Higher-order Operators Research Articles

Hermite–Hadamard-Type Inequalities for Harmonically Convex Functions via Proportional Caputo-Hybrid Operators with Applications

In this paper, we aim to establish new inequalities of Hermite–Hadamard (H.H) type for harmonically convex functions using proportional Caputo-Hybrid (P.C.H) fractional operators. Parameterized by α, these operators offer a unique flexibility: setting α=1 recovers the classical inequalities for harmonically convex functions, while setting α=0 yields inequalities for differentiable harmonically convex functions. This framework allows us to unify classical and fractional cases within a single operator. To validate the theoretical results, we provide several illustrative examples supported by graphical representations, marking the first use of such visualizations for inequalities derived via P.C.H operators. Additionally, we demonstrate practical applications of the results by deriving new fractional-order recurrence relations for the modified Bessel function of type-1, which are useful in mathematical modeling, engineering, and physics. The findings contribute to the growing body of research in fractional inequalities and harmonic convexity, paving the way for further exploration of generalized convexities and higher-order fractional operators.

A comparative study of several enhanced energy operators for vibration exciter bearing fault diagnosis

Rolling bearings of the vibration exciter are prone to failure due to long-term high amplitude alternating impact loads, causing economic losses and threatening production safety. The heavy environmental noise during the operation of the vibration exciter and the high vibration level generated by the eccentric block make the weak bearing fault features submerged and difficult to extract. Teager–Kaiser energy operator is a popular method for extracting bearing fault features. However, it has poor noise-robustness and low accuracy of frequency estimation of the exciter with heavy noise and multiple disturbances. Therefore, three enhanced energy operators—symmetric higher-order analytical energy operator (SHAEO), multi-resolution symmetric difference energy operator (MSDAEO), and symmetric higher-order frequency weighted energy operator (SHFWEO) have been introduced. This paper compares and studies the three energy operators through theoretical analysis and vibration exciter bearing fault diagnosis experiments. The results show that MSDAEO has the most outstanding noise robustness, but has the minimum effect on improving the signal-to-interference ratio (SIR) of the signal among the three energy operators. SHFWEO has the most prominent performance on improving SIR but is sensitive to the signal energy. SHAEO can increase the amplitude of the signal, and its ability to improve signal SIR is higher than MSDAEO but lower than SHFWEO. Its ability to improve signal SNR is the weakest among the three. Finally, the characteristics of preprocessing methods that can be jointly used by the three energy operators in different application scenarios are presented.

Tunable Optical High‐Order Differential Microscopy for Cell Structure Detection

AbstractOptical differential microscopy is an important tool for the detection and recognition of transparent biological objects. Among it, the first‐order optical differentiation is commonly utilized to aid in fast, label‐free, and contactless detection. However, the characterization of detailed contours for some smooth object areas may be limited, and a higher order operation needs to be executed. A tunable optical high‐order differential microscopy is proposed and implemented, in virtue of electric‐driven liquid crystal (LC). By electrically switching the working state of LC, the differential operation can be flexibly tuned in desired order, such as from zero‐order to first‐order and second‐order differentiations. Using this scheme, clear edge‐enhanced images of different‐contrast objects even transparent biological cells are experimentally acquired under multi‐wavelength cases. Specifically, based on the connection between high‐order differential results and edge features, further gained in‐depth information in the size of light spot and structure of plant cells. The beam waist radius of a laser is determined as 0.35 ± 0.002 mm, and the cell wall thickness is estimated about 3 to 5 microns. These results may open the avenue for biological imaging and microscopic measurement.

Flexible graphene textile-based sensor integrates programmable DNAzyme and logic gates for efficient small extracellular vesicle-miRNA detection

Nucleic acid signal amplification technologies and their cascade systems possess powerful ability to amplify signals. However, their application in biological computing, which necessitates a strict logical relationship, requires further investigation. To address this need, we developed a flexible sensing substrate consisting of carbon fiber cloth/graphene walls (CFC/GW), integrated with a 3D DNA tetrahedron (DNA-Te)-assisted bioplatform. This platform serves as the foundation for two types of Boolean logic gates: the “AND” and “OR” gate. The output system of the Cu2+ + DNAzyme logic gate module, activated by multiple miRNAs, was combined with the CFC/GW/Au-Te-based detection system to precisely identify small extracellular vesicle (sEV)-derived miRNAs in ultratrace quantities. Leveraging DNA Te-assisted DNAzyme molecular logic circuits, we designed higher-order Boolean logic operations to effectively identify and accurately read sEV-miRNAs in complex mixed samples. By integrating a material with low-background-signal and high-performance material with the original branch-strand migration logic gate system, we achieved an intelligent sensing platform that integrates capture, recognition, detection, and interpretation of sEV-miRNAs. We successfully demonstrated the response of the logic gate module of sEV-miRNAs in clinical samples, with detection results maintaining high consistency with conventional qRT-PCR methods. Our DNA logic gate platform boasts a simple design, adaptability, expandable complexity, and compatibility with various systems, enabling diverse possibilities for the nucleic acid-based development of intricate transduction networks in biomedical fields. This platform paves the way for more effective diagnosis, treatment, and monitoring of diseases, marking a significant advancement in nucleic acid signal amplification technologies and their utilization in biological computing.

Efficient higher-order matrix product operators for time evolution

We introduce a systematic construction of higher-order matrix product operator (MPO) approximations of the time evolution operator for generic (short and long range) one-dimensional Hamiltonians. We demonstrate the utility of our construction, by showing an order of magnitude speedup in simulation cost compared to conventional first-order MPO time evolution schemes.

Global Kato smoothing and Strichartz estimates for Schrödinger type equations with rough decay potentials

Let [Formula: see text] be a higher-order elliptic operator on [Formula: see text], where [Formula: see text] is a general bounded decaying potential. This paper focuses on the global Kato smoothing and Strichartz estimates for solutions to Schrödinger-type equation associated with [Formula: see text]. In particular, we first establish sharp global Kato smoothing estimates for [Formula: see text], based on uniform resolvent estimates of Kato–Yajima type for the absolutely continuous part of [Formula: see text]. As a consequence, we also obtain optimal local decay estimates. Using these local decay estimates, we then prove the full set of Strichartz estimates, including the endpoint case. Notably, we derive Strichartz estimates with sharp smoothing effects for higher-order cases with rough potentials, which are applicable to the study of nonlinear higher-order Schrödinger equations. Finally, we introduce new uniform Sobolev estimates of the Kenig–Ruiz–Sogge type, incorporating an additional derivative term, which are crucial for establishing the sharp Kato smoothing estimates.

Photonic counterdiabatic quantum optimization algorithm

One of the key applications of near-term quantum computers has been the development of quantum optimization algorithms. However, these algorithms have largely been focused on qubit-based technologies. Here, we propose a hybrid quantum-classical approximate optimization algorithm for photonic quantum computing, specifically tailored for addressing continuous-variable optimization problems. Inspired by counterdiabatic protocols, our algorithm reduces the required quantum operations for optimization compared to adiabatic protocols. This reduction enables us to tackle non-convex continuous optimization within the near-term era of quantum computing. Through illustrative benchmarking, we show that our approach can outperform existing state-of-the-art hybrid adiabatic quantum algorithms in terms of convergence and implementability. Our algorithm offers a practical and accessible experimental realization, bypassing the need for high-order operations and overcoming experimental constraints. We conduct a proof-of-principle demonstration on Xanadu’s eight-mode nanophotonic quantum chip, successfully showcasing the feasibility and potential impact of the algorithm.

Spurious numerical mixing under strong tidal forcing: a case study in the south-east Asian seas using the Symphonie model (v3.1.2)

Abstract. The role of mixing between layers of different densities is key to how the ocean works and interacts with other components of the Earth's system. Correctly accounting for its effect in numerical simulations is therefore of utmost importance. However, numerical models are still plagued with spurious sources of mixing, originating mostly from the vertical advection schemes in the case of fixed-coordinate models. As the number of phenomena explicitly resolved by models increases, so does the amplitude of resolved vertical motions and the amount of spurious numerical mixing, and regional models are no exception to this. This paper provides a clear illustration of this phenomenon in the context of simulating the south-east Asian (SEA) seas along with a simple way to reduce its impact. This region is known for its particularly strong internal tides and the fundamental role they play in the dynamic of the region. Using the Symphonie ocean model, simulations including and excluding tides and using a pseudo-third-order upwind advection scheme on the vertical are compared to several reference datasets, and the impact on water masses is assessed. The high diffusivity of this advection scheme is demonstrated along with the importance of accounting for tidal mixing for a correct representation of water masses. Simultaneously, we present an improvement in this advection scheme to make it more suitable for use in the vertical. Simulations with the new formulation are added for comparison. We conclude that the use of a higher-order numerical diffusion operator greatly improves the overall performance of the model.

Characterising transformations between quantum objects, 'completeness' of quantum properties, and transformations without a fixed causal order

Many fundamental and key objects in quantum mechanics are linear mappings between particular affine/linear spaces. This structure includes basic quantum elements such as states, measurements, channels, instruments, non-signalling channels and channels with memory, and also higher-order operations such as superchannels, quantum combs, n-time processes, testers, and process matrices which may not respect a definite causal order. Deducing and characterising their structural properties in terms of linear and semidefinite constraints is not only of foundational relevance, but plays an important role in enabling the numerical optimisation over sets of quantum objects and allowing simpler connections between different concepts and objects. Here, we provide a general framework to deduce these properties in a direct and easy to use way. While primarily guided by practical quantum mechanical considerations, we also extend our analysis to mappings between general linear/affine spaces and derive their properties, opening the possibility for analysing sets which are not explicitly forbidden by quantum theory, but are still not much explored. Together, these results yield versatile and readily applicable tools for all tasks that require the characterisation of linear transformations, in quantum mechanics and beyond. As an application of our methods, we discuss how the existence of indefinite causality naturally emerges in higher-order quantum transformations and provide a simple strategy for the characterisation of mappings that have to preserve properties in a 'complete' sense, i.e., when acting non-trivially only on parts of an input space.

Improved Homogenization Estimates for Higher-order Elliptic Operators in Energy Norms

Improved Homogenization Estimates for Higher-order Elliptic Operators in Energy Norms

Operator estimates for homogenization of higher-order elliptic operators with periodic coefficients

In L 2 ( R d ; C n ) L_2(\mathbb {R}^d;\mathbb {C}^n) , a strongly elliptic differential operator A ε {\mathcal {A}}_\varepsilon of order 2 p 2p is studied. Its coefficients are periodic and depend on x / ε \mathbf {x}/\varepsilon . The resolvent ( A ε + I ) − 1 ({\mathcal {A}}_\varepsilon +I)^{-1} is approximated in the operator norm on L 2 ( R d ; C n ) L_2(\mathbb {R}^d;\mathbb {C}^n) : ( A ε + I ) − 1 = ( A 0 + I ) − 1 + ∑ j = 1 2 p − 1 ε j K j , ε + O ( ε 2 p ) . \begin{equation*} ({\mathcal {A}}_\varepsilon +I)^{-1} = ({\mathcal {A}}^0+I)^{-1} + \sum _{j=1}^{2p-1} \varepsilon ^{j} {\mathcal {K}}_{j,\varepsilon } + O(\varepsilon ^{2p}). \end{equation*} Here A 0 {\mathcal {A}}^0 is an effective operator with constant coefficients, and K j , ε {\mathcal {K}}_{j,\varepsilon } , j = 1 , … , 2 p − 1 j=1,\dots ,2p-1 , are appropriate correctors.

Designing optimal protocols in Bayesian quantum parameter estimation with higher-order operations

Using quantum systems as sensors or probes has been shown to greatly improve the precision of parameter estimation by exploiting unique quantum features such as entanglement. A major task in quantum sensing is to design the optimal protocol, i.e., the most precise one. It has been solved for some specific instances of the problem, but in general even numerical methods are not known. Here, we focus on the single-shot Bayesian setting, where the goal is to find the optimal initial state of the probe (which can be entangled with an auxiliary system), the optimal measurement, and the optimal estimator function. We leverage the formalism of higher-order operations to develop a method based on semidefinite programming that finds a protocol that is close to the optimal one with arbitrary precision. Crucially, our method is not restricted to any specific quantum evolution, cost function, or prior distribution, and thus can be applied to any estimation problem. Moreover, it can be applied to both single-parameter or multiparameter estimation tasks. We demonstrate our method with three examples, consisting of unitary phase estimation, thermometry in a bosonic bath, and multiparameter estimation of an SU(2) transformation. Exploiting our methods, we extend several results from the literature. For example, in the thermometry case, we find the optimal protocol at any finite time and quantify the usefulness of entanglement. Published by the American Physical Society 2024

ALPs, the on-shell way

We study how the coupling between axion-like particles (ALPs) and matter can be obtained at the level of on-shell scattering amplitudes. We identify three conditions that allow us to compute amplitudes that correspond to shift-symmetric Lagrangians, at the level of operators with dimension 5 or higher, and we discuss how they relate and extend the Adler’s zero condition. These conditions are necessary to reduce the number of coefficients consistent with the little-group scaling to the one expected from the Lagrangian approach. We also show how our formalism easily explains that the dimension-5 interaction involving one ALP and two massless spin-1 bosons receive corrections from higher order operators only when the ALP has a non-vanishing mass. As a direct application of our results, we perform a phenomenological study of the inelastic scattering ℓ+ℓ− → ϕh (with ℓ± two charged leptons, ϕ the ALP and h the Higgs boson) for which, as a result of the structure of the 3-point and 4-point amplitudes, dimension-7 operators can dominate over the dimension-5 ones well before the energy reaches the cutoff of the theory.

Hyperviscosity stabilisation of the RBF-FD solution to natural convection

The numerical stability of fluid flow is an important topic in computational fluid dynamics as fluid flow simulations usually become numerically unstable in the turbulent regime. Many mesh-based methods have already established numerical dissipation procedures that dampen the effects of the unstable advection term. When it comes to meshless methods, the prominent stabilisation scheme is hyperviscosity. It introduces numerical dissipation in the form of a higher-order Laplacian operator. Many papers have already discussed the general effects of hyperviscosity and its parameters. However, hyperviscosity in flow problems has not yet been analyzed in depth. In this paper, we discuss the effects of hyperviscosity on natural convection flow problems as we approach the turbulent regime.

Fault-Tolerant Control of Stochastic High-Order Fully Actuated Systems.

In recent years, high-order fully actuated (HOFA) systems, founded by Prof. GR Duan, have recorded rapid progress for deterministic systems. However, the control issue of stochastic fully actuated systems is still an open problem. This study develops a novel stochastic HOFA system model that complements the existing HOFA methodology. Notably, stochastic signals can be considered in the proposed model, different from the case in the deterministic model. By adopting a high-order operator, equivalent control and stabilization control laws are realized to guarantee the global asymptotic stability in probability of the closed-loop system. For the system with sensor gain faults, an observer-based fault-tolerant control law is designed. Finally, the simulation results validate the effectiveness of the proposed control schemes.

The Jacobi-Sobolev, Laguerre-Sobolev, and Gegenbauer-Sobolev differential equations and their interrelations

Recently, the author determined the higher-order differential operator having the Jacobi-Sobolev polynomials as its eigenfunctions for certain eigenvalues. These polynomials form an orthogonal system with respect to an inner product equipped with the Jacobi measure on the interval [ − 1 , 1 ] with parameters α ∈ N 0 , β > − 1 and two point masses N, S>0 at the right end point of the interval involving functions and their first derivatives. The first purpose of the present paper is to reveal how the Jacobi-Sobolev equation reduces to the differential equation satisfied by the Laguerre-Sobolev polynomials on the positive half line via a confluent limiting process as β → ∞ . Secondly, we explicitly establish the differential equation for the symmetric Gegenbauer-Sobolev polynomials by employing a quadratic transformation of the argument. Each of the three differential operators involved is of order 4 α + 10 and symmetric with respect to the corresponding Sobolev inner product.

Sharp spectral gap estimates for higher-order operators on Cartan–Hadamard manifolds

The goal of this paper is to provide sharp spectral gap estimates for problems involving higher-order operators (including both the clamped and buckling plate problems) on Cartan–Hadamard manifolds. The proofs are symmetrization-free — thus no sharp isoperimetric inequality is needed — based on two general, yet elementary functional inequalities. The spectral gap estimate for clamped plates solves a sharp asymptotic problem from [Q.-M. Cheng and H. Yang, Universal inequalities for eigenvalues of a clamped plate problem on a hyperbolic space, Proc. Amer. Math. Soc. 139(2) (2011) 461–471] concerning the behavior of higher-order eigenvalues on hyperbolic spaces, and answers a question raised in [A. Kristály, Fundamental tones of clamped plates in nonpositively curved spaces, Adv. Math. 367(39) (2020) 107113] on the validity of such sharp estimates in high-dimensional Cartan–Hadamard manifolds. As a byproduct of the general functional inequalities, various Rellich inequalities are established in the same geometric setting.

Equivariant Solutions to the Optimal Partition Problem for the Prescribed Q-Curvature Equation

We study the optimal partition problem for the prescribed constant Q-curvature equation induced by the higher-order conformal operators under the effect of cohomogeneity one actions on Einstein manifolds with positive scalar curvature. This allows us to give a precise description of the solution domains and their boundaries in terms of the orbits of the action. We also prove the existence of least energy symmetric solutions to a weakly coupled elliptic system of prescribed Q-curvature equations under weaker assumptions and conclude a multiplicity result of sign-changing solutions to the prescribed constant Q-curvature problem induced by the Paneitz-Branson operator. Moreover, we study the coercivity of GJMS operators on Ricci solitons, compute the Q-curvature of these manifolds, and give a multiplicity result for the sign-changing solutions to the Yamabe problem with a prescribed number of nodal domains on the Koiso–Cao Ricci soliton.

Higher-Order Process Matrix Tomography of a Passively-Stable Quantum Switch

The field of indefinite causal order (ICO) has seen a recent surge in interest. Much of this research has focused on the quantum switch, wherein multiple parties act in a superposition of different orders in a manner transcending the quantum circuit model. This results in a new resource for quantum protocols, and is exciting for its relation to issues in foundational physics. The quantum switch is also an example of a higher-order quantum operation, in that it transforms not only quantum states but also other quantum operations. To date, no quantum process without a definite causal order has been completely experimentally characterized. Indeed, past work on the quantum switch has confirmed its ICO by measuring causal witnesses or demonstrating resource advantages, but the complete process matrix has been described only theoretically. Here we report our performing higher-order quantum process tomography. However, doing so requires exponentially many measurements with a scaling worse than that of standard process tomography. We overcome this challenge by creating a new fiber-based quantum switch using active optical elements to deterministically generate and manipulate time-bin encoded qubits. Moreover, our new architecture for the quantum switch can be readily scaled to multiple parties. By reconstructing the process matrix, we estimate its fidelity and tailor different causal witnesses directly for our experiment. To achieve this, we measure a set of tomographically complete settings, which also spans the input operation space. Our tomography protocol allows the characterization and debugging of higher-order quantum operations with and without an ICO, while our experimental time-bin techniques could enable the creation of a new realm of higher-order quantum operations with an ICO. Published by the American Physical Society 2024

Асимптотики спектральных данных краевых задач четвертого порядка

In this paper, we derive sharp asymptotics for the spectral data (eigenvalues and weight numbers) of the fourth-order linear differential equation with a distribution coefficient and three types of separated boundary conditions. Our methods rely on the recent results concerning regularization and asymptotic analysis for higher-order differential operators with distribution coefficients. The results of this paper have applications to the theory of inverse spectral problems as well as a separate significance.