Department of Physics

Abstract The HL-3 tokamak program addresses critical challenges in developing integrated high-performance scenarios compatible with power exhaust demands for ITER and future reactors. Through systematic facility enhancements including auxiliary heating upgrades to 19.5 MW and AI-enabled control systems achieving 95.5% disruption avoidance, HL-3 finished a new round of exploration and validation for high-performance operation and power exhaust solution. Experiments at mega-ampere plasma currents demonstrated a reactor-relevant hot-ion regime with core ion temperatures exceeding 10 keV and a fusion triple product of . High normalized beta scenarios featuring internal and double transport barriers were successfully established. To address the compatibility of the plasma boundary, various small- or no-edge localized mode (ELM) regimes were achieved, including the enhanced D-alpha (EDA) H-mode, quiescent H-mode (QH-mode), and the quasi continuous exhaust (QCE) regime. Investigations into power exhaust integration highlighted the efficacy of advanced divertor configurations, specifically snowflake and tripod geometries, in significantly reducing peak heat fluxes. Active ELM control was demonstrated via resonant magnetic perturbations (RMPs), lower hybrid waves (LHW), and impurity supersonic molecular beam injection (SMBI), complemented by real-time feedback control of divertor detachment. These developments establish the fundamental physics basis and technical foundations necessary for demonstrating and extrapolating high-performance operations to ITER and next-step devices.

A recent study demonstrates that the suppression of ion temperature gradient (ITG) modes can occur during the nonlinear evolution of toroidicity-induced Alfvén eigenmodes (TAEs) in the DIII-D tokamak [Du et al., Phys. Rev. Lett. 135, 265101 (2025)]. In that work, ITG was suppressed by the formation of a narrow, TAE-induced shear flow layer, whose shearing rate exceeded the ITG decorrelation rate. The shear flow arises from an imbalance between Reynolds and Maxwell stress forces, as the TAE departs from the conventional shear Alfvén wave polarization. This follow-up paper systematically identifies the plasma conditions required for robust ITG suppression through a series of comparative experiments. The results show that TAEs routinely suppress ITG turbulence in plasmas with higher local safety factor (q), elevated fast-ion beta, and larger populations of fast ions on passing orbits, i.e., conditions consistent with the substantial TAE drive. Database analysis further reveals the existence of a threshold in TAE drive for ITG suppression. That is, once the drive exceeds a critical value within a favorable q window, the system undergoes the nonlinear bifurcation process, characterized by a sharp increase in TAE saturated amplitudes at a nearly fixed fast ion drive, suppression of ITG turbulence, and the formation of an internal thermal transport barrier at the localized radii.

This paper presents solutions to Einstein’s equation, and the numerical methods used to construct them, that describe simple cosmological models on manifolds with compact nonorientable spatial slices. These solutions have been constructed on a selection of manifolds having positive, negative, and vanishing spatial scalar curvatures. One example is shown to be indistinguishable locally from a homogeneous Friedman cosmological model, and others are constructed with significant inhomogeneities. Together, these examples are used to explore the strengths and limitations of the numerical methods used in this study, and to test the code used to implement them.

Strong magnetic fields and anisotropic stresses can substantially modify the structure and observable properties of compact stars. In this review, we present a unified treatment of magnetically induced anisotropy across neutron stars, hybrid stars, and white dwarfs, connecting the microphysical equation of state effects to macroscopic structure and multimessenger observables. We demonstrate that magnetic-field geometry plays a decisive role: toroidally oriented (transverse) fields enhance the maximum mass by providing additional perpendicular pressure support, whereas radially oriented fields primarily increase central compression with comparatively small mass gain. In neutron stars, anisotropy and magnetic stresses can shift phase-transition thresholds in hybrid models and enable configurations in the lower mass gap with significantly smaller magnetic energy compared to the gravitational binding energy. We further show that continuous gravitational wave emission from magnetically deformed neutron stars provides a complementary probe of internal field geometry through ellipticity-driven strain evolution. In magnetized white dwarfs, super-Chandrasekhar masses arise from the spatial redistribution of magnetic stresses rather than from globally strong magnetic energy. Taken together, these results highlight that magnetic-field geometry and matter anisotropy are as important as field strength in determining mass–radius relations, tidal deformability, gravitational wave detectability, and the emergence of extreme compact-star configurations.

In eukaryotic cells, mitochondria form networks that range from highly fused interconnected structures to fragmented populations of individual organelles that undergo transient interactions. These structures can be described as temporal networks of physical units, whose dynamic topology is determined by fusion, fission, and motion of the mitochondria through intracellular space. The heterogeneity of the mitochondrial population is governed by diffusive transport and interunit exchange of proteins, lipids, ions, and RNA within these networks. We present a unifying framework for the dispersion of material within temporal networks of spatially embedded units that span across a broad connectivity range. Specifically, we consider filling of the networks with a locally produced but globally consumed material, demonstrating that the steady-state content is determined by the balance of timescales for spatial encounter between clusters, local fusion, fission, and diffusive transport within a cluster. As the connectivity increases, filling behavior transitions from three-dimensional spread through a "social network" limited by cluster interactions to low-dimensional transport through a largely stationary "physical network" limited by material diffusivity. We extract parameters for mitochondrial networks in three human cell lines, demonstrating that different cells can access both the social and the physical network regimes. These results provide a quantitative basis for predicting the homogenization of biomolecules through a mitochondrial population. Our framework unifies a variety of temporal network structures into an overarching theory for transport through populations of interacting and interconnected units.

We develop a general framework for quantum field theory in curved spacetime based on Local Minkowski Coordinates (LMC), which incorporates curvature effects into local Feynman diagrammatics. Gravitational influence enters through a curvature-dependent normalization function B(x), derived from covariant current conservation, and a gravitational phase S(x), obtained via the WKB approximation. These quantities enter through local phase accumulation and observer-dependent normalization of external states, without modifying globally conserved fluxes. As a first application, we analyze the local redshift normalization and phase structure of quantum amplitudes in the vicinity of a Schwarzschild black hole. Within their range of validity, the curvature-dependent factors B(x) and S(x) reproduce the expected gravitational redshift of field amplitudes in general relativity. When amplitudes are propagated to asymptotic infinity and evaluated in a standard global quantum state (such as the Unruh state), the resulting flux is consistent with the standard Hawking result. The framework refines the local WKB structure and clarifies the separation between local normalization effects and globally conserved fluxes.

Magnetoresistance studies of 2D systems are often shaped by the motion of electrons that occupy spatially confined wave functions, such as topological edge modes and disorder-induced bound states. Directly probing how such states form and behave in situ, under applied currents, provides a clear way of connecting microscopic physics to the macroscopic transport response. In this Letter, scanning tunneling potentiometry is used to probe the local, current-induced electrochemical potential of carriers in graphene near circular p-n junctions in an out-of-plane magnetic field ranging from 0 to 1.4 T. These measurements provide detailed information about the motion of carriers at the nanometer scale, revealing how it evolves with increasing field. The electrochemical potential displays distinct patterns, such as dipoles, spirals, and concentric disks in weak, moderate, and high fields, respectively. The size and orientation of these patterns can be used to understand how local carrier dynamics change in different transport regimes as well as to directly extract physical parameters such as the electron mean free path and cyclotron diameter.

We study current flow around a density inhomogeneity in a two-dimensional electron gas in the presence of a strong magnetic field. The inhomogeneity is parametrized by a power-law tail with an exponent β>2. We show that current and electrochemical potential are exponentially suppressed inside a surrounding area much larger than the geometric size of the perturbation. The corresponding “no-go” radius grows as a certain power of the magnetic field. Residual current and potential exhibit spiraling patterns inside the no-go region. Outside of it, they acquire corrections inversely proportional to the distance, which is known as the Landauer resistivity dipole. The Landauer dipole is rotated by the angle π(1−1/β) with respect to the average electric field. The rotation direction depends on whether the local density is raised or lowered. We also consider the effect of electron viscosity and show that the variation of the no-go radius with magnetic field becomes more rapid if viscosity is large enough. The Landauer dipole size is set by the Gurzhi length, which is much larger than the no-go radius, which is in turn much larger than the geometric size of the perturbation. Our results may be useful for interpreting nanoimaging of current distribution in graphene and other two-dimensional systems.

There is an ongoing discussion in the literature on the nature of long-period transients (LPTs), radio-emitting sources with periods ranging from hundreds to tens of thousands of seconds. Although some of these objects have been identified as white dwarf (WD) + M-dwarf binaries, this description currently does not fit the entire class. An example is GLEAM-X J162759.5-523504.3 (hereafter GLEAM-X J1627-5235), with a period of 1091 s, for which the lack of an optical counterpart disfavors the presence of such a binary system. In this case, GLEAM-X J1627-5235 could be interpreted as an isolated, massive, fast-rotating, and highly magnetized ( ∼ 109 G) WD pulsar. Its properties are consistent with a carbon–oxygen WD of mass  ∼ 1.3 M⊙ and radius  ∼ 2500 km, possibly supported by small-scale multipolar magnetosphere structures that keep it above the death line for WD-pulsars. We assess a double WD merger origin, modeling the post-merger rotational evolution under accretion, propeller, and magnetic braking torques. We find rotational age of  ∼ 572 Myr for GLEAM-X J1627-5235, i.e., the post-merger time required to reach its observed period. This result is consistent with current optical upper limits for GLEAM-X J1627-5235 and support the WD pulsar interpretation for this source. We also discuss how the same model can apply to other LPTs.