Gotowa bibliografia na temat „Ultra Light Axion Dark Matter (ULADM)”

Abstract It is well known that Ultra-Light Dark Matter (ULDM), usually scalar fields of mass m ∼ 10-22 eV, can solve some of the outstanding problems of the Cold Dark Matter (CDM) paradigm. Such a scalar field could have non-negligible self-coupling λ. In this work, using the known observational upper limit on the amount of centrally concentrated dark matter in a galaxy, we arrive at the observational constraints in the λ-m (self coupling-mass) parameter space. It is found that the observational limit on the mass m of the ULDM depends upon the sign and strength of the self-interactions. We demonstrate that, for m ∼ 10-22 eV, self-coupling values of 𝒪(10-96) (corresponding to a scattering length of as ∼ 10-82 m) can be probed using limits on the dark matter mass within 10 pc of the centre of M87 galaxy. Our analysis suggests that if Ultra Light Axion particles (ULAs) form all of dark matter, dark matter particle mass must be less than ∼ 6 × 10-23 eV.

This is a review on the brief history of the scalar field dark matter model also known as fuzzy dark matter, BEC dark matter, wave dark matter, or ultra-light axion. In this model ultra-light scalar dark matter particles with mass m = O(10-22)eV condense in a single Bose-Einstein condensate state and behave collectively like a classical wave. Galactic dark matter halos can be described as a self-gravitating coherent scalar field configuration called boson stars. At the scale larger than galaxies the dark matter acts like cold dark matter, while below the scale quantum pressure from the uncertainty principle suppresses the smaller structure formation so that it can resolve the small scale crisis of the conventional cold dark matter model.

Abstract We present forecasts on the detectability of Ultra-light axion-like particles (ULAP) from future 21 cm radio observations around the epoch of reionization (EoR). We show that the axion as the dominant dark matter component has a significant impact on the reionization history due to the suppression of small scale density perturbations in the early universe. This behavior depends strongly on the mass of the axion particle. Using numerical simulations of the brightness temperature field of neutral hydrogen over a large redshift range, we construct a suite of training data. This data is used to train a convolutional neural network that can build a connection between the spatial structures of the brightness temperature field and the input axion mass directly. We construct mock observations of the future Square Kilometer Array survey, SKA1-Low, and find that even in the presence of realistic noise and resolution constraints, the network is still able to predict the input axion mass. We find that the axion mass can be recovered over a wide mass range with a precision of approximately 20%, and as the whole DM contribution, the axion can be detected using SKA1-Low at 68% if the axion mass is M X < 1.86 × 10-20 eV although this can decrease to M X < 5.25 × 10-21 eV if we relax our assumptions on the astrophysical modeling by treating those astrophysical parameters as nuisance parameters.

We consider a dark matter halo (DMH) of a spherical galaxy as a Bose–Einstein condensate (BEC) of the ultra-light axions (ULA) interacting with the baryonic matter. In the mean-field (MF) limit, we have derived the integro-differential equation of the Hartree–Fock type for the spherically symmetrical wave function of the DMH component. This equation includes two independent dimensionless parameters: (i) [Formula: see text] is the ratio of baryon and axion total mases and (ii) [Formula: see text] is the ratio of characteristic baryon and axion spatial parameters. We extended our “dissipation algorithm” for studying numerically the ground state of the axion halo in the gravitational field produced by the baryonic component. We calculated the characteristic size, [Formula: see text] of DMH as a function of [Formula: see text] and [Formula: see text] and obtained an analytical approximation for [Formula: see text].

We suggest that the dark matter halo in some of the spiral galaxies can be described as the ground state of the Bose–Einstein condensate of ultra-light self-gravitating axions. We have also developed an effective “dissipative” algorithm for the solution of nonlinear integro-differential Schrödinger equation describing self-gravitating Bose–Einstein condensate. The mass of an ultra-light axion is estimated.

In the heterotic superstring theory, the decay constant of the QCD axion lies within the range 3×1016≲fa GeV ≲1018, the lower limit referring to the model-independent axion, while the upper limit is due to dimension-five, non-renormalizable effects first calculated by Cvetič. Consequently, the neutralino χ0, assumed to be a nearly pure B-ino, decays into the axino ã on the time scale obtained by Covi et al., [Formula: see text], which is ≲10-3 times the age of the Universe t0≈4×1017 s , but can only be made less than the time t≈1 s of the onset of Big-Bang nucleosynthesis by revising mχ0 to an unnaturally high level, mχ0≳500 TeV . Therefore, it is necessary to set the coefficient Ca YY =0, which is possible for the Kim–Shifman–Vainshtein–Zakharov invisible-axion model if the electric charge q c of the heavy-quark colour representation C vanishes. The neutralino does not then decay and can constitute some fraction of the dark matter of the Universe, depending upon the value of mχ0 (for a gaugino-dominated state, [Formula: see text] where [Formula: see text] is the SU(2) singlet slepton). The consequences of an ultra-light axion with fa≈1018 GeV are also discussed.

Abstract The polarization of photons emitted by astrophysical sources might be altered as they travel through a dark matter medium composed of ultra light axion-like particles (ALPs). In particular, the coherent oscillations of the ALP background in the galactic halo induce a periodic change on the polarization of the electromagnetic radiation emitted by local sources such as pulsars. Building up on previous works, we develop a new, more robust, analysis based on the generalised Lomb-Scargle periodogram to search for this periodic signal in the emission of the Crab supernova remnant observed by the QUIJOTE MFI instrument and 20 Galactic pulsars from the Parkes Pulsar Timing Array (PPTA) project. We also carefully take into account the stochastic nature of the axion field, an effect often overlooked in previous works. This refined analysis leads to the strongest limits on the axion-photon coupling for a wide range of dark matter masses spanning 10-23 eV ≲ ma ≲ 10-19 eV. Finally, we survey possible optimal targets and the potential sensitivity to axionic dark-matter in this mass range that could be achieved using pulsar polarimetry in the future.

Abstract Ultra-light axion-like particle (ULAP) with mass m ∼ 10-22 eV has recently been attracting attention as a possible solution to the small-scale crisis. ULAP forms quasi-stable objects called oscillons/I-balls, which can survive up to a redshift z ∼ 10 and affect the structure formation on a scale ∼ 𝒪(0.1) Mpc by amplifying the density fluctuations. We study the effect of oscillons on 21 cm anisotropies caused by neutral hydrogen in minihalos. It is found that this effect can be observed in a wide mass range by future observations such as Square Kilometer Array (SKA) if the fraction of ULAP to the total dark matter density is 𝒪(0.01 – 0.1).

Abstract We search for ultra-light axions as dark matter (DM) and dark energy particle candidates, for axion masses 10-32 eV ≤ m a ≤ 10-24 eV, by a joint analysis of cosmic microwave background (CMB) and galaxy clustering data — and consider if axions can resolve the tension in inferred values of the matter clustering parameter S 8. We give legacy constraints from Planck 2018 CMB data, improving 2015 limits on the axion density Ωa h 2 by up to a factor of three; CMB data from the Atacama Cosmology Telescope and the South Pole Telescope marginally weaken Planck bounds at m a = 10-25 eV, owing to lower (and theoretically-consistent) gravitational lensing signals. We jointly infer, from Planck CMB and full-shape galaxy power spectrum and bispectrum data from the Baryon Oscillation Spectroscopic Survey (BOSS), that axions are, today, < 10% of the DM for m a ≤ 10-26 eV and < 1% for 10-30 eV ≤ m a ≤ 10-28 eV. BOSS data strengthen limits, in particular at higher m a by probing high-wavenumber modes (k < 0.4h Mpc-1). BOSS alone finds a preference for axions at 2.7σ, for m a = 10-26 eV, but Planck disfavours this result. Nonetheless, axions in a window 10-28 eV ≤ m a ≤ 10-25 eV can improve consistency between CMB and galaxy clustering data, e.g., reducing the S 8 discrepancy from 2.7σ to 1.6σ, since these axions suppress structure growth at the 8h -1 Mpc scales to which S 8 is sensitive. We expect improved constraints with upcoming high-resolution CMB and galaxy lensing and future galaxy clustering data, where we will further assess if axions can restore cosmic concordance.

Abstract The JWST early release data show unexpected high stellar mass densities of massive galaxies at 7 < z < 11. A high star formation efficiency is probably needed to explain this. However, such a high star formation efficiency would greatly increase the number of ionizing photons, which would be in serious conflict with current cosmic microwave background (CMB) and other measurements of cosmic reionization history. To solve this problem, we explore fuzzy dark matter (FDM), which is composed of ultra-light scalar particles, e.g., ultra-light axions, and calculate its halo mass function and stellar mass density for different axion masses. We find that a FDM model with m a ≃ 5 × 10−23 eV and a possible uncertainty range ∼3 × 10−23–10−22 eV can effectively suppress the formation of small halos and galaxies, so that with higher star formation efficiency both the JWST data at z ∼ 8 and the reionization history measurements from optical depth of CMB scattering and ionization fraction can be simultaneously matched. We also find that the JWST data at z ∼ 10 are still too high to fit in this scenario. We note that the estimated mean redshift of the sample may have large uncertainty, that it can be as low as z ∼ 9 depending on adopted spectral energy distribution templates and photometric-redshift code. In addition, warm dark matter with ∼keV mass can also be an alternative choice, since it should have similar effects on halo formation as FDM.

The dark matter is the most dominating matter candidate and a key driving force for the structure formation in the universe. Despite decade-long searches, the precise nature and particle properties of dark matter are still unknown. The standard cold dark matter candidate, the Weakly Interacting Massive Particle(WIMP) can successfully describe the large-scale features of the universe. However, when it comes to the scales comparable to a galaxy or a group of galaxies, it fails to explain the observations. The nature of the small-scale anomalies suggests a lower amount of dark matter at the scales of interest and can be tackled with different strategies. The simulation suites, used to produce the small-scale universe theoretically, can be equipped with varieties of baryonic phenomena, leading to a better agreement with observation. Another way is to use some new dark matter candidate altogether that reduces the small-scale power. Many such alternative dark matter candidates have been suggested and explored in the literature. The aim of the work presented in this thesis is to study the effects of small-scale power reduction due to new dark matter physics on different cosmological observables. In Chapter 2 of this thesis, we have discussed the particle physics properties of three dark matter candidates proposed as alternatives of the WIMP. The rst one is the Late Forming Dark Matter(LFDM), where dark matter is created due to a phase transition in the massless neutrino sector [1] long after the Big Bang Nucleosynthesis(BBN). Another candidate is the Ultra Light Axion Dark Matter(ULADM), which is born due to spontaneous symmetry breaking in the early universe and is stuck to its initial condition because of the Hubble drag. When the mass of the particle exceed the Hubble parameter, it decouples from the drag and starts behaving like dark matter [2], with a free-streaming length that is dependent on its mass. The last candidate we consider is the Charged Decaying Dark Matter (CHDM), which is born in iv the radiation dominated era, after an instantaneous decay of a massive charged particle [3]. All of these dark matter candidates suppress small-scale power, though because of different physical reasons. In the next three chapters, we have studied their e ects on various cosmological observables. The methods of study, along with the data used to validate the theoretical predictions and results are discussed below. Chapter 3: This chapter is based on the work performed in [4]. In this chapter, we focus on the LFDM and study its e ects on linear matter power spectra at both small and large scales. Method of Study: The LFDM model is speci ed by two parameters: The effective massless neutrino degrees of freedom(DOF) Ne and the redshift of formation zf . We have generated a set of matter power spectra using publicly available code CAMB for different sets of Ne and zf , and performed a 2 analysis using matter power spectrum data to constrain the model parameters. We have also considered a scenario, where a fraction flfdm of the total dark matter is LFDM and repeated the exercise. We have computed multi-parameter contours and posterior probabilities by marginalization over redundant parameters that allow us to estimate the model parameters. The Data: The two parameters|zf and Ne | affect the linear power spectrum at different scales. The main impact of changing Ne is to alter the MRE epoch, shifting the peak of the matter power spectrum, which is located at k ' 0:01hMpc􀀀1 in the standard model of cosmology. We use the SDSS DR7 data [5] for our analysis. As the SDSS data on the galaxy power spectrum gives the power at scales: k=0:02{0:1 h=Mpc, this data is sensitive to the variation of Ne . On the other hand, the main effect of formation redshift zf is to suppress the power at scales k > 0:1 h=Mpc. In this scales, we use the linear matter power spectrum, reconstructed from Lyman- forest power spectrum in the range: 0:2 < k < 4:8 h=Mpc from [6,7]. We use 45 band-powers from the SDSS galaxy data and 12 points from the reconstructed linear power spectrum from the Lyman- data. Results: Our results can be summarized as follows. If all the presently observed CDM is late forming, then both the data sets lead to upper limits on the redshift of formation of LFDM, with Lyman- data resulting in tighter bounds: zf < 3 106 at 99% con dence limit. On the other hand, if we allow only a fraction of the CDM to form at late times, then we improve the quality of t as compared to the standard CDM model for the Lyman- data. This is suggestive that the present data allows for a fraction 30% of the CDM to form at zf ' 105. Therefore, our result underlines the importance of the Lyman- data for studying the small-scale power spectrum in alternative dark matter regime. Chapter 4: This chapter is based on the work performed in [8]. Here, we have studied the e ects of small-scale power suppression on the Epoch of Reionization(EoR) and the evolution of collapsed fraction of gas at high redshift. We have considered two of the alternative dark matter candidates discussed in Chapter-2 in this chapter: the LFDM and the ULADM. Method of Study: Our method of constructing the reionization fi elds consists of three steps: (i) Generating the dark matter distribution at the desired redshift, (ii) Identifying the location and mass of collapsed dark matter halos within the simulation box, (iii) Generating the neutral hydrogen map using an excursion set formalism. The assumption here is that the hydrogen exactly traces the dark matter eld and the dark matter halos host the ionizing sources. Given the uncertainty of reionization history, we do not assume a particular model for reionization history xHI (z), where xHI is the fraction of neutral hydrogen in the universe. Instead, we xed the redshift at z = 8 and the ionization fraction at xHI = 0:5 and compared these models. We have produced Hi power spectra, and photon brightness temperature fluctuation( Tb) maps to compare the alternative models with the standard CDM model. We discard the models where no halo is formed to host the ionizing sources, or an absurdly high number of ionizing photon is necessary to make xHI = 0:5 at z = 8 successfully. The collapsed fraction, defined as the fraction of collapsed mass in haloes with masses larger than a threshold mass M at a redshift z, is sensitive to the mass function of the haloes. As obtaining the mass function from N-body simulation is numerically expensive, we integrate the Sheth-Tormen mass function above the density threshold of collapse at a given redshift for computing the collapsed fraction in case of LFDM models. For computing the collapsed fraction for ULADM models, we integrate the halo mass functions derived by [9]. The collapsed fractions are calculated for two threshold halo masses, 1010M and 5 1010M in the redshift range 2 < z < 5 and compared to observational data. Models that are unable to produce the observed collapsed fractions at high redshifts are discarded. The Data: From absorption studies of the Damped Lyman- (DLA) clouds, the evolution of average mass density of Hi in the universe can be inferred. Assuming that the collapsed fraction of baryons traces dark matter, this allows us to get an approximate measure of the minimum amount of collapsed fraction of the total matter in the redshift range 2 < z < 5. We have used the data of density of gas trapped in DLAs (HI ), at the mentioned redshift range from [10, 11] and converted them to collapsed fraction of gas. The re-constructed collapsed fractions are used to compare the theoretical predictions. Results: Our method predicts an `inside-out' reionization where the high-density regions are ionized rst. We fi nd that the Hi power for LFDM and ULADM models is greater than the CDM model over a large range of scales 0:1 < k < 4Mpc􀀀1. In the maps of Tb, there are two main differences between CDM and alternative models. The size of the ionized regions is larger in the LFDM (ULADM) models and the Hi elds have stronger density contrast. Checking the facts that halos are actually formed to host stars and a realistic number of ionizing photons are produced to achieve the desired level of ionization, we put a rough limit on zf 4 105 and ma ' 2:6 10􀀀23 eV as lower cut-o s. Comparing the estimated collapsed fraction with data we found weaker constraints on zf . 2 105 and ma . 10􀀀23 eV. All these constraints are in good agreement with previous constraints. Chapter 5: This chapter is based on the work performed in [12]. The observable of interest here is the spectral distortion in the Cosmic Microwave Background(CMB). Method of Study: The distortion on the CMB spectra can occur due to heating or cooling of the medium owing to several mechanisms at di erent times in the history of the universe. In this work, we consider heating due to the dissipation of acoustic waves, well-known as the Silk Damping. The fraction of energy injected into the photon bath is a function of the evolution of the fluctuation in gravitational potential and the CMB dipole 1. We have computed the evolution of and 1 for all the three dark matter candidates studied in Chapter 2, along with the WDM, using the publicly available code CMBFAST and axionCAMB. Using them, we estimate the evolution of the heating rate and integrate it to get the distortion parameters. The distortion parameters thus found are used to calculate the distorted CMB spectrum. The nal output is the percentage change of the distortion parameters for the alternative dark matter models with respect to the CDM model. Results: The two earlier spectral distortions, namely the - and the i-distortion, are not found to be affected due to new dark matter physics. The y-distortion is the only one that carries the signatures of small-scale power suppression. We conclude that, unless the constraints on the model parameters found in previous studies are violated, the change in the y-distortion parameter is not more than 14% compared to the standard model with identical spectral shapes. y-distortion occurring from later phenomena, i.e., structure formation and tSZ e ects in the galaxy clusters have orders of magnitude higher distortion parameters than the Silk Damping, again with the same spectral shape. Thus, unless these foregrounds are understood and cleared correctly, distinguishing between dark matter candidates which reduce small-scale power is next to impossible. Finally, our study shows that changing matter power at small scales can have noticeable impacts on other observables of the universe. However, to see the difference, the phenomena themselves are to be understood properly. The constraints found on the models using different probes are in good agreement with each other. In future, we will extend our research by investigating whether it is possible to accommodate an O(10 eV) particle as a dominating cold dark matter candidate, by exploring its effects on linear matter power spectrum and CMB spectral distortion.