Astronomische Nachrichten最新文献

A novel approach to cosmic inflation within the framework of a noncommutative Riemannian foliated quantum gravity, built upon a reverse Faddeev–Jackiw symplectic spacetime deformation of the conventional Poisson algebra, is investigated. Friedmann-type dynamical equations, analytically continued to a complex noncommutative framework, incorporate a modified energy-momentum Riemann tensor and a noncommutative matter-energy potential, highlighting the emergence of quantum gravity topological fluctuation effects on the expansion dynamics of the universe. In this realm, the coupling of UV and IR scales plays a central role, providing a natural topological mechanism for inflation and recursal evidence for the generation of relic gravitational waves. These predictions align with a self-consistent description of the transition between the primordial mirror-universe deceleration and present-universe acceleration phases as predicted by the Riemann foliated quantum gravity, offering potential connections to observational cosmology.

Dark matter constitutes approximately $��27�\%�$ of the universe's total matter-energy content, yet its fundamental nature remains unknown. Axions, initially proposed to solve the strong CP problem in quantum chromodynamics (QCD), emerge as leading dark matter candidates due to their attractive theoretical properties and compatibility with observational constraints. This paper explores the theoretical foundations of axions, their interactions with electromagnetic fields, and recent advancements in experimental detection methods. We provide an in-depth analysis of axion models, including the PQWW, KSVZ, DFSZ models, and axion-like particles (ALPs), highlighting their mass ranges, coupling strengths, and experimental implications. The potential for detecting axion dark matter via pulsar observations is also explored, offering a novel avenue to constrain axion parameter spaces. Finally, we discuss ongoing challenges and future research directions in axion physics, underscoring the transformative potential of axion detection for solving the dark matter puzzle and advancing fundamental physics.

The paper first meticulously analyzes the primary mechanisms of neutrino generation within neutron stars, namely the direct Urca process and the modified Urca process, elucidates the computational methods for neutrino radiation rates, including the physical mechanisms of weak interactions, applications of quantum field theory, and complex mathematical integration techniques. Additionally, it comprehensively investigates various critical factors affecting neutron star cooling processes, such as the inhibitory effect of superfluidity and superconductivity on neutrino emission rates, the anisotropic impact of strong magnetic fields on neutrino radiation, the modulating effect of baryon density on neutrino emission rates, and how these factors alter the cooling curves and observational characteristics of neutron stars. Finally, based on the existing research findings, the paper outlines future research directions in the field of neutron star thermal evolution, emphasizing the importance of enhancing the measurement accuracy of neutron star cooling curves, delving into neutrino radiation mechanisms under extreme physical conditions, and exploring potential new physical phenomena within neutron stars, such as quark matter. These studies will not only refine the physical models of neutron stars but also propel the broader field of astrophysics, offering new perspectives and insights into extreme physical conditions and fundamental interactions in the universe.

Solar activity can be witnessed in the form of sunspots and active regions, where the magnetic field is enhanced by up to a factor of 1000 as compared to that of the quiet Sun. In addition, solar activity manifests itself in terms of flares, jets, coronal mass ejections and the production of highly energetic particles. All these processes are governed by the solar magnetic field. Here we study the spatial reach of the influence of the magnetic field of active regions on the photosphere and in the solar corona. An active region is modelled by a magnetic dipole located under the photosphere. This simplified description allows us to study the spatial influence of an active region in the solar atmosphere in a rough but easy way. We find that the area of influence of the magnetic field of an active region on the solar atmosphere increases with both the maximum strength of the magnetic field in the active region and the depth of the dipole under the photosphere. For a typical active region, the magnetic field can be neglected for distances beyond ca. 700 Mm on the photosphere and two solar radii in the solar corona.

We explore a noncommutative extension of branch-cut quantum gravity (BCQG), with a focus on its implications for early-universe inflation. Our framework builds on a three-field mini-superspace model involving a complex-valued cosmic-scale factor, a perfect-fluid field, and an inflaton-type scalar field. Using a Faddeev–Jackiw symplectic deformation of the conventional Poisson algebra, we construct a noncommutative phase space and derive a modified Wheeler–DeWitt equation. Analytic solutions to the wave function of the universe are obtained and analyzed. We show that noncommutativity induces coupling between ultraviolet and infrared modes, naturally leading to an inflationary phase without requiring fine-tuned initial conditions. This feature offers a novel alternative to standard inflationary models. We also discuss how the structure of the wave function in this framework may relate to primordial density perturbations. While some aspects of this theory remain speculative, the mathematical formulation provides a consistent path toward integrating quantum gravitational effects into early cosmological dynamics.