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Where is Noether's principle in machine learning?

cgad.ski

11–20 of 81 posts

Re: Where is Noether's principle in machine learning?

#11
post #9

As a complete amateur I was wondering if it could be possible to use that property of light ("to always choose the most optimal route") to solve the traveling salesman problem (and the whole class of those problems as a consequence). Maybe not with an algorithmic approach, but rather some smart implementation of the machine itself.

If somehow you can ensure that light can only reach a point by travelling through all other points then yes.

It's basically the same way you could use light to solve a maze, just flood the exit with light and walk in the direction which is brightest. Works better for mirror mazes.

Re: Where is Noether's principle in machine learning?

#12
post #10
post #9

As a complete amateur I was wondering if it could be possible to use that property of light ("to always choose the most optimal route") to solve the traveling salesman problem (and the whole class of those problems as a consequence). Maybe not with an algorithmic approach, but rather some smart implementation of the machine itself.

This sounds a bit like LIDAR implementations, I assume you mean something similar at a smaller scale, where physical obstacles provide a "path" representation of a problem space?

Yup, something like that came to my mind first: create a physical representation (like a map) of the graph you want to solve and use physics to determine the shortest path. Once you have it you could easily compute the winning path's length etc.

Re: Where is Noether's principle in machine learning?

#13
post #3

Earlier quoted context omitted.

Yeah, I've been thinking about similar concepts in a different context. Fascinating. Regarding the role of time, the idea of a purely conserved quantity is that it is conserved under the conditions of the system (that's why the article frequently references Newton's First Law), so they're generally held "for all time that these symmetries exist in the system". Specifically on time: the invariant for systems that exhi…

Here's my ELI5 attempt of the time/energy relation: imagine a spring at rest (not moving) strike the spring, it's now oscillating the system now contains energy like a battery what is energy? it's stored work potential the battery is storing the energy, which can then be taken out at some future time the spring is transporting the energy through time in fact how do we measure time? with clocks. What's a clock? It's a…

Symmetry exists abstractly, apart from time.

There are many machine learning problems which should have symmetries: a picture of a cow rotated 135 degrees is still a picture of a cow, the meaning of spoken words shouldn't change with the audio level, etc. If they were doing machine learning on tracks from the LHC the system ought to take account of relativistic momentum and energy.

Can a model learn a symmetry? Or should a symmetry just be built into the model from the beginning?

Re: Where is Noether's principle in machine learning?

#14

This is one of those links where just seeing the title sets you off, thinking about the implications. I'm going to have to spend more time digesting the article, but one thing that jumps out at me, and maybe it's answered in the article and I don't understand it, is the role of time. Generally in physics, you're talking about a quantity being conserved over time, and I'm not sure what plays the role of time when you'…

"I'm now wondering if in something like Sora that can do a kind of physical modeling, if there's some conserved quantity in the neural network that is _directly analogous_ to conserved quantities in physics"

My first thought on reading that was that if there was it would be interesting to see if there was some way it tied into the concept of us living in a simulation, i.e. we're all living in a complex ML network simulation.

Re: Where is Noether's principle in machine learning?

#15

This is one of those links where just seeing the title sets you off, thinking about the implications. I'm going to have to spend more time digesting the article, but one thing that jumps out at me, and maybe it's answered in the article and I don't understand it, is the role of time. Generally in physics, you're talking about a quantity being conserved over time, and I'm not sure what plays the role of time when you'…

In physics, the conserved quantity isn't always time. Invariance over time translation is specifically conservation of energy. Invariance over spatial translation is conservation of momentum, invariance over spatial rotation is conservation of conservation of angular momentum, invariance of electromagnetic field is conservation of current, and invariance of wave function phase is conservation of charge.

I think the analogue in machine learning is conservation over changes in the training data. After all, the point of machine learning is to find general models that describe the training data given, and minimize the loss function. Assuming that a useful model can be trained, the whole point is that it generalizes to new, unseen instances with minimal losses, i.e. the model remains invariant under shifts in the instances seen.

The more interesting part to me is what this says about philosophy of physics. Noether's Theorem can be restated as "The laws of physics are invariant under X transformation", where X is the gauge symmetry associated with the conservation law. But maybe this is simply a consequence of how we do physics. After all, the point of science is to produce generalized laws from empirical observations. It's trivially easy to find a real-world situation where conservation of energy does not hold (any system with friction, which is basically all of them), but the math gets very messy if you try to actually model the real data, so we rely on approximations that are close enough most of the time. And if many people take empirical measurements at many different points in space, and time, and orientations, you get generalized laws that hold regardless of where/when/who takes the measurement.

Machine learning could be viewed as doing science on empirically measurable social quantities. It won't always be accurate, as individual machine-learning fails show. But it's accurate enough that it can provide useful models for civilization-scale quantities.

Re: Where is Noether's principle in machine learning?

#16

This is one of those links where just seeing the title sets you off, thinking about the implications. I'm going to have to spend more time digesting the article, but one thing that jumps out at me, and maybe it's answered in the article and I don't understand it, is the role of time. Generally in physics, you're talking about a quantity being conserved over time, and I'm not sure what plays the role of time when you'…

A convolutional neural network ought to have translational symmetry, which should lead to a generalized version of momentum. If I understood the article correctly the conserved quantity would be , where dx is the finite difference gradient of x.

This gives a vector with dimensions equal to however many directions you can translate a layer in and which is conserved over all (convolutional) layers.

Re: Where is Noether's principle in machine learning?

#17
People have mentioned the discrete - continuous tradeoff. One way to bridge that gap would be to use https://arxiv.org/abs/1806.07366 - they draw an equivalence between vanilla (FC layer) neural nets of constant width with differential equations, and then use a differential equation solver to "train" a "neural net" (from what I remember - it's been years since that paper...).

Another approach might be to take an information theoretic view with the infinite-width finite-entropy nets.

Re: Where is Noether's principle in machine learning?

#18
post #9

As a complete amateur I was wondering if it could be possible to use that property of light ("to always choose the most optimal route") to solve the traveling salesman problem (and the whole class of those problems as a consequence). Maybe not with an algorithmic approach, but rather some smart implementation of the machine itself.

Google up 'soap film steiner tree' for a fun, well-known variant of this.

Re: Where is Noether's principle in machine learning?

#20
post #3

Earlier quoted context omitted.

Yeah, I've been thinking about similar concepts in a different context. Fascinating. Regarding the role of time, the idea of a purely conserved quantity is that it is conserved under the conditions of the system (that's why the article frequently references Newton's First Law), so they're generally held "for all time that these symmetries exist in the system". Specifically on time: the invariant for systems that exhi…

Here's my ELI5 attempt of the time/energy relation: imagine a spring at rest (not moving) strike the spring, it's now oscillating the system now contains energy like a battery what is energy? it's stored work potential the battery is storing the energy, which can then be taken out at some future time the spring is transporting the energy through time in fact how do we measure time? with clocks. What's a clock? It's a…

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