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There is a fundamental problem in physics.
A unique number, called the cosmological constant, connects the microscopic world of quantum mechanics and the macroscopic world of Einstein's theory of general relativity. But no theory can agree on its value.
In fact, there is such a large gap between the observed value of this constant and what the theory predicts is widely regarded as the worst prediction in the history of physics. Solving differences could be the most important goal of theoretical physics in this century.
Lucas Lombriser, assistant professor of theoretical physics at the University of Geneva in Switzerland, has introduced a new method of evaluating Albert Einstein's gravity equations in order to find a value for the corresponding cosmological constant. closely to the observed value. He published his method online in the October 10 edition of the journal. Letters of Physics B.
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How Einstein's biggest mistake has become black energy
The history of the cosmological constant began more than a century ago, when Einstein presented a set of equations, now known as field equations. Einstein, who became the setting of his work. theory of general relativity. Equations explain how matter and energy deform the fabric of space and time to create the force of gravity. At the time, Einstein and astronomers agreed that the size of the universe was fixed and that the overall space between galaxies did not change. However, when Einstein applied general relativity to the universe as a whole, his theory predicted an unstable universe that would expand or contract. To force the universe to remain static, Einstein relied on the cosmological constant.
Nearly ten years later, another physicist, Edwin Hubble, discovered that our universe is not static, but expanding. The light of distant galaxies showed that they were moving away from each other. This revelation convinced Einstein to abandon the cosmological constant of his field equations because it was no longer necessary to explain an expanding universe. According to physics, Einstein later admitted that his introduction of the cosmological constant was maybe his biggest mistake.
In 1998, distant supernova observations showed that the universe was not just expanding, but accelerating. The galaxies moved away from each other as if an unknown force was defeating gravity and discarding these galaxies. Physicists have named this enigmatic phenomenon black energyas his true nature remains a mystery.
Physicists reintroduced once again the cosmological constant in the Einstein equations to account for black energy. In the present standard model of cosmology, known as CDM (Lambda CDM), the cosmological constant is interchangeable with dark energy. Astronomers have even estimated its value from observations of distant supernovas and fluctuations of the cosmic microwave background. Although the value is absurdly small (in the order of 10 ^ -52 per square meter), at the scale of the universe, it is significant enough to explain the accelerated expansion of l & # 39; space.
"The cosmological constant [or dark energy] is currently about 70% of the energy content of our universe, which we can deduce from the accelerated expansion observed that our universe is undergoing. Yet this constant is not understood, "said Lombriser. Attempts to explain it have failed, and there seems to be something fundamental missing in our understanding of the cosmos. Solving this problem is one of the major research areas of modern physics. It is generally expected that the resolution of the problem can lead to a more fundamental understanding of physics. "
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The worst theoretical prediction of the history of physics
The cosmological constant is thought to represent what physicists call "vacuum energy". Quantum field theory states that even in a completely empty space gap, virtual particles appear and disappear and create energy – a seemingly absurd but experimentally observed idea. The problem arises when physicists try to calculate their contribution to the cosmological constant. Their result differs from the observations by a bewildering factor of 10 ^ 121 (ie 10 followed by 120 zeros), the biggest gap between theory and experience in all of physics.
Such disparity has led some physicists to doubt Einstein's original gravity equations; some even suggested other gravity models. However, the laser interferometer gravitational wave observatory (from other sources) showed that the gravitational wave was one more proof.LIGO) have only strengthened general relativity and rejected many of these alternative theories. That's why, instead of rethinking gravity, Darken has taken a different approach to solving this cosmic puzzle.
"The mechanism I'm proposing does not alter Einstein's field equations," said Lombriser. Instead, "it adds an extra equation over the Einstein field equations".
the gravitational constant, which was first used in The laws of gravity of Isaac Newton and now an essential part of Einstein's field equations, describes the magnitude of the gravitational force between objects. It is considered one of the fundamental constants of physics, unchanged from the beginning of the universe. Darken has made the dramatic assumption that this constant can change.
In the modification of the general relativity proposed by Lombriser, the gravitational constant remains the same in our observable universe but can vary beyond. He suggests a multiverse scenario where there might be invisible universe patches for us that have different values for the fundamental constants.
This variation in gravity gave Lombriser an additional equation connecting the cosmological constant to the average sum of matter in space-time. After taking into account the estimated mass of all galaxies, stars and black matter in the universe, he could solve this new equation to obtain a new value for the cosmological constant – a relationship that corresponds to observations.
Using a new parameter, ΩΛ (omega lambda), which expresses the fraction of the universe made up of dark matter, he discovered that the universe is composed of about 74% energy. black. This number closely matches the value of 68.5% estimated from observations – a considerable improvement over the huge disparity found by quantum field theory.
Although the Lombrize framework can solve the problem of the cosmological constant, there is currently no way to test it. But in the future, if the experiments of other theories validate his equations, this could mean a major jump in our understanding of dark energy and constitute a tool for solving other cosmic mysteries .
Originally published on Science live.
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