Recent content by Philip Koeck

This sounds quite promising: https://www.unige.ch/~hairer/preprints/relcpd.pdf (https://epubs.siam.org/doi/10.1137/23M1568946). In section 4 they discuss an energy preserving algorithm. Thanks for pointing me in that direction.

I'm simulating a situation that's partly relativistic and I'm wondering if it's wise to use Velocity Verlet. A fast electron (200 keV or roughly 208 000 000 m/s) travels along the z-axis and intersects a beam of slower electrons (1 keV or roughly 20 000 000 m/s) that are moving along the...

I would say the final directions are incompatible with elastic particle collisions. I wouldn't assume that macroscopic energy is conserved.

The problem statement confused me. The wall doesn't move by itself "until they reach equilibrium". The system is already in equilibrium and the wall is moved by an external force, so work is done on the system and it moves to a new equilibrium.

I'm also confused. Why are they not already in equilibrium? Both gases have the same temperature so there should be no heat transfer through the wall. Both gases have the same pressure so the wall shouldn't move. What am I missing?

Not my field at all, but I have a question too. I always thought that the gravitational field and the electrostatic field are both vector fields, but now I read that gravitons build (carry, mediate?) tensor fields. How can the gravitational force be due to a tensor field?

The energy variation is definitely stochastic.

It's for an actual phase plate I'm working on.

Start by writing down the equations for x and y. See where that takes you.

The Kramers Kronig relations in (quantum) optics. Edit: Looks like the KK relations are used for almost everything: https://en.wikipedia.org/wiki/Kramers%E2%80%93Kronig_relations

Maybe I'm overthinking this, but isn't there a fundamental difference here. The energy variation from the source or even due to the specimen doesn't allow me to locate the path of the electron in most cases. However if I have a phase plate that can change the energy of an unscattered electron...

I'm wondering about phase contrast imaging with a transmission electron microscope (TEM). It's generally accepted that phase contrast arises because scattered waves interfere with the unscattered wave when they meet again in the image plane. It's also well established, I believe, that each...

Have you looked at the Conflat standards you can buy from Lesker or Agilent, for example?

Good point! I'm not sure about your example though. There's no reaction going on there, is there? So I can mix water and ethanol at any ratio and it'll stay that way if nothing evaporates. It won't move towards a chemical equilibrium. Or am I missing something? Not really my field, but I like...

In the equilibrium expression for a solution you only need to include the concentration of solutes. The solvent doesn't matter. It has "activity" equal to 1. So the density change of the solvent due to temperature change has very little effect, I would say.