2born (2born) wrote,

Парочка педагогически полезных статеек с матфизическим содержанием

A Unified View of Transport Equations: https://arxiv.org/abs/1906.06541

Distribution functions of many static transport equations are found using the Maximum Entropy Principle. The equations of constraint which contain the relevant dynamical information are simply the low-lying moments of the distributions. Systems subject to conservative forces have also been considered.

Why pushing a bell does not produce a sound: https://arxiv.org/abs/1906.06837

The difference between "beating" and "pushing" results in the perception that a push just makes the object move as a whole, while a beat produces also a sound. Through a detailed analysis of the physics underlying such everyday experiences, we identify the \emph{strength}, the \emph{duration} and the \emph{softness} of the applied contact force, as the main (measurable) characteristics that mark such difference. The strength determines the final velocity Δv achieved by the body. The duration 2τ compares to the time τℓ the sound takes to cross the body. The softness γ (a positive exponent) results from the shape in time of the contact force. Those three elements enter the formula for the intensity of the sound produced. The relevant role of the softness is stressed and specific values are calculated for a thin metallic bar, chosen as the simplest possible model system.
Tags: Мегаучебник или Что я читал и похвалил, разгребая arXiv'ы

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