The h Bar - 2019-11-22

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12:42 AM

@ACuriousMind Indeed this was correct

I just spoke with her and she confirmed this is the case

it still messes with my head and my beliefs about what the German language can and can't do, as instilled by intro courses, but I guess language will do what language wants to do ¯\ _(ツ)_/¯

1 hour later…

2:08 AM

A.(BxC)=(AxB).C is this possible? where "." represent scalar product and "x" represent tensor product

11 hours later…

1:08 PM

@baponkar for a tensor product the notation is slightly ambiguous, but the direct interpretation of your formula is wrong

Presumably you mean a vector cross product instead, though, in which case the identity is indeed true

In your notation, is the value of AxB a vector, or a higher-rank tensor?

2:04 PM

New experiments suggest the existence of a potential fifth fundamental force

> However, these latest results have not yet been validated by peers, so they must be taken with extreme caution.

2:18 PM

The X17 particle is a hypothetical subatomic particle proposed by Attila Krasznahorkay as the cause of anomalous measurement results near 17 MeV. The X17 particle could be the force carrier for a hypothetical fifth force, likely connected with dark matter, and has been described as a 'protophobic X boson' with a mass of 17 MeV. The particle has been proposed to explain anomalous angles consistently observed in the decay of beryllium-8 atoms since 2015, and observed once in He atoms in November 2019. == History == In 2015, Krasznahorkay and his colleagues at ATOMKI posited the existence of a new...

2:39 PM

"There is a claim the authors of this discovery have a history of discovering "new particles" at various masses, that go away in later studies with no explanation."

0

Q: What is the cause of motion in geodesic

The shortest or longest path in curved space between two points is geodesic . What about a body having no potential energy was put in geodesic near earth , what makes it move , May be it is about the space , what does it something to do with motion ,"if question sounds nonsense please ignore

general-relativity geodesics inertia

Please can anyone tell me about how wrong am I about this concept

3:27 PM

@Rico Remember, that even if a body is at rest (in some frame) its worldline is a timelike geodesic. That is, in a sense, it is "moving" in the forward time direction. I talked about this a couple of months ago, starting around here; you may find that helpful.

@PM2Ring hi. How are you.

I have a question, if you have time please have a look

@yuvrajsingh Ok. How are you doing?

1

Q: What makes the planets to be symmetric

I have seen, in my text books, and on nasa sites, the all the planets are symmetrical. And universe also love symmetry. What cause this symmetry, why the symmetry is important. As we know that universe is expanding day by day. Will the symmetry will change. I am a high school boy, and happy to ...

planet universe

Abhas Kumar Sinha

@PM2Ring heyo!! After a long time ?

@yuvrajsingh This part? "Can we put the local asymmetry of the universe on the quantum randomness?"

3:33 PM

Yes @PM2Ring.

@AbhasKumarSinha I'm here most days, but I don't always post. And I try to read the transcript to keep up with stuff that happens while I'm offline or busy on other parts of the network.

Abhas Kumar Sinha

@PM2Ring ah okay :)

@yuvrajsingh I suppose that quantum randomness is sort of responsible as the root cause of why the universe isn't perfectly homogeneous and isotropic at all scales. But most of the asymmetry is due to simple classical randomness / chaos.

Eg, if you set up the balls in a game of pool, so they are in a perfect triangle, when you make the first shot the balls will have a fairly chaotic looking pattern, unless the cue ball hits the target ball perfectly head-on.

Yes.

ok, simple question, but I'm having a sizeable brain fart. why is $$\frac{d}{dt}\frac{1}{2}(\vec{\Omega}\times\vec{r})^2=(\vec{\Omega}\times\vec{r})\times\vec{\Omega}$$?

how do I just see that it's crossed with $\Omega$?

Abhas Kumar Sinha

3:46 PM

user image

@PM2Ring @JohnRennie @Slereah @Secret @NovaliumCompany @AaronStevens @yuvrajsingh

sorry, messed up. hold on

:-)

$$\frac{d}{d\vec{r}}\frac{1}{2}(\vec{\Omega}\times\vec{r})^2=(\vec{\Omega}\times\vec{r})\times\vec{\Omega}$$

Abhas Kumar Sinha

@JohnRennie :-)

@yuvrajsingh In a classical analysis of particle collision, a nice ordered pattern can quickly become messy. And tiny deviations in position &/or momentum quickly become amplified. You can never know the positions or momenta with unlimited precision, and that puts limitations on how far in the future we can predict the state of the system. And that's before we start adding quantum stuff like the HUP to the mix.

3:48 PM

Yes.

Novalium Company

@AbhasKumarSinha sup

Abhas Kumar Sinha

@NovaliumCompany Bro, great :)

you?

Novalium Company

@AbhasKumarSinha same

Abhas Kumar Sinha

@NovaliumCompany where are you now?

Novalium Company

@AbhasKumarSinha home

Abhas Kumar Sinha

3:50 PM

@NovaliumCompany ah okay, I thought school

@NovaliumCompany what's the time there?

Novalium Company

@AbhasKumarSinha i'm too busy suffering there

@AbhasKumarSinha 17:50

Abhas Kumar Sinha

@NovaliumCompany suffering?

Too busy doing magic to be active in SE

Abhas Kumar Sinha

@Secret :)

Novalium Company

@Secret Said Dumbledore never

3:51 PM

user image

Abhas Kumar Sinha

@NovaliumCompany you live in bolivia?

very ancient things...

Abhas Kumar Sinha

@Secret lol

@Secret ...?

Novalium Company

@AbhasKumarSinha Bulgaria

Abhas Kumar Sinha

@NovaliumCompany ah okay, my bad...

3:52 PM

The connective tissue of everything, why things are unifying at all, at least in the spiritual angle

@yuvrajsingh An even simpler example is Rubik's cube. If your friend has a solved cube, and then does 3 random moves on it, and passes it to you, it's not too hard for you to understand the pattern so you can reverse those 3 random moves and restore the cube to the solved state. But if your friend does 6 random moves the resulting pattern can look so chaotic that reversing the sequence is likely impossible, and you have to just solve it from scratch.

Abhas Kumar Sinha

@Secret have seen ancient Indian stuff about that, you'll straight fall sick... One of the weirdest creation out there.

@NovaliumCompany Do you've github>

Novalium Company

@AbhasKumarSinha no

Most physical systems have far more degrees of freedom than a Rubik's cube, so it generally doesn't take long for an initial ordered state to look very complicated.

Abhas Kumar Sinha

@Secret why reading such things? They are not helpful...

@NovaliumCompany You use any Version Control system?

3:55 PM

@PM2Ring OK.

Novalium Company

@AbhasKumarSinha no

@AbhasKumarSinha :D Vedic cosmology can be mind-bending.

Abhas Kumar Sinha

@NovaliumCompany mail/fb/twitter? (not personal)

@PM2Ring It's still bending my minds :P

because philosophy is really cool

Novalium Company

@AbhasKumarSinha email yes. I prefer using Discord.

3:56 PM

@PM2Ring Can you upload it as answer, so that I can take it as future reference.

Abhas Kumar Sinha

@NovaliumCompany oh okay...

@Secret ..? not cool, when you are in modern world, you need modern strategies

@yuvrajsingh I'll think about it. I want to see if David adds some info about that to his answer.

Abhas Kumar Sinha

@PM2Ring India's illuminati - ancient-origins.net/myths-legends-asia/… (the 9 unknown)

Sure. @PM2Ring, I am fine, I almost recover from the incident.

Abhas Kumar Sinha

@Secret You know kamasutra? (ancient Indian book containing stuff about sex, psychology, biology, hormones, hypnosis stuff)

4:00 PM

Has anyone seen the design of the Tesla Cybertruck? It looks like someone designed a futuristic car, and then made sure that it could be rendered perfectly in Starfox for SNES.

Doubt in showing Von Mises stress and seeing it is above by 15%

Abhas Kumar Sinha

@JMac me

image.png
Here the main confusion arises while calculating the value of Von Mises stress and seeing that it is 15% above the Tresca's criteria prediction.I have arrived at the rest but I need to assume that maximum shear stress in Von Mises is equal to "Equivalent tensile stress"/√3. This is something that I am not able to arrive.The rest is quite empirical.

user image

@AbhasKumarSinha are you going to teach him.

Lol.

Abhas Kumar Sinha

@yuvrajsingh lol

@user586228 sorry, I don't really understand your question... ?

In 1947 W. H. Mills proved that there is a number A, such that the following number is prime for all integer values of n. $$ {A}^{3^n} $$

4:04 PM

@AbhasKumarSinha My query is on Von Mises criteria..So to preove that the maximum shear stress is tenrile stress/ square root(3) u need to have assumptions.That is what I am unable to arrive please help if possible.

Abhas Kumar Sinha

@user586228 Sorry, I'm not good with Von Mises yield Criterion, (I actually thought something else), although there are other smart people here, who are expert in those topics and can definitely help you :)

@AbhasKumarSinha Are u in an IIT?

@AbhasKumarSinha do you have any friend.

Abhas Kumar Sinha

@user586228 no... you?

@yuvrajsingh in real life? no

No are u an engineer btw?

@AbhasKumarSinha?

Like in that case may be u could know

Abhas Kumar Sinha

4:08 PM

@user586228 no, student

OK.

Abhas Kumar Sinha

high school student

I never knew about Von Mises inn High School

Abhas Kumar Sinha

@user586228 I too, just saw in few aerospace books...

Nice to hear.

Abhas Kumar Sinha

4:10 PM

@user586228 :-)

@user586228 I forget most of what I learned about stress analysis/failure, but for the first part, wouldn't you expect Von mises and Tresca criteria to be different stresses because they calculate failure in different ways?

"Nuclear structure" book recommendations Please!

@JMac Yes I do but this is a definite question asked in a semeter exam which you are asked to proove.

@PM2Ring do you like hiking.

@user586228 Ah okay, can't help you there then. I haven't played around with that in years, and didn't dig too deep into it when I learned it anyways.

Abhas Kumar Sinha

4:15 PM

Female graduates in science, technology, engineering and mathematics.

India: 44%
South Africa: 42%
Italy: 40%
UK: 38%
Indonesia: 37%
Brazil: 37%
Turkey: 35%
US: 34%
France: 32%
Canada: 31%
Mexico: 31%
Spain: 30%
Germany: 27%
South Korea: 26%
Netherlands: 25%

(World Bank)

@user586228 I think try engineering stack exchange.

Abhas Kumar Sinha

unbelievable!! I thought most of the females opt for medical exams...

Bhai ratio in thanks to government.

A st girl with rank of 60k in jee advanced can get iit bhu cs.

Abhas Kumar Sinha

@yuvrajsingh hehehe.... reservation zindabad!

@yuvrajsingh lol yes

Actually these happens with me a girl, who do not know how to draw Fbd landed in iit bhu cs.

Abhas Kumar Sinha

4:20 PM

@yuvrajsingh lol, and they say that need empowerment...

You could argue that trying to get more women in the program will encourage more women to study STEM fields. If they are under represented, you could make the case that young women aren't even encouraged to try and learn engineering for example, because they don't see enough women in it and assume it's not for them. When engineering looks like a boys club for example, it's much less appealing to women.

@AbhasKumarSinha Please stick with English in chat. Mods & ROs can't moderate stuff that they can't read.

Abhas Kumar Sinha

@PM2Ring sorry, will keep in mind for the next time, I've flagged that for deletion too :)

@yuvrajsingh Not really. I did some orienteering when I was young, and often went on walks through the bush. But these days, I'm not so mobile due to back pain. I have sciatica from a ruptured disc in my lumber region.

Abhas Kumar Sinha

Is that really a true proof? - vixra.org/pdf/1911.0316v1.pdf seems wrong to me at the very first page...

4:28 PM

@PM2Ring how are you, does it pain.

Abhas Kumar Sinha

@PM2Ring My friend's father suffers that too, very painful situation, when he gets up to close/open the door, he sometimes gets socks!!

@yuvrajsingh I can live with it. When it gets bad I take pain-killers, but I try not to take them every day.

@AbhasKumarSinha Thanks for that haha. I didn't know I played a huge role here

Yes. Are you on a Facebook.

Abhas Kumar Sinha

@AaronStevens :-)

@PM2Ring what doctors said? surgery?

I've made a cool room for AI Enthusiasts - chat.stackexchange.com/rooms/101084/artificial-intelligence

Artificial Intelligence

This is the year 2109 on Earth. The reign of Terminators and A...

4:33 PM

@PM2Ring are you on a Facebook.

@PM2Ring I don't have to deal with it personally; but I hear a lot of scary stuff about the tradeoffs between painkillers and dependence. Must suck to have to deal with :(

Abhas Kumar Sinha

@JMac painkillers =/= harmful, unless morphine....

@AbhasKumarSinha That's a vast oversimplification...

Abhas Kumar Sinha

@JMac heheheh XD

@AbhasKumarSinha Yes. They suggested surgery, but I decided against it. One of my sisters also has sciatica. She's had surgery twice, but still suffers.

Abhas Kumar Sinha

4:37 PM

@PM2Ring Don't go for it, unless some good hospital, I've heard my previous PET teacher who was suggested to go for the surgery, now is dealing with paralysis below abdomen and knees....

@JMac The dependency aspect doesn't worry me too much, but most painkillers become less effective if you use them too frequently, so you end up needing higher doses, and putting more strain on your liver etc.

Abhas Kumar Sinha

@PM2Ring exactly...

@PM2Ring I don't know how that advice will sound you, but you can try Aryuveda and yoga, personally, I've heard 100% success rate (no side effects/pain) but it's slow, also the painkillers they give is natural and are not very hard on liver...

Come to kerala, I do of but they are famous for their traditional treatment. @PM2Ring

Abhas Kumar Sinha

@yuvrajsingh That's what I said.

@AbhasKumarSinha Indeed. We don't yet have the technology to perfectly repair ruptured discs, and the doctors freely admit that even if nothing goes wrong with the surgery there's no guarantee that it'll make you feel better.

4:41 PM

@PM2Ring In my mind I kinda wrap that in with dependency, but yeah I guess that's a slightly different problem.

I bet, no surgery, no pain killer. Just natural therapy.

Abhas Kumar Sinha

@PM2Ring You can come to India, (Apollo) they are much good doing these surgeries (If you want)...

@yuvrajsingh But, that also takes 4-5 years to heal completely...

@JMac Fair enough. And apart from the stress on liver (and kidneys & other stuff), opiate-based painkillers tend to suppress your appetite and can cause constipation if you aren't careful with them. So I try to use them only when the pain is unbearable otherwise.

@yuvrajsingh No, I don't use Facebook.

I was on morphine for a week after an operation on my leg (this was several decades ago) and I can confirm it causes quite spectacular constipation.

Abhas Kumar Sinha

user image

bow pose^

4:48 PM

@AbhasKumarSinha I don't just have a slipped disc. That disc is totally ruptured, and the one above it is badly eroded. This happened almost 20 years ago.

Abhas Kumar Sinha

@PM2Ring Doesn't matter, you can still try doing that, (for calcium buildup) ONLY IF YOU ARE COMFORTABLE DOING THAT POSE

When I was young, I could walk on my knees in full lotus position. I wouldn't try doing that these days. :)

Abhas Kumar Sinha

@PM2Ring Lotus is very hard, I don't have patience to sit at a single place for more than 10 min :P When my grandama was there, she would teach me doing those...

@PM2Ring H.O.P.E. Hold on, pain ends :)

Try AMAL. @PM2Ring

Best thing you can do.

It is a plant leave.

Abhas Kumar Sinha

@yuvrajsingh They probably don't have that in Australia.. Although there must be alternatives to it...

4:59 PM

Actually here in rajasthan, this plant which eaten from centuries.

Abhas Kumar Sinha

@yuvrajsingh Its called Indian gooseberry in English

Phyllanthus emblica

Yes.

Abhas Kumar Sinha

Here goes it's research - ncbi.nlm.nih.gov/pubmed/27898027

@AbhasKumarSinha Interesting.

Yes.

Abhas Kumar Sinha

5:05 PM

@PM2Ring :)

OK, I have some work, so bye. @PM2Ring @AbhasKumarSinha

Abhas Kumar Sinha

@yuvrajsingh bye, gn :)

1 hour later…

6:16 PM

How can I find parity operator of dirac field?

6:58 PM

0

Q: Are questions of this sort allowed?

So I was tempted to ask this question (after some slight physics edits - see comment section) in physics stack exchange and would like the wisdom of the community if it would be closed or not? Why I'm asking Meta first Crossposts between physics and math stack exchange are discouraged. It does...

Good morning/afternoon/night for everyone!

One thing isn't quite clear to me concerning the basic discussion of classical field theory. Why, in variation of the Lagrangian density, you can "treat" the fields and derivatives of the field "like a coordinate". I mean, the for of the equations are the same as for particle lagrangian dynamics...why the equations are so similar? (Because, a field isn't a coordinate!)

form*

7:58 PM

@M.N.Raia I'm slightly confused by what you mean. But have to sleep :((( It's too late in my country

8:37 PM

in Language Overflow, Nov 17 at 16:12, by CowperKettle

user image

9:09 PM

@M.N.Raia for $y = f(x)$ we have functionals $S = \int_{x_0}^{x_1} L(x,y,y')dx$ which are the analogue for $x = x(t)$ of $S = \int_{t_0}^{t_1} L(t,x,\dot{x})dt$. Similarly for $z = f(x,y)$ we have functionals $S = \int \int L(x,y,z,z_x,z_y) dxdy$ which are the analogue of $S = \int d^4 x L(x^{\mu},\phi,\partial_{\mu} \phi)$ from classical field theory. It's just functionals of multivariable functions while CM considers functionals of single-variable functions

9:39 PM

@bolbteppa but what about vector and tensor field theories?

What about them

they aren't scalar fields (functions of several variables)

e.g. Maxwell $S = \int d^4 x L(x^{\mu},A_{\nu},\partial_{\mu} A_{\nu})$

aaaah yes, you construct a scalar field

pardon.

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Nov '1922

The h Bar

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