios to cover a much wider range of parameters.

Probing baryogenesis in f(Q) gravity

The origin of matter domination in the Universe is one of the most exciting open puzzles in particle physics and cosmology. Despite many theoretical developments, the actual reason behind baryon-antibaryon asymmetry is still unknown. Our aim here is to examine this phenomenon in the framework of modified gravity theories, which have impressively elucidated the contemporary accelerated expansion of the Universe as well as the early phase. Consequently, this letter sets its sights on the task of constraining a specific variant of modified gravity, namely, f(Q) gravity, in conjunction with gravitational baryogenesis. The power law model and recently proposed DGP-like f(Q) models are considered to find the baryon-to-entropy ratio and compare them with the observed value, that is . Furthermore, we impose constraints on the additional degrees of freedom introduced by this modified theory of gravity.

Anatomy of diluted dark matter in the minimal left-right symmetric model

Temporary matter domination and late entropy dilution, injected by a “long-lived” particle in the early Universe, serves as a standard mechanism for yielding the correct dark matter relic density. We recently pointed out the cosmological significance of diluting particle’s partial decay into dark matter. When repopulated in such a way, dark matter carries higher momentum than its thermal counterpart, resulting in a suppression of the linear matter power spectrum that is constrained by the large scale structure observations. In this work, we study the impact of such constraints on the minimal left-right symmetric model that accounts for the origin of neutrino mass. We map out a systematic anatomy of possible dilution scenarios with viable parameter spaces, allowed by cosmology and various astrophysical and terrestrial constraints. We show that to accommodate the observed dark matter relic abundance the spontaneous left-right symmetry breaking scale must be above PeV and cosmology will continue to provide the most sensitive probes of it. In case the dilutor is one of the heavier right-handed neutrinos, it can be much lighter and lie near the electroweak scale. Published by the American Physical Society 2024

MaNGA DynPop – VI. Matter density slopes from dynamical models of 6000 galaxies versus cosmological simulations: the interplay between baryonic and dark matter

ABSTRACT We try to understand the trends in the mass density slopes as a function of galaxy properties. We use the results from the best Jeans Anisotropic Modelling (JAM) of the integral-field stellar kinematics for near 6000 galaxies from the MaNGA DynPop project, with stellar masses $10^9\ {\rm {\rm M}_{\odot }}\lesssim M_*\lesssim 10^{12}\ {\rm {\rm M}_{\odot }}$, including both early-type and late-type galaxies. We use the mass-weighted density slopes for the stellar $\overline{\gamma }_*$, dark $\overline{\gamma }_{_{\rm DM}}$ and total $\overline{\gamma }_{_{\rm T}}$ mass from the MaNGA DynPop project. As previously reported, $\overline{\gamma }_{_{\rm T}}$ approaches a constant value of $\overline{\gamma }_{_{\rm T}}\approx 2.2$ for high σe galaxies, and flattens for $\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\lesssim 2.3$ galaxies, reaching $\overline{\gamma }_{_{\rm T}}\approx 1.5$ for $\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\approx 1.8$. We find that total and stellar slopes track each other tightly, with $\overline{\gamma }_{_{\rm T}}\approx \overline{\gamma }_*-0.174$ over the full σe range. This confirms the dominance of stellar matter within Re. We also show that there is no perfect conspiracy between baryonic and dark matter, as $\overline{\gamma }_*$ and $\overline{\gamma }_{_{\rm DM}}$ do not vary inversely within the σe range. We find that the central galaxies from TNG50 and TNG100 simulations do not reproduce the observed galaxy mass distribution, which we attribute to the overestimated dark matter fraction, possibly due to a constant IMF and excessive adiabatic contraction effects in the simulations. Finally, we present the stacked dark matter density profiles and show that they are slightly steeper than the pure dark matter simulation prediction of $\overline{\gamma }_{_{\rm DM}}\approx 1$, suggesting moderate adiabatic contraction in the central region of galaxies. Our work demonstrates the power of stellar dynamics modelling for probing the interaction between stellar and dark matter and testing galaxy formation theories.