nchagnet

Regarding the "why the action is this object" part of the question, I find that the easiest way to think about it is from the Hamiltonian perspective. There you can think of it as minimising energy along a trajectory. From that point, a Lagrangian is just a mathematical trick to express the symplectic structure differently.

But if your question was more about "why minimizing something yields trajectories", I personally would argue this is beyond physics. As an empirical science, physicists have seen this kind of behaviour broadly (optics, classical mechanics, quantum mechanics) and just unified it as an overarching principle.

Finally regarding the proof to newtonian mechanics, I don't have anything handy from the pure Newtonian perspective beyond the usual "minimises the lagrangian and your equations of motions look the same". However, you might be interested in proofs which show newtonian gravity as low energy approximation of general relativity. And since general relativity has a nice action formulation, it all gets nicely tied in.

Hope this helps!

I generally agree with your point on ease of experimentation, but if we insist on calling it software engineering, then maybe the field needs to adhere to engineering principles, as the GP highlighted.

Interesting that they just skipped the entire Verstappen dominance era, but decided instead to jump to the budgeoning McLaren Piastri-Norris dominance (about a year old only).

Of course with 75 years of history you need to trim it down, but that's an interesting choice...

I would argue the latter one is quite the interesting project from a US interests perspective. I've personally been hearing and reading a lot about the possible impact of climate change on the artic region in terms of resource availability and even transport channels (an arctic passageway would be huge).

This is such a cool project! Congrats!

That'd be a good start. This article is well anchored within geometrodynamics (the theories which attempt to explain all physics as geometry), so maybe making that clear would avoid confusions already.

Sadly no, most examples I'm familiar with are within research articles. A typical thing done within such articles is to consider a spacetime geometry, calculate its Einstein tensor and map it to some ansatz like that of a perfect relativistic fluid. It's a neat way to interpret the geometry in question as an energy/matter content.

Hope that helps point you in the correct direction!

This is what I was trying to convey: this is already how we think about it.

In general relativity, mass is not more fundamental than the gravitational field and its curvature. While we generally speak of spacetime curving because of mass, this doesn't mean this is a one way relation. The stress energy tensor is equal to the Einstein tensor (roughly curvature), so the relationship is already two-way.

It's a cool thing to think about of course, just wanted to clarify.

This is already sort of the case. Of course it's not as immediate a comparison, but in the same way that charge sources the divergence of the electric field (Maxwell's equations), mass-energy are sources of the Einstein equations involving the curvature. It's the same reasoning and something we generally already consider.

The title of the phys.org article is a bit more misleading than the article itself (when are they not).

What the authors did is build a unified setup for classical gravity and electromagnetism as the solution of one action, under specific assumptions (Weyl geometry, etc...). Usually we consider gravity as the curvature of spacetime, and electromagnetic forces as the curvature of the electromagnetic field. The authors built something elegant where you can get both in one go.

What this work doesn't do is as important as what it does given the "ambitious" title. The authors' work is interesting, but a casual interpretation of the title would really mislead people into thinking they solved the unification problem.

This work doesn't address other forces or the general particularities of the standard model and how they would also bundle. The second thing it doesn't answer is how to quantize any of these fields (gravity is notoriously difficult to quantize for many reasons).

You do understand that this is explicitly mandated by the law and only in special cases can this be lifted (and here the judge mentioned the lack of remorse or admission from the defendant was a deciding factor for this)? Here is a reference for that: https://www.vie-publique.fr/questions-reponses/297965-inelig...

Why do you need a signin to search the recipes? What does it bring to the experience besides bookmarks?

This is really interesting! You mention using LLMs to parse sentences in strongly typed prompts, but how would this work with the prevalence of tolerated grammatical errors in most languages? Would such a parsing always be "pass/fail" or would you be able to get a degree of correctness?

This argument could be made for healthcare, postal services, and even emergency services. Thankfully in Europe we don't agree with that view. Entrepreneurship is an important engine for innovation, but it doesn't mean our collective representation cannot fund projects which serve the whole community if we see fit.

Thankfully it's tax euros!

I get your point, and I agree to some extent, but I also don't think it has to be black and white. I don't really trust the French government to fund such projects long-term, but at the same time private companies create and end services all the time (looking at you Google). So within those parameters, this doesn't seem like a bad thing.

And regarding the economy, my understanding is that there's been a push in the French government (and in Europe to some extent) towards more independent services (the recent behaviour of US big tech are not helping for sure). If the government is going to generate some tool for its internal use, I sure would prefer if they open sourced it at the same time.

Finally for the WhatsApp alternative, if France or Germany or whoever else started an open source WhatsApp competitor with better encryption, I definitely think it would be good for European citizens: one less dependency on Meta. Why wouldn't we want that?

This is a really great project from both the French and German governments.

I think state-funded open source solutions to digital platforms is a fantastic opportunity to get away from the big tech walled gardens. Of course, there is always the risk that this becomes unmaintained in the future, but the community at least can take over. But until then, it's a nice platform and a nice contribution to the community.

So there are two aspects to reconcile the solid and fluid parts together.

First, just like a superfluid, a supersolid can have a portion that flows and one that doesn't (the normal fraction).

The second part is that, as you rightfully mentioned, holes are just vacancies in the structure. Here the vacancies in the crystalline structure they made are able to flow along the solid. But as they flow, the structure retains its shape. And at low enough temperature, these excitations condense into a macroscopic quantum state which makes them a superfluid.

So in a nutshell, you have an organised structure like a solide, but a portion of that structure flows without breaking the overall structure.

If it can help:

- Supersolid: it's a state of matter when a system is both organised like a solid but presents superfluid-like flow without viscosity.

- Driven-dissipative: it's a qualifier for systems which are dissipative (excitations of the systems dissipate energy as heat) and driven by external fields (in this case strong electromagnetic fields are keeping the supersolid in shape). In physics, "driven" usually refers to an external influx of energy or force kept on the system.

- non-equilibrium system is what we call systems where the physics cannot be fully described by a statistical analysis of the whole over long times. These systems have transitory behaviours which are often complex before they return to equilibrium (unless they are driven away from it).

Exciton-polariton: excitons and polaritons are what we call quasiparticles. They're not particles in the sense of an electron or photon, but instead they are excitations of the collective system which look like particles. Kind of like how waves on the ocean aren't one water molecule, but a bunch of them. An exciton has no charge (it's essentially an electron and a missing electron stuck together). When an exciton couples to electromagnetic waves (photons), it can make a special type of polariton (another quasiparticle) which we call an exciton-polariton.

- Photonic = made of photons

This looks like a neat library! I really like the inheritance aspect, seems quite useful to define standard flags and arguments.

Agreed with you, although I'd say there is a spectrum between "do everything the hardest way" and "don't learn anything". I think LLM-based tools can be a great time-saver for boilerplate repetitive code, and they can sometimes help you get a first draft of some implementation you're not fully seeing yet, but you definitely should not rely on them to write the whole code for you if you want to learn.

To be fair, whether you disagree with it or not, this is the spirit of the law: ostensible religious symbols are not allowed in public schools (and more generally in republican institutions). So yes, one symbol is more visible than others, and that makes it somewhat unfair, but the "visible" portion is realistic. You can't ask teachers to check under student's clothes for them.

I will agree though that France has also been very reactionary towards its Muslim population and laicity has been a convenient tool to bash them. But that doesn't invalidate the purpose of the original principle.

Add to that the licensing of conda. In my company, we are not allowed to use conda because the company would rather not pay, so might as well use some other tool which does things faster.

At least pertaining to vinyls, this seems to mostly discuss practical and technical aspects, but misses the more "ceremonial" aspect which in my opinion explains its popularity. Buying a physical record requires some intent and choice which you don't have in a spotify catalogue of millions of tracks. And playing a record has this physical action aspect a lot of people cherish: I enjoy it because it feels like a treat I set up for myself.

I fully agree with the comments in that post. I started studying them because, well, they sound really cool, but my first impression was definitely that this sounded like a lot of effort (computationally) to solve a single equation. But then I only tested on simple equations where traditional solvers have no difficulties.

In my previous position, we studied the behaviour of black holes with exotic geometries, and we never could make our solvers work with the added time dependence. I would be very curious to see how a PINN would have fared on this (given enough compute time of course).

Thank you!

As far as I can tell, PINNs are promising and an active research area, but they are also young and far from being as widely adopted as finite element methods (at least that's my experience academic environments).

I do see great improvements are being made both on the performance level but also on the applications.

One aspect I didn't discuss in the post is the use for inverse solution search, where you fit experimental data to your equation, and where your parameters and your initial conditions can also be trainable parameters. This has great potential to improve the methodology of experimental results analysis.

I agree with the general feeling from other commenters that a blog should first and foremost be an activity you do for yourself. It's a great way to organize your thoughts and truly reflect on them.

I have been trying to start my own recently (https://nchagnet.pages.dev/blog), mostly because I used to write research articles and I miss that feeling at the end of a project to wrap it up with some piece of writing you are proud of. I am still looking for my voice, but it has definitely been fun!