CosmicDefect's recent activity
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Comment on Proving that SU(2) is compact (and other group theory bits) in ~science
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Proving that SU(2) is compact (and other group theory bits)
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentI have to admit my heart kind of fell in love with kaluza Klein theory back when I first learned about it several years ago and that love has persisted since. I'm always on the lookout for a...I have to admit my heart kind of fell in love with kaluza Klein theory back when I first learned about it several years ago and that love has persisted since. I'm always on the lookout for a reasonable theory that adds more dimensions.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentThat's not a really a compelling case. We can't see radio, but it's just as much a legit form of light as any other wavelength. Our human experience is quite limited and is often a poor source for...Because it's the set of dimensions we experience
That's not a really a compelling case. We can't see radio, but it's just as much a legit form of light as any other wavelength. Our human experience is quite limited and is often a poor source for physics intuition. In contrast, there's a lot of similarities between the degrees of freedom that arise from spatial dimensions and the degrees of freedom in the gauge fields, including the fact curvature in both are defined analogously. You might then naturally ask; are they actually separate things?
We already expanded Euclidean 3-space to include time as a dimension from relativity:
- xi = (x,y,z)
- xμ = (x,y,z,t)
We're then tempted to include the photon Aν gauge field. - Xa = (xμ,Aν)
We can add even more of the fields until we have a unified geometry of all interactions. Now, with all this said, the "project" of doing this in physics in incomplete and success is not guaranteed, but it's a cool idea. All theories of extra-dimensions (including String Theory) start with thoughts like these.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentTo a certain extent, we already see that it does defy expectations by being difficult (or impossible) to quantize in a manner as satisfying as say electromagnetism. But a different point is that...It seems intuitive that the physics of gravity wouldn't conform to expectations derived from our understanding of the other forces?
To a certain extent, we already see that it does defy expectations by being difficult (or impossible) to quantize in a manner as satisfying as say electromagnetism.
But a different point is that you don't have to formulate general relativity as spacetime curvature (the geometrical interpretation). It is perfectly alright to consider a background of special relativity on which the gravitational field acts. From this perspective, gravity is then an additional dynamics field like any other (electromagnetism, electroweak, etc.) living on top of special relativity.
The flipped perspective is to LEAN into the geometrical interpretation. Gravity is the spacetime curvature of our base reality, but so are the other forces! The electromagnetic field tensor F is a curvature tensor for the gauge field we call the electromagnetic field in the same way the Reinmann curvature tensor R is for spacetime. From this perspective, you write all the interactions (gravity, electromagnetism, electroweak, strong, etc.) as geometric curvature. Our reality is then not just spacetime, but spacetime plus all gauge fields. Why give spacetime a preference when mathematically it is a dimension just like any of the others?
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentThank you for the kind words. It occurs to me I should have perhaps motivated the dimensional analysis better so one could follow why the cross section is proportional to the combination of...This was a really fascinating article to read as well, and though I agree with the other posters in being unable to follow the chain of derivation, the results are very clear. It never occurred to me that there could be such a stark difference in the detactability of quantum particles, but a distance of 85 orders of magnitude is nothing to sniff at!
Thank you for the kind words. It occurs to me I should have perhaps motivated the dimensional analysis better so one could follow why the cross section is proportional to the combination of constants in each case, but that'd require either some pretty strong (and likely unsatisfying) hand-waving or a crash course into the Feynman rules for quantum fields.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentThe other answers you got cover the gist, but here's some more reasons why we expect gravity to be quantized. I'm quoting a reddit comment I made some time ago: Why does gravity have to be quantum...The other answers you got cover the gist, but here's some more reasons why we expect gravity to be quantized. I'm quoting a reddit comment I made some time ago:
Why does gravity have to be quantum in the first place? Since nobody can figure it out, maybe gravity is just classical. Maybe Einstein got it right the first time and we're just spinning our wheels. The above seems like a reasonable argument, but I want to elaborate on why we should expect gravity to be quantum in nature.
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There appears to be four fundamental forces in the universe (five if you include the Higgs, though it's not a gauge boson). Of these, all but gravity, are quantum in nature. It would be strange if all of physics except gravity obeyed the rules of quantum mechanics.
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Where quantum mechanics and gravity are both important (most famously black holes), there are calculations that are contradictory, or can only be done approximately. This means that physics must be incomplete. The "Black hole information paradox" says BHs do not preserve information via their decay into Hawking radiation. This is a paradox because quantum mechanics (which predicts Hawking radiation) requires information to be preserved which is a feature called "unitarity." Unitarity is a VERY important feature of quantum theory and we're reluctant to give it up.
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Instead of adding quantum fields to curved spacetime, we ask: "Can classical gravitation fields be made from quantum matter?" The simplest form of this "semi-classical gravity" (i.e. G = <T>) where <T> is the "averaged" quantum matter is also inconsistent and leads to incorrect predictions. This doesn't mean gravity can't be classical, but it does mean both classical gravity and quantum mechanics can't be simultaneously true. Either quantum theory or gravity needs to change.
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Effective quantum gravity actually works well. If you keep to low energy situations, quantum theory and gravity are actually very compatible. In this domain, you can do everything classical gravity does through the language of quantum theory. Calculating the precession of Mercury using quantized gravity is a graduate student level homework problem. Effective quantum gravity also clearly predicts quantum corrections to Newtonian gravity, though today there's no clear way to measure such corrections.
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String theory, despite recent negative buzz and bad PR these days, is a theory of quantum gravity. The problem is well-understood (and well behaved) string theories do not describe our gravity in our universe. We seem to have made math for quantum gravity for somebody else's universe! This is akin to stumbling upon Paris, Kansas instead of Paris, France. It's still Paris however, so maybe there's hope.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect (edited )Link ParentMy pleasure, thank you for reading. The main problem with detecting gravitons as a scattering process is that the cross-section is always proportional to either G_N or (G_N)^(2) which is tiny as...Thank you for sharing your write-up!
My pleasure, thank you for reading.
Have scholars speculated upon any additional processes the graviton participates in with higher cross-sections that might be more readily measured?
The main problem with detecting gravitons as a scattering process is that the cross-section is always proportional to either G_N or (G_N)^(2) which is tiny as an interaction strength. As far as alternative theories, there's a whole zoo of model building we could do out there. Dozens of models. One example which comes to mind is the search for the Randall-Sundrum (RS) graviton which is a massive heavy excitation of the graviton that is predicted by some theories involving extra dimensions. We wouldn't see these gravitons as a scattering process because they are heavy and wouldn't propagate easily (same reason W and Z bosons aren't long range) but there is the possibility we produce them in energetic collisions.
The LHC has excluded RS gravitons of mass up to a few TeV, but they could easily be heavier than that.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect Link ParentWhat gravity has going for it, is that all charges are always positive and attractive.And how insanely weak it is, yet so dominant in the Universe.
What gravity has going for it, is that all charges are always positive and attractive.
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Comment on Can we ever detect the graviton? (No, but why not?) in ~science
CosmicDefect LinkFull disclosure, I did this little writeup but thought folks here might find it interesting. It was fun to use dimensional analysis to understand the order of magnitudes involved in graviton...Full disclosure, I did this little writeup but thought folks here might find it interesting. It was fun to use dimensional analysis to understand the order of magnitudes involved in graviton detection.
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Can we ever detect the graviton? (No, but why not?)
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Comment on Balatro Mobile coming to Google Play, Apple Arcade and App Store on September 26th in ~games
CosmicDefect LinkNon-zero chance I pick this up for mobile. I adore the Steam version and have played many hours on my Steam Deck.Non-zero chance I pick this up for mobile. I adore the Steam version and have played many hours on my Steam Deck.
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Comment on ProtonMail on all the data that Outlook collects about your email in ~tech
CosmicDefect Link ParentOoh. I should try Mint then. Thanks for the recommendation.Until Linux Mint. I think it matters a lot, which Linux you try to switch over to. Ubuntu is decent, but it's too "different" for most Windows users to adjust to. Mint will feel different, too ... but it's manageable.
Ooh. I should try Mint then. Thanks for the recommendation.
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Comment on What are you reading these days? in ~books
CosmicDefect LinkI'm doing a reread of The Lord of the Rings (this time using the audiobook done by Andy Serkis which is excellent). After I finish that, I plan to tackle the Silmarillion again. I've read it once...I'm doing a reread of The Lord of the Rings (this time using the audiobook done by Andy Serkis which is excellent). After I finish that, I plan to tackle the Silmarillion again. I've read it once before, but didn't understand much. This time I feel much more prepared to follow along, afterwhich, I'd like to jump into Unfinished Tales. I'm in a bit of a Tolkien kick atm.
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Comment on In Cold War II, the US risks playing the Soviet role in ~society
CosmicDefect (edited )Link ParentThey're an economic powerhouse to be sure, but from my understanding they're facing some serious real estate and unemployment problems right now. This economic malaise is a real risk for China....The US is destined to be eclipsed economically by China, and anyone who believes otherwise is frankly delusional.
They're an economic powerhouse to be sure, but from my understanding they're facing some serious real estate and unemployment problems right now. This economic malaise is a real risk for China. Demographics are also spoiled against them as the work force ages and the population continues to contract for the first time in decades.
In contrast, US unemployment is near record lows, we've dealt with global inflation far better than most nations on Earth, and our population is steadily predicted to increase over the next century primarily because immigration here is so high. These are some big advantages.
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Comment on Poll: US President Joe Biden’s standing hits new lows amid Israel-Hamas war in ~news
CosmicDefect Link ParentIn my non-expert opinion, the Biden administration is partially responsible for the war not spilling into Lebanon in any truly catastrophic manner. The amount of restraint the US is displaying as...In my non-expert opinion, the Biden administration is partially responsible for the war not spilling into Lebanon in any truly catastrophic manner. The amount of restraint the US is displaying as Iranian proxies attack US soldiers actively goading for escalation is remarkable.
I can't imagine either of the two prior administratives threading the needle in this way. The last for obvious reasons, and the Obama admin because of Obama's antagonistic relationship with Bibi.
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Comment on The Attack on Titan/Shingeki no Kyojin anime has finally finished. What's the verdict? in ~anime
CosmicDefect (edited )Link ParentEdit: "but that's not a debate I want to get into" Oops. Well, I'll leave my comment be. I didn't hate the manga ending but I certainly felt "welmed" by it, so your take is good to hear. I'll have...Edit: "but that's not a debate I want to get into" Oops. Well, I'll leave my comment be.
I didn't hate the manga ending but I certainly felt "welmed" by it, so your take is good to hear. I'll have to check out your link after watching it. My biggest issue however, outside the meme dialogue, was as you alluded to: Eren's seemingly incoherent actions which bothered me quite a bit. As someone who was reading issue to issue as it was coming out, the fan theories at the time mostly ended up way more imaginative, creative and consistent with Eren's actions up until the ending battle.
In contrast, when I watched Breaking Bad as it aired, the fan theories were either proven true (the poisoning) or outdone by the actual show (the wheelchair). That led to a vastly more hype experience where it felt like you either figured out the puzzle the showrunners laid out for you or were completely outsmarted by them. It's a shame because for much of AoT's run, it was that quality of story. I'm talking about stuff like the meaning of Erwin's odd question or "you started this". These and others were such great plot points where the community either figured it out or were rewarded with something even better.
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Comment on OpenAI announces leadership transition in ~tech
CosmicDefect Link ParentCue up some conspiracy theory that OpenAI has created the AGI Omnissiah and it itself requested his firing. It'd make a good sci-fi story.I'm wrong and they either have something much more powerful than I thought OR it's just as dumb as I think but it's getting adopted/used in dangerous ways we're not more aware of
Cue up some conspiracy theory that OpenAI has created the AGI Omnissiah and it itself requested his firing. It'd make a good sci-fi story.
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Comment on <deleted topic> in ~games
CosmicDefect Link ParentI friggin love that DF meme. I laughed every time I see it. DF is pretty relaxing too actually if you don't settle somewhere dangerous.I friggin love that DF meme. I laughed every time I see it. DF is pretty relaxing too actually if you don't settle somewhere dangerous.
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Comment on Unzicker's "Real Physics": on dangers of Youtube physicists in ~science
CosmicDefect Link ParentMeh, as much as I don't like it, it's not really acutely dangerous, but rather very frustrating and annoying. People always like underdogs so the narrative of the terrible academic ivory tower is...Maybe he's super dangerous.
Meh, as much as I don't like it, it's not really acutely dangerous, but rather very frustrating and annoying. People always like underdogs so the narrative of the terrible academic ivory tower is inherently attractive (and there's no shortage of real reasons to have a beef with academia either). The issue I find is that it's far easier to gain an audience if you don't need to actually sell truth. The video in question makes absurd claims about Schwinger's publications that are easy to prove false if you have a physics background. But that's a big barrier to most folks. Working physicists who can counter this stuff are themselves however busy... well... doing physics. There are good physics YouTubers out there: Scishow, PBS Spacetime, MinutePhysics, Sixty Symbols, 3Blue1Brown (more math really) to name a few, so all hope is not lost. These people however focus on making their own interesting content rather than the depressing work of debunking and I don't blame them.
So, as the blog post states right off: I am not a trained mathematician, but a physicist. I am secretly jealous of mathematicians though, and their ways, and have been trying to patch up my skills. What better method to improve than to pick a question that interests me and diving deep as I could and putting the results into writing. Corrections are welcome! This was also cross-posted to /r/math which has some really good discussion too.