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1. Defect absorption and emission for $p$ -atic liquid crystals on cones

   https://doi.org/10.1103/PhysRevE.106.024704  

   Vafa, Farzan; Zhang, Grace H.; Nelson, David R. (August 2022, Physical Review E)

   We investigate the ground-state configurations of two-dimensional liquid crystals with p-fold rotational symmetry (p-atics) on fixed curved surfaces. We focus on the intrinsic geometry and show that isothermal coordinates are particularly convenient as they explicitly encode a geometric contribution to the elastic potential. In the special case of a cone with half-angle β, the apex develops an effective topological charge of −χ, where 2πχ = 2π(1 − sin β) is the deficit angle of the cone, and a topological defect of charge σ behaves as if it had an effective topological charge Qeff = (σ − σ2/2) when interacting with the apex. The effective charge of the apex leads to defect absorption and emission at the cone apex as the deficit angle of the cone is varied. For total topological defect charge 1, e.g., imposed by tangential boundary conditions at the edge, we find that for a disk the ground-state configuration consists of p defects each of charge +1/p lying equally spaced on a concentric ring of radius d = ( p−1 3p−1 ) 1 2p R, where R is the radius of the disk. In the case of a cone with tangential boundary conditions at the base, we find three types of ground-state configurations as a function of cone angle: (i) for sharp cones, all of the +1/p defects are absorbed by the apex; (ii) at intermediate cone angles, some of the +1/p defects are absorbed by the apex and the rest lie equally spaced along a concentric ring on the flank; and (iii) for nearly flat cones, all of the +1/p defects lie equally spaced along a concentric ring on the flank. Here the defect positions and the absorption transitions depend intricately on p and the deficit angle, which we analytically compute. We check these results with numerical simulations for a set of commensurate cone angles and find excellent agreement. 

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2. Higher-order symmetry plane correlations in Pb-Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$

   https://doi.org/10.1103/zx6t-29hf  

   Acharya, S; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; et al (June 2025, Physical Review C)

   The correlations between event-by-event fluctuations of symmetry planes are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5.02\mathrm{TeV}$recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the nonlinear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information—independent of flow amplitudes—their usage in future model developments can further constrain the properties of the strongly interacting matter created in ultrarelativistic heavy-ion collisions. 

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3. Phonon eigenfunctions of inhomogeneous lattices: Can you hear the shape of a cone?

   https://doi.org/10.1103/PhysRevE.104.065005  

   Zhang, Grace H.; Nelson, David R. (December 2021, Physical Review E)

   We study the phonon modes of interacting particles on the surface of a truncated cone resting on a plane subject to gravity, inspired by recent colloidal experiments. We derive the ground-state configuration of the particles under gravitational pressure in the small-cone-angle limit and find an inhomogeneous triangular lattice with spatially varying density but robust local order. The inhomogeneity has striking effects on the normal modes such that an important feature of the cone geometry, namely its apex angle, can be extracted from the lattice excitations. The shape of the cone leads to energy crossings at long wavelengths and frequency-dependent quasilocalization at short wavelengths.We analytically derive the localization domain boundaries of the phonons in the limit of small cone angle and check our results with numerical results for eigenfunctions. 

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4. Strong Evidence for ${}^9\mathrm{N}$ and the Limits of Existence of Atomic Nuclei

   https://doi.org/10.1103/PhysRevLett.131.172501  

   Charity, R J; Wylie, J; Wang, S M; Webb, T B; Brown, K W; Cerizza, G; Chajecki, Z; Elson, J M; Estee, J; Hoff, D_E M; et al (October 2023, Physical Review Letters)

   The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on two of the most exotic proton-rich isotopes where at least one half of their constitute nucleons are unbound. While the ground state of 8C is a resonance, its first excited state lies in the diffuse borderland between nuclear states and fleeting scattering features. Evidence for 9N, with seven protons and two neutrons, is also presented. This extremely proton-rich system represents the first-known example of a ground-state five-proton emitter. The energies of these states are consistent with theoretical predictions of an open-quantum-system approach. 

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5. Electronic structure of Co $3d$ states in the Kitaev material candidate honeycomb cobaltate ${\mathrm{Na}}_3{\mathrm{Co}}_2{\mathrm{SbO}}_6$ probed with x-ray dichroism

   https://doi.org/10.1103/PhysRevB.107.214443  

   van Veenendaal, M.; Poldi, E. H.; Veiga, L. S.; Bencok, P.; Fabbris, G.; Tartaglia, R.; McChesney, J. L.; Freeland, J. W.; Hemley, R. J.; Zheng, H.; et al (June 2023, Physical Review B)

   none (Ed.)

   The recent prediction that honeycomb lattices of Co2+ (3d7) ions could host dominant Kitaev interactions provides an exciting direction for exploration of new routes to stabilizing Kitaev’s quantum spin liquid in real materials. Na3Co2SbO6 has been singled out as a potential material candidate provided that spin and orbital moments couple into a Jeff = 1/2 ground state, and that the relative strength of trigonal crystal field and spin-orbit coupling acting on Co ions can be tailored. Using x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD) experiments, alongside configuration interaction calculations, we confirm the counterintuitive positive sign of the trigonal crystal field acting on Co2+ ions and test the validity of the Jeff = 1/2 description of the electronic ground state. The results lend experimental support to recent theoretical predictions that a compression (elongation) of CoO6 octahedra along (perpendicular to) the trigonal axis would drive this cobaltate toward the Kitaev limit, assuming the Jeff = 1/2 character of the electronic ground state is preserved. 

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