Comparison of the measured spectral emission properties of single-crystal Cu(001) and W(111) photocathodes to established photoemission theories reveals evidence for an additional one-photon emission process predominantly affecting electron emission near and below the photoemission threshold. This additional photoemission process is postulated to be due to a momentum-resonant Franck-Condon mechanism mediated by inelastic Umklapp electron scattering. An initial first-principles simulation of this emission process (involving the electron thermal effective mass, the inelastic electron mean free path at the vacuum level, and the number of Fermi surfaces in the metal), when combined with a direct one-step band emission model, is consistent with the measured spectral dependencies of both the quantum efficiency and mean transverse energy of electron photoemission from the two single-crystal metal photocathodes.

Models of unification predict additional $Z^{\prime }$ boson, which contributes to parity nonconservation (PNC) in atoms. If $Z^{\prime }$ boson is light, ratio of $Z^{\prime }$-boson contribution to the standard model $Z$-boson contribution to atomic PNC increases with decreasing nuclear charge $Z$ faster than $1/Z^2$. This motivated our previous study of PNC in hydrogen and deuterium, where $s\text{−}p$ wave mixing induced by the weak interaction was considered. An even more pronounced relative enhancement occurs when higher-angular-momentum states are involved, such as in the $p\text{−}d$ weak matrix elements. A light boson mediates a long-range interaction, in contrast to the effectively contactlike interaction mediated by the standard model $Z$ boson. Consequently, higher-angular-momentum states provide a background-free system: Their suppressed overlap with the nucleus strongly reduces the standard model contribution while leaving the long-range $Z^{\prime }$ contribution unsuppressed.

Nonlinear oscillators are ubiquitous in physics and engineering, yet finding explicit analytical expressions for their amplitude-dependent frequency remains a fundamental challenge. The Duffing equation is the paradigmatic model for this class of problems, and despite decades of progress through perturbative, variational, and homotopic methods, general closed-form frequency relations are unavailable for most of its configurations. In this work, we investigate whether symbolic regression (SR)—a machine-learning technique that searches for interpretable mathematical expressions directly from data—can recover the closed-form amplitude-frequency relations produced by classical methods, and approximate them where no closed form is available. We generate reference datasets using four classical approaches: the Lindstedt-Poincaré method, first-harmonic balance, multiharmonic balance, and numerical integration via a Runge-Kutta 4–5 scheme. We stress at the outset that, for the analytical and semianalytical methods, the training labels are obtained by evaluating the corresponding closed-form expressions; recovering those expressions therefore constitutes symbolic rediscovery of a known formula from sampled data, rather than discovery of new physics. The only genuinely dynamics-based case is the quintic oscillator labeled with Runge-Kutta integration followed by spectral analysis. SR, implemented through PySR, is then trained on these datasets for six configurations spanning cubic, quartic, and quintic nonlinearities under both free and forced conditions. In all free-oscillator datasets the oscillation amplitude is fixed (normalized to $A=1$), so the learned relations are parameter-frequency relations at fixed amplitude. For free oscillators with known analytical solutions, SR reproduces the reference expressions to machine-level numerical precision ($R^2=1.0000$, mean squared error (MSE) $\sim {10}^{-17}$), returning the Lindstedt-Poincaré, harmonic-balance, and first-harmonic-balance expressions used to generate the labels. For forced oscillators, where the response amplitude is defined implicitly as the root of a cubic (or quintic) polynomial in $A^2$, SR captures the dominant resonance structure but cannot fully resolve the implicit-root behavior with the present algebraic operator set ($0.53\le R^2\le 0.83$). These results position SR as a practical complement to classical analytical approaches to nonlinear dynamics, with particular value in contexts where specialized perturbative methods are inaccessible or their validity is restricted to narrow parameter regimes. We are explicit about the limits of the present scope: amplitude dependence, robustness to noise, extrapolation beyond the training box, and run-to-run variability of the stochastic search are identified as the validation steps required before any claim of genuine discovery can be made.

In discrete models describing growing rough interfaces in the Kardar-Parisi-Zhang universality class, we examine height fluctuations at a fixed site as a function of time, measured in monolayer units. For small systems, we show that it is possible to reach the stationary state. We compute the two-time autocorrelation and power spectra independently. The correlation function remains nonexponential and vanishes after a correlation time that diverges with system size. As a result, the power spectra display a lower cutoff with constant power. In the nontrivial frequency regime, we observe $1/f^{\gamma }$-type scaling with the spectral exponent 5/3. Finite-size scaling reveals that the temporal correlation function follows dynamic scaling. Our findings, supported by scaling-theoretical arguments, establish that the fluctuations are wide-sense stationary, implying the applicability of the Wiener-Khinchin theorem. The scaling arguments also reveal a scaling relation $\gamma =1+2\alpha /z$, where $\alpha$ and $z$ denote the roughness and dynamical exponents.

Density cube theory extends the canonical quantum density matrix ${\rho }_{ij}$ with the addition of an extra index to ${\rho }_{ijk}$. The elements of the density cube with two different indices, ${\rho }_{iij}$ and ${\rho }_{ijj}$, correspond to the real and imaginary parts of the off-diagonal element ${\rho }_{ij}$ of the density matrix and describe double-path interference, while those with three different indices describe noncanonical triple-path interference. In this Letter, we propose an equation of motion for the density cube, obtained from the quantization of ternary Nambu dynamics, and find that pairs of triple-path interferences oscillate into each other.

The Casimir-Polder interaction energy between a unipolarizable point atom and a unipolarizable dielectric ring has been limited, until now, to the case when the atom is confined on the axis of symmetry of the ring. We find the generalized analytical expression for any position of the atom relative to the ring in terms of complete elliptic integrals. This is aided by the construction of a class of integrals of a Jacobian elliptic function as a linear combination of complete elliptic integrals. Our expression for the interaction energy allows us to investigate the instability of the atom even for the equilibrium points that exist off the axis of symmetry.

We find the ground-state energy of the Ising model using the cascaded variational quantum eigensolver algorithm with the guided-sampling ansatz using up to 63 qubits on a quantum computer. We study a heavy-hex lattice to match the qubit architecture, allowing us to perform calculations on a scale that is inaccessible to exact diagonalization. We study both a homogeneous and a random-coupling model. We locate the boundary of acceptable quantum errors as a function of the number of qubits and coupling strength. An entropic analysis is performed, giving insights into the quantum computing performance. A subspace analysis is performed, which suggests that the Ising model is especially suited for near-term quantum computing.

We investigate dissipative charging of a single particle in finite tight-binding lattices coupled to engineered nonequilibrium Markovian reservoirs. The engineered number-conserving bond jumps convert local antisymmetric bond modes into symmetric modes, thereby steering the system toward upper spectral-edge states with finite steady-state ergotropy. In an even periodic chain, this mechanism admits a simple bond-mode interpretation and gives ${\mathcal{E}}_{\mathrm{ss}}=4t$ in the clean limit, where $t$ denotes the uniform nearest-neighbor hopping amplitude. We further show that the same dissipative charging principle applies to a two-dimensional honeycomb tight-binding lattice. For on-site Anderson disorder, disorder-averaged calculations show that the mixed steady state becomes more spatially concentrated, while the final ergotropy decreases and the charging transient shortens over the examined parameter range. Additional local dephasing produces a similar finite-time trade-off in the displayed rate window. The finite-time metric $P_{0.99}$, defined by $P_{0.99}=0.99{\mathcal{E}}_{\mathrm{ss}}/{\tau }_{0.99}$, with ${\tau }_{0.99}$ the first time at which the ergotropy reaches $99\%$ of its steady-state value, is therefore interpreted as a battery-side charging measure rather than the net thermodynamic power or efficiency of the full reservoir-engineering apparatus.

The continuum emission from the hot and ionized inner regions of accretion disks around supermassive black holes (SMBHs), which is strongly lensed by the light ring (i.e., the unstable photon orbit), is always superimposed on that from the locally emitting plasma near the innermost stable circular orbit, masking strong-gravity effects and making their study difficult. Cleaner images of (strong-lensing)-generated brightness distributions set against a nonluminous background would thus be preferable. An SMBH illumination source that allows for this could be the more distant, cooler, neutral gas reservoir, underlying the so-called broad line region. Such a far-field illumination is ideal for producing the aforementioned images, and thus better suited for strong-gravity tests. In such an illumination scenario, however, two prominent first-order effects stand out, whichwill be the focus of this Letter: an hourglasslike brightness distribution around the SMBH and an associated double-peaked inner feature imprinted on the disk's global double-horned line profile, for lines of sight near the accretion disk plane. The latter effect can be discerned even in unresolved sources where only the total line profile is accessible. Interferometers operating in spectral line mode can reveal this hourglass image and the inner double peak spectral feature it imprints on the global line profile, and yield SMBH mass estimates for edge-on systems.

Scattered light is one of the most common sources of noise in the Laser Interferometer Gravitational Wave observatories (LIGO). Light scattering is a highly nonlinear process through which motion at low frequencies gets up-converted and creates noise in a higher-frequency band in the detector data. From the beginning of the fourth observation run, many glitches appeared in the data of LIGO Livingston detector in the frequency range 10–40 Hz, and the morphology of these glitches suggested that they were produced by scattered light. From our analysis, we identified two different populations of scattered light glitches, one group having higher signal-to-noise ratio (SNR) than the other. The glitches of the high-SNR group were solely modulated by microseismic ground motion (ground motion in 0.1–1.0 Hz), and in this paper, we present models of possible coupling mechanisms for these glitches. We also present results of a statistical correlation analysis based on our models, which indicates that the microseismic ground motion at the corner station along the X direction is the one most correlated with the noise that creates these high-SNR glitches. After installing baffles very close to the test mass mirrors, we have noticed a significant reduction in the rate and SNR of these glitches. The low-SNR glitches were primarily modulated by high-frequency (10–30 Hz) vertical ground motion at the corner station, and this motion was coupling through a specific vacuum chamber at the corner station. After installing an additional seismic isolation platform in that vacuum chamber, these glitches have disappeared.

The uncertainty principle constitutes a cornerstone of quantum mechanics. However, its conventional formulations do not adequately describe uncertainty in scenarios involving conditional measurement. In this work, we propose uncertainty relations based on conditional variance and conditional expectation. We define the conditional expectation operator $E\left(\widehat{A}\right|\widehat{B})$, its dual operator $E\left(\widehat{B}\right|\widehat{A})$, and a corresponding conditional covariance term ${\mathcal{R}}_{\text{corr}}$. We demonstrate that even for noncommuting observables $\widehat{A}$ and $\widehat{B}$, their conditional expectation operators can possess a nonvanishing commutator. This leads to a strengthened uncertainty relation applicable to both pure and mixed states. In addition to the standard term arising from the noncommutativity of the observables themselves, our relation incorporates three distinct contributions: one from the noncommutativity of the conditional expectations, one from quantum coherence, and one from the conditional covariance. These contributions collectively yield a significantly tighter lower bound. Numerical simulations verify the generality and enhanced tightness of the proposed relation. Our results provide a refined theoretical tool for the joint estimation of multiple observables in composite quantum systems, with potential applications in quantum precision metrology and secure quantum key distribution.

Detecting weak field perturbations at an optical-vortex node is a fundamental challenge across wave physics, as the local signal contrast typically scales quadratically with the impurity amplitude when no reference field is used. Here, we propose a complementary, spatially resolved diagnostic that exploits the strongly nonlinear response of an electromagnetically induced transparency (EIT) medium to transduce weak topological impurities into probe transmission. Using a vortex beam with a weak coherent admixture as a concrete realization, we show theoretically that EIT coherence converts the weak field that lifts the nominal vortex node into a highly sensitive, macroscopic transmission contrast. A resonant weak-probe model with representative cold-${}^{87}\mathrm{Rb}$ parameters predicts a per-exposure detection floor for the impurity amplitude at the level of a few $\times {10}^{-3}$, relative to a separately characterized, preaveraged pure-vortex reference. We quantify the intrinsic and experimental limits of this response, analyzing its dependence on coupling strength, ground-state decoherence, optical depth, two-photon detuning, and Maxwell-Boltzmann thermal motion. While not a complete, basis-independent measurement of modal purity, this method provides a calibrated, local all-optical diagnostic for weak coherent field admixtures at a known vortex node.

We investigate the collective behavior of motile rods immersed in a monolayer of apolar rods confined between vertically vibrating plates using numerical simulations. We uncover an antidiffusive phenomenon whereby motile rods segregate from the apolar medium and form anisotropic flocks whose size increases with the medium concentration. Remarkably, enhanced segregation leads to a reduction of the global polar order, giving rise to an anomalous dependence of the polar order on the medium concentration and the angular noise of the motile rods. The flock structure is strongly influenced by the anisotropy of the medium rods. For small aspect ratios, the flocks are elongated perpendicular to the mean direction of motion, whereas for larger aspect ratios they elongate along the direction of motility. We rationalize the emergence of segregation-induced disorder using a minimal mean-field model.

We investigate the role of stochastic resetting in non-Markovian systems, where memory effects arise due to slow relaxation, rugged energy landscapes, disordered environments, and molecular crowding. Using the celebrated continuous-time random walk framework, we analyze first-passage processes with multiple competing outcomes and examine how resetting can selectively enhance desired outcomes. We characterize the efficiency of resetting through conditional mean first-passage times and demonstrate that its impact is highly sensitive to the underlying waiting-time statistics. Furthermore, we derive an inequality that quantifies how resetting controls fluctuations in conditional first-passage times, revealing regimes where variability is significantly suppressed. Our results provide a systematic understanding of how long-term memory influences competitive first-passage outcomes and establish resetting as a powerful control mechanism beyond the conventional Markovian setting.

We propose a microscopic realization of the idle-level quantum heat engine architecture based on a two-qubit non-Hermitian XY model with a staggered imaginary magnetic field. The energy spectrum naturally separates into two working levels coupled to the external field and two field-decoupled idle levels entirely independent of it. Tuning the non-Hermitian parameter drives the system from a dissipative accelerator regime into a genuine heat engine regime, while simultaneously enhancing both the net work output and the cycle efficiency. The efficiency enhancement originates from the compression of the idle-level gap, which redistributes level occupations and progressively suppresses the idle-level heat current, signaling the approach to the reverse heat-flow regime that underlies the idle-level engine principle. We map the full thermodynamic phase diagram identifying engine, refrigerator, accelerator, and heater regimes, and decompose the heat current into working-level and idle-level contributions to clarify the microscopic origin of the performance gain. The model is implementable in trapped-ion and NMR quantum simulators. These results establish non-Hermiticity as a versatile control knob for idle-level quantum thermal machines.

We study the refrigerator working between a finite-sized cold heat bath and an infinite-sized hot heat bath (environment) in the nonlinear response regime. We assume that the initial temperature $T_i$ of the finite-sized cold heat bath satisfies $T_i\le T_h$, where $T_h$ is the temperature of the hot heat bath. By consuming the input power, the refrigerator transfers the heat from a finite-sized cold heat bath to the hot heat bath. Hence, the temperature of the finite-sized cold heat bath decreases until it reaches the desired low temperature $T_f$. By minimizing the input work for the heat transport process, we derive the optimal path for temperature change. We calculate the coefficient of performance as a function of average input power. We also obtain the bounds for the coefficient of performance by applying the asymmetric dissipation limits. For the parameter values considered in this study, we observe that the relation between the coefficient of performance and the average input power strongly depends on the nature of the finite-sized heat cold bath.

Epitaxial strain provides a powerful, nonchemical route to tune the properties of functional materials by modifying the coupling between spin, charge, and lattice degrees of freedom. We investigate strain-controlled magnetic transitions within an anisotropic half-filled one-band Hubbard model in three dimensions. In this framework, strain is introduced through anisotropic hopping processes between nearest- and next-nearest-neighbor sites. Using a semiclassical Monte Carlo (s-MC) approach, we construct ground-state phase diagrams in the nonperturbative regime, which show how uniaxial hopping anisotropy stabilizes distinct magnetic ground states: Compressive strain drives a transition from a G-type to a C-type antiferromagnetic (AF) insulator, whereas tensile strain suppresses the C-type AF order, favoring an A-type AF phase. Furthermore, we examine the effect of the on-site Hubbard interaction strength ($U$) on these phase diagrams, revealing systematic evolution of the competing magnetic phases. Overall, our s-MC calculations emphasize that directional electronic anisotropy is a powerful tuning parameter for controlling competing magnetic orders in correlated systems, offering valuable insights for the design of strain-controlled materials.

Complex numbers, intrinsic to the formulation of quantum theory, play a pivotal role in enabling advantages across a broad range of quantum information-processing tasks. Despite their fundamental importance, practical and scalable criteria for detecting quantum imaginarity remain relatively underexplored, particularly methods that enable its identification with reduced experimental overhead. In this work, we propose a realistic and experimentally feasible method to detect quantum imaginarity using moment-based approach. Our framework relies on experimentally accessible moments of the Kirkwood-Dirac quasiprobability distribution, enabling scalable detection in high-dimensional systems without requiring full state tomography. We then present illustrative examples to support our detection scheme. Finally, we present an interferometric scheme for measuring these moments, paving the way for experimental implementation of our detection protocol.