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Reaction rate determination is an essential problem in the theories of cosmological and stellar nucleosynthesis. I investigate the closed-form analytic evaluation of thermonuclear reaction rates, which are necessary for both cosmic and celestial nucleosynthesis. An alternate velocity distribution to the Maxwell-Boltzmann distribution can be considered in nuclear fusion processes occurring in the interior of stars when there is a diversion from hydrostatic equilibrium. The extension of non-resonant reaction rate integrals in standard, cut-off, depletion, and screening instances is examined in this study, utilising the MacDonald distribution. This study is primarily on the use of generalized special functions that represent the extended non-resonant thermonuclear functions in mathematical physics. Moreover, an attempt is made to analyse the reaction probability integrals corresponding to the several forms of the slowly varying cross-section factor S(E).

Solar wind is a complex network of distinct magnetic flux tubes, each contained and separated by a current sheet. In this study, more than 50,000 current sheets in the solar wind are identified and characterized for the first time, using multi-point Cluster observations during solar minimum and maximum intervals. Flux tubes at Earth are found to have an average diameter of ∼1.5 Earth radii, nearly 45 times smaller than previously reported. Furthermore, 6 years of NASA's ACE solar wind observations at Sun-Earth Lagrange point L1 is used to show that only 30% of the observed flux tubes would directly impact the Earth's magnetosphere. It is shown that flying closer to the Sun-Earth line could help to improve the prediction accuracy of space weather monitors at L1 by up to 2.5 times.

In contrast to potential-driven warm inflation models, this paper presents a new inflationary scenario driven purely by noncanonical kinetic terms. We derive the evolution equations and the associated slow-roll approximations specific to the kinetic case. The model incorporates a nonminimal derivative coupling that enhances gravitational friction; when combined with thermal damping, this leads to a significantly slower evolution of the pure kinetic inflaton. The resulting slow-roll approximations differ fundamentally from those of potential-driven inflation. The attractor behavior of this warm $k$-inflation with nonminimal derivative coupling is explored, confirming that slow-roll solutions can approach a strict exponential expansion attractor under relaxed slow-roll conditions. We further calculate the density fluctuation equations and obtain analytic expressions for the power spectrum, spectral index, and tensor-to-scalar ratio. Compared to standard inflation in general relativity, the energy scale at horizon crossing is lower, and the tensor-to-scalar ratio is significantly reduced due to the combined effects of thermal damping and nonminimal derivative coupling. The field excursion remains comfortably sub-Planckian. The model's predictions are in excellent agreement with the latest Planck 2018 data, offering a novel and successful extension of the warm inflation paradigm.

We study the structure and evolution of the Galactic bar's resonant phase space in self-consistent N-body simulations of the Milky Way, with and without perturbations from the Sagittarius dwarf galaxy. In an idealized disk evolution model in which stars are perturbed solely by a bar that spins down due to dynamical friction against the dark matter halo, it is predicted that stars trapped in the bar's corotation resonance form a characteristic "tree-ring" structure in phase space: as the resonance expands in volume while sweeping outwards, it sequentially captures surrounding stars at its surface, such that stars captured earlier in the inner disk are found preferentially near the core of the resonance. However, it has not been clear whether such a structure persists in a more realistic galactic disk subject to a variety of time-dependent perturbations, in particular those by spiral arms and passing satellite galaxies. This paper demonstrates that the predicted tree-ring structure indeed emerges in a realistic noisy environment using self-consistent N-body simulations. Despite the presence of spiral arms, encounters with the Sagittarius dwarf galaxy, as well as fluctuations in the bar's pattern speed, and not least numerical noise—all of which drive stellar diffusion in phase space—, the tree-ring structure remains well-preserved in the slow angle-action space. Our results demonstrate that the tree-ring structure of the bar's resonance is a robust signal of the bar's spin down, and hence its discovery in the Milky Way implies the existence of a dark matter halo that removed angular momentum from the bar.