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0108-20 补录

优先级 60　·　引力波电磁对应体　·　多信使触发与联合　·　方法

A template-based search for large-scale-structure-correlated anisotropy in the nanohertz gravitational-wave background using the public NANOGrav 15-year data set

利用公开 NANOGrav 15 年数据集模板搜索纳赫兹引力波背景中与大尺度结构相关的各向异性

✉ Yun Fang (Institute of Fundamental Physics and Quantum Technology, Ningbo University; BINGO Center, Ningbo University; School of Physical Science and Technology, Ningbo University)

原文摘要Abstract

Recent PTA analyses reporting evidence for a nanohertz common-spectrum process motivate targeted tests of whether any anisotropic component of the stochastic gravitational-wave background (SGWB) is correlated with the nearby large-scale structure (LSS), as anticipated for an astrophysical background dominated by supermassive black hole binaries. We present the first Bayesian PTA likelihood analysis that embeds an externally observed, full-sky galaxy-survey LSS template directly as an overlap-reduction-function (ORF) component. Using the 2MASS photometric redshift (2MPZ) galaxy catalog, we construct low-multipole LSS-correlated ORF templates in two redshift slices (0 < z ⩽ 0.1 and 0.1 < z ⩽ 0.2) and model PTA cross-correlations as <inline-formula><mml:math><mml:msub><mml:mi>Γ</mml:mi><mml:mrow><mml:mi>a</mml:mi><mml:mi>b</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:msubsup><mml:mi>Γ</mml:mi><mml:mrow><mml:mi>a</mml:mi><mml:mi>b</mml:mi></mml:mrow><mml:mrow><mml:mtext>HD</mml:mtext></mml:mrow></mml:msubsup><mml:mo>+</mml:mo><mml:msub><mml:mi>Σ</mml:mi><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>ϵ</mml:mi><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msub><mml:msubsup><mml:mi>Γ</mml:mi><mml:mrow><mml:mi>a</mml:mi><mml:mi>b</mml:mi></mml:mrow><mml:mrow><mml:mtext>LSS</mml:mtext><mml:mo>(</mml:mo><mml:mi>i</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>, where ϵi quantifies the amplitude of an SGWB component whose angular correlations project onto the fixed 2MPZ LSS templates. Applying this framework to the NANOGrav 15-year dataset, we find no evidence for an LSS-correlated component: the inferred ϵi values are consistent with zero in both single-bin and two-bin analyses (e.g., <inline-formula><mml:math><mml:msub><mml:mi>ϵ</mml:mi><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:msubsup><mml:mn>0.20</mml:mn><mml:mrow><mml:mo>−</mml:mo><mml:mn>1.66</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>1.68</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula> and <inline-formula><mml:math><mml:msub><mml:mi>ϵ</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mo>−</mml:mo><mml:msubsup><mml:mn>0.11</mml:mn><mml:mrow><mml:mo>−</mml:mo><mml:mn>1.83</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>2.04</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula>; 68% credible intervals), and Bayes factors favor the isotropic Hellings-Downs hypothesis (<inline-formula><mml:math><mml:msub><mml:mrow><mml:mrow><mml:mi>B</mml:mi></mml:mrow></mml:mrow><mml:mrow><mml:msub><mml:mtext>HD+LSS</mml:mtext><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:mo>,</mml:mo><mml:mtext>HD</mml:mtext></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>0.40</mml:mn><mml:mo>,</mml:mo><mml:msub><mml:mrow><mml:mrow><mml:mi>B</mml:mi></mml:mrow></mml:mrow><mml:mrow><mml:msub><mml:mtext>HD+LSS</mml:mtext><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>,</mml:mo><mml:mtext>HD</mml:mtext></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>0.43</mml:mn><mml:mo>,</mml:mo><mml:msub><mml:mrow><mml:mrow><mml:mi>B</mml:mi></mml:mrow></mml:mrow><mml:mrow><mml:msub><mml:mtext>HD+LSS</mml:mtext><mml:mrow><mml:mn>1</mml:mn><mml:mo>+</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>,</mml:mo><mml:mtext>HD</mml:mtext></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>0.11</mml:mn></mml:math></inline-formula>). We therefore place upper limits on any 2MPZ-traced, LSS-correlated contribution to the SGWB at z < 0.2. More broadly, our framework provides a reproducible pathway for incorporating observed LSS information into PTA anisotropy searches and naturally motivates extensions to finer redshift tomography and next-generation PTA datasets.

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AI 综述 AI-generated · 以原文为准

亮点

创新点在于把实测星系巡天大尺度结构模板直接嵌入重叠缩减函数（ORF）似然，无需重构完整 GW 天空即可检验 SGWB 是否追踪近邻宇宙大尺度结构；框架可复现，并为低信噪比 PTA 各向异性搜索提供了可扩展的模板化路径。

脉络与展望

既往 PTA 各向异性研究大多采用无模型球谐/天图重建，仅在低阶多极上给出上限（Agazie+ 2023；Mingarelli+ 2013）。近年来，星系巡天与 SGWB 的交叉相关被证明可在强泊松散粒噪声下提升灵敏度（Yang+ 2023；Cusin+ 2025）。本文首次将 2MPZ 实测星系模板直接嵌入 ORF 似然，提供一种低维度、免重构 GW 天空的模板检验；当前 NANOGrav 15 年数据未显示 LSS 相关分量，贝叶斯因子偏向 HD。未来更细红移层析、更广/更深星系巡天以及下一代 PTA/SKA 数据集有望使这种交叉相关检验进入预测性探测阶段（Cusin+ 2025；Sah & Mukherjee 2026）。

预印本 2026-03-02 · 接收 2026-05-09 · 刊出 2026-07-27 · 收录 2026-08-20

ADS:2026SCPMA..6990411F ↗arXiv:2603.02110 ↗DOI ↗

边缘相关 2 篇 · 低相关性展开＋

优先级 20

Current and future constraints on the expansion history of the GREA model

Graziotti, Irene, De Leo, Chiara, Martinelli, Matteo

原文摘要Abstract

In this work, we investigate the General Relativistic Entropic Acceleration (GREA) framework, in which late-time acceleration emerges from entropy production associated with the cosmological horizon, and compare its performance with the standard ΛCDM description of the Universe. We first confront GREA with current background observations, including baryon acoustic oscillations, type Ia supernovae, compressed CMB information, and cosmic chronometers, with particular emphasis on the geometric horizon parameter −kη0. We then introduce a phenomenological extension of the theory by allowing for an additional dark energy component, Ωde, enabling the recovery of a ΛCDM-like expansion history as a limiting case. We perform a Bayesian parameter inference and model comparison analysis using both current data and mock datasets representative of future surveys, including SKAO, LSST, and ET. While current data statistically prefer ΛCDM when compressed CMB information is included, GREA remains competitive for low-redshift combinations. Forecasts indicate that gravitational wave standard sirens are expected to enhance the ability to discriminate between entropic-driven and dark-energy-driven expansion scenarios, and to identify the underlying cosmological model favored by the data.

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GREA模型膨胀历史的当前和未来约束　·　本文使用当前和未来模拟数据（BAO、超新星、CMB、宇宙计时器、SKAO、LSST、ET）对GREA模型进行参数推断和模型比较，发现当前数据在包含压缩CMB时偏好ΛCDM，但未来引力波标准警报将增强区分模型的能力。

预印本 2026-03-02 · 刊出 2026-07-10 · 收录 2026-07-22

ADS:2026OJAp....964902G ↗arXiv:2603.01934 ↗DOI ↗

优先级 509-14 补录

The LBT Yp Project. V. Cosmological Implications of a New Determination of Primordial 4He

Yeh, Tsung-Han, Olive, Keith A., Fields, Brian D., et al.

原文摘要Abstract

The primordial abundance of 4He plays a central role in Big Bang nucleosynthesis (BBN) and in the cosmic microwave background (CMB). The LBT Yp Project's new measurement of the primordial 4He mass fraction, Yp = 0.2458 ± 0.0013, is the most precise determination to date. In this paper, we combine our new Yp value with the latest primordial deuterium measurement and assess the consequences for cosmology. For standard BBN, where the number of light neutrino species is fixed at Nν = 3, the single free parameter is the cosmic baryon density; the CMB measures this independently, with results consistent with each other. Combining Yp, D/H, BBN, and the CMB gives the cosmic baryon-to-photon ratio η = (6.120 ± 0.038) × 10-10, corresponding to a baryon density parameter ΩBh2 = 0.02236 ± 0.00014. We then allow Nν to vary and thus measure relativistic species present during nucleosynthesis. We find η = (6.101 ± 0.044) × 10-10 or ΩBh2 = 0.02229 ± 0.00016, and Nν = 2.925 ± 0.082, and for Nν >= 3, ∆Nν = Nν - 3 <= 0.125 (95% confidence limit) during BBN and the CMB. Our results demonstrate consistency with the Standard Model of particle physics and the standard cosmology that links BBN at <inline-formula> <mml:math><mml:mo>~</mml:mo><mml:mn>1</mml:mn><mml:mspace></mml:mspace><mml:mi>s</mml:mi></mml:math> </inline-formula> and the CMB at ~400,000 yr.

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LBT Y_p 项目 V：原始4He新测定的宇宙学意义　·　该论文利用最精确的原始4He丰度测量，结合氘丰度、大爆炸核合成和宇宙微波背景，约束了宇宙重子密度与有效中微子种类数，结果与标准模型和标准宇宙学一致。

接收 2026-03-02 · 刊出 2026-09-09 · 收录 2026-09-14

ADS:2026ApJ..1008..241Y ↗arXiv:2601.22239 ↗DOI ↗

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Current and future constraints on the expansion history of the GREA model

The LBT Y<SUB>p</SUB> Project. V. Cosmological Implications of a New Determination of Primordial <SUP>4</SUP>He