# Anton Chudaykin's research while affiliated with McMaster University and other places

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## Publications (41)

We study the one-point probability distribution function (PDF) for matter density averaged over spherical cells. The leading part to the PDF is defined by the dynamics of the spherical collapse whereas the next-to-leading part comes from the integration over fluctuations around the saddle-point solution. The latter calculation receives sizable cont...

We present the effective-field theory (EFT)-based cosmological full-shape analysis of the anisotropic power spectrum of eBOSS quasars at the effective redshift $z_{\rm eff}=1.48$. We perform extensive tests of our pipeline on simulations, paying a particular attention to the modeling of observational systematics, such as redshift smearing, fiber co...

The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be a...

In this paper we will list a few important goals that need to be addressed in the next decade, also taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant $H_0$, the $\sigma_8$--$S_8$ tension, and other less statistically significant anomalies. While these...

We present new cosmological constraints in a set of motivated extensions of the $\Lambda$CDM model using the polarization and gravitational lensing measurements from the South Polar Telescope and the Planck CMB temperature observations at large angular scales. It was shown in Ref. \cite{Chudaykin:2020acu} that this CMB setup is free from the Planck...

A precise measurement of the curvature of the Universe is of prime importance for cosmology since it could not only confirm the paradigm of primordial inflation but also help in discriminating between different early-Universe scenarios. Recent observations, while broadly consistent with a spatially flat standard Cold Dark Matter (CDM) model, show t...

The standard Cold Dark Matter cosmological model provides a wonderful fit to current cosmological data, but a few statistically significant tensions and anomalies were found in the latest data analyses. While these anomalies could be due to the presence of systematic errors in the experiments, they could also indicate the need for new physics beyon...

A precise measurement of the curvature of the Universe is of prime importance for cosmology since it could not only confirm the paradigm of primordial inflation but also help in discriminating between different early-Universe scenarios. Recent observations, while broadly consistent with a spatially flat standard Λ Cold Dark Matter (ΛCDM) model, sho...

The standard Λ Cold Dark Matter cosmological model provides an amazing description of a wide range of astrophysical and astronomical data. However, there are a few big open questions, that make the standard model look like a first-order approximation to a more realistic scenario that still needs to be fully understood. In this Letter of Interest we...

The standard Λ Cold Dark Matter cosmological model provides a wonderful fit to current cosmological data, but a few statistically significant tensions and anomalies were found in the latest data analyses. While these anomalies could be due to the presence of systematic errors in the experiments, they could also indicate the need for new physics bey...

The current cosmological probes have provided a fantastic confirmation of the standard Λ Cold Dark Matter cosmological model, which has been constrained with unprecedented accuracy. However, with the increase of the experimental sensitivity, a few statistically significant tensions between different independent cosmological datasets emerged. While...

A promising idea to resolve the long standing Hubble tension is to postulate a new subdominant dark-energy-like component in the prerecombination Universe which is traditionally termed as the early dark energy (EDE). However, as shown in the Refs. [J. C. Hill et al., Early dark energy does not restore cosmological concordance, Phys. Rev. D 102, 043...

An important aspect of large-scale structure data analysis is the presence of non-negligible theoretical uncertainties, which become increasingly important on small scales. We show how to incorporate these uncertainties in realistic power spectrum likelihoods by an appropriate change of the fitting model and the covariance matrix. The inclusion of...

We present limits on the parameters of the oΛCDM, w0CDM, and w0waCDM models obtained from the joint analysis of the full-shape, baryon acoustic oscillations (BAO), big bang nucleosynthesis (BBN) and supernovae data. Our limits are fully independent of the data on the cosmic microwave background (CMB) anisotropies, but rival the CMB constraints in t...

A promising idea to resolve the long standing Hubble tension is to postulate a new subdominant dark-energy-like component in the pre-recombination Universe which is traditionally termed as the Early Dark Energy (EDE). However, as shown in Refs. \cite{Hill:2020osr,Ivanov:2020ril} the cosmic microwave background (CMB) and large-scale structure (LSS)...

We present a new open-source code that calculates one-loop power spectra and cross spectra for matter fields and biased tracers in real and redshift space. These spectra incorporate all ingredients required for a direct application to data: nonlinear bias and redshift-space distortions, infrared resummation, counterterms, and the Alcock-Paczynski e...

An important aspect of large-scale structure data analysis is the presence of non-negligible theoretical uncertainties, which become increasingly important on small scales. We show how to incorporate these uncertainties in realistic power spectrum likelihoods by the appropriate change of the fitting model and the covariance matrix. The inclusion of...

We present limits on the parameters of the o$\Lambda$CDM, $w_0$CDM, and $w_0 w_a$CDM models obtained from the joint analysis of the full-shape, baryon acoustic oscillation (BAO), big bang nucleosynthesys (BBN) and supernovae data. Our limits are fully independent from the data on the cosmic microwave background (CMB) anisotropies, but rival the CMB...

A precise measurement of the curvature of the Universe is of primeval importance for cosmology since it could not only confirm the paradigm of primordial inflation but also help in discriminating between different early Universe scenarios. The recent observations, while broadly consistent with a spatially flat standard $\Lambda$ Cold Dark Matter ($...

The standard $\Lambda$ Cold Dark Matter cosmological model provides an amazing description of a wide range of astrophysical and astronomical data. However, there are a few big open questions, that make the standard model look like a first-order approximation to a more realistic scenario that still needs to be fully understood. In this Letter of Int...

The standard $\Lambda$ Cold Dark Matter cosmological model provides a wonderful fit to current cosmological data, but a few tensions and anomalies became statistically significant with the latest data analyses. While these anomalies could be due to the presence of systematic errors in the experiments, they could also indicate the need for new physi...

The current cosmological probes have provided a fantastic confirmation of the standard $\Lambda$ Cold Dark Matter cosmological model, that has been constrained with unprecedented accuracy. However, with the increase of the experimental sensitivity a few statistically significant tensions between different independent cosmological datasets emerged....

It has been recently suggested [F. Bezrukov et al. J. Cosmol. Astropart. Phys. 06 (2017) 051; F. Bezrukov et al. Phys. Rev. D 99, 083507 (2019)] that a cosmic scalar field can completely change the keV-scale sterile neutrino production in the early Universe. Its effect may, for various parameter choices, either suppress sterile neutrino production...

We propose a novel method that utilizes both Planck and SPTPol cosmological datasets. We show that our combined approach predicts consistent lensing-induced smoothing of acoustic peaks within $\Lambda$CDM cosmology and yields the robust predictions of the cosmological parameters. Combining only the Planck and the SPTPol polarization and lensing mea...

We present a new open-source code that calculates one-loop power spectra and cross spectra for matter fields and biased tracers in real and redshift space. These spectra incorporate all ingredients required for a direct application to data: non-linear bias and redshift-space distortions, infra-red resummation, counterterms, and the Alcock-Paczynski...

It has been recently suggested \cite{Bezrukov:2017ike,Bezrukov:2018wvd} that a cosmic scalar field can completely change the keV-scale sterile neutrino production in the early Universe. Its effect may, for various parameter choices, either suppress sterile neutrino production and make moderate active-sterile mixing cosmologically acceptable, or inc...

We present a Markov-Chain Monte-Carlo (MCMC) forecast for the precision of neutrino mass and cosmological parameter measurements with a Euclid-like galaxy clustering survey. We use a complete perturbation theory model for the galaxy one-loop power spectrum and tree-level bispectrum, which includes bias, redshift space distortions, IR resummation fo...

We describe two new generation mechanisms for dark matter (DM) composed of sterile neutrinos with O(1) keV mass. The model contains a light scalar field that coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino. In a region of model parameter space, the oscillations between active and sterile neutrinos...

We describe two new generation mechanisms for Dark Matter composed of sterile neutrinos with $O(1)$ keV mass. The model contains a light scalar field which coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino. In a region of model parameter space, the oscillations between active and sterile neutrinos a...

It has been recently suggested [1] that a subdominant fraction of dark matter decaying after recombination may alleviate tension between high-redshift (CMB anisotropy) and low-redshift (Hubble constant, cluster counts) measurements. In this report, we continue our previous study [2] of the decaying dark matter (DDM) model adding all available recen...

We study a model with a hidden sector coupled to keV scale sterile neutrinos. Due to nontrivial dynamics of this sector, the initially massless sterile neutrino acquires a nonzero mass at some temperature corresponding to the phase transition in the hidden sector. It shifts the onset of oscillations in plasma to later times, so that the final abund...

It has been recently suggested [Berezhiani:2015yta] that a subdominant fraction of dark matter decaying after recombination may alleviate tension between high-redshift (CMB anisotropy) and low-redshift (Hubble constant, cluster counts) measurements. In this report, we continue our previous study [Chudaykin:2016yfk] of the Decaying Dark Matter (DDM)...

We study a model of a keV-scale sterile neutrino with a relatively large mixing with the Standard Model sector. Usual considerations predict active generation of such particles in the early Universe, which leads to constraints from the total Dark Matter density and absence of X-ray signal from sterile neutrino decay. These bounds together may deem...

We confront different up to date cosmological data with different gravity models of the Universe with one additional massive sterile neutrino [1].

It has been recently suggested that emerging tension between cosmological parameter values derived in high redshift (CMB anisotropy) and low redshift (cluster counts, Hubble constant) measurements can be reconciled in a model which contains subdominant fraction of dark matter decaying after recombination. We check the model against the CMB Planck d...

We address the cosmological role of ${\cal O}(1)$ eV sterile neutrino in
modified gravity models. We confront the present cosmological data with the
predictions of FLRW cosmological model based on a variant of $f(R)$ modified
gravity proposed by one of the authors previously. This viable cosmological
model which deviation from general relativity wi...

## Citations

... In recent years, there has been a growing consensus that today's standard model of cosmology, namely, the Lambda cold dark matter (ΛCDM) model, is actually an approximation to a more realistic new cosmological model which is yet to be understood. This new model, which may be conceptually very different, is expected to show slight but probably nontrivial phenomenological deviations from ΛCDM; as despite being in very good agreement with a wide range of astrophysical and cosmological data [1][2][3][4][5][6][7][8], ΛCDM leads to discordances between various cosmological probes increased in diversity and precision over the past decade, e.g., the H 0 and S 8 tensions, and other statistically less significant anomalies [9][10][11][12][13][14][15][16][17]. While these discordances can still be in part the result of systematic errors, the fact that they survived and in some cases are even exacerbated after several years of accurate analyses, points to cracks in ΛCDM, and suggests searching for new physics beyond the wellestablished fundamental theories that underpin, and even extend, the ΛCDM model. ...

... Moreover, we present some novel scenarios that cannot be achieved in GR under same conditions regarding big rip and isotropic initial singularity. It is known that nowadays ΛCDM suffers from persistent tensions of various degrees of significance among some existing datasets [39][40][41][42][43][44][45], thereby, we think that on the road to resolving the current issues and problems of cosmology, such historical considerations might enable us to develop new approaches that are hard to come to mind when we stay within the framework of the standard cosmological model. ...

... Theories of gravity with higher-order invariants arise naturally as an effective description of a complete String Theory [1], and since they can improve the renormalizability properties of general relativity [2] they have attracted the interest of the literature [3]. On the other hand, one may have an additional motivation of cosmological origin [4][5][6], since when applied at a cosmological framework such theories may lead to new effective sectors of gravitational origin, that can drive inflation or late-time acceleration, or alleviate the H 0 and S 8 cosmological tensions [7,8]. ...

... Quantifying in terms of the S 8 parameter (S 8 ≡ σ 8 Ω m /0.3) for σ T φ /b 3 Λ = 0.05, 0.10, 0.20, this results in a suppression ∼ 3%, 5%, and 12% respectively. Interestingly, the suppression in this region of parameter space is enough to help alleviate the S 8 tension [40]. ...

... Furthermore, we also explore whether this model could shed some light on the so-called cosmological tensions, which include the well-known H 0 tension, a ∼ 4σ-discrepancy between direct measurements of H 0 using low-z SN (H 0 = 73.48 ± 1.66 km/s/Mpc [25]) and the H 0 estimate from current CMB data assuming the standard model (H 0 = 67.72 ± 0.41 km/s/Mpc [14]) [26,27]. It is worth mentioning that most of the usual mechanisms to solve this problem have failed so far, as alleviating the H 0 discrepancy worsens the agreement of other parameters with the data. ...

... Moreover, we present some novel scenarios that cannot be achieved in GR under same conditions regarding big rip and isotropic initial singularity. It is known that nowadays ΛCDM suffers from persistent tensions of various degrees of significance among some existing datasets [39][40][41][42][43][44][45], thereby, we think that on the road to resolving the current issues and problems of cosmology, such historical considerations might enable us to develop new approaches that are hard to come to mind when we stay within the framework of the standard cosmological model. ...

... Many attempts to reconcile these discrepancies have been put forward [35][36][37][38][39][40][41]. However, it seems that many suggestions that reduce the Hubble tension seem to increase the S 8 one [42]. ...

... Moreover, we present some novel scenarios that cannot be achieved in GR under same conditions regarding big rip and isotropic initial singularity. It is known that nowadays ΛCDM suffers from persistent tensions of various degrees of significance among some existing datasets [39][40][41][42][43][44][45], thereby, we think that on the road to resolving the current issues and problems of cosmology, such historical considerations might enable us to develop new approaches that are hard to come to mind when we stay within the framework of the standard cosmological model. ...

... However, small-scale ground-based CMB observations such as by ACT and SPT, providing precise measurements of the small-scale power spectrum, have not found this oversmoothing effect (Henning et al. 2018;Aiola et al. 2020;Dutcher et al. 2021). Recently, a combined analysis of Planck (ℓ TT 1000) with ACT and SPT data for EDE models has also been performed, such as CMB+SPTpol (Chudaykin et al. 2020(Chudaykin et al. , 2021Jiang & Piao 2021), CMB+ACT DR4 Poulin et al. 2021 In this paper, we study a scenario with multiple transient phases of dark energy, both before and after the surface of last scattering, yielding a higher value of the current Hubble expansion rate compared to what is inferred from the ΛCDM model. This is a phenomenological model motivated by Firouzjahi (2022b), who studied the quantum vacuum zero-point energy in connection to the cosmological constant problem and the origin of dark energy. ...

... It has been implemented in numerical codes [17][18][19]. Recently, it has been successfully used to extract cosmological parameters from the data [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], including analyses with controlled theoretical uncertainty [36][37][38]. ...