Astrophysicist 'fixes' general relativity by getting rid of a key law: ScienceAlert

Albert Einstein was one smart cookie; There is no doubt about that. But even he knew that his theory of general relativity — the 21st century's answer to Newton's universal theory of gravitation — wasn't perfect.

Like the used car you bought with your first paycheck, it gets the job done on everyday errands. Push it hard up a steep hill Or park it near a quantum mall, and the engine will shudder until it grinds to a halt.

The solution offered by Hamid Reza Fazlullah, a graduate student in astrophysics at the Russian Peoples' Friendship University, is to dive under the hood and find out which components are not as necessary as they seem.

By removing the law of conservation of the mathematical property involving energy and momentum, it is believed that general relativity may overcome a few speed bumps.

Gravity describes the tendency of objects with mass to pack together. Whether it's colliding galaxies, a moon struggling against the inertia of a planet, or an apple falling to Earth from the top of a tree, models of gravity need to explain why masses attract.

However, such a theory would also need to work in a universe where objects with identical charges repel each other, explain why atomic nuclei stick together with incredible force, or why neutrons spontaneously decay to form protons. They also need to operate stably when masses become so dense or space-time so compressed that light itself is no longer able to escape.

Frankly, although good, general relativity is not up to the task.

“The problem of the irrenormalizability of Einstein's gravity is well known. It has led to dozens of attempts to treat it as a low-energy theory,” Fadlallah said. He says.

Renormalization It is a magic trick used by theoretical physicists to hide the frustrating infinities in quantum fields. When the loops of reality seem to forever recede into a confusing fractal, pull some of these techniques out of the bag, and your model will be on solid ground again.

General relativity doesn't make this easy. As such, the undulating space-time fields it describes refuse to entangle with the sandy shores of quantum mechanics, leading to an immiscible physical system that requires two theories of nature where one can make more sense.

Fortunately, Einstein's formulation of general relativity was also based on a number of assumptions. He had good reasons for including it, but ultimately the universe may simply have second thoughts about whether it was justified.

One of the fundamental assumptions of general relativity is that the curvature of space and time corresponds to… Energy and momentum are conserved. In other words, navigating an ocean of space-time from A to B should not affect your energy or speed unless there is a change in forces.

This assumption is all well and good in a flat, empty universe. But the universe is curved and curved, full of galaxies, electrons, and virtual particles that pop in and out of existence.

In 1976English physicist Peter Rastall We arrived at a completely different model of gravity that suggests that matter and the curvature of space and time are related in a non-trivial way, a way that leaves room for maneuver to the standard energy-momentum conservation law.

Modeling a different strand on similar thinking, Fadlallah looked to relativistic thermodynamics — the physics of energy exchange under fairly extreme conditions — to find energy and momentum transformations reminiscent of the equations used in general relativity.

The result is a new way to describe the emergence of gravity from the curvature of space-time, one that gets rid of some basic assumptions while still being useful for things like explaining how the universe expands.

Although good, Einstein's brilliant idea is clearly wrong in some way. There is no point in being overly conservative when fate has everything at hand.

This research was published in European Physical Journal C.