How can Einstein's theory of gravity and quantum mechanics be reconciled? It's a challenge that could lead to new understanding of phenomena like black holes and the origins of the universe. Researchers from Chalmers University of Technology in Sweden and MIT in the United States have published a new article in Nature Communications that reveals discoveries that shed fresh insight on critical issues in understanding quantum gravity.
The search
for a "unified theory" that can describe all of nature's laws within
a single framework—connecting Einstein's general theory of relativity, which
describes the universe on a large scale, and quantum mechanics, which describes
our world at the atomic level—is a major challenge in modern theoretical
physics. A "quantum gravity" theory would encompass both macroscopic
and microscopic descriptions of nature.
"We attempt to comprehend natural rules, which are expressed in the language of mathematics. When we seek answers to physics questions, we are frequently led to new mathematical discoveries as well. This connection is particularly evident in the hunt for quantum gravity, where conducting tests is extremely challenging "Professor Daniel Persson of Chalmers University of Technology's Department of Mathematical Sciences explains.
Black
holes are an example of a phenomenon that demands this type of cohesive
description. When a sufficiently massive star expands and falls under its own
gravitational attraction, all of its mass is condensed in an exceedingly
compact volume, a black hole forms. The quantum mechanical description of black
holes is still in its early stages, but it contains some impressive advanced
mathematics.
A simplified model for quantum gravity
"The task is to explain how gravity emerges as a 'new' phenomena. We want to describe how gravity emerges from quantum mechanical systems at the microscopic level, just as everyday phenomena like liquid flow emerge from the chaotic movements of individual droplets "Robert Berman, a professor at Chalmers University of Technology's Department of Mathematical Sciences, agrees.
Daniel
Persson and Robert Berman, along with Tristan Collins of MIT in the United
States, demonstrated how gravity emerges from a special quantum mechanical
system in a simplified model for quantum gravity called the holographic principle,
which was recently published in the journal Nature Communications.
"We
were able to create an explanation for how gravity emerges by the holographic
principle in a more accurate way than has previously been done, using
approaches from the mathematics that I have investigated," Robert Berman
explains.
Ripples of dark energy
The new
article may possibly shed light on the enigmatic dark energy. Gravity is
described as a geometric phenomenon in Einstein's general theory of relativity.
Heavy items can bend the geometric shape of the cosmos in the same way that a
newly made bed bends beneath a person's weight. But, according to Einstein's
theory, even empty space—the universe's "vacuum state"—has a complex
geometric form. You would detect quantum mechanical fluctuations or ripples, sometimes
known as dark energy, if you could zoom in and look at this vacuum on a
microscopic level. From a broader viewpoint, it is this unexplained source of
energy that is responsible for the universe's accelerating expansion.
This new
research could lead to fresh insights into how and why these minuscule quantum
mechanical ripples form, as well as the relationship between Einstein's theory
of gravity and quantum mechanics, which has long been a mystery to scientists.
"These findings suggest that additional parts of the holographic principle, such as the microscopic description of black holes, might be tested. We also intend to leverage these new links to break new ground in mathematics in the future "According to Daniel Persson.
References:
- Robert J. Berman et al, Emergent Sasaki-Einstein geometry and AdS/CFT, Nature Communications (2022). DOI: 10.1038/s41467-021-27951-9
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