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Abstract: The key model for particle populations in statistical mechanics is the Bogolyubov–Born–Green–Kirkwood–Yvon (BBGKY) equation chain. It is derived mainly from the Hamilton ordinary differential equation (ODE) system for the particle states in the position-momentum phase space. Many problems beyond physics or chemistry, for instance, in the living-matter sciences (biology, medicine, ecology, and sociology) make it necessary to extend the notion of a particle to an individual, or active particle. This challenge is met by the generalized kinetic theory. The corresponding dynamics of the state vector can also be regarded to be described by an ODE system. The latter, however, need not be the Hamilton one. The question is how one can derive the analogue of the BBGKY paradigm for the new settings. The present work proposes an answer to this question. It applies a very limited number of carefully selected tools of probability theory and common statistical mechanics. It also uses the well-known feature that the maximum number of the individuals which can mutually interact directly is bounded by a fixed value of a few units. The proposed approach results in the finite system of equations for the reduced many-individual distribution functions thereby eliminating the so-called closure problem inevitable in the BBGKY theory. The thermodynamic-limit assumption is not needed either. The system includes consistently derived terms of all of the basic types known in kinetic theory, in particular, both the “mean-field” and scattering-integral terms, and admits the kinetic equation of the form allowing a direct chemical-reaction reading. The approach can deal with Hamilton’s model which is nonmonogenic. The results may serve as the basis of the generalized kinetic theory and contribute to stochastic mechanics of populations of individuals. [Copyright &y& Elsevier]

Abstract: Homeorhesis is a necessary feature of any living system. If a system does not perform homeorhesis, it is nonliving. The present work develops the sufficient conditions for the ODE model to describe homeorhesis and suggests the structure of the model. The proposed homeorhesis model is fairly general. It treats homeorhesis as piecewise homeostasis. The model can be specified in different ways depending on the specific system and specific purposes of this analysis. An example of the specification is the PhasTraM model, the homeorhesis-aware nonlinear reaction–diffusion model for hyperplastic oncogeny in the previous works of the author. The qualitative agreement of the developed homeorhesis model with the living-system experimental results is noted. The work also shows that the basic mathematical models (such as the active-particle generalized kinetic theory) are substantially more important for the living-matter studies than in the case of nonliving matter. A few directions for future research are suggested as well. [Copyright &y& Elsevier]

Abstract: Many features of living systems prevent the application of fundamental statistical mechanics (FSM) to study such systems. The present work focuses on some of these features. After discussing all the basic approaches of FSM, the work formulates an extension of the kinetic theory paradigm (based on the reduced one-particle distribution function) that exhibits all of the living-system properties considered. This extension appears to be a model within the generalized kinetic theory developed by N. Bellomo and his co-authors. In connection with this model, the work also stresses some other features necessary for making the model relevant to living systems. A mathematical formulation of homeorhesis is also derived. An example discussed in the work is a generalized kinetic equation coupled with a probability-density equation representing the varying component content of a living system. The work also suggests a few directions for future research. [Copyright &y& Elsevier]