On the Bound States in a Non-linear Quantum Field Theory of a Spinor Field with Higher Derivatives

We consider a model of quantum field theory with higher derivatives for a spinor field with quartic selfinteraction. With the help of the Bethe-Salpeter equation we study the problem of the two particle bound states in the "chain" approximation. The existence of a scalar bound state is established.Comment: 14 pages, no figures, LaTe

Development of an Algorithm for Multicriteria Optimization of Deep Learning Neural Networks

Nowadays, machine learning methods are actively used to process big data. A promising direction is neural networks, in which structure optimization occurs on the principles of self-configuration. Genetic algorithms are applied to solve this nontrivial problem. Most multicriteria evolutionary algorithms use a procedure known as non-dominant sorting to rank decisions. However, the efficiency of procedures for adding points and updating rank values in non-dominated sorting (incremental non-dominated sorting) remains low. In this regard, this research improves the performance of these algorithms, including the condition of an asynchronous calculation of the fitness of individuals. The relevance of the research is determined by the fact that although many scholars and specialists have studied the self-tuning of neural networks, they have not yet proposed a comprehensive solution to this problem. In particular, algorithms for efficient non-dominated sorting under conditions of incremental and asynchronous updates when using evolutionary methods of multicriteria optimization have not been fully developed to date. To achieve this goal, a hybrid co-evolutionary algorithm was developed that significantly outperforms all algorithms included in it, including error-back propagation and genetic algorithms that operate separately. The novelty of the obtained results lies in the fact that the developed algorithms have minimal asymptotic complexity. The practical value of the developed algorithms is associated with the fact that they make it possible to solve applied problems of increased complexity in a practically acceptable time. Doi: 10.28991/HIJ-2023-04-01-011 Full Text: PD

Development and Algorithmization of a Method for Analyzing the Degree of Uniqueness of Personal Medical Data

The purpose of this investigation is to develop a method for quantitative assessment of the uniqueness of personal medical data (PMD) to improve their protection in medical information systems (MIS). The relevance of the goal is due to the fact that impersonal PMD can form unique combinations that are potentially of interest to intruders and threaten to reveal the patient's identity and medical confidentiality. Existing approaches were analyzed, and a new method for quantifying the degree of uniqueness of PMD was proposed. A weakness in existing approaches is the assumption that an attacker will use exact matching to identify people. The novelty of the method proposed in this paper lies in the fact that it is not limited to this hypothesis, although it has its limitations: it is not applicable to small samples. The developed method for determining the PMD uniqueness coefficient is based on the assumption of a multidimensional distribution of features, characterized by a covariance matrix, and a normal distribution, which provides the most reliable reflection of the existing relationships between features when analyzing large data samples. The results obtained in computational experiments show that efficiency is no worse than that of focus groups of specialized experts. Doi: 10.28991/HIJ-2023-04-01-09 Full Text: PD

Higher-Derivative Two-Dimensional Massive Fermion Theories

We consider the canonical quantization of a generalized two-dimensional massive fermion theory containing higher odd-order derivatives. The requirements of Lorentz invariance, hermiticity of the Hamiltonian and absence of tachyon excitations suffice to fix the mass term, which contains a derivative coupling. We show that the basic quantum excitations of a higher-derivative theory of order 2N+1 consist of a physical usual massive fermion, quantized with positive metric, plus 2N unphysical massless fermions, quantized with opposite metrics. The positive metric Hilbert subspace, which is isomorphic to the space of states of a massive free fermion theory, is selected by a subsidiary-like condition. Employing the standard bosonization scheme, the equivalent boson theory is derived. The results obtained are used as a guideline to discuss the solution of a theory including a current-current interaction.Comment: 23 pages, Late

Perturbation Theory for Path Integrals of Stiff Polymers

The wormlike chain model of stiff polymers is a nonlinear $\sigma$-model in one spacetime dimension in which the ends are fluctuating freely. This causes important differences with respect to the presently available theory which exists only for periodic and Dirichlet boundary conditions. We modify this theory appropriately and show how to perform a systematic large-stiffness expansions for all physically interesting quantities in powers of $L/\xi$, where $L$ is the length and $\xi$ the persistence length of the polymer. This requires special procedures for regularizing highly divergent Feynman integrals which we have developed in previous work. We show that by adding to the unperturbed action a correction term ${\cal A}^{\rm corr}$, we can calculate all Feynman diagrams with Green functions satisfying Neumann boundary conditions. Our expansions yield, order by order, properly normalized end-to-end distribution function in arbitrary dimensions $d$, its even and odd moments, and the two-point correlation function

Predictive accuracy of cardiac risk indices for cardiovascular complications in patients undergoing noncardiac surgery

Objective: To compare predictive accuracy of the American Society of Anesthesiologists (ASA) score and various cardiac risk indices for perioperative cardiovascular (CV) complications in patients undergoing noncardiac surgery.Materials and methods: We examined 243 patients (148 men and 95 women) aged 45 to 84 (66 [60-71] years) prior to their elective oncological and vascular surgery. We assessed patients using the ASA physical status classification system, Revised Cardiac Risk Index (RCRI), Gupta Myocardial Infarct or Cardiac Arrest (MICA) calculator, and Khoronenko cardiac risk index and analyzed perioperative CV complications.Results: We detected complications in 30 (12.3%) patients, with 3 (1.24%) of them having 2 concomitant CV complications. One death (0.41%) was registered. The MICA risk calculator had the highest predictive value (AUC ROC = 0.753). Risk scores over 0.95% discriminated patients with perioperative CV complications with sensitivity and specificity of 73.3% and 67.45%, respectively.Conclusions: We recommend using the MICA risk calculator to predict perioperative CV complications following elective oncological and vascular surgery

Quark mass correction to the string potential

A consistent method for calculating the interquark potential generated by the relativistic string with massive ends is proposed. In this approach the interquark potential in the model of the Nambu--Goto string with point--like masses at its ends is calculated. At first the calculation is done in the one--loop approximation and then the variational estimation is performed. The quark mass correction results in decreasing the critical distance (deconfinement radius). When quark mass decreases the critical distance also decreases. For obtaining a finite result under summation over eigenfrequencies of the Nambu--Goto string with massive ends a suitable mode--by--mode subtraction is proposed. This renormalization procedure proves to be completely unique. In the framework of the developed approach the one--loop interquark potential in the model of the relativistic string with rigidity is also calculated.Comment: 34 pages, LATE

Is it possible to assign physical meaning to field theory with higher derivatives?

To overcome the difficulties with the energy indefiniteness in field theories with higher derivatives, it is supposed to use the mechanical analogy, the Timoshenko theory of the transverse flexural vibrations of beams or rods well known in mechanical engineering. It enables one to introduce the notion of a "mechanical" energy in such field models that is wittingly positive definite. This approach can be applied at least to the higher derivative models which effectively describe the extended localized solutions in usual first order field theories (vortex solutions in Higgs models and so on). Any problems with a negative norm ghost states and unitarity violation do not arise here.Comment: 16 pp, LaTeX, JINR E2-93-19

Возможности навигационной транскраниальной магнитной стимуляции в сложных диагностических случаях вовлечения верхнего мотонейрона: клиническое наблюдение

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized with lesions of both upper and lower motor neurons. In accordance with modern diagnostics criteria, only clinical symptoms are used for revealing lesions of the upper motor neuron with the ALS, which often causes serious difficulties. Absence of the pyramidal syndrome does not allow diagnosing ALS, and the diagnosis of progressive muscular atrophy should be set in these cases. We describe a case of an isolated generalized lesion of the lower motor neuron with the signs of cortical motor neurons lesion revealed in the course of navigational transcranial magnetic stimulation. Possible reasons for difficulties in detecting pyramidal syndrome are discussed together with the necessity of working out the criteria of instrumental diagnostics of lesions of the upper motor neuron in ALS.Боковой амиотрофический склероз (БАС) – нейродегенеративное заболевание, характеризующееся поражением как верхнего, так и нижнего мотонейронов. Согласно современным критериям диагностики для выявления поражения верхнего мотонейрона при БАС используют только клинические признаки, что нередко вызывает значительные трудности. Отсутствие пирамидного синдрома не позволяет диагностировать БАС, и в этих случаях ставится диагноз прогрессирующей мышечной атрофии. Описан случай пациентки с изолированным генерализованным поражением нижнего мотонейрона, у которой признаки поражения корковых мотонейронов были выявлены при проведении навигационной транскраниальной магнитной стимуляции. Обсуждаются возможные причины сложностей выявления пирамидного синдрома, а также необходимость разработки критериев инструментальной диагностики поражения верхнего мотонейрона при БАС