arXiv subjects

Aleš Mohorič

Publications and source records attributed to Aleš Mohorič.

3 recordsLinked to original sources

arXiv2026

Stellar structure, magnetism and the variational principle

Matter interacts through two long range forces: gravity and electromagnetism. While all matter contributes to the gravitational potential, electromagnetic effects were traditionally expected to cancel in large systems because positive and negative charges balance. Yet astrophysical objects clearly show long range electromagnetic behavior, so the cancellation cannot be perfect. This paper develops a model for stationary aggregation of matter into a star that consistently includes angular momentum and electromagnetic effects. We reformulate the standard polytropic stellar model as a variational problem and extend it to include the kinetic energy of rigid rotation and the electromagnetic interaction energy between oppositely charged baryonic matter. The electromagnetic contribution to the action is taken to be the minimal energy required to generate the stellar magnetic dipole moment. This energy has two parts: the pure electromagnetic contribution, expressible as a surface integral, and the free energy difference between magnetized and unmagnetized matter, obtained by analyzing a degenerate electron gas in a background of cold ions. Differential forms provide a convenient mathematical framework. The resulting model incorporates electromagnetic effects into stellar structure in a way consistent with linearized general relativity. Although the full system forms a complex open boundary problem, exact solutions exist under simplifying assumptions. The phase diagram predicted by the simplified model shows patterns that may motivate further study of the balance between matter, gravitation, and electromagnetism

astro-ph.SR↗

arXiv2019

Molecular velocity auto-correlations in glycerol/water mixtures studied by NMR MGSE method

Molecular dynamics in binary mixtures of water and glycerol was studied by measuring the spectrum of water velocity auto-correlation in the frequency range from 0.05 to 10 kHz by using the NMR method of modulated gradient spin echo. The method shows that the diversity of diffusion signature in the short spin trajectories provides information about heterogeneity of molecular motion due to the motion in the micro-vortexes of hydrodynamic fluctuation, which is especially pronounced for the mixtures with the low glycerol content. As concentration of glycerol increases above 10vol%, a new feature of spectrum appears due to interaction of water molecules with the clusters formed around hydrophilic glycerol molecules. New spectrum exposes a rate thickening of molecular friction, according to Einstein-Smoluchowski-Kubo formula, which inhibits rapid molecular motions and creates the conditions for a slow process of spontaneously folding of disordered poly-peptides into biologically active protein molecules when immersed in such a mixture.

cond-mat.stat-mech↗

arXiv2018

Molecular velocity auto-correlation of simple liquids observed by NMR MGSE method

The velocity auto-correlation spectra of simple liquids obtained by the NMR method of modulated gradient spin echo show features in the low frequency range up to a few kHz, which can be explained reasonably well by a $t^{-3/2}$ long time tail decay only for non-polar liquid toluene, while the spectra of polar liquids, such as ethanol, water and glycerol, are more congruent with the model of diffusion of particles temporarily trapped in potential wells created by their neighbors. As the method provides the spectrum averaged over ensemble of particle trajectories, the initial non-exponential decay of spin echoes is attributed to a spatial heterogeneity of molecular motion in a bulk of liquid, reflected in distribution of the echo decays for short trajectories. While at longer time intervals, and thus with longer trajectories, heterogeneity is averaged out, giving rise to a spectrum which is explained as a combination of molecular self-diffusion and eddy diffusion within the vortexes of hydrodynamic fluctuations.

cond-mat.soft↗