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#astro

20 posts20 participants2 posts today
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Rxiv mechanobio

📰 "Modeling transport in weakly collisional plasmas using thermodynamic forcing"
arxiv.org/abs/2504.14000 #Physics.Plasm-Ph #Astro-Ph.He #Astro-Ph.Ga #Force #Cell

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arXiv.orgModeling transport in weakly collisional plasmas using thermodynamic forcingHow momentum, energy, and magnetic fields are transported in the presence of macroscopic gradients is a fundamental question in plasma physics. Answering this question is especially challenging for weakly collisional, magnetized plasmas, where macroscopic gradients influence the plasma's microphysical structure. In this paper, we introduce thermodynamic forcing, a new method for systematically modeling how macroscopic gradients in magnetized or unmagnetized plasmas shape the distribution functions of constituent particles. In this method, we propose to apply an anomalous force to those particles inducing the anisotropy that would naturally emerge due to macroscopic gradients in weakly collisional plasmas. We implement thermodynamic forcing in particle-in-cell (TF-PIC) simulations using a modified Vay particle pusher and validate it against analytic solutions of the equations of motion. We then carry out a series of simulations of electron-proton plasmas with periodic boundary conditions using TF-PIC. First, we confirm that the properties of two electron-scale kinetic instabilities -- one driven by a temperature gradient and the other by pressure anisotropy -- are consistent with previous results. Then, we demonstrate that in the presence of multiple macroscopic gradients, the saturated state can differ significantly from current expectations. This work enables, for the first time, systematic and self-consistent transport modeling in weakly collisional plasmas, with broad applications in astrophysics, laser-plasma physics, and inertial confinement fusion.
Public
Ethan Siegel

How come we’ve never observed a black hole decaying? Black holes, according to Stephen Hawking, should emit radiation from outside their event horizons, ultimately decaying away completely. So why haven't we ever seen it happening? bigthink.com/starts-with-... #space #astro #physics

How come we've never observed ...

Big ThinkHow come we've never observed a black hole decaying?According to Stephen Hawking, spontaneously emitted radiation should cause all black holes to decay. But we've never seen it: not even once.
Public
Starry Time Podcast

Ever see an #astrophotography image and it just feels too... 2D?!

#Chandra & friends have the answer: chandra.harvard.edu/photo/2025

As an example, here is G292.0+1.8, a supernova remnant located in the #constellation #Centaurus (we covered this constellation's #astronomy here: starrytimepodcast.podbean.com/ #mythology here: starrytimepodcast.podbean.com/)

#AstroDon#space#science
Public
Jan Miksovsky

This minimalist static site generator pattern is only for #JavaScript developers who want something small, fast, flexible, and comprehensible jan.miksovsky.com/posts/2025/0

Configuring a complex tool can take more work that just coding the functionality from scratch. Earlier I created a simple blog in #Astro, a popular #SSG. That felt more complicated than the problem justified, so I rewrote the entire #blogging project from scratch in pure JavaScript with 0 dependencies.

This went very well!

Chart comparing size of source code of 22K for zero dependency version and 11K for Astro version
Chart comparing 0 node_modules for zero dependency and 117Mb for Astro version
Public
Ethan Siegel

Is our Universe fundamentally unstable, and will it decay? Our dark energy-rich Universe has a positive amount of energy inherent to space. If that's not the lowest possible value, we may be in huge trouble someday, maybe even soon. bigthink.com/starts-with-... #space #physics #astro

Is our Universe fundamentally ...

Big ThinkIs our Universe fundamentally unstable, and will it decay?Empty space itself, the quantum vacuum, could be in either a true, stable state or a false, unstable state. Our fate depends on the answer.
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