AKA Moiré Gravity
Graphene - after many years, I still find it hard to believe that two-dimensional materials aren't talked about more in the news. Isn't the news one big hype machine? If I told you that the discovery of one single material has already been so revolutionary that it requires its own branch of science, a new branch of science, just to understand it, wouldn't you want to know more about that?
Maybe it's because companies can't make money off it yet. No, it's definitely because companies can't make money off it yet (because most news is advertising, which is paid for by the companies who make "newsworthy" things, and we're not talking about the ads, but the content itself, which is a subtle and pervasive form of advertising that some folks might call psychological operations, or just cultural indoctrination).
So I thought graphene was a big deal; I still do. But then this comes out, and now I just give up.
Bilayer graphene inspires two-universe cosmological model
May 2022, phys.org
This is where true excitement comes from: "The pair of scientists stumbled upon this new perspective..." (i.e., accidental discovery)
They realized that experiments on the electrical properties of stacked sheets of graphene produced results that looked like little universes and that the underlying phenomenon might generalize to other areas of physics.Stacked graphene's exceptional electrical properties and possible connection to our reality having a twin comes from the special physics produced by patterns called moiré patterns. Moiré patterns form when two repeating patterns—anything from the hexagons of atoms in graphene sheets to the grids of window screens—overlap and one of the layers is twisted, offset, or stretched.Galitski and Parhizkar realized that the physics in two sheets of graphene could be reinterpreted as the physics of two two-dimensional universes where electrons occasionally hop between universes.But wait (cosmological shenanigans) - Whenever researchers attempt to use observations to approximate the cosmological constant, the value they calculate is much smaller than they would expect based on other parts of the theory. More importantly, the value jumps around dramatically depending on how much detail they include in the approximation instead of homing in on a consistent value. This lingering challenge is known as the cosmological constant problem, or sometimes the "vacuum catastrophe."Galitski and Parhizkar created a mathematical model (which they call moiré gravity) by taking two copies of Einstein's theory of how the universe changes over time and introducing extra terms in the math that let the two copies interact.Playing with their model, they showed that two interacting worlds with large cosmological constants could override the expected behavior from the individual cosmological constants. The interactions produce behaviors governed by a shared effective cosmological constant that is much smaller than the individual constants. The calculation for the effective cosmological constant circumvents the problem researchers have with the value of their approximations jumping around because over time the influences from the two universes in the model cancel each other out.This idea arose spontaneously when they were working on a seemingly unrelated project...
via Joint Quantum Institute: Alireza Parhizkar et al, Strained bilayer graphene, emergent energy scales, and moiré gravity, Physical Review Research (2022). DOI: 10.1103/PhysRevResearch.4.L022027
Also: Alireza Parhizkar, Victor Galitski, Moiré Gravity and Cosmology. arXiv:2204.06574v1 [hep-th], arxiv.org/abs/2204.06574
And then this, completely different group of scientists, reported in the same month:
Ghostly 'mirror world' might be cause of cosmic controversy
May 2022, phys.org
New research suggests an unseen "mirror world" of particles that interacts with our world only via gravity that might be the key to solving a major puzzle in cosmology today—the Hubble constant problem.Just a reminder: The Hubble constant is the rate of expansion of the universe today. Predictions for this rate—from cosmology's standard model—are significantly slower than the rate found by our most precise local measurements. This discrepancy is one that many cosmologists have been trying to solve by changing our current cosmological model."Basically, we point out that a lot of the observations we do in cosmology have an inherent symmetry under rescaling the universe as a whole. This might provide a way to understand why there appears to be a discrepancy between different measurements of the Universe's expansion rate.""In practice, this scaling symmetry could only be realized by including a mirror world in the model—a parallel universe with new particles that are all copies of known particles," said Cyr-Racine. "The mirror world idea first arose in the 1990s but has not previously been recognized as a potential solution to the Hubble constant problem.
via University of New Mexico and University of California Davis: Francis-Yan Cyr-Racine et al, Symmetry of Cosmological Observables, a Mirror World Dark Sector, and the Hubble Constant, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.201301
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