Papers

Proton exchange membrane water electrolysis (PEMWE) is among the most promising techniques to provide hydrogen as both energy carrier and feedstock for the chemical industry, due to its compatibility with intermittent renewable electricity sources. However, a major bottleneck in scaling up PEMWE is the limited supply of the anode catalyst Ir. This work shows a novel approach to tailoring ionomer-free catalyst layers based on custom-made microporous substrates and two different atomic layer deposition (ALD) processes, both using Ir(EtCp)(CHD) precursor. Thermal ALD using O3 as counter-reactant yields mostly metallic Ir/IrOx and an electrode Ir loading of 0.21 mg/cm2. The PEMWE cell-level performance is comparable to a commercial catalyst-coated membrane anode despite 7x lower loading, and is maintained over an accelerated durability test equivalent to 600 h of intermittent operation. Moreover, using a low-loading ALD-made cathode, the total platinum group metal loading is only 0.24 mg/cm2. Plasma-enhanced ALD reduces the Ir loading to 0.04 mg/cm2 by tailoring the catalyst distribution, however, yields lower-activity IrO2. Finally, direct ALD catalyst deposition needs no ionomer-bearing ink. The anodes are therefore compatible with various membrane materials, as demonstrated in a CO2 electrolysis experiment with an anion exchange membrane.

Ordinal optimization selects designs that are good enough rather than optimal when evaluation is expensive and the budget is small. The alignment probability measures the chance that the selected set contains at least a prescribed number of truly good designs. We formulate quantum ordinal optimization as a class of problems that maximize this probability under a fixed oracle budget. We study exact, coherent pairwise comparisons with one selected design as a first instance, with the budget counted in comparison queries. For every classical comparison budget smaller than the number of designs, we prove that a knockout among uniformly sampled designs attains the optimum. The sample is drawn without replacement and contains one more design than the number of comparisons. For a uniformly random order, the selected design's rank has a polynomial probability law. At the same comparison budget, the maximum quantum degree is at most twice the classical maximum, a factor attained whenever there are more than twice as many designs as comparisons, so a quantum algorithm can realize rank laws that no classical algorithm with the same budget can. We determine the exact quantum optimum with one comparison for every number of designs and every good-enough set. For selecting the best of n designs, the optimal success probability with one quantum comparison is approximately 3.30/n for large n, compared with 2/n for one classical comparison. When the best design is sought, one quantum comparison gives a higher alignment probability than two classical comparisons whenever there are more than nine designs.

Magpie is a fully graphical linear spin-wave software which has its main focus on 3-d visualisation of magnetic models and magnon dispersion relations. The software is distributed under an open-source license and is written in high-performance, portable C++. Its modular architecture allows for a rapid development of new calculation modules and permits the inclusion into external applications. Included code generators ensure seamless interoperability with other linear spin-wave libraries.

The Hanbury Brown-Twiss (HBT) effect marked a significant milestone in quantum optics by illustrating that intensity correlations can reveal inherently quantum features of light. Motivated by the structure of the original 8-mode HBT interferometer, we develop a simplified 4-mode toy-model that captures its essential physical ingredients while significantly reducing analytical complexity. Our toy-model provides an intuitive and well-structured framework for examining the desired correlation functions. We investigate whether our toy-model can exhibit genuinely non-classical behaviour by formulating and applying a Bell-type inequality tailored to its specific measurement configuration. Our analysis shows that the correlations generated by the toy-model violate the inequality, indicating the presence of non-local features that are incompatible with any classical hidden-variable description. The results highlight the power of simplified models in uncovering fundamental aspects of non-classicality in optical systems.

The rotating vector model (RVM) is widely used to interpret pulsar radio polarization under the assumption of a dipolar magnetic field. Motivated by tentative evidence for non-dipolar magnetic structure in millisecond pulsars provided by recent modeling of surface thermal X-ray pulsations, we examine how a global quadrupole component modifies position-angle (PA) behavior within the classical RVM framework. We numerically integrate magnetic field lines in static vacuum magnetospheres composed of a centered dipole component that is inclined with respect to the spin axis, and a centered quadrupole component aligned with it. We then compute the open field line regions (OFLRs), emission skymaps, and PA curves for a range of dipole inclinations, relative quadrupole strengths, and light cylinder radii corresponding to two trial spin periods of 1\,ms and 5\,ms. We find that quadrupole-modified magnetospheres produce a wide variety of PA behaviors and substantially alter the morphology and total area of OFLRs, with the OFLR area varying non-monotonically with quadrupole strength and, in some cases, exceeding that of the corresponding pure dipole. Depending sensitively on the field configuration and viewing geometry, three broad PA regimes can be distinguished: a) nearly dipolar PA swings that are largely insensitive to emission altitude; b) moderately distorted, altitude-dependent PA tracks that can bias dipolar RVM fits; and c) strongly dispersed PA behavior associated with emission from different OFLRs, which can remain incompatible with a single dipolar PA track even within narrow emission altitude ranges. These results demonstrate that dipole-like PA curves do not uniquely imply a purely dipolar magnetic field, while global quadrupole components alone are insufficient to reproduce the full complexity of observed millisecond pulsar PA profiles.

The coherent exchange of pairs of quanta between two bosonic modes is equivalent, up to a numerical factor, to the generator of two-axis twisting, which attains Heisenberg scaling of the squeezing; we determine how much of that equivalence survives in a realistic nonlinear medium. In any such medium the exchange term is accompanied by a local Kerr nonlinearity, and within a sector of fixed particle number the Hamiltonian depends on a single dimensionless ratio of the effective Kerr strength to the exchange strength. We derive two criteria governing this ratio and show that they are independent. The first is the rate at which squeezing is generated: the exponential rate follows in closed form, vanishes exactly when the two strengths are equal in magnitude, and recovers as the square root of the detuning from that point. The second is the depth to which squeezing can be driven: at fixed particle number the attainable depth is a function of the anisotropy of the mean-field saddle alone, reaches the full two-axis-twisting value only for the isotropic saddle, and is independent of the rate, parameter sets sharing the same anisotropy but differing in rate by a sizeable factor giving depths that agree to every printed digit. The closed-form Gaussian dynamics reveals a pitfall: extracting rates from short-time data overestimates them by more than a factor of two unless the saddle is isotropic. An isotropic cubic nonlinearity imposes the value of the ratio where the rate vanishes, so realizing two-axis twisting by pair exchange requires detuning it; a moderate mismatch already recovers almost all of the optimal depth. We also explain why the constraint has not surfaced before: at two quanta the self-Kerr shifts the two coupled states equally, so the two twisting Hamiltonians are rigorously indistinguishable, the degeneracy being lifted only from four quanta.

We consider singular Schrödinger operators with an attractive $\delta'$ interaction of strength $\beta$ supported by a star graph and prove that the ground-state eigenvalue is uniquely maximized by stars of the maximum symmetry. Two different proofs are presented, one for an even number of edges using a comparison to the $\delta$ interaction star, the other general based on Birman-Schwinger technique.

A long-standing challenge in climate science since the Charney Report in 1979 is to determine how much the Earth's climate warms in response to a unit external energy input at the top of the atmosphere (TOA). In this study, we show from first principles that temperature feedback within an atmosphere-surface column operates as a set of feedback circuits, each governed by an intrinsic gain less than unity, leading to geometric amplification of energy through successive feedback cycles. In particular, the surface-centered temperature feedback circuit determines the amplification of surface energy per unit TOA forcing. The surface energy amplification by non-temperature feedback is estimated from the amplification of solar energy absorption by downward longwave radiation at the surface in the climate mean state. Climate sensitivity then emerges as the product of these two amplifications scaled by the surface Planck feedback parameter. The climate sensitivity derived from the 1980-2000 climate mean state is 1.15 K (W m$^{-2}$)$^{-1}$. It yields a warming of 0.44 K from 1980-2000 to 2000-2020, consistent with the observed warming of 0.41 K, and equilibrium warmings of 3.02 and 5.83 K for CO$_2$ doubling and quadrupling, respectively, the former consistent with the Charney estimate near 3 degrees C. The framework provides a basis for predicting global surface temperature responses to other external forcing scenarios from the climate mean state.

Low-loss stoichiometric silicon nitride on oxidized silicon has emerged as the major wide-band photonics platform for nonlinear and quantum photonics. These films, deposited by low-pressure chemical vapor deposition (LPCVD), are well known to have around 1000 MPa of residual tensile stress, which often leads to cracking when film thickness exceeds 400 nm. Although various stress-mitigation approaches can isolate or prevent cracking, this stress issue remains a major fabrication challenge. Low-residual-stress LPCVD stoichiometric silicon nitride on sapphire has also been reported and recently explored for photonics at telecommunication wavelengths. Here, we advance its development through systematic characterization, including thin-film stress analysis, ellipsometry and prism-coupling measurements of refractive index and loss, and swept-wavelength spectroscopy of fabricated photonic devices across a broad range of wavelengths. We demonstrate the direct growth of crack-free stoichiometric silicon nitride up to 2 {\mu}m thick with only 200 MPa of stress. Our fabricated devices show propagation losses of 0.35 dB/cm around 780 nm, 0.37 dB/cm around 1064 nm, and 0.25 dB/cm around 1630 nm. In addition, prism-coupling measurements indicate film losses below 1 dB/cm at wavelengths down to 500 nm. Our work highlights stoichiometric silicon nitride on sapphire as a promising wide-band photonics platform.

The integer and fractional quantum Hall effects reveal that quantized physical responses can take integer and fractional values, respectively. This naturally raises the question of whether quantization can extend beyond rational numbers to an irrational value. Here we show that such a quantized response can emerge from the limiting behavior of a finite, experimentally realizable geometric network. We develop a method based on infinite geometric structures, in which a sequence of finite networks rapidly converges toward an infinite limit. Following this approach, we identify a planar network whose normalized resistance converges to the irrational value $\sqrt{3}$, and realize a finite approximation with high-precision geometric control. The measured normalized resistance is $1.735 \pm 0.001\, h/e^2$ for a fully occupied Landau level in the designed pattern. Our experimental results extend the concept of quantization beyond rational values and demonstrate that an irrational quantized response can be approached through a finite physical system.

Levitated dielectric sensors are often treated as perturbative probes of a pre-existing optical field. We show that this picture fails for a novel sensor geometry: a dielectric plate whose transverse extent captures the full optical mode. Even an optically thin sensor with modest refractive index can heavily restructure the intracavity fields, effectively partitioning a cavity into two subcavities with substantial cross-coupling and producing new optical resonances and trapping sites with properties which deviate from the standard intuition. Conventional perturbative expressions for the cavity frequency shift and optomechanical coupling depart from the exact solution at thicknesses as small as $\sim\lambda/(10n)$. Furthermore, cavity locking decreases the coupling and increases the trap stiffness by orders of magnitude, and the coupled subcavity structure permits appreciable optical cooling at zero detuning, a distinct behavior unique to this nonperturbative regime. These effects, sharing a common origin, establish a distinct regime of cavity optomechanics in which the sensor is no longer merely a probe of the cavity field, but an element that helps define it.

Strongly interacting fermionic chains obeying a $Z_n$ symmetry can host topological phases with highly degenerate ground-state manifolds. The different ground states are connected by strongly bound fractionalized edge modes called parafermionic zero modes. While exactly preserved under time evolution at zero temperature, interactions lead to a destabilization of these modes at finite energy densities, and, given a generic Hamiltonian, obtaining the lifetime of these modes is often impossible as it requires knowledge of the full spectrum of the Hamiltonian or long time evolutions. Here, we propose a novel quantum-inspired algorithm that can be used to variationally search for these almost strong zero modes in generic parafermionic chain models. We demonstrate analytically and numerically that our ansatz faithfully reproduces the exact results and finds strongly bound parafermionic operators in the non-integrable Kitaev-Hubbard chain and chiral Potts model. Our results further allow us to verify the existence of a true strong zero mode in the symmetrical limit of the chiral Potts model for $Z_3$-parafermions.

Spatial interference can break the inversion symmetry of an effective Josephson potential even in a laterally homogeneous junction with inversion-symmetric local energy. We derive a general criterion based on harmonic-dependent complex spatial form factors: a single local harmonic remains a shifted cosine, whereas multiple harmonics can acquire phases incompatible with any common inversion center, permitting cubic interactions and three-wave mixing. Phase reflection reverses all odd-order expansion coefficients about corresponding minima while preserving the even-order ones. For a capacitively shunted junction at fixed charging energy and arbitrary offset charge, it also preserves the complete quantum spectrum, enabling reversal of the odd nonlinear sector without spectral retuning. A centered cross junction with multiple local harmonics is one concrete example. Within the imposed-field model, a three-component magnetic field can generate an inversion-asymmetric effective potential, and reversing an odd number of field components exactly reflects it without changing the quantum spectrum of the capacitively shunted junction.

In molecules, electronic coherence typically decays within a few hundred femtoseconds, a timescale usually attributed to the environment. We show that it is set to a large extent by which coherences are excited: the molecule can host coherences that the bath barely sees, and optimal control can find and exploit them. Using gradient-based optimal control (GRAPE) with Redfield dynamics, we maximize the total vibronic coherence between the electronic ground and an optically bright electronic excited state in a three-state model with nonadiabatic features, in two regimes of low and high nonadiabatic mixing and for different system-bath coupling strengths. The Liouvillian spectrum reveals, in both regimes, a well-separated coherence mode with substantial ground-bright character that decays on a picosecond timescale. This mode is protected by mixing with the dark state, which brings the geometry of the optically accessible excited state close to that of the ground state and thus weakens its coupling to the bath. Without prior information, GRAPE finds this mode and keeps the photoexcited wave packet near the Franck-Condon region. At equal fluence, it increases the coherence at 800 fs by more than two orders of magnitude over a Gaussian pulse at the weakest coupling, and by many more at stronger coupling. The Liouvillian predicts the bath dependence of the long-lived coherence to within 1%, and a Gaussian pulse tuned to the mode frequency comes within 10% of the best pulse found. Beyond two-level and spin systems, our study puts forward the vibronic structure of molecules as a route to protected coherence subspaces, identifying a dark-state protection mechanism and a design criterion based on molecular parameters. These results lay the groundwork for our goal of using vibronic molecular systems as a resource for long-lived, controllable coherences in molecular quantum information science.

Measurements from the NASA Parker Solar Probe (PSP) mission demonstrate that inside $\sim20$ solar radii ($\Rs$) the magnitude of the interplanetary magnetic field does not fall off simply as $1/R^2$, with $\avg{|B|}\,R^2$ 15–20% below its value at $\sim60\,\Rs$. Here we use PSP magnetic field measurements over $10.6$–$56.8\,\Rs$ to show that the outward rise of $\avg{|B|}\,R^2$ is not due to the global structure of the heliospheric magnetic field or proximity to the heliospheric current sheet but is the direct result of the growth of large-amplitude, spherically polarized Alfvén waves (so-called `switchbacks'). Over the same distance range, $\avg{B_R}\,R^2$ stays constant, so that the sector-signed radial flux is conserved. The wave amplitude $\epsilon = B_{\perp,{\rm rms}}/\avg{B_\parallel}$ grows from $0.26$ to $0.57$ as $R^{1/2}\cos\alpha$, and $\avg{|B|}/\avg{B_R}$ rises by $20\%$. A simple model parametrized by the broadening of the distribution of deflection angles reproduces the effect to high accuracy. These results demonstrate that as the relative wave amplitudes grow with increasing solar distance, a dynamo-like process operates to enhance the field magnitude by up to $20\%$. By enhancing magnetic pressure this has implications for the large scale solar wind structure in the low-beta inner heliosphere, as well as partially resolving the long-standing discrepancy between remote measurements of the solar magnetic field and those made in situ by earlier missions farther from the Sun.

A characteristic feature of topological field theories is the absence of local propagating degrees of freedom. In four-dimensional BF theory with cosmological term, we make this feature manifest by exactly reducing the finite non-Abelian shift symmetry. We do so by identifying a higher dressing field, a 1-form compensating the shift, allowing to build from first principles the composite shift-invariant field $\boldsymbol{B}=B-\lambda^{-1}F$. In terms of this dressed field, the dynamics becomes algebraic and sets $\boldsymbol{B}=0$, directly exposing the absence of local propagating degrees of freedom. This provides the first explicit instance of the higher-form Dressing Field Method.

How charge rearranges within an electrode shapes the behavior of batteries, supercapacitors, and other electrochemical devices. Molecular simulations can capture this response by allowing the charge on each electrode atom to adjust to its surroundings, but repeatedly calculating these charges adds substantial computational cost. We present an open-source implementation of the constant-potential method in GROMACS that integrates these calculations into the program's optimized CPU and GPU routines. Comparisons with established codes validate the electrode charges, while charging, voltammetry, and impedance simulations demonstrate the response to changing electrical conditions. The implementation also supports electrodes that move or deform and models of finite metallic screening and electron spillover. In a pair of charged carbon nanotubes, allowing charge to move away from the facing surfaces reduces the repulsive force at contact by about half at an intermediate charge and keeps the pair bound where a uniform-charge model opens within the simulated time. These capabilities make the electrical response of electrodes accessible within GROMACS for studies of interfacial structure, charging dynamics, and electrode motion.

The coexistence of multiple classes of localized states, including different types of topological corner states, is highly desired; yet its realization typically requires sufficiently strong long-range couplings, bringing challenges to experimental realizations across a wide range of systems. Here, we demonstrate the emergence of multiple localized corner modes evolution under purely nearest-neighbor coupling conditions without long-range couplings, not even next-nearest-neighbour couplings, and experimentally confirm their coexistence in a single lattice. Our platform simultaneously hosts type-I and type-II corner states, corner localized bound states in the continuum, flat-band states, and edge states. We experimentally realize such lattice using topolectrical circuits, a system that can strictly exclude long-range coupling by design, enabling direct characterizations of both the energy-band spectrum and the spatial profiles of the localized eigenmode. This work demonstrates that solely modifying nearest-neighbor couplings can replace the role of long-range interactions in realizing multiple types of corner states, providing a deterministic and widely accessible route to multiple corner-state classes and rich localized states, with immediate potential for mode-division multiplexing and multimode topological devices.

The anomalous Hall effect (AHE) in magnetic Weyl semimetals arises from distinct microscopic origins-intrinsic Berry curvature and extrinsic scattering mechanisms-yet reversible switching between these regimes within a single material platform remains elusive. Here, we demonstrate that off-stoichiometric tuning of the Al/Si ratio (from ~1.05 to ~0.75) reversibly drives an intrinsic-extrinsic-intrinsic crossover of the AHE in PrAlSi single crystals. Across four compositions spanning a narrow Si variation (PrAl0.93Si0.89 to PrAl0.79Si1.06), the anomalous Hall conductivity (AHC) exhibits a non monotonic arch (170-1413- 507-164 {\Omega}-1cm-1). The intermediate composition PrAl0.90Si0.94 (Al/Si ~0.96) exhibits high carrier mobility, multi carrier transport, yielding a giant AHC of 1413 {\Omega}-1cm-1 dominated by extrinsic skew-scattering. The Si-poor and Si-rich compositions exhibit lower AHC values and intrinsic Berry-curvature-dominated AHE, establishing a composition-driven intrinsic-extrinsic-intrinsic crossover. Deviating from the intermediate composition suppresses mobility and reverses carrier type from hole-like to electron-like. The Al/Si ratio thus serves as a chemical knob that primarily modulates the Fermi level via compositional band filling, while off-stoichiometry-induced chemical disorder plays a subordinate role in determining the AHE mechanism. These results position off-stoichiometric PrAlSi as a tunable platform where subtle compositional variation reversibly switches the AHE mechanism.

We observed comet 2P/Encke with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope on UT 2003 November 12.3, when the comet was at heliocentric and geocentric distances of 1.09 and 0.27 au, respectively. Imaging observations of the comet with narrow-band filters centered at 8.8, 10.5, 11.7, 12.4, 18.8, and 24.5 $\mu$m and low-resolution spectroscopic observations in the N-band (8-13 $\mu$m, $R\sim250$) of the comet were performed. The observed spatial profiles of the comet were consistent with those of a standard star (FWHM $\sim$ 0.3” at 10.5 $\mu$m, close to the diffraction-limited image size), indicating that the observed spectrum was dominated by thermal emission from the cometary nucleus. The semi-axial ratio ($a$/$b$) of the nucleus of 2P/Encke is estimated as 2.26$^{+0.33}_{-0.21}$ based on the isothermal, prolate ellipsoid model. The photometric data with the correction for rotational phases, can be explained by a blackbody temperature of $328\pm7$ K, consistent with the nucleus surface temperature empirically estimated at 1.09 au from the Sun (327 K). This blackbody approximation for the nucleus leads to $a = 3.6^{+0.5}_{-0.3}$ km and $b = 1.6^{+0.2}_{-0.2}$ km by assuming an emissivity of unity. The observed low-resolution N-band spectrum showed an overall smooth continuum with no prominent excess emission feature at $\sim$10 $\mu$m due to fine silicate grains in the cometary coma. The relative emissivity spectrum of the nucleus showed a negative feature at $\sim$9.5 $\mu$m, as seen in the mid-infrared nucleus spectrum of 460P/PanSTARRS [T. Ootsubo, et al. (2021), Icarus, 363, 114425].

We present a unified Bayesian analysis of Higgs-portal, neutron-decay, and axion-like-particle (ALP)-mediated dark matter in neutron stars within the single-fluid approximation. Using a common relativistic mean-field description of hadronic matter, we combine finite-nucleus and heavy-ion collision data, chiral effective field theory, NICER measurements of four pulsars, and GW170817. The individual dark-sector parameters remain weakly determined, while model-dependent shifts in nuclear skewness reveal the sensitivity of the inferred hadronic equation of state to the assumed dark-matter mechanism. The three scenarios yield substantially overlapping mass-radius and tidal-deformability predictions, with median maximum masses near $2.1\,M_\odot$. For $1.4\,M_\odot$ stars, the Higgs-portal model predicts higher $f$-mode frequencies and shorter damping times than the neutron-decay and ALP models, although their credible regions overlap. Comparison with three consistently reanalysed two-fluid models gives the largest Bayesian evidence to neutron decay: under the adopted priors, its Bayes factors relative to the Higgs-portal and two-fluid alternatives are approximately $24$-$37$, but only $2.2$ relative to ALP. This ranking concerns complete dark-matter models and does not establish a general preference for either fluid description or evidence for a dark component itself. Improved nuclear constraints and future gravitational-wave asteroseismology could provide complementary information to disentangle the hadronic and dark-sector contributions.

Reanalyzing the multi-wavelength data of GRB 240825A, we identify two distinct prompt-emission episodes, i.e. an early, spectrally soft plateau and a subsequent bright, spectrally hard gamma-ray pulse. We show that this signature is consistent with a two-stage central engine model, in which the early soft plateau is powered by the dipolar spin-down radiation of a transient proto-magnetar, while the later hard pulse arises from a relativistic jet launched by fallback accretion onto the nascent black hole via the Blandford-Znajek mechanism. Adopting simulation-motivated initial black hole (BH) masses ($M_{\rm BH,0}$) and spins ($a_0$), our fits to the second episode yield total masses supplied to the post-collapse disk of $M_{\rm fb}=0.45$–$0.96 M_\odot$, fallback radii of $r_{\rm fb}=16.9$–$17.6 r_g$, and characteristic fallback timescales of $t_{\rm fb}=0.13$–$0.25$ s. The corresponding maximum inner accretion rates range from $0.18$ to $0.70 M_\odot \mathrm{s}^{-1}$, which is sensitive to $a_0$. Joint spectral fits with optical-X-ray afterglow data reveal a coupled temporal evolution of dust extinction and equivalent hydrogen column density. Incorporating this extinction evolution, an external forward-reverse shock model in a wind-like medium can account for the radio-to-GeV band afterglow data. Although ambient dust and the bright host galaxy may obscure any associated supernova, late-time optical reddening remains compatible with a supernova contribution. Applying the empirical relation between the prompt spectral peak energy and the SN peak bolometric magnitude gives an illustrative estimate of $M_{\rm bol,peak}=-19.46\pm0.35$ mag for a putative associated SN. These results support a two-stage evolution of the central engine and variable dusty environment of GRB 240825A, which provides insights into the nature of its progenitor.

A gap exists in connecting biological evolution within the framework of statistical mechanics. It has been hoped that statistical mechanics would provide us with a general predictive principle for the emergence of novelty and complexity. However, the emergence of novel functional features initiated by stochastic processes remains difficult to describe, because these processes commonly arise outside near-equilibrium or linear-response regimes. To understand how environmental influences generate diverse, open-ended, complex objects by driving physical systems to specific regions of phase space over long spatial and temporal scales, a new approach to non-equilibrium thermodynamics is necessary. Here, we present the coupling of assembly theory (AT) with statistical mechanics as a framework that works within the laws of thermodynamics, but can contextualise the processes of novelty, complexity, and evolution within these laws. We map construction processes from physical space to assembly space (AS) and introduce the concept of an assembler, a machine that constructs objects contingent on previous states and is represented by bitwise operations. Using this approach, we apply principles from stochastic thermodynamics with AT to define selection within large combinatorial spaces1 and estimate the work required to create novel and complex objects. This approach allows us to represent complex processes, such as selection, within large combinatorial spaces as a set of rules for a memory-feedback loop followed by the assembler. This framework concretely defines the relationships between thermodynamics and information theory by introducing a novel aspect of physics that uses history and causal contingency to influence the probabilistic time evolution of complex systems.

Magnetic circular dichroism (MCD) is an optical probe of orbital time reversal symmetry breaking. Although frequency integrated MCD is related to the self-rotation contribution to orbital magnetization at zero field, its magnetic response generally differs from the thermodynamic orbital susceptibility. Here, we define the MCD susceptibility and derive general expressions for multiband systems using an electromagnetic $U(1)$ gauge invariant approach. For insulators, the response contains contributions from the non-Abelian quantum metric, Berry curvature, and field induced interband mixing. For metals, a finite temperature Green function formulation separates the smooth response into Fermi sea and Fermi surface contributions. An independent Landau level calculation confirms the expressions for the zero-field MCD moment and its linear magnetic response. In a continuum model for twisted bilayer graphene, the MCD susceptibility vanishes within the charge neutrality gap, while the thermodynamic orbital susceptibility remains markedly diamagnetic. Near the gap edges, the orbital moment term dominates the response. Features near the van Hove energies are associated with density of states enhancement. These results clarify how the two susceptibilities reflect different orbital processes even for the same electronic structure and thus establish the MCD susceptibility as a distinct probe of orbital magnetic response.

Magnetic frustration is commonly quantified by the frustration index, calculated from the Curie-Weiss and Neel temperatures. Because both quantities are not simultaneously available for most materials, direct prediction of the magnetic frustration index remains challenging. Here, we propose a machine learning workflow for indirect prediction of the frustration index and consequent screening of potential frustrated magnetic compounds through independent prediction of Curie-Weiss and Neel temperatures. In our work, composition-based models implemented via the CatBoost algorithm, trained on experimental data were optimized using chemically informed dataset subdivision. The highest predictive accuracy was achieved for the rare earth-oxide model in predicting Neel and for the rare earth model in predicting Curie-Weiss. Ensemble uncertainty was incorporated through a conservative frustration index to improve the reliability of candidate selection. Screening of approximately 67000 Materials Project compounds identified 20 high-confidence frustrated magnetic candidates, including several experimentally known frustrated magnets and previously unexplored oxide systems potential for further investigation.

The detection and quantification of quantum entanglement are central problems in quantum information science. Based on the realignment of density matrices and the vectorization of reduced density matrices, we construct a family of enhanced separability criteria for bipartite and multipartite quantum systems. Our criteria recover the previously proposed realignment-based criteria as special cases and detect more entanglement than the earlier ones. Moreover, we derive tighter lower bounds for the concurrence and the convex-roof extended negativity, criteria for detecting the genuine tripartite entanglement, and lower bounds on genuine-multipartite-entanglement concurrence. The advantages of our results are demonstrated with detailed examples.

A subharmonic mixer topology is introduced that uses quarter-wave stubs to create virtual RF/LO grounds and provide impedance matching in close proximity to the antiparallel Schottky barrier diode pair, thereby reducing the electrical length and enabling broadband operation. The RF/LO matching topology is demonstrated at 600 GHz and 1200 GHz, with good agreement between measured and simulated performance. The 600-GHz mixer demonstrates approximately 20% RF bandwidth with a DSB receiver noise temperature below 1300 K across most of the measured band, while the 1200-GHz implementation achieves DSB receiver noise temperatures below 3000 K over a broad frequency range. Both mixers are characterized at room temperature with approximately 2 mW of LO power. The 600-GHz mixer is used in the Submillimeter Wave Instrument (SWI) onboard ESA's Jupiter Icy Moons Explorer. Overall, these results demonstrate state-of-the-art room-temperature performance for broadband receiver front ends targeting atmospheric research and remote-sensing applications.

Stationary scattering admits a dynamical formulation in which the scattering data are extracted from the evolution operator for an effective non-stationary and non-unitary quantum system. This provides a mathematical method of solving scattering problems. We consider the possibility of realizing such a quantum system and relating the scattering information to outcomes of quantum measurements performed on it. To this end, we examine stationary scattering problems in one dimension where the scattering data consist of reflection and transmission amplitudes and the corresponding effective quantum system is a non-unitary two-level system. The states of this system identify points in a Bloch sphere $S^2$ and their evolution yields trajectories in $S^2$. Quantum measurements turn out to be capable of providing information about the reflection amplitudes. We identify configurations displaying reflectionlessness with situations where one or both of the poles of $S^2$ undergo cyclic evolutions. Spectral singularities and coherent perfect absorption correspond to dynamical spin flips which map one of the poles of $S^2$ to the other.

This paper explores topological phase transitions in the momentum space of the $\kappa$-deformed $\phi^4$ lattice model within the mean-field approximation. We show that the double-well structure of the momentum space gives rise to degenerate momentum states at high energies and that this change is marked by a phase transition. We investigate this transition using both numerical and analytical methods, with the analytical approach based primarily on singularity theory. Our numerical analysis shows that the energy at which the topological phase transition occurs is related to the noncommutative parameter by the simple power law $E \sim 1/\alpha^{4}$. By mapping the constant-energy-level surface to the $A_{3}$ singularity, we obtain the same result analytically. We also present results unique to noncommutative systems, showing that the fraction of particles in degenerate momentum states has a nonzero commutative limit. As a nonperturbative effect, this result provides a testable prediction for the existence of noncommutative spacetime.

We investigate finite time vacuum energy relaxation in conformally coupled scalar-tensor cosmology distinguishing the suppression accumulated along a physical trajectory from its asymptotic rate. For a canonical scalar with an exponential potential and constant conformal coupling, the autonomous system exhibits a stability exchange between scalar dominated and vacuum kinetic scaling solutions. In the power-law metric $f(R)=f_0R^n$ realization with $n>2$, the stable scalar dominated branch has a sustained relaxation rate below $0.579$ decades per Einstein frame e-fold. We additionally derive a finite time upper bound that accounts for depletion of the vacuum relative to the scalar potential. For the specified reference initial state $\Omega_{\Lambda,i}=0.99$ and $\Omega_{{\rm kin},i}=10^{-4}$, the bound excludes $60$ decades of suppression within $60$ e-folds throughout the $n>2$ family: $D_\Lambda(60)<47.7$. Numerical trajectories illustrate why this bound is conservative and why the transient contribution cannot be inferred from the final attractor alone. For the reference $f(R)\propto R^{2.14}$ solution, $D_\Lambda(60)\simeq7.53$ decades including a transient excess of about $3.27$ decades relative to uniform evolution at the asymptotic rate. The relaxed quantity is the dimensionless vacuum to gravitational scale hierarchy, its evolution also entails variation of the conformal frame Planck mass. The bounds are conditional on the homogeneous model and specified initial state, not a demonstration of complete cosmological viability.