搜索结果：Theoretische

We present the first lattice QCD determination of the electromagnetic form factors of the exotic tetraquark T_{bb}(bbu[over ¯]d[over ¯]) with quantum numbers I(J^{P})=0(1^{+}). The extracted form factors encode information about its internal structure, including the charge distribution and the magnetic dipole moments, determined separately for the light and heavy quarks. Our results provide evidence in favor of it being a bound state consisting of a compact heavy diquark [bb] in a color-antitriplet with spin one and a light antidiquark [u[over ¯]d[over ¯]] in a color-triplet with spin zero. The charge radius of T_{bb} is found to be significantly smaller than the combined charge radii of B and B^{*} mesons. These two comprise the lowest-lying threshold BB^{*} in the channel that we are considering, and their electric charge form factors are also determined. The computations were performed on a single ensemble, generated by the Coordinated Lattice Simulations effort, with N_{f}=2+1 dynamical quarks and a lattice spacing of approximately a≈0.064  fm at the pion mass m_{π}≈290  MeV.

The thermalizing dynamics of many-body systems is often described through the lens of the eigenstate thermalization hypothesis (ETH). ETH postulates that the statistical properties of observables, when expressed in the energy eigenbasis, are described by smooth functions, which also describe correlations among the matrix elements. However, the form of these functions is usually left undetermined, constituting a key missing component of the ETH framework. In this Letter, we investigate the structure of such smooth functions by focusing on their Fourier transform, recently identified as free cumulants. Using nonlinear hydrodynamics, we provide a prediction for the universal scaling of the late-time behavior of time-ordered free cumulants in the thermodynamic limit. The prediction is further corroborated by large-scale numerical simulations of several nonintegrable one-dimensional spin models that exhibit diffusive transport behavior. Good agreement is observed in both infinite and finite-temperature regimes and for a collection of local observables. Our results indicate that the smooth multipoint correlation functions within the ETH framework admit a universal hydrodynamic description at low frequencies.

Action-detected two-dimensional (2D) spectroscopy resolves the time-dependent nonlinear optical response of a quantum system by recording incoherently detected observables such as fluorescence, photoelectrons, or photocurrents which reflect the system's excited-state population. Processes such as exciton-exciton annihilation alter this population and obscure, for instance, energy-transfer processes. This limits the information available from action-detected 2D spectra compared to their coherently detected counterparts. Here we investigate time gating and kinetic-energy filtering in photoelectron-detected 2D spectroscopy to disentangle various processes. We implement a numerical simulation protocol that allows us to calculate photoelectron-detected 2D spectra for various systems, demonstrating that time gating can extract the same information as coherently detected 2D spectroscopy, even when annihilation is present. Furthermore, we can directly infer annihilation dynamics. Kinetic-energy filtering additionally enables the isolation of specific excited-state dynamics. Our simulations demonstrate that time gating and kinetic-energy filtering are promising extensions for photoelectron-detected 2D spectroscopy.

The weak-field, quasi-static regime of gravity is commonly described by the Newton-Poisson equation as an effective response law. We construct this response within a cost-first discrete variational framework. The Recognition Composition Law (RCL) uniquely selects a reciprocal closure cost within the restricted quadratic symmetric composition class; together with the discrete ledger axioms AX1-AX5 (including conservation) and standard DEC refinement, the Newton-Poisson baseline is then recovered in the instantaneous-closure limit. Conditional on Assumption AS1 (scale-free latency) and Assumption AS2 (causal frequency-wavenumber ansatz), allowing finite equilibration introduces fractional memory into the response, yielding a scale-free modification of the source-potential relation characterized by a power-law kernel wker(k)=1+C(k0/k)α in Fourier space. The kernel exponent α=12(1-φ-1)≈0.191, where φ=(1+5)/2, is derived from self-similarity of the discrete ledger closure; the amplitude C=φ-2≈0.382 is identified as a hypothesis from a three-channel factorization argument. We evaluate this quasi-static kernel-motivated response against SPARC galaxy rotation curves under a strict global-only protocol (fixed M/L=1, no per-galaxy tuning, conservative σtot), using a controlled multiplicative surrogate for the full nonlocal disk operator implied by the kernel. In this deliberately over-constrained setting, the surrogate interface achieves median(χ2/N)=3.06 over 147 galaxies (2933 points), outperforming a strict global-only NFW benchmark and remaining less efficient than MOND under identical constraints. The analysis is restricted to the non-relativistic, quasi-static sector and should be read as a falsifier-oriented galactic-regime consistency check of the scaling window, not as a relativistic completion or a claim of Solar System viability without additional UV regularization/screening.

Controllable covalent surface functionalization of black phosphorus (BP) remains a central challenge in the development of 2D phosphorus-based materials. Here, we report a scalable route to synthesize biodegradable BP-polymer hybrids and establish optimal conditions for BP production, exfoliation, and covalent modification. BP sheets, produced via optimized mechanochemical and exfoliation processes, are covalently functionalized with 2-azido-4,6-dichloro-1,3,5-triazine via a nitrene-mediated [2+1] cycloaddition. The reaction yields a P-N bond, verified by advanced surface analyses and density functional theory (DFT) calculations. The conjugated triazine groups enable subsequent nucleophilic aromatic substitution reactions, providing a versatile platform for controlled post-modification of BP surface. This covalent functionalization strategy addresses key limitations in BP surface chemistry and provides a route toward biodegradable phosphorus-based hybrid materials. As a representative example, functionalization with linear polyglycerol sulfate produces BP-polymer conjugates that inhibit respiratory syncytial virus (RSV) and herpes simplex virus 1 (HSV-1) at low-microgram-per-milliliter concentrations.

We present an extension of the functional renormalization group (FRG) framework developed to compute critical probability distributions of the order parameter to momentum-dependent observables. Focusing on the constraint effective action at fixed magnetization for the Ising universality class, we derive its exact flow equations and solve them at the second order of the derivative expansion (DE2). We solve these flow equations numerically for two- and three-dimensional systems, extract universal rate functions and momentum-dependent correlation functions, and benchmark them against Monte Carlo simulations. In three dimensions, we recover the rate function and accurately reproduce the first few Fourier modes of the constrained correlation function and demonstrate the convergence of the method. In two dimensions, the lowest-order approximations such as local potential approximation fail, and it is required to consider at least the DE2 to describe the critical point. Our results are in qualitative agreement with the numerics. We confirm the robustness of the FRG approach for calculating both zero- and finite-momentum critical observables at fixed magnetization.

Optical circuits and light sources, such as lasers, undergo continuous miniaturization. In its extreme, nanolasers might be composed of only a few molecules confined in plasmonic nanoresonators. Few-emitter lasers promise low-energy requirements and fast responses in a footprint that can be inserted into any device or biological tissue. Utilizing the recently developed stacked hierarchy approach, informed from first principles, we demonstrate the impact of the vibrational structure on lasing, using the example of few-molecule lasing in plasmonic cavities. Explicitly accounting for the entire vibrational manifold unveils resonances in the laser intensity that depend on the Stokes shift, drive strength, and number of emitters. Our work identifies the limits of the omnipresent "incoherent drive" approximation and paves the way for the understanding of nanolasers at the molecular scale.

Diluting solvate ionic liquids (SILs) with small amounts of water combines the advantages of this electrolyte class with those of water-in-salt (WIS) electrolytes. This yields a new class of hybrid electrolytes: water-in-solvate-ionic-liquid (WISIL) electrolytes, as introduced in our previous work (Philipp et al. ChemPhysChem 2026, 27, e70353). Our study uses a combination of Fourier-transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulations to examine hydrogen bonding in water-diluted mixtures of the SIL formed by the equimolar mixture of [Li][NTf2] and triglyme (G3) at varying water content. An exchange of OH and OD in water allows for the separation of overlapping OH bands and their assignment to different water environments: quasi-free OH groups, water coordinated between G3 and [NTf2]-, and water-water hydrogen bonds (HB). The spectra reveal a gradual transition from predominantly dispersed water molecules in the WISIL regime at low water content to extended water-water HB networks at higher water content. MD simulations corroborate these findings by showing that water initially inserts into the cationic [Li(G3)]+ complex and replaces one of the donor functions of a G3 oxygen atom toward [Li]+, resulting in [Li(G3)(H2O)]+ with a long-lived HB between the metal-coordinated water and G3. These complexes progressively disintegrate upon dilution, resulting in increased mobility and bulk-like water behavior. This study emphasizes the narrow compositional window in which adding water beneficially alters the physicochemical properties of SIL electrolytes.

In the last decades, femtoscopic measurements from heavy-ion collisions have become a popular tool to investigate the strong interactions between hadrons. The key observables measured in such experiments are the two-hadron momentum correlations, which depend on the production mechanism of hadron pairs and the final-state interactions. Given the complexity of ultrarelativistic collision experiments, the source term describing the production mechanism can be modeled phenomenologically only based on numerous assumptions. The commonly employed approach for analyzing femtoscopic data relies on the Koonin-Pratt formula, which relates the measured correlation functions with the relative wave function of an outgoing hadron pair and a source term that is assumed to be universal. Here, we critically examine this universality assumption and show that, for strongly interacting particles such as nucleons, the interpretation of femtoscopic measurements suffers from a potentially large intrinsic uncertainty. We also comment on the ongoing efforts to explore three-body interactions using this experimental technique.

We present an approach for efficiently simulating strongly damped quantum systems subjected to periodic driving, employing a periodic matrix product operator representation of the influence functional. This representation enables the construction of a numerically exact Floquet propagator that captures the non-Markovian open system dynamics, thus providing a dissipative analog to the Floquet Hamiltonian of driven isolated quantum systems. We apply this method to study the asymptotic heating of a reservoir in spin-boson models, characterizing the deviation from equilibrium conditions. Moreover, we show how a local driving of two qubits can be utilized to stabilize a transient entanglement buildup of the qubits originating from the interaction with a common environment. Our results make it possible to directly study both stationary and transient dynamics of strongly damped and driven quantum systems within a transparent theoretical and numerical framework.

We investigate magnetic active matter in confined geometries using both experiments with magnetic toy robots, Hexbugs, and simulations of elongated magnetic active Brownian particles in circular domains. Standard active particles tend to accumulate at boundaries, forming clusters even at relatively low densities. In the presence of magnetic interactions, we provide evidence for a fluidization effect that inhibits clustering and shifts its onset to higher packing fractions. Moreover, magnetic dipolar interactions give rise to collective behaviors such as train-like formations, rotating pairs, and rotating clusters.

Odd diffusion breaks time-reversal symmetry in overdamped systems through transverse probability currents while preserving equilibrium steady states. In this work, we develop a dynamical density functional theory (DDFT) for densely interacting odd-diffusive fluids and apply it to ultrasoft particles in two dimensions. In the bulk, odd diffusion qualitatively reshapes collective relaxation by generating transient circulating current patterns that do not exist in normal fluids. Under harmonic ring confinement, the circulation of the probability current induces an angular redistribution of density along the ring during relaxation. This unique footprint of odd diffusion opens up a shorter pathway to equilibrium. Repulsive interactions significantly enhance these effects. Excellent agreement with Brownian dynamics simulations confirms that our odd-DDFT framework quantitatively captures all essential nonequilibrium aspects of the nontrivial odd transport and collective redistribution for dense fluids in both bulk and confined geometries.

In this study, we present a significant advancement in palladium catalysed alkoxycarbonylation of aliphatic olefins. A comparison of privileged bidentate phosphines with different ligand backbones was conducted. Therefore, it can be inferred that L3, with its propyl backbone, is capable of challenging the state-of-the-art systems (L1 and L2). This ligand is particularly well-suited for ester synthesis from simple alkenes with industrial relevance and challenging alkenes having internal or multiple double bonds. In comparison with the other tested ligands, L3 facilitates more efficient synthesis and scale-up.

We explore interpretations of the power-law banded random matrix (PLBRM) ensemble as Hamiltonians of one-dimensional quantum many-body systems. We introduce and compare a number of labeling schemes for assigning random matrix basis indices to many-body basis vectors. We compare the physical properties of the resulting Hamiltonians, focusing on the half-system eigenstate bipartite entanglement entropy. We show and quantify how the different PLBRM phases (ergodic, weakly ergodic, localized), known from the single-particle interpretation, can be interpreted as entanglement transitions in the quantum many-body interpretation. For the weakly ergodic phase, where spectral edge and bulk eigenstates show distinct behavior, we perform a detailed scaling analysis to provide a quantitative picture of the boundaries between different types of entanglement scaling behaviors. In particular, we identify and characterize an intermediate set of eigenstates whose entanglement entropy have volume law scaling but nonvanishing deviation from the Page value expected for maximally ergodic states.

Ion beam technology provides a powerful means for surface modification and nanostructuring of materials. In this work, slow highly charged xenon ions were used to fabricate well-defined nanopits in thin polymethyl methacrylate (PMMA) films. The pit surface density scales linearly with the applied ion fluence, demonstrating that each structure originates from a single ion impact. The formation of these nanopits is interpreted within a plasma expansion framework, in which the potential energy of an individual highly charged ion creates a transient, localized plasma within a nanometric surface region. The subsequent plasma expansion ejects material and produces a shallow surface depression. Numerical solutions of the hydrodynamic equations for the plasma components yield expansion parameters that agree with the experimentally observed pit dimensions and aspect ratios, confirming the plausibility of the proposed mechanism.

We study a two-dimensional crystal composed of active units governed by self-alignment. This mechanism induces a torque that aligns a particle's orientation with its velocity and leads to a phase transition from a disordered to a flocking crystal. Here, we provide the first microscopic theory that analytically maps the crystal dynamics onto a Landau-Ginzburg model, in which the velocity-dependent effective free energy undergoes a transition from a single-well shape to a Mexican-hat profile. As confirmed by simulations, our theory quantitatively predicts the transition point and characteristic spatial velocity correlations. The continuous variation of the order parameter and the divergence of the analytically predicted correlation length imply that flocking in self-aligning active crystals corresponds to a continuous phase transition of the Berezinskii-Kosterlitz-Thouless type in two dimensions and to a second-order phase transition in three dimensions. These findings provide a theoretical foundation for the flocking phenomenon observed experimentally in active granular particles and migrating cells.

The fragmentation properties of parsec- scale clumps play a fundamental role in shaping the dense gas condensations known as cores, the immediate progenitor of stars. The distribution of core masses, the so-called core mass function, is the precursor of the stellar initial mass function, which governs the distribution of stellar masses and, consequently, the evolution of galaxies. The stellar initial mass function is often described by a typical Salpeter-like slope, although deviations toward more top-heavy distributions have been reported in extreme environments, raising questions about its universality and about the physical connection between the two mass functions. To date, there are no observational constraints on the core mass function and its link to the initial mass function beyond the Milky Way.Here we present a study of the fragmentation properties and the measurement of the core mass function in an external galaxy, focusing on the 30Dor-10 region in the Large Magellanic Cloud, using high resolution observations that probe spatial scales down to 2000 au. Robust statistical analysis demonstrates that the core mass function is consistent with a Salpeter-like slope and suggests that variations in the stellar mass distribution arise from evolutionary processes rather than from initial fragmentation.

The correlation discrete variable representation (CDVR) enables efficient quantum dynamics calculation with the multi-layer multi-configurational time-dependent Hartree approach on general potential energy surfaces. It employs a time-dependent quadrature to compute potential energy matrix elements, thereby eliminating the need to refit the potential to a sum of products form. The non-hierarchical CDVR conserves the inherent symmetry properties of tree-shaped wavefunction representations and drastically reduces the number of grid points compared to the original hierarchical CDVR. However, it requires projection on the space spanned by the single-hole functions at each node of the tree, which can introduce unphysical couplings for unconverged basis sets. In this work, the non-hierarchical CDVR is revisited, and a revised approach that avoids explicit projection on the single-hole space is introduced. The computational costs of the revised approach scale favorably with the number of single-particle functions (SPFs): for a tree with three edges at each node and n SPFs at each edge, an n4 scaling is achieved. Furthermore, a revised scheme that uses artificial SPFs to systematically increase the accuracy of the CDVR quadrature is presented. Computations studying the photodissociation of NOCl, the vibrational states of methyl, and the non-adiabatic quantum dynamics of photoexcited pyrazine demonstrate the accuracy and efficiency of the revised non-hierarchical CDVR. Notably, for the 24-dimensional pyrazine system, the use of the CDVR does not increase the required wall clock time compared to calculations utilizing the sum of products form of the vibronic coupling model.

Macroscopic active matter systems, such as bristle bots, provide a compelling platform for investigating nonequilibrium dynamics at highly visible scales. To fully leverage their accessibility, accurate mathematical models are needed to corroborate experiments. In this work, we study the motion of a free chiral hexbug (Nano-Newton Series) via video tracking and compare the results to theoretical predictions from overdamped Langevin equations for active Brownian circle swimmers (ABCs). We find good agreement between the hexbug's dynamics and ABC model predictions, particularly for the mean-squared displacement and the intermediate scattering function (ISF). Deviations between the hexbug data and the ABC model arise primarily in the short-time behavior of the real-space propagator, where translational noise is most evident. Our results generally support the use of models based on overdamped Langevin equations as a robust framework for describing hexbug motion when the influence of translational noise is negligible. Moreover, they demonstrate the sensitivity of ISF- and propagator-based analyses in characterizing active systems. Our approach opens new avenues toward refining coarse-grained models and advancing the theoretical understanding of macroscopic active systems.