Are Quasiparticles Real?

I'm posting this because someone here (@dougnatelson) can respond to this. This is based on this article that asks if quasiparticle are real.

In much the same way, "quasiparticles can only exist within some medium or material, because they are built up from the response of that material's constituents or building blocks," Natelson said; in contrast, particles such as electrons and protons "can exist in free space."

In other words, quasiparticles can't exist in a vacuum and they can't exist on their own. They're reliant on particles acting together and being in a material where they can emerge, just as a wave carried out in a stadium can only exist when there is a group of people there who can perform it.

As a condensed matter physicist, I'm quite familiar with the concept of "quasiparticles", since we deal with electrons, "holes", etc. that undergo many-body interactions. It is why, for example, charge carriers in solids have "effective mass", which is typically not the "bare mass" of the charge carrier, but the "normalized" mass due to such many-body interactions. In essence, we have reduced one many-body problem into many one-body problem by lumping the complicated many-body interactions into this new particle's mass. This particle is often called the "quasiparticle".

But the above is a highly simplified picture. Some people would say that this is the Fermi Liquid model of quasiparticles where the strength of the coupling between the particle and the many-body interactions are "weak", allowing for such simplification. This is no longer true for particles with strong interactions where the Fermi Liquid model breaks down (marginal Fermi Liquid and so on). Therefore, it can get very complicated, especially when you add particles in reduced dimensions (2D and 1D).

I like this article because it highlights a very basic concept in condensed matter physics that does not get the appropriate publicity. However, the one issue that is missing is the explanation on what we mean by "real". Is an electron "real" based on what we measured the "bare electron" properties? After all, if we buy into the idea of quantum field theory, even a bare electron has its own vacuum interactions. This leads to the crazy idea that particles actually are all the result of some kind of many-body interactions themselves, i.e. they are quasiparticles!

Instead of worrying whether something is "real", whatever that means, we should be focusing on fact that we can measure such-and-such properties of such-and-such a thing. The measurements, or rather, the outcome of the measurements are real for they can be reproduced. The measurements represent the characteristics and properties of the entity that we are measuring. Maybe this is carrying empiricism to the extreme, but it beats trying to convince people that it is "real".

😊

Zz. 

 

Entanglement and Experiment

The AIP has produced one of the most informative historical account of the history of quantum entanglement after EPR, especially on its development before Bell came up with his infamous inequality test. It is a two-parter, so you definitely want to read both.

Entanglement and experiment, part 1: Before Bell

Entanglement and experiment, part 2: Oral history of the first Bell tests

What I was not aware of was the early experiment by Chien-Shiung Wu in this area. She is definitely one of the giants of physics that should have been awarded the Nobel Prize. I'm glad this article finally gives her the recognition that she deserves, and it certainly gives me even more reason to admire her accomplishments.

Zz. 

ChatGPT Is Still Not Very Good With Sketching

I gave this prompt to ChatGPT:

Sketch an object moving in a circular path, showing the tangential velocity at 4 different points along its path.

This was the image that it gave me:

 

I then gave what I thought a simpler prompt:

sketch an object moving in a circular path having a centripetal force

... and this was what I got:

 

 

I guess it is worth a giggle.

Zz. 

Astrophotgraphy - As If I Need A New Hobby

I got the new Dwarf Mini smart telescope for my birthday this year. I never had a desire for a telescope before even though images of these remote places in our universe had always fascinated me. It also helps that I teach basic Astronomy for students wanting a GED science credits.

However, when I came across videos of the Dwarf Mini and saw how compact and stylish it was, I made a mistake of expressing my fascination to it to the people around me and voila! It showed up as a birthday present!

Ever since a month ago, I have been fiddling around with it and have really gotten into this astrophotography thing. I must say, it has been quite fascinating and educational, because I ended up reading about the stuff that I photographed.

Anyhow, here are a few pictures that I've taken so far. Mind you, we have not been getting a lot of clear skies so far, and on days that we do have them, they have been rather chilly except for a few days. I'm hoping this will change soon now that this is the first day of Spring.

The telescope came with a solar filter which allows me to take a snapshot of the Sun. Here comes the Sun, with a few sun spots!

 

Next comes the closest spiral galaxy to the Milky Way, the Andromeda galaxy (M31), which Edwin Hubble discovered to be at a location much further than the size of the Milky Way and thus, proving that this not not part of our galaxy. I've removed the stars in the photo, but you'll notice that the image kept two additional galaxies.

This next one is the one that was at the top of my list. This is the Orion Nebula (M42), a star nursery in the Orion constellation. This is a popular shot because it is one of the brightest nebula for astrophotography. I was quite impressed by what the Dwarf Mini was able to do.

Finally, this was obtained just last night. We had clear skies, and so I wanted to see if we could capture the Rosette Nebula (NGC 2237). We got it, but I think we needed to go twice as long to get a better and clearer image.

Except for the Sun, each one of these images took about 1 hour and 15 minutes to complete. The telescope basically tracked and stacked a series of images that it took. Each image had about 15-30-second exposure time. I left it up to the telescope auto settings for each of the items store in its library.

My next goal is to capture a few more galaxies, maybe an elliptical one, or even the Magellenic cloud (LMC) and see how that looks.

Zz.