Isotriplet pairing energy of nucleons in nuclei

The problem of describing the nucleon pairing energy in nuclei is considered using a realistic nucleon-nucleon potential that reproduces the parameters of nucleon-nucleon scattering. Satisfactory agreement was obtained between the calculated and experimental values of the isotriplet nucleon pairing energies for even-even nuclei. The analytical representation of the wave functions of the pair allows us to conclude that there are no signs of dineutrons or diproton clustering

Reduced SIR Model of COVID-19 Pandemic

We propose a mathematical model of COVID-19 pandemic preserving an optimal balance between the adequate description of a pandemic by SIR model and simplicity of practical estimates. As base model equations, we derive two-parameter nonlinear first-order ordinary differential equations with retarded time argument, applicable to any community (country, city, etc.).The presented examples of modeling the pandemic development depending on two parameters: the time of possible dissemination of infection by one virus carrier and the probability of contamination of a healthy population member in a contact with an infected one per unit time, e.g., a day, is in qualitative agreement with the dynamics of COVID-19 pandemic. The proposed model is compared with the SIR model

Approximate Solutions of the RSIR Model of COVID-19 Pandemic

The Reduced SIR (RSIR) model of COVID-19 pandemic based on a two-parameter nonlinear first-order ordinary differential equation with retarded time argument is developed. An algorithm aimed to forecast the COVID-19 pandemic development by approximate solution of RSIR model is proposed. The input data for this algorithm are the cumulative numbers of infected people on three dates (e.g., today, a week ago, and two weeks ago)