arXiv subjects

Maresuke Shiraishi

Publications and source records attributed to Maresuke Shiraishi.

At least 19 recordsLinked to original sources

arXiv2026

Dipolar power asymmetry in wide-angle correlations of galaxy density, velocity and ellipticity

The large-scale structure of the universe has the potential to probe anomalies suggested by observations of the cosmic microwave background. In this work, we focus on a position-dependent dipolar modulation of the primordial power spectrum and develop a full-sky formalism for computing correlation functions of galaxy density, velocity and ellipticity. By comparing the correlation functions obtained with and without the plane-parallel approximation, we show that wide-angle corrections become non-negligible for opening angles $Θ\gtrsim 30^\circ$. Our results demonstrate that wide-angle corrections must be taken into account when testing the dipolar modulation with future large-scale structure surveys.

astro-ph.CO↗

arXiv2026

Probing dipolar power asymmetry with galaxy clustering and intrinsic alignments

We investigate the prospects for probing large-scale statistical anisotropy through galaxy clustering and intrinsic alignments (IA) in Stage IV galaxy surveys. Specifically, we consider a dipolar modulation in the primordial power spectrum and evaluate the Fisher information matrix using the two-point statistics of both the galaxy clustering and IA. Our analysis reveals that while IA alone provides limited improvement in constraining the anisotropy amplitude, the cross-spectrum between galaxy density and IA can contribute up to half the constraining power of galaxy clustering, especially for surveys with low galaxy bias and high number density of galaxies, such as Euclid. This demonstrates the potential of IA-clustering cross-correlations as a robust consistency check against systematics, and highlights the complementary roles of galaxy clustering and IA in constraining cosmic statistical anisotropy. We also show that marginalizing over galaxy bias and IA bias parameters has a negligible impact on the final constraint on the anisotropy amplitude.

astro-ph.CO↗

arXiv2026

Constraining Primordial Power Asymmetry from Galaxy Clustering and Peculiar Velocity Information

Primordial power asymmetry would probe departures from statistical isotropy, offering a clue to the physics of the primordial Universe. We investigate how such asymmetries can be tested with galaxy surveys and quantify how peculiar-velocity information can improve these tests. We develop a unified bipolar spherical harmonic (BipoSH) analysis of the auto- and cross-power spectra of galaxy density and line-of-sight peculiar velocity, and perform Fisher forecasts combining a Euclid-like spectroscopic galaxy survey with peculiar velocities reconstructed from Simons Observatory-like CMB maps through the kinetic Sunyaev-Zel'dovich effect. For dipolar asymmetry, we consider both scale-independent and scale-dependent modulations proportional to $k^{-0.5}$. Galaxy clustering provides most of the constraining power in both cases, while peculiar velocities add only modest information. For quadrupolar asymmetry, we account for the recently identified anisotropic galaxy-bias response and marginalize over its amplitude. We find that galaxy clustering alone suffers from a degeneracy between the primordial quadrupolar modulation and anisotropic galaxy bias. This degeneracy can be substantially broken by adding peculiar-velocity information: the density-velocity cross-spectrum provides complementary information to the galaxy auto-spectrum, while the velocity auto-spectrum constrains the primordial modulation independently of anisotropic galaxy bias. The velocity information becomes increasingly effective for more negative scale dependence, yielding constraints tighter than those from BOSS for scale dependences proportional to $k^{-1}$ and $k^{-2}$. Our results demonstrate that peculiar-velocity information provides a complementary avenue for testing primordial power asymmetry with large-scale structure, particularly for quadrupolar asymmetry in the presence of anisotropic galaxy bias.

astro-ph.CO↗

arXiv2025

Parity-violating scalar trispectrum from helical primordial magnetic fields

Some recent observations of the cosmic microwave background (CMB) anisotropies and the large-scale structure of the Universe imply cosmic parity violation. Among possible parity-violating sources, helical primordial magnetic fields (PMFs) are of particular interest, as they inherently violate parity symmetry and can explain the observed magnetic fields, especially in void regions. PMFs, if generated in the early universe, can source curvature perturbations, which evolve into the present density fluctuations observed in CMB and galaxy surveys. Motivated by this, we study the imprint of helical PMFs on the trispectrum of the sourced primordial curvature perturbations, which is a leading-order scalar statistics sensitive to parity-violating signals. We derive full expressions for the trispectrum of the primordial curvature perturbations sourced by both the helical and non-helical PMFs and reduce them to computationally-feasible ones using a proper approximation. From numerical works, we confirm that parity-odd signals are efficiently enhanced and surpass parity-even ones in specific momentum and parameter spaces. Parity-violating signatures found in this paper are partially testable with observational implications reported so far. Assuming nearly scale-invariant PMF power spectra and the PMF strength of $B_{r}=4.7 \, {\rm nG}$, we obtain a rough upper bound on the helical-to-non-helical power ratio as $r_H\lesssim 4\times 10^{-4}$. Our findings highlight the primordial trispectrum as a promising probe of helical PMFs and provide a theoretical basis for future precise observations of higher-order statistics in the CMB anisotropies and the galaxy clustering.

astro-ph.CO↗

arXiv2025

First confirmation of anisotropic halo bias from statistically anisotropic matter distributions

We confirm for the first time the existence of distinctive halo bias associated with the quadrupolar type of statistical anisotropy (SA) of the linear matter density field using cosmological $N$-body simulations. We find that the coefficient of the SA-induced bias for cluster-sized halos takes negative values and exhibits a decreasing trend with increasing halo mass. This results in the quadrupole halo power spectra in a statistically anisotropic universe being less amplified compared to the monopole spectra. The anisotropic feature in halo bias that we found presents a promising new tool for testing the hypothesis of a statistically anisotropic universe, with significant implications for the precise verification of anisotropic inflation scenarios and vector dark matter and dark energy models.

astro-ph.CO↗

arXiv2025

Non-Gaussianity Beyond the Scalar Sector: A Search for Tensor and Mixed Tensor-Scalar Bispectra with Planck Data

Primordial gravitational waves could be non-Gaussian, just like primordial scalar perturbations. Although the tensor two-point function has thus-far remained elusive, the three-point function could, in principle, be large enough to be detected in Cosmic Microwave Background temperature and polarization anisotropies. We perform a detailed analysis of tensor and mixed tensor-scalar non-Gaussianity through the Planck PR4 bispectrum, placing constraints on eleven primordial templates, spanning various phenomenological and physical regimes including modifications to gravity, additional fields in inflation, and primordial magnetic fields. All analysis is performed using modern quasi-optimal binned estimators, and yields no evidence for tensor non-Gaussianity, with a maximum detection significance of $2σ$. Our constraints are derived primarily from large-scales (except for tensor-scalar-scalar models), and benefit greatly from the inclusion of $B$-modes. Although we find some loss of information from binning, mask effects and residual foreground contamination, our $f_{\rm NL}$ bounds improve over those of previous analyses by $(20-700)\%$, with six of the eleven models being analyzed for the first time. Unlike for scalar non-Gaussianity, future low-noise experiments such as LiteBIRD, the Simons Observatory and CMB-S4, will yield considerable improvement in tensor non-Gaussianity constraints.

astro-ph.CO↗

arXiv2024

Parity-violating scalar trispectrum from a rolling axion during inflation

We study a mechanism of generating the trispectrum (4-point correlation) of curvature perturbation through the dynamics of a spectator axion field and U(1) gauge field during inflation. Owing to the Chern-Simons coupling, only one helicity mode of gauge field experiences a tachyonic instability and sources scalar perturbations. Sourced curvature perturbation exhibits parity-violating nature which can be tested through its trispectrum. We numerically compute parity-even and parity-odd component of the sourced trispectrum. It is found that the ratio of parity-odd to parity-even mode can reach O(10%) in an exact equilateral momentum configuration. We also investigate a quasi-equilateral shape where only one of the momenta is slightly longer than the other three, and find that the parity-odd mode can reach, and more interestingly, surpass the parity-even one. This may help us to interpret a large parity-odd trispectrum signal extracted from BOSS galaxy-clustering data.

astro-ph.CO↗

arXiv2024

Testing Parity Symmetry with the Polarized Cosmic Microwave Background

New physics in the early Universe could lead to parity-violation in the late Universe, sourcing statistics whose sign changes under point reflection. The best constraints on such phenomena have come from the Planck temperature fluctuations; however, this is already cosmic-variance-limited down to relatively small scales, thus only small improvements are expected in the future. Here, we search for signatures of parity-violation in the polarized CMB, using the Planck PR4 $T$- and $E$-mode data. We perform both a simulation-based blind test for any parity-violating signal at $\ell<518$, and a targeted search for primordial $U(1)$ gauge fields (and the amplitudes of a generic collapsed model) at $\ell<2000$. In all cases, we find no evidence for new physics, with the model-independent test finding consistency with the FFP10/NPIPE simulation suite at $(-)0.4σ$, and the gauge field test constraining the fractional amplitude of gauge fields during inflation to be below $6\times 10^{-19}$ at $95\%$ confidence level for a fiducial model. The addition of polarization data can significantly improve the constraints, depending on the particular model of primordial physics, and the bounds will tighten significantly with the inclusion of smaller-scale information.

astro-ph.CO↗

arXiv2024

Testing Graviton Parity and Gaussianity with Planck T-, E- and B-mode Bispectra

Many inflationary theories predict a non-Gaussian spectrum of primordial tensor perturbations, sourced from non-standard vacuum fluctuations, modified general relativity or new particles such as gauge fields. Several such models also predict a chiral spectrum in which one polarization state dominates. In this work, we place constraints on the non-Gaussianity and parity properties of primordial gravitational waves utilizing the Planck PR4 temperature and polarization dataset. Using recently developed quasi-optimal bispectrum estimators, we compute binned parity-even and parity-odd bispectra for all combinations of CMB T-, E- and B-modes with $2\leq \ell<500$, and perform both blind tests, sensitive to arbitrary three-point functions, and targeted analyses of a well-motivated equilateral gravitational wave template (sourced by gauge fields), with amplitude $f_{\rm NL}^{ttt}$. This is the first time B-modes have been included in primordial non-Gaussianity analyses; they are found to strengthen constraints on the parity-even sector by $\simeq 30\%$ and dominate the parity-odd bounds, without inducing bias. We report no detection of non-Gaussianity (of either parity), with the template amplitude constrained to $f_{\rm NL}^{ttt}=900\pm 700$ (stable with respect to a number of analysis variations), compared to $1300\pm1200$ in Planck 2018. The methods applied herein can be reapplied to upcoming CMB datasets such as LiteBIRD, with the inclusion of B-modes poised to dramatically improve future bounds on tensor non-Gaussianity.

astro-ph.CO↗

arXiv2023

Imprints of primordial magnetic fields on intrinsic alignments of galaxies

Primordial magnetic fields (PMFs) are one of the plausible candidates for the origin of the observed large-scale magnetic fields. While many proposals have been made for the generation mechanism of PMFs by earlier studies, it remains a subject of debate. In this paper, to obtain new insights into PMFs, we focus on the intrinsic alignments (IAs) of galaxies induced by the vector and tensor modes of the anisotropic stress of PMFs. The long-wavelength vector and tensor modes locally induce the tidal gravitational fields, leading to the characteristic distortions of the intrinsic ellipticity of galaxies. We investigate the shear E- and B-mode power spectra induced by the magnetic vector and tensor modes in the three-dimensional space, assuming the combination of galaxy imaging and galaxy redshift surveys. We find that the magnetic tensor mode dominates both the E- and B-mode spectra. In particular, the B-mode spectrum induced by the magnetic tensor mode plays a crucial role in constraining the amplitude of PMFs, even in the presence of the non-magnetic scalar contribution to the B-mode spectrum arising from the one-loop effect. In future galaxy redshift surveys, such as Euclid and Square Kilometre Array, the minimum detectable value reaches $\sim 30 \, \rm nG$, which can potentially get even smaller in proportion to the number of observed galaxies and reach $\sim \mathcal{O}(1 \, {\rm nG})$. Measuring the IAs of galaxies would be a potential probe for PMFs in future galaxy surveys.

astro-ph.CO↗

arXiv2023

Statistical anisotropy in galaxy ellipticity correlations

As well as the galaxy number density and peculiar velocity, the galaxy intrinsic alignment can be used to test the cosmic isotropy. We study distinctive impacts of the isotropy breaking on the configuration-space two-point correlation functions (2PCFs) composed of the spin-2 galaxy ellipticity field. For this purpose, we build a formalism for general types of the isotropy-violating 2PCFs and a methodology to efficiently compute them by generalizing the polypolar spherical harmonic decomposition approach to the spin-weighted version. As a demonstration, we analyze the 2PCFs when the matter power spectrum has a well-known $g_*$-type isotropy-breaking term (induced by, e.g., dark vector fields). We then confirm that some anisotropic distortions indeed appear in the 2PCFs and their shapes rely on a preferred direction causing the isotropy violation, $\hat{d}$. Such a feature can be a distinctive indicator for testing the cosmic isotropy. Comparing the isotropy-violating 2PCFs computed with and without the plane parallel (PP) approximation, we find that, depending on $\hat{d}$, the PP approximation is no longer valid when an opening angle between the directions towards target galaxies is ${\cal O}(1^\circ)$ for the density-ellipticity and velocity-ellipticity cross correlations and around $10^\circ$ for the ellipticity auto correlation. This suggests that an accurate test for the cosmic isotropy requires the formulation of the 2PCF without relying on the PP approximation.

astro-ph.CO↗

arXiv2022

Cosmological gravity probes: connecting recent theoretical developments to forthcoming observations

Since the discovery of the accelerated expansion of the present Universe, significant theoretical developments have been made in the area of modified gravity. In the meantime, cosmological observations have been providing more high-quality data, allowing us to explore gravity on cosmological scales. To bridge the recent theoretical developments and observations, we present an overview of a variety of modified theories of gravity and the cosmological observables in the cosmic microwave background and large-scale structure, supplemented with a summary of predictions for cosmological observables derived from cosmological perturbations and sophisticated numerical studies. We specifically consider scalar-tensor theories in the Horndeski and DHOST family, massive gravity/bigravity, vector-tensor theories, metric-affine gravity, and cuscuton/minimally-modified gravity, and discuss the current status of those theories with emphasis on their physical motivations, validity, appealing features, the level of maturity, and calculability. We conclude that the Horndeski theory is one of the most well-developed theories of modified gravity, although several remaining issues are left for future observations. The paper aims to help to develop strategies for testing gravity with ongoing and forthcoming cosmological observations.

astro-ph.CO↗

arXiv2022

Can primordial parity violation explain the observed cosmic birefringence?

Recently, the cross-correlation between $E$- and $B$-mode polarization of the cosmic microwave background (CMB), which is well explained by cosmic birefringence with rotation angle $β\approx 0.3$ deg, has been found in CMB polarization data. We carefully investigate the possibility of explaining the observed $EB$ correlation by the primordial chiral gravitational waves (CGWs), which can be generated in the parity-violating theories in the primordial Universe. We found that the CGWs scenario does not work due to the overproduction of the $BB$ auto-correlation which far exceeds the observed one by SPTPol and POLARBEAR.

astro-ph.CO↗

arXiv2022

New constraints on axion-gauge field dynamics during inflation from $Planck$ and BICEP/Keck data sets

We present new constraints on spectator axion-${\rm U}(1)$ gauge field interactions during inflation using the latest $Planck$ (PR4) and BICEP/Keck 2018 data releases. This model can source tensor perturbations from amplified gauge field fluctuations, driven by an axion rolling for a few e-folds during inflation. The gravitational waves sourced in this way have a strongly scale-dependent (and chiral) spectrum, with potentially visible contributions to large/intermediate scale $B$-modes of the CMB. We first derive theoretical bounds on the model imposing validity of the perturbative regime and negligible backreaction of the gauge field on the background dynamics. Then, we determine bounds from current CMB observations, adopting a frequentist profile likelihood approach. We study the behaviour of constraints for typical choices of the model's parameters, analyzing the impact of different dataset combinations. We find that observational bounds are competitive with theoretical ones and together they exclude a significant portion of the model's parameter space. We argue that the parameter space still remains large and interesting for future CMB experiments targeting large/intermediate scales $B$-modes.

astro-ph.CO↗

arXiv2022

In-flight polarization angle calibration for LiteBIRD: blind challenge and cosmological implications

We present a demonstration of the in-flight polarization angle calibration for the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimate its impact on the measurement of the tensor-to-scalar ratio parameter, r, using simulated data. We generate a set of simulated sky maps with CMB and polarized foreground emission, and inject instrumental noise and polarization angle offsets to the 22 (partially overlapping) LiteBIRD frequency channels. Our in-flight angle calibration relies on nulling the EB cross correlation of the polarized signal in each channel. This calibration step has been carried out by two independent groups with a blind analysis, allowing an accuracy of the order of a few arc-minutes to be reached on the estimate of the angle offsets. Both the corrected and uncorrected multi-frequency maps are propagated through the foreground cleaning step, with the goal of computing clean CMB maps. We employ two component separation algorithms, the Bayesian-Separation of Components and Residuals Estimate Tool (B-SeCRET), and the Needlet Internal Linear Combination (NILC). We find that the recovered CMB maps obtained with algorithms that do not make any assumptions about the foreground properties, such as NILC, are only mildly affected by the angle miscalibration. However, polarization angle offsets strongly bias results obtained with the parametric fitting method. Once the miscalibration angles are corrected by EB nulling prior to the component separation, both component separation algorithms result in an unbiased estimation of the r parameter. While this work is motivated by the conceptual design study for LiteBIRD, its framework can be broadly applied to any CMB polarization experiment. In particular, the combination of simulation plus blind analysis provides a robust forecast by taking into account not only detector sensitivity but also systematic effects.

astro-ph.CO↗

arXiv2022

Gravitational wave trispectrum in the axion-SU(2) model

We study the trispectrum of the gravitational waves (GWs) generated through the dynamics of an axionic spectator field and SU(2) gauge fields during inflation. In non-Abelian gauge theory, the gauge fields have four-point self-interactions, which induce the tree-level GW trispectrum. We formulate this type of the GW trispectrum including the non-dynamical contributions and evaluate it in the equilateral limit as a unique signal of this model. We find that the ratio of the GW trispectrum to the cube of the scalar power spectrum can be as large as $\mathcal{O}(10^6)$ in the viable parameter space, which could be captured in the CMB observations.

astro-ph.CO↗

arXiv2021

Alcock-Paczynski effects on wide-angle galaxy statistics

The Alcock-Paczynski (AP) effect is a geometrical distortion in three-dimensional observed galaxy statistics. In anticipation of precision cosmology based on ongoing and upcoming all-sky galaxy surveys, we build an efficient method to compute the AP-distorted correlations of galaxy number density and peculiar velocity fields for any larger angular scale not relying on the conventionally used plane-parallel (PP) approximation. Here, instead of the usual Legendre polynomial basis, the correlation functions are decomposed using tripolar spherical harmonic basis; hence, characteristic angular dependence due to the wide-angle AP effect can be rigorously captured. By means of this, we demonstrate the computation of the AP-distorted correlations over the various scales. Comparing our results with the PP-limit ones, we confirm that the errors due to the PP approximation become more remarkable as the visual angle of separation between target galaxies, $Θ$, enlarges, and especially for the density auto correlation, the error exceeds $10\%$ when $Θ\gtrsim 30^\circ$. This highlights the importance of the analysis beyond the PP approximation.

astro-ph.CO↗

arXiv2021

Gaia 400,894 QSO constraint on the energy density of low-frequency gravitational waves

Low frequency gravitational waves (GWs) are keys to understanding cosmological inflation and super massive blackhole (SMBH) formation via blackhole mergers, while it is difficult to identify the low frequency GWs with ground-based GW experiments such as the advanced LIGO (aLIGO) and VIRGO due to the seismic noise. Although quasi-stellar object (QSO) proper motions produced by the low frequency GWs are measured by pioneering studies of very long baseline interferometry (VLBI) observations with good positional accuracy, the low frequency GWs are not strongly constrained by the small statistics with 711 QSOs (Darling et al. 2018). Here we present the proper motion field map of 400,894 QSOs of the Sloan Digital Sky Survey (SDSS) with optical {\it Gaia} EDR3 proper motion measurements whose positional accuracy is $< 0.4$ milli-arcsec comparable with the one of the radio VLBI observations. We obtain the best-fit spherical harmonics with the typical field strength of $\mathcal{O}(0.1)\, μ$arcsec, and place a tight constraint on the energy density of GWs, $Ω_{\rm gw}=(0.964 \pm 3.804) \times 10^{-4}$ (95 \% confidence level), that is significantly stronger than the one of the previous VLBI study by two orders of magnitude at the low frequency regime of $f <10^{-9}\,{\rm [Hz]}\simeq (30\,{\rm yr})^{-1}$ unexplored by the pulsar timing technique. Our upper limit rules out the existence of SMBH binary systems at the distance $r < 400$ kpc from the Earth where the Milky Way center and local group galaxies are included. Demonstrating the limit given by our optical QSO study, we claim that astrometric satellite data including the forthcoming {\it Gaia} DR5 data with small systematic errors are powerful to constrain low frequency GWs.

gr-qc↗