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1. Molecular-Orbital Framework of Two-Electron Processes: Application to Auger and Intermolecular Coulomb Decay.

   https://doi.org/10.26434/chemrxiv-2023-4l9cz  

   Karippara_Jayadev, Nayanthara; Skomorowski, Wojciech; Krylov, Anna I (July 2023, J. Phys. Chem. Lett.)

   States with core vacancies, which are commonly created by absorption of X-ray photons, can decay by a two-electron process in which one electron fills the core hole and the second one is ejected. These processes accompany many X-ray spectroscopies. Depending on the nature of the initial core-hole state and the decay valence-hole states, these processes are called Auger decay, intermolecular Coulomb decay, or electron-transfer-mediated decay. To connect many-body wavefunctions of the initial and final states with molecular orbital picture of the decay, we introduce a concept of natural Auger orbitals (NAOs). NAOs are obtained by two-step singular value decomposition of the two-body Dyson orbitals, reduced quantities that enter the expression of the decay rate in the Feshbach--Fano treatment. NAOs afford chemical insight and interpretation of the high-level ab intio calculations of Auger decay and related two-electron relaxation processes. 

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2. A Physically Based Statistical Model With the Parameterized Topographic Effect for Predicting the Weakening of Tropical Cyclones After Landfall Over China

   https://doi.org/10.1029/2022GL099630  

   Liu, Lu; Wang, Yuqing (September 2022, Geophysical Research Letters)

   Abstract Accurate prediction of tropical cyclone (TC) intensity is important but challenging. In this study, a physically based algebraic decay model for predicting TC weakening after landfall over China is introduced, which assumes the TC weakening rate is proportional to the square of the TC maximum near‐surface wind speed. In this algebraic decay model, a decay parameter including the topographic effect by modifying the surface drag coefficient with the normalized terrain height is determined by minimizing the forecast errors for all landfalling TCs over mainland China during 1980–2020. Results show that the algebraic decay model with topographic effect considered performs better than the commonly used exponential decay model for TCs after landfall over mainland China, especially when TCs move further inland. This new model has a time‐dependent decay parameter along the TC track due to the topographic variation, which is different from the previous exponential decay model. 

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3. On mix-norms and the rate of decay of correlations

   https://doi.org/10.1088/1361-6544/abdbbd  

   Oakley, Bryan W; Thiffeault, Jean-Luc; Doering, Charles R (June 2021, Nonlinearity)

   Abstract Two quantitative notions of mixing are the decay of correlations and the decay of a mix-norm—a negative Sobolev norm—and the intensity of mixing can be measured by the rates of decay of these quantities. From duality, correlations are uniformly dominated by a mix-norm; but can they decay asymptotically faster than the mix-norm? We answer this question by constructing an observable with correlation that comes arbitrarily close to achieving the decay rate of the mix-norm. Therefore the mix-norm is the sharpest rate of decay of correlations in both the uniform sense and the asymptotic sense. Moreover, there exists an observable with correlation that decays at the same rate as the mix-norm if and only if the rate of decay of the mix-norm is achieved by its projection onto low-frequency Fourier modes. In this case, the function being mixed is called q -recurrent ; otherwise it is q - transient . We use this classification to study several examples and raise questions for future investigations. 

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4. How to describe collective decay of uncoupled modes in the input–output formalism

   https://doi.org/10.1364/JOSAB.468251  

   Propp, Tzula_B (November 2022, Journal of the Optical Society of America B)

   We extend the input–output formalism to study the behavior of uncoupled discrete modes (bosonic cavity modes and fermionic qubits) when they decay to the same Markovian continuum. When the continuum interacts with only a single mode, this decay is irreversible. However, when multiple modes decay to the same Markovian continuum they develop correlations and decay collectively. In the input–output formalism these correlations manifest in additional terms in the quantum Langevin equation. For two modes, this collective decay can dramatically extend the lifetimes of both modes (Dicke subradiance) and, within the single-mode subsystem, induces non-Markovian memory effects including energy backflow. 

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5. Four-jet event shapes in hadronic Higgs decays

   https://doi.org/10.1007/JHEP03(2024)104  

   Gehrmann-De_Ridder, Aude; Preuss, Christian T; Williams, Ciaran (March 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present next-to-leading order perturbative QCD predictions for four-jet-like event-shape observables in hadronic Higgs decays. To this end, we take into account two Higgs-decay categories: involving either the Yukawa-induced decay to a$${\text{b}}\overline{{\text{b}} }$$pair or the loop-induced decay to two gluons via an effective Higgs-gluon-gluon coupling. We present results for distributions related to the event-shape variables thrust minor, light-hemisphere mass, narrow jet broadening,D-parameter, and Durham four-to-three-jet transition variable. For each of these observables we study the impact of higher-order corrections and compare their size and shape in the two Higgs-decay categories. We find large NLO corrections with a visible shape difference between the two decay modes, leading to a significant shift of the peak in distributions related to the H→gg decay mode. 

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