高能暂现源 · 每日文献综述

Quantum backreaction effects may quench Hawking evaporation through a "memory burden," allowing primordial black holes (PBHs) with formation masses well below <inline-formula><mml:math><mml:msup><mml:mn>10</mml:mn><mml:mn>15</mml:mn></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>g</mml:mi></mml:math></inline-formula> to survive to the present and contribute to the dark matter. We show that ultrahigh-energy cosmic rays (UHECRs) provide a powerful and previously unexplored probe of this scenario. We compute the proton and neutron emission from memory-burdened PBHs, including the Galactic-halo contribution and the extragalactic proton component, and confront it with the Pierre Auger Observatory proton spectrum and its EeV neutron limits from the Galactic plane. This yields new constraints on the PBH dark-matter fraction as a function of the PBH formation mass and the evaporation-suppression parameter <inline-formula><mml:math><mml:mi>k</mml:mi></mml:math></inline-formula>. For <inline-formula><mml:math><mml:mi>k</mml:mi><mml:mo>≳</mml:mo><mml:mn>3</mml:mn></mml:math></inline-formula> the nonobservation of ultrahigh-energy protons leads to bounds competitive with those from UHE gamma rays, while neutron limits remain comparable to high-energy neutrino constraints. Our results highlights the key role of multimessenger astronomy in constraining beyond-the-standard-model scenarios.

We investigate primordial non-Gaussianity in the inflation without an inflaton framework, where scalar perturbations are generated at second order by primordial gravitational waves in Einstein gravity on an exact de Sitter background. Since scalar modes are produced nonlinearly from tensor modes, non-Gaussianity is an intrinsic prediction of the mechanism. We compute the corresponding scalar bispectrum, derive the relevant contribution to the three-point function of the scalar potential, and evaluate its shape numerically. Similar to the scalar power spectrum, we find that the bispectrum depends on the number of observed e-folds <inline-formula><mml:math><mml:msub><mml:mi>N</mml:mi><mml:mrow><mml:mi>obs</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> through the ultraviolet cutoff. We show that the bispectrum shape is enhanced toward squeezed configurations, but its amplitude becomes strongly suppressed once the scalar power spectrum is normalized to the observed value. The resulting non-Gaussianity at cosmic microwave background scales is therefore negligibly small, well below present observational sensitivity.

We present py5vec, a Python package for implementing and extending the 5-vector method, used to search for continuous gravitational wave (CW) signals. We also provide a comprehensive theoretical review of the 5-vector method and extend the relative likelihood formalism by marginalizing over the noise variance, resulting in a more robust Student's <inline-formula> <mml:math><mml:mrow><mml:mi>t</mml:mi></mml:mrow></mml:math></inline-formula>-likelihood, and over the initial phase to account for pulsar glitches. py5vec provides a modular architecture that separates data representation, signal demodulation, and statistical inference into independent abstract stages. It supports multiple input data formats and interoperates with existing Python software, providing a bridge between different statistical approaches and data processing pipelines. For example, using a bilby-based interface, py5vec implements Bayesian parameter estimation within the 5-vector formalism for the first time. The modular design also allows for making exact multi-level and direct comparisons between other software, such as cwinpy and SNAG in MATLAB. In py5vec, we implement a multidetector targeted search for known pulsars, validated using LIGO data from the O4a run and hardware injections, demonstrating consistent reconstruction of signal parameters. This package therefore provides a flexible platform for current targeted searches and for future extensions to other CW search strategies.

The Einstein telescope (ET) is a third-generation underground gravitational-wave observatory designed to extend the detection sensitivity down to a few Hertz. Newtonian noise is expected to limit the low-frequency sensitivity of ET, particularly in the 3─15 Hz band. Most existing estimates rely on analytical or semi-analytical models assuming homogeneous or layered media, neglecting geological heterogeneity and complex wave interactions. In this work, we present a numerical framework for Newtonian-noise estimation based on spectral-element simulations of a seismic wave field. As a proof of concept, we first benchmark the numerical results against analytical plane-wave predictions in a two-dimensional homogeneous medium with a single surface source, demonstrating excellent agreement for both bulk and cavern contributions. We then extend the model to an array of 30 stochastic surface sources to approximate stationary ambient seismic excitation. The P-wave fraction inferred from the simulated wave field is, in this simple homogeneous case, significantly lower than commonly assumed, indicating enhanced prospects for Newtonian-noise mitigation. The framework is readily applicable to three-dimensional simulations and to integration of detailed local seismic models and topography, offering strong potential for site-specific Newtonian-noise estimation.

The large-distance approximation of a sandwich gravitational wave by a continuous but not necessarily smooth profile provides us with an approximate analytic description of particle motion in a gravitational wave as spelled out for the Pöschl-Teller profile. Displacement Memory is obtained by fine-tuning the amplitude. The role of the 2nd solution of the Sturm-Liouville equation is highlighted. Similar results hold for a Gaussian and simple square profiles. Our approximate models are consistent with Carroll symmetry.