Complete Theory Research Articles

Homogeneous Cosmological Models in Weyl’s Geometrical Scalar–Tensor Theory

In this paper, we consider homogeneous cosmological solutions in the context of the Weyl geometrical scalar–tensor theory. Firstly, we exhibit an anisotropic Kasner type solution taking advantage of some similarities between this theory and the Brans–Dicke theory. Next, we consider an isotropic model with a flat spatial section sourced by matter configurations described by a perfect fluid. In this model, we obtain an analytical solution for the stiff matter case. For other cases, we carry out a complete qualitative analysis theory to investigate the general behaviour of the solutions, presenting some possible scenarios. In this work, we do not consider the presence of the cosmological constant nor do we take any potential of the scalar field into account. Because of this, we do not find any solution describing the acceleration of the universe.

Molecular properties of TCNQ and anions

The purpose of the work is to calculate accurate values of molecular properties of tetracyanoquinodimethane (TCNQ) and anions using the complete active space self-consistent field and complete active space second-order perturbation theory methods. The accuracy has been evaluated using several basis sets and active spaces. The calculated properties have, in many cases, been confirmed by experimental data (within parentheses), e.g., 9.54 eV (9.61 eV) and 3.36 eV (3.38 eV) for the ionization potential and electron affinity, respectively, of TCNQ; 3.12 eV (3.01 eV) and 3.54 eV (3.42 or 3.60 eV) for transition energies to the two lowest-lying excited singlet states of TCNQ; − 0.03, 0.46 and 1.44 eV (0, 0.5 and 1.4 eV) for electronic energies in electron attachment of TCNQ forming hbox {TCNQ}^-; and 3.88 eV (3.71 eV) for the transition energy to the second lowest-lying excited singlet state of hbox {TCNQ}^{2-}. Further, the calculations have brought insight into some experimental observations, e.g., the shape of the fluorescence spectrum of TCNQ at 3–4 eV.

Quantum fluctuations, particles and entanglement: solving the quantum measurement problems

The so-called quantum measurement problems are solved from a new perspective. One of the main observations is that the basic entities of our world are particles, elementary or composite. It follows that each elementary process, hence each measurement process at its core, is a spacetime, pointlike, event. Another key idea is that, when a microsystem ψ gets into contact with the experimental device, factorization of ψ rapidly fails and entangled mixed states appear. The wave functions for the microsystem-apparatus coupled system for different measurement outcomes then lack overlapping spacetime support. It means that the aftermath of each measurement is a single term in the sum: a “wave-function collapse”. Our discussion leading to a diagonal density matrix, ρ = diag(|c 1|2,…,|cn |2,…) shows how the information encoded in the wave function gets transcribed, via entanglement with the experimental device and environment, into the relative frequencies Pn = |cn |2 for various experimental outcomes F = fn . Our discussion represents the first, significant steps towards filling in the logical gaps in the conventional interpretation based on Born’s rule, replacing it with a clearer understanding of quantum mechanics. Accepting objective reality of quantum fluctuations, independent of any experiments, and independently of human presence, one renounces the idea that in a fundamental, complete theory of Nature the result of each single experiment must necessarily be predictable.

Some Backscatter Modeling Issues Complicating the Sonar‐Based Monitoring of Suspended Sediments in Rivers

AbstractThe measurement of suspended sediments from acoustic backscatter was originally developed in marine science for monitoring near‐bottom suspensions usually composed of sand particles. In the last decade, there has been a growing interest in adapting these techniques to rivers. The so‐called “solid particle theory” developed in oceanography mainly applies to suspensions of non‐cohesive solid particles producing incoherent backscatter signal. So far, this theory has been used for interpreting river backscatter even if it relies on assumptions that are not obviously met in rivers. This study uses a set of measurements made on the Rhône River in France to discuss the typical issues which challenge the interpretation of sound backscattering for monitoring suspended sediments in rivers. Large discrepancies between model outputs and measurements for frequencies lower than 2.5 MHz suggest that other scattering processes including flocculation and air micro‐bubbles may have a large impact on acoustic backscatter and attenuation. Deviations of the backscatter echo distribution from Rayleigh statistics were observed, suggesting that the assumption of incoherent backscattering is not always met. This work calls for the development of a more complete theory for interpreting river backscatter.

Quantum-Interference-Enhanced Phonon Laser in Cavity Optomechanics

Cavity-optomechanics-based phonon lasers are traditionally described in terms of three-mode resonance, while the energy nonconservation optomechanical terms are conventionally ignored. Here, we present a complete theory of phonon lasers, emphasizing the importance of the previously omitted optomechanical interaction. We show that this indispensable optomechanical interaction is equivalent to a Kerr nonlinear interaction. Analytical results show that the interference between this Kerr-type interaction and three-mode resonance adds a transition channel with no phonon emission or absorption, thus enhancing phonon lasing and realizing an ultralow-threshold phonon laser and even a phonon cooler. The interference effect produces an asymmetric gain profile with a Fano spectral shape in addition to the traditional Lorentzian shape. Our complete theory shows perfect agreement with existing experiments and provides a new degree of freedom to manipulate optomechanical phonon lasers.

Evolution of 1/f Flux Noise in Superconducting Qubits with Weak Magnetic Fields.

The microscopic description of 1/f magnetic flux noise in superconducting circuits has remained an open question for several decades despite extensive experimental and theoretical investigation. Recent progress in superconducting devices for quantum information has highlighted the need to mitigate sources of qubit decoherence, driving a renewed interest in understanding the underlying noise mechanism(s). Though a consensus has emerged attributing flux noise to surface spins, their identity and interaction mechanisms remain unclear, prompting further study. Here, we apply weak in-plane magnetic fields to a capacitively shunted flux qubit (where the Zeeman splitting of surface spins lies below the device temperature) and study the flux-noise-limited qubit dephasing, revealing previously unexplored trends that may shed light on the dynamics behind the emergent 1/f noise. Notably, we observe an enhancement (suppression) of the spin-echo (Ramsey) pure-dephasing time in fields up to B=100 G. With direct noise spectroscopy, we further observe a transition from a 1/f to approximately Lorentzian frequency dependence below 10Hz and a reduction of the noise above 1MHz with increasing magnetic field. We suggest that these trends are qualitatively consistent with an increase of spin cluster sizes with magnetic field. These results should help to inform a complete microscopic theory of 1/f flux noise in superconducting circuits.

THE EFFECT OF COVID-19 DISRUPTION, RESILIENCE, AND ADAPTATION STRATEGIES ON SUPPLY CHAIN PERFORMANCE (Case Study of Pharmaceutical SOE)

Abstract
 The pandemic of COVID-19 caused disruption on supply chain systems, with long-term consequences. The goal of this research is to identify the internal and external factors that cause high vulnerability to disruption and to investigate how COVID-19 disruption, resilience, and adaptation strategies affect supply chain performance (SCP). The research was conducted using qualitative and quantitative approaches, based on a case study at a pharmaceutical company. Document analysis, observation, and interviews were used to collect research data. The techniques and analytical tools used in this study include value chain analysis for internal factor analysis, PESTLE for external factor analysis, and multiple linear regression using Minitab to measure the relationship between variables. The study's findings indicate that internal and external factors influence a company's vulnerability when the COVID-19 disruption occurs. The COVID-19 disruption has had a negative impact on SCP. SCR, SCRM, SCI, and SCE are all components of resilience that have a positive impact on SCP. This research also shows that adaptation strategies such as intertwining, substitution, and repurposing can reduce the impact of pandemic disruptions on SCP and improve it. This study suggests that additional research be conducted on companies with different uniqueness and business processes in order to develop a more complete theory.
 

Transient wheel–rail rolling contact theories

This paper provides an overview of different theories to analyse unsteady rolling contact phenomena between wheel and rail: the exact formulation by Kalker, the simplified model based on the Winkler approximation, and the recent two-regime model. The classic solution to the transient problem derived by Kalker using the complete theory of elasticity is first recalled. The more involved situation of combined creepages and spin is analysed using Kalker’s simplified model. Analytical solutions are reported in integral form concerning the time-varying and constant creepages. Qualitative results are additionally provided for the case of a time-varying contact patch. Finally, a novel theory, which describes the transient evolution of the force-creepage characteristics using a system of ordinary differential equations (ODEs), is introduced.

TT¯ deformed soft theorem

In this paper, we derive a $T\bar{T}$ deformed soft graviton theorem in the context of celestial holography. As a concrete example, it illustrates that a two-dimensional irrelevant deformation can be applied to a four-dimensional theory at the level of amplitudes. We argue that the $T\bar{T}$ deformation has a close relation to the loop-correction from the amplitude side which could provide an alternative way to construct an ultraviolet complete quantum theory of gravity.

Electron Trap Depths in Cubic Lutetium Oxide Doped with Pr and Ti, Zr or Hf─From Ab Initio Multiconfigurational Calculations.

We propose a universal approach to model intervalence charge transfer (IVCT) and metal-to-metal charge transfer (MMCT) transitions between ions in solids. The approach relies on already well-known and reliable ab initio RASSCF/CASPT2/RASSI-SO calculations for a series of emission center coordination geometries (restricted active space self-consistent field, complete active space second-order perturbation theory, and restricted active space state interaction with spin-orbit coupling). Embedding with ab initio model potentials (AIMPs) is used to represent the crystal lattice. We propose a way to construct the geometries via interpolation of the coordinates obtained using solid-state density functional theory (DFT) calculations for the structures where the activator metal is at specific oxidation (charge) states of interest. The approach thus takes the best of two worlds: the precision of the embedded cluster calculations (including localized excited states) and the geometries from DFT, where the effects of ionic radii mismatch (and eventual nearby defects) can be modeled explicitly. The method is applied to the Pr activator and Ti, Zr, Hf codopants in cubic Lu2O3, in which the said ions are used to obtain energy storage and thermoluminescence properties. Electron trap charging and discharging mechanisms (not involving a conduction band) are discussed in the context of the IVCT and MMCT role in them. Trap depths and trap quenching pathways are analyzed.

The structure of accounting theory. Part 1

Subject. This article examines the main approaches to the construction of the theory of accounting, namely the inductive and deductive ones. Objectives. The article aims to identify the advantages and disadvantages of each of the approaches, analyze the structure of the theory of accounting in detail, and identify it at the present stage of development of accounting as a science discipline. Methods. For the study, I used combinations of analysis and synthesis, induction and deduction, and historical and logical research methods. Results. The article defines the structure of the theory of accounting that includes the objectives of financial reporting, postulates and theoretical concepts of accounting, as well as the principles and techniques of accounting. Conclusions and Relevance. The article concludes that of the two existing approaches to the construction of the theory of accounting, the inductive approach has a number of significant drawbacks that do not allow building a full-fledged theory of accounting. The deductive approach also has a number of drawbacks associated with understanding the axiomatic basis and the inference rules, but it helps lay the scientific foundations for building a complete and consistent theory of accounting. The results obtained can be used to create the theory of accounting.

Teleparallel Minkowski Spacetime with Perturbative Approach for Teleparallel Gravity on a Proper Frame

A complete perturbation theory suitable for teleparallel gravity is developed. The proposed perturbation scheme takes into account perturbations of the coframe, the metric, and the spin-connection, while ensuring that the resulting perturbed system continues to describe a teleparallel gravity situation. The resulting perturbation scheme can be transformed to one in which perturbations all take place within the co-frame. A covariant definition of a teleparallel Minkowski geometry is proposed. We compute the perturbed field equations for f(T) teleparallel gravity and discuss the stability of the teleparallel Minkowski geometry within f(T) teleparallel gravity.

Using ultrapowers to compare continuous structures

In 1967 the author introduced a pre-ordering of all first order complete theories where T is lower than U if it is easier for an ultrapower of a model of T than an ultrapower of a model of U to be saturated. In a long series of recent papers, Malliaris and Shelah showed that this pre-ordering is very rich and gives a useful way of classifying simple theories. In this paper we investigate the analogous pre-ordering in continuous model theory.

Analytic first-order derivatives of CASPT2 with IPEA shift.

Complete active space second-order perturbation theory (CASPT2) is useful for accurately predicting properties of complex electronic structures, but it is well known that it systematically underestimates excitation energies. The underestimation can be corrected using the ionization potential-electron affinity (IPEA) shift. In this study, analytic first-order derivatives of CASPT2 with the IPEA shift are developed. CASPT2-IPEA is not invariant with respect to rotations among active molecular orbitals, and two additional constraint conditions are necessary in the CASPT2 Lagrangian to formulate analytic derivatives. The method developed here is applied to methylpyrimidine derivatives and cytosine, and minimum energy structures and conical intersections are located. By comparing energies relative to the closed-shell ground state, we find that the agreement with experiments and high-level calculations is indeed improved by the inclusion of the IPEA shift. The agreement of geometrical parameters with high-level calculations may also be improved in some cases.

A Theoretical Study on Mid-Infrared Difference Frequency Generation Based on Periodically Poled Thin-Film LiNbO3

A mid-infrared difference frequency generator (DFG) based on a periodically poled thin-film lithium niobate rib waveguide on a sapphire substrate is theoretically studied. A mode analysis is carried out at the mid-infrared region, and the analysis focuses on the effects of waveguide geometry on effective refractive indices of a few lower-order modes. A complete theory suitable for modeling a DFG based on a waveguide structure is described. Its validity is confirmed by comparing the theoretical results with previously reported experimental data. Explicit expressions are presented for nonlinear conversion efficiency, thermal tunability and quasi-phase matching (QPM) bandwidth. The effects of waveguide geometry and mode hybridization on the effective mode field area and mode overlap factor, which are either inversely or linearly proportional to nonlinear conversion efficiency, are studied in detail. In this article, an optimized mid-infrared DFG with improved geometry that exhibits excellent performance, including a higher nonlinear conversion efficiency of 230–273% W−1cm−2 in the temperature range of 20–120 °C; a larger temperature tunability of 2.2 nm/°C; a larger QPM bandwidth of ~130 nm; and a higher idler wave output power, as much as −2 dBm when Pp = 20 dBm and Ps = 11.5 dBm, is suggested.

Differential equations of oscillation of thin plates with point bonding

Abstract The relevance of the research results presented in this article lies in the general concept of elasticity theory, which integrates the bases of theoretical-empirical physics, practical mathematics and the natural implementation of modelling results in the fields of industrial (to a large extent in the design and manufacture of aircraft and naval aircraft shells and fuselages), construction (more so in the design and formation of multi-layer building structures), electronics and other areas of the science and industry complex. The aim of the study is to form a mathematical model of thin plate vibration based on a system of differential equations for the computational case of point bonding. The method of scientific search (Multilocal Literature Review) is used to achieve the set goal, which made it possible to establish the actual scientific-theoretical basis of the investigated problem, the method of mathematical modelling allowing to systematize the systems of differential equations developed earlier and formed in the framework of the present study, both for the general concept of the theory of elasticity of thin plates and for a selected calculation situation with partial constraints in the form of point bond imposing. As a result of the investigations conducted in the framework of this study, a mathematical model of the oscillations of thin plates bounded by special point-coupling conditions has been obtained, consisting of a system of differential equations obtained by successive iterations of mathematical transformations for the generated local boundary conditions. The mathematical model obtained is of practical scientific interest. The developed model environment forms a complete mathematical theory of elasticity for the formulated problem of the oscillatory process of thin plates with bounding point couplings. This problem has not received a satisfactory mathematical apparatus because of the complexity and cumbersomeness of analytical methods to describe the investigated elastic object.

Volume Loss and Recovery in Bovine Knee Meniscus Loaded in Circumferential Tension.

Load-induced volume change is an important aspect of knee meniscus function because volume loss creates fluid pressure, which minimizes friction and helps support compressive loads. The knee meniscus is unusual amongst cartilaginous tissues in that it is loaded not only in axial compression, but also in circumferential tension between its tibial attachments. Despite the physiologic importance of the knee meniscus' tensile properties, its volumetric strain in tension has never been directly measured, and predictions of volume strain in the scientific literature are inconsistent. In this study, we apply uniaxial tension to bovine knee meniscus and use biplanar imaging to directly observe the resulting three-dimensional volume change and unloaded recovery, revealing that tension causes volumetric contraction. Compression is already known to also cause contraction; therefore, all major physiologic loads compress and pressurize the meniscus, inducing fluid outflow. Although passive unloaded recovery is often described as slow relative to loaded loss, here we show that at physiologic strains the volume recovery rate in the meniscus upon unloading is faster than the rate of volume loss. These measurements of volumetric strain are an important step toward a complete theory of knee meniscus fluid flow and load support.

Τ-quasi-Cauchy spaces - a non-symmetric theory of completeness and completion

Based on the concept of Cauchy pair Τ-filters, we develop an axiomatic theory of completeness for non-symmetric spaces, such as Τ-quasi-uniform (limit) spaces or L-metric spaces. We show that the category of Τ-quasi-Cauchy spaces is topological and Cartesian closed and we construct a finest completion for a non-complete Τ-quasi-Cauchy space. In the special case of symmetry, Τ-quasi-Cauchy spaces can be identified with Τ-Cauchy spaces.

Importance of Dispersion in the Molecular Geometries of Mn(III) Spin-Crossover Complexes

The computational investigation of the molecular geometries of a pair of manganese(III) spin-crossover complexes is reported. For the geometry of the quintet high-spin state, density functionals significantly overestimate Mn-Namine bond distances, although the geometry for the triplet intermediate-spin state is well described. Comparisons with several wave function-based methods demonstrate that this error is due to the limited ability of commonly used density functionals to recover dispersion beyond a certain extent. Among the methods employed for geometry optimization, restricted open-shell Møller-Plesset perturbation theory (MP2) appropriately describes the high-spin geometry but results in a slightly shorter Mn-O distance in both spin states. On the other hand, extended multistate complete active space second-order perturbation theory (XMS-CASPT2) provides a good description of the geometry for the intermediate-spin state but also sufficiently recovers dispersion, performing well for the high-spin state. Despite the fact that the electronic structure of both spin states is dominated by one-electron configuration, XMS-CASPT2 offers a balanced approach, leading to molecular geometries with much better agreement with experiment than MP2 and DFT. A scan along the Mn-Namine bond demonstrates that for these complexes coupled cluster methods (i.e., DLPNO-CCSD(T)) also yield bond distances in agreement with experiment while multiconfiguration pair density functional theory (MC-PDFT) is unable to recover dispersion well enough, analogous to single-reference DFT.

Liouville closed HT-fields

Let T be a complete, model complete o-minimal theory extending the theory of real closed ordered fields. An HT-field is a model K of T equipped with a T-derivation ▪ such that the underlying ordered differential field of ▪ is an H-field. We study HT-fields and their extensions. Our main result is that if T is power bounded, then every HT-field K has either exactly one or exactly two minimal Liouville closed HT-field extensions up to K-isomorphism. The assumption of power boundedness can be relaxed to allow for certain exponential cases, such as T=Th(Ran,exp).