domain walls

In a pot of boiling water, steam bubbles appear and disappear — a similar struggle takes place in two-dimensional materials. Here, electrons both create magnetism and try to extinguish it.

In 1929, Edwin Hubble pointed his telescope at distant galaxies and discovered they were receding. Ninety years later, two measurements of this recession rate, from ancient light and from nearby stars, stubbornly disagree. A 9% discrepancy cannot be chalked up to error. It is as if the Universe in its youth and in its maturity runs on different clocks.

The ring was assembled from several different segments. In each segment, particles behave in their own way, like musicians playing different notes. The most interesting part begins at the junctions: here particles often get stuck, like an echo trapped in a narrow corridor. This phenomenon is called the skin effect — particles pile up at the boundary, like a crowd at an exit. But the authors noticed something new.

A pot of extremely thick and hot glue: that's roughly what the early Universe looked like. It wasn't ordinary glue, but a 'gluon soup': particles carrying the strong force (gluons) zipped freely through space. The temperature was so high that even quarks and gluons didn't stick together into protons and neutrons. Over time, the Universe cooled.

Boiling water in a pot is a good place to start. Bubbles of steam rise, pop, and the surface settles down. Something similar might have happened in the first moments of the universe's life with a special field filling space: bubbles of a new phase inflated and collided, like islands of steam in liquid.

In the first moments after the Big Bang, cosmic symmetry breaking divided the hot plasma into regions with different vacuums — the lowest energy states of a field.

Glass lenses and mirrors appear perfectly smooth and still. But beneath the surface, a hidden life teems. Atoms in an amorphous material (a substance without a crystalline lattice) are packed haphazardly, and this disorder creates a complex energy landscape, like a mountainous region with countless hills and valleys.

A honeycomb made not of wax but of atoms is graphene — a flat crystal just one atom thick. Electrons in it are like runners at an intersection: they speed up here, slow down there, but never get stuck at the edge. Physicists call such a sheet "topologically trivial," meaning its edges are perfectly ordinary, with no special properties. Now, let's knock out a single atom from the honeycomb.

After the Big Bang, the Universe went through a series of phase transitions, like water turning into ice, but with unpredictable patterns.

In 1981, Alan Guth proposed a scenario of cosmological inflation — a lightning-fast expansion of space that stretched quantum fluctuations to the scale of entire galaxies. Since then, cosmologists, like archaeologists, have been excavating this event from the structures of the Universe.

In the first moments of its life, the Universe resembled a boiling cauldron. As it cooled, phase transitions occurred — much like steam turning into water, but instead of molecules, the very state of space changed. In this cauldron, bubbles of the new phase were born, akin to bubbles in a pot coming to a boil.

If you squeeze water between two glass plates so that only two layers of molecules fit, it becomes something between a liquid and ice. At room temperature, molecules in such a trap still move but arrange themselves into a semblance of a crystal lattice.

A pebble drops into a pond, and ripples spread across the water. But one wave suddenly doesn't spread out: it clings to an invisible fold on the surface and runs only along it.

On May 14, 2019, LIGO detectors registered a gravitational burst that didn't fit the usual mold. Event GW190521 appeared as a collision of two black holes weighing 85 and 66 solar masses. The resulting hole of 142 solar masses landed right in the "forbidden" range — where stellar collapses leave almost no trace.

A compressed spring can sit for years without moving. It seems frozen forever, but inside the metal, atoms slowly rearrange, and one day the spring clicks, settling into a new, more relaxed position.

A rubber band that gets thicker the harder you pull it. In electricity, this behavior is called negative capacitance: the more charge accumulates on the plates, the lower the voltage. A regular capacitor works the opposite way — voltage rises with charge.

The universe is expanding, and its history features two puzzling episodes that don't fit into a simple picture. The first is a brief period in its youth when everything flew apart faster than expected, as if someone had floored the gas pedal. The second is today's acceleration, as if the same pedal were pressed again, but more gently.

Hot tea in a freezer doesn't freeze all at once. First, tiny ice needles dart around — forming and melting until the temperature drops enough for the ice to set solid. The early universe behaved similarly as it cooled and changed its internal structure.

A superconductor carries current without resistance, like water running through a pipe without friction. The secret lies in electron pairs: two electrons stick together as one, even though they normally repel. In an ordinary superconductor, the spins of the electrons in a pair point in opposite directions: this is the singlet state.

A balloon doesn't deflate all at once: first, dents appear on its surface, which run, merge, and finally the balloon shrivels into a point. Domain walls behave in much the same way — thin partitions that divided space in the first moments after the Big Bang.

Imagine a huge layered cake, where the layers of dough are space and the filling is a special region resembling an invisible wall. This wall is not made of bricks but of energy, and it could be as thick as the entire universe. If such a wall exists, it should stretch the dough layers differently: those lying along it spread apart faster, while those across it spread slower.

The mystery of dark matter, first glimpsed in the stellar whirlpools by Vera Rubin, has been tormenting physics for nearly a century. One of the boldest hypotheses: primordial black holes, born in the scalding broth of the early universe.

First thing that comes to mind when thinking about the birth of the Universe is an explosion. But modern cosmology paints a more refined picture: birth through the neck of a wine glass. This geometry is not a sommelier's fantasy, but a rigorous form of Euclidean wormhole that connects two anti-de Sitter worlds.

The universe is not emptiness, but a vast crystalline sphere, threaded with invisible boundaries — domain walls frozen after phase transitions.

A stone falls into a pond, and ripples spread across the water. They reflect off the shore, overlap, and die out. All this motion unfolds in space. But what if the pond itself changed its depth or density for an instant — not at one point, but everywhere at once? A temporal boundary is exactly such a jump in properties over time, not space.

In a pot of boiling soup, churning currents carry heat to the walls, and the soup cools. In a tokamak, a huge magnetic bottle for plasma, the same thing happens: turbulent eddies carry energy outward, hindering the ignition of a fusion reaction. But sometimes the plasma seems to find a way to calm itself.

A magnet with only one pole (north, without a south) is not a fragment but a particle in its own right. Physicists call it a magnetic monopole (a carrier of a single magnetic charge). Such visitors could have been born in the early universe, when the forces were just separating.

Ordinary magnetic measurements only see the surface of a superconductor, where barriers and viscous flows of magnetic field get in the way. Inside, in the so-called intermediate state, superconducting and normal domains coexist, separated by thin walls. These walls can oscillate, but hearing them directly has been difficult.

An ordinary crystal is like an apartment building: electrons move through shared hallways and staircases, influencing each other through the walls. Now, imagine removing all the walls, leaving just a single line of apartments. How would the residents behave? Hydrogen has nothing to do with it, but the collective behavior of electrons takes center stage.

A struck tuning fork fades: its vibrations leak into the air. But there are systems where the oscillation does not decay, even though there are plenty of free waves around, ready to carry energy away. Physicists call such 'captured' states bound states in the continuum (BIC).

Toss a handful of sand on the floor: there are few large grains, many medium ones, and even more tiny ones. This skew, where small events are common and large ones are rare, is described by a power law. It shows up in city sizes, earthquake magnitudes, and citation counts of scientific papers.

In the crystal HfTe5, electrons behave almost like light: their mass is so small that they obey the laws of relativity. If you place such a crystal in a strong magnetic field, the electrons start to circle in tiny orbits. Their energy then changes not smoothly but in steps, like floors in a building.

In the quantum world, there are rules that seem to be broken. One of them is the conservation law: if in classical physics symmetry guarantees the conservation of charge, then in the quantum description this guarantee can disappear. This phenomenon is called a quantum anomaly.

A spring compressed to the limit breaks. Likewise, classical gravity theory leads to a singularity — a point where all laws break down. Quantum mechanics turns this end into an elastic bounce.

In a metal crystal, atoms line up in neat rows like bricks in a wall. Knock out a single brick, and you're left with a void — what scientists call a vacancy. Under irradiation, these voids multiply and start merging into large holes, sapping the metal's strength. It's like holes in a brick wall joining up into a gaping breach.

A stack of identical pancakes on a plate is just a stack. But if you arrange them with a certain order, something new suddenly appears: for example, a pattern that was not visible in each pancake individually. Physicists have performed a similar trick with thin layers of materials.

Two particles cling to each other like climbers on the same rope and fly toward a wall. When they hit, will they bounce off together, or will the rope snap? What does it depend on? Physicists considered the simplest case: everything happens on a single line, the particles attract only when they occupy the same point, and the wall is perfectly rigid.

Neutron stars are the compressed remnants of massive stars: their matter is squeezed so tightly that a thimble-sized amount would weigh a colossal amount. If dark matter, the mysterious invisible substance thought to hold galaxies together with its gravity, accumulates inside such an object, under certain conditions this accumulation becomes fatal.

In the familiar world, we have three spatial dimensions. However, theoretical physics allows for additional, hidden directions — compactified, that is, curled up to microscopic sizes.