arXiv:2302.04644  [pdf, other] 

Can neutrino-assisted early dark energy models ameliorate the H0 tension in a natural way?

Authors: Diogo H. F. de Souza, Rogerio Rosenfeld

Abstract: The idea of neutrino-assisted early dark energy (νEDE) was introduced with the aim of reducing some of the fine-tuning required in usual early dark energy (EDE) models. The activation of the EDE field around the recombination epoch can arise as a result of a ``neutrino kick" occurring when neutrinos transition from relativistic to nonrelativistic species. We show that although νEDE can open up the parameter space especially with respect to the initial field value, unfortunately the kick alone is insufficient to provide cosmologically interesting values of the relevant EDE parameters. 

Submitted 9 February, 2023; originally announced February 2023.

Comments: 6 pages, 4 figures

arXiv:2209.07804  [pdf, other] 

Isotropic cosmic birefringence from early dark energy

Authors: Kai Murai, Fumihiro Naokawa, Toshiya Namikawa, Eiichiro Komatsu

Abstract: A tantalizing hint of isotropic cosmic birefringence has been found in the EB cross-power spectrum of the cosmic microwave background (CMB) polarization data with a statistical significance of 3σ. A pseudoscalar field coupled to the CMB photons via the Chern-Simons term can explain this observation. The same field may also be responsible for early dark energy (EDE), which alleviates the so-called Hubble tension. Since the EDE field evolves significantly during the recombination epoch, the conventional formula that relates EB to the difference between the E- and B-mode auto-power spectra is no longer valid. Solving the Boltzmann equation for polarized photons and the dynamics of the EDE field consistently, we find that currently favored parameter space of the EDE model yields a variety of shapes of the EB spectrum, which can be tested by CMB experiments. 

Submitted 26 January, 2023; v1 submitted 16 September, 2022; originally announced September 2022.

Comments: 7 pages, 4 figures, 1 table. (v2) Expanded discussion on forecasts for SO and CMB-S4. Accepted for publication in Phys. Rev. D

Report number: RESCEU-16/22

arXiv:2209.06088  [pdf, other] 

Suitability of Magnetic Microbolometers based on Paramagnetic Temperature Sensors for CMB Polarization Measurements

Authors: Juan Manuel Geria, Matias Rolf Hampel, Sebastian Kempf, Juan Jose Bonaparte, Luciano Pablo Ferreyro, Manuel Eliías Garcia Redondo, Daniel Alejandro Almela, Juan Manuel Salum, Nahuel Müller, Jesus David Bonilla-Neira, Alan Ezequiel Fuster, Manuel Platino, Alberto Etchegoyen

Abstract: High resolution maps of polarization anisotropies of the Cosmic Microwave Background (CMB) are in high demand, since the discovery of primordial B-Modes in the polarization patterns would confirm the inflationary phase of the Universe that would have taken place before the last scattering of the CMB at the recombination epoch. Transition Edge Sensors (TES) and Microwave Kinetic Inductance Detectors (MKID) are the predominant detector technologies of cryogenic detector array based CMB instruments that search for primordial B-Modes. In this paper we propose another type of cryogenic detector to be used for CMB survey: A magnetic microbolometer (MMB) that is based on a paramagnetic temperature sensor. It is an adaption of state-of-the-art metallic magnetic calorimeters (MMCs) that are meanwhile a key technology for high resolution α, β, γ and X-ray spectroscopy as well as the study of neutrino mass. The effort to adapt MMCs for CMB surveys is triggered by their lack of Johnson noise associated with the detector readout, the possibility of straightforward calibration and higher dynamic range given it possesses a broad and smooth responsivity dependence with temperature and the absence of Joule dissipation which simplifies the thermal design. A brief proof of concept case study is analyzed, taking into account typical constraints in CMB measurements and reliable microfabrication processes. The results show that MMBs provide a promising technology for CMB polarization survey as their sensitivity can be tuned for background limited detection of the sky while simultaneously maintaining a low time response to avoid distortion of the point-source response of the telescope. As the sensor technology and its fabrication techniques are compatible with TES based bolometric detector arrays, a change of detector technology would even come with very low cost. 

Submitted 16 February, 2023; v1 submitted 13 September, 2022; originally announced September 2022.

Comments: 20 pages, 11 figures. Published in SPIE's Journal of Astronomical Telescopes, Instruments and Systems (JATIS)

Journal ref: J. Astron. Telesc. Instrum. Syst. 9(1), 016002 (2023)

arXiv:2207.14487  [pdf, other] 

Coupled and uncoupled early dark energy, massive neutrinos and the cosmological tensions

Authors: Adrià Gómez-Valent, Ziyang Zheng, Luca Amendola, Christof Wetterich, Valeria Pettorino

Abstract: Some cosmological models with non-negligible dark energy fractions in particular windows of the pre-recombination epoch are capable of alleviating the Hubble tension quite efficiently, while keeping the good description of the data that are used to build the cosmic inverse distance ladder. There has been an intensive discussion in the community on whether these models enhance the power of matter fluctuations, leading {\it de facto} to a worsening of the tension with the large-scale structure measurements. We address this pivotal question in the context of several early dark energy (EDE) models, considering also in some cases a coupling between dark energy and dark matter, and the effect of massive neutrinos. We fit them using the Planck 2018 likelihoods, the supernovae of Type Ia from the Pantheon compilation and data on baryon acoustic oscillations. We find that ultra-light axion-like (ULA) EDE can actually alleviate the H0 tension without increasing the values of σ12 with respect to those found in the ΛCDM, whereas EDE with an exponential potential does not have any impact on the tensions. A coupling in the dark sector tends to enhance the clustering of matter, and the data limit a lot the influence of massive neutrinos, since the upper bounds on the sum of their masses are too close to those obtained in the standard model. We find that in the best case, namely ULA, the Hubble tension is reduced to ∼2σ. 

Submitted 24 October, 2022; v1 submitted 29 July, 2022; originally announced July 2022.

Comments: 27 pages, 16 figures, 8 tables. Version accepted for publication in Phys. Rev. D

arXiv:2207.09824  [pdf, ps, other] 

Peculiar velocities in the early universe

Authors: Myrto Maglara, Christos G. Tsagas

Abstract: Large-scale peculiar motions are commonplace in our universe. Nevertheless, their origin, evolution and implications are still largely unknown. It is generally assumed that bulk motions are a relatively recent addition to the universal kinematics, triggered by the increasing inhomogeneity and anisotropy of the post-recombination epoch. In this work, we focus on the linear evolution of peculiar velocities prior to recombination, namely in the late radiation era and also during a phase of de Sitter inflation. We begin by showing/confirming that bulk motions are triggered and sustained by the non-gravitational forces developed during structure formation. Since density and therefore peculiar-velocity perturbations cannot grow in the baryonic sector before recombination, we consider drift motions in non-baryonic species, which can start growing in the late radiation era. Using relativistic linear cosmological perturbation theory, we find that peculiar motions in the low-energy dark component exhibit power-law growth, which increases further after equipartition. Turning to the very early universe, we consider the evolution of linear peculiar velocities during a phase of de Sitter inflation. We find that typical slow-roll scenarios do not source peculiar motions. Moreover, even if the latter were to be present at the onset of the de Sitter phase, the subsequent exponential expansion should quickly wash away any traces of peculiar-velocity perturbations. 

Submitted 19 October, 2022; v1 submitted 20 July, 2022; originally announced July 2022.

Comments: Typos corrected. Published version

Journal ref: Phys. Rev. D 106, 083505 (2022)

arXiv:2207.06719  [pdf, other

Consistency test of the fine-structure constant from the whole ionization history

Authors: Ke Wang, Lu Chen

Abstract: In cosmology, the fine-structure constant can affect the whole ionization history. However, the previous works confine themselves to the recombination epoch and give various strong constraints on the fine-structure constant. In this paper, we also take the reionization epoch into consideration and do a consistency test of the fine-structure constant from the whole ionization history. From the data combination of Planck 2018, BAO data, SNIa samples, SFR density from UV and IR measurements, and the QHII constraints, we find the constraint on the fine-structure constant during the recombination epoch is αrec/αEM=1.001494+0.002041−0.002063 and its counterpart during the reionization epoch is αrei/αEM=0.854034+0.031678−0.027209 at 68% C.L.. They are not consistent with each other by 4.64σ. A conservative explanation for such a discrepancy is that there are some issues in the data we used. We prefer a calibration of some important parameters involved in reconstructing the reionization history. 

Submitted 2 October, 2022; v1 submitted 14 July, 2022; originally announced July 2022.

Comments: 9 pages, 4 figures

arXiv:2204.08088  [pdf, other

Thermal SZ effect in a magnetized IGM dominated by interacting DM decay/annihilation during dark ages

Authors: Arun Kumar Pandey, Sunil Malik

Abstract: During cosmic dawn, the thermal history of the universe is well studied, and a study of this era can give us some of the most useful insight into the universe before the recombination epoch. Its precise modeling and future high-precision measurements will be a valuable tool for determining the thermal history of the universe. In the present work, we study the thermal and ionization history of IGM in the presence of decaying magnetic fields via ambipolar and turbulent decay, Baryon-Dark matter (BDM) interaction, including the DM decay/annihilation. The BDM interaction cross-sections considered are of the form σ=σ0vn, where n=−2 and n=−4. In this work, we show that in the current scenario, the decay/annihilation of the DM particles have a considerable impact on the temperature and ionization histories at low redshift. With the addition of the concept of fractional interaction, which states that if a fraction of the DM particles interacts with the baryons, the temperature and ionization fraction of the baryons show a strong dependence on the percentage of DM particles interacting with the baryons. We have also studied the interesting consequences of the present scenario on the thermal Sunyaev-Zeldovich (tSZ) effect. We show that the highest value of the absolute value of the mean y−parameter in the current DM decay/annihilation scenario is well within the values derived from experimental data such as PLANCK, FIRAS, and PIXIE. Later we calculate the bound on the ordinary magnetic fields originating from the Dark photons. 

Submitted 17 April, 2022; originally announced April 2022.

Comments: 16 page, 23 Figures (Comments and suggestions are welcome)

arXiv:2111.07288  [pdf, ps, other] 

Inflaton-driven early dark energy

Authors: Michael Maziashvili

Abstract: By arranging the control parameters, we examine whether the mass varying neutrino model PRD 103, 063540 (2021), enabling one to unify inflation with the present dark energy, can be used for producing an early dark energy. The model works in the following way. At early stages of the Big-Bang, the inflaton trapped in the minimum at φ=0 gets uplifted due to interaction with neutrinos and starts to roll down to one of the degenerate minima of the effective potential and after a while gets anchored at this minimum, which in turn evolves in time very slowly. Correspondingly, the early dark energy taking place as a result of this dynamical symmetry breaking also varies in time very slowly. Shortly before the recombination epoch, however, the symmetry is restored and early dark energy disappears. A typical problem of the mass varying neutrino models is that they can hardly provide the needed amount of early dark energy at the tree-level because of smallness of neutrino masses. Nevertheless, the quantum fluctuations of φ can do the job in providing sufficient early dark energy under assumption that inflationary energy scale is of the order of 1\,TeV. Radiative as well as thermal corrections coming from the neutrino sector do not affect the model significantly. As for the gravity induced corrections to the effective potential - they can be safely ignored. 

Submitted 14 November, 2021; originally announced November 2021.

Comments: 8 pages

Journal ref: Astroparticle Physics 145, 102792 (2023)

arXiv:2107.11065  [pdf, other

Early dark energy in the pre- and post-recombination epochs

Authors: Adrià Gómez-Valent, Ziyang Zheng, Luca Amendola, Valeria Pettorino, Christof Wetterich

Abstract: Many quintessence models possess scaling or attractor solutions where the fraction of dark energy follows the dominant component in previous epochs of the expansion, or phase transitions may happen close to matter-radiation equality time. A non-negligible early dark energy (EDE) fraction around matter-radiation equality could contribute to alleviate the H0 tension. We constrain the EDE fraction using two approaches: first, we use a fluid parameterization that mimics the plateaux of the dominant components in the past. An alternative tomographic approach constrains the EDE density in binned redshift intervals. This allows us to reconstruct Ωde(z) before and after the decoupling of the CMB photons. We have employed Planck data 2018, the Pantheon supernovae of Type Ia (SNIa), galaxy clustering data, the prior on the absolute magnitude of SNIa by SH0ES, and weak lensing (WL) data from KiDS+VIKING-450 and DES-Y1. When we use a minimal parameterization mimicking the background plateaux, EDE has only a small impact on current cosmological tensions. The constraints on the EDE fraction weaken considerably when its sound speed is allowed to vary. By means of our binned analysis we put very tight constraints on the EDE fraction around the CMB decoupling time, ≲0.4% at 2σ c.l. We confirm previous results that a significant EDE fraction in the radiation-dominated epoch (RDE) loosens the H0 tension, but tends to worsen the σ8 one. The presence of EDE in the matter-dominated era helps to alleviate this issue. When the SH0ES prior and WL data are considered in the fitting analysis in combination with data from CMB, SNIa and baryon acoustic oscillations, the EDE fractions are constrained to be ≲2.6% in the RDE epoch and ≲1.5% in the redshift range z∈(100,1000) at 2σ c.l. The tensions remain at ∼2−3σ c.l. 

Submitted 22 September, 2021; v1 submitted 23 July, 2021; originally announced July 2021.

Comments: 17 pages, 5 figures, 5 tables. Version accepted for publication in PRD

arXiv:2105.13932  [pdf, other

Updated cosmological constraints on Macroscopic Dark Matter

Authors: Luca Caloni, Martina Gerbino, Massimiliano Lattanzi

Abstract: We revise the cosmological phenomenology of Macroscopic Dark Matter (MDM) candidates, also commonly dubbed as Macros. A possible signature of MDM is the capture of baryons from the cosmological plasma in the pre-recombination epoch, with the consequent injection of high-energy photons in the baryon-photon plasma. By keeping a phenomenological approach, we consider two broad classes of MDM in which Macros are composed either of ordinary matter or antimatter. In both scenarios, we also analyze the impact of a non-vanishing electric charge carried by Macros. We derive constraints on the Macro parameter space from three cosmological processes: the change in the baryon density between the end of the Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) decoupling, the production of spectral distortions in the CMB and the kinetic coupling between charged MDM and baryons at the time of recombination. In the case of neutral Macros we find that the tightest constraints are set by the baryon density condition in most of the parameter space. For Macros composed of ordinary matter and with binding energy I, this leads to the following bound on the reduced cross-section: σX/MX≲6.8⋅10−7(I/MeV)−1.56cm2g−1. Charged Macros with surface potential VX, instead, are mainly constrained by the tight coupling with baryons, resulting in σX/MX≲2⋅10−11(|VX|/MeV)−2cm2g−1. Finally, we show that future CMB spectral distortions experiments, like PIXIE and SuperPIXIE, would have the sensitivity to probe larger regions of the parameter space: this would allow either for a possible evidence or for an improvement of the current bounds on Macros as dark matter candidates. 

Submitted 28 May, 2021; originally announced May 2021.

Comments: 25 pages, 10 figures

arXiv:2105.03704  [pdf, ps, other

Mergers of primordial black holes in extreme clusters and the H0 tension

Authors: Yury Eroshenko

Abstract: We consider a cosmological model with dark matter in the form of ∼10−12M⊙ primordial black holes in dense weakly relativistic clusters with masses 18−560M⊙. It is shown that during the multiple collisions of the black holes the ∼10\% of the initial cluster mass can be transformed into gravitational waves in the time interval from recombination to the redshifts z≥10. At the recombination epoch, the density of matter was larger by ∼10\% and, accordingly, the universe expansion rate was higher. This leads to a shortening of the sound horizon scale, as is necessary to solve the "H0 tension" problem. 

Submitted 14 May, 2021; v1 submitted 8 May, 2021; originally announced May 2021.

Comments: 8 pages, 3 figures; updated with the accepted version

Journal ref: Physics of the Dark Universe 32, 100833 (2021)

arXiv:2102.11257  [pdf, other] 

Axi-Higgs Cosmology

Authors: Leo WH Fung, Lingfeng Li, Tao Liu, Hoang Nhan Luu, Yu-Cheng Qiu, S. -H. Henry Tye

Abstract: If the electroweak Higgs vacuum expectation value v in early universe is ∼1% higher than its present value v0=246 GeV, the 7Li puzzle in BBN and the CMB/ΛCDM tension with late-universe measurements on Hubble parameter are mitigated. We propose a model of an axion coupled to the Higgs field, named ``axi-Higgs'', with its mass ma∼10−30−10−29eV and decay constant fa∼1017−1018GeV, to achieve this goal. The axion initial value aini yields an initial Δvini/v0∼0.01 throughout the BBN-recombination epoch and a percent level contribution to the total matter density today. Because of its very large de Broglie wavelength, this axion matter density ωa suppresses the matter power spectrum, alleviating the CMB/ΛCDM S8/σ8 tension with the weak-lensing data. It also explains the recently reported isotropic cosmic birefringence by its coupling with photons. Adding the axion (m∼10−22eV) in the fuzzy dark matter model to the axi-Higgs model allows bigger Δvrec and ωa to address the Hubble and S8/σ8 tensions simultaneously. The model predicts that Δv may be detected by the spectral measurements of quasars, while its oscillation may be observed in the atomic clock measurements. 

Submitted 3 September, 2021; v1 submitted 22 February, 2021; originally announced February 2021.

Comments: 52 pages, 8 figures. Matches the published version in JCAP

Journal ref: JCAP 08 (2021) 057

arXiv:2101.03740  [pdf, other] 

Comparing early dark energy and extra radiation solutions to the Hubble tension with BBN

Authors: Osamu Seto, Yo Toda

Abstract: The shorten sound horizon scale at the recombination epoch by introducing extra energy components such as the extra radiation or early dark energy (EDE) is a simple approach to so-called the Hubble tension. We compare EDE models, an extra radiation model and an EDE and extra radiation co-existing model with paying attention to the fit to big bang nucleosynthesis (BBN). We find that a fit to BBN in EDE models also is somewhat poorer than that in the ΛCDM model, because the increased inferred baryon asymmetry leads to smaller deuterium abundance. We find that an extra radiation-EDE co-existing model indicates the largest present Hubble parameter H0 between models studied. We also the examine data sets dependence, whether we include BBN or not. The difference in an extra radiation model is 3.22<Neff<3.49(68%) for data sets without BBN and 3.16<Neff<3.40(68%) for data sets with BBN, and is so large that the 1σ border of the larger side becomes the 2σ border. 

Submitted 27 July, 2021; v1 submitted 11 January, 2021; originally announced January 2021.

Comments: 17 pages,10 figures: discussions, figures and references added, version published in Phys. Rev. D

Report number: EPHOU-21-002

Journal ref: Phys. Rev. D 103, 123501 (2021)

arXiv:2011.11086  [pdf, ps, other] 

On Generalized Lemaitre-Tolman-Bondi Metric. Fractal Matter at the end of Matter-Antimatter Recombination

Authors: Sergio Cacciatori, Alessio Marrani, Federico Re

Abstract: Many recent researches have investigated the deviations from the Friedmannian cosmological model, as well as their consequences on unexplained cosmological phenomena, such as dark matter and the acceleration of the Universe. On the one hand, a first order perturbative study of matter inhomogeneity returned a partial explanation of dark matter and dark energy, as relativistic effects due to the retarded potentials of far objects. On the other hand, the fractal cosmology, now modeled with a Lemaitre-Tolman-Bondi (LTB) metric, results in distortions of the luminosity distances of SNe Ia, explaining the acceleration as apparent. In this work we extend the LTB metric to ancient times. The origin of the fractal distribution of matter is explained as the matter remnant after the matter-antimatter recombination epoch. We show that the evolution of such a inhomogeneity necessarily requires a dynamical generalization of LTB, and we propose a particular solution. 

Submitted 22 November, 2020; originally announced November 2020.

Comments: 1+26 pages, 0 figures

arXiv:2009.14174  [pdf, other] 

NANOGrav signal from MHD turbulence at QCD phase transition in the early universe

Authors: A. Neronov, A. Roper Pol, C. Caprini, D. Semikoz

Abstract: The NANOGrav collaboration has recently reported evidence for the existence of a stochastic gravitational wave background in the 1-100 nHz frequency range. We argue that such background could have been produced by magneto-hydrodynamic (MHD) turbulence at the QCD scale. From the NANOGrav measurement one can infer the magnetic field parameters: comoving field strength close to microGauss and a correlation length close to 10\% of the Hubble radius at the QCD phase transition epoch. We point out that the turbulent decay of a non-helical magnetic field with such parameters leads to a magnetic field at the recombination epoch, which would be sufficiently strong to provide a solution to the Hubble tension problem, as recently proposed. We also show that the MHD turbulence interpretation of the NANOGrav signal can be tested via measurements of the relic magnetic field in the voids of the large scale structure, with gamma-ray telescopes like CTA. 

Submitted 16 March, 2021; v1 submitted 29 September, 2020; originally announced September 2020.

Comments: 6 pages, 2 figures

Journal ref: Phys. Rev. D 103, 041302 (2021)

arXiv:1912.04682  [pdf, other] 

Improved model-independent constraints on the recombination era and development of a direct projection method

Authors: Luke Hart, Jens Chluba

Abstract: The precision of recent experiments such as Planck have allowed us to constrain standard and non-standard physics (e.g., due to dark matter annihilation or varying fundamental constants) during the recombination epoch. However, we can also probe this era of cosmic history using model-independent variations of the free electron fraction, Xe, which in turn affects the temperature and polarization anisotropies of the cosmic microwave background. In this paper, we improve on the previous efforts to construct and constrain these generalised perturbations in the ionization history, deriving new optimized eigenmodes based on the full Planck 2015 likelihood data, introducing the new module 'FEARec++'. We develop a direct likelihood sampling method for attaining the numerical derivatives of the standard and non-standard parameters, and discuss complications arising from the stability of the likelihood code. We improve the amplitude constraints of the Planck 2015 principal components constructed here, μ1=−0.09±0.12, μ2=−0.17±0.20 and μ3=−0.30±0.35, finding no indication for departures from the standard recombination scenario. The third mode error is reduced by 60%. We utilise an efficient eigen-analyser that keeps the cross-correlations of the first three eigenmodes to ξμ,μ′<0.1% after marginalisation for all the considered data combinations. We also propose a new projection method for estimating constraints on the parameters of non-standard recombination. Using our eigenmodes, this allows us to recreate the Planck constraint on the two-photon decay rate, A2s1s=7.60±0.64, giving an estimate to within ≃0.05σ of the full MCMC result. The improvements on the analysis using the Planck data will allow us to implement this new method for analysis with fundamental constant variations in the future. 

Submitted 8 June, 2020; v1 submitted 10 December, 2019; originally announced December 2019.

Comments: 17 pages, 20 figures, 7 tables; accepted for publication in MNRAS

arXiv:1912.00190  [pdf, other] 

Can Non-standard Recombination Resolve the Hubble Tension?

Authors: Miaoxin Liu, Zhiqi Huang, Xiaolin Luo, Haitao Miao, Naveen K. Singh, Lu Huang

Abstract: The inconsistent Hubble constant values derived from cosmic microwave background (CMB) observations and from local distance-ladder measurements may suggest new physics beyond the standard ΛCDM paradigm. It has been found in earlier works that, at least phenomenologically, non-standard recombination histories can reduce the ≳4σ Hubble tension to ∼2σ. Following this path, we vary physical and phenomenological parameters in RECFAST, the standard code to compute ionization history of the universe, to explore possible physics beyond standard recombination. We find that the CMB constraint on the Hubble constant is sensitive to the Hydrogen ionization energy and 2s→1s two-photon decay rate, both of which are atomic constants, and is insensitive to other details of recombination. Thus, the Hubble tension is very robust against perturbations of recombination history, unless exotic physics modifies the atomic constants during the recombination epoch. 

Submitted 30 November, 2019; originally announced December 2019.

Comments: 8 pages, 3 figures

Report number: SYSU-SPA-2020 MSC Class: 83F05 ACM Class: J.2

Journal ref: SCPMA, 63(9), 290405, 2020

arXiv:1910.14125  [pdf, other] 

A new method to build the (inverse) distance ladder

Authors: David Camarena, Valerio Marra

Abstract: The cosmic distance ladder is the succession of techniques by which it is possible to determine distances to astronomical objects. Here, we present a new method to build the cosmic distance ladder, going from local astrophysical measurements to the CMB. Instead of relying on high-redshift cosmography in order to model the luminosity-distance relation and calibrate supernovae with BAO, we exploit directly the distance-duality relation dL=(1+z)2dA---valid if photon number is conserved and gravity is described by a metric theory. The advantage is that the results will not depend on the parametrization of the luminosity-distance relation at z>0.15: no model is adopted in order to calibrate BAO with supernovae. This method yields local measurements of the Hubble constant and deceleration parameter. Furthermore, it can directly assess the impact of BAO observations on the strong 4--5σ tension between local and global H0. Using the latest supernova, BAO and CMB observations, we found a consistently low value of q0 and strong inconsistency between angular-only BAO constraints and anisotropic BAO measurements, which are, or not, in agreement with CMB depending on the kind of analysis (see Table~4). We conclude that, in order to understand the reasons behind the H0 crisis, a first step should be clarifying the tension between angular and perpendicular anisotropic BAO as this will help understanding if new physics is required at the pre-recombination epoch or/and during the dark energy era. 

Submitted 17 March, 2020; v1 submitted 30 October, 2019; originally announced October 2019.

Comments: 16 pages, 12 figures, 5 tables. v2 reflects version accepted for publication in MNRAS

Journal ref: MNRAS 495 (3), 2630-2644 (2020)

arXiv:1910.06272  [pdf, ps, other

CMB anisotropy and BBN constraints on pre-recombination decay of dark matter to visible particles

Authors: Sandeep Kumar Acharya, Rishi Khatri

Abstract: Injection of high energy electromagnetic particles around the recombination epoch can modify the standard recombination history and therefore the CMB anisotropy power spectrum. Previous studies have put strong constraints on the amount of electromagnetic energy injection around the recombination era (redshifts z≲4500). However, energy injected in the form of energetic (> keV) visible standard model particles is not deposited instantaneously. The considerable delay between the time of energy injection and the time when all energy is deposited to background baryonic gas and CMB photons, together with the extraordinary precision with which the CMB anisotropies have been measured, means that CMB anisotropies are sensitive to energy that was injected much before the epoch of recombination. We show that the CMB anisotropy power spectrum is sensitive to energy injection even at z=10000, giving stronger constraints compared to big bang nucleosynthesis and CMB spectral distortions. We derive, using Planck CMB data, the constraints on long-lived unstable particles decaying at redshifts z≲10000 (lifetime τX≳1011s) by explicitly evolving the electromagnetic cascades in the expanding Universe, thus extending previous constraints to lower particle lifetimes. We also revisit the BBN constraints and show that the delayed injection of energy is important for BBN constraints. We find that the constraints can be weaker by a factor of few to almost an order of magnitude, depending on the energy, when we relax the quasi-static or on-the-spot assumptions. 

Submitted 18 December, 2019; v1 submitted 14 October, 2019; originally announced October 2019.

Comments: Comments welcome

Journal ref: JCAP12(2019)046

arXiv:1906.09845  [pdf, other] 

Shape and Spin of Minihaloes. II: The Effect of Streaming Velocities

Authors: Maik Druschke, Anna T. P. Schauer, Simon C. O. Glover, Ralf S. Klessen

Abstract: Models of the decoupling of baryons and photons during the recombination epoch predict the existence of a large-scale velocity offset between baryons and dark matter at later times, the so-called streaming velocity. In this paper, we use high resolution numerical simulations to investigate the impact of this streaming velocity on the spin and shape distributions of high-redshift minihalos, the formation sites of the earliest generation of stars. We find that the presence of a streaming velocity has a negligible effect on the spin and shape of the dark matter component of the minihalos. However, it strongly affects the behaviour of the gas component. The most probable spin parameter increases from ∼0.03 in the absence of streaming to ∼0.15 for a run with a streaming velocity of three times σrms, corresponding to 1.4 km\,s−1 at redshift z=15. The gas within the minihalos becomes increasingly less spherical and more oblate as the streaming velocity increases, with dense clumps being found at larger distances from the halo centre. The impact of the streaming velocity is also mass-dependent: less massive objects are influenced more strongly, on account of their shallower potential wells. The number of halos in which gas cooling and runaway gravitational collapse occurs decreases substantially as the streaming velocity increases. However, the spin and shape distributions of gas that does manage to cool and collapse are insensitive to the value of the streaming velocity and we therefore do not expect the properties of the stars that formed from this collapsed gas to depend on the value of the streaming velocity. The spin and shape of this central gas clump are uncorrelated with the same properties measured on the scale of the halo as a whole. 

Submitted 12 August, 2020; v1 submitted 24 June, 2019; originally announced June 2019.

Comments: 16 pages, 21 figures, resubmitted to MNRAS

arXiv:1905.05170  [pdf, other] 

Dark matter component decaying after recombination: constraints from diffuse gamma-ray and neutrino flux measurements

Authors: Oleg E. Kalashev, Mikhail Yu. Kuznetsov, Yana V. Zhezher

Abstract: We consider scenario of the dark matter consisting of two fractions, stable part being dominant and a smaller unstable fraction, which has decayed after the recombination epoch. It has been suggested in Ref. [arxiv:1505.03644] that the above scenario may alleviate tension between high-redshift (CMB anisotropy) and low-redshift (cepheid variables and SNe Ia, cluster counts) cosmological measurements. We derive constraints on the heavy relics branching to qq¯, e+e−, μ+μ−, τ+τ−, νeνe¯, νμνμ¯, W+W− and γγ in the above scenario by comparison of the secondary γ and ν fluxes produced by the process with recent diffuse γ and ν flux measurements. 

Submitted 22 June, 2019; v1 submitted 13 May, 2019; originally announced May 2019.

Comments: 9 pages, 5 figures

Report number: INR-TH-2019-009

arXiv:1905.02441  [pdf, other] 

Revisiting Ryskin's Model of Cosmic Acceleration

Authors: Zhiqi Huang, Han Gao, Haoting Xu

Abstract: Cosmic backreaction as an additional source of the expansion of the universe has been a debate topic since the discovery of cosmic acceleration. The major concern is whether the self interaction of small-scale nonlinear structures would source gravity on very large scales. Gregory Ryskin argued against the additional inclusion of gravitational interaction energy of astronomical objects, whose masses are mostly inferred from gravitational effects and hence should already contain all sources with long-range gravity forces. Ryskin proposed that the backreaction contribution to the energy momentum tensor is instead from the rest of the universe beyond the observable patch. Ryskin's model elegantly solves the fine-tuning problem and is in good agreement with the Hubble diagram of Type Ia supernovae. In this article we revisit Ryskin's model and show that it is {\it inconsistent} with at least one of the following statements: (i) the universe is matter-dominated at low redshift (z≲2); (ii) the universe is radiation-dominated at sufficiently high redshift; (iii) matter density fluctuations are tiny (≲10−4) at the recombination epoch. 

Submitted 9 July, 2019; v1 submitted 7 May, 2019; originally announced May 2019.

Comments: 7 pages; 2 figures; submitted to Astroparticle Physics

Report number: SYSU-SPA-2019 MSC Class: 83F05 ACM Class: J.2

Journal ref: Astroparticle Physics, 114, 77, 2019

arXiv:1902.04512  [pdf, ps, other] 

Mirror magnetic field and its impact on dark matter distribution in galaxies

Authors: Ekaterina Kryukova

Abstract: We obtain the value of the mirror magnetic field during different stages of cosmological evolution. We consider the magnetic field generation in the radiation-dominated era and the post-recombination epoch. We also estimate its galactic low-scale value in the process of dynamo amplification. We discuss a possible effect of the mirror magnetic field on the mirror matter distribution in a galaxy. The model can be generalized by assuming the existence of kinetic mixing between ordinary and mirror particles. 

Submitted 12 February, 2019; originally announced February 2019.

Comments: 15 pages, 2 figures, to be published in JETP

Journal ref: JETP Vol. 156 (1) (2019)

arXiv:1901.07174  [pdf, other] 

Clustering of Hotspots in the Cosmic Microwave Background

Authors: Joel Low, Abel Yang

Abstract: The physics behind the origin and composition of the Cosmic Microwave Background (CMB) is a well-established topic in the field of Cosmology. Literature on CMB anisotropies reveal consistency with Gaussianity, but these were conducted on full multi-frequency temperature maps. In this thesis, we utilise clustering algorithms to specifically conduct statistical analyses on the distribution of hotspots in the CMB. We describe a series of data processing and clustering methodologies conducted, with results that conclusively show that the counts-in-cells distribution of hotspots in the CMB does not follow a Poisson distribution. Rather, the distribution exhibits a much closer fit to both the Negative Binomial Distribution (NBD) and the Gravitational Quasi-Equilibrium Distribution (GQED). From this result, we conclude that structure likely existed in the early universe, from the period of the recombination Epoch, possibly opening new insights in the field of galaxy formation. 

Submitted 21 January, 2019; originally announced January 2019.

Comments: Poster presented at the XLVIII International Symposium on Multiparticle Dynamics (ISMD2018)

arXiv:1812.09488  [pdf, ps, other] 

The role of some collisional processes in AGNs: rate coefficients needed for modeling

Authors: M. S. Dimitrijevic, V. A. Sreckovic, Lj. M. Ignjatovic, B. P. Marinkovic

Abstract: The importance of some atom hydrogen collisions in AGN has been investigated. The results are useful for better estimate of the hydrogen Balmer lines uxes, which usage for effective temperature diagnostics in astrophysical plasma is limited by errors from the line formation models. The data could be also useful for modeling cooler and denser parts of AGN BLR clouds, as well as for the investigation of Rydberg states of hydrogen and for the study of their in uence during the cosmological recombination epoch. The results of the present work suggest that the investigated processes are of interest for the research and modelling of such media. 

Submitted 14 January, 2020; v1 submitted 22 December, 2018; originally announced December 2018.

Comments: 17 pages, 3 figures