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The electronic structure of the strongly correlated electron system plutonium hexaboride is studied by using single‐particle approximations and a many‐body approach. Imaginary components of impurity Green's functions show that 5fj=5/2 and 5fj=7/2 manifolds are in conducting and insulating regimes, respectively. Quasi‐particle weights and their ratio suggest that the intermediate coupling mechanism is applicable for Pu 5f electrons, and PuB6 might be in the orbital‐selective localized state. The weighted summation of occupation probabilities yields the interconfiguration fluctuation and average occupation number of 5f electrons n5f ~ 5.101. The interplay of 5f–5f correlation, spin‐orbit coupling, Hund's exchange interaction, many‐body transition of 5f configurations, and final state effects might be responsible for the quasiparticle multiplets in electronic spectrum functions. Prominent characters in the density of state, such as the coexistence of atomic multiplet peaks in the vicinity of the Fermi level and broad Hubbard bands in the high‐lying regime, suggest that PuB6 could be identified as a Racah material. Finally, the quasiparticle band structure is also presented. [ABSTRACT FROM AUTHOR]

We show that the GJMS operators of a special Einstein product factor as a composition of second‐ and fourth‐order differential operators. In particular, our formula applies to the Riemannian product Hℓ×Sd−ℓ$H^{\ell } \times S^{d-\ell }$. We also show that there is an integer D=D(k,ℓ)$D = D(k,\ell)$ such that if d⩾D$d \geqslant D$, then for any special Einstein product Nℓ×Md−ℓ$N^\ell \times M^{d-\ell }$, the Green's function for the GJMS operator of order 2k$2k$ is positive. As a result, these products give new examples of closed Riemannian manifolds for which the Q2k$Q_{2k}$‐Yamabe problem is solvable. [ABSTRACT FROM AUTHOR]

Phase field models have been employed extensively in the study of microstructure evolution in materials. Elasticity plays an important role in solid‐state phase transformation processes, and it is usually introduced into phase field models in terms of the elastic strain energy by applying Khachaturyan–Shatalov microelasticity theory. Conventionally, this energy is derived in the reciprocal space and results in full‐space Fourier transformation in practice, which becomes bottle‐neck in large‐scale and massively‐parallel applications. In this article, we propose an error‐controlled approximation algorithm for scalable and efficient calculation of the elastic strain energy in phase field models. We first derive a real‐space convolutional representation of the elastic strain energy by representing the equilibrium displacements in the Khachaturyan–Shatalov microelasticity theory using Green's function. Then we propose an error‐controlled truncation criterion to approximate the corresponding terms in the phase field model. Finally, a carefully designed parallel algorithm is presented to carry out large‐scale simulations. The accuracy and efficiency of the proposed algorithm are demonstrated by real‐world large‐scale phase field simulations. [ABSTRACT FROM AUTHOR]

ABSTRACT The present work proposes a new version of the Green‐FOSM (first‐order second moment) method, which eliminates the iterative calculation process of the original version and, simultaneously, solves the convergence problems related to the mechanical properties of rocks that form the geological formation. In this calculation scheme, the iterative process is eliminated by using a matrix that correlates the nodal displacement vector with the strain vector. Considering the same computational resources, this non‐iterative version of the Green‐FOSM method is up to 200 times faster than the original iterative process. In addition, it allows analyzing problems with more than 10,000 random variables, value that in the original method is less than 3000. To demonstrate its validity, the proposed method is applied to two hypothetical models subjected to different fluid extraction processes. For all the different levels of correlation and spatial variability, the statistical results obtained by the proposed method agree well with the results obtained via Monte Carlo Simulation (MCS). The relationship between CPU times demonstrates that the proposed method is at least 50 times faster than MCS. In the end, the non‐iterative Green‐FOSM method is used to obtain the displacement, strain, and stress fields of a geological section constructed from a seismic image of Brazilian pre‐salt oil region. The results found show that, depending on the levels of spatial variability, the analyzed fields can assume values up to 30.6% higher or lower than the values obtained deterministically. [ABSTRACT FROM AUTHOR]

For the first time, the magnetic and optical (bandgap) properties of co‐doped Mg/Dy, Al/Dy, and Mn/Nd SrFe12O19$\left(\text{SrFe}\right)_{12} \left(\text{O}\right)_{19}$ (SFO) at Sr and Fe sites are investigated using a microscopic model and the Green's function theory. It is shown that the co‐doping at both Sr and Fe sites can change the behavior of the magnetization which decreases by transition metal or nonmagnetic ion doping at the Fe site (with doping ions larger than the host Fe ions), but by additive co‐doping at the Sr site with rare‐earth ion (which ionic radius is smaller than that of Sr) the magnetization increases with increasing the co‐doping concentration. The bandgap energy decreases in the co‐doped SFO. The mechanism of this co‐doping effect is explained on microscopic level. It is due to the changes of the spin‐exchange interaction constants at the doped sites caused by the appearance of different strain by the doping with two ions. The theoretical results are compared with the existing experimental data and are in good qualitative agreement. [ABSTRACT FROM AUTHOR]

In the past few years, the remarkable progress of commercially operated spacecrafts, the success with reusable rocket engines, as well as the international competition to explore space, has led to a substantial acceleration of activities in the design and preparation of ambitious future lunar missions. In the search for ice and/or cavities imaging the shallow subsurface structure is of vital importance. Hereby, previous studies have shown that seismic interferometry is a promising method to investigate the subsurface properties from passive lunar data. In this study, we want to evaluate the potential of this method further by examining the required duration of seismic measurements and the influence of scattering on the Green's function retrieval. Therefore, we applied seismic interferometry to both measured Apollo 17 data and synthetic data. Our findings indicate that, under optimal conditions, a few hours of data are sufficient when using the method of time‐scaled phase‐weighted stack (ts‐PWS). However, this strongly depends on the inter‐station distance, the orientation toward the principal noise sources, and the timing of the measurement during the lunar cycle. Additionally, we were able to reproduce the measured data using numerical simulations in 2D. The synthetic results show that scattering effects clearly influence the Green's function extraction, especially for larger station distances. Key Points: Green's functions are retrieved from passive Apollo 17 data and synthetic data using seismic interferometryThe convergences time of the Green's function depends on inter‐station distance, noise source distribution and timing during the lunar cycleStrong scattering in the lunar regolith influences the Green's function retrieval, especially for larger station distances [ABSTRACT FROM AUTHOR]

The stochastic Green's function method (SGFM), which simulates the source spectra of small earthquakes based on the ω−2 model and follows the scaling law of earthquakes to synthesize into a large earthquake, is a practical ground motion simulation method in areas lacking suitable small earthquake records. However, one of the problems in the application of the SGFM is that the source spectrum synthesized from small earthquakes shows a fall‐off in the mid‐frequency band, as the number of fault divisions of the large earthquake increases. To solve this problem, this study proposes an improved method, which introduces a correction coefficient for the source spectrum according to the ω−2 model and considers the variation of subfault rise time with the rupture process. Taking the 1994 Northridge earthquake as an example, the ground motion simulation results of the improved method are compared with observed records. The results show that only introducing the correction coefficient causes larger amplitude of simulation results than observed records. Only considering the variation of subfault rise time can improve the fall‐off problem to some extent, but the accuracy of ground motion simulation at observation points has no significant improvement. By simultaneously introducing the correction coefficient and considering the variation of subfault rise time, the simulation results are in good agreement with observed records and are able to reproduce the directivity effect at the forward observation points. Therefore, the improved SGFM proposed in this study is an effective and reliable tool for ground motion simulation. Key Points: The problem of source spectrum fall‐off for simulating ground motion using stochastic Green's method was pointed outAn improved method introducing a correction coefficient and considering the variation of subfault rise time simultaneously was proposedThe effectiveness of improved method was verified by comparison of the simulated and observed results of the 1994 Northridge earthquake [ABSTRACT FROM AUTHOR]

Astrophysical accretion discs that carry a significant mass compared with their central object are subject to the effect of self‐gravity. In the context of circumstellar discs, this can, for instance, cause fragmentation of the disc gas, and—under suitable conditions—lead to the direct formation of gas‐giant planets. If one wants to study these phenomena, the disc's gravitational potential needs to be obtained by solving the Poisson equation. This requires to specify suitable boundary conditions. In the case of a spherical‐polar computational mesh, a standard multipole expansion for obtaining boundary values is not practicable. We hence compare two alternative methods for overcoming this limitation. The first method is based on a known Green's function expansion (termed "CCGF") of the potential, while the second (termed "James' method") uses a surface screening mass approach with a suitable discrete Green's function. We demonstrate second‐order convergence for both methods and test the weak scaling behavior when using thousands of computational cores. Overall, James' method is found superior owing to its favorable algorithmic complexity of ∼On3$$ \sim \mathcal{O}\left({n}^3\right) $$ compared with the ∼On4$$ \sim \mathcal{O}\left({n}^4\right) $$ scaling of the CCGF method. [ABSTRACT FROM AUTHOR]

How substituents affect the conductance of single‐molecule junctions has been a subject of ongoing debate. Here, a comparative study on the transport properties across a broader range of experimentally proposed and representative π‐conjugated molecular systems, each characterized by prototypical backbone motifs with distinct terminal groups and featuring a range of substituents is conducted. Employing the non‐equilibrium Green's function method within density functional theory, this investigation reveals a significant impact on junction conductance due to asymmetric characteristics arising from both electronic and spatial effects induced by the di‐substituents of phenanthrene analogs with C═C or B─N motifs. Remarkably, a linear correlation is uncovered, either negative or positive, between the dipole moment of the molecules and the junction conductance, contingent upon whether the transport is governed by the highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO) states. Furthermore, the validity of this proposed dipole moment descriptor is substantiated across various substituted series, including 2,7‐dipyridylfluorene, oligo(phenylene ethynylene), and 1,4‐diaminobenzene. These findings underscore the pivotal role of individual molecular dipole moment, easily determinable, in offering precise predictive insight into the conductance of intricate molecular junctions. [ABSTRACT FROM AUTHOR]

The competition between superconductivity and magnetism has been studied for the ongoing investigation of mechanisms in unconventional superconductors. Fe1+yTe1−xSex is distinct among iron‐based superconductors due to its structural simplicity, comprising solely FeTe/Se layers that are favorable for probing the superconductivity mechanism. The main goal of this article is to focus on the computational investigation of the interplay of magnetism and superconductivity in the Fe1+yTe1−xSex multiband superconductor. From the electronic structure of the Fe1+yTe1−xSex superconductor, a two‐band Hamiltonian model was considered to examine the interplay of magnetism and superconductivity in the Fe1+yTe1‐xSex superconductor. Using Green's function formalism with the Hamiltonian model, the mathematical statements for the superconducting (Sc) gap parameter, spin density wave (SDW) ordering parameter, Sc and magnetic transitional temperatures have been obtained. Using these mathematical expressions, the phase diagram of transition temperatures versus the gap parameters for the Fe1+yTe1‐xSex superconductor has been plotted. The intersection region in the phase diagram of transition temperatures as a function of the SDW order parameter has been plotted to show the possible interplay of superconductivity and magnetism in a Fe1+yTe1‐xSex iron‐based superconductor. [ABSTRACT FROM AUTHOR]

Herein, a highly practical first‐principles approach for studying phonon transport across various materials, ranging from low‐dimensional systems to three‐dimensional bulk structures, as well as nanostructures, is presented. This method integrates the nonequilibrium Green's function (NEGF) formalism with ab initio calculations of dynamical matrices generated by Quantum Espresso. A detailed technical approach for extracting atomistic force constants and forming dynamical matrices that adhere to the tri‐diagonal technique within the NEGF framework is provided. Additionally, an efficient method for constructing dynamical matrices of conventional cells from those of primary cells is introduced, remarkably reducing the computational costs associated with density‐functional theory calculations. The robustness and applicability of this methodology are validated through several case studies. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the existence and uniqueness of solutions for a sixth‐order differential equation involving nonlocal and integral boundary conditions. Firstly, we obtain the properties of the relevant Green's functions. The existence result of at least one nontrivial solution is obtained by applying the Krasnoselskii–Zabreiko fixed point theorem. Moreover, we also establish the existence of unique solution to the considered problem via Hölder and Minkowski inequalities and Rus's theorem. Finally, two numerical examples are included to show the applicability of our main results. [ABSTRACT FROM AUTHOR]

In this article, we propose novel coupled nonlinear singular boundary value problems arising in epitaxial growth theory. The coupled equations are nonlinear, non‐self‐adjoint, and singular and have no exact solutions. We derive some qualitative properties of the coupled solutions, which depend on the size of parameters that occur in the coupled system. To prove the existence of the coupled solutions, we apply the monotone iterative technique on equivalent coupled integral equations in the presence of upper and lower solutions. We also compute the bounds for the parameters, which indicates the existence of coupled solutions for small values of the parameters, and nonexistence for large positive values of these parameters. To illustrate the theory developed, we consider test cases and compute the sequence of upper and lower solutions. To verify the bounds on the parameters, we have used a type of Adomian decomposition method. [ABSTRACT FROM AUTHOR]

The problem of the existence and uniqueness of solutions of boundary value problems (BVPs) for a nonlinear fractional differential equation of order 2<α ≤ 3 is studied. The BVP is transformed into an integral equation and discussed by means of a fixed point problem for an integral operator. Conditions for the existence and uniqueness of a fixed point for the integral operator are derived via b‐comparison functions on complete b‐metric spaces. In addition, estimates for the convergence of the Picard iteration sequence are given. An estimate for the Green's function related with the problem is provided and employed in the proof of the existence and uniqueness theorem for the solution of the given problem. Illustrative examples are presented to support the theoretical results. [ABSTRACT FROM AUTHOR]

We establish the existence and qualitative behavior of positive continuous solutions to some nonlinear singular fractional differential equation in the frame of conformable fractional derivative. To this end, we combine estimates on the Green's function and a fixed point argument. Some examples are given to illustrate the applicability of our main result. [ABSTRACT FROM AUTHOR]

This work proposes a novel mathematical model based on the Galerkin time‐domain boundary element method for accurately calculating the lightning current distribution and lightning impulse response of the buried substation grounding grid, in a multi‐layer horizontal layered soil model, by taking into account the soil ionization effect. To improve computational efficiency, the quasi‐static complex image method and its closed form time‐domain Green's function have been introduced into the model that has the ability to analytically calculate the mutual inductance coefficient between the branch currents of any two conductor segments and the mutual resistance coefficient between the leakage currents. The Galerkin time‐domain boundary element method proposed in this work can simulate the transient lightning impulse response of a substation grounding grid buried in the multi‐layer horizontal layered soil. [ABSTRACT FROM AUTHOR]

Using density functional theory combined with nonequilibrium Green's function, the electronic structures and carrier transport properties of the orthorhombic phase boron nitride nanoribbons (BNNRs) with different edges and different widths are investigated. The calculated results show that both armchair‐ and zigzag‐edged BNNRs are direct bandgap semiconductors. The quantum confinement gives rise to a distinct bandgap for the 1D BNNRs, and the edged atoms play an important role on their electronic structures. The bandgaps of the armchair‐edged BNNRs approach 0.5–0.8 eV when their widths are sufficiently large. However, the electronic structures of the zigzag‐edged BNNRs exhibit more variations dependent on their edged atoms. The J–V characteristics of the BNNRs reveal that the zigzag‐edged BNNRs have superior J–V performance to that of the armchair‐edged counterparts. Eventually, a computational nanodevice design is proposed to achieve rectifying behavior by constructing an in‐plane heterojunction based on the BNNRs without any doping, and the left and right electrodes are formed by differently edged atoms and a small strain is performed on the left electrode. The rectification ratio of about 77.36 is realized. The findings provide comprehensive understandings of the orthorhombic BN monolayer, which can be helpful to its potential application for nanoelectronics. [ABSTRACT FROM AUTHOR]

This article aims to compare the so‐called iterated perturbation theory (IPT) and auxiliary master equation approach (AMEA) impurity solvers for a Mott insulating system driven out of equilibrium by a static electric field. Electronic heat bath and optical phonons are employed as dissipation mechanism of the current‐induced Joule heat that the excited electrons of the lattice experience as the result of the field's driving. Despite its simplicity, the IPT approach yields results that qualitatively are in good agreement with those obtained within the AMEA impurity solver, although fails to reproduce some correlation effects. [ABSTRACT FROM AUTHOR]

The electrical conductivity σ and magnetization M of KBiFe2O5$\left(\text{KBiFe}\right)_{2} \left(\text{O}\right)_{5}$ (KBFO) nanoparticles (NPs) are systematically examined using a microscopic model and Green's function theory. KBFO is characterized by a narrow bandgap and relatively weak electrical conductivity σ, which presents a problem in carrier transportation and collection. Therefore, ways to enhance σ are found. The first is reducing the NP size. The second one is doping at the Fe and Bi sites with different ions which cause a compressive strain, that is, their ionic radius is smaller than that of the host ion. It is shown that doping with Al at the Fe site as well as with Ru or La ions at the Bi site leads to enhancing the electrical conductivity σ. The magnetization M increases with increasing concentration of all dopants. [ABSTRACT FROM AUTHOR]

Herein, analytical modeling of Fe3O4/x(≈1.1 nm)/Co (x = rubrene, C60, and bathocuproine (BCP)) magnetic tunnel junctions (MTJs) has been performed using rubrene, C60, and BCP as organic spacer layers. The simulation is considered as nonequilibrium Green's function assuming spin precession at ferromagnet/organic semiconductor (FM/OSC) interface defect states. The voltage‐dependent resistances for both parallel (RP) and antiparallel (RAP) orientations have been observed to be dependent on spin injection from FM/OSC defect states. Pinning well‐dependent defect state depths have been associated with band misalignment‐induced lattice distortion at FM/OSC interface of the devices. The large tunnel magnetoresistance (TMR) response for rubrene‐based MTJ device has been attributed to a higher change of FM/OSC defect state depths with voltage. High TMR may have reduced spin torque‐dependent spin precession, leading to lower spin transfer torque for the rubrene device. Hence, engineering of defect states at the FM/OSC interface may lead to the successful realization of enhanced TMR in organic spacer MTJs for high‐performance spintronic memory applications. [ABSTRACT FROM AUTHOR]

The theory of nonequilibrium Green functions (NEGF) has seen a rapid development over the recent three decades. Applications include diverse correlated many‐body systems in and out of equilibrium. Very good agreement with experiments and available exact theoretical results could be demonstrated if the proper selfenergy approximations were used. However, full two‐time NEGF simulations are computationally costly, as they suffer from a cubic scaling of the computation time with the simulation duration. Recently the G1–G2 scheme that exactly reformulates the generalized Kadanoff–Baym ansatz with Hartree–Fock propagators (HF‐GKBA) into time‐local equations is introduced, which achieves time‐linear scaling and allows for a dramatic speedup and extension of the simulations (Schluenzen et al. Phys. Rev. Lett. 2020, 124, 076601). Remarkably, this scaling is achieved quickly, and also for high‐level selfenergies, including the nonequilibrium GW and T‐matrix approximations (Joost et al. Phys. Rev. B 2020, 101, 245101). Even the dynamically screened ladder approximation is now feasible (Joost et al. Phys. Rev. B 2022, 105, 165155), and also applications to electron‐boson systems are demonstrated. Herein, an overview on recent results that are achieved with the G1–G2 scheme is presented. Problems and open questions are discussed and further ideas of how to overcome the current limitations of the scheme and present are presented. The G1–G2 scheme is illustrated by presenting applying it to the excitation dynamics of Hubbard clusters, to optical excitation of graphene, and to charge transfer during stopping of ions by correlated materials. [ABSTRACT FROM AUTHOR]

Due to their conceptual appeal and computational convenience, two‐level systems (TLSs) and generalizations are used to investigate nonlinear behavior in quantum optics and assess the applicability of theoretical methods. Herein, the focus is on second‐harmonic generation (SHG) and, as system of interest, on the Dicke model, which consists of several TLSs inside an optical cavity. The main aspect addressed is the scope of nonequilibrium Green's function (NEGF) to describe the effect of inhomogeneities and electron–electron (e–e) interactions on the SHG signal. For benchmarking purposes, exact diagonalization (ED) results are also presented and discussed. SHG spectra obtained with NEGF and ED are found to be in very good mutual agreement in most situations. Furthermore, inhomogeneity in the TLS and e–e interactions reduce the SHG signal, and the reduction is stronger with inhomogeneity than with interactions. This trend is consistently noted across different (small to large) system sizes. Finally, a modified NEGF approach is proposed to account for cavity leakage, where the quantum photon fields are coupled to a bath of classical oscillators. As expected, within this mixed quantum‐classical scheme, a decrease in the intensity of the fluorescent spectra takes place depending on the entity of leakage. [ABSTRACT FROM AUTHOR]

Correlated quantum many‐particle systems out of equilibrium are of high interest in many fields, including correlated solids, ultracold atoms, or dense plasmas. Accurate theoretical description of these systems is challenging both, conceptionally and with respect to computational resources. A quantum fluctuations approach is recently presented, which is equivalent to the nonequilibrium GW approximation that promises high accuracy at low computational cost. The method exhibits process time scaling that is linear in the number of time steps, like the G1–G2 scheme, however, at a much reduced computer memory cost. In a second publication, this approach is extended to the two‐time exchange–correlation functions and the dynamic density response properties. Herein, the properties of this approach are analyzed in more detail. The physical meaning of the central approximation, the quantum polarization approximation, is established. It is demonstrated that the method is equivalent to the Bethe–Salpeter equation for the two‐time exchange–correlation function when the generalized Kadanoff–Baym ansatz with Hartree–Fock propagators is applied. [ABSTRACT FROM AUTHOR]

In this work, the study of the spectral properties of an open interacting system by solving the generalized Kadanoff‐Baym ansatz (GKBA) master equation for the single‐particle density matrix, namely the time‐diagonal lesser Green's function, is reported. To benchmark its validity, the solution obtained within the GKBA is compared with the solution of the Dyson equation at stationarity. In both approaches, the interaction is treated within the self‐consistent second‐order Born approximation, whereas the GKBA still retains the retarded propagator calculated at the Hartree–Fock (HF) and wideband limit approximation level. The model chosen is that of two leads connected through a central correlated region where particles can interact and utilize the stationary particle current at the boundary of the junction as a probe of the spectral features of the system. The central region is chosen as the simplest model featuring a degenerate ground state with a flat band. The main result is that the solution of the GKBA master equation captures well the spectral feature of such system and specifically the transition from dispersionless to dispersive behavior of the flat band as the interaction is increased. Therefore, the GBKA solution retains the main spectral features of the self‐energy used even when the propagator is at the HF level. [ABSTRACT FROM AUTHOR]

Electron dynamics in a two‐sites Hubbard model is studied using the nonequilibrium Green's function approach. The study is motivated by the empirical observation that a full solution of the integro‐differential Kadanoff–Baym equation (KBE) is more stable and often accompanied by artificial damping [Marc Puig von Friesen, C. Verdozzi, and C.‐O. Almbladh (2009)] than its time‐linear reformulations relying on the generalized Kadanoff–Baym ansatz (GKBA). Additionally, for conserving theories, numerical simulations suggest that KBE produces natural occupations bounded by one and zero in agreement with the Pauli exclusion principle, whereas, in some regimes, GKBA‐based theories violate this principle. As the first step for understanding these issues, the electron dynamics arising in the adiabatic switching scenario is studied. Many‐body approximations are classified according to the channel of the Bethe–Salpeter equation in which electronic correlations are explicitly treated. They give rise to the so‐called second Born, T‐matrix, and GW approximations. In each of these cases, the model is reduced to a system of ordinary differential equations, which resemble equations of motion for a driven harmonic oscillator with time‐dependent frequencies. A more complete treatment of electronic correlations is achieved by combining different correlation channels, with parquet theory serving as a starting point. [ABSTRACT FROM AUTHOR]

The interaction of electrons with quantized phonons and photons underlies the ultrafast dynamics of systems, ranging from molecules to solids, giving rise to a plethora of physical phenomena experimentally accessible using time‐resolved techniques. Green's function methods offer an invaluable interpretation tool since scattering mechanisms of growing complexity can be selectively incorporated in the theory. Cheers is a general‐purpose nonequilibrium Green's function code that implements virtually all known many‐body approximations and is designed for first‐principles studies of ultrafast processes in molecular and model solid‐state systems. The aims of generality, extensibility, efficiency, and user friendliness of the code are achieved through the underlying theory development and the use of modern software design practices. Herein, the necessity for the creation of such a code is motivated and its design and capabilities are overviewed. [ABSTRACT FROM AUTHOR]

Ultrawideband (UWB) time‐reversal techniques are widely used in microwave imaging systems to detect and localize breast tumors. Measuring the scattering electromagnetic fields from a breast phantom can be time‐reversed and back‐propagated to refocus on a tumor. In this study, a Debye model was applied to the breast phantom. Using the decomposition of the time‐reversal operator (TR‐DORT), images were obtained in the UWB frequency range of 3.1–10.6 GHz. The conventional TR imaging method employs the free‐space Green's function to refocus on the tumor, which degrades refocusing in a lossy and dispersive breast phantom. We propose the use of the cylindrical dyadic Green's function in a three‐layer medium for TR imaging. The excitation system consists of a circular array of spiral antennas. The imaging results of the proposed Green's function in TR‐DORT were subsequently calculated, indicating successful tumor detection in different application scenarios of the lossy and dispersive breast phantom. [ABSTRACT FROM AUTHOR]

High‐resolution seismic model is crucial for advancing our understandings on geological processes and enhancing seismic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) in the top 100 km of the crust and uppermost mantle in continental China following a top‐down construction process. The employed seismic constraints include P‐wave polarization angle from tele‐seismic event, short‐period Rayleigh wave ellipticity from ambient noise, long‐period Rayleigh wave ellipticity from earthquake data, receiver function, empirical Green's function from ambient noise, Rayleigh wave phase/group velocity dispersion curves from regional earthquakes, and Pn‐wave travel time extracted from seismic data of 4,435 stations. CSRM‐1.0 has a spatial crustal resolution of ∼60 km beneath the north‐south seismic belt and trans‐North China orogen regions and ∼120 km beneath the rest of continental China, and a spatial mantle resolution of ∼300 km. CSRM‐1.0 exhibits prominent velocity heterogeneities in the crust and uppermost mantle and an eastward thinning of the crust, geographically correlating with geological settings. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Plain Language Summary: High‐resolution seismic imaging of the crust and uppermost mantle offers crucial insights into regional geological histories and enhances seismic and volcanic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) of the crust and mantle beneath continental China with various types of seismic constraints extracted from seismic data recorded by 4,435 stations deployed across continental China since 1990. CSRM‐1.0 has a spatial resolution of ∼60–120 km in the crust and 300 km in the uppermost mantle. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Key Points: CSRM‐1.0 is constructed with various seismic constraints from data of 4,435 stations using a self‐consistent top‐down construction processCSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution, and enhanced model accuracyCSRM‐1.0 reveals major crustal mafic rocks related to the past subductions, an Emeishan mantle plume and geological inter‐block boundaries [ABSTRACT FROM AUTHOR]

We study the Cauchy problem for the three‐dimensional isentropic compressible Navier–Stokes/Allen–Cahn system, which models the phase transitions in two‐component patterns interacting with a compressible fluid. Under the assumption that the initial perturbation is small and decays spatially, we establish the global existence and the pointwise behavior of strong solutions to this nonconserved system. To deal with the source terms involving the phase variable, we employ the Green's function and space‐time weighted estimates. The analysis shows that the phase variable mainly contains the diffusion wave with exponential decaying amplitude over time, and consequently the density and momentum of the compressible fluid adhere to a generalized Huygens principle. [ABSTRACT FROM AUTHOR]

Two‐dimensional materials exhibit significant potential and wide‐ranging application prospects owing to their remarkable tunability, pronounced quantum confinement effects, and notable surface sensitivity. The switching, optoelectronics, and gas‐sensitive properties of the new carbon material poly‐cyclooctatetraene framework (PCF)‐graphene were systematically studied using density functional theory combined with the nonequilibrium Green's function method. First, the diode device based on PCF‐graphene monolayer exhibited an impressive switching ratio of 106, demonstrating excellent diode characteristics. Moreover, in the investigation of the pin junction utilizing monolayer PCF‐graphene, it is noteworthy that significant photocurrent responses were observed in both the zigzag and armchair directions, specifically within the visible and ultraviolet regions. Finally, gas sensors employing monolayer and bilayer PCF‐graphene demonstrate significant chemical adsorption capabilities for NO and NO2. Notably, the maximum gas sensitivity for NO is achieved in monolayer PCF‐graphene, reaching 322% at a bias voltage of 1.0 V. Meanwhile, for bilayer PCF‐graphene‐based gas sensor, the maximum gas sensitivity reaches 52% at a bias voltage of 0.4 V. In addition, the study also examined the influence of various environmental conditions, specifically H2O, O, and OH, on the system under investigation. The obtained results emphasize the multifunctional properties of PCF‐graphene, exhibiting significant potential for various applications, including switching devices, optoelectronic devices, and gas sensors. [ABSTRACT FROM AUTHOR]

Solving the inverse problems of heat conduction often requires performing a very large number of Green's function evaluations. This paper addresses the calculation of Green's functions in anisotropic curved media, such as composite lamina, where the principal axes of thermal conductivity follow the curved surface. We start with established exact series solutions for cylindrical convex and concave shapes. These solutions are extended to accommodate geometries of real‐world composite materials that do not form a closed surface like a cylinder. Unfortunately, the exact solutions have the form of an infinite series of sums or integrals and are computationally infeasible for the inverse problems of interest, especially for large radii of curvature. This motivates a perturbation solution that is accurate and computationally efficient at large radii of curvature. In addition, it motivates a phenomenological approximation that is extremely computationally efficient over a broad range of curvatures, but with some sacrifice in accuracy. These solutions are compared with exact solutions, with each other, and with numerical finite difference calculation. We identify regions in parameter space where the different approaches are preferable and where they lead to the same numerical result. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) emissions affect local temperature; quantifying that local response is important for learning about the earth system, the impacts of mitigation, and adaptation needs. We assume the climate system can be represented as a time‐dependent linear system, diagnosing Green's Functions for the spatial temperature response to CO2 emissions based on CMIP6 earth system models. This allows us to emulate the linear component of the temperature response to CO2. This approach is sufficient to capture the spatial temperature response of CMIP6 experiments within one standard deviation of the multimodel spread across most regions, though accuracy is lower in the Southern Ocean and the Arctic. Our approach reveals where nonlinear feedbacks are important in current CMIP6 models, and where the local system response is well represented by a time‐dependent linear differential operator. It incorporates emissions path dependency and may be useful for evaluating large ensembles of emission scenarios. Plain Language Summary: Carbon dioxide (CO2) emissions impact surface temperature. It is well established that the global mean temperature change is proportional to the cumulative emissions of CO2. This has led to the creation of carbon budgets to reach temperature goals. We test this relationship at the spatio‐temporal scale, quantifying a simple approach that estimates the local temperature response to CO2 emissions alone. We use an approach built from the Climate Model Intercomparison Project Phase 6 (CMIP6) Earth System Models, based on the concept that an additional unit of CO2 can be scaled for larger emissions and summed over time to estimate cumulative impacts. We evaluate this with additional CMIP6 experiments, showing that this approach captures the temperature response in most locations with lower accuracy in the Arctic and Southern Ocean. This type of approach may be useful to evaluate many policy scenarios and to better understand earth system processes that are represented in the models, as it takes around one second to quantify 90 years' worth of temperature change on a local computer, while Earth System Models can require weeks of runtime on supercomputers. Key Points: With a Green's Function approach, we emulate the linear component of the spatially resolved temperature response to CO2 emissionsWe reproduce the temperature response well within multi‐model uncertainty except in the Arctic and Southern OceanThis approach allows expedient quantification of the spatial and temporal temperature response to varying CO2 emissions pathways [ABSTRACT FROM AUTHOR]

By directly solving the full two‐way wave equation, reverse time migration has superiority over other imaging algorithms in handling steeply dipping structures and other complicated geological models. Moreover, by incorporating the asymptotic inversion operator into reverse time migration imaging condition, the imaging algorithm is able to give a quantitative estimation of parameter perturbation in high‐frequency approximation sense. However, because conventional asymptotic inversion only accounts for geometrical spreading, uneven illumination due to irregular acquisition geometry and inhomogeneous subsurface at each image point is neglected. The omit of illumination compensation significantly affects the imaging quality. Wave‐equation‐based illumination compensation methods have been extensively studied in the past. However, the traditional wave‐equation‐based illumination compensation methods usually require high computational cost and huge storage. In this paper, we propose an efficient wave‐equation‐based illumination compensation method. Under high‐frequency approximation, we first define a Jacobian determinant to measure the regularity of subsurface illumination, and then illumination compensation operators are proposed based on the Jacobian. Through boundary integration, we further express the illumination compensation operators through extrapolated wavefields; the explicit computation of asymptotic Green's functions is thus avoided, and an efficient illumination compensation implementation for reverse time migration is achieved. Numerical results with both synthetic and field data validate the effectiveness and efficiency of the presented method. [ABSTRACT FROM AUTHOR]

The array‐based frequency‐Bessel transform method has been demonstrated to effectively extract dispersion curves of higher‐mode surface waves from the empirical Green's functions (EGFs) of displacement fields reconstructed by ambient noise interferometry. Distributed acoustic sensing (DAS), a novel dense array observation technique, has been widely implemented in surface wave imaging to estimate subsurface velocity structure in practice. However, there is still no clear understanding in theory about how to accurately extract surface‐wave dispersion curves directly from DAS strain (or strain rate) data. To address this, we extend the frequency‐Bessel transform method by deriving Green's functions (GFs) for horizontal strain fields, making it applicable to DAS data. First, we test its performance using synthetic GFs and verify the correctness of extracted dispersion spectrograms with theoretical results. Then, we apply it to three field DAS ambient‐noise data sets, two recorded on land and one in the seabed. The reliability and advantages of the method are confirmed by comparing results with the widely used phase shift method. The results demonstrate that our extended frequency‐Bessel transform method is reliable and can provide more abundant and higher‐quality dispersion information of surface waves. Moreover, our method is also adaptable for active‐source DAS data with simple modifications to the derived transform formulas. We also find that the gauge length in the DAS system significantly impacts the polarity and value of extracted dispersion energy. Overall, our study provides a theoretical framework and practical tool for multimodal surface wave dispersion measurement using DAS data. Plain Language Summary: Ambient noise surface wave imaging is one of the most widely used methods for estimating the Earth's internal shear wave velocity structure, exploiting the dispersion characteristics of surface waves. The array‐based frequency‐Bessel transform method has been proven effective in extracting dispersion curves of higher‐mode surface waves from empirical Green's functions (EGFs) retrieved via ambient noise interferometry. Distributed acoustic sensing (DAS), which is a novel dense array observation technique, has become widely adopted in practical surface wave imaging. Nevertheless, there remains a theoretical gap in our understanding of how to accurately extract surface‐wave dispersion curves directly from DAS strain (or strain rate) data. To bridge this gap, starting from the perspective of strain field theory, we propose an extension of the frequency‐Bessel transform method, which can account for Green's functions of horizontal strain fields and the reconstructed EGFs from DAS ambient noise data. Both synthetic tests and applications to field DAS data demonstrate that our proposed frequency‐Bessel transform method can be confidently and effectively utilized for multimodal dispersion measurement of surface waves derived from DAS observation data. This work can offer a theoretical basis and practical tool for DAS‐based surface wave imaging. Key Points: We derive Green's functions for horizontal strain fields, extending the frequency‐Bessel transform method for applications in distributed acoustic sensing (DAS) dataThe extended frequency‐Bessel transform method reliably measures multimodal surface‐wave dispersion in both synthetic and field DAS recordsThe method excels in extracting high‐quality multimodal dispersion information from both active and passive DAS data for surface waves [ABSTRACT FROM AUTHOR]

During electro‐osmotic consolidation, effective voltage attenuation induced by the increasing interface resistance is an important phenomenon, which significantly decreases consolidation effectiveness. This paper presents an analytical model for one‐dimensional electro‐osmotic consolidation in layered soils with horizontal graphite electrodes considering effective voltage attenuation. The mathematical model is characterized by time‐dependent source term and discontinuous interface flux. New variables are introduced to homogenize the discontinuous interface flux and Green's function method is used to solve the new nonhomogeneous governing equations with nonhomogeneous boundaries. Several verification examples are conducted using the existing analytical solution and numerical results. Parametric studies indicate that electro‐osmotic consolidation of layered soils cannot be accurately simulated by equivalent homogeneous soil, whether effective voltage attenuation is considered or not. Furthermore, the backflow phenomenon may occur due to effective voltage attenuation, while it may disappear when the anode is placed in the low‐permeability layer. In addition, the optimal arrangement of electrodes in layered soils is also investigated. When the ratio of the thickness of low‐permeability layer to high‐permeability layer is about 1/3, installing the cathode in the low‐permeability layer can improve the electro‐osmosis effect up to two times, compared with installing the anode in the low‐permeability layer. [ABSTRACT FROM AUTHOR]

Employing the constructs of density functional theory (DFT) and the Nonequilibrium Green's Function (NEGF), the investigation extensively explores the electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) doped with vanadium (V). Notably, this inquiry unveils that strategic doping can transform V‐doped ZGNRs into spintronic nanodevices with distinctive transport attributes. Initially, the simulations showcase remarkably high spin‐filtering efficiencies (SFEs) at certain bias voltages. Furthermore, a giant magnetoresistance (GMR) peaking at 6.87 ×$\times$ 103$^3$ is detected. In conclusion, the examination discerns a spin rectifier that exhibits a significant rectification ratio (RR) of 9.62 ×$\times$ 102$^2$. This research delineates a viable trajectory for the refinement of high‐performance spintronics in ZGNRs via vanadium doping. The implications of this study indicate that the model harbors considerable promise for application in miniature spintronic devices. [ABSTRACT FROM AUTHOR]

Generating fully spin‐polarized currents (FSPC) and pure spin currents (PSC) are of great importance for spintronics. Half‐metallic ferromagnets, which generate 100% spin polarization, are considered as one of the most promising materials for applications in spintronics. However, the knowledge of intrinsic half‐metallic materials in the spin‐dependent photogalvanic effect is still poorly understood. Using first‐principle transport calculations, a robust approach is introduced to obtain FSPC and PSC by spin‐dependent photogalvanic effect in intrinsic half‐metallic materials. Based on the recently synthesized monolayer half‐metallic C(CN)3, a 2D spin photogalvanic device is built and it is demonstrated that the FSPC can be achieved in a wider photon energy range under both linearly and elliptically polarized light due to the half‐metallicity. It is intriguing to note that the device can be easily manipulated to transition between two modes: one for generating FSPC and another for generating PSC by setting the two leads in anti‐parallel configurations. Furthermore, a significant spin‐valve effect can be attained across various photon energies for both linearly and elliptically polarized light. The research shows that half‐metallic materials are an ideal platform for studying and generating FSPC and PSC, which presents a remarkable avenue for the development of advanced spintronic devices in the next generation. [ABSTRACT FROM AUTHOR]

This article utilizes first‐principles calculations within the density functional theory framework, employing spin generalized gradient approximation, to investigate the spin polarization of arsenic nitride nanotubes (AsNNTs). It is found that AsNNT does not exhibit spin polarization and has a bandgap of 1.05 eV, indicating that it is a semiconductor. Decoration with C, O, Ge, and Se on AsNNT induces spin polarization, resulting in magnetic moments of 1.001, 0.916, 0.770, and 0.967 μB, respectively. Meanwhile, all decorated configurations exhibit narrow bandgap semiconductor properties. Furthermore, the nonequilibrium Green's function method is used to study the spin‐polarized current of AsNNT decorated with C, O, Ge, and Se. It is found that AsNNTs decorated with C, Ge, and Se have relatively small spin current values. Notably, the Se‐decorated AsNNT exhibits the highest degree of spin polarization, with the spin current being nearly fully polarized. [ABSTRACT FROM AUTHOR]

Electromagnetic ion cyclotron (EMIC) waves are a key plasma mode affecting radiation belt dynamics. These waves are important for relativistic electron losses through scattering and precipitation into Earth's ionosphere. Although theoretical models of such resonant scattering predict a low‐energy cut‐off of ∼1 MeV for precipitating electrons, observations from low‐altitude spacecraft often show simultaneous relativistic and sub‐relativistic electron precipitation associated with EMIC waves. Recently, nonresonant electron scattering by EMIC waves has been proposed as a possible solution to the above discrepancy. We employ this model and a large database of EMIC waves to develop a universal treatment of electron interactions with EMIC waves, including nonresonant effects. We use the Green's function approach to generalize EMIC diffusion rates foregoing the need to modify existing codes or recompute empirical wave databases. Comparison with observations from the electron losses and fields investigation mission demonstrates the efficacy of the proposed method for explaining sub‐relativistic electron losses by EMIC waves. Plain Language Summary: Precipitation of energetic electrons from the equatorial magnetosphere to the Earth's ionosphere plays a crucial role in the dynamics of the radiation belt and ionosphere ionization. Such precipitation is primarily driven by wave‐particle interactions. However, accurately modeling these interactions requires precise knowledge of the electron energy ranges which is affected by different wave modes present in the equatorial magnetosphere. A notable challenge arises from the contradiction between model‐predicted energy ranges of electron precipitation by electromagnetic ion cyclotron (EMIC) waves and the energies observed by spacecraft during such precipitation events. By combining a new theoretical approach with detailed observational data sets of these waves, we successfully resolved this contradiction, offering a powerful tool for the simulation of electron precipitation driven by EMIC waves. Key Points: We provide a statistical model of nonresonant electron scattering by electromagnetic ion cyclotron wavesWe show the main wave and electron parametric regions where nonresonant effects can be important for electron precipitationWe derive an analytical approximation allowing generalization of the quasi‐linear diffusion rates including nonresonant effects [ABSTRACT FROM AUTHOR]

Near‐term projections of drought in the southwestern United States (SWUS) are uncertain. The observed decrease in SWUS precipitation since the 1980s and heightened drought conditions since the 2000s have been linked to a cooling sea surface temperature (SST) trend in the Equatorial Pacific. Notably, climate models fail to reproduce these observed SST trends, and they may continue doing so in the future. Here, we assess the sensitivity of SWUS precipitation projections to future SST trends using a Green's function approach. Our findings reveal that a slight redistribution of SST leads to a wetting or drying of the SWUS. A reversal of the observed cooling trend in the Central and East Pacific over the next few decades would lead to a period of wetting in the SWUS. It is critical to consider the impact of possible SST pattern trends on SWUS precipitation trends until we fully trust SST evolution in climate models. Plain Language Summary: Precipitation trends in the southwestern United States (SWUS) are sensitive to the pattern of sea surface temperature (SST) trends in the Tropical Pacific. Since the turn of the century, a decrease in SWUS precipitation has been linked to a cooling of the Central and Eastern Pacific (1990–2020). Notably, climate models are unable to simulate this observed cooling SST trend. In this study, we answer how SWUS precipitation projections may be impacted by potential error in the simulation of future SST trends by climate models. We first demonstrate that slight changes in the pattern of SST trends leads to either a wetting or drying of the SWUS. Second, if the current 30‐year cooling trend in the Central and East Pacific switches to a warming trend, the SWUS could experience a near‐term increase in precipitation. While climate models are the main tool to predict the global response to anthropogenic climate change, we must consider and account for their error in projections of global warming. Key Points: The observed Equatorial Pacific cooling trend, unpredicted by climate models, may have led to decreased precipitation in the southwestern USWith a sea surface temperature‐precipitation Green's function, we find that small changes in sea surface temperature can either wet or dry the southwestern USA reversal of the cooling trend in the Equatorial Pacific could lead to a wetting trend in the southwestern US [ABSTRACT FROM AUTHOR]

In previous methods for solving the equivalent resistance of large‐scale complex resistive networks, abstract Green's functions or complex matrix transformations were often involved, which brought more difficulties to the readers' understanding. For this reason, this study proposed an innovative method based entirely on simple algebraic operations. This method combined the equivalent decomposition method with the improved recursion‐transform (IRT) method. It was divided into three steps: Firstly, by introducing the concept of “negative resistance,” one of the resistors of the network to be solved was equivalently decomposed into the parallel connection of three resistors, so that the whole resistive network was equivalently decomposed into three parts, namely, a left network, a middle network, and a right network. Then, the equivalent resistances of the left network and the right network were calculated using the IRT method, respectively. Finally, the equivalent resistance between any nodes was solved according to the parallel relationship of the equivalent resistances of the left network, the middle network, and the right network. The equivalent resistance between any nodes in the 2 × 4 × n tower‐shaped cascaded resistive network was successfully solved using this method. The calculation showed that because the concept of negative resistance was introduced in this method, the equivalent resistance problem of any nodes in the network was changed into the equivalent resistance problem of the initial nodes of the network, which made the equivalent resistance problem of any nodes simple, convenient, fast and easy to understand. [ABSTRACT FROM AUTHOR]

The functional integral formulation of the Hubbard model when treated in its Kotliar‐Ruckenstein representation in the radial gauge involves fermionic, as well as complex and radial slave boson fields. In order to improve on the understanding of the interplay of the three types of fields, and on the nature of the latter, a comprehensive investigation of an exactly solvable two‐site cluster is performed, as it entails all pitfalls embodied in this approach. It is first shown that the exact partition function is recovered, even when incorporating in the calculation the square root factors that are at the heart of the representation, when suitably regularized. It is shown that using radial slave boson fields allows to overcome all hurdles following from the normal ordering procedure. It is then demonstrated that this applies to the Green's function as well, and to the correlation functions of physical interest, thereby answering the criticisms raised by Schönhammer [K. Schönhammer, Phys. Rev. B 199042, 2591]. In addition, the investigation generalizes the calculations to the Hubbard model extended by a non‐local Coulomb interaction. [ABSTRACT FROM AUTHOR]

Upcoming THz applications require compact, robust, and efficient sources with high output‐power. Among electronic devices, resonant tunneling diodes are a promising candidate for THz operation. Triple‐barrier resonant tunneling diodes provide a high degree of design and operation freedom. Zero‐bias detection and THz emission are possible with the same device due to the asymmetric structure and IV curve. However, more investigations in the layer stack design are required. An investigation is presented into the effect of collector spacer thickness and doping profile in the subcollector contact region. The aim is to simultaneously optimize the RF output‐power and cut‐off frequency in triple‐barrier structures. A series of devices with different collector spacers and two distinct doping profiles are fabricated. A trade‐off between collector spacer thickness and doping profile for either higher output power or cut‐off frequency is observed. In addition, the simulation results are presented from a nonequilibrium Green's function solver implemented in Python. Herein, a need for accurate determination of the extent of the nonequilibrium region to achieve simulation results matching the IV measurements is observed. [ABSTRACT FROM AUTHOR]

A previous combined experimental and theoretical study found that the position of anchoring groups on a phenanthrene (PHE) backbone played a large role in determining the single‐molecule conductance of the PHE derivative. However, a consistent 0.1 G0 feature was found across all PHE derivatives. To understand this, the previously investigated PHE derivatives were placed flat on a simulated Au substrate with a scanning tunneling microscope (STM) tip over PHE and conductance was calculated using the non‐equilibrium Green's function technique in conjunction with density functional theory (NEGF‐DFT). The location of the tip was varied to find the most conductive and most energetically favorable arrangements, which did not coincide. Furthermore, the variation in conductance found in erect junctions was not present when PHE derivatives were lying flat, with all derivatives calculated to have conductance values around 0.1 G0. [ABSTRACT FROM AUTHOR]

A one‐dimensional thaw consolidation model considering the density change from pore ice to pore water is established, and the model describes a special type of moving boundary problem with double moving boundaries. An analytical solution for the model under a time‐varying external load is developed using certain form of superposition principle and the similarity type of general solution. Some known solutions in literature can be recovered as special cases of the analytical solution once the density change from pore ice to pore water is neglected. If the thawing front was to cease at certain time, consolidation of thawed soil in a fixed region is then encountered, and an analytical solution for the post‐thawing consolidation problem is developed using the Green's function method. Computational examples of the analytical solutions are presented. First, comparison between our model and classical model of Morgenstern and Nixon (MN model) is conducted, showing the error caused by neglecting the density change from pore ice to pore water. The MN model overestimates the excessive pore water pressure at locations near the soil surface, while underestimates it at locations near the thawing front; the error caused by neglecting the density change becomes more pronounced with increasing ice content of frozen soil. Second, comparison between the thaw consolidation process under an instant load and that under a corresponding exponential load is made. The difference in thaw consolidation behavior between the two situations mainly displays during the early stage, when there is obvious discrepancy between the two external loads; the degree of consolidation and thaw consolidation settlement are more sensitive to the discrepancy in external load than the excessive pore water pressure is. [ABSTRACT FROM AUTHOR]

Investigating the multiferroic properties of Cu2OCl2$\left(\text{Cu}\right)_{2} \left(\text{OCl}\right)_{2}$, their temperature and magnetic‐field dependencies around the magnetic and ferroelectric phase transition temperatures TN$T_{N}$ and TE$T_{E}$ are analyzed using a microscopic model and Green's function technique. Near the Neel temperature TN$T_{N}$, a kink in the specific heat Cp(T)$C_{p} \left(\right. T \left.\right)$ and also in the phonon energy ω(T)$\omega \left(\right. T \left.\right)$ and damping γ(T)$\gamma \left(\right. T \left.\right)$ due to strong anharmonic spin–phonon interaction is observed. The kink in Cp(T)$C_{p} \left(\right. T \left.\right)$ disappears with increasing magnetic field h. The polarization P(T)$P \left(\right. T \left.\right)$ shows also a small anomaly at TN$T_{N}$ and decreases with increasing magnetic field h. This behavior strongly suggests that Cu2OCl2$\left(\text{Cu}\right)_{2} \left(\text{OCl}\right)_{2}$ exhibits multiferroic characteristics. A kink at TN$T_{N}$ can be seen in the real part of the dielectric constant ε′(T)$\left(\epsilon\right)^{&amp;amp;amp;amp;amp;aposx;} \left(\right. T \left.\right)$, too. It should be noted that ε′$\left(\epsilon\right)^{&amp;amp;amp;amp;amp;aposx;}$ demonstrates a significant increase with increasing field strength h below TN$T_{N}$, which is a pronounced magneto‐dielectric effect. These findings qualitatively agree with the experimental data. [ABSTRACT FROM AUTHOR]

Correlated classical and quantum many‐particle systems out of equilibrium are of high interest in many fields, including dense plasmas, correlated solids, and ultracold atoms. Accurate theoretical description of these systems is challenging both, conceptionally and with respect to computational resources. While for classical systems, in principle, exact simulations are possible via molecular dynamics, this is not the case for quantum systems. Alternatively, one can use many‐particle approaches such as hydrodynamics, kinetic theory, or nonequilibrium Green functions (NEGF). However, NEGF exhibit a very unfavorable cubic scaling of the CPU time with the number of time steps. An alternative is the G1–G2 scheme [N. Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)] which allows for NEGF simulations with time linear scaling, however, at the cost of large memory consumption. The reason is the need to store the two‐particle correlation function. This problem can be overcome for a number of approximations by reformulating the kinetic equations in terms of fluctuations – an approach that was developed, for classical systems, by Yu.L. Klimontovich [JETP 33, 982 (1957)]. Here, we present an overview of his ideas and extend them to quantum systems. In particular, we demonstrate that this quantum fluctuations approach can reproduce the nonequilibrium GW approximation [E. Schroedter et al., Cond. Matt. Phys. 25, 23401 (2022)] promising high accuracy at low computational cost which arises from an effective semiclassical stochastic sampling procedure. We also demonstrate how to extend the approach to the two‐time exchange‐correlation functions and the density response properties. [E. Schroedter et al., Phys. Rev. B 108, 205109 (2023)]. The results are equivalent to the Bethe–Salpeter equation for the two‐time exchange‐correlation function when the generalized Kadanoff‐Baym ansatz with Hartree‐Fock propagators is applied [E. Schroedter and M. Bonitz, phys. stat. sol. (b) 2024, 2300564]. [ABSTRACT FROM AUTHOR]

Quite a many electron transport problems in condensed matter physics are analyzed with a quasiparticle Boltzmann equation. For sufficiently slowly varying weak external potentials it can be derived from the basic equations of quantum kinetics, provided quasiparticles can be defined and lead to a pole in the quantum‐mechanical propagators. The derivation breaks down, however, in the vicinity of an interface which constitutes an abrupt strong perturbation of the system. In this contribution we discuss in a tutorial manner a particular technique to systematically derive, for a planar, nonideal interface, matching conditions for the quasi‐particle Boltzmann equation. The technique is based on pseudizing the transport problem by two auxiliary interface‐free systems and matching Green functions at the interface. Provided quasiparticles exist in the auxiliary systems, the framework can be put onto the semiclassical level and the desired boundary conditions result. For ideal interfaces, the conditions can be guessed from flux conservation, but for complex interfaces this is no longer the case. The technique presented in this work is geared toward such interfaces. [ABSTRACT FROM AUTHOR]

Investigating the multiferroic properties of Cu2OCl2$\left(\text{Cu}\right)_{2} \left(\text{OCl}\right)_{2}$, their temperature and magnetic‐field dependencies around the magnetic and ferroelectric phase transition temperatures TN$T_{N}$ and TE$T_{E}$ are analyzed using a microscopic model and Green's function technique. Near the Neel temperature TN$T_{N}$, a kink in the specific heat Cp(T)$C_{p} \left(\right. T \left.\right)$ and also in the phonon energy ω(T)$\omega \left(\right. T \left.\right)$ and damping γ(T)$\gamma \left(\right. T \left.\right)$ due to strong anharmonic spin–phonon interaction is observed. The kink in Cp(T)$C_{p} \left(\right. T \left.\right)$ disappears with increasing magnetic field h. The polarization P(T)$P \left(\right. T \left.\right)$ shows also a small anomaly at TN$T_{N}$ and decreases with increasing magnetic field h. This behavior strongly suggests that Cu2OCl2$\left(\text{Cu}\right)_{2} \left(\text{OCl}\right)_{2}$ exhibits multiferroic characteristics. A kink at TN$T_{N}$ can be seen in the real part of the dielectric constant ε′(T)$\left(\epsilon\right)^{&amp;amp;amp;amp;amp;aposx;} \left(\right. T \left.\right)$, too. It should be noted that ε′$\left(\epsilon\right)^{&amp;amp;amp;amp;amp;aposx;}$ demonstrates a significant increase with increasing field strength h below TN$T_{N}$, which is a pronounced magneto‐dielectric effect. These findings qualitatively agree with the experimental data. [ABSTRACT FROM AUTHOR]

We generalize Popoviciu's inequality utilizing the theory of 4-convex function under the effect of new Green functions. We formulate result for power means and quasi means. Also, we give applications in information theory by giving new estimations of generalized Csiszár divergence, Rényi divergence, Shannon entropy, Kullback-Leibler divergence, x² divergence, Zipf-Mandelbrot entropy, and Hybrid Zipf-Mandelbrot entropy. [ABSTRACT FROM AUTHOR]