Ripples in space-time leads to missing components of the Universe

University of Chicago The scientist explains how LIGO Gravitational waves Fried, may yield information.

Our theory of the universe is a bit off-putting. Almost everything fits, but there is a fly in the cosmic ointment, a particle of sand in the infinite sandwich. Some scientists believe that the culprit may be gravity – and the micro-wave in the space-time fabric can help us find the missing piece.

A new paper co-written by a scientist at the University of Chicago explains how this can work. Published in Physical Review D on 21 December, the method relies on finding waves that have bent their way to Earth by traveling through supermassive black holes or large galaxies.

The trouble is that something is not only expanding the universe, but also expanding faster and faster over time – and no one knows what it is. (The discovery of the exact rate is an ongoing debate in cosmology).

Scientists have proposed all kinds of theories for what may be the missing piece. “Many of these rely on changing the way we work on a large scale,” said the paper’s co-author Jose Maria Eziagua, NASA Einstein Postdoctoral Fellow at the Kavli Institute for Cosmological Physics in Ucqogo. “Gravitational waves are the right messengers to see these possible modifications of gravity, if they exist.”

“Gravitational waves are the right messengers to see these possible modifications of gravity, if they exist.”

Astrophysicist Jose Maria Eziagaga

Gravitational waves are waved in the space-time fabric; From 2015 onwards, humanity can pick up these waves using LIGO observatories. Whenever two massive massive objects collide elsewhere in the universe, they create a wave that travels into space, carrying the signature of whatever it created – perhaps two black holes or two neutron stars colliding. .

Merging Black Hole Gravitational Waves

A supercomputer simulation of merging black holes sending out gravitational waves. Scientists believe that there may be a way to use these waves to find missing fragments in our understanding of the universe. Credit: Illustration by Chris Heinz / NASA

In the paper, Ezekiaga and co-author Miguel Zumalacargui argue that if such waves hit a superemusive Black hole Or a cluster of galaxies on the way to Earth, the signature of the wave will change. If there was a difference in gravity compared to Einstein’s theory, the evidence would be embedded in that signature.

For example, one theory for the missing piece of the universe is the existence of an extra particle. Such a particle would produce a kind of background or “medium” around large objects, among other effects. If a traveling gravitational wave hits a supermassive black hole, it will produce waves that merge with the gravitational wave itself. Depending on how it is encountered, the gravitational wave signature may show an “echo”, or scrambled.

“This is a new way to investigate scenarios that could not be tested before,” Ezakiyaga said.

Waves blending animation

A combination of waves creates a blending and a new signature. Credit: Ezakiyaga and Zumalacargui

His paper gives the conditions for finding such effects in future data. The next LIGO run is scheduled to begin in 2022, making detectors even more sensitive to upgrade.

“In our last observation with LIGO, we were reading a new gravitational wave every six days, which is amazing. Across the entire universe, we think they are actually happening once every five minutes, ”Ezekiaga said. “In the next upgrade, we can see many of them – hundreds of incidents per year.”

The increased number, he said, makes it more likely that one or more waves would have traveled through a giant object, and that scientists would be able to analyze them for clues to missing components.

Reference: “Gravitational wave lensing beyond general relativity: Birfring, echoes and shadows, by Jose Maria Eziaga and Miguel Zumalacregui, 21 December 2020,”. Physical Review D.
DOI: 10.1103 / PhysRevD.102.124048

Zumalácarregui, the second author on the paper, is a scientist at the Max Planck Institute for Gravitational Physics in Germany as well as the Berkeley Center for Cosmological Physics at Lawrence Berkeley National Laboratory and University of California, Berkeley.

Funding: NASA, Kavali Foundation.

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