高能暂现源 · 每日文献综述

Primordial Black Holes (PBHs) have emerged as a leading non-particulate candidate for dark matter and a unique cosmological probe, a paradigm shift accelerated by the detection of anomalous binary mergers by the LIGO-Virgo-KAGRA (LVK) collaboration. While the literature is rich with phenomenological constraints, the fundamental quantum and relativistic underpinnings governing PBH genesis and evolution often receive comparatively less emphasis. This review bridges that gap by systematically detailing the physics of PBH formation and their subsequent evolutionary trajectory. We critically examine the hydrodynamic complexity of the early universe, establishing the relativistic thresholds for collapse, the non-linear race against sound in the primordial plasma, and the rigorous mathematical utility of the compaction function. Furthermore, by incorporating the dynamic nature of FLRW backgrounds, higher curvature corrections, and quantum backreaction via the memory burden effect, we challenge the standard Hawking evaporation and show that extreme-curvature environments halt evaporation entirely, leaving Planck-scale relics that evade current extragalactic bounds. Finally, we map the multimessenger observational landscape, highlighting how the imminent search for sub-solar mass inspirals by next-generation gravitational wave observatories—such as the Einstein Telescope and Cosmic Explorer—could yield smoking-gun evidence for the PBH paradigm, ultimately transforming these primordial relics into unparalleled laboratories for high-energy physics.

The Laser Interferometer Space Antenna (LISA) is a space-based gravitational-wave observatory that uses free-falling test masses as inertial references to detect mHz-frequency signals. Interactions between these test masses and galactic or solar energetic particles cause charge buildup and Coulomb forces, a major source of acceleration noise that must be accurately modeled. LISA Pathfinder measurements showed that the Poissonian test-mass charging noise, an important entry in the noise budget, was considerably larger than that in prelaunch simulations, indicating missing physical processes in early models. Emission of low-energy secondary electrons (LEEs) from test-mass and housing surfaces has been proposed as a key mechanism affecting charging and the sensor's electrostatic response. We report a particle accelerator-based experiment that directly tests the LEE hypothesis by measuring proton-induced test-mass charging in a LISA-like Gravitational Reference Sensor geometry as a function of the test-mass electrostatic potential. A flight-representative test mass and the capacitive sensor electrode housing surrounding it are exposed in vacuum to monoenergetic 70─230 MeV proton beams, while test-mass charging currents are measured with femtoampere sensitivity. By varying the test-mass potential by volts during irradiation, we gain sensitivity to eV-scale charge carriers whose transport and collection depend on these fields. The measurements yield stable, reproducible picoampere-level charging currents and a clear dependence of the net charging rate on test-mass potential. This behavior directly supports the role of low-energy secondary electrons in test-mass charging and is consistent with the LEE-based interpretation of LISA Pathfinder data. These are the first controlled laboratory measurements of low-energy electron effects in test-mass charging for a LISA-like sensor and provide a benchmark for validating charging models and charge-management strategies for LISA and future space-based precision interferometry missions.

Near-IR spectra of a homogeneous sample of 15 red giants in the Galactic nuclear star cluster, within 1.5 pc of SgrA*, have been acquired with X-shooter at the Very Large Telescope. From these spectra, line-of-sight radial velocities and chemical abundances of iron, carbon, oxygen, and other alpha and light elements have been derived. By combining radial velocities from this study and proper motions from the literature, we computed the orbits of these stars, finding that they have been confined within 12 pc from SgrA* for their entire lifetime, thus strongly suggesting an in situ formation and evolution. Iron abundances between half and twice solar; approximately solar-scaled values within ±0.1 dex for α-elements, Ti, and V; some enhancement of [Na/Fe], [K/Fe], and [Al/Fe]; and some depletion of [C/Fe] with respect to the solar ratios have been measured. The inferred chemical abundance distributions are consistent with a formation from a gas enriched by type II and type I supernovae (SNe) over a prolonged timescale, closely matching those of the metal-rich populations of the inner bulge field and other complex stellar systems like Terzan 5 and Liller 1.

We present deep Hubble Space Telescope (HST) imaging of one of the nearest ultra-diffuse galaxies (UDGs) outside of the Local Group: F8D1, a satellite of M81 known to be tidally disrupting. UDGs are an enigmatic and diverse population, with evolutionary pathways ranging from tidal processing to bursty feedback and high initial angular momentum. To determine F8D1's evolutionary drivers, we resolve stars in F8D1's central ~1 kpc and in a parallel field ~6 kpc along its major axis to deep photometric limits, reaching below the red clump. We also image eight shallower fields along F8D1's major and minor axes. We calculate the star formation history (SFH) in the two deep fields, finding that while currently quiescent, both regions experienced a substantial burst ~2 Gyr ago and a smaller burst ~500 Myr ago, which likely formed F8D1's nuclear star cluster. In the shallow fields, using the ratio of evolved asymptotic giant branch and red giant branch stars out to ~13 kpc along F8D1's known stellar stream, we confirm that F8D1 was globally star-forming until at least ~2 Gyr ago. We estimate a total progenitor stellar mass, including the stream, of ~1.3 × 10<SUP>8</SUP> M<SUB>⊙</SUB>, with an average [M/H] ~ -0.8. We compare F8D1's properties to those of Local Group galaxies with similar initial stellar mass. We find that F8D1 is consistent with a progenitor star-forming galaxy similar to NGC 6822 that is in the midst of a transition to a Sagittarius-like system. Notably, this evolutionary sequence can be accomplished through tidal processing alone in galaxies that have experienced sufficiently bursty feedback to have created cored profiles.