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Scientist Smith YT
Scientist Smith YT
4:18 AM
What does Quantum Field Theory, String Theory and M-Theory have in common? I'm looking for an in-depth thing they all have in common and I have no clue. Could someone help me out on this one
 
yuvraj singh
yuvraj singh
4:52 AM
@ScientistSmithYT I think quantum field theory and string theory are different things.
On e things sure QFT doesn't know anything about particles. In string theory, the classical model from which we start is the one of string moving freely in some high-dimensional target space.
 
 
2 hours later…
Scientist Smith YT
Scientist Smith YT
7:20 AM
@yuvrajsingh Ok thanks. But I'm kind of looking for a more in depth thing they all have in common. Like the very root of all of them.
 
yuvraj singh
yuvraj singh
I like to post something, which learn from @JohnRennie sir, so I am posting it exact hope it help.
It's a bit like we don't notice quantum effects in everyday life e.g. cricket balls don't diffract. It's only when we look closely that we see quantum effects. So quantum mechanics looks like Newtonian mechanics at large scales.
But some quantum effects, like tunnelling, have no Newtonian equivalent. They are exclusively quantum effects
We get a similar relationship between string theory and QFT. When we study elementary particles we find QFT works well, just like when we study cricket balls Newtonian mechanics works fine.
We get a similar relationship between string theory and QFT. When we study elementary particles we find QFT works well, just like when we study cricket balls Newtonian mechanics works fine.
But we expect that if we were able to look at QFT effects really closely we would start seeing effects due to string theory. In fact we can't do those experiments because they would need higher energy colliders than we can build at the moment.
So everything in QFT is described by string theory, but at high enough energies we would see effects due to string theory that we don't see in QFT.
@ScientistSmithYT
 
weegee
weegee
The immediate axis theorem question should be on physics.SE, right?
128
Q: The "Dzhanibekov effect" - an exercise in mechanics or fiction? Explain mathematically a video from a space station

Alexander ChervovThe question briefly: Can one explain the "Dzhanibekov effect" (see youtube videos from space station or comments below) on the basis of the standard rigid body dynamics using Euler's equations? (Or explain that this is impossible and that would be yet another focus ... ) Here are more details...

classical-mechanics ds.dynamical-systems
Why is it on math.overflow?
Is it because they ask the mathematical reasoning for it?
 
yuvraj singh
yuvraj singh
7:37 AM
@PM2Ring hi. Morning.
 
weegee
weegee
Would it be downvoted if asked on physics.SE because the questions ask the mathematical reasoning behind it?
 
PM 2Ring
PM 2Ring
Hi @yuvrajsingh I hope you're feeling a bit better today.
@weegee I think it would have been ok on Phyics.SE. But there's no point asking it on Physics.SE now, since it has been answered on MathOverflow.
 
weegee
weegee
Why was it okay for mathoverflow in the first place?
Like it's a physics question
 
PM 2Ring
PM 2Ring
8:02 AM
@weegee Well, it is a mathematical physics question. But I don't know the rules of MathOverflow. Note that that question was posted before MathOverflow became part of the Stack Exchange network. See en.wikipedia.org/wiki/MathOverflow
 
weegee
weegee
oh yes
Anyone who knows mathoverflow's rules and knows why it's okay to ask something like that in math.overflow?
 
yuvraj singh
yuvraj singh
@PM2Ring yes.
Have you ever tried paragliding.
 
Secret
Secret
8:40 AM
Cyclic universe: What ensures the cylicity
 
PM 2Ring
PM 2Ring
@yuvrajsingh No. I was interested in hang-gliding when I was younger: I had friends who lived very close to a popular hang-gliding site, so I spent hours watching people hang-gliding. But I never tried it myself. And I'm not fit enough for that kind of thing these days. I ruptured a disc in my back about 20 years ago.
 
yuvraj singh
yuvraj singh
9:12 AM
Oh OK.
 
Slereah
Slereah
@SirCumference what do u need
 
Slereah
Slereah
9:27 AM
Added a captcha on me site's contact form
Hopefully less spam about bitcoins and horny ladies
 
 
3 hours later…
Secret
Secret
12:12 PM
 
Martin Sleziak
Martin Sleziak
12:56 PM
@weegee Since this is being discussed in two rooms, I will mention also here that a question about Dzhanibekov effect (Tennis Racket Theorem) exists also on this site: Why does this object periodically turn itself?
Both questions (the one on Physics and the one on MathOverflow) have link to the other one in comments or answers.
 
yuvraj singh
yuvraj singh
1:43 PM
@Secret amazing game.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
2:10 PM
@yuvrajsingh I like your profile picture... Btw, I <3 Swami V.
@NovaliumCompany rigorous way...
like can you implement Neural Nets using C++?
or question stuff like that.
If you don't have mathematically strong background no one can help you.
Read books on Machine Learning, specially the perceptron part.
@PM2Ring how?
 
ZeroTheHero
ZeroTheHero
@weegee this result has been the topic of multiple questions on PSE.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
Hey, this is terrible, India is doing a lot of secret nuclear and weapons testing. I'm afraid, still no comments from the government...
I think they are developing Newer Versions of KALI.
KALI (electron accelerator)
The KALI (Kilo Ampere Linear Injector) is a linear electron accelerator being developed in India by Defence Research and Development Organisation (DRDO) and Bhabha Atomic Research Centre (BARC). It is a Directed-energy weapon designed to work in such a way that if an enemy missile is launched towards India, it will quickly emit powerful pulses of Relativistic electron beam and destroy the target. Unlike laser beams, it does not bore a hole in the target but thoroughly damages the on-board electronic systems. Scientists say that it can potentially be used as a beam weapon. Bursts of microwaves packed...
There were also shockwaves felt near Pokhran a few days ago, (same spot, where Nuclear Test - 1, smiling Buddha and Nuclear Test, Pokhran - II was performed)
There's some secret spot where they are doing underground testing (rumors)
 
Ryan Unger
Ryan Unger
@Slereah Unruh looks exactly like I expected
 
Slereah
Slereah
@RyanUnger what did you expect?
I mean I would expect him to look like your average old physicist
 
Ryan Unger
Ryan Unger
2:25 PM
Yes
 
Slereah
Slereah
I wouldn't except say, Cedric Villani
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Lifting something that was too heavy, when my back was already injured.
 
Ryan Unger
Ryan Unger
@Slereah villani looks more normal irl
 
Slereah
Slereah
I would expect so
Hard to maintain that level of style
Harsh words on negative numbers
 
yuvraj singh
yuvraj singh
@AbhasKumarSinha he was a legend, and his thoughts and views are eternal.
 
PM 2Ring
PM 2Ring
2:34 PM
@AbhasKumarSinha Secret testing of nuclear devices is very difficult. Many fission & fusion products undergo beta decay, which releases neutrinos / antineutrinos. And they travel through most matter with very few being absorbed. So if a nuclear bomb explodes, all the neutrino detection experiments around the world will pick it up.
 
Ezze
Ezze
@PM2Ring Got any proof of this statement? AFAIK neutrino detection experiments have an absolute horrible detection rate, as in from a flux of $10^11$ neutrinos per square cm per second they only detect a handful per year
 
yuvraj singh
yuvraj singh
@PM2Ring do you remember I ask you a question on time, someone refer me to watch star wars, is there any connection of this movie with answer.
 
PM 2Ring
PM 2Ring
@Ezze I'll have a look. Yes, neutrino detection is hard, because they tend to just go through everything, so even detecting one per billion is considered good. But I know that neutrino flux can be measured from a reactor a couple of hundred kilometres away, even though the neutrinos are traveling through the Earth itself.
@yuvrajsingh They did? There is almost no science in Star Wars.
 
yuvraj singh
yuvraj singh
Yes, he said me to watch star wars.
 
Slereah
Slereah
2:51 PM
I have watched Star Wars
 
PM 2Ring
PM 2Ring
Ok, maybe my previous statement was a little premature. But here's an article about a planned detector which will test the feasibility of watching for rogue nuclear devices. nytimes.com/2018/03/27/science/nuclear-bombs-antineutrinos.html I'll keep looking...
 
yuvraj singh
yuvraj singh
@Slereah yes.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Both of the previous Nuclear Tests were kept the secret, it was the Indian service which informed CIA (pulling socks) about that. Otherwise, they got no chance to know about it. See Pokhran Movie for more info.
@yuvrajsingh Ofc, I like and appreciate these people.
 
Ezze
Ezze
@PM2Ring See, this is the thing I'm skeptical about. If you only detect two to four a day (based on the article), then I am not sure you would see any kind of peak from a nuclear explosion. What would that peak be? One more detection that day? Good luck proving that it is indeed an anomaly
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Also both Nuclear tests were conducted very very deep underground. Both succeeded and even villagers were not aware of that. Current India has about 150 active nuclear missiles. America and Japan threw sanctions after those tests.
 
PM 2Ring
PM 2Ring
2:58 PM
I was thinking about the OPERA experiment, but that used a high energy neutrino beam, not a mere reactor (or bomb). But those neutrinos did travel through 731 km of soil and rock. OTOH, only a handful of neutrinos were detected.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Detecting Neutrinos is not an easy task. It's difficult. specially the ones emitted from Nuclear Missles.
 
Ezze
Ezze
@AbhasKumarSinha Naah, worst case: we all die.
Can't see any problem with that
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring see how CIA was fooled and all the satellites were too! - economictimes.indiatimes.com/news/defence/…
@Ezze well USA has 10x more nuclear weapons because they have multiple enemies unlike the case of India. I don't see any reason for death from it.
@Ezze India should remain stuck to no first use policy in my opinion. It doesn't have multiple enemies.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha The 1st Indian nuclear test, Smiling Buddha, was conducted in 1974, when neutrino detectors were in their infancy. Pokhran was more recent (20 years ago), when more detectors were online. There are now even more detectors, with improved sensitivity. But I admit there's plenty of room for improvement. en.wikipedia.org/wiki/Neutrino_detector
 
Ryan Unger
Ryan Unger
@Slereah polyakov might be here
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:05 PM
@PM2Ring well if that's true, then why not this test was detected? third one
 
Slereah
Slereah
@RyanUnger Star studded affair
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Also the government is clearly hiding things to avoid the mess.
@PM2Ring Are there any other ways to detect these? I mean some other way better than Neutrino Detectors?
 
Slereah
Slereah
@AbhasKumarSinha Radionucleids in the atmosphere
Seismic waves
Big explosions
Nuclear explosions are famously not discreet
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@Slereah India also has ASAT Capabilities, they won't let you other satellites track you. ASAT also fooled the whole world and is the 4th country in the world to do that. (so, ofcourse that would work in case of other countries but not with India)
@Slereah Government can hide those. SAD
@Slereah RTI Act doesn't fall for Military stuff, sad, woof, otherwise anyone could have used RTI Act to ask questions and approach Supreme Court.
 
Slereah
Slereah
Also if all else fails, just look at your hand
If it's disintegrating, there is an atomic explosion nearby
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:13 PM
@Slereah Not true, example North Korea, they have more capabilities compared to US.
@Slereah That works.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Here's a current HNQ on the no-first-use (NFU) policy of nuclear weapons. politics.stackexchange.com/q/47349
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@Slereah Men in Black II (<3 Will Smith)
@PM2Ring This is true, NAZIS had Nuclear Weapons and very less people in the world knew it, and no one knew this untill 2012 When they found secret 80km underground chain of caves, they found emission of radioactive waste there.
 
PM 2Ring
PM 2Ring
Underground tests are no big deal. When I was a kid they were still doing above ground tests. Some of the tests in Australia were among the dirtiest: en.wikipedia.org/wiki/British_nuclear_tests_at_Maralinga
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring have you seen them doing underground?
 
Slereah
Slereah
From what I remember the nazi nuclear program is fairly controversial to historian
and whatever they had wasn't much anyway
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:21 PM
@Slereah Do you need proof? A guy dug his backyard using Nuclear Radiation Detector which showed warning levels under the ground, probably I've seen them in Nat Geo.. Let me find that for you. Due to very high Radiation Levels, government banned further search
@PM2Ring was that successful?
 
Slereah
Slereah
@AbhasKumarSinha I mean that doesn't necessarily means nuclear tests, although I don't know enough about the topic to judge
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@Slereah ah okay... got the point..
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha They may have built a reactor. It may have even worked. That's a far cry from creating a usable weapon.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Oh okay, does Australia has Nuclear Weapons?
@Slereah My bad, not Nat Geo, it's Discovery
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha What do you mean? They certainly succeeded in contaminating a big chunk of land with plutonium & other unpleasant stuff. It was a long distance from the big cities, but all the people alive on the continent at that time would have picked up a few extra radioisotopes.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:28 PM
@PM2Ring ah, okay... That was also undetectable one.
@PM2Ring Do you know More than 25 million Indian population could get wiped out overnight just due to a silly Nuclear Fault (protonium tablets)
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha As far as I know, we don't. The tests at Maralinga were of British devices. I don't know where they got the fissile materials, probably from the USA, but Australian uranium was probably involved.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Australia has a lot of Uranium, they can be used as energy alternatives to coal.
@PM2Ring India doesn't have any. (That's good too)
 
PM 2Ring
PM 2Ring
2 days ago, by PM 2Ring
BTW, Australia has a lot of uranium, but we have no nuclear reactors producing power, for political reasons.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring The link you shared doesn't have any information about India's No First Use Policy, while India has also signed too - en.wikipedia.org/wiki/No_first_use
@PM2Ring true, Is Australia member of NSG?
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha What's a protonium tablet?
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:34 PM
@PM2Ring tablets of protonium or energy capsules.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Yes, it is.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring my bad plutonium tablet.
@PM2Ring not protonium, it's plutonium, hydrogen isotope.
@PM2Ring Australia is a member of NSG so what's the political problem here?
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha You're not making sense. Plutonium is element 94, hydrogen is element 1. Plutonium is not an isotope of hydrogen!
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring ah okay... Not hydrogen isotope.
@PM2Ring plutonium isotope I mean, the more radioactive ones.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Australia supplies uranium to other countries. Neither of our major political parties want nuclear power stations here. We do have a research reactor though, which produces medical & industrial isotopes.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
3:40 PM
@PM2Ring nuclear power stations are good, then where's the problem?
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha I'm quite familiar with plutonium. Eg, physics.stackexchange.com/a/512461/123208
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring oh okay.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha If any Australian politician said he wanted to build a nuclear power station, he'd lose the next election.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring why people don't want that?
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Because they're scared of nuclear accidents, and nuclear waste.
 
Ezze
Ezze
3:45 PM
As they very well should be.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring ..? really? We neither had any nuclear accidents neither nuclear waste problem....
@Ezze yes, agree.
 
PM 2Ring
PM 2Ring
There's been a lot of anti-nuclear propaganda here for the last 40 years or so, starting after Maralinga. Most of the environmentalists are anti-nuclear. And it's likely that the big oil & coal producers are quite happy about that...
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring Environmentalists against nuclear weapons? then people are not well informed or I don't understand the problem. On an average Australian people have 3x more carbon emission than average and nuclear technologies will definitely reduce it to half...
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha What? Ezze is saying that people should be scared of nuclear accidents, and nuclear waste. I'd expect you to disagree with that.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring I agree with that, that's why I'm here asking how to detect secret nuclear tests...
 
Ezze
Ezze
3:52 PM
Not being scared of nuclear accidents sounds kind of cocky NGL
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@Ezze true.
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha They are against all nuclear technology. They certainly don't want weapons, they don't want power reactors, they don't approve of uranium (or thorium) mining. The more radical ones don't want the reactor that makes medical isotopes.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring ah okay... certainly there's some problem when you don't trust nuclear stuff for wrong reasons...
@PM2Ring Nuclear weapons are also for peace too: (special exceptions exist) qr.ae/TW49NA
 
PM 2Ring
PM 2Ring
@AbhasKumarSinha Well I answered that at the start of this conversation: build big sensitive neutrino detectors. With several such detectors around the world, you could locate the illicit neutrino sources. And if you're close enough, sensitive seismological detectors should be able to detect explosions.
 
Abhas Kumar Sinha
Abhas Kumar Sinha
@PM2Ring ah okay...
Ah okay, bye...
 
PM 2Ring
PM 2Ring
3:58 PM
@AbhasKumarSinha Personally, I approve of nuclear power reactors.
But you do need to be sensible, and not build them in places prone to earthquakes, tsunamis, etc...
 
Secret
Secret
4:42 PM
Discalar
Orientation is the direction
Ratio of the parallel lines is the first scalar
Height of the trapezoid is the second scalar
Pretty sure nothing special since you can capture the same amount of information using a complex vector in 2D space
 
Ryan Unger
Ryan Unger
@Slereah teitelboim was supposed to be here but there was some medical issue
:(
 
ACuriousMind
ACuriousMind
5:13 PM
@RyanUnger He's not called Teitelboim anymore!
 
Ryan Unger
Ryan Unger
@ACuriousMind what
That’s what the speaker called him
Ah Bunster
Yeah I saw that on the slides you’re right
I didn’t understand
Why did he change his name?
 
ACuriousMind
ACuriousMind
Apparently, this politician Volodia Teitelboim wasn't his actual father but it was kept secret. I'm not clear on why exactly since everything that goes into more detail is in Spanish.
 
Ryan Unger
Ryan Unger
I see
Neil Turok has claimed string theory is finished
Not needed
Amazing
 
Scientist Smith YT
Scientist Smith YT
5:37 PM
@yuvrajsingh Ah ok I understand now. Holy smokes it was right in front of me this whole time! Thanks :)
 
DanielSank
DanielSank
6:00 PM
Здравствуйте, всё.
 
Slereah
Slereah
@RyanUnger Well at least that's over
Onto the next one
 
vzn
vzn
@RyanUnger hmmm, a 4th woit+smolin+hossenfelder contrarian? ref? (he was director perimeter inst 2008-2019)
 
Ryan Unger
Ryan Unger
There’s lots of anti string theory people around
I meet more anti than pro
 
Slereah
Slereah
it is fashionable
what would be the most bold stance on quantum gravity
 
vzn
vzn
6:15 PM
Neil Turok stepping down as director of Perimeter Institute for Theoretical Physics therecord.com/news-story/…
 
Slereah
Slereah
I believe the true theory of quantum gravity is the Schrödinger-Newton theory
 
Ryan Unger
Ryan Unger
@Slereah turok’s was bold
He said the path integral converges if you take the right contour
He claims to have found it
So quantum gravity is solved
 
Slereah
Slereah
@RyanUnger Euclidian or Lorentzian?
 
Ryan Unger
Ryan Unger
He said the Euclidean path integral is nonsense
So the Lorentzian obviously
 
Slereah
Slereah
Usually people say the other way around
I mean it's probably fair for curved spacetimes
 
Ryan Unger
Ryan Unger
6:21 PM
Wick rotation is missing
 
vzn
vzn
[String theory] almost self-destructed, I would say because it turned out to be not just one theory but this vast collection of theories which could all give different descriptions of the world. —Turok cbc.ca/radio/ideas/…
 
Slereah
Slereah
6:54 PM
I mean sure, but the same is true of quantum field theory
or quantum mechanics, really
 
vzn
vzn
> So I think that sort of theoretical catastrophe, as I view it — meaning the logical pursuit of quantum mechanics and relativity over a hundred years was tremendously successful at some level but finding its own successor theory, it hasn't been successful.
> I think that is also laying the ground for some sort of revolutionary change in the sense that we basically will have to go back to the founding principles. It looks like the founding principles of modern physics — quantum theory and relativity — have played out and they have not given us the answers we need. And so we have to go back …
> So, I think this is a very, very exciting time to be doing theory. The challenge is enormous. The clues are enormous. We're waiting and we're preparing and we're encouraging people to take radical leaps.
 
Novalium Company
Novalium Company
7:19 PM
@AbhasKumarSinha Can you tell me exactly what in my assumptions is wrong?
 
Sir Cumference
Sir Cumference
user image
2
thank you google for the incredibly useful information
 
ACuriousMind
ACuriousMind
technically correct is the best kind of correct ;)
 
Sir Cumference
Sir Cumference
7:41 PM
also weird how "earth radius" doesn't give you the number while typing, yet "earth size" gives it
 
Aaron Stevens
Aaron Stevens
8:15 PM
Sometimes I start thinking about how crazy it is that we can use mathematical models to actually learn things about the world around us.
 
JMac
JMac
@AaronStevens It's clear to me that math is actually a malevolent being who has devised a very cunning way to enslave a whole species. It just appears like an abstract concept, because of camouflage.
 
Aaron Stevens
Aaron Stevens
@JMac I have been reading stories where that is pretty much the main idea haha
@JMac About how math has been used to oppress people
 
 
2 hours later…
Semiclassical
Semiclassical
10:41 PM
@JMac now I wonder what maths natural predator would be
 
Jake Rose
Jake Rose
11:13 PM
Anybody know any good books that talk about impact parameter for two particles nearly colliding?
 

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