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1. High resolution X-ray spectra of the time evolution of emission from metastable electronic states of highly charged Ni-like ions

   https://doi.org/10.1140/epjd/s10053-024-00872-0  

   Burke, Timothy; Takacs, Endre; Dipti; Hosier, Adam; O’Neil, Galen; Tan, Joseph; Staiger, Hunter; Naing, Aung; Marler, Joan; Ralchenko, Yuri (June 2024, The European Physical Journal D)

   AbstractMetastable levels of highly charged ions that can only decay via highly forbidden transitions can have a significant effect on the properties of high temperature plasmas. For example, the highly forbidden 3d$$^{10}$$ $_{}^{10}$$$_{J=0}$$ $_{J=0}^{}$- 3d$$^9$$ $_{}^9$4 s$$(\frac{5}{2},\frac{1}{2})_{J=3}$$ ${(\frac{5}{2},\frac{1}{2})}_{J=3}$magnetic octupole (M3) transition in nickel-like ions can result in a large metastable population of its upper level which can then be ionized by electrons of energies below the ground state ionization potential. We present a method to study metastable electronic states in highly charged ions that decay by x-ray emission in electron beam ion traps (EBIT). The time evolution of the emission intensity can be used to study the parameters of ionization balance dynamics and the lifetime of metastable states. The temporal and energy resolution of a new transition-edge sensor microcalorimeter array enables these studies at the National Institute of Standards and Technology EBIT. Graphical abstractNOMAD calculated time evolution of the ratio of the Ni-like and Co-like lines in Nd at varying electron densities compared with measured ratios 

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2. Stability and chaos in dynamical last passage percolation

   https://doi.org/10.1090/cams/35  

   Ganguly, Shirshendu; Hammond, Alan (June 2024, Communications of the American Mathematical Society)

   Many complex disordered systems in statistical mechanics are characterized by intricate energy landscapes. The ground state, the configuration with lowest energy, lies at the base of the deepest valley. In important examples, such as Gaussian polymers and spin glass models, the landscape has many valleys and the abundance of near-ground states (at the base of valleys) indicates the phenomenon ofchaos, under which the ground state alters profoundly when the disorder of the model is slightly perturbed. In this article, we compute the critical exponent that governs the onset of chaos in a dynamic manifestation of a canonical model in the Kardar-Parisi-Zhang [KPZ] universality class, Brownian last passage percolation [LPP]. In this model in its static form, semidiscrete polymers advance through Brownian noise, their energy given by the integral of the white noise encountered along their journey. A ground state is ageodesic, of extremal energy given its endpoints. We perturb Brownian LPP by evolving the disorder under an Ornstein-Uhlenbeck flow. We prove that, for polymers of length $n$, a sharp phase transition marking the onset of chaos is witnessed at the critical time $n^{-<\#comment/>1/3}$. Indeed, the overlap between the geodesics at times zero and $t>0$that travel a given distance of order $n$will be shown to be of order $n$when $t\ll <\#comment/>n^{-<\#comment/>1/3}$; and to be of smaller order when $t\gg <\#comment/>n^{-<\#comment/>1/3}$. We expect this exponent to be universal across a wide range of interface models. The present work thus sheds light on the dynamical aspect of the KPZ class; it builds on several recent advances. These include Chatterjee’s harmonic analytic theory [Superconcentration and related topics, Springer, Cham, 2014] of equivalence ofsuperconcentrationandchaosin Gaussian spaces; a refined understanding of the static landscape geometry of Brownian LPP developed in the companion paper (see S. Ganguly and A. Hammond [Electron. J. Probab. 28 (2023), 80 pp.]); and, underlying the latter, strong comparison estimates of the geodesic energy profile to Brownian motion (see J. Calvert, A. Hammond, and M. Hegde [Astérisque 441 (2023), pp. v+119]). 

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3. High-pressure induced Weyl semimetal phase in 2D Tellurium

   https://doi.org/10.1038/s42005-023-01460-1  

   Niu, Chang; Zhang, Zhuocheng; Graf, David; Lee, Seungjun; Wang, Mingyi; Wu, Wenzhuo; Low, Tony; Ye, Peide D. (November 2023, Communications Physics)

   Abstract Relativistic Weyl fermion quasiparticles in Weyl semimetal bring the electron’s chirality degree of freedom into the electrical transport and give rise to exotic phenomena. A topological phase transition from a topological trivial phase to a topological non-trivial phase offers a route to control electronic devices through its topological properties. Here, we report the Weyl semimetal phase in hydrothermally grown two-dimensional Tellurium (2D Te) induced by high hydrostatic pressure (up to 2.47 GPa). The unique chiral crystal structure gives rise to chiral fermions with different topological chiral charges ($${{C}}=-{{1}},+{{1}},{{and}}-{{2}}$$ $C=-1,+1,and-2$). The highly tunable chemical potential in 2D Te provides comprehensive information for understanding the pressure-dependent electron band structure. The pressure-induced insulator-to-metal transition, two-carrier transport, and the non-trivial π Berry phase shift in quantum oscillations are observed in the 2D Te Weyl semimetal phase. Our work demonstrates the pressure-induced bandgap closing in the inversion asymmetric narrow bandgap semiconductor 2D Te. 

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4. The half-volume spectrum of a manifold

   https://doi.org/10.1007/s00526-025-02949-z  

   Mazurowski, Liam; Zhou, Xin (May 2025, Calculus of Variations and Partial Differential Equations)

   Abstract We define the half-volume spectrum$$\{{\tilde{\omega }_p\}_{p\in \mathbb {N}}}$$ $\{{\tilde{\omega }}_p{\}}_{p\in N}$of a closed manifold$$(M^{n+1},g)$$ $(M^{n+1},g)$. This is analogous to the usual volume spectrum ofM, except that we restrict top-sweepouts whose slices each enclose half the volume ofM. We prove that the Weyl law continues to hold for the half-volume spectrum. We define an analogous half-volume spectrum$$\tilde{c}(p)$$ $\tilde{c}\left(p\right)$in the phase transition setting. Moreover, for$$3 \le n+1 \le 7$$ $3\le n+1\le 7$, we use the Allen–Cahn min-max theory to show that each$$\tilde{c}(p)$$ $\tilde{c}\left(p\right)$is achieved by a constant mean curvature surface enclosing half the volume ofMplus a (possibly empty) collection of minimal surfaces with even multiplicities. 

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5. Asymptotic normalization coefficients for $\alpha +{}^{12}\mathrm{C}$ synthesis and the $S$ factor for ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ radiative capture

   https://doi.org/10.1103/PhysRevC.110.055803  

   Mukhamedzhanov, A M; deBoer, R J; Irgaziev, B F; Blokhintsev, L D; Kadyrov, A S; Savin, D A (November 2024, Physical Review C)

   : The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$reaction, determining the survival of carbon in red giants, is of interest for nuclear reaction theory and nuclear astrophysics. A specific feature of the ${}^{16}\mathrm{O}$nuclear structure is the presence of two subthreshold bound states, (6.92 MeV, $2^{+}$) and (7.12 MeV, $1^{-}$), that dominate the behavior of the low-energy $S$factor. The strength of these subthreshold states is determined by their asymptotic normalization coefficients (ANCs), which need to be known with high accuracy. : The objective of this research is to examine how the subthreshold and ground-state ANCs impact the low-energy $S$factor, especially at the key astrophysical energy of $300\mathrm{keV}$. The $S$factors are calculated within the framework of the $R$-matrix method using the code. Our total $S$factor takes into account the $E1$and $E2$transitions to the ground state of ${}^{16}\mathrm{O}$including the interference of the subthreshold and higher resonances, which also interfere with the corresponding direct captures, and cascade radiative captures to the ground state of ${}^{16}\mathrm{O}$through four subthreshold states: $0_2^{+},3^{-},2^{+}$, and $1^{-}$. To evaluate the impact of subthreshold ANCs on the low-energy $S$factor, we employ two sets of the ANCs. The first selection, which offers higher ANC values, is attained through the extrapolation process [Blokhintsev , ]. The set with low ANC values was employed by deBoer []. A detailed comparison of the $S$factors at the most effective astrophysical energy of 300 keV is provided, along with an investigation into how the ground-state ANC affects this $S$factor. : The contribution to the total $E1$and $E2S$factors from the corresponding subthreshold resonances at $300\mathrm{keV}$are $(71–74)\%$and $(102–103)\%$, respectively. The correlation of the uncertainties of the subthreshold ANCs with the $E1$and $E2S\left(300\mathrm{keV}\right)$factors is found. The $E1$transition of the subthreshold resonance $1^{-}$does not depend on the ground-state ANC but interferes constructively with a broad $(9.585\mathrm{MeV};1^{-})$resonance giving (for the present subthreshold ANC) an additional $26\%$contribution to the total $E1S\left(300\mathrm{keV}\right)$factor. Interference of the $E2$transition through the subthreshold resonance $2^{+}$with direct capture is almost negligible for small ground-state ANC of $58{\mathrm{fm}}^{-1/2}$. However, its interference with direct capture for higher ground-state ANC of $337{\mathrm{fm}}^{-1/2}$is significant and destructive, contributing $-27\%$. The low-energy $S_{E2}\left(300\mathrm{keV}\right)$factor experiences a smaller increase when both subthfreshold and the ground-state ANCs rise together due to their anticorrelation, compared to when only the subthreshold ANCs increase. Published by the American Physical Society2024 

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