Quadratic Gravity Theory Reshapes Quantum View of Big Bang (phys.org) 41
Researchers at the University of Waterloo say a new "quadratic quantum gravity" framework could explain the universe's rapid early expansion without adding extra ingredients to Einstein's theory by hand. The idea is especially notable because it makes testable predictions, including a minimum level of primordial gravitational waves that future experiments may be able to detect. "Even though this model deals with incredibly high energies, it leads to clear predictions that today's experiments can actually look for," said Dr. Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo and Perimeter Institute (PI). "That direct link between quantum gravity and real data is rare and exciting." Phys.org reports: The research team found that the Big Bang's rapid early expansion can emerge naturally from this simple, consistent theory of quantum gravity, without adding any extra ingredients. This early burst of expansion, often called inflation, is a central idea in modern cosmology because it explains why the universe looks the way it does today.
Their model also predicts a minimum amount of primordial gravitational waves, which are tiny ripples in spacetime geometry created in the first moments after the Big Bang. These signals may be detectable in upcoming experiments, offering a rare chance to test ideas about the universe's quantum origins.
[...] The team plans to refine their predictions for upcoming experiments to explore how their framework connects to particle physics and other puzzles about the early universe. Their long-term goal is to strengthen the bridge between quantum gravity and observational cosmology. The research has been published in the journal Physical Review Letters.
Their model also predicts a minimum amount of primordial gravitational waves, which are tiny ripples in spacetime geometry created in the first moments after the Big Bang. These signals may be detectable in upcoming experiments, offering a rare chance to test ideas about the universe's quantum origins.
[...] The team plans to refine their predictions for upcoming experiments to explore how their framework connects to particle physics and other puzzles about the early universe. Their long-term goal is to strengthen the bridge between quantum gravity and observational cosmology. The research has been published in the journal Physical Review Letters.
Doing the editor's job. (Score:5, Informative)
https://en.wikipedia.org/wiki/Quadratic_gravity
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Sure, here you go:
First, there was light.
???
Profit!
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Lies !
Isaiah 14:12
“How you are fallen from heaven, O Day Star, son of Dawn!"
9.81m/s^2 is obviously implied.
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What about underwear?
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You shall make for them linen undergarments to cover their naked flesh. They shall reach from the hips to the thighs
Okay, I'm not doing this from memory: https://www.openbible.info/topics/underwear
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And now you know why the Mormons have their magic underwear.
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Just not correctly...
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The BIBLE answers ALL questions.
So does a magic 8-ball.
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First, there was light.
Nope.
First, there was nothing.
Then God created light.
And there was still nothing. But at least you could see it.
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This is truly the origin of the phrase "always look on the bright side of life"
(Ti dum. Ti dum, didum didum...)
Re:Doing the editor's job. (Score:5, Informative)
Relativity = gravity is represented by the curvature of spacetime. Curvature is linear, R. The formula treats curvature linearly. As things get closer and curvature spikes, the math just scales at a 1:1 rate
Quadratic gravity = Squares the curvature. Doesn't really change things much when everything is far apart, but heavily changes things when everything is close together.
Pros: prevents infinities and other problems when trying to reconcile quantum theory with relativity ("makes the theory renormalizable"). E.g. you don't want to calculate "if I add up the probabilities of all of these possible routes to some specific event, what are the odds that it happens?" -> "Infinity percent odds". That's... a problem. Renormalization is a trick for electromagnetism that prevents this by letting the infinities cancel out. But it doesn't work with linear curvature - gravitons carry energy, which creates gravity, which carries more energy... it explodes, and renormalization attempts just create new infinities. But it does work with quadratic curvature - it weakens high-energy interactions and allows for convergence.
Cons: Creates "ghosts" (particles with negative energies or negative probabilities, which create their own problems). There's various proposed solutions, but none that's really a "eureka!" moment. Generally along the lines of "they exist but are purely virtual and don't interact", "they exist but they're so massive that they decay before they can interact with the universe", "they don't exist, we're just using the math out of bounds and need a different representation of the same", "If we don't stop at R^2 but also add in R^3, R^4, ... on to infinity, then they go away". Etc.
The theory isn't new, BTW. The idea is from 1918 (just a few years after Einstein's theory of General Relativity was published), and the work that led to the "Pros" above is from 1977.
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ED: "But it doesn't work for gravity with linear curvature"
Get Off My Lawn (Score:5, Funny)
Don't you young whipper-snappers go gettin' yer new-fangled quadratic quantum gravity up in my 11-dimensional string theory!
Simple? (Score:2)
I don't think there will ever be a simple fundamental physics again. Unless reality is 3D FEM simulation, then the fundamental equations might be simple (and almost useless).
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For ALL we actually know, Einstein could still be waiting to be proven wrong in many ways.
Einstein died in 1955, so I think we do know for a fact that he's not waiting for anything anymore. But I get what you mean. To wit:
Perhaps the simplest answer is to not assume any human is infallible. No matter how smart. Will we be shocked to find Einstein was perhaps wrong at some point, or will we simply understand and accept he was human.
I for one won't be shocked to find out Einstein is (well, was) wrong. He was many times during his career. So have many other luminaries in science.
Re:Simple? (Score:4, Insightful)
Perhaps the simplest answer is to not assume any human is infallible.
No one seriously working in Cosmology does that. Indeed, there are a lot of theories out there trying to either displace or at least amend Einstein's General Relativity, like MoND or TeVeS. The problem: No one until now has come up with a good idea how to do it, and all the proposed alternatives don't work very well either, have to assume even more unknowns, or are outright wrong in places where GR has been shown to work. Until then, we continue to use GR, because we know, where it works fine, and we know, where it fails.
It's easy to sit in an armchair and wandwave some theories in existence which superseed General Relativity. It's really hard to actually write them down.
Einstein is wrong! (Score:2)
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"....we sure do spend a LOT of time and effort trying to ensure every square theory fits into the perfectly accepted Einstein circle of truth."
We spend a lot of time and effort ensure that every new theory fits with observations.
The fact that our observations align very well with the predictions of General Relativity is another matter entirely.
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The universe is under no obligation to make sense to you. -- Neil deGrasse Tyson
Re: Simple? (Score:2)
I suspect modern cosmological physics is pushing the intellectual limits of the human mind. All the great minds working on it and after all this time still no working theory of what actually happened after the start never mind what caused the big bang in the first place. Perhaps we ll have to wait for AI to advance the field much further.
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I suspect modern cosmological physics is pushing the intellectual limits of the human mind.
IMHO (and not just mine, see below) quantum mechanics hit that wall a century ago.
I think I can safely say that nobody understands quantum mechanics. -- Richard Feynman
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It depends on your time horizon. The predictions aren't *currently* testable. Testing them depends on building new tools.
I sort of don't like it, because I don't really accept continuity, but I've no evidence that my feeling is correct. (I expect things to break down before one gets to 10^-33 cm. But that's because of something Wheeler speculated about in the 1980's.)
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Got some questions (Score:1)
Re:Got some questions (Score:5, Interesting)
Wouldn't you have to be on the very edge of the universe to feel ancient gravitational waves? It's not like they bounce like sound waves.
There is no edge, every point is at the precise center including your two eyes. Because light, gravity waves, and causality travel at a single fixed speed, the further something is the farther back in time it is until you reach a point where you cannot see beyond because it is too far back in time and approaches the Big Bang. Gravity waves from the Big Bang will be rippling through all points always just as you can look in any direction and see the microwave background which is the Big Bang but stretched out to the point it’s far cooler and of longer wavelengths.
And don't they dissipate the further they get from the source, making them undetectable?
Gravity waves are fundamentally undetectable, even in principle. If you want a nearly exact example you are probably familiar with think of two floating bits on a still lake. Perception only occurs along the surface of the water, they cannot see or measure or perceive up and down. When a ripple passes the two bits move toward and away from each other as the surface stretches and shrinks to accommodate the wave and that is the distortion that is measured not the wave itself. It boils down to the second derivative of the mass quadrupole moment tensor and it falls off linearly with distance so is not like other directly measured waves that fall off exponentially.
And how does this explain the ridiculous notion that matter traveled faster than the speed of light shortly after the big bang?
The universe is the same everywhere at the largest scales including being at the exact temperature despite not being casually connected if you look at how causality works on our scales, times, and energy levels. The most reasonable thing is that the universe was once all touching in close contact, even points 90 billion light years away from each other. The universe is also expanding the same everywhere on the largest scales so if you rewind time everything goes back to one point even if there isn’t a “center”. So the crazy thing is to look at all the evidence for it (many other examples of measurement also confirm this is how it looks) and say it’s all wrong because it does not meet personal expectations. That’s not how science works.
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Gravity waves are undetectable, even in theiry? So, we haven't been detecting gravity waves for what, 11 years? https://en.wikipedia.org/wiki/... [wikipedia.org]
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IIUC there are two different kinds of things that are called "gravity waves" in quantum physics by those who aren't experts in the field. One of those is undetectable, and the other is what we've been detecting. (I'm no expert, so I can't clarify that.) There's also something called "gravity waves" in fluid dynamics, and that's definitely detectable.
Phys.org (Score:2)
Got an alternate link that doesn't divert me to ads for cheap watches and flea-bag condo units?
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Here you go. [aps.org]
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huh. phys.org is legit afaik. and testing the TFA link in Brave even with its ad blocker disabled didn't send me anywhere. just got an ad for "the Pitt" on Max+.
maybe a bad ad got through, but might be time to run a Malwarebytes scan just in case.. (also generally I recommend ghostery extension fwiw).