Cosmic Coincidence Research Articles

The probability of cosmic coincidence

The wave function of the quantum cosmological model of gravity coupled to a scalar field has been found at very early times. Corrections resulting from quadratic curvature terms may be evaluated and the functional dependence is found to have a similar form consistent with the inflationary epoch. The fundamental string theories would determine the gravitational action, and effective actions for both [Formula: see text] and [Formula: see text] string theories are examined, establishing a connection with topological string models. The nonlinear differential equation for the free energy of the 10-dimensional theory describing the compactification over a Calabi–Yau space of three complex dimensions is formulated, and it is transformed into a linear differential equation for the product of a function of the scaled string coupling and the partition function. A solution given by a sum over the genus is found for the series expansion of the partition function that can be matched in a bounded range for the coupling, and the scale factor, with the quantum cosmological wave function of the quadratic gravity model viable during the inflationary epoch.

A closer look in the mirror: reflections on the matter/dark matter coincidence

We argue that the striking similarity between the cosmic abundances of baryons and dark matter, despite their very different astrophysical behavior, strongly motivates the scenario in which dark matter resides within a rich dark sector parallel in structure to that of the standard model. The near cosmic coincidence is then explained by an approximate ℤ2 exchange symmetry between the two sectors, where dark matter consists of stable dark neutrons, with matter and dark matter asymmetries arising via parallel WIMP baryogenesis mechanisms. Taking a top-down perspective, we point out that an adequate ℤ2 symmetry necessitates solving the electroweak hierarchy problem in each sector, without our committing to a specific implementation. A higher-dimensional realization in the far UV is presented, in which the hierarchical couplings of the two sectors and the requisite ℤ2-breaking structure arise naturally from extra-dimensional localization and gauge symmetries. We trace the cosmic history, paying attention to potential pitfalls not fully considered in previous literature. Residual ℤ2-breaking can very plausibly give rise to the asymmetric reheating of the two sectors, needed to keep the cosmological abundance of relativistic dark particles below tight bounds. We show that, despite the need to keep inter-sector couplings highly suppressed after asymmetric reheating, there can naturally be order-one couplings mediated by TeV scale particles which can allow experimental probes of the dark sector at high energy colliders. Massive mediators can also induce dark matter direct detection signals, but likely at or below the neutrino floor.

Oscillating Dark Energy in Light of the Latest Observations and Its Impact on the Hubble Tension

In this paper, we have performed a comparative study of different types of oscillating dark energy (DE) models using the Metropolis algorithm of Markov Chain Monte Carlo. Eight different oscillating parameterizations are examined herein that have demonstrated considerable ability to fit the overall cosmological observations, including the Pantheon sample of Type Ia supernovae, baryon acoustic oscillations, cosmic chronometer Hubble data, and distance priors of the Planck cosmic microwave background. In order to compare the consistency of these models with observations, we have used both the Akaike and deviance information criteria. Although the values of the Akaike information criterion for different models indicate that there is no support for oscillating DE models, the deviance information criterion showed that there is significant support for some of these models. Our results showed that these models are capable of solving the cosmic coincidence problem and alleviating the Hubble tension. Comparing the H 0 values obtained for different oscillating scenarios with that of ΛCDM, we observed that our oscillating models led to H0¯=69.78 , which is 0.29 greater than H 0,Λ and thus reduces the Hubble tension. Among all of the models, model 1, with H 0 = 70.00 ± 0.71, is the most capable of alleviating the H 0 tension. Furthermore, we examined our models assuming H 0 = 73.0 ± 1.4 from SHoES measurements. We find that adding this data point to our data combination led to a ΔH0¯=0.95 increase in the H 0 value for different models.

Integrated study of dark matter and dark energy models

Dark matter and dark energy are used as two important concepts in cosmology to explain some of the observed phenomena in the universe. Dark matter is one of the most dominant constituents of the Universe, and it influences the structural formation of the Universe through gravity, including the formation and evolution of galaxies, clusters, and the large-scale structure of the Universe. Dark energy is believed to be one of the causes of the accelerated expansion of the Universe, and its presence explains the observed phenomenon of the accelerating rate of expansion of the Universe. Although their existence has not been directly observed, people understand through the study of the structure and evolution of the universe that they play an important role in the universe. This paper first introduces the background knowledge of dark matter and its related properties and explains the reasons why three types of models, namely WIMP, axion, and sterile neutrino, are candidates for dark matter in the light of existing observations. The paper then discusses the relevant properties of dark energy and analyses the mainstream dark energy models. For the cosmological constant mode, the fine-tuning problem and cosmic coincidence problem it faces are analysed in detail. The evolution of the dark energy equation of state from the past >-1 to the present <-1 is then explained, and this is used to introduce the scalar field model involving dynamic, the Chaplygin gas model, the holographic dark energy model, and the interacting dark energy model.

Dynamics of viable f(R) dark energy models in the presence of curvature–matter interactions

In this study, we analyze the dynamics of the interaction between dark matter and curvature-driven dark energy in viable f(R) gravity models using the framework of dynamical system analysis. We incorporate this interaction by introducing a source term in their respective continuity equations, given by Q=κ2α3Hρ~mρcurv\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q = \\frac{\\kappa ^2 \\alpha }{3\\,H}\ ilde{\\rho }_\ extrm{m}\\rho _\ extrm{curv}$$\\end{document}, and examine two f(R) gravity models that comply with local gravity constraints and cosmological viability criteria. Our findings reveal subtle modifications to fixed points and their stability criteria when compared to the conventional dynamical analysis of f(R) gravity models without matter-curvature interactions as proposed and examined in prior literature. We determine the parameter limits associated with the stability criteria of critical points of the dynamical system for both the models. Additionally, the introduction of interaction reveals variations in the dynamical aspects of cosmic evolution, contingent on the range of values for the relevant model parameters. These results are consistent with the observed features of cosmic evolution within specific limits of the f(R) models parameters and the coupling parameter α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. We also examine the evolutionary dynamics of the universe in the interacting scenario through cosmological and cosmographic parameters. Our analysis demonstrates that the interacting scenario comprehensively accounts for all the observed phases of the universe’s evolution and also results in a stable late-time cosmic acceleration. Additionally, we’ve studied how the coupling parameter affects evolutionary dynamics, particularly its impact on the matter-to-curvature energy density ratio. Our findings suggest that the chosen form of interaction can also address the cosmic coincidence problem.

A mass scale law connecting cosmophysics to microphysics

We introduce different mass scales corresponding to the Universe, fermion stars, mini boson stars, Planck black holes, the electron, the neutrino, and the cosmon. These mass scales are obtained by combining the maximum mass of fermion stars, boson stars and soliton stars set by quantum mechanics and general relativity with the Eddington relation connecting the mass me of the electron to the cosmological constant Λ. In this manner, we can express the mass of these objects in terms of the fundamental constants of physics G, c, ħ and Λ. By normalizing the mass Ma of these objects by the Planck mass MP, we find that Ma/MP∼χa/6, where χ∼ρP/ρΛ∼10120 is the “largest large number” in Nature (the ratio of the Planck density on the Einstein cosmological density) and a=3,2,1,0,−1,−2,−3 for the Universe, fermion stars, mini boson stars, Planck black holes, the electron, the neutrino, and the cosmon respectively. This formula suggests an interesting symmetrical mass scale law connecting cosmophysics (Universe, fermion stars, mini boson stars) to microphysics (electron, neutrino, cosmon). A generalization of this law including the earth mass and another neutrino mass scale is proposed. We highlight an accurate form of Eddington relation me≃α(Λħ4/G2)1/6 or Λ≃G2me6/α6ħ4=α−6(me/MP)6lP−2, where α=e2/ħc≃1/137 is the fine structure constant, and provide different heuristic derivations of this relation. We consider another relation Λ=Gc(mΛ∗)4/ħ3=(mΛ∗/MP)4lP−2, where mΛ∗=(Λħ3/Gc)1/4 is the neutrino mass. We relate these relations to the two expressions of the vacuum energy density given by Zeldovich in 1968. We suggest that the dark energy particle (cosmon) of mass mΛ=ħΛ/c could be a quantum of mass and entropy so that Λ=mΛ2c2/ħ2=(mΛ/MP)2lP−2. We relate the large number 10120 to the total number of degrees of freedom (or number of cosmons) in the universe. Finally, we give hints how to possibly solve the cosmological constant problem, the cosmic coincidence problem, and the large number coincidence problem.

Little Ado about Everything: ηCDM, a Cosmological Model with Fluctuation-driven Acceleration at Late Times

We propose a model of the Universe (dubbed ηCDM) featuring a controlled stochastic evolution of the cosmological quantities that is meant to render the effects of small deviations from homogeneity/isotropy on scales of 30–50 h −1 Mpc at late cosmic times associated with the emergence of the cosmic web. Specifically, we prescribe that the behavior of the matter/radiation energy densities in different patches of the Universe with such a size can be effectively described by a stochastic version of the mass–energy evolution equation. The latter includes, besides the usual dilution due to cosmic expansion, an appropriate noise term that statistically accounts for local fluctuations due to inhomogeneities, anisotropic stresses, and matter flows induced by complex gravitational processes. The evolution of the different patches as a function of cosmic time is rendered via the diverse realizations of the noise term; meanwhile, at any given cosmic time, sampling the ensemble of patches will create a nontrivial spatial distribution of the various cosmological quantities. Finally, the overall behavior of the Universe will be obtained by averaging over the patch ensemble. We assume a simple and physically reasonable parameterization of the noise term, gauging it against a wealth of cosmological data sets in the local and high-redshift Universe. We find that, with respect to standard ΛCDM, the ensemble-averaged cosmic dynamics in the ηCDM model is substantially altered by the stochasticity in three main respects: (i) an accelerated expansion is enforced at late cosmic times without the need for any additional exotic component (e.g., dark energy), (ii) the spatial curvature can stay small even in a low-density Universe constituted solely by matter and radiation, (iii) matter can acquire an effective negative pressure at late times. The ηCDM model is Hubble tension–free, meaning that the estimates of the Hubble constant from early- and late-time measurements do not show marked disagreement as in ΛCDM. We also provide specific predictions for the variance of the cosmological quantities among the different patches of the Universe at late cosmic times. Finally, the fate of the Universe in the ηCDM model is investigated to show that the cosmic coincidence problem is relieved without invoking the anthropic principle.

Elucidation of ‘Cosmic Coincidence’

In the standard cosmological model the dark energy (DE) and nonrelativistic (NR) matter densities are observationally determined to be comparable at the present time, in spite of their greatly different evolution histories. This ‘cosmic coincidence’ enigma – also referred to as the ‘why now? problem’ – relies, by its very definition, on the implicit prior expectation for our ‘typicality’ in the cosmic (expanding) spacetime volume. Otherwise, this conundrum does not exist in the first place. It is shown here that this apparent coincidence could be explained as a non-anthropic observational selection effect: for us to be typical observers in the comoving (static) spacetime volume, the cosmic energy budget must contain a non-vanishing DE component. In addition, it is shown that irrespective of the cosmological initial conditions and assuming no ‘new physics’, the Universe is most likely to be observed at a time when the conformal Hubble radius, H−1, attains a maximum. The latter takes place at the epoch when ρDE and ρm, the energy densities of DE and NR matter, respectively, are comparable. Specifically, our presumed ‘typicality’ along the conformal timeline, coupled to a few other plausible assumptions, implies that R≡ρDE/ρm is ‘sampled’ from a Beta Prime probability distribution function. A priori 68% (95%) confidence range for the ratio is 0.20<R<3.46 (0.033<R<17.20), with an expectation value of R̄=3.5. These are in agreement with the observationally inferred value, Robs=2.23.

A quantum cosmology approach to cosmic coincidence and inflation

This work studies the quantum cosmology of a closed, spatially homogeneous, and isotropic FLRW minisuperspace model with electromagnetic radiation as a matter content. We solve the associated Wheeler-DeWitt (WDW) equation using the holographic regularization method and show that the electromagnetic zero-point energy forms the vacuum energy and provides a unified resolution to the horizon, flatness, singularity, and cosmic coincidence problems. This quantum cosmology approach composes an alternative to the usual inflationary paradigm and can be extended to more general matter contents and emergent gravity schemes.

Twin cogenesis

We investigate a cogenesis mechanism within the twin Higgs setup that can naturally explain the nature of dark matter, the cosmic coincidence puzzle, little hierarchy problem, leptogenesis, and the tiny neutrino masses. Three heavy Majorana neutrinos are introduced to the standard model sector and the twin sector respectively, which explain the tiny neutrino masses and generate the lepton asymmetry and the twin lepton asymmetry at the same time. The twin cogenesis mechanism applies to any viable twin Higgs model without an explicit breaking in the leptonic sector and evading the ΔN eff constraint. We illustrate the twin cogenesis mechanism using the neutrino-philic twin two Higgs doublet model, a newly proposed model to lift the twin neutrino masses with spontaneous breaking. The dark photon with a Stueckelberg mass MeV ensures the energy in the twin sector as well as the symmetric component of twin sector particles can be depleted. The lightest twin baryons are the dark matter candidates with masses of approximately 5.5 GeV, which explains naturally the amount of dark matter and visible matter in the Universe are of the same order. We also demonstrate twin cogenesis in the fraternal twin Higgs setup, in which the dark matter candidate is the twin bottom bound state .

Cosmic coincidence problem in interacting holographic dark energy models

It is well known fact that almost the cosmological models for dark energy are suppressed by the coincidence problem. It is worth while studying holographic dark energy model which requires considering the interaction between dark energy and dark matter. In this paper we propose a method for determining parameters of the models so as for the transition redshift zt and the present deceleration parameter q0 to agree with the previous study by means of numerical simulation. By considering the variation of coincidence parameter with the redshift based on the proposed models, we demonstrate that α-model is the most appropriate to explain coincidence problem. Also, this work shows that the direction of flow must be from dark energy to dark matter.

Forecast analysis on interacting dark energy models from future generation PICO and DESI missions

ABSTRACT The next-generation cosmic microwave background (CMB) satellite missions are expected to provide robust constraints on a wide range of cosmological parameters with unprecedented precision. But these constraints on the parameters could weaken if we do not attribute dark energy to a cosmological constant. The cosmological models involving interaction between dark energy and dark matter can give rise to comparable energy densities at the present epoch, thereby alleviating the so-called cosmic coincidence problem. In the present paper, we perform a forecast analysis to test the ability of the future generation high-sensitive CMB, and baryon acoustic oscillation (BAO) experiments to constrain phenomenological interacting dark energy models. We consider cosmic variance limited future CMB experiment Probe of Inflation and Cosmic Origins (PICO) along with BAO information from the Dark Energy Spectroscopic Instrument (DESI), to constrain the parameters of the interacting dark sector. Based on the stability of the cosmological perturbations, we consider two possibilities for the interaction scenario. We investigate the impact of both coupling constant and equation of state parameter of dark energy on CMB temperature power spectrum, matter power spectrum, and fσ8. We have used simulated temperature and polarization data from PICO within the multipole ranges (ℓ = 2–4000), and as expected, we do see PICO alone produces better constraints than Planck on the ΛCDM parameters. With the integration of PICO and DESI missions, we observe a significant improvement in the constraints on several cosmological parameters, especially the equation of state parameter of dark energy. However, we note that additional data are required to constrain a small positive coupling constant.

The effective theory of gravity and dynamical vacuum energy

Gravity and general relativity are considered as an Effective Field Theory (EFT) at low energies and macroscopic distances. The effective action of the conformal anomaly of light or massless quantum fields has significant effects on macroscopic scales, due to associated light cone singularities that are not captured by an expansion in local curvature invariants. A compact local form for the Wess-Zumino effective action of the conformal anomaly and stress tensor is given, requiring the introduction of a new light scalar field, which it is argued should be included in the low energy effective action for gravity. This scalar conformalon couples to the conformal part of the spacetime metric and allows the effective value of the vacuum energy, described as a condensate of an exact 4-form abelian gauge field strength F = dA, to change in space and time. This is achieved by the identification of the torsion dependent part of the Chern-Simons 3-form of the Euler class with the gauge potential A, which enters the effective action of the conformal anomaly as a J · A interaction analogous to electromagnetism. The conserved 3-current J describes the worldtube of 2-surfaces that separate regions of differing vacuum energy. The resulting EFT thus replaces the fixed constant Λ of classical gravity, and its apparently unnaturally large sensitivity to UV physics, with a dynamical condensate whose ground state value in empty flat space is Λeff = 0 identically. By allowing Λeff to vary rapidly near the 2-surface of a black hole horizon, the proposed EFT of dynamical vacuum energy provides an effective Lagrangian framework for gravitational condensate stars, as the final state of complete gravitational collapse consistent with quantum theory. The possible consequences of dynamical vacuum dark energy for cosmology, the cosmic coincidence problem, and the role of conformal invariance for other fine tuning issues in the Standard Model are discussed.

Predictions from the logotropic model: The universal surface density of dark matter halos and the present proportions of dark matter and dark energy

The logotropic model (Chavanis, 2015) may be an interesting alternative to the ΛCDM model. It is able to account for the present accelerating expansion of the universe while solving at the same time the core–cusp problem of the CDM model. In the logotropic model, there is a single dark fluid. Its rest-mass plays the role of dark matter and its internal energy plays the role of dark energy. We highlight two remarkable predictions of the logotropic model. It yields cored dark matter halos with a universal surface density equal to Σ0th=0.01955cΛ/G=133M⊙/pc2, without free parameter, in very good agreement with the observational value Σ0obs=141−52+83M⊙/pc2. It also predicts the present ratio of dark energy and dark matter to be the Euler number Ωde,0th/Ωdm,0th=e=2.71828... in very good agreement with the observations giving Ωde,0obs/Ωdm,0obs=2.669±0.08. Using the measured present proportion of baryonic matter Ωb,0obs=0.0486±0.0010, we find that the values of the present proportions of dark matter and dark energy are Ωdm,0th=11+e(1−Ωb,0)=0.2559 and Ωde,0th=e1+e(1−Ωb,0)=0.6955 in very good agreement with the observational values Ωdm,0obs=0.2589±0.0057 and Ωde,0obs=0.6911±0.0062 within the error bars. These theoretical predictions are obtained by advocating a mysterious strong cosmic coincidence (dubbed “dark magic”) implying that our epoch plays a particular role in the history of the universe. We review the three types of logotropic models introduced in our previous papers depending on whether the equation of state is expressed in terms of the energy density, the rest-mass density, or the pseudo-rest mass density of a complex scalar field. We discuss the similarities and the differences between these models. Finally, we point out some intrinsic difficulties with the logotropic model similar to those encountered by the Chaplygin gas model and discuss possible solutions.

ROBUST ETHICAL REALISM AND THE MORAL COINCIDENCE PROBLEM

I present an objection to robust ethical realism, the view that there are mind-independent moral facts with normative import. I argue that if we combine robust ethical realism with a traditional conception of morality, according to which persons are especially relevant from a moral point of view, the result is that there is a remarkable coincidence between the content of normative facts and the kind of beings that actually exist. On the one hand, the normative facts single out persons as anespecially relevant kind of being and, on the other hand, persons happen to exist. This match amounts to a coincidence because, according to robust ethical realism, normative facts cannot explain why there are persons and the fact that there are persons cannot explain why the normative facts are what they are. To the extent that commitment to unexplained coincidences counts against a view, robust ethical realism faces a problem. Although there are important similarities between this objection and other objections to normative realism that appeal to remarkable coincidences (such as Street’s evolutionary debunking argument and Bedke’s cosmic coincidence argument), I argue that the moral coincidence poses a different problem for robust ethical realism.

Stranger H: no se recuerda la soledad

I sustained a two-hour conversation with a stranger I met in the library. In this time, we cried twice over the death of his parents and my father. We also agreed to create a present for his daughter which kept us in communication for over a year. The synchronic interconnections and parallels of time and space that emerged between this stranger's life and mine forced me into a dialogue with people, dates, places, objects, and revelations that crystallize in this text. The events that initially felt like parts of individual fates of individual family histories are here rediscovered as entanglements of unexpected invisible bonds and strands of cosmic coincidence.&nbsp; In&nbsp;Stranger H: We Do Not Remember Alone,&nbsp;I recapitulate this process and grieve my loss by gathering mourning rituals, contagious recalling, audiovisual metaphysics, pseudoscientific relational diagrams, and spiritual strangerhood.&nbsp; &nbsp; The performative nature of the text continued to grow. I shared this text with a friend and she spontaneously added the memories of her own loss as they emerged while going through it. As I read her notes, I realized that things that we probably wouldn’t have been able to tell each other verbally were shared in a profound reading-conversation. The editable version of the text is now available on request to anyone who has&nbsp;lost a parent&nbsp;and would like to&nbsp;join&nbsp;this conversation. This text has become an in-dialogue reading that acknowledges loss from an aesthetic, philosophical,&nbsp;speculative, and imaginative lense. But most importantly, it is a way to be accompanied in the lonesome process of facing loss. Although the pain of each person is non-transferable and must be overcome individually, the&nbsp;Stranger H: We Do Not Remember Alone&nbsp;holds space and time to reflect one's own experience in the mirror of voices of many others. If you wish to have access to the editable version contact&nbsp;the.stranger.gets.a.gift@gmail.com&nbsp;

Induced gravitational waves from the cosmic coincidence

The induced gravitational wave (GW) background from enhanced primordial scalar perturbations is one of the most promising observational consequences of primordial black hole (PBH) formation from inflation. We investigate the induced GW spectrum ΩIGW from single-field inflation in the general ultra-slow-roll (USR) framework, restricting the peak frequency band to be inside 10-3-1 Hz and saturating PBH abundance to comprise all dark matter (DM) in the ultralight asteroid-mass window. By invoking successful baryogenesis driven by USR inflation, we verify the viable parameter space for the specific density ratio between baryons and PBH DM observed today, the so-called “cosmic coincidence.” We show that the cosmic coincidence requirement bounds the spectral index n UV in the high frequency limit, ΩIGW(f ≫ 1) ∝ f -2n UV , into 0 < n UV < 1, which implies that baryogenesis triggered by USR inflation for PBHs in the mass range of 10-16-10-12 M⊙ can be tested by upcoming Advanced LIGO and Virgo data and next generation experiments such as LISA, Einstein Telescope, TianQin and DECIGO.

Can dark matter\u2013dark energy interaction alleviate the cosmic coincidence problem?

In this paper we study a model of interacting dark energy–dark matter where the ratio between these components is not constant, changing from early to late times in such a way that the model can solve or alleviate the cosmic coincidence problem (CP). The interaction arises from an assumed relation of the form rho _xpropto rho _d^alpha , where rho _x and rho _d are the energy densities of dark energy and dark matter components, respectively, and alpha is a free parameter. For a dark energy equation of state parameter w=-1 we found that, if alpha =0, the standard Lambda CDM model is recovered, where the coincidence problem is unsolved. For 0<alpha <1, the CP would be alleviated and for alpha sim 1, the CP would be solved. The dark energy component is analyzed with both w=-1 and wne -1. Using Supernovae type Ia and Hubble parameter data constraints, in the case w=-1 we find alpha =0.109^{+0.062}_{-0.072} at 68% C.L., and the CP is alleviated. For wne -1, a degeneracy arises on the w–alpha plane. In order to break such degeneracy we add cosmic microwave background distance priors and baryonic acoustic oscillations data to the constraints, yielding alpha =-0.075pm 0.046 at 68% C.L.. In this case we find that the CP is not alleviated even for 2sigma interval for alpha . Furthermore, this last model is discarded against flat Lambda CDM according to BIC analysis.

Dark energy with oscillatory tracking potential: observational constraints and perturbative effects

ABSTRACT The cosmological models exhibiting tracker properties have great significance in the context of dark energy as they can reach the present value of dark energy density from a wide range of initial conditions, thereby alleviating both the fine-tuning and the cosmic coincidence problem. The α-attractors, which are originally discussed in the context of inflation, can exhibit the properties of dark energy as they can behave like cosmological trackers at early times and show the late-time behaviour of a cosmological constant. In this paper, we study the oscillatory tracker model (OTM), which belongs to the family of α-attractor dark energy models. Using the current observational data sets like cosmic microwave background (CMB), baryon acoustic oscillation, and type 1a supernova data (Pantheon compilation), we constrain the parameters of the model and estimate both the mean and best-fitting values. Although the OTM contains a larger set of parameters than the usual lambda cold dark matter (LCDM) model, the common set of parameters of both agree within $1\, \sigma$ error limits. Our observations using both high redshift and low redshift data support Hubble parameter value H0 = 67.4 Km s−1 Mpc−1. We study the effect of the OTM on the CMB temperature and polarization power spectra, matter power spectrum and fσ8. Our analysis of the CMB power spectrum and matter power spectrum suggests that the oscillatory tracker dark energy model has noticeable differences from usual LCDM predictions. Yet, in most cases, the agreement is very close.

Cosmic Coincidences of Primordial-Black-Hole Dark Matter.

If primordial black holes (PBHs) contribute more than 10% of the dark matter (DM) density, their energy density today is of the same order as that of the baryons. Such a cosmic coincidence might hint at a mutual origin for the formation scenario of PBHs and the baryon asymmetry of the Universe. Baryogenesis can be triggered by a sharp transition of the rolling rate of inflaton from slow-roll to (nearly) ultraslow-roll phases that produce large curvature perturbations for PBH formation in single-field inflationary models. We show that the baryogenesis requirement drives the PBH contribution to DM, along with the inferred PBH mass range, the resulting stochastic gravitational wave background frequency window, and the associated cosmic microwave background tensor-to-scalar ratio amplitude, into potentially observable regimes.