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1. Multimessenger emission from tidal waves in neutron star oceans

   https://doi.org/10.1093/mnras/stad389  

   Sullivan, Andrew G.; Alves, Lucas M. B.; Spence, Georgina O.; Leite, Isabella P.; Veske, Doğa; Bartos, Imre; Márka, Zsuzsa; Márka, Szabolcs (February 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Neutron stars in astrophysical binary systems represent exciting sources for multimessenger astrophysics. A potential source of electromagnetic transients from compact binary systems is the neutron star ocean, the external fluid layer encasing a neutron star. We present a groundwork study into tidal waves in neutron star oceans and their consequences. Specifically, we investigate how oscillation modes in neutron star oceans can be tidally excited during compact binary inspirals and parabolic encounters. We find that neutron star oceans can sustain tidal waves with frequencies between 0.01 and 20 Hz. Our results suggest that tidally resonant neutron star ocean waves may serve as a never-before studied source of precursor electromagnetic emission prior to neutron star–black hole and binary neutron star mergers. If accompanied by electromagnetic flares, tidally resonant neutron star ocean waves, whose energy budget can reach 1046 erg, may serve as early warning signs (≳1 min before merger) for compact binary mergers. Similarly, excited ocean tidal waves will coincide with neutron star parabolic encounters. Depending on the neutron star ocean model and a flare emission scenario, tidally resonant ocean flares may be detectable by Fermi and Nuclear Spectroscopic Telescope Array (NuSTAR) out to ≳100 Mpc with detection rates as high as ∼7 yr−1 for binary neutron stars and ∼0.6 yr−1 for neutron star–black hole binaries. Observations of emission from neutron star ocean tidal waves along with gravitational waves will provide insight into the equation of state at the neutron star surface, the composition of neutron star oceans and crusts, and neutron star geophysics. 

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2. Recent advancements in neutron scattering techniques for quantifying the structure and dynamics of polymers

   https://doi.org/10.1016/j.progpolymsci.2025.102041  

   Cao, Zhiqiang; Wang, Yunfei; Gu, Xiaodan (December 2025, Progress in Polymer Science)

   Neutron scattering techniques are powerful tools for characterizing the structure and dynamics of materials. They are particularly well-suited for studying polymer systems, which are typically rich in hydrogen. By combining neutron scattering with deuterium labeling, researchers can unravel complex structural features and dynamic behaviors within these systems. This review highlights recent advances in neutron scattering methods for probing the hierarchical structures and dynamics of polymeric materials, with a focus on developments over the past decade. We begin by discussing elastic techniques—such as small-angle neutron scattering (SANS)—used to examine polymer organization in both solution and solid states. Subsequently, we addressed the application of neutron reflectometry (NR) and grazing-incidence neutron scattering (GINS) techniques to the study of polymer thin-film structures. Next, we explore inelastic and quasi-elastic techniques, including inelastic neutron scattering (INS), quasi-elastic neutron scattering (QENS), and neutron spin echo (NSE), which provide insight into polymer dynamics across a broad range of time and length scales. Finally, we consider future directions for neutron scattering in soft matter research, emphasizing emerging methodologies and next-generation neutron sources that promise to further advance our understanding of these complex systems. 

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3. Neutron Star Radii, Deformabilities, and Moments of Inertia from Experimental and Ab Initio Theory Constraints of the 208Pb Neutron Skin Thickness

   https://doi.org/10.3390/galaxies10050099  

   Lim, Yeunhwan; Holt, Jeremy W. (October 2022, Galaxies)

   Recent experimental and ab initio theory investigations of the 208Pb neutron skin thickness have the potential to inform the neutron star equation of state. In particular, the strong correlation between the 208Pb neutron skin thickness and the pressure of neutron matter at normal nuclear densities leads to modified predictions for the radii, tidal deformabilities, and moments of inertia of typical 1.4M⊙ neutron stars. In the present work, we study the relative impact of these recent analyses of the 208Pb neutron skin thickness on bulk properties of neutron stars within a Bayesian statistical analysis. Two models for the equation of state prior are employed in order to highlight the role of the highly uncertain high-density equation of state. From our combined Bayesian analysis of nuclear theory, nuclear experiment, and observational constraints on the dense matter equation of state, we find at the 90% credibility level R1.4=12.36−0.73+0.38 km for the radius of a 1.4M⊙ neutron star, R2.0=11.96−0.71+0.94 km for the radius of a 2.0M⊙ neutron star, Λ1.4=440−144+103 for the tidal deformability of a 1.4M⊙ neutron star, and I1.338=1.425−0.146+0.074×1045gcm2 for the moment of inertia of PSR J0737-3039A whose mass is 1.338M⊙. 

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4. Sagnac-type neutron displacement-noise-free interferometeric gravitational-wave detector

   https://doi.org/10.1088/1361-6382/ad42fa  

   Kawasaki, Yuki; Iwaguchi, Shoki; Ishikawa, Tomohiro; Nishizawa, Atsushi; Kitaguchi, Masaaki; Yamagata, Yutaka; Chen, Yanbei; Wu, Bin; Shimizu, Ryuma; Umemura, Kurumi; et al (May 2024, Classical and Quantum Gravity)

   Abstract The detection of low-frequency gravitational waves on Earth requires the reduction of displacement noise, which dominates the low-frequency band. One method to cancel test mass displacement noise is a neutron displacement-noise-free interferometer (DFI). This paper proposes a new neutron DFI configuration, a Sagnac-type neutron DFI, which uses a Sagnac interferometer in place of the Mach–Zehnder interferometer. We demonstrate that a sensitivity of the Sagnac-type neutron DFI is higher than that of a conventional neutron DFI with the same interferometer scale. This configuration is particularly significant for neutron DFIs with limited space for construction and limited flux from available neutron sources. 

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5. Investigating the weak charge of 48Ca using a dispersive optical model

   https://doi.org/10.1016/j.physletb.2025.139371  

   Calleya, NL; Atkinson, MC; Dickhoff, WH (April 2025, Physics Letters B)

   Balantekin, B (Ed.)

   A new nonlocal dispersive-optical-model analysis has been carried out for neutrons and protons in 48Ca that reproduces the weak-form-factor measurement of CREX. In addition to elastic-scattering angular distributions, total and reaction cross sections, single-particle energies, the neutron and proton numbers, and the charge distribution, the CREX-measured weak form factor has been fit to extract the neutron and proton self-energies both above and below the Fermi energy. The resulting single-particle propagators yield a weak form factor of 𝐹𝑊 =0.125±0.05 and a neutron skin of 𝑅skin =0.152±0.05 fm, in good agreement with CREX. The rearrangement of the neutron distribution to accommodate such a thin neutron skin results in the high-momentum content of the neutrons exceeding that of the protons, in contrast to what is expected from high-energy two-nucleon knockout measurements by the CLAS collaboration and ab initio asymmetric matter calculations. The present analysis also emphasizes the importance of neutron experimental data in constraining weak charge observables necessary for a precise description of neutron densities. Notably, the neutron reaction cross section and further parity-violating experiments weak form factor measurements are essential to generate a unique way to determine the 48Ca neutron distribution in this framework. 

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