New research suggests that extreme objects known as “kugelblitzes” – black holes made entirely of light – are impossible in our universe, Einstein’s theory of general relativity. This discovery places significant constraints on cosmological models and shows how quantum mechanics and general relativity can be reconciled with solving complex scientific questions.
Black holes — massive objects with such strong gravity that not even light can escape their grip — are among the most interesting and bizarre objects in the universe. They are typically formed by the collapse of massive stars at the end of their life cycle, when the pressure from thermonuclear reactions in their cores can no longer counteract the force gravitation.
However, there are more exotic hypotheses regarding the formation of black holes. One such theory involves the creation of a “kugelblitz”, German for “ball lightning”. (The plural is “kugelblitze.”)
“The Kugelblitz is a hypothetical black hole that, instead of being formed by the collapse of ‘ordinary matter’ (the main components of which are protons, neutrons, and electrons), is formed from the concentration of huge amounts of electromagnetic radiation, such as light,” the study says. co-author José Polo-Gómezphysicist at the University of Waterloo and the Perimeter Institute for Theoretical Physics in Canada, told Live Science in an email.
“Even though light has no mass, it carries energy,” Polo-Gómez said, adding that in Einstein’s general theory of relativity, energy is responsible for creating the curvatures in spacetime that lead to gravitational attractions. “That being said, it is in principle possible for light to form black holes – if we focus enough of it into a small enough volume,” he said.
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These principles apply in the classical general theory of relativity, which does not take quantum phenomena into account. To investigate the potential impact of quantum effects on kugelblitz formation, Polo-Gómez and his colleagues investigated the influence of the Schwinger effect.
“When there is incredibly intense electromagnetic energy – for example due to a huge concentration of light – some of this energy is transformed into matter in the form of electron-positron pairs,” lead author of the study Álvaro Álvarez-Domínguez from the Institute of Particle and Cosmic Physics (IPARCOS) at the Universidad Complutense de Madrid, told Live Science in an email. “This is a quantum effect called the Schwinger effect. It is also known as vacuum polarization.”
In their studieswhich has been accepted for publication in the journal Physical inspection letters but not yet published, the team calculated the rate at which electron-positron pairs produced in an electromagnetic field would deplete their energy. If this rate exceeds the replenishment rate of electromagnetic field energy in a given area, a kugelblitz cannot form.
The team found that even under the most extreme circumstances, pure light can never reach the required energy threshold to form a black hole.
“We demonstrate that kugel blitzes cannot be created by concentrating light, either artificially in the laboratory or in naturally occurring astrophysical scenarios,” study co-author Luis J. Garay, also from IPARCOS, told Live Science. “For example, even though we used the most intense one lasers on Earth we would still be more than 50 orders of magnitude away from the intensity needed to produce a kugelblitz.”
This finding has profound theoretical implications, significantly constraining previously considered astrophysical and cosmological models that postulate the existence of kugelblitzes. It also dashes any hopes of experimentally studying black holes in laboratory conditions by creating them through electromagnetic radiation.
Nevertheless, the positive result of the study shows that quantum effects can be effectively integrated into problems involving gravity, thus providing clear answers to current scientific questions.
“From a theoretical point of view, this work shows how quantum effects can play an important role in understanding the formation mechanisms and appearance of astrophysical objects,” said Polo-Gómez.
Inspired by their findings, the scientists plan to continue investigating the influence of quantum effects on various gravitational phenomena of practical and fundamental importance.
“Several of us are very interested in continuing to study the gravitational properties of quantum matter, particularly in scenarios where this quantum matter violates traditional energy conditions,” he said. Eduardo Martin-Martinez, also University of Waterloo and Perimeter Institute. “In principle, this type of quantum matter can give rise to exotic spacetimes, resulting in effects such as repulsive gravity or the production of exotic solutions. like Alcubierre’s warp drive or traversable wormholes.”