Tag: physics

Gauge CNN

going beyond the Euclidean plane would require them to reimagine one of the basic computational procedures that made neural networks so effective at 2D image recognition in the first place. This procedure, called “convolution,” lets a layer of the neural network perform a mathematical operation on small patches of the input data and then pass the results to the next layer in the network. Gauge CNNs can detect patterns not only in 2D arrays of pixels, but also on spheres and asymmetrically curved objects. “This framework is a fairly definitive answer to this problem of deep learning on curved surfaces”

this has been applied to proteins:

Correia’s system, called MaSIF (short for molecular surface interaction fingerprinting), avoids the inherent complexity of a protein’s 3D shape by ignoring the molecules’ internal structure. Instead, the system scans the protein’s 2D surface for what the researchers call interaction fingerprints: features learned by a neural network that indicate that another protein could bind there. “The idea is that when any 2 molecules come together, what they’re essentially presenting to 1 another is that surface. So that’s all you need,. It’s very, very innovative.”

Physics & Biology

13 tips for engaging with physicists, as told by a biologist this is a great, and unfortunately rare, example of interdisciplinary work:

Understand what ‘I do not understand’ means When physicists do not understand something that you have said about biology, it’s possible that you do not understand that topic either. 2. Seek common ground When a physicist does not understand an aspect of biology, they are not requesting a ‘biology 101’ explanation. In my experience, when physicists ask a biology question, they want to apply the thinking of physics to biology; specifically, they are searching for universal, mathematical explanations. 4. Keep in mind the maths shortfall in biology For most biological phenomena, we don’t have precise equations — unlike in physics. This is not to say that we don’t have maths, but our field needs a lot more detailed quantification. This lack is the Achilles heel of biology, and affects even the concepts we use every day.

there’s also a view from the other side: 12 tips for engaging with biologists, as told by a physicist

Get comfortable being uncomfortable I went from being one of the most knowledgeable people in my research field at the end of my PhD to knowing less than most of the first-year PhD students in my new lab. For me, that meant I was doing something right, but you do have to be OK with taking that hit and spending time building a new skill set Do not blindly accept dogma Challenging prevailing ideas in biology using your perspective can bring about revolutions. I greatly admire colleagues who have upturned decades of accepted dogma using quantitative methods that were not even considered by the biological community.

Quantum Conservation Laws

Maybe energy can be created and destroyed, or maybe the notion doesn’t quite make sense. To reconcile quantum mechanics and general relativity will require a quantum theory of gravity. Physicists disagree vehemently on what such a theory will look like, but most agree on one thing: The notion of spacetime will disappear at the fundamental quantum-gravity level. In that case, conservation laws lose their relevance completely. How can you say a certain quantity does not change with time if there is no time at the fundamental level?

Cosmological Bootstrap

There’s no “time” variable anywhere in the new bootstrapped equation. Yet it predicts cosmological triangles, rectangles and other shapes of all sizes that tell a sensible story of quantum particles arising and evolving at the beginning of time. This suggests that the temporal version of the cosmological origin story may be an illusion. Time can be seen as an “emergent” dimension, a kind of hologram springing from the universe’s spatial correlations, which themselves seem to come from basic symmetries. The approach has the potential to help explain why time began, and why it might end. “The thing that we’re bootstrapping is time itself.”

Proton Radius

Muon-orbited protons are 0.84 femtometers in radius — 4% smaller than those in regular hydrogen. If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons — a fundamental discovery. 100s of papers speculating about the possibility have been written. After Pohl’s muonic hydrogen result, a team of physicists set out to remeasure the proton in regular, “electronic” hydrogen. Finally, the results are in: The proton’s radius is 0.833 femtometers, give or take 0.01, a measurement exactly consistent with Pohl’s value. Both measurements are more precise than earlier attempts, and they suggest that the proton does not change size depending on context; rather, the old measurements using electronic hydrogen were wrong.

Don’t Fear The Simulators

don’t worry if we happen to live in a simulation.

That means it knows these experiments are going to happen. If it cares about the results, it can fake them. Assuming for some reason that it made a mistake in designing the cosmic background radiation (why are we assuming this, again?), it can correct that mistake now, or cause the experimental apparatus to report the wrong data, or do one of a million other things that would prevent us from learning we are in a simulation. The Times’ argument requires that simulators are so powerful that they can create entire universes, so on-top-of-things that they will know the moment we figure out their game – but also so incompetent that they can’t react to a warning published several years in advance in America’s largest newspaper. There’s another argument for the same conclusion: the premises of the simulation argument suggest this isn’t the simulators’ first rodeo. Each simulator civilization must simulate 1000s or millions of universes. Presumably we’re not the first to think of checking the cosmic background radiation. Do you think the simulators just destroy all of them when they reach radio-wave-technology, and never think about fixing the background radiation mismatch or adding in some fail-safe to make sure the experiments return the wrong results?

Against High Energy Physics

high energy physics thinks that bigger colliders will let them find new particles, but this view is probably wrong.

You could build a circular machine 3x the size of the Large Hadron Collider to collide electrons and positrons; you could upgrade the LHC, or even build a next-generation linear accelerator. Probing higher energies offers the hope of new physics — it could be supersymmetry, it could be something else, I don’t know what. But before exploring higher energies, it makes sense to me to build a muon collider, and to clarify the question of the Higgs first. Here we already have a particle that we want to explore. We may even find signs of new physics by studying the Higgs very precisely. For that we don’t need to go to a 100-kilometer-around tunnel. Think about how many days it takes to walk 100 kilometers! And it all has to be extremely functional, every single piece has to work — it’s a miracle if people succeed in making it work.