158 research outputs found
Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
Although the spectrum of primordial fluctuations has been accurately measured
on scales above , only upper limits exist on smaller scales.
In this study, we investigate generic monochromatic enhancements to the
CDM spectrum that trigger the collapse of ultracompact minihalos
(UCMHs) well before standard structure formation. We refine previous treatments
by considering a mixed population of halos with different density profiles,
that should realistically arise as a consequence of late-time accretion and
mergers. Assuming that dark matter (DM) can self-annihilate, we find, as
expected, that UCMHs can greatly enhance the annihilation rate around
recombination, significantly imprinting the cosmic microwave background (CMB)
anisotropies. However, we provide additional insight on the theoretical
uncertainties that currently impact that boost and which may affect late-time
probes such as the 21 cm line or -ray signals. We derive constraints on
the primordial power spectrum on small scales using the ExoCLASS/HYREC codes
and the Planck legacy data. We account for the velocity dependence of the DM
annihilation cross-section (- or -wave), annihilation channel, the DM
particle mass and the inclusion of late-time halo mergers. Our -wave
constraints are competitive with previous literature, excluding primordial
amplitudes at wavenumbers $k \sim 10^4-10^7 \
\rm{Mpc}^{-1}p$-wave processes
have constraining power on the primordial spectrum for cross-sections still
allowed by currently the strongest astrophysical constraints. Finally, we
provide an up-to-date compilation of the most stringent limits on the
primordial power spectrum across a wide range of scales.Comment: 26+18 pages, 12 figures. Added citations and reshaped the appendices.
v2 matches the published JCAP version. Comments welcome
Probing Early Modification of Gravity with Planck, ACT and SPT
We consider a model of early modified gravity (EMG) that was recently
proposed as a candidate to resolve the Hubble tension. The model consists in a
scalar field with a non-minimal coupling (NMC) to the Ricci curvature
of the form and an effective mass
induced by a quartic potential . We present the
first analyses of the EMG model in light of the latest ACT DR4 and SPT-3G data
in combination with full Planck data, and find a preference
for a non-zero EMG contribution from a combination of primary CMB data alone,
mostly driven by ACT DR4 data. This is different from popular 'Early Dark
Energy' models, which are detected only when the high- information from
Planck temperature is removed. We find that the NMC plays a key role in
controlling the evolution of density perturbations that is favored by the data
over the minimally coupled case. Including measurements of supernovae
luminosity distance from Pantheon+, baryonic acoustic oscillations and growth
factor from BOSS, and CMB lensing of Planck leaves the preference unaffected.
In the EMG model, the tension with SES is alleviated from
to . Further adding SES data rise the detection of the EMG
model above .Comment: 25 pages, 9 figures, 5 tables. Comments welcome
The weak, the strong and the ugly -- A comparative analysis of interacting stepped dark radiation
Models which address both the Hubble and tensions with the same
mechanism generically cause a pre-recombination suppression of the small scale
matter power spectrum. Here we focus on two such models. Both models introduce
a self-interacting dark radiation fluid scattering with dark matter, which has
a step in its abundance around some transition redshift. In one model, the
interaction is weak and with all of the dark matter whereas in the other it is
strong but with only a fraction of the dark matter. The weakly interacting case
is able to address both tensions simultaneously and provide a good fit to a the
Planck measurements of the cosmic microwave background (CMB), the Pantheon Type
Ia supernovae, and a combination of low and high redshift baryon acoustic
oscillation data, whereas the strongly interacting model cannot significantly
ease both tensions simultaneously. The addition of high-resolution cosmic
microwave background (CMB) measurements (ACT DR4 and SPT-3G) slightly limits
both model's ability to address the Hubble tension. The use of the effective
field theory of large-scale structures analysis of BOSS DR12 LRG and eBOSS DR16
QSO data additionally limits their ability to address the tension. We
explore how these models respond to these data sets in detail in order to draw
general conclusions about what is required for a mechanism to address both
tensions. We find that in order to fit the CMB data the time dependence of the
suppression of the matter power spectrum plays a central role.Comment: 22 pages, 17 figures, 5 tables. Any comment is welcome
Third EuCAPT Annual Symposium
Although the CMB and galaxy surveys provide precise measurements of the primordial power spectrum at large scales, the small-scale power spectrum remains largely unconstrained. An enhancement in the small-scale primordial spectrum can lead to the formation of Ultra-Compact-Mini-Halos (UCMH) much earlier than standard halo can form. As a result, the DM annihilation signal receives a boost than can strongly impact the CMB power spectra. In this talk, I briefly discuss how to model the effect of s- and p-wave annihilations in UCMHs onto the CMB. I quantify the impact of late-time halo mergers using excursion set theory, and argue that the associated uncertainty in the boost of energy injection is limited for the CMB, but can have serious consequences for late time probes (i.e. for the 21-cm signal). Finally, I demonstrate that the derived CMB constraints on the amplitude of the small-scale spectrum are competitive with those coming from gamma-ray observations, even for p-wave processes
A step in the right direction? Analyzing the Wess Zumino Dark Radiation solution to the Hubble tension
The Wess Zumino Dark Radiation (WZDR) model first proposed in arXiv:2111.00014 shows great promise as a well-motivated simple explanation of the Hubble tension between local and CMB-based measurements. In this work we investigate the assumptions made in the original proposal and confront the model with additional independent data sets. We show that the original assumptions can have an impact on the overall results but are usually well motivated. We further demonstrate that the preference for negative remains at a similar level as for the CDM model, while the tension is slightly increased. Furthermore, the tension between Planck data for and is significantly reduced for the WZDR model. The independent data sets show slightly more permissive bounds on the Hubble parameter, allowing the tension to be further reduced to (CMB-independent) or (ACT+WMAP). However, no combination shows a large preference for the presence of WZDR. We also investigate whether additional dark radiation -- dark matter interactions can help in easing the tension as well. Assuming all of the dark matter to be interacting and a temperature-independent scattering rate, we find that the CMB data are too restrictive on this additional component as to allow a significant decrease in the clustering
Early dark energy resolution to the Hubble tension in light of weak lensing surveys and lensing anomalies
International audienceA constant early dark energy (EDE) component contributing a fraction fEDE(zc)âŒ10% of the energy density of the universe around zcâ3500 and diluting as or faster than radiation afterwards, can provide a simple resolution to the Hubble tension, the âŒ5Ï discrepancyâin the ÎCDM contextâbetween the H0 value derived from early- and late-universe observations. However, it has been pointed out that including Large-Scale Structure (LSS) data, which are in âŒ3Ï tension with ÎCDM and EDE cosmologies, might break some parameter degeneracy and alter these conclusions. We reassess the viability of the EDE against a host of high- and low-redshift measurements, by combining LSS observations from recent weak lensing (WL) surveys with CMB, baryon acoustic oscillation (BAO), growth function (FS) and Supernova Ia (SNIa) data. Introducing a model whose only parameter is fEDE(zc), we report in agreement with past work a âŒ2Ï preference for nonzero fEDE(zc) from Planck CMB data alone, while the tension with the local H0 measurement from sh0es is reduced below 2Ï. Adding BAO, FS and SNIa does not affect this conclusion, while the inclusion of a prior on H0 from sh0es increase the preference for EDE over ÎCDM to the âŒ3.6Ï level. After checking the EDE nonlinear matter power spectrum as predicted by standard semi-analytical algorithms via a dedicated set of N-body simulations, we test the 1-parameter EDE cosmology against WL data. We find that it does not significantly worsen the fit to the S8 measurement as compared to ÎCDM, and that current WL observations do not exclude the EDE resolution to the Hubble tension. We also caution against the interpretation of constraints obtained from combining statistically inconsistent datasets within the ÎCDM cosmology. In light of the CMB lensing anomalies, we show that the lensing-marginalized CMB data also favor nonzero fEDE(zc) at âŒ2Ï, predicts H0 in 1.4Ï agreement with sh0es and S8 in 1.5Ï and 0.8Ï agreement with kids-viking and des respectively. There still exists however a âŒ2.5Ï tension with the joint results from kids-viking and des. With an eye on Occamâs razor, we finally discuss promising extensions of the EDE cosmology that could allow us to fully restore cosmological concordance
Linear cosmological constraints on two-body decaying dark matter scenarios and the S8 tension
International audienceThe âS8 tensionâ is a long-standing discrepancy between the cosmic microwave background (CMB) and weak gravitational lensing determination of the amplitude of matter fluctuations, parametrized as S8âĄÏ8(Ωm/0.3)0.5, where Ï8 is the root-mean-square of matter fluctuations on an 8ââh-1âMpc scale, and Ωm is the total matter abundance. It was recently shown that dark matter (DM) decaying into a massless (dark radiation) and a massive (warm DM) species, with a lifetime Î-1â55(Ï”/0.007)1.4ââGyrâwhere Ï” represent the mass-energy fraction transferred to the massless componentâcan ease the tension. Thanks to a fast and accurate fluid approximation scheme for the warm species, we perform a comprehensive study of this two-body decaying DM scenario, discussing in detail its dynamics and its impact on the CMB and linear matter power spectra. We then investigate the implications for the S8 tension against a number of changes in the analysis: different S8 priors, marginalization over the lensing information in Planck data, trading Planck high-â polarization data for those from the SPTpol and ACTPol surveys, and the inclusion of the recent results from the Xenon1T Collaboration. We conclude that the preference for decaying DM, apparent only when the S8 value determined from weak lensing data is added to the analysis, does not sensibly degrade the fit to any of the cosmological datasets considered, and that the model could potentially explain the anomalous electron recoil excess reported by the Xenon1T Collaboration. Furthermore, we explictly show that while current CMB data alone are not sensitive enough to distinguish between standard cold DM and decaying DM, next-generation CMB observations (CMB-S4) can unambiguously detect its signature
Ruling out QCD phase transition as a PBH origin of LIGO/Virgo events
The best-motivated scenario for a sizable primordial black hole (PBH) contribution to the LIGO/Virgo binary black hole mergers invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. We reconsider the expected mass function associated not only to the QCD phase transition proper, but also the following particle antiparticle annihilation processes, and analyse the constraints on this scenario from a number of observations: The specific pattern in cosmic microwave background (CMB) anisotropies induced by accretion onto PBHs, CMB spectral distortions, gravitational wave searches, and direct counts of supermassive black holes at high redshift. We find that the scenario is not viable, unless an ad hoc mass evolution for the PBH mass function and a cutoff in power-spectrum very close to the QCD scale are introduced by hand
Ruling out QCD phase transition as a PBH origin of LIGO/Virgo events
The best-motivated scenario for a sizable primordial black hole (PBH) contribution to the LIGO/Virgo binary black hole mergers invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. We reconsider the expected mass function associated not only to the QCD phase transition proper, but also the following particle antiparticle annihilation processes, and analyse the constraints on this scenario from a number of observations: The specific pattern in cosmic microwave background (CMB) anisotropies induced by accretion onto PBHs, CMB spectral distortions, gravitational wave searches, and direct counts of supermassive black holes at high redshift. We find that the scenario is not viable, unless an ad hoc mass evolution for the PBH mass function and a cutoff in power-spectrum very close to the QCD scale are introduced by hand
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