The h Bar

6:21 AM

@Slereah I finally have a question for which you sir are uniquely qualified for!

https://physics.stackexchange.com/questions/502408/equivalence-principle-hold-in-special-relativity-let-alone-qft?noredirect=1#comment1132570_502408

8:16 AM

@ACuriousMind Find the Fourier series of such a function

@Slereah for once I'd be willing to talk to u even about fluid mechanics or thermodynamics as long as it answers the question I tag u in :P

9:06 AM

@Slereah Thanks, but I value what little sanity I have left ;)

9:46 AM

@ACuriousMind It's not easy to even draw that one. :) But Mathworld has a variant that is kind of plottable: f(x) is 0 for irrational x; and 1/b for rational x = a / b in reduced form. It reminds me a bit of Farey sequences & Ford circles, but I suppose that's partly an artifact of the finite size of the plot.

@PM2Ring what is this interesting ongoing discussion in the chat about? Can I have a link/text to question/chat -link?

@MoreAnonymous It's just a tangent flowing on from the question here

10:03 AM

@ACuriousMind I have some sort of short follow up question

Which is mildly related

$$ \prod \frac{a_i - b_j}{a_i - a_j}$$ is not well-defined if we permit the case $i=j$ inside the product

But if we look at the reciprocal of this same product, we may permit the case $i=j$

Oh and let's say the $a$' and $b$'s are some discrete sets of real variables

@1010011010 Sure - but you just get 0, so its reciprocal is still ill-defined

Isn't the empty product defined to contribute a value of 1 to the overall product?

Or is that only for products of all zeroes?

Multiplying with a zero is very different from the empty product!

Oh, fair enough

Hahah omg I'm being so sloppy

Glad I'm not in the Maths chat :D

The empty product is a product over an empty set, i.e. it contains no mutliplicands at all

10:09 AM

Excellent, this answers everything :D

10:43 AM

@ACuriousMind Umm ... I wanted to say sorry ... Clearly in the heat of the moment I posted something dumb in meta ... I apologise

I'm just reading the starred messages it's amazing how many of them are related to me :P

10:57 AM

@PM2Ring I made a quick and dirty estimate for the waste water release pathway. Some of the things that would be more interesting for terrorists are missing from my list. But we don't need to tell that to the OP. ;-)

And I still think that the whole mess would be better suited to Worldbuilding.

11:16 AM

@Loong Thanks. Does your final calculation mean that you could contaminate enough water to give roughly 10000 people the annual dose limit of 1 mSv? Also, why "you would not be able to release this inventory to the environment." Is it simply too dangerous to get access to that waste?

12:19 PM

@PM2Ring Yes, that's roughly correct – if you could dilute and distribute the water so precisely.

"you would not be able to release this inventory to the environment." – this inventory is in form of fuel assemblies.

I.e. the radionuclides are mostly bound in a solid UO2 matrix.

A small part is present in the gap between the fuel and the cladding.

You would need a core melt accident to get all of the Cs-137 out of the fuel rods.

And then it's still inside the RPV.

If the corium melts through the RPV, it would still be in the containment.

There is no direct water connection from the containment to the sea.

12:35 PM

Is the torque of the gears in the transmission box of a manual car the same? (Therefore only force and radius vary)

For example the torques of 1st, 2nd, 3rd... gears are all the same?

@Loong Ah, of course. And it would take a while (and I guess stuff like hydrofluoric acid) to liberate it.

In that case, the terrorist might prefer going to a nuclear fuel reprocessing plant.

@NovaliumCompany Wikipedia has good articles about gears & gearboxes. Gears are used to multiply (or divide) torque, just like levers multiply linear force. The point is to convert the torque from the engine to the torque that the wheels need at the current speed (and load). Engines have a limited band of torque that they can deliver effectively at a given rotation speed RPM). So the gears let the engine operate near peak efficiency while providing a wide range of wheel speed.

Low gears give the wheels low speed, but a lot of torque. High gears give high wheel speed, but not a lot of pulling power.

You should also look at the Wikipedia article on starter motors.

How seeds grow? I mean, who could possible have created something brilliant... a thing as small as a tooth that feeds of the environmental resources and grows to be something else with predefined shape, chemical structure, processes... my logic tells me that predefined information must be stored somewhere, the DNA?

@PM2Ring So the torque of the gears is not the same?

@NovaliumCompany You're doing that thing again where you're asking questions that are straightforward to ask Google or Wikipedia about...

@MoreAnonymous Apology accepted. If it helps, this was far from the worst I've experienced as a mod here ;P

12:51 PM

@ACuriousMind for entertainment purposes does the worst have any meta post at all :P

Even if it had, I wouldn't point people towards it. The past is the past.

@ACuriousMind I'm pretty sure I know the answer to the question, it's the DNA, the genetic code, and to some degree, environmental factors, but I can't help but wonder, who created this... it's so perfect to be accidential.

@ACuriousMind I pretty sure I've pissed off the chatroom before...

@MoreAnonymous That time we talked about porn and stuff, I'm sure we pissed @ACuriousMind a bit.

lets apologize

@NovaliumCompany It's not "created" (at least not in the usual sense of the word), but the result of at least 3 billion years of evolution.

i apologize

@ACuriousMind How did it start?

me 2

@NovaliumCompany are you talking about the anthropic principle? If not what are u guys going on about?

12:57 PM

@NovaliumCompany We're not sure, but we have some good guesses: en.wikipedia.org/wiki/Evolutionary_history_of_life, en.wikipedia.org/wiki/Abiogenesis

How are we talking biology here ???

Why wouldn't we?

@ACuriousMind Cool. And what also bothers me is, how constants exist, that if they werent exactly what they are, the universe will not exist

Isnt bio stack exchange and Im sure they got a chat too?

This is the chat for physics.SE but there's no rule at all that says all we can talk about is physics

12:59 PM

^

^^

Agreed ... But neother of us experts (I suspect) in that case redirect?

@ACuriousMind and there is also xkcd 435 ;-)

Also "And what also bothers me is, how constants exist, that if they werent exactly what they are, the universe will not exist" ... This smells of anthropic ... I swear it does!

@NovaliumCompany Well, if you believe that it is meaningful to say that the constants "could have been different", then that's called the "fine-tuning problem": en.wikipedia.org/wiki/Fine-tuned_universe

@Loong Yes, but we also talk about math in here even if it is purer ;)

1:01 PM

isn't energy pure?

:P

Yes, but usually our math isn't so pure. ;-)

@ACuriousMind I believe, that if the constants were different, life and the universe will still exist but will be different from what we can imagine

@ACuriousMind You again prove to me that everything I ask is answered in wikipedia lol

@NovaliumCompany perhaps, start there :-)

@ACuriousMind is there any definition for evolution in a computational sense .. Where I define some kind of random generator but don't have our physics laws ?? And start to get intelligible computer-forms (as opposed to life forms)

Please reply my laptop battery is dyiiiiinnnngggg :(

@MoreAnonymous Certainly none that produces human-like intelligence (otherwise people wouldn't still be trying to hard to construct general AIs), but you can of course code evolutionary patterns into a computer program: en.wikipedia.org/wiki/Conway%27s_Game_of_Life, en.wikipedia.org/wiki/Genetic_algorithm

1:15 PM

@Loong Speaking of xkcd, the forum's still offline :( forums.xkcd.com

Hey the math people

Consider this :

Globally hyperbolic manifolds are foliable by timelike geodesics

@NovaliumCompany Wikipedia isn't perfect, but it's usually a good starting point, and it gives references that you can follow up with.

As foretold by the geodesic flow of the Cauchy surface

But let's consider this :

If I have a globally hyperbolic spacetime

With a foliation

And a unique non-geodesic curve

Is there a foliation such that this curve is part of the foliation

I'm thinking maybe by considering a foliation by geodesics outside of a certain radius and then inside the radius a transition to that curve

Bump function of the acceleration sort of thing

But then I'm thinking about Rindler observers and I'm thinking this may be tough

Actually... If I have initial conditions $\gamma(0), \gamma'(0)$ and the acceleration $\alpha(\tau)$, does that uniquely determine a curve

that would help

Secret

Today's PhD blue is trying to suggest quantum mechanics is somehow broken:

in The Periodic Table, 13 mins ago, by Secret

Either the thing calculated by easyMECP is not the sought for conical intersection, or that we have a very bizarre barrierless intersystem crossing which upon spin flipping, the molecule rotates by 90 degrees without changing energy

There is no way can a pair of atoms rotate about a centre, flipping an electron spin in the process, without any energy change

Having said that, this molecule is very strange for its $<S^2>$ is around 1.5, suggesting it is heavily contaminated by some triplet state

1:34 PM

How should one interpret this:

$$ \int f(x) \exp(i*g(x)) dx $$ ?

Is it $f(g(x))$? Surely it's not?

Oh, the zero of $g(x)$ is contained in the integration interval

I read on wikipedia about gearboxes but what confuses me is what's the deal with the torque being a product of the output force of a gear and radius. So if I'm on 1st gear, the radius is small, but the force is high (therefore the car becomes more powerful and can climb inclined planes), when I'm on 4th gear the radius is high, but the force is low (therefore the car will suffer climbing mountains). So is the torque of the gears constant? I understand that the power (torque * speed) is constant

so the engine delivers medium torque and medium speed, and the gears increase/decrease the torque for the inversely proportional increase/decrease in speed.

@1010011010 I don't understand what you mean by "interpret".

ZeroTheHero

@1010011010 The result is a number since you integrate over the only variable in the problem so it cannot be $f(g(x))$, still $x$-dependent. Otherwise this number is just the area under the real part plus the area under the imaginary part.

@NovaliumCompany I suggest that you find a friend who owns a bicycle with gears and do some experiments. Turn the bike upside-down, and crank the pedals by hand at different speeds, in different gears. Use your other hand to put an extra load on the wheel; you may wish to wear gloves while doing that. ;) You need to experience this stuff to get a good feel for it.

@PM2Ring OMG! I'm literally going out to ride my bike with gears :DD right now

@PM2Ring I feel it, but I'm struggling on the equations side and how they relate to what I "feel"

anyways, I'll go to ride the bike now, I'll continue when I return

1:49 PM

cya pal

@ACuriousMind Well, it's not a Fourier transform, and the exponential kind of reminds me of delta function. Should I be equating it to f(x) evaluated at the zero (zeroes) of g(x) if these are in the integration interval and 0 otherwise?

Up to some constants?

No, why would you?

I'm looking at this: math.stackexchange.com/questions/1343859/…

Letting x -> f(x) under the integral gives delta(x)/|f'(x)| on the RHS, then by the source method I should get something similar to what I said above (?)

2:05 PM

No. Please try to actually formally write down what you want to do here, because it doesn't work at all. Note also that your integral has no free variable, its result is a fixed value, not a function.

Q: Which temperature transformation does QFT allow?

@ACuriousMind maybe they didn't run the simulation long enough :P with enough computation power :P

And can someone enlighten me to why this is a bad (downvoted) question?

-1

Background Taken from here Is temperature a Lorentz invariant in relativity?: Einstein himself, in a 1907 review (available in translation as Am. J. Phys. 45, 512 (1977), e.g. here), and Planck, one year later, assumed the first and second law of thermodynamics to be covariant, and d...

@MoreAnonymous I didn't vote on it either way (yet), but it's not clear at all why you think "QFT" has any special position on it, given that QFt doesn't even necessarily deal with systems that have temperature. The question also shows no research attempt on your part at all beyond reading the question you linked. Also, please don't leave comments asking for the reason for downvotes - if the downvoters had wanted to leave a comment they already would have, so it's just noise.

2:20 PM

Hmm .. okay my bad ... But thanks for letting me I have to let people know why "QFT" has any special position on it ... QFt doesn't even necessarily deal with systems that have temperature (I suspect the we're talking about 0 kelvin fields) ... Maybe statistical field theory might have been a better word ??? But Im not really familiar with it so i didnt use it

"temperature" is a property of statistical systems in (near-)equilibrium. Scattering processes - i.e. QFT as used in high-energy physics - are no such systems. There's also QFT that deals with far-from-equilibrum physics, etc. In other words, your question is much like as if you had asked "What does classical mechanics say?" when most of classical mechanics doesn't deal with temperature at all.

I see .. I thought in this context it might be self evident ... But ur right ... I'm currently editing the question. Thanks :)

Also I find the comment: Scattering processes - i.e. QFT as used in high-energy physics - are no such systems.... quite interesting ...Like I remember the S matrix and all but I mean if ur using an S matrix ur probably thinking of some Hamiltonian too ... In which case I'm not sure why I can't use any of: en.wikipedia.org/wiki/Thermal_quantum_field_theory

@ACuriousMind If your answer is gonna take too much time (and u don't wanna give it) ... I wouldn't mind a reference?

@MoreAnonymous It explicitly says that it computes expectation values in a canonical ensemble. If you look up the definition of a canonical ensemble you'll find it is ill-suited to model what's going on during HEP scattering.

Ah .. I see .. got it ...

Just looked at the formula and skimmed the text :P

Well, don't do that!

2:38 PM

I should have just googled it and found a comment of yours :P

The problem of the question is not the temperature, but that it doesn't specify an explicit theory in which one could compute these crosssections and therefore definitively answer it. – ACuriousMind

Sorry entire comment:
"I'm not convinced this is correct. Thermal quantum field theory is certainly a thing, and it appears quite sensible to me to be able to ask whether the crosssections (in the sense of QFT, i.e. the n-point functions of the field operators) go up or down with temperature. The problem of the question is not the temperature, but that it doesn't specify an explicit theory in which one could compute these crosssections and therefore definitively answer it. – ACuriousMind"

If you click on the timestamp behind a comment, you get a permalink that you can use to paste the entire comment into chat:

I'm not convinced this is correct. Thermal quantum field theory is certainly a thing, and it appears quite sensible to me to be able to ask whether the crosssections (in the sense of QFT, i.e. the n-point functions of the field operators) go up or down with temperature. The problem of the question is not the temperature, but that it doesn't specify an explicit theory in which one could compute these crosssections and therefore definitively answer it. — ACuriousMind ♦ Dec 19 '17 at 13:21

like that

@ACuriousMind How can there be something "quantum" but somehow your not allowed (or don't know) how to talk about temperature?? Are there more sub-fields like that?

I was under the impression talking about thermodynamics in classical mechanics is really difficult because of having it being classical and not quantum

I don't understand the question - when you do Newtonian mechanics for balls on a billard table, it's also hard to see how to talk about temperature. Again, temperature is a property of statistical systems in or near thermal equilibrium. There's lots of things that are either not usefully thought of as statistical systems or not in equilibrium.

Q: Can a single classical particle have any entropy?

I'm glad you say "hard" and not "impossible" ... reason why I say that .. is answers like these:

18

recently I have had some exchanges with @Marek regarding entropy of a single classical particle. I always believed that to define entropy one must have some distribution. In Quantum theory, a single particle can have entropy and I can easily understand that. But I never knew that entropy of a s...

thermodynamics statistical-mechanics entropy

there's an incredible amount of alcohol at princeton

it's weird coming from a dry campus

2:51 PM

Ur at princeton!!! WOW!

there's a bar in the basement of grad student housing

@RyanUnger students

and there's free alcohol almost every night somewhere on campus

Are known for imbibing

half of the students

the really good ones don't

2:53 PM

stay smart, stay sober

@RyanUnger obviously alcohol levels don't corelate to ones intelligence :P

@RyanUnger never forget where you came from

@RyanUnger ocf.berkeley.edu/~abhishek/chicphys.htm

@skullpetrol from a campus with no booze

not sure I can go back there

Gradshteyn, I.S., Ryzhik, J.M., Ryzhik, I.M., & Jeffrey, A., Table of Integrals, Series, and Products

If you want it, it's in here in one form or another. This is the book to consult when you've got an integral you can't solve on your own. The tome's authors have tabulated something like 20,000 integrals. (There's an amusing story here, possibly apocryphal: The authors of the original edition spent about a year locked in a cabin in Siberia just doing integrals. Supposedly, they measured an integral's difficulty by counting how many vodkas they needed to drink before finding a solution.) Un…

Are you saying you are better than Gradshteyn and Ryzhik

2:57 PM

today I'm gonna take some of the European students to Costco

teach them what America is really about

@ACuriousMind also in scattering I am of the opinion it's useful?

https://physics.stackexchange.com/questions/375150/why-did-dark-matter-interact-with-the-standard-model-particles-in-the-early-univ

@RyanUnger America is about Costco?

America is all about buying terrible cheap things in great quantity

For Winning The Nobel Prize, Niels Bohr Got A House With Free Beer ... after he won the Nobel Prize in 1922, the Carlsberg brewery gave him a gift – a house located next to the brewery. And the best perk of the house? It had a direct pipeline to the brewery so that Bohr had free beer on tap whenever he wanted.

6

Lil Nas X - Panini (ft. DaBaby) [Chowder Video]

Hey panini

3:06 PM

@Slereah and here i always thought america is about the american dream :P

@NovaliumCompany wb

@skullpetrol thx

I rode my bike but I'm still confused on the torque part. Is torque of the gears same?

@PM2Ring ...maybe I should've stayed in academia after all ;)

Hm

If I have some timelike curve on a spacetime

Then I'm gonna have at least a normal neighbourhood that is foliated by a family of curves which include that curve

If I can make it so that the boundary of that neighbourhood is geodesics, then I'm safe

I think it might be doable

Timelike curve $\gamma$ in $M$ > tubular neighbourhood around $\gamma$ foliated by curves $\gamma_x$ > each $\gamma_x$ has an acceleration $\alpha_x(\tau)$ > use a bump function so that $\alpha_0 = \tau$ and $\alpha_x = 1$ on the boundary

Does that sound okay

hey PANINI! don't you be a meany naaa

::whistles::

nvm

about the gears, I watched a video and understood everything

I've literally watched all movies in existance

plz help

3:30 PM

@NovaliumCompany I don't know what to tell you that isn't on Wikipedia or my previous messages. A gear train takes some input torque and produces an output torque. Say the engine is turning at 60 RPM, with a torque of 10 units. It's driving a gear with 100 teeth, and that gear is driving a gear with 50 teeth, so for each revolution of the 1st gear, the 2nd gear revolves twice. So that gear will be doing 120 RPM, and it has a torque of 5 units.

Q: Focal plane of ideal thin lenses and spherical mirrors

Yep, I watched a video and understood everything. I just didn't know that the force in the torque equations is a constant.

Now that the force is constant, the torque is determined by the radius. So a gear that has a larger radius, will deliver more torque, but will be slower in speed (therefore power = torque * speed of the gear (angular))

user8718165

Hello everyone! Could somebody please have a look at my question? I searched for answers but couldn't find one.

0

Recently I was studying about optical instruments and in my book I came across a point which stated that When non axial parallel rays are incident on an ideal spherical mirror at a small angle or a parabolic mirror, the rays meet at a point on the focal plane rather than the focus point. Also ...

optics visible-light geometric-optics optical-materials

Hm

I guess the causal diamond of an observer in a globally hyperbolic spacetime is itself globally hyperbolic

ie $I^+(\gamma) \cap I^{-}(\gamma)$

Say to meeee watchuuu waaant from meeee

hey panini

if not hole-free

3:45 PM

don't you be a meany naaa

Don't spam the room with random lyrics, please :P

@ACuriousMind xD sorry

@ACuriousMind acuriousmind.com

@ACuriousMind you misspelled drug seller on that site

ye

@Slereah I was thinking the same thing

3:48 PM

@ACuriousMind do these drugs help increase my IQ ? :P

or do they only give me "a curious mind" :P

How can you possibly not click on this movie

(just for the record, I'm not involved with that site at all)

@ACuriousMind that's what a drug seller would say

:O

@ACuriousMind curious and curiouser :P

3:53 PM

@MoreAnonymous might watch that movie

which version of Alice in wonderland though

@ACuriousMind how deep down the rabbit hole are you :P

I ate the rabbit

@ACuriousMind :O

lol

it tasted blue

3:54 PM

No eat the red pill or the blue pill!!!

yep, he's a drug seller

The Matrix - Tumbling down the rabbit hole. . .

The matrix 4 dude

what the hell is this

The Matrix (1999) - The Pill scene

I'm setting my guess now: In The Matrix 4, (since Neo died in 3) will wake up and realize what he thought of real life will actually turn out to be another matrix.

3:55 PM

@NovaliumCompany I'll watch matrix 4 .. I dont give a link to the entire movie it's references to the points I'm making :P

Down the rabbit hole was a reference to matrix and not alice in wonderland

:P

curiousest

Adjective: curiousest

(informal or nonstandard) superlative form of curious: most curious
Honourable even in the curiousest pointes of honour, whereout there can no disgrace nor disperagement come unto her.
"But the curiousest thing a'most as I ever see at sea," resumed the mate ....
What was the curiousest thing he had seen? Well! He didn't know. He couldn't momently name what was the curiousest thing he had seen, — unless it was a Unicorn, — and he see him once at a Fair....

whomst

'd've

the curiousest mind

@skullpetrol sorry whomst?

I feel like I should create a new user id called ACuriouserMind

Con-cidentally it will have the same display image as that of @ACuriousMind 's :P

3:59 PM

@MoreAnonymous if you do, i'll create "the curiousest mind"

@NovaliumCompany i suspect u love dank memes

@MoreAnonymous yaa

If you don't like dank memes, then whomst'd've do you think you are?

@skullpetrol Soon we'll have our own Curious Stack Exchange

:D

I'll create ACurious'd'veMind

Key & Peele - Cute Puppies

4:01 PM

@NovaliumCompany I had a canadian friend who I was trying to expose to dark humor

lesson 101:

Lets just say I was in the college office on behaviour grounds

And I'm posting it here cause I still dont think its dark

It wasn't even 101 it was sissy dark humor 101

Alice and Bob in Wonderland

@Slereah good one! but like I said I was referencing the matrix :P

@Slereah Sounds like the title of a QC magazine

Fast and Curious xD

XD XD XD

4:07 PM

ok srsly tho, imma watch fast anf furous 8 cya

later

@NovaliumCompany ... Click on the spoilers link: time.com/4725171/fast-furious-8-ending-fate

@skullpetrol <3 ur the only person telling me bye everything <3 <3

Then u can stay in the chat :P

nope

4:08 PM

<3

@NovaliumCompany U gotta agree I'm nice ... I could have not called it a spoiler's link

:P

On Physics note: Does anyone know the answer to this?

can non-relativistic accelerations result in nontrivial influences in QFT cross-sections? (nontrivial meaning, other than coordinate and momentum classical transformations of on-shell legs)

the user: lurscher was suggesting I ask this ... I thought he knew the answer (and suggested he share it in chat) ... Maybe he doesn't ?

@MoreAnonymous Accelerations of what? A quantum state does not have any property that could be straightforwardly identified with "acceleration".

A scattering in-state for a cross-section is fully specified by giving its momentum. There's no room to specify any acceleration.

I have the impression that you really should learn the actual formalisms of QM and QFT properly before you go and ask all these poorly defined questions.

Some of them will dissolve, while you will be able to actually formalize those that survive in a way that makes sense to others without these lengthy back-and-forths in chat.

@ACuriousMind If u read the comments then u might get a jist of what I;m talking about ... Though I am certain the notion of acceleration in SR and GR are different ...

The comments of what?

You didn't link anything.

Q: Why doesn't acceleration in QFT lead to horrible paradoxes?

Oh I thought u knew my bad

-1

Background So I remember that in Special Relativity while one can define acceleration things can go horribly wrong has happened historically (I'm sure there many other paradoxes). The real reason of things going wrong is while in special relativity on can talk about acceleration in a limited sen...

quantum-field-theory special-relativity reference-frames acceleration inertial-frames

4:20 PM

No, these comments do not give me a clearer impression of what you're trying to ask.

@skullpetrol Nonsense, of course acceleration exists in SR

nvm

ugh

@ACuriousMind sorry for taking time to reply I just wanna b very careful on how I phrase my words

What are the definitions of dimensions? How to travel to 5th dimension?

Dec 21 '17 at 2:07, by DanielSank

Internet chat is an asynchronous communicaiton protocol.

There's no need to rush anything. Take as much time as you want

@AbhasKumarSinha When used in the sense of "3rd dimension" etc., physics usually uses the notion of dimension of a manifold. "the 5th dimension" is not a place (neither are the 1st, 2nd, 3rd and 4th dimensions) and you cannot travel to it.

4:28 PM

@ACuriousMind So, what is the use of discovering that there are 11 dimensions?

Okay I should have used the word "Accelerating reference frames" .. That would be better?

@AbhasKumarSinha Well, we haven't "discovered" that - string/M-theory have little experimental support so far.

@ACuriousMind would "Accelerating reference frames" save the day?

@ACuriousMind What experimental support so far?

And in any case, the "use" of M-theory being actually correct is not in any practical thing we could then do, but in us having a correct and full theory of quantum gravity.

4:31 PM

@ACuriousMind That doesn't sound good, what are the research areas where the research regarding 5th dimensions are going?

@MoreAnonymous I'm sure you have an idea what that is supposed to mean, but I don't-

What problems do you think QFT should have with accelerating reference frames? Scattering amplitudes are scalars, they don't care about frames (since all observers must eventually agree upon what particles were produced by some process).

wait are u asking what "accelerated reference frames" means / the comments / something else? (me confused)

@AbhasKumarSinha String theory/M-theory are almost certainly the theories you have heard about in the context of extra dimensions.

@ACuriousMind why accept such theories when there are no practical evidence of that?

@AbhasKumarSinha Well, most people I know don't "accept" them! They're a subject of ongoing research, not settled science.

4:34 PM

@ACuriousMind I'm sure the laws of special relativity hold in an infinitesimal region around a freely-falling observer ... Is not the same in QFT or SR ??

^yes that is the equivlance principle ...

That's not an answer to my question.

@ACuriousMind We need a much better scientist to work on M theory and tell us how to go to 5th Dimension.

Well u asked "What problems do you think QFT should have with accelerating reference frames" .. My answer "laws of special relativity hold in an infinitesimal region around a freely-falling observer ... Is not the same in QFT or SR "

@MoreAnonymous no, that isn't equivalence principle

Equivalence principle

In the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference. == Einstein's statement of the equality of inertial and gravitational mass == A little reflection will show that the law of the equality of the inertial and gravitational mass is equivalent to the assertion that the accelerat...

@AbhasKumarSinha Read axiom 1 physics.stackexchange.com/questions/164598/…

4:36 PM

There is a single effect in QFT that is related to accelerating frames that I know of, and it's Unruh radiation, whose gravitational mirror (equivalence principle!) is Hawking radiation.

@MoreAnonymous precisely, quantum isn't same as macroscopic, so, equivalence principle may or may not be true for quantum objects

@AbhasKumarSinha is there any quantum equivalence principle out there?

@ACuriousMind

And the Unruh effect has been in the literature since 1973, so not exactly the forefront of theoretical research. Efforts at actually detecting the Unruh effect are currently being discussed, but it's not like people are just thinking about this now - they've been thinking about QFT in non-inertial frames for over 50 years. – probably_someone

@MoreAnonymous arxiv.org/abs/1712.02054

I must admit that I still don't understand your question properly

@ACuriousMind Bogoliubov transformation

@AbhasKumarSinha theres a whole nightmare situation of QM and Equivlance principle out there ...

https://physics.stackexchange.com/questions/72916/does-quantum-mechanics-violate-the-equivalence-principle

@AbhasKumarSinha I wrote googled "Quantum Mechanics Equivalence Principle" and got your arxiv.org/abs/1712.02054 ... Curious and curiouser ?

4:42 PM

@MoreAnonymous I don't understand where the problem is supposed to be, nor am I certain I understand what "...Is not the same in QFT or SR" is meant to refer to. Can we drop the textspeak and write full, coherent sentences?

Sure

If your question is "Is QFT incompatible with general relativity?" then the answer is yes. This has been known for ages.

QFT works entirely fine with accelerated observers

It's not as pleasant but there is certainly a formalism in place

@ACuriousMind Well depends on the spacetime :p

@ACuriousMind maybe we should start somewhere waaay more basic?
https://physics.stackexchange.com/questions/502408/equivalence-principle-holding-in-special-relativity-let-alone-qft?noredirect=1#comment1132570_502408

Let's start with that. First sentence:

> I am pretty confused of why people are hopeful to find a version of the equivalence principle ("the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system") within QFT.

Who are these people who are hopeful? Where have you read about them! Please do not assume readers of your questions can read your mind or have read the exact same sources you have; provide citations for any assertions about "other people" you make like this.

Second sentence is superfluous.

Third:

> Within Special Relativity the definition of acceleration is limiting (to say the least).

4:46 PM

Yea .. I remember juan macaldena - string theorist saying something like that in some youtube video ... I swear I searched but couldn't find it

I did find a Lee smolin Quantum Equivalnce Princple

No idea what that's supposed to mean. What is it limiting and how?

> In light of this I was curious if there existed a version of the equivalence principle within Special Relativity?

Now we come to the actual question, but it's not clear how it could have an answer. Pretty much by definition, special relativity does not deal with gravitational phenomena, you need general relativity for that. It's unclear why you're looking for this principle in SR

Though to be fair that may be more in the context of QG (skimmed through the paper)

^the Lee smolin one

1 min ago, by ACuriousMind

Now we come to the actual question, but it's not clear how it could have an answer. Pretty much by definition, special relativity does not deal with gravitational phenomena, you need general relativity for that. It's unclear why you're looking for this principle in SR

Semiclassical

You can have gravitation in SR, simply in the sense of “force in a rest frame is 1/r^2”. But there’s no notion of equivalence implied by that

^

4:50 PM

Yeah, sure

@ACuriousMind I am seriously confused
1.I can indeed define acceleratiion in SR
2.This defination is similar (if not identical (?))to the one in GR
3.But special relativity does not deal with gravitational phenomena
4. So you can't have the equivlance principle
5. Even if - the laws of special relativity hold in an infinitesimal region around a freely-falling observer - is the equivalence principle definition we go with?

Which statements are wrong? (and please clarify point 2 is it identical or similar)