arXiv subjects

Jussi Valiviita

Publications and source records attributed to Jussi Valiviita.

At least 19 recordsLinked to original sources

arXiv2025

FuGa3D: Fast full-sky analysis of Galaxy catalogs in 3D

We present FuGa3D, a code for fast computation of correlation functions and power spectra for galaxy survey observables, including galaxy clustering and cosmic shear. We define the redshift-space correlation function (RCF) as the correlation function defined in the parameter space of two redshifts and an angular separation angle. Assuming that there is no preferred direction in the sky, these parameters fully define the relative position of two galaxies, independently of the assumed cosmological model. Once the RCF is constructed, it is easy to compute derived correlation metrics, such as the real-space clustering correlation function and its multipoles. We further define the redshift-space power spectrum as the harmonic counterpart of the RCF, and show that it can be computed efficiently using the discrete galaxy coordinates. We validate the code with simulated mock catalogs. Computing the RCF and the two-point correlation function at 1.5 Mpc (3 Mpc) resolution for a MICE simulation with 46 million galaxies, took 47 node-min for clustering only, and 7.3 node-hours with shear analysis included.

astro-ph.CO↗

arXiv2022

Planck and BICEP/Keck Array 2018 constraints on primordial gravitational waves and perspectives for future B-mode polarization measurements

Current and future B-mode polarization data are the most powerful observables to constrain gravitational waves from the early Universe. We set conservative constraints on tensor modes when relaxing the inflationary consistency condition $n_t=-r/8$ between the tensor tilt $n_t$ and the tensor-to-scalar ratio r. By adding a power-law spectrum of tensor perturbations to $Λ$CDM, and parameterizing this tensor contribution by two independent primordial tensor-to-scalar ratios $(r_1,r_2)$ at $k_1 = 0.005$ Mpc$^{-1}$ and $k_2 = 0.02$ Mpc$^{-1}$, Planck and BICEP/Keck Array 2018 data (BK18) lead to constraints $r_{0.005} < 0.030$ and $r_{0.02} < 0.098$ at 95% CL. The corresponding upper bound $r_{0.01} < 0.039$ is by a factor of 2 tighter than the one obtained with Planck 2018 and the older BK15 data. We then study the perspectives for future CMB experiments that will measure both the reionization bump and recombination peak of the B-mode polarization angular power spectrum, such as LiteBIRD. We test the robustness of the results to the choice of the scales for $(r_1,r_2)$ in these future perspectives. Whereas distinguishing $n_t=-r/8$ from exact scale invariance is impossible as expected, we show how radical, theoretically motivated departures from $n_t=-r/8$, which are consistent with the current data, could be distinguished with LiteBIRD. Moreover, LiteBIRD will be able to shrink the allowed parameter space area in the $(r_{0.005},r_{0.02})$ plane to less than one hundredth of the currently allowed area by Planck 2018 and BK18.

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arXiv2017

Power Spectra Based Planck Constraints on Compensated Isocurvature, and Forecasts for LiteBIRD and CORE Space Missions

Compensated isocurvature perturbations (CIP), where the baryon and cold dark matter perturbations cancel, do not cause total matter isocurvature perturbation. Consequently, at the linear order in the baryon density contrast $Δ$, CIP is not detectable by the CMB power spectra. At the second order CIP smoothes the power spectra in a similar manner as lensing, causing a degeneracy between the CIP variance $Δ^2_{rms}=<Δ^2>$ and lensing parameter $A_L$. We show that the CMB lensing data breaks this degeneracy. Nested sampling of the LCDM+CIP(+$A_L$) model, the Planck 2015 temperature, polarization, and lensing data give $Δ^2_{rms}=0.0069\pm0.0030$ at 68% CL. A non-zero value is favored at 2.3$σ$. CIP with $Δ^2_{rms}=0.007$ improves the bestfit $χ^2$ by 3.6 compared to the adiabatic LCDM model. In contrast, although the temperature data favor $A_L=1.22$, allowing $A_L\ne1$ does not improve the joint fit, since the lensing data disfavor $A_L\ne1$. Indeed, CIP provides a rare example of a simple model, which can reduce the Planck lensing anomaly by fitting well simultaneously the high multipole temperature and lensing data, as well as the polarization data. Finally, we derive forecasts for future satellite missions (LiteBIRD proposal to JAXA and Exploring Cosmic Origins with CORE proposal to ESA's M5 call). Due to its coarse angular resolution, LiteBIRD is not able to improve the constraints on CIP or $A_L$, but CORE-M5 approaches the cosmic variance limit and improves the CIP constraint to $Δ^2_{rms}<0.0006\ (0.0014)$ at 68% (95%) CL, which is 9 times better than the current trispectrum based upper bound and 6 times better than obtained from the simulated Planck data. In addition, CORE-M5 will exquisitely distinguish between CIP and $A_L$. No matter whether CIP is allowed for or not, the uncertainty of the lensing parameter will be $σ(A_L)=0.012$.

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arXiv2016

Testing distance duality with CMB anisotropies

We constrain deviations of the form $T\propto (1+z)^{1+ε}$ from the standard redshift-temperature relation, corresponding to modifying distance duality as $D_L=(1+z)^{2(1+ε)} D_A$. We consider a consistent model, in which both the background and perturbation equations are changed. For this purpose, we introduce a species of dark radiation particles to which photon energy density is transferred, and assume $ε\ge0$. The Planck 2015 release high multipole temperature plus low multipole data give the limit $ε<4.5\times 10^{-3}$ at 95% C.L. The main obstacle to improving this CMB-only result is strong degeneracy between $ε$ and the physical matter densities $ω_{\rm b}$ and $ω_{\rm c}$. A constraint on deuterium abundance improves the limit to $ε<1.8\times 10^{-3}$. Adding the Planck high-multipole CMB polarisation and BAO data leads to a small improvement; with this maximal dataset we obtain $ε<1.3\times 10^{-3}$. This dataset constrains the present dark radiation energy density to at most 12% of the total photon plus dark radiation density. Finally, we discuss the degeneracy between dark radiation and the effective number of relativistic species $N_{\rm eff}$, and consider the impact of dark radiation perturbations and allowing $ε<0$ on the results.

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arXiv2015

Distinguishing interacting dark energy from wCDM with CMB, lensing, and baryon acoustic oscillation data

We employ the Planck 2013 CMB temperature anisotropy and lensing data, and baryon acoustic oscillation (BAO) data to constrain a phenomenological $w$CDM model, where dark matter and dark energy interact. We assume time-dependent equation of state parameter for dark energy, and treat dark matter and dark energy as fluids whose energy-exchange rate is proportional to the dark-matter density. The CMB data alone leave a strong degeneracy between the interaction rate and the physical CDM density parameter today, $ω_c$, allowing a large interaction rate $|Γ| \sim H_0$. However, as has been known for a while, the BAO data break this degeneracy. Moreover, we exploit the CMB lensing potential likelihood, which probes the matter perturbations at redshift $z \sim 2$ and is very sensitive to the growth of structure, and hence one of the tools for discerning between the $Λ$CDM model and its alternatives. However, we find that in the non-phantom models ($w_{\mathrm{de}}>-1$), the constraints remain unchanged by the inclusion of the lensing data and consistent with zero interaction, $-0.14 < Γ/H_0 < 0.02$ at 95\% CL. On the contrary, in the phantom models ($w_{\mathrm{de}}<-1$), energy transfer from dark energy to dark matter is moderately favoured over the non-interacting model; $-0.57 < Γ/H_0 < -0.10$ at 95\% CL with CMB+BAO, while addition of the lensing data shifts this to $-0.46 < Γ/H_0 < -0.01$.

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arXiv2013

Constraints on neutrino density and velocity isocurvature modes from WMAP-9 data

We use WMAP 9-year and other CMB data to constrain cosmological models where the primordial perturbations have both an adiabatic and a (possibly correlated) neutrino density (NDI), neutrino velocity (NVI), or cold dark matter density (CDI) isocurvature component. For NDI and CDI we use both a phenomenological approach, where primordial perturbations are parametrized in terms of amplitudes at two scales, and a slow-roll two-field inflation approach, where slow-roll parameters are used as primary parameters. For NVI we use only the phenomenological approach, since it is difficult to imagine a connection with inflation. We find that in the NDI and NVI cases larger isocurvature fractions are allowed than in the corresponding models with CDI. For uncorrelated perturbations, the upper limit to the primordial NDI (NVI) fraction is 24% (20%) at k = 0.002 Mpc^{-1} and 28% (16%) at k = 0.01 Mpc^{-1}. For maximally correlated (anticorrelated) perturbations, the upper limit to the NDI fraction is 3.0% (0.9%). The nonadiabatic contribution to the CMB temperature variance can be as large as 10% (-13%) for the NDI (NVI) modes. Bayesian model comparison favors pure adiabatic initial mode over the mixed primordial adiabatic and NDI, NVI, or CDI perturbations. At best, the betting odds for a mixed model (uncorrelated NDI) are 1:3.4 compared to the pure adiabatic model. For the phenomenological generally correlated mixed models the odds are about 1:100, whereas the slow-roll approach leads to 1:13 (NDI) and 1:51 (CDI).

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arXiv2012

Constraints on scalar and tensor perturbations in phenomenological and two-field inflation models: Bayesian evidences for primordial isocurvature and tensor modes

We constrain cosmological models where the primordial perturbations have both an adiabatic and a (possibly correlated) cold dark matter (CDM) or baryon isocurvature component. We use both a phenomenological approach, where the primordial power spectra are parametrized with amplitudes and spectral indices, and a slow-roll two-field inflation approach where slow-roll parameters are used as primary parameters. In the phenomenological case, with CMB data, the upper limit to the CDM isocurvature fraction is α<6.4% at k=0.002Mpc^{-1} and 15.4% at k=0.01Mpc^{-1}. The median 95% range for the non-adiabatic contribution to the CMB temperature variance is -0.030<α_T<0.049. Including the supernova (or large-scale structure, LSS) data, these limits become: α<7.0%, 13.7%, and -0.048<α_T< 0.042 (or α<10.2%, 16.0%, and -0.071<α_T<0.024). The CMB constraint on the tensor-to-scalar ratio, r<0.26 at k=0.01Mpc^{-1}, is not affected by the nonadiabatic modes. In the slow-roll two-field inflation approach, the spectral indices are constrained close to 1. This leads to tighter limits on the isocurvature fraction, with the CMB data α<2.6% at k=0.01Mpc^{-1}, but the constraint on α_T is not much affected, -0.058<α_T<0.045. Including SN (or LSS) data, these limits become: α< 3.2% and -0.056<α_T<0.030 (or α<3.4% and -0.063<α_T<-0.008). When all spectral indices are close to each other the isocurvature fraction is somewhat degenerate with the tensor-to-scalar ratio. In addition to the generally correlated models, we study also special cases where the perturbation modes are uncorrelated or fully (anti)correlated. We calculate Bayesian evidences (model probabilities) in 21 different cases for our nonadiabatic models and for the corresponding adiabatic models, and find that in all cases the data support the pure adiabatic model.

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arXiv2009

Adiabatic initial conditions for perturbations in interacting dark energy models

We present a new systematic analysis of the early radiation era solution in an interacting dark energy model to find the adiabatic initial conditions for the Boltzmann integration. In a model where the interaction is proportional to the dark matter density, adiabatic initial conditions and viable cosmologies are possible if the early-time dark energy equation of state parameter is $w_e > -4/5$. We find that when adiabaticity between cold dark matter, baryons, neutrinos and photons is demanded, the dark energy component satisfies automatically the adiabaticity condition. As supernovae Ia or baryon acoustic oscillation data require the recent-time equation of state parameter to be more negative, we consider a time-varying equation of state in our model. In a companion paper [arXiv:0907.4987] we apply the initial conditions derived here, and perform a full Monte Carlo Markov Chain likelihood analysis of this model.

astro-ph.CO↗

arXiv2009

Constraints on primordial isocurvature perturbations and spatial curvature by Bayesian model selection

We present posterior likelihoods and Bayesian model selection analysis for generalized cosmological models where the primordial perturbations include correlated adiabatic and cold dark matter isocurvature components. We perform nested sampling with flat and, for the first time, curved spatial geometries of the Universe, using data from the cosmic microwave background (CMB) anisotropies, the Union supernovae (SN) sample and a combined measurement of the integrated Sachs-Wolfe (ISW) effect. The CMB alone favors a 3% (positively correlated) isocurvature contribution in both the flat and curved cases. The non-adiabatic contribution to the observed CMB temperature variance is 0 < alpha_T < 7% at 98% CL in the curved case. In the flat case, combining the CMB with SN data artificially biases the result towards the pure adiabatic LCDM concordance model, whereas in the curved case the favored level of non-adiabaticity stays at 3% level with all combinations of data. However, the ratio of Bayes factors, or Delta ln(evidence), is more than 5 points in favor of the flat adiabatic LCDM model, which suggests that the inclusion of the 5 extra parameters of the curved isocurvature model is not supported by the current data. The results are very sensitive to the second and third acoustic peak regions in the CMB temperature angular power: therefore a careful calibration of these data will be required before drawing decisive conclusions on the nature of primordial perturbations. Finally, we point out that the odds for the flat non-adiabatic model are 1:3 compared to the curved adiabatic model. This may suggest that it is not much less motivated to extend the concordance model with 4 isocurvature degrees of freedom than it is to study the spatially curved adiabatic model.

astro-ph.CO↗

arXiv2009

Observational constraints on an interacting dark energy model

We use observations of cosmic microwave background anisotropies, supernova luminosities and the baryon acoustic oscillation signal in the galaxy distribution to constrain the cosmological parameters in a simple interacting dark energy model with a time-varying equation of state. Using a Monte Carlo Markov Chain technique we determine the posterior likelihoods. Constraints from the individual data sets are weak, but the combination of the three data sets confines the interaction constant $Γ$ to be less than 23% of the expansion rate of the Universe $H_0$; at 95% CL $-0.23 < Γ/H_0 < +0.15$. The CMB acoustic peaks can be well fitted even if the interaction rate is much larger, but this requires a larger or smaller (depending on the sign of interaction) matter density today than in the non-interacting model. Due to this degeneracy between the matter density and the interaction rate, the only observable effect on the CMB is a larger or smaller integrated Sachs-Wolfe (ISW) effect. While SN or BAO data alone do not set any direct constraints on the interaction, they exclude the models with very large matter density, and hence indirectly constrain the interaction rate when jointly analysed with the CMB data. To enable the analysis described in this paper, we present in a companion paper [arXiv:0907.4981] a new systematic analysis of the early radiation era solution to find the adiabatic initial conditions for the Boltzmann integration.

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arXiv2008

Large-scale instability in interacting dark energy and dark matter fluids

If dark energy interacts with dark matter, this gives a new approach to the coincidence problem. But interacting dark energy models can suffer from pathologies. We consider the case where the dark energy is modelled as a fluid with constant equation of state parameter w. Non-interacting constant-w models are well behaved in the background and in the perturbed universe. But the combination of constant w and a simple interaction with dark matter leads to an instability in the dark sector perturbations at early times: the curvature perturbation blows up on super-Hubble scales. Our results underline how important it is to carefully analyze the relativistic perturbations when considering models of coupled dark energy. The instability that we find has been missed in some previous work where the perturbations were not consistently treated. The unstable mode dominates even if adiabatic initial conditions are used. The instability also arises regardless of how weak the coupling is. This non-adiabatic instability is different from previously discovered adiabatic instabilities on small scales in the strong-coupling regime.

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arXiv2008

Primordial non-gaussianity from multiple curvaton decay

We study a model where two scalar fields, that are subdominant during inflation, decay into radiation some time after inflation has ended but before primordial nucleosynthesis. Perturbations of these two curvaton fields can be responsible for the primordial curvature perturbation. We write down the full non-linear equations that relate the primordial perturbation to the curvaton perturbations on large scales, and solve them in a sudden-decay approximation. We calculate the power spectrum of the primordial perturbation, and finally go to second order to find the non-linearity parameter, fNL. Not surprisingly, we find large positive values of fNL if the energy densities of the curvatons are sub-dominant when they decay, as in the single curvaton case. But we also find a novel effect, which can be present only in multi-curvaton models: fNL becomes large even if the curvatons dominate the total energy density in the case when the inhomogeneous radiation produced by the first curvaton decay is diluted by the decay of a second nearly homogeneous curvaton. The minimum value min(fNL)=-5/4 which we find is the same as in the single-curvaton case. Using (non-)Gaussianity observations, Planck can be able to distinguish between single-field inflation and curvaton model. Hence it is important to derive theoretical predictions for curvaton model. From particle physics point of view it is more natural to assume multiple scalar fields (rather than just one ``curvaton'' in addition to inflaton). Our work updates the theoretical predictions of curvaton model to this case.

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arXiv2007

Hints of Isocurvature Perturbations in the Cosmic Microwave Background?

The improved data on the cosmic microwave background (CMB) anisotropy allow a better determination of the adiabaticity of the primordial perturbation. Interestingly, we find that recent CMB data seem to favor a contribution of a primordial isocurvature mode where the entropy perturbation is positively correlated with the primordial curvature perturbation and has a large spectral index (niso ~ 3). With 4 additional parameters we obtain a better fit to the CMB data by Delta chi^2 = 9.7 compared to an adiabatic model. For this best-fit model the nonadiabatic contribution to the CMB temperature variance is 4%. According to a Markov Chain Monte Carlo analysis the nonadiabatic contribution is positive at more than 95% C.L. The exact C.L. depends somewhat on the choice of priors, and we discuss the effect of different priors as well as additional cosmological data.

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arXiv2007

Primordial non-Gaussianity from two curvaton decays

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arXiv2006

Non-Gaussianity of the primordial perturbation in the curvaton model

We use the delta N -formalism to investigate the non-Gaussianity of the primordial curvature perturbation in the curvaton scenario for the origin of structure. We numerically calculate the full probability distribution function allowing for the non-instantaneous decay of the curvaton and compare this with analytic results derived in the sudden-decay approximation. We also present results for the leading-order contribution to the primordial bispectrum and trispectrum. In the sudden-decay approximation we derive a fully non-linear expression relating the primordial perturbation to the initial curvaton perturbation. As an example of how non-Gaussianity provides additional constraints on model parameters, we show how the primordial bispectrum on CMB scales can be used to constrain variance on much smaller scales in the curvaton field. Our analytical and numerical results allow for multiple tests of primordial non-Gaussianity, and thus they can offer consistency tests of the curvaton scenario.

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arXiv2006

Non-Gaussianity and constraints for the variance of perturbations in the curvaton model

Recently, the primordial non-Gaussianity in the curvaton model has been predicted assuming sudden decay of the curvaton. We extend the calculation to non-instantaneous decay by employing delta N -formalism. The difference between the sudden-decay approximation and our numerical result is larger than 1% only if the non-linearity parameter is small, -1.16 < f_NL < 60. Thus it is safe to use the sudden-decay approximation when deriving constraints for the curvaton model from WMAP3 (f_NL < 114), but with the Planck forecast |f_NL| <5 one should employ the fully numerical result. Often, the curvaton perturbations $δσ$ have been assumed to be small compared to the background value of the curvaton field $σ_0$. Consequently, the variance $Δ^2 = <δσ^2> / σ_0^2$ has been assumed to be negligible. However, the measurements of CMB or large-scale structure perturbation amplitude do not constrain the variance if the main contribution to it comes from the ultraviolet (UV) scales, i.e., from smaller than observable scales. We discuss how, even in this case, observational constraints on non-Gaussianity set an upper bound to the small scale variance, Delta^2_UV < 90.

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arXiv2004

Correlated Primordial Perturbations in Light of CMB and LSS Data

We use cosmic microwave background (CMB) and large-scale structure data to constrain cosmological models where the primordial perturbations have both an adiabatic and a cold dark matter (CDM) isocurvature component. We allow for a possible correlation between the adiabatic and isocurvature modes, and for different spectral indices for the power in each mode and for their correlation. We do a likelihood analysis with 11 independent parameters. We discuss the effect of choosing the pivot scale for the definition of amplitude parameters. The upper limit for the isocurvature fraction is 18% around a pivot scale k = 0.01 Mpc^{-1}. For smaller pivot wavenumbers the limit stays about the same. For larger pivot wavenumbers, very large values of the isocurvature spectral index are favored, which makes the analysis problematic, but larger isocurvature fractions seem to be allowed. For large isocurvature spectral indices n_iso > 2 a positive correlation between the adiabatic and isocurvature mode is favored, and for n_iso < 2 a negative correlation is favored. The upper limit to the nonadiabatic contribution to the CMB temperature variance is 7.5%. Of the standard cosmological parameters, determination of the CDM density $ω_c$ and the sound horizon angle $θ$ (or the Hubble constant $H_0$) are affected most by a possible presence of a correlated isocurvature contribution. The baryon density $ω_b$ nearly retains its ``adiabatic value''.

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arXiv2004

Correlated isocurvature perturbations from mixed inflaton-curvaton decay

We study cosmological perturbations in the case that present-day matter consists of a mixture of inflaton and curvaton decay products. We calculate how the curvaton perturbations are transferred to its decay products in the general case when it does not behave like dust. Taking into account that the decay products of the inflaton can also have perturbations results in an interesting mixture of correlated adiabatic and isocurvature perturbations. In particular, negative correlation can improve the fit to the CMB data by lowering the angular power in the Sachs-Wolfe plateau without changing the peak structure. We do an 11-parameter fit to the WMAP data. We find that the best-fit is not the 'concordance model', and that well-fitting models do not cluster around the best-fit, so that cosmological parameters cannot be reliably estimated. We also find that in our model the mean quadrupole (l=2) power is l(l+1) C_l/2pi = 1081 muK^2, much lower than in the pure adiabatic LCDM model, which gives 1262 muK^2.

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