black hole ringdown

Two tiny diamonds float in a vacuum, separated by a distance that light cannot cross during the experiment. Inside each, like a frozen spark, resides an entangled spin — a quantum state linking them into a single whole. Now the diamonds begin to move, but not just any motion: each one seems to split, existing in two places at once.

When two heavy balls merge into one, ripples spread across the water's surface for a long time. A black hole behaves similarly: after a merger, it 'rings' for a while, emitting special gravitational oscillations — quasinormal modes. Usually, this ring fades quickly, like an echo dying out in an empty hall.

A stone falls into still water — ripples spread across the surface. A black hole behaves similarly when something falls into it or when it merges with another black hole. The hole begins to oscillate, and these oscillations propagate through space as gravitational waves.

A massive aluminum cylinder weighing a ton hangs in a vacuum. A gravitational wave, a ripple in spacetime, passes through it, and the bar begins to tremble almost imperceptibly. That trembling can be heard as sound: gravitational waves turn into a phonon — a quantum of sound vibrations.

The spiral of water draining into a sink spins faster and faster toward the center. In an ordinary black hole, that funnel ends in an infinitely sharp point — a singularity where the laws of physics break down. But this new work considers a different picture: the funnel doesn't taper to a needle but ends in a smooth, swelling bubble.

When two black holes merge far away, we receive a tremor of space — gravitational waves. Usually, they are described by Einstein's equations, but what if gravity works differently at the tiniest distances? The authors took one such hypothesis — Hořava–Lifshitz gravity.

Picture the early Universe as an unimaginably large bell. Inflation — the era of rapid expansion, dreamed up by Alan Guth, strikes it, sending a wave rippling across the fabric of spacetime.

Gravitational-wave detectors are like sensitive microphones, listening for the whispers of distant cataclysms. But every now and then, a sharp crack bursts in — a brief noise spike known as a glitch.

A black hole merger is not a silent impact. The newborn hole quivers and decays, emitting gravitational waves — ripples in space itself. This signal is called the 'ringdown,' and it resembles the fading chime of a bell: it has a fundamental tone and several overtones.

At the center of an ordinary black hole, according to classical ideas, lurks a singularity — a point of infinite density where the laws of physics break down. But some theories, inspired by the duality idea from string theory, propose replacing the point with a tiny 'smudged' region.

The mystery of dark matter has puzzled physicists for nearly a century. Among the candidates for its role are primordial black holes (PBHs), born in the fiery embrace of the first moment after the Big Bang.

The early universe resembled an overcrowded hall where heavy particles collided and decayed at a deafening pace. Among them could have been scalar leptoquarks — particles that simultaneously latch onto a quark (a building block of matter) and a lepton (such as an electron).

In the first moments after the Big Bang, matter and antimatter were almost perfectly balanced. But something tipped the scales — otherwise everything would have annihilated into radiation, leaving the universe empty. One candidate for the role of "tipper" is the ultraheavy right-handed neutrino.

A tightrope walker spirals over an abyss, each loop drawing closer to the center. Their path is not a smooth glide but a series of sharp jerks and pauses. That is roughly how a tiny black hole behaves when it is pulled toward a supermassive neighbor.

Gravitational waves from a tiny body falling into a black hole work like an X-ray image. Only instead of a bone, they illuminate the curved spacetime itself.

Two heavy spheres of dark emptiness hurtle toward each other and collide dead-on. This is not billiards: it's the collision of two equal black holes. The impact sends a tremor through space itself — gravitational waves. Most of this tremor is a low hum that physicists call bremsstrahlung.

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 stone falls into a well, and a second later, a splash. A star falls into a black hole, and disappears beyond the horizon, leaving only a ripple in space. But what if the bottom of the well is not a dead end but a passage? In the usual picture, matter compresses into a point of infinite density — a singularity.

Two heavy balls orbit on the surface of a pond. Ripples spread from them: these are gravitational waves. As the balls spiral closer, the waves carry away energy, and the ripples become more frequent.

When black holes approach and then fly apart — without merging, just grazing each other's gravitational fields — they become ideal projectiles for testing the laws of gravity. In extreme fields, where time dilation reaches monstrous magnitudes, any crack in the theory would flash dazzlingly bright.

A bell struck by a hammer hums softer and softer. Its ring fades smoothly, like ripples on water after a stone is tossed in. A black hole behaves much the same way after colliding with another hole: it shudders, and those shudders, gravitational waves, fly off into space, gradually weakening.

A wormhole is a hypothetical tunnel that shortens the path between distant corners of the universe, like a soap bubble stretched between two points. To keep the bubble's walls from closing, a special film is needed — matter with negative pressure, akin to dark energy. But this support isn't eternal: remove half the film, and the bubble bursts.

Imagine the hum of a crowded square (that's what the gravitational wave background of the Universe sounds like, as detected by a network of pulsars) neutron stars that emit regular radio pulses with the precision of atomic clocks.

Two black holes whirl faster and faster, draw closer, and merge into one. The space around them trembles — that tremor travels across the universe for billions of years and finally makes detector mirrors sway by a fraction of an atom. Scientists catch this signal and want to know exactly which holes produced it.

A chemical bond is like a stretched spring between atoms. When it's snapped, the molecular fragments fly apart, but they don't freeze: they keep vibrating, like a plucked string. That's exactly the vibration a team of researchers caught when they broke a methyl iodide molecule with an ultraviolet laser.

Right after its birth, the Universe wasn't just expanding: it was inflating at an unimaginable pace. This stage, called inflation, was proposed by Alan Guth. New models compare the process to inflating a balloon with quick, jerky pumps.

When two black holes merge, the newborn hole rings like a bell, emitting gravitational waves. In the past, only the fundamental tone of this ringing was captured. But analysis of the GW250114 merger showed that the signal hides extra faint vibrations — nonlinear overtones.

Two giant black holes spiral together and collide — a ripple of spacetime spreads across the Universe. Detectors of gravitational waves catch this ripple. But the signal may hide more than just mass and distance: if the laws of physics differ ever so slightly in different directions, the wave will be distorted.