arXiv subjects

Naonori Sugiyama

Publications and source records attributed to Naonori Sugiyama.

9 recordsLinked to original sources

arXiv2026

IR-Safe and IR-Resummed Bispectra Before and After Reconstruction in Unified Lagrangian Perturbation Theory

We develop a unified analytic framework for modeling the real-space dark matter bispectrum, including both auto and cross bispectra constructed from pre- and post-reconstruction density fields, based on Unified Lagrangian Perturbation Theory (ULPT). ULPT reorganizes the standard Lagrangian approach by separating the Jacobian deviation, which generates the nonlinear source bispectrum, from the displacement-mapping effect that determines how long-wavelength bulk flows distort observed configurations. Within this structure, we derive general one-loop ULPT expressions for the bispectrum and analyze their infrared (IR) behavior, demonstrating exact, nonperturbative IR cancellation and the natural emergence of an IR-resummed description of baryon acoustic oscillation (BAO) damping. In particular, ULPT enables a detailed and fully analytic treatment of the wiggle-wiggle contribution to the IR-resummed bispectrum, whose structure has remained comparatively unexplored in previous approaches. We further construct IR-resummed models for the cross bispectra of all pre- and post-reconstruction combinations. For configurations in which the displacement fields differ, ULPT captures not only the overall exponential damping but also the more intricate BAO-scale modulation characteristic of mixed pre/post bispectra. Our results clarify the physical origin of nonlinear BAO suppression and provide a compact theoretical framework in which the full ULPT bispectrum, once implemented numerically through displacement-mapping convolution integrals, will automatically encode all nonlinear BAO and IR effects. The framework developed here therefore offers a unified and IR-safe foundation for interpreting next-generation bispectrum measurements.

astro-ph.CO↗

arXiv2025

Renormalization-Free Galaxy Bias in Unified Lagrangian Perturbation Theory

We present a renormalization-free framework for modeling galaxy bias based on Unified Lagrangian Perturbation Theory (ULPT). In this approach, the biased density fluctuation is built solely from Galileon-type operators associated with the intrinsic nonlinear growth of dark matter. This ensures the bias expansion is well defined at the field level, automatically satisfies statistical conditions of vanishing ensemble and volume averages, and removes the need for ad hoc renormalization. We derive analytic one-loop expressions for the galaxy-galaxy and galaxy-matter power spectra and implement an efficient numerical algorithm using \texttt{FFTLog} and \texttt{FAST-PT}, enabling rapid and accurate evaluation. The model requires only a minimal set of bias parameters: three parameters are sufficient to describe correlation functions in configuration space, while four parameters are needed for power spectra in Fourier space. To test accuracy, we jointly fit halo auto- and cross-spectra from the \textit{Dark Emulator}, covering nine redshift-mass combinations with 100 cosmologies each. A single set of bias parameters reproduces both spectra within $\sim1\%$ up to $k \simeq 0.3\,h\,\mathrm{Mpc}^{-1}$ for typical linear bias $b_1 \sim 0.8$-2, and to $k \simeq 0.2\,h\,\mathrm{Mpc}^{-1}$ for $b_1 \sim 3$. The same parameters also match two-point correlation functions down to $r \simeq 15\,h^{-1}\mathrm{Mpc}$. Moreover, ULPT predicts the relation $b_{K^2}^{\mathrm{E}} = -\tfrac{3}{4} b_2^{\mathrm{E}}$, validated against $N$-body results. These results demonstrate that ULPT provides a physically consistent and efficient model for nonlinear galaxy bias, with applications to redshift-space distortions, bispectra, and reconstruction. The numerical implementation is released as the open-source Python package https://github.com/naonori/ulptkit.

astro-ph.CO↗

arXiv2025

One-Loop Nonlinear Matter Power Spectrum from Unified Lagrangian Perturbation Theory: Fast Computation and Comparison with Emulators

We present a fast and accurate formulation for computing the nonlinear matter power spectrum at one-loop order based on Unified Lagrangian Perturbation Theory (ULPT). ULPT decomposes the density field into the Jacobian deviation, capturing intrinsic nonlinear growth, and the displacement-mapping factor, accounting for large-scale distortions due to bulk flows. This structural separation leads to a natural division of the power spectrum into a source term and a displacement-mapping factor, ensuring infrared (IR) safety by construction. We implement an efficient numerical algorithm using FFTLog and FAST-PT, achieving approximately 2-second evaluations on a standard laptop. The results are validated against simulation-based emulators, including the Dark Emulator and Euclid Emulator 2. Across 100 sampled cosmologies, ULPT agrees with emulator predictions at the 2--3\% level up to $ k \simeq 0.4\,h\,\mathrm{Mpc}^{-1} $ for $ z \geq 0.5 $, without any nuisance parameters. Similar agreement is found in configuration space, where the two-point correlation function remains accurate down to $ r \simeq 10\,h^{-1}\mathrm{Mpc} $. Compared to standard perturbation theory, which fails at small scales due to series expansion of the displacement factor, ULPT maintains convergence by preserving its full exponential form. We also clarify the mechanism of BAO damping: exponential suppression by displacement and peak sharpening by nonlinear growth. The combination accurately reproduces BAO features seen in simulations. ULPT thus offers a robust, IR-safe, and computationally efficient framework for modeling large-scale structure in galaxy surveys. The numerical implementation developed in this work is publicly released as the open-source Python package \texttt{ulptkit} (https://github.com/naonori/ulptkit).

astro-ph.CO↗

arXiv2025

Unified Lagrangian Framework for Galaxy Clustering: Consistent Modeling of Bias, Redshift-Space Distortions, and Reconstruction

We present \emph{Unified Lagrangian Perturbation Theory} (ULPT), a perturbative framework for consistently modeling galaxy density fluctuations across real space, redshift space, and post-reconstruction fields. Unlike existing approaches that treat these cases separately, ULPT provides a single theoretical structure that incorporates the three essential coordinate mappings: the Lagrangian-to-Eulerian transformation, the real-to-redshift mapping induced by peculiar velocities, and the remapping from pre to post reconstruction. A key feature of our formulation is the explicit decomposition of the density field into two physically distinct components: the \emph{Jacobian deviation}, which encodes intrinsic linear and nonlinear growth, and the \emph{displacement-mapping effect}, which captures large-scale convective distortions. This separation enables a fully analytic and infrared (IR)-safe resummation, ensuring exact IR cancellation, a consistent Gaussian description of baryon acoustic oscillation (BAO) damping, and the correct residual structure in cross spectra between fields with distinct IR behavior. The perturbative expansion of ULPT naturally generates Galileon-type operators, thereby providing a compact and physically motivated operator basis for nonlinear and nonlocal Lagrangian bias, and allowing for a renormalization-free treatment of biased tracers. Within this framework, we derive a unified expression for the power spectrum that applies equally to dark matter, biased tracers, redshift-space distortions, and reconstructed fields. ULPT thus offers a robust and extensible foundation for precision modeling of large-scale structure, with potential extensions to higher-order statistics, such as the bispectrum, and to other two-point observables, such as galaxy--galaxy lensing.

astro-ph.CO↗

arXiv2024

Discreteness Effects in the Post-Reconstruction Galaxy Power Spectrum

Recent studies have increasingly recognized the value of analyzing the post-reconstruction galaxy power spectrum for investigations into redshift space distortion (RSD) effects. In this paper, we present a novel theoretical model for the post-reconstruction galaxy power spectrum, designed for RSD analyses. In particular, we emphasize the importance of accounting for discrete effects arising from the reconstruction displacement vector, which have been overlooked. We specifically calculate these discrete effects, i.e., shot noise terms, within the framework of standard perturbation theory at the 1-loop level. In addition, we adopt a formulation that accounts for infrared (IR) effects to accurately model the non-linear damping of the Baryon Acoustic Oscillation (BAO) signal. Our model comprehensively integrates key physical phenomena relevant to the post-reconstruction galaxy power spectrum, such as gravitational non-linearities, RSD effects, bias effects, reconstruction effects, reconstruction-specific shot-noise effects, and the non-linear damping of the reconstructed BAO signal, thereby making it applicable to post-reconstruction RSD analyses.

astro-ph.CO↗

arXiv2024

Developing a Theoretical Model for the Resummation of Infrared Effects in the Post-Reconstruction Power Spectrum (an explanatory video is available in the comments section)

Since galaxy distribution reconstruction effectively reduces non-Gaussian terms in the power spectrum covariance matrix, it has attracted interest not only for Baryon Acoustic Oscillation (BAO) signals but also for various cosmological signal analyses. To this end, this paper presents a novel theoretical model that addresses infrared (IR) effects in the post-reconstruction galaxy power spectrum, including 1-loop corrections. In particular, we discuss the importance of incorporating non-perturbative effects arising from IR contributions into the displacement vector $\vec{s}$ used for reconstruction. Consequently, post-reconstruction nonlinear damping of BAO can be described by a single two-dimensional Gaussian function. This is a phenomenon not observed when $\vec{s}$ is considered to at a linear order in the Zel'dovich approximation. Furthermore, we confirm that the cross-power spectrum of the pre- and post-reconstruction density fluctuations lacks IR effect cancellations, and shows an exponential decay in both the cross-power spectrum and the associated shot-noise term. An explanatory video is available at https://youtu.be/u1-xx3_4xCg

astro-ph.CO↗

arXiv2024

Developing a Theoretical Model for the Resummation of Infrared Effects in the Pre- and Post-Reconstruction Galaxy Bispectra (https://youtu.be/bHdlIi3jQ4A)

While substantial progress has been made in studying the pre-reconstruction galaxy bispectrum, investigations of the post-reconstruction bispectrum are still in nascent stages. In this paper, we present a bispectrum model that incorporates one-loop corrections in the Standard Perturbation Theory (SPT), while simultaneously addressing infrared (IR) effects in the post-reconstruction density fluctuations in a non-perturbative approach. This model accurately captures the nonlinear behavior of the Baryon Acoustic Oscillation (BAO) signal within the post-reconstruction bispectrum framework. Furthermore, the incorporation of the one-loop correction extends its applicability to smaller scales. Given that the approach to addressing IR effects remains invariant before and after the reconstruction process, the resulting IR-resummed bispectrum model exhibits uniformity across both scenarios. Throughout this analysis, we achieve a comprehensive and unified description of the bispectrum that seamlessly spans the pre- and post-reconstruction phases. An explanatory video is available at https://youtu.be/bHdlIi3jQ4A.

astro-ph.CO↗

arXiv2019

Microwave Spectro-Polarimetry of Matter and Radiation across Space and Time

This paper discusses the science case for a sensitive spectro-polarimetric survey of the microwave sky. Such a survey would provide a tomographic and dynamic census of the three-dimensional distribution of hot gas, velocity flows, early metals, dust, and mass distribution in the entire Hubble volume, exploit CMB temperature and polarisation anisotropies down to fundamental limits, and track energy injection and absorption into the radiation background across cosmic times by measuring spectral distortions of the CMB blackbody emission. In addition to its exceptional capability for cosmology and fundamental physics, such a survey would provide an unprecedented view of microwave emissions at sub-arcminute to few-arcminute angular resolution in hundreds of frequency channels, a data set that would be of immense legacy value for many branches of astrophysics. We propose that this survey be carried-out with a large space mission featuring a broad-band polarised imager and a moderate resolution spectro-imager at the focus of a 3.5m aperture telescope actively cooled to about 8K, complemented with absolutely-calibrated Fourier Transform Spectrometer modules observing at degree-scale angular resolution in the 10-2000 GHz frequency range. We propose two observing modes: a survey mode to map the entire sky as well as a few selected wide fields, and an observatory mode for deeper observations of regions of specific interest.

astro-ph.CO↗

arXiv2019

A Space Mission to Map the Entire Observable Universe using the CMB as a Backlight

This Science White Paper, prepared in response to the ESA Voyage 2050 call for long-term mission planning, aims to describe the various science possibilities that can be realized with an L-class space observatory that is dedicated to the study of the interactions of cosmic microwave background (CMB) photons with the cosmic web. Our aim is specifically to use the CMB as a backlight -- and survey the gas, total mass, and stellar content of the entire observable Universe by means of analyzing the spatial and spectral distortions imprinted on it. These distortions result from two major processes that impact on CMB photons: scattering by electrons (Sunyaev-Zeldovich effect in diverse forms, Rayleigh scattering, resonant scattering) and deflection by gravitational potential (lensing effect). Even though the list of topics collected in this White Paper is not exhaustive, it helps to illustrate the exceptional diversity of major scientific questions that can be addressed by a space mission that will reach an angular resolution of 1.5 arcmin (goal 1 arcmin), have an average sensitivity better than 1 uK-arcmin, and span the microwave frequency range from roughly 50 GHz to 1 THz. The current paper also highlights the synergy of our BACKLIGHT mission concept with several upcoming and proposed ground-based CMB experiments.

astro-ph.CO↗