Does a container of ideal gas increase in temperature when accelerated and stopped?

An insulated container consisting of two ideal gas atoms are used. It is shown using rectilinear motion and elastic collisions with the walls of the container how the root mean square speed of the atoms change during acceleration of the container and after the container comes to a sudden stop.

Collisions of Nucleons with Atoms: Calculated Cross Sections and Monte Carlo Simulation

After a summary description of the theory of elastic collisions of nucleons with atoms, we present the calculation of a generic database of differential and integrated cross sections for the simulation of multiple elastic collisions of protons and neutrons with kinetic energies larger than 100 keV. The relativistic plane-wave Born approximation, with binding and Coulomb-deflection corrections, has been used to calculate a database of proton-impact ionization of K-shell and L-, M-, and N-subshells of neutral atoms These databases cover the whole energy range of interest for all the elements in the periodic system, from hydrogen to einsteinium (Z = 1–99); they are provided as part of the penh distribution package. The Monte Carlo code system penh for the simulation of coupled electron-photon-proton transport is extended to account for the effect of the transport of neutrons (released in proton-induced nuclear reactions) in calculations of dose distributions from proton beams. A simplified description of neutron transport, in which neutron-induced nuclear reactions are described as a fractionally absorbing process, is shown to give simulated depth-dose distributions in good agreement with those generated by the Geant4 code. The proton-impact ionization database, combined with the description of atomic relaxation data and electron transport in penelope, allows the simulation of proton-induced x-ray emission spectra from targets with complex geometries.

Relative entropy of freely cooling granular gases. A molecular dynamics study

Whereas the original Boltzmann’s H-theorem applies to elastic collisions, its rigorous generalization to the inelastic case is still lacking. Nonetheless, it has been conjectured in the literature that the relative entropy of the velocity distribution function with respect to the homogeneous cooling state (HCS) represents an adequate nonequilibrium entropy-like functional for an isolated freely cooling granular gas. In this work, we present molecular dynamics results reinforcing this conjecture and rejecting the choice of the Maxwellian over the HCS as a reference distribution. These results are qualitatively predicted by a simplified theoretical toy model. Additionally, a Maxwell-demon-like velocity-inversion simulation experiment highlights the microscopic irreversibility of the granular gas dynamics, monitored by the relative entropy, where a short “anti-kinetic” transient regime appears for nearly elastic collisions only.

New Thermodynamics: Inelastic Collisions and Cosmology

The sciences have evolved around elastic collisions although most collisions are inelastic. Elastic collisions allow for simpler mathematical modelling, that may not be particularly suitable for cosmology. Inelastic collisions create photons. This has led to consideration of an ensemble of inelastic collisions producing CMB. This will further lead to brief discussions concerning the nature of dark matter, and dark energy. This will then be followed by a simpler analogy concerning the creation of Hawking’s radiation. A consequence of collisions being inelastic is that as a mathematical contrivance, entropy may only be an approximation when applied to the real world. And this fits well with this author’s “New Thermodynamics”.

New Thermodynamics: Inelastic Collisions, Blackbody Radiation, Entropy and Light

Most collisions that we witness are inelastic. Irrationally, the sciences have evolved around elastic collisions, which allows for simpler mathematical modelling. Since a result of inelastic collisions are photons, we examine the feasibility of an ensemble of inelastic collisions producing a blackbody spectrum. This will lead to reconsideration of how the light that governs our lives is produced, i.e., light from both the stars and incandescent lightbulbs. A brief discussion of entropy being a mathematical contrivance based upon elastic collisions is included. A consequence of collisions being inelastic becomes, entropy can only be an approximation when applied to the real world. And this fits well with “New Thermodynamics”.