arXiv subjects

Maxim V. Polyakov

Publications and source records attributed to Maxim V. Polyakov.

At least 19 recordsLinked to original sources

arXiv2025

Computer Modelling of Bioheat Transfer for the Analysis of Brightness Temperature Distributions

This paper presents a comprehensive computer simulation of thermal processes in multilayered biological tissues for the analysis of luminance temperature distributions recorded by microwave radiometry. A mathematical model combining the bioheat transfer equation with the electrodynamic description of electromagnetic field propagation in an inhomogeneous medium has been developed. The model accounts for variations in the thermophysical and dielectric properties of tissues, as well as convective heat exchange with the environment. A parametric analysis was performed to investigate the effects of ambient temperature, heat transfer coefficient, and tissue thermal conductivity on brightness temperature formation. Computational experiments revealed a clear linear dependence of the radiometric signal on both external and internal parameters. It was found that an increase in air temperature by 8 {\deg}C causes a shift in the brightness temperature by about 2 {\deg}C, which exceeds the typical error of the microwave radiometry method and emphasises the need for strict temperature control of the measurement conditions. The developed software system was validated against analytical solutions and experimental data, confirming the accuracy of the calculated temperature fields to within 0.1 {\deg}C. The obtained results lay the groundwork for refining heat transfer models in biological tissues, improving the accuracy of non-invasive thermodiagnostic methods, and integrating computer modelling with machine learning algorithms to enable the automated interpretation of radiometric data.

physics.bio-ph↗

arXiv2025

Numerical Analysis of Antenna Parameter Influence on Brightness Temperature in Medical Microwave Radiometers

This article presents a study on the influence of antenna parameters in medical microwave radiometers on brightness temperature. A series of computational experiments was conducted to analyse the dependence of brightness temperature on antenna characteristics. Various antenna parameters and their effect on the distribution of electromagnetic fields in biological tissues were examined. It was demonstrated that considering the antenna mismatch parameter is crucial when modelling the brightness temperature of biological tissues, contributing about 2 percent to its formation. The depth range of brightness temperature measurement was determined. The dependence of brightness temperature on the antenna diameter and frequency was established. The findings of this study can be applied to improve medical microwave radiometers and enhance their efficiency in the early diagnosis of various diseases.

physics.med-ph↗

arXiv2024

Improving the Efficiency of Oncological Diagnosis of the Breast Based on the Combined Use of Simulation Modeling and Artificial Intelligence Algorithms

The work includes a brief overview of the applications of the powerful and easy-to-perform method of Microwave Radiometry (MWR) for the diagnosis of various diseases. The main goal of this paper is to develop a method for diagnosing breast oncology based on machine learning algorithms using thermometric data, both real medical measurements and simulation results of MWR examinations. The dataset includes distributions of deep and skin temperatures calculated in numerical models of the dynamics of thermal and radiation fields inside a biological tissue. The constructed combined dataset allows us to explore the limits of applicability of the MWR method for detecting weak tumors. We use convolutional neural networks and classic machine learning algorithms (k-nearest neighbors, naive Bayes classifier, support vector machine) to classify data. The construction of Kohonen self-organizing maps to explore the structure of our combined dataset demonstrated differences between the temperatures of patients with positive and negative diagnoses. Our analysis shows that the MWR can detect tumors with a radius of up to 0.5 cm if they are at the stage of rapid growth, when the tumor volume doubling occurs in approximately 100 days or less. The use of convolutional neural networks for MWR provides both high sensitivity ($sens=0.86$) and specificity ($spec=0.82$), which is an advantage over other methods for diagnosing breast cancer. New modified scheme for medical measurements of IR temperature and brightness temperature is proposed for a larger number of points in the breast compared to the classical scheme. This approach can increase the effectiveness and sensitivity of diagnostics by several percent.

physics.med-ph↗

arXiv2023

Simulation tumor growth in heterogeneous medium based on diffusion equation

In the present article the diffusion equation is used to model the spatio-temporal dynamics of a tumor, taking into account the heterogeneous of the medium. This approach makes it possible to take into account the complex geometric shape of the tumor in modeling. The main purpose of the work is demonstration the applicability of this approach by comparing the obtained results with the data of clinical observations. We used an algorithm based on an explicit finite-difference approximation of differential operators for solve the diffusion equation. The ranges of possible values that the input parameters of the model can take to match the results of clinical observations are obtained. It is concluded that the heterogeneity of the physical parameters of the model, in particular the diffusion coefficient, has a significant effect on shape of tumor.

physics.bio-ph↗

arXiv2022

Landscape of heavy baryons from the perspective of the chiral quark-soliton model

We employ the chiral quark-soliton model and the heavy quark symmetry to describe spectra of charm and beauty baryons. Heavy baryons can be classified according to the SU(3) representations of the light sector. We argue that recently discovered $Ξ_b$ states can be interpreted as negative parity excited anti-triplets or sextets, and the $Σ_b$ states as negative parity sextets. Consequences of such assignments for the decay patterns are discussed and also predictions of masses of the yet unmeasured sextet members are given.

hep-ph↗

arXiv2021

Light-cone distribution amplitudes of the nucleon and $Δ$ baryon

We investigate the light-cone wave functions and leading-twist distribution amplitudes for the nucleon and $Δ$ baryon within the framework of the chiral quark-soliton model. The baryon wave function consists of the valence quark and vacuum wave functions. The vacuum wave functions generate all possible higher Fock states by expanding them. We find that it is essential to consider the five-quark component and relativistic corrections to evaluate the distribution amplitudes of the nucleon and $Δ$ isobar. Having taken into account them, we derive the distribution amplitudes. The results are in good agreement with the lattice data.

hep-ph↗

arXiv2021

Exact summation of leading logs around $T\bar T$ deformation of $O(N+1)$-symmetric 2D QFTs

We consider a general (beyond $T\bar T$) deformation of the 2D $O(N+1)$ $σ$-model by the irrelevant dimension-four operators. The theory deformed in this most general way is not integrable, and the $S$-matrix loses its factorization properties. We perform the all-order summation of the leading infrared logs for the $2 \to 2$ scattering amplitude and provide the exact result for the $2 \to 2$ $S$-matrix in the leading logarithmic approximation. These results can provide us with new insights into the properties of the theories deformed by irrelevant operators more general than the $T\bar T$ deformation.

hep-th↗

arXiv2021

A bound on the nucleon Druck-term from chiral EFT in curved space-time and mechanical stability conditions

Using dispersive representations of the nucleon gravitational form factors, the results for their absorptive parts from chiral effective field theory in curved space-time, and the mechanical stability conditions, we obtain a model independent inequality for the value of the gravitational $D(t)$ form factor at zero momentum transfer (Druck-term). In particular, the obtained inequality leads to a conservative bound on the Druck-term in the chiral limit $D \leq -0.95(9)$. This bound implies the restriction on the low-energy constant $c_8$ of the effective chiral action for nucleons and pions in the presence of an external gravitational field, $c_8\leq -1.1(1)$ GeV$^{-1}$. For the physical pion mass we obtain a model independent bound $D\leq -0.20(2)$.

hep-ph↗

arXiv2021

Forces inside the nucleon on the light front from 3D Breit frame force distributions: Abel tomography case

We derive simple relations which express 2D light front force distributions in terms of 3D Breit frame pressure and shear force distributions. Mathematically the relations correspond to invertible Abel transformation and they establish one-to-one mathematical equivalence of 3D Breit frame force distributions and 2D light front ones. Any knowledge (model calculation, experimental measurement, etc.) about pressure and shear force distributions in Breit frame can be unambiguously transformed into light front force distributions with the help of Abel transformation. It is important that the transformation ensures 2D stability conditions if the 3D stability conditions are satisfied. As an illustration of how the relations work, we calculated the light front force distributions for a large nucleus as a liquid drop, and for large $N_c$ nucleon as a chiral soliton.

hep-ph↗

arXiv2020

On the second Gegenbauer moment of $ρ$-meson distribution amplitude

Using the soft pion theorem, crossing, and the dispersion relations for the two pion distribution amplitude ($2π$DA) we argue that the second Gegenbauer moment the $ρ$-meson DA ($a_2^{(ρ)}$) most probably is negative. This result is at variance with the majority of the model calculations for $a_2^{(ρ)}$. Using the instanton theory of the QCD vacuum, we computed $a_2^{(ρ)}$ at a low normalisation point and obtain for the ratio $ a_2^{(ρ)}/M_3^{(π)}$ {\it definitely negative value} in the range of $a_2^{(ρ)}/M_3^{(π)}\in [-2, -1]$. The range of values corresponds to a generous variation of the parameters of the instanton vacuum. The value of the second Gegenbauer moment of pion DA is positive in the whole range and is compatible with its the most advanced lattice measurement. It seems that the topologically non-trivial field configurations in the QCD vacuum (instantons) lead to qualitatively different shapes of the pion and the $ρ$-meson DAs.

hep-ph↗

arXiv2020

Quadrupole pressure and shear forces inside baryons in the large $N_c$ limit

We derive number of relations between quadrupole energy, elastic pressure, and shear force distributions in baryons using the large $N_c$ picture of baryons as chiral solitons. The obtained large $N_c$ relations are independent of particular dynamics and should hold in any picture in which the baryon is the chiral soliton. One of remarkable qualitative predictions of the soliton picture is the nullification of the tangential forces acting on the radial area element for any tensor polarisation of the baryon. The derived relations provide a powerful tool to check the hypothesis that the baryons are chiral solitons, say using lattice QCD.

hep-ph↗

arXiv2020

Strong force fields and stabilities of the nucleon and singly heavy baryon $Σ_c$

We investigate the strong force fields and stabilities of the nucleon and the singly heavy baryon $Σ_c$ within the framework of the chiral quark-soliton model. Having constructed the pion mean fields in the presence of the $N_c-1$ level quarks self-consistently, we are able to examine the gravitational form factors of $Σ_c$. We mainly focus in the present work on the stability conditions for both the nucleon and $Σ_c$ and discuss the strong force fields and their physical implications. We also present the results for the gravitational form factors and relevant observables, emphasising the difference between the nucleon and $Σ_c$.

hep-ph↗

arXiv2020

Nucleon quasi-Parton Distributions in the large N$_c$ limit

In this letter, we investigate the nucleon quasi-parton distribution functions in the chiral quark soliton model. We derive a set of sum-rules depending on the velocity of the nucleon and on the Dirac matrix defining the distribution functions. We present numerical results for the isosinglet unpolarized distribution, in which we find that the anti-quark distribution breaks the positivity condition at nucleon velocities $v\approx 0.99\;(P_N\approx 7.0 M_N)$ and smaller. We found that, for the isosinglet unpolarized case, a large nucleon momentum is required for the quasi-parton distribution to get close enough to the usual parton distribution function.

hep-ph↗

arXiv2020

Probing Nucleons and Nuclei in High Energy Collisions

This volume is a collection of contributions for the 7-week program "Probing Nucleons and Nuclei in High Energy Collisions" that was held at the Institute for Nuclear Theory in Seattle, WA, USA, from October 1 until November 16, 2018. The program was dedicated to the physics of the Electron Ion Collider (EIC), the world's first polarized electron-nucleon (ep) and electron-nucleus (eA) collider to be constructed in the USA. These proceedings are organized by chapters, corresponding to the weeks of the program: Week I, Generalized parton distributions; Week II, Transverse spin and TMDs; Week III, Longitudinal spin; Week IV, Symposium week; Weeks V & VI, eA collisions; Week VII, pA and AA collisions. We hope these proceedings will be useful to readers as a compilation of EIC-related science at the end of the second decade of the XXI century.

hep-ph↗

arXiv2019

New LHCb pentaquarks as hadrocharmonium states

New LHCb Collaboration results on pentaquarks with hidden charm [1] are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario [2,3]. In the new data the old LHCb pentaquark $P_c(4450)$ splits into two states $P_c(4440)$ and $P_c(4457)$. We interpret these two almost degenerate hadrocharmonium states with $J^P=1/2^-$ and $J^P=3/2^-$ as a result of hyperfine splitting between hadrocharmonium states predicted in [2]. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting [2,3] that is compatible with the experimental data. The new $P_c(4312)$ state finds a natural explanation as a bound state of $χ_{c0}$ and a nucleon, with $I=1/2$, $J^P=1/2^+$ and binding energy 42 MeV. As a bound state of a spin-zero meson and a nucleon, hadrocharmonium pentaquark $P_c(4312)$ does not experience hyperfine splitting. We find a series of hadrocharmonium states in the vicinity of the wide $P_c(4380)$ pentaquark that can explain its apparently large decay width. We compare the hadrocharmonium and molecular pentaquark scenarios and discuss their relative advantages and drawbacks.

hep-ph↗

arXiv2019

Gravitational form factors of a spin one particle

We define the form factors of the quark and gluon symmetric energy-momentum tensor (EMT). The static EMT is related to the spatial distributions of energy, spin, pressure and shear forces. They are obtained in the form of a multipole expansion. The relations between gravitational form factors and the generalised parton distributions are given.

hep-ph↗

arXiv2019

On tetraquarks with hidden charm and strangeness as phi-psi(2S) hadrocharmonium

In the hadrocharmonium picture a $\bar cc$ state and a light hadron form a bound state. The effective interaction is described in terms of the chromoelectric polarizability of the $\bar cc$ state and energy-momentum-tensor densities of the light hadron. This picture is justified in the heavy quark limit, and may successfully account for a hidden-charm pentaquark state recently observed by LHCb. In this work we extend the formalism to the description of hidden-charm tetraquarks, and address the question of whether the resonant states observed by LHCb in the $J/ψ$-$ϕ$ spectrum can be described as hadrocharmonia. This is a non-trivial question because nothing is known about the $ϕ$ meson energy-momentum-tensor densities. With rather general assumptions about energy-momentum-tensor densities in the $ϕ$-meson we show that a $ψ(2S)$-$ϕ$ bound state can exist, and obtain a characteristic relation between its mass and width. We show that the tetraquark $X(4274)$ observed by LHCb in $J/ψ$-$ϕ$ spectrum is a good candidate for a hadrocharmonium. We make predictions which will allow testing this picture. Our method can be generalized to identify other potential hadrocharmonia.

hep-ph↗

arXiv2019

Exact summation of leading infrared logarithms in 2D effective field theories

A method of exact all-order summation of leading infrared logarithms in two dimensional massless $Φ^4$-type non-renormalizable effective field theories (EFTs) is developed. The method is applied to the ${\rm O}(N)$-symmetric EFT, which is a two-dimensional sibling of the four dimensional ${\rm O}(N+1)/{\rm O}(N)$ sigma-model. For the first time the exact all-order summation of the $\left(E^{2} \ln(1/E)\right)^n$ contributions (chiral logarithms) for the $2 \to 2$ scattering amplitudes is performed in closed analytical form. The cases when the resulting amplitudes turn to be meromorphic functions with an infinite number of poles (Landau poles) are identified. This provides the first explicit example of quasi-renormalizable field theories.

hep-ph↗