Papers

We address a recent Comment [I. Nikolov et al., arXiv:2608.13579 (2026)] proposing crystalline mosaicity as an alternative explanation for the asymmetric nuclear magnetic resonance (NMR) spectra reported in our study [S. Suetsugu et al., Nat. Phys. 22, 1251–1256 (2026)]. We show that this scenario requires substantial temperature- and site-dependent distributions of crystallographic orientations and additional site-dependent distributions of the electric field gradient (EFG) asymmetry parameter, none of which follow from ordinary crystalline mosaicity. We therefore conclude that crystalline mosaicity cannot account for the observed site-selective spectral asymmetry and does not provide an alternative explanation for the central spectroscopic observation underlying our interpretation.

We construct regular, horizon-admitting compact objects supported entirely by a self-gravitating dark-matter fluid, in the one-parameter curvature-gravity family $f(R)=R+\beta R^n$. Working with the Einasto density profile, we derive the anisotropic fluid field equations for a static, spherically symmetric metric and obtain the exact General Relativity limit under a de~Sitter-type equation of state, in which the central singularity is replaced by a regular de~Sitter core and the solution is either a horizonless droplet or a black hole with one or two Killing horizons, depending on a single rescaled-mass parameter. We compute the resulting Hawking temperature and geodesic effective potential, and – exploiting the linearity of the $\beta=0$ field equation – solve the curvature correction perturbatively in closed form for general $n$, showing that its sign and radial shape are genuinely model-dependent by direct comparison at fixed $\beta$ between $n=2$ (Starobinsky) and $n=3$ (cubic) gravity. We repeat the construction for a non-local equation of state and confirm the resulting droplets are curvature-regular via the Kretschmann scalar. Finally, replacing the Einasto profile with the cored Burkert profile preserves the qualitative regularity mechanism but, because the Burkert halo lacks a finite total mass, produces a horizon structure with inner and outer radii separated by nearly three orders of magnitude – a genuine physical distinction between two comparably realistic dark-matter models.

How many memories can a local learning rule protect, and what fixes the number? Physical learning rules train resistive networks through local measurements, and the standard rules conserve a mass-like function of the conductances, a law whose general form was posed as an open problem with the expectation that no useful solution theory exists. We answer it, in the direction the expectation ran against, and the answer is a capacity theory. The Tellegen identity behind the conserved mass localizes: the feedback state is pinned to zero at the inputs, so every sector of the circuit that the input electrodes separate carries its own private conserved mass, by an argument consuming only Kirchhoff's law and that boundary condition, hence valid for arbitrary nonlinear branch laws. The number of independent sector masses is a topological property of the circuit, bounded by the number of output electrodes. An untrainable element can destroy the mass of its own sector and of no other, which says where fixed nonlinear components may be placed; per-edge learning rates select which functionals are conserved and never how many; and adjoint coupled learning, which clamps its outputs before measuring, drains every output-carrying sector at a rate set by the squared output multipliers. In linear circuits we then classify the identities: exact rational computation over all 502 circuits on up to five vertices with two inputs and one or two outputs, and hundreds of larger ones, yields a closed-form count, proved on that family and conjectured in general, with the sector statement a theorem at every circuit size. The anticipated series-parallel polynomial laws appear as exactly the series-class cubic differences, and the number the opening question asks for is a budget: one designed mass per sector, the differences the topology donates, and one broadcast scalar for each protected functional beyond.

Even for tension-dominated fracture propagation, porous materials may deform plastically adjacent to the propagating fracture. As is common for porous materials, existing phase-field models typically employ a non-associative flow rule for plasticity, and a Helmholtz free energy based on strain and fluid pressure. This work revisits the hydromechanically coupled formulation of the phase-field model for fracture in poro-elastoplastic media by analyzing the strength surface and fracture driving force. Our analyses show that these common choices of flow rule and free energy will lead to a discontinuous strength surface across the tension-compression transition. A non-associative flow rule introduces a jump at the strength surface, while treating fluid pressure-rather than fluid content-as the independent variable in the Helmholtz free energy omits a coupling term from the phase-field driving force, also breaking continuity. Incorporating an associative Drucker-Prager flow rule and this omitted coupling term ensures a continuous strength surface and the accurate fracture driving force. The proposed model exhibits improved accuracy in hydromechanical responses when compared against the analytical solution of the Kristianovich-Geertsma-de Klerk hydraulic fracturing benchmark. Numerical simulations of hydraulic fracturing and biaxial compression in poro-elastoplastic media show that the model can reproduce both shear-dominated fractures induced by mechanical disturbance and tension-dominated fractures driven by fluid injection in saturated porous media.

We derive a channel-resolved Lee-Huang-Yang correction and construct an extended GrossPitaevskii model for one-dimensional polar spin-1 quantum droplets. The fluctuation contribution separates into density and spin channels, which supports self-bound droplets even when the spinindependent mean-field interaction is repulsive. Stationary solutions exhibit a continuous crossover from soliton-like to flat-top droplets, accompanied by saturation of the chemical potential and peak density as the particle number increases. Within the parameter range examined here, linear Bogoliubov analysis together with weak-perturbation dynamics supports the stability of both droplet types. A quadratic-Zeeman quench reveals a finite-size crossover in breathing dynamics and distinct nonequilibrium roles of the density and spin fluctuation channels. Representative head-on collisions further show that the finite-size crossover modulates phase-sensitive nonlinear scattering, with in-phase impact producing coalescence-like central retention and out-of-phase impact favoring quasi-elastic separation. The analysis clarifies how density and spin fluctuations shape equilibrium structure and nonequilibrium response in low-dimensional polar spinor droplets.

We develop a quantum algorithm for solving the dynamics of the nonlinear viscous Burgers equation. We apply the Carleman linearization procedure on the spatially discretized equation, followed by a padding scheme that allows implementation on qubit registers. Existing Carleman-based quantum algorithms commonly formulate the lifted linear differential equation in an oracle model. Here we decompose the padded generator into diagonal masks and reversible arithmetic permutations using the Permutation Matrix Representation (PMR), which we show to be naturally compatible with the Linear Combination of Hamiltonian Simulations (LCHS) algorithm. Under the assumptions required by LCHS - most importantly positive semidefiniteness of the Hermitian part of the linear generator, possibly after a stabilizing shift - the algorithm prepares a normalized quantum state proportional to the solution of the truncated lifted system; the stabilizing shift introduces an exponential postselection overhead, which we quantify and mitigate through a rescaling scheme. We show that our algorithm scales with the off-diagonal norm of the Carleman generator instead of the matrix norm, which can be advantageous for other generators that are diagonally dominant. We also extend the PMR scheme to general fluid equations that may contain higher-order derivatives or nonlinear terms, or may involve multiple fluid variables or spatial dimensions. The construction illustrates how PMR can serve as a convenient Hamiltonian-simulation primitive for a broader class of LCU-based algorithms.

Vacuum ultraviolet photoemission spectroscopies are very information-rich experiments, but due to their surface sensitivity, data are often collected on an initially uncharacterized surface. Traditional raster-grid approaches for locating optimal measurement regions can be time-consuming. In this work, we introduce AARDVARK, a generalizable framework for sample exploration that leverages dimensionality reduction and Gaussian process regression to guide initial sample searches in spatially-resolved photoemission experiments. By utilizing UMAP as a target for a Gaussian process, the algorithm efficiently identifies boundaries of spectroscopically distinct regions, dynamically adapting to variations in sample characteristics. The algorithm enables real-time decision making in measurement selection, optimizes data acquisition, and presents a robust framework for future autonomous sample exploration in photoemission experiments.

We introduce the reader to the continuous posets approach to spacetime geometry, a topic pioneered by Martin and Panangaden (MP), supplying the relevant domain-theoretic proofs to ease the transition for readers from Lorentzian geometry and general relativity. We then present new results for the spacetime interpretation. Identifying the way-below relation with the chronological relation $I$, we determine the unique choice of $\le$ and of causality condition yielding each poset property: continuous posets require $\le\,=D_p$ and “past-distinction, (SC) and future-reflectivity”, bicontinuous posets are causally continuous spacetimes with $\le\,=D$, and globally hyperbolic posets are precisely globally hyperbolic spacetimes with $\le\,=J$, a necessity result beyond MP's sufficiency. Causal simplicity is recovered through a chain realizability condition, stable causality through the Hausdorffness of a topology $\tau$, so the causal ladder is fully determined at the abstract level, solving a problem posed by MP. Being phrased entirely in terms of a poset, the theory is of low regularity. We introduce topological Kronheimer–Penrose causal spaces, general enough to encompass the Lorentzian length spaces in the literature, and give weak conditions making them (bi)continuous posets. Domain-theoretic constructions then apply directly; e.g., Lawson's round-ideal completion, the most natural for preserving continuity, is proved to equal the future GKP completion, as is the directed completion of Gigli et al., for which we remove the (SC) assumption under strong causality. Reversing the logical order of the theory, we characterize the relations that induce a continuous poset having them as way-below relation. Finally, physical considerations on the key role of past-reflectivity in black hole evaporation lead us to suggest that spacetime is, at the fundamental level, a co-continuous poset.

Thermal management underpins essentially every energy technology, from solar harvesters and waste-heat recovery to industrial process heating and electronic cooling. Yet, thermal systems remain limited compared to their electrical and optical counterparts: they lack a direct equivalent of active control elements that enable on-demand pulse generation. As a result, in conventional thermal energy storage architectures, the amount of energy stored and the peak power at which it can be released are both fixed at design time by material properties and heat-exchanger geometry, locking each device to a single operating point in the energy–power plane. This rigidity is incompatible with applications that require short, high-power thermal bursts on demand. Here we show that a counter-flow heat oscillator admits an actively switchable effective thermal quality factor, $Q$, and that modulating $Q$ on sub-dwell-time scales generates transient outlet power exceeding the steady input by more than an order of magnitude. We formalize the system as a dissipative resonant thermal cavity with $Q$ controlled by the balance between advective and conductive transport and environmental losses, and we experimentally demonstrate, in a water-based dual-channel device, $\sim$5-fold transient power amplification through controlled flow detuning, in quantitative agreement with our thermofluidic model. Active $Q$-switching establishes a distinct mode of thermal power management, accessing $\sim$5$\times$ (demonstrated experimentally) to $\sim$40$\times$ (projected numerically) peak-power amplification on continuous input through a single architecture, a regime inaccessible to passive thermal storage and a missing analogue of the active pulse-generation tools long available in optics and electronics.

Light-field microscopy enables snapshot volumetric imaging, but its information rate is constrained by both optical encoding and detector readout architecture. Here we develop a task-dependent Fisher-information framework that evaluates optical encoders relative to the detector resource limiting acquisition throughput. We compare full Fourier light-field microscopy (FLFM), squeezed light-field microscopy (SLIM), and frame-rate-matched FLFM under a common optical geometry, photon budget, and row-limited camera model. Sparse scenes are analyzed using a 3D point-emitter Fisher matrix, and dense scenes using Fourier-mode information on tilted spectral slices. At s=0.25, SLIM provides 2.40x higher axial Fisher information per camera bandwidth and 1.89x higher 3D D-optimal position information than frame-rate-matched FLFM. For dense scenes, it provides 1.85x higher integrated Fourier-mode Fisher information per bandwidth, 4x greater axial-frequency extent, and approximately 11x larger projected lateral hard-support area. Sweeps over compression factor and view tilt show that these advantages reflect a general detector-allocation principle rather than a specific operating point. More broadly, the framework can be adapted to other camera architectures by incorporating architecture-specific measurement models and detector-throughput costs, providing a general basis for co-designing optical encoding, scene statistics, and camera readout.

Nonlinear multiphoton conversion processes are theoretically and experimentally challenging systems in quantum optics and related areas. These phenomena bring remarkable quantum properties and can be of fundamental relevance in quantum information and computation applications. Based on recent experimental advances and the possible uses in generalized three-photon squeezing, we investigate degenerate three-photon parametric down-conversion generated inside a cavity fed by a classical pump. In addition, we consider that the process is stimulated by a coherent driving mode and subjected to dissipation by spontaneous emission of the cavity. A treatment using phase-space methods and stochastic differential equations is applied and the stability conditions of its steady states are found. We find that the system does not exhibit multistability, instead it has a limited parameter region leading to a single stable steady branch, alongside multiple unstable branches. Focusing on the stable steady states and linearizing the dynamics around them, we calculate the spectral densities of the quadrature variables. We identify and characterize the squeezing of three-photon down-conversion. Moreover, since the quasi-probability differential equations of the higher-order multiphoton processes have higher-order derivatives, hindering their mapping into stochastic differential equations, we make use of a positive Wigner function approach to calculate two-dimensional spectral densities associated with three-time correlation functions, with the goal of studying non-Gaussian properties of the system.

We present a catalog of 147 short-period (10.34–106.46~min) blue compact-binary candidates, identified by combining Gaia DR3 astrometry and photometry with ZTF DR23 light curves via a Gaia selection, period searches, and machine-learning morphology ranking. Of these, 111 lack prior compact-binary classifications. Multiwavelength data (DESI DR1, GALEX, AllWISE) reveal a heterogeneous sample: on the Gaia colour–magnitude diagram, 52 sources lie on the white-dwarf locus, 69 in the hot-subdwarf region, and 26 are intermediate. Among 26 sources with DESI spectra, only about one third follow the white-dwarf cooling sequence; the rest are more luminous blue stars with white-dwarf-like low-resolution spectra. We highlight a prioritized subset of new white-dwarf-locus candidates for follow-up, including ten with periods below 40~min and none with existing radial-velocity data. Under fiducial binary assumptions, 17 of these newly identified white-dwarf-locus candidates would exceed the adopted LISA signal-to-noise threshold (led by a 37~pc white dwarf), with the count depending on chirp mass (9 for $0.15\,M_\odot$, 17 for $0.3\,M_\odot$, 21 for $0.6\,M_\odot$), assuming orbital modulation. However, for most of the white-dwarf-locus sample, observed modulation amplitudes exceed any plausible ellipsoidal signal by three to five orders of magnitude, implying that rotating magnetic or chemically inhomogeneous single white dwarfs offer a viable alternative that ZTF photometry alone cannot rule out—the catalog includes at least one confirmed case. We release the full 147-source catalog, including periods, Gaia/spectroscopic classifications, harmonic/ellipsoidal diagnostics, and supplementary tables of fiducial GW estimates and UV–IR photometry.

We establish a general framework for developing fast sampling and counting algorithms for stoquastic spin systems at high temperature. Our framework is based on a rapidly mixing Markov chain for polymer models and a subcritical percolation process for sampling individual polymers. We apply our framework to obtain fast algorithms for approximating the partition function and sampling from the thermal distribution of (1) general stoquastic spin systems, (2) ferromagnetic Heisenberg models, and (3) antiferromagnetic Heisenberg models on bipartite graphs. For the Heisenberg models, we obtain an improved bound on the inverse temperature by using their respective cycle and loop representations.

We argue that the variance of the information content ($C$), an information-theoretic quantity, can be naturally interpreted as a measure of statistical complexity. We show that $C$ satisfies widely accepted criteria for statistical complexity measures: it vanishes for both ordered and equiprobable states, while attaining maxima in intermediate regimes, typically shifted toward order. This interpretation establishes direct connections with thermodynamics and phase transitions: for systems obeying Boltzmann–Gibbs statistics, $C$ is extensive and directly proportional to energy fluctuations and heat capacity. Moreover, unlike other statistical complexity measures, it attains a maximum at continuous phase transitions, as illustrated for the two-dimensional Ising model. Applications to chaotic maps and fractional Gaussian noise further indicate that $C$ captures nontrivial dynamical structure in different classes of correlated systems.

We study the dynamics of the kinetic wave equation associated to the three dimensional Schrödinger equation close to Rayleigh-Jeans equilibria. We first prove that the linearised operator generates a semigroup of contractions in $L^2((0,\infty);\sqrt \omega \dd\omega )$. Considering the family of nonsingular Rayleigh-Jeans spectra, we prove that the linearised operator possesses a spectral gap, despite the non-compactness of the integral collisional operator, and thus obtain an exponential relaxation for the linear semigroup. We then prove bilinear and trilinear estimates in the relevant norm for the nonlinear terms and deduce global well-posedness and exponential relaxation for sufficiently small relative perturbations of Rayleigh-Jeans equilibria. To our knowledge, this is the first global strong well-posedness and asymptotic stability result near a nonzero thermodynamic equilibrium for the full spatially homogeneous four-wave kinetic equation associated with the cubic nonlinear Schrödinger equation.

We study a non-standard cosmology (NSC) scenario within the Unimodular Gravity (UG) framework, sourced by a scalar field $\phi$ that undergoes energy diffusion, parametrized by the diffusion parameter $x$, the initial energy densities rate $\kappa\equiv\rho_\phi/\rho_\gamma|_{\text{ini}}$, and the end-of-domination temperature $T_{\text{end}}$. We compare this UG+NSC scenario with standard NSC and $\Lambda$CDM cosmologies for WIMP Dark Matter (DM) production via the freeze-out mechanism. We find that energy diffusion reshapes the allowed $(m_\chi, \langle\sigma v\rangle)$ parameter space, where $m_\chi$ is the DM mass and $\langle \sigma v \rangle$ is the thermally averaged annihilation cross section, opening regions otherwise excluded by DM overproduction in $\Lambda$CDM, and shifting the mass and cross-section ranges accessible to WIMP candidates depending on $x$, $\kappa$, $T_{\text{end}}$, and the barotropic index $\omega$ of $\phi$. As a concrete application, we implement this framework for the Real Singlet Scalar WIMP and test its $(m_\chi, \lambda_{HS})$ parameter space against current direct detection bounds from the LZ experiment, showing that energy diffusion opens previously unconstrained regions in the Higgs-portal coupling $\lambda_{HS}$ and thereby alters the detectability prospects of this benchmark model in future searches.

The inner filter effect (IFE) transforms the nominally linear fluorescence-concentration relationship into a geometry-dependent and often nonmonotonic response, resulting in reduced sensitivity, concentration ambiguity, and inaccurate underestimation at high optical densities. Here, we introduce a spatially encoded multireceiver fluorometric strategy that does not eliminate or correct the IFE, but instead harnesses the spatial fluorescence attenuation induced by IFE as an additional quantitative encoding dimension. Fluorescence generated along the excitation axis is integrated over independently positioned receiver windows, and concentration is recovered by nonlinear optimization of the joint fluorescent intensity vector. Tryptophan was selected as a biomedically relevant model fluorophore to validate the proposed strategy. Single-window calibration exhibited vanishing-gradient boundary and two-valued concentration inversions, whereas two spatially separated receiver windows restored global identifiability across the full concentration range. Screening of 35 two-receiver geometries identified the minimum-uncertainty configuration, achieving an average 95% error half-width of mean E_95= 0.884 mg/L, and the maximum-sensitivity configuration, reaching a noise-normalized response sensitivity of mean S_N=3.832 a.u./(mg/L). By converting spatial attenuation into a multidimensional concentration coordinate, this approach extends quantitative fluorescence analysis without dilution, a separate absorbance measurement, or piecewise calibration and provides a general metrology framework for fluorescence metrology even under strong IFE conditions.

We propose a spintronic memcapacitance effect based upon altermagnetic multiferroic materials. We identify the rare-earth vanadates RVO$_3$ as a concrete platform, with all key parameters tied to measured properties. Under an oscillating electric field, the resulting charge and spin currents trace pinched hysteresis loops that close tangentially at zero field – the hallmark of memcapacitive, type-2 memdevice behavior – with charge current densities exceeding, by a factor of about 3.6, the lowest deterministic switching current density reported for optimized spin-transfer-torque magnetic tunnel junctions. We model the system theoretically as a dimerized two-orbital $d$-wave altermagnetic lattice via a Su–Schrieffer–Heeger-type bond modulation, in the spirit of the spin-dependent Rice–Mele model, thereby coupling the altermagnetic order to field-switchable charge and spin polarizations. The associated polarization loops close tangentially at zero field and yield a sign-changing, history-dependent “butterfly” differential capacitance, identifying the device as a genuine memcapacitor. Both responses are protected by the same inversion symmetry, so charge and spin channels switch simultaneously with no separate control needed. These results establish altermagnetic multiferroics, realized concretely in RVO$_3$, as an efficient, non-volatile platform for combined electric and spintronic memory.

Picosecond level timing resolution is a prerequisite capability for improved coincidence matching, time-of-flight measurements, and secondary vertex reconstruction. Here, we present the specification, design, and simulation results for a new Application Specific Integrated Circuit (ASIC), called PSEC6, in the TSMC 65nm process. It features 8 channels, a maximum sampling rate of 40 GSa/s, a buffer length of 204.8 nanoseconds, and a 10.24 GHz Phase Locked Loop (PLL), which is the first of its kind in the 65nm CMOS process. The event readout rate is 32 kHz, with the digitization done by an off-chip Analog-to-Digital Converter (ADC). Simulations predict a 4.0 GHz analog input bandwidth and 20 mW per channel during sampling; the 10.24 GHz PLL has a predicted jitter of 550 fs RMS at 15.7 mW. The paper describes the sampling architecture, chip signal paths, PLL design, and presents simulation results.

Paleoclimate archives extend climate knowledge beyond the instrumental era, registering different seasons, variables, time averages, and memory lengths. A longstanding problem is to integrate these heterogeneous sources of information within a unified methodology. Here we present a new data-assimilation framework, Last Millennium Reanalysis 4D-Var (LMR4D-Var), which reconstructs climate trajectories from these heterogeneous datasets while balancing errors in the model, observations, and initial conditions. We compare results using LMR4D-Var to assimilate proxies from PAGES2k, Temp12k, and borehole temperature profiles without treating them as instantaneous equivalents. Instrumental verification shows that LMR4D-Var achieves the highest skill compared with previous reconstructions. Borehole assimilation preserves skill against withheld annually resolved records, increases agreement between reconstructed 300–2000-m ocean heat content and independent estimates, and yields a cooler reconstructed Little Ice Age ocean. Results for Temp12k demonstrate assimilation of decadal-to-millennial records and the potential for Holocene and deeper-time applications with suitable emulators.

We report high-resolution synchrotron X-ray diffraction and X-ray resonant magnetic scattering (XRMS) studies of the low-temperature crystal and magnetic structures of DyCuAs$_2$, a member of the \RE{}CuAs$_2$ family exhibiting a resistivity minimum above the antiferromagnetic transition temperature. Synchrotron diffraction measurements reveal that DyCuAs$_2$ preserves tetragonal symmetry down to low temperature within the experimental resolution, although pronounced anomalies in both lattice parameters $a$ and $c$ are observed near the antiferromagnetic transition temperature, $T_{\mathrm N}\approx7$~K, indicating strong magnetoelastic coupling. XRMS measurements at the Dy $L_3$ edge establish commensurate antiferromagnetic ordering below $T_{\mathrm N}$ with AFM Bragg peaks at \qq{} = (0, 0, 0.5). Representation analysis and calculations of the AFM Bragg peak intensities identify the magnetic structure as the $\Gamma_{10}$ representation, consisting of in-plane Dy moments stacked along the \cc{} axis in a $++--$ sequence. The magnetic structure is therefore identical to that previously reported for SmCuAs$_2$. Comparison among DyCuAs$_2$, SmCuAs$_2$, and GdCuAs$_2$ suggests that in-plane AFM order and the associated magnetic frustration on the tetragonal lattice are closely connected to the emergence of the resistivity minimum in the \RE{}CuAs$_2$ family. At the same time, the enhanced lattice response and stronger magnetic-field sensitivity observed in DyCuAs$_2$ imply that magnetoelastic and spin-orbit interactions additionally play important roles in determining the robustness of this anomalous transport behavior.

At fixed pulse energy, which drive waveform extracts the most $n$th-order nonlinear conversion from a resonator ($n=2$ for second harmonic)? A short pulse couples poorly to a narrow resonance, a long one dilutes its energy, and no linear rule fixes the compromise. We solve the problem exactly for a single mode of amplitude decay rate $\kappa$. Eliminating the drive turns fixed incident energy into a constraint on the stored field alone, and the optimization becomes a sharp Gagliardo–Nirenberg inequality whose extremal is the ground-state soliton of the nonlinear Schrödinger equation. The optimal stored field is $\mathrm{sech}^{1/(n-1)}[(n-1)\kappa t]$, sustained by an asymmetric input that rises as $e^{\kappa t}$ and falls as $e^{-(2n-1)\kappa t}$; the largest converted energy follows in closed form. A rising exponential, the time-reversal recipe, retains at most $79.0\%$ of the bound at $n=2$ and $2/e$ at large $n$; a two-rate pulse retains above $97\%$. Critical coupling generalizes to $n$-fold overcoupling, with optimal input coupling $n$ times the intrinsic loss rate. The bound applies from microrings to superconducting circuits and caps the per-pulse brightness of broadband photon-pair sources.

Partial entanglement may provide enough connections in the universe to satisfy the definition of a small world. To investigate this possibility, we define a network of particles on a given space-like hyper-surface with a long-range link between any two particles that are connected by a chain of exchanged particles involving a limited number of interactions. Considering the mean free paths of particles in different regions of space and the resulting probability distributions of entanglement connections vs. distance, we find evidence of small-world or random network structure on all but the smallest scales - corresponding to stars and planets - on which other types of connections would need to be added to complete the small world picture.

A realist, anti-psi interpretation of quantum field theory is introduced, based on an expanded ontology that was inspired by the renormalization group. A goal will be to work with a classical non-interacting scalar field "toy model" in the canonical ensemble and show that an observer in this expanded ontology, under certain limiting conditions, will see a QFT. The inverse renormalization group (IRG) will be key in both interpreting this expanded ontology and furnishing novel examples of QFTs. This will lead to a definition of Planck's constant that flows as we head towards a fixed point, is expressed in terms of a temperature, and depends on the observer being studied in this expanded ontology. Our hope is that this approach will lead both to insights into quantum foundations and to prescriptions for developing new QFTs.

Direct optimization of complex wave dynamics through the intrinsic evolution of physical systems is fundamentally limited by the lack of directly accessible gradients. Adjoint methods provide an exact route to gradient computation and have enabled optimization in numerical solvers and, more recently, in frequency-domain physical platforms. Yet their extension to the time domain has remained out of reach, as reproducing time-reversed propagation appears to require non-causal operations or compensating gain. Here we develop a protocol and experimentally demonstrate that time-domain adjoint dynamics can be realized in-situ in linear physical systems without gain, non-causal elements, or auxiliary backward networks. By combining time remapping with a transformation of system variables, we obtain a physically realizable adjoint evolution that constructs gradients from measurable signals. We experimentally demonstrate the approach in a complex RLC network, realizing in-situ optimization for time-dependent objectives, including time-windowed and broadband responses. This framework unifies physical optimization by enabling both system parameters and source excitations to be optimized within the same platform. Our results close the gap between adjoint theory and physical implementation, establishing a general foundation for hardware-native, in-situ temporal optimization across a broad class of complex dynamical systems.

Using Helioseismic and Magnetic Imager ring-diagram measurements and building on the rotation-rate $\Omega$ inferences presented in Paper I for depths of 1-17 Mm, we examine the properties of the dimensionless radial shear $\partial\ln\Omega/\partial\ln r$. In the radial range overlapping global-mode analyses, the inferred shear agrees with previous results. The near-surface shear layer exhibits a three-region shear structure with an enhanced-shear middle layer, and the largest residual variations occur in the two shallowest regions not accessible to global-mode analyses. We parameterize the enhanced-shear layer by the depth of maximum shear, its amplitude, and its width, and find all three to be strongly correlated with a magnetic activity index; increasing activity corresponds to a shallower, stronger, and modestly narrower layer, indicating that the flows and magnetic fields are interconnected in these layers. This behavior is consistent with expectations that sufficiently strong toroidal fields can enhance the near-surface rotational shear and with inferences of a near-surface toroidal-field concentration near the radius where we observe the strongest shear. Moreover, the observed strengthening and upward shift of the strong-shear layer toward solar-cycle maximum suggest a corresponding solar-cycle dependence in the location of the strong toroidal field. We also highlight the importance of finite-resolution effects and instrumental calibration in interpreting small variations in the results.

Gravitational wave observatories are large scale laser interferometers which are held on resonance to facilitate the detection of gravitational waves. Achieving this resonant condition is a time consuming process, and in the LIGO gravitational-wave observatories this procedure has a relatively low success rate. This limitation leads to a loss of observation time thereby reducing the number of observable astrophysical events. The primary cause of this problem is the coupling among the longitudinal degrees of freedom of the interferometer, particularly the coupling from the arm cavity lengths to the central degrees of freedom, such as the recycling cavities and the Michelson interferometer. We demonstrate a simpler and faster lock acquisition scheme at the 40-meter prototype interferometer, located at the California Institute of Technology. This scheme is achieved by controlling the arm cavity lengths with high bandwidth during the lock acquisition process. In this paper, we describe how this fast lock acquisition is realized, compare it with the current LIGO lock acquisition method, and discuss how our framework can be implemented in LIGO.

We consider the task of simulating the real-time dynamics of weakly interacting fermionic systems. In particular, we focus on computing the expectation value of a local observable $A$ at time $t$. By analyzing the convergence of the perturbative expansion in the interaction strength $\lambda$ for the Heisenberg-picture observable, we propose a polynomial-time algorithm for estimating this expectation value in the weakly interacting regime $\lambda |t|^{2D+1}=\mathcal{O}(1)$, when the Hamiltonian is geometrically local on a $D$-dimensional lattice. Importantly, this condition is independent of the system size. If the goal is instead to approximate the time-evolved observable in normalized Frobenius norm, we extend the convergence regime to $\lambda |t|=\mathcal{O}(1)$ with quasi-polynomial runtime. When the non-interacting part exhibits Anderson localization, our polynomial-time algorithm can be extended up to $\lambda |t|=\mathcal{O}(1)$, modulo polylogarithmic factors. Our algorithm brings together ideas from continuous-time QMC, diagrammatic QMC, and Majorana Propagation, but with a new Heisenberg-picture operator-growth analysis that makes the sampling complexity rigorously controllable. This leads to provably efficient classical algorithms in regimes where the interaction is weak enough that the sampling variance remains bounded independently of system size. Together, these results identify broad regimes in which weak interactions, locality, and localization can be leveraged to make real-time fermionic dynamics classically tractable.

The application of certain configurations of resonant magnetic perturbations (RMPs) has been shown to cause a plasma pump-out in both L- and H-mode discharges at MAST. In this paper we discuss the impact of neutral fueling on this density reduction. The neutral fueling and average particle confinement time $\tau_p$ of the main ion species were calculated using a 0-D particle balance analysis. When the RMPs were applied, it was found that there was an increase in ionizations and a 15$\%$ reduction in $\tau_p$ for L-mode discharges and a similar result for inter-ELM (edge localized modes) periods of H-mode discharges. A time-dependent global multi-reservoir particle balance (MRPB) was developed, which included atomic and molecular reservoirs, to further investigate the role neutrals had on the density change. We discuss how this model was able to accurately reproduce the experimentally measured density reduction and ionization increase due to either a reduction in $\tau_p$ or a reduction in particle fueling efficiency. Results from EMC3-EIRENE modeling indicate this change could be attributed to neutral particle fueling occurring in locations with now-opened field lines due to the chaotic edge-region from RMP applications.

In this work, an implantation-free ohmic contact technology based on selectively MOCVD-regrown Si-doped n$^+$ layers is demonstrated for enhancement-mode vertical $\beta$-Ga$_2$O$_3$ U-trench MOSFETs. The regrown n$^+$ contact structure eliminates the need for implantation-based ohmic contact formation while maintaining excellent electrical characteristics. A multi-energy nitrogen-ion-implanted current blocking layer (CBL) followed by 1100~$^\circ$C activation annealing in N$_2$ ambient for 30 min was employed to achieve normally-OFF operation. Transmission line model measurements yielded a low specific contact resistivity of $2.65 \times 10^{-7}~\Omega\cdot$cm$^2$. The fabricated devices exhibited a threshold voltage of approximately 5~V, an ON/OFF current ratio of $1.15\times10^{6}$, a peak current density of 158A/cm$^2$, and a specific ON-resistance of 120.9~m$\Omega\cdot$cm$^2$. Three-terminal OFF-state breakdown voltages ranging from 920 to 980~V were achieved at $V_{GS}=0$~V. Multi-finger MOSFETs show current scaling to 0.25 A. These results demonstrate that selectively MOCVD-regrown n$^+$ contact layers provide a promising implantation-free approach for realizing high-performance vertical $\beta$-Ga$_2$O$_3$ power MOSFETs.