Surface optimization governs the local design of physical networks
TL;DR
Imagine you're building a city's plumbing system. The old idea was to use the least amount of pipe possible to connect every house. This paper argues that nature is smarter than that. Instead of just minimizing the length of the pipes, it also considers their thickness and tries to minimize the total surface area of all the pipes. This different goal explains why we see weird but efficient designs in nature, like three branches sprouting from one point or a tiny branch shooting off at a perfect right angle. It's a more realistic model for how to build things in the physical world, where thickness and maintenance matter just as much as length.
The brain’s connectome and the vascular system are examples of physical networks whose tangible nature influences their structure, layout and, ultimately, their function. The material resources required to build and maintain these networks have inspired decades of research into wiring economy, offering testable predictions about their expected architecture and organization. Here we empirically explore the local branching geometry of a wide range of physical networks, uncovering systematic violations of the long-standing predictions of wiring minimization. This leads to the hypothesis that predicting the true material cost of physical networks requires us to account for their full three-dimensional geometry, resulting in a largely intractable optimization problem. We discover, however, an exact mapping of surface minimization onto high-dimensional Feynman diagrams in string theory, predicting that, with increasing link thickness, a locally tree-like network undergoes a transition into configurations that can no longer be explained by length minimization. Specifically, surface minimization predicts the emergence of trifurcations and branching angles in excellent agreement with the local tree organization of physical networks across a wide range of application domains. Finally, we predict the existence of stable orthogonal sprouts, which are not only prevalent in real networks but also play a key functional role, improving synapse formation in the brain and nutrient access in plants and fungi.
- 1Systematic violations of wiring minimization predictions in physical networks.
- 2Mapping of surface minimization onto high-dimensional Feynman diagrams in string theory.
- 3Prediction of trifurcations and branching angles in physical networks.
- 4Existence of stable orthogonal sprouts improving synapse formation and nutrient access.
Single-minus gluon tree amplitudes are nonzero
Imagine tiny particles called gluons are like spinning tops. Their spin can be in one of two directions, which physicists call 'plus' or 'minus'. For decades, the rulebook seemed to say that you could never have a situation where just one gluon was spinning 'minus' and all the others were spinning 'plus' — that outcome was thought to be zero. This paper found a loophole. Under very specific, purely mathematical conditions that don't exist in our physical reality but are useful for calculations, this interaction can happen. The researchers wrote down the exact recipe for it, fixing a small but important detail in our fundamental rulebook for how the universe works.
Sub-part-per-trillion test of the Standard Model with atomic hydrogen
Scientists made an incredibly precise measurement of light emitted by hydrogen atoms that tested one of physics' most fundamental theories - the Standard Model - to an accuracy of 0.7 parts per trillion. This measurement also resolved a long-standing disagreement about the size of protons by confirming the smaller value found in previous experiments with exotic atoms.
Rock art from at least 67,800 years ago in Sulawesi
Imagine finding a spray-painted handprint on a cave wall. Over thousands of years, a thin, glassy layer of minerals, like limescale in a kettle, grew on top of it. Scientists used a high-tech laser to analyze that mineral layer. By measuring the natural radioactive decay of elements within it, they figured out the layer is about 71,600 years old. Since the handprint is underneath that layer, it must be at least that old, with the most conservative estimate being 67,800 years. This makes it one of the oldest pieces of art ever found and proves that the early humans who lived on this Indonesian island, who had to cross the ocean to get there, were creating symbolic art.
An interstellar energetic and non-aqueous pathway to peptide formation
Imagine you have a box of LEGO bricks, which are like the basic molecules of life called amino acids. To build anything, you need to snap them together. Scientists used to think you needed a puddle of liquid water to make the bricks 'click'. This experiment is like discovering you can snap the LEGOs together inside a freezer. The researchers took the simplest amino acid, froze it onto a dust grain like you'd find in space, and zapped it with energy that mimics cosmic radiation. They found that the amino acids linked up to form a two-brick chain, the first step towards building a protein. This means the essential first chains for life could be forming all over space and delivered to new planets by comets and asteroids.