« first day (3446 days earlier)      last day (1477 days later) » 

4:40 AM
morning to all
@JMac so much snow fall
i haven't seen snow fall in my life ,because my home town is in desert area.
How do we quantify more carefully the notion that the "curvature approaches Planck values?
 
5:01 AM
@JingleBells I haven't watched the new one. Here's a song by Sydney punk rock band, Radio Birdman, about watching re-runs of Hawaii 5-0 on late night TV. FWIW, guitarist Deniz Tek is also a medical doctor.
@Secret You may enjoy watching Greg Egan's Quantum Well applet.
 
5:17 AM
Is 178 cm too short? I feel very short.... :-(
 
@AbhasKumarSinha I'm 178cm, and I have never felt short.
 
6:13 AM
@AbhasKumarSinha Ahh I remember being insecure about my height and coming here to chat a few months back. I'm around 178 cm as well and in time, you'll learn to accept it and you'll learn to see your height as a benefit. I personally, wanted to be taller because I thought it's a necessity in the business world, but then I found out that Mark Zuckerberg is 171 cm, Jeff Bezos is 171cm, Bill Gates is 177 cm... your height is perfect for anything.
You're not too tall to intimidate and not too short to be intimidated.
Meaning, you're not too tall to make other people feel short (which is not really a good thing because many people are insecure about their height) and you're not too short to feel bad around taller people. In my opinion, the average height is the perfect one to be.
 
6:26 AM
-1
Q: Would it be possible to give 10 minutes warning to people writing answers that the question will be closed or made duplicate in 10 ,minutes?

anna vI had spent some time answering this question, when it was made duplicate by an announcement at the top "this question will no longer be accepting answers". Would it not be possible to give ten minutes grace for people who are in the process of writing an answer? "in ten minutes this question w...

 
6:47 AM
@PM2Ring sloshing around
I think quantum fields are then sloshings such that some of these we identify them as different particles
 
@PM2Ring whoaa ,how are you sir ?
 
@PhysicsMeta sigh, and that from a user who has almost 180 000 reputation
 
7:09 AM
@Secret Quantized sloshing. Yes, particles are just nice slosh patterns in quantum fields. And virtual particles are kind of messy slosh patterns. That's not controversial. See profmattstrassler.com/articles-and-posts/…
@YuvrajSingh... Hi. I'm ok. We've had a lot of rain lately in Sydney, but we had nice sunny weather today. It's rather windy, but that's ok, because my washing dried in less than an hour. How are you?
 
7:24 AM
@Loong Anna does have a tendency to answer stuff that ought to be closed... And some of her answers aren't so great. OTOH, I think it's pretty cool that we have her as a regular member on this site. I hope I'm still that sharp when I'm 79 (if I manage to last that long).
 
 
1 hour later…
8:41 AM
Probability of finding a particle in the position range a to b in the energy eigenstate in position space,$\psi_n $ is given by integral over the absolute squared wave function.For momentum range a to b,we transform the position space wave function to momentum space and integrate over the interval.


What to do for other physical observables?
e.g.--If I want to find what is the probability of finding the particle in the energy range E1 to E2 or What is the probability that the particle has angular momentum in the range L1 to L2...How to approach the problem?
 
This is actually quite a complicated question, because you need to explain exactly what is meant by the probability. For example we normally work with eigenfunctions, but these have a precise energy so the energy probability distribution is a delta function.
So it doesn't make sense to ask what the probability is for a range of energies because an eigenstate only has a single value of the energy.
The reason you can ask this sort of question for position is that energy eigenfunctions are not eigenfunctions of the position operator so the position does have a range of values.
 
So,we can find the probability of a particle in a certain energy eigenstate and then know with certainty the particular energy it has,not a range of energies?
 
If a particle is in an eigenstate then by definition you know its energy exactly.
deleted
 
 
1 hour later…
10:16 AM
@ManasDogra The logic is exactly the same for all observables. You have the abstract quantum state $\lvert \psi\rangle$ and you have the set of eigenstates of the observable as $\lvert a\rangle$ (for $a$ either continuous or discrete) and then you get a probability (density, if the spectrum is continuous like it is for position or momentum) for measuring a particular $a$ by $\psi(a) = \lvert \langle a\vert \psi\rangle\rvert^2$
There isn't really anything special about position or momentum in this respect, they are just the most common observables to choose to express the wavefunction with respect to
@PM2Ring I believe that Strassler does not use "virtual particles" there in the same sense as it is technically used in standard QFT, but more in the sense of "actual intermediate state", see this answer of mine
Rococo's answer agrees with me - Strassler gives a good impression of how a quantum interaction looks, but he does not explain the meaning of "virtual particle" in its standard usage, so you should in particular not apply this interpretation to think about standard Feynman diagrams
 
I am learning about propagators and Feynman diagrams in many body systems. Do I always have to consider hole propagation processes, or just sometimes, or never?
 
I'm afraid my lack of actual condensed matter knowledge means I'm not even sure what a hole propagation process is, so I'm not much help there
 
user434058
10:44 AM
@JingleBells Good! But I am not a fan of this kind of trap, complextro, electro, moombathon kind of electronic music :) But from production POV, you did a good job.
 
user434058
@JingleBells In case you don't know, there's a Sound Design SE. You might find it helpful.
 
user434058
@JingleBells BTW, I had some of my older tracks on the internet, but then I removed them because I made them when I was just starting out and they sounded like shit once I learnt more about production. I have a few ready-to-release tracks, but I will only get back to work after JEE :)
 
@ACuriousMind Thanks. FWIW, I've already upvoted your answer and Rococo's. Personally, I have no problem with the usual definition: "Virtual particle represent (fictitious) intermediate states over which we must sum". I think Strassler's sense of virtual particles is primarily aimed at people who've learned about virtual particles from pop-sci presentations and don't have a clue about perturbation theory.
 
I'm reading about Weyl fermions, and I've realised I have no idea of how "Weyl" is actually pronounced. Is it "Wile", or "Vile", "Whale", or maybe "Vale"? Or something completely different? Weyl was from Hamburg, so input from native-speaking Germans would be welcome.
 
@PM2Ring The problem is that the pop-sci presentations often show Feynman diagrams, which are intrinsically perturbative. I find it confusing to "explain" virtual particles by redefining them compared to what both pop-sci (wrongly) and technical texts (correctly) use.
@ClaraDiazSanchez Vile is the closest English equivalent
(source: I'm German :P)
 
10:55 AM
But even those who've heard that virtual particles represent internal lines in Feynman diagrams may not realise that those intermediate states from perturbation theory are mathematical fictions.
 
Danke @ACuriousMind that's one less distraction for me :)
 
@ACuriousMind Fair enough. That redefinition may just add to the confusion, rather than cure it.
@ACuriousMind Is it the same pronunciation as the composer Kurt Weill?
 
I think so? I'm not sure I've ever heard how anglophones pronounce him but in German they'd be the same
 
I'm not an anglophone, but I pronounce "Weill" as "Vile"
 
 
1 hour later…
12:11 PM
@FakeMod Coolio, I'm not a big fan of production and such stuff, I just like to make beats for fun for myself
 
Why not look into becoming a musician? @JingleBells
 
 
1 hour later…
1:19 PM
@skullpatrol I had this dream for about a period of 4 years (between around 9 and 13 years of age). I can actually sing pretty good and I have a "sense of music" but then I realized that that's not what I want to do in life.
 
@JingleBells people change pal, life changes :-)
 
@skullpatrol Yes, I guess that's a good thing. I feel a bit guilty for not pursuing music and stuff because people have told me I'm very good at it. I'm sacrificing the pursuit of my talent for the pursuit of my other talent, love and purpose.
 
@JingleBells Never regret doing what you love.
 
It's like my brain is associating my musical talent with all the potential dopamine, social status, and increased reproduction chances and it feels bad for not doing it. I've been struggling with this a lot actually... but I know the path I've taken and I never regret quitting the dream of becoming a singer.
 
It is never too late to change your path, my friend.
 
1:33 PM
True, but I don't want to change it. I know I'm sacrificing singing for something bigger and greater, something I'm also good at, something I find purpose in.
 
> What I think the blog post by Matt Strassler you're citing is getting at is that there is, regardless of all "virtual particles", of course an actual intermediate state during a QFT scattering, however complicated to describe it may be. He's saying that "virtual
> particles" are what physicists call that intermediate state which is...close enough, but more precisely we need to keep in mind that the intermediate states of perturbation theory aren't the same as the actual state of the system, they are computationally convenient fictions.
To be fair, I think I will be fine doing QFT without ever thinking there are particles
Both particle and wave are ultimately misleading compared to what the actual state is doing
put it in another way, I think it is ontologically more satisfying to deal with the state itself, instead of trying to give names to the terms in a perturbation as "virtual particle" as they are ultimately approximations and not the actual thing
 
@JingleBells whatever you do "have no regrets"
11 mins ago, by skullpatrol
@JingleBells Never regret doing what you love.
@Secret did you get my super ping in the other room?
 
@skullpatrol "super ping" usually refers to moderators pinging users that are not normally pingable. Non-mods cannot super ping.
 
1:49 PM
this is not a usual reference
his lack of response is my answer
 
When a charge is put in the cavity of a conductor, the charge in the conductor will configure itself so as to cancel the field generated by the charge in the cavity (so that the electric field is zero inside the conductor). If one were to place another charge exterior to the conductor, would the charge in the conductor re-configure again so as to cancel the electric field inside the conductor? Is there an infinite amount of charge then available in a conductor?
 
@skullpatrol the topology stuff?
then yes
and read that ages ago
 
@skullpatrol Yep, I don't regret quitting the dream of becoming a singer but it still hurts because I've sacrificed something that has many potential rewards.
 
2:04 PM
It should not hurt @JingleBells
 
@skullpatrol Why not?
 
@schn Yes, the definition of an ideal conductor is essentially that there an infinite amount of charge in it that's able to move without resistance
 
@JingleBells Feeling that you are sacrificing something leads to regret, right?
 
@ACuriousMind Thanks for the reply. Interesting.
 
@skullpatrol No. I don't regret sacrificing the dream of becoming a singer.
 
2:09 PM
Of course, real conductors are imperfect in all sorts of ways, but I think this is a pretty valid idealization - there is a lot of free electrons in a metal
 
Then reexamine why it "hurts" @JingleBells
Life should not hurt.
Unless, of course, you want it to.
 
@ACuriousMind If one were to increase the charge inside the cavity as well as outside the conductor (for a real conductor), what would happen? Would the electric field inside the conductor eventually become non-zero?
 
@skullpatrol sorry, what do you mean by regret?
 
@schn I think it's impractical to accumulate so much charge that we leave the regime where the idealization is valid
It's pretty hard to get decent amounts of isolated charge
But sure, if you somehow manage to do so, sooner or later you will exceed the real conductors ability to supply more charge and the field won't be zero
Whether we're then at field strengths that would rip the material apart anyway I don't know
 
@ACuriousMind What would be an example of isolated charges?
 
2:19 PM
@schn I mean the things you want to put into the cavity/outside
 
@ACuriousMind Why would it be hard to accumulate those?
 
@skullpatrol Those sentences are pretty generalized and I don't understand what you're trying to say sorry
 
They don't grow on trees ;)
I mean, you can't just put a bunch of electrons or protons in there, they just fly apart because they repel each other
 
True.
 
I think van de Graaff generators are still one of the best ways to get a lot of charge
 
2:22 PM
@ACuriousMind Fire an electron canon at a black hole
As long as the energy is larger than the Coulomb repulsion, it will accumulate charge
although it will lose some charge via Hawking radiation over time
 
@JingleBells by "regret" I mean a feeling of sorrow for not doing something that was possible at the time.
 
10 hours ago, by Yuvraj Singh...
How do we quantify more carefully the notion that the "curvature approaches Planck values?
@ACuriousMind
 
@Slereah Do we actually know that? I mean, that the Hawking radiation from a charged black hole radiates away charge?
 
sorry for pinging you !
but if you can answer that for me !
 
This would not be symmetric with the Unruh effect, so it can't be caused by properties of the horizon alone
 
2:29 PM
@ACuriousMind Well, in theory anyway, yes
Charged blackholes radiate away charge, rotating black holes radiate away angular momentum
If they didn't, imagine this :
 
Do you say that because its intuitive or because one can actually compute that? :P
 
we send a lot of charge to a black hole
It radiates mass away but not charge
the mass/charge ratio becomes such that it becomes a naked singularity
@ACuriousMind You can compute it, yes
Hawking did it I believe?
Like proportions of radiated particles
 
@Slereah My reply to all these arguments is always that Hawking radiation is semi-classical anyway so I don't trust arguments that can also be countered with "this doesn't happen because full QG kicks in" :P
@Slereah Alrighty then, that's what I wanted to know
 
@ACuriousMind Hawking radiation has been computed using a lot of QG theories, too
It's probably correct?
Unless it's a yet unknown really different QG theory that is correct
 
@skullpatrol Is this the same as wanting to go back and change things but not being able to?
 
2:35 PM
@Slereah I mean, there could be a UV catastrophe type situation where the general gist is correct but the absurd consequence isn't
 
@ACuriousMind If there's no Hawking radiation, then maybe we should worry about the LHC creating black holes!
 
I mean, maybe there's something about the charged black hole that just stops the evaporation before the singularity undresses
not a lot of charged black holes around to test!
 
There's the old theory that electrons are black holes
 
@skullpatrol Anyways, I think I understand what you're trying to say. My life doesn't hurt or anything. I just sometimes get reminded of the sacrifice that I've made and I don't feel regret, but I feel bad knowing what I'm missing out. But that "bad" feeling can't reach the happiness of the gains of my current dream. Anyways, a lady once told me that I don't have to choose between singing and entrepreneurship, I can combine them and form something better.
Maybe the next Steve Jobs will sing a song before presenting the new product.
 
2:53 PM
@JingleBells regret comes in many forms as outlined here I'm just saying try your best because that is all you can do pal :-)
 
3:08 PM
@Slereah don't forget the old one-electron universe
 
@skullpatrol wasn't really a theory :p
just a musing
 
hmm
 
@skullpatrol I understand. I guess there's some conflict or a scar in me, I have been trying to understand it for a while. It's not anything serious but it does come on my mind from time to time. I don't know if I regret or not, but if I was given the chance to go back and take a different path, I wouldn't. The idea of combining the two (singing and entrepreneurship) really satisfies me and makes me feel good inside. It feels right.
 
@ACuriousMind Moderators are not the Pope, and often it is questions from young students which are closed. An answer that illuminates some physics to the student should not be a problem for the objectives of the site, particularly as closed questions are not seen in search engines, and might help a student find his/her way into the intricacies of mainstream physics. Also think: if the moderator had seen the question ten minutes later, the answer would be there, in the closed question. — anna v 4 hours ago
@ACuriousMind Wow...all this time I thought you were the Pope
Is this correct? Should I make a meta post asking about the sanctity of moderators as sanctioned by the Catholic church?
 
@AaronStevens 1/6th of the Pope, rather. Note the plural.
 
3:14 PM
@ACuriousMind Oh the other moderators aren't a part of your hive mind?
 
The details of our mental connection are trade secrets, I'm afraid
 
@JingleBells if it makes you feel good inside, then you more than halfway there pal
 
Does this make questions about Mass on topic for PSE?
 
Questions about mass have always been on-topic!
 
It's the way we can migrate questions between PSE and Christianity SE :P
 
3:19 PM
If someone could explain the argument of why +q is distributed uniformly, that would be much appreciated.
 
@schn It might be better to tell us why the provided argument doesn't make sense to you
 
@AaronStevens Sure.
 
@skullpatrol I value legacy much more than I value happiness. I'm ready to be sad and feel bad my whole life if it means achieving the legacy I want to leave behind. Life is very short, and after that, no one cares how happy you have been, but what you've left behind. Luckily, I can be happy and leave the legacy I want to leave. But who knows, with the recent progress of AI, we might transcend soon... and who knows what happens then...
 
@AaronStevens "Is mass quantized?" - "Yes. Proof: the host comes in discrete units"
 
@ACuriousMind Had to Google "mass host" to get that one :P haha
 
3:25 PM
Is that not the common English name for that bread? It's Hostie in German so I picked the one most similar to that :P
 
Hm interesting. No, I haven't heard of bread as "host".
 
@JingleBells sure, we all have limited control of our "destiny"
 
But now I will start calling it "buttered host" instead of "buttered toast"
 
@AaronStevens Wouldn’t the +q distribution depend on the -q distribution, since if their distribution would differ this would cause an electric field in the conductor?
 
@schn The -q distribution cancels out the field from the charge in the cavity. So the +q left over in the conductor "doesn't know it is there"
Or think of it in terms of field lines
field lines will start on the cavity charge and end on the -q on the cavity surface
The remaining +q will then distribute normally as if it was just excess charge on a uniform conductor
 
3:29 PM
@AaronStevens Makes sense. Thanks.
 
@AaronStevens Well, I mean that the sacramental bread specifically is called that, not bread in general. Maybe I just assumed wrongly that everyone'd be familiar with the communion ritual :P
 
@ACuriousMind Right. Well I am familiar with communion, I have just never heard it called "host". New knowledge for me
 
shouldn't there be wine with that bread?
 
Okay, then apparently I just picked an unusual word for it.
@skullpatrol you're thinking of beans
 
@ACuriousMind I don't think it is unusual, I just didn't know about it.
 
3:33 PM
ok
 
dammit, your edit makes my weak joke completely nonsensical :P
 
:-D
 
@skullpatrol what do you mean?
 
I was agreeing with you @JingleBells
 
@skullpatrol okay thx I guess :D
 
3:36 PM
:D
 
@ACuriousMind Are there interesting symmetries of diffeomorphisms that aren't linked to the identity?
ie if we have some one-parameter group of diffeomorphism that aren't connected to the identity, are any of them of interest
 
Who's excited about AI becoming smarter than us?
::me::
 
@Slereah Define "interesting" ;)
 
I have seen a lot of AI stuff and I'm not too excited
Hm
 
3:39 PM
^
 
mathematicians certainly care about them, the mapping class group measures them, essentially
 
Imagine I am in a room with only a vacuum (and obviously I am wearing some kind of spacesuit)
 
Are currents even defined for these?
Or do we always define currents for transformations connected to the identity
 
@JingleBells Unless you take that philosophy too far and you are specifically remembered for being unhappy
 
I suppose we probably do, since we do infinitesimal variations around the identity
 
3:40 PM
@Slereah u actually responded, I thought you've given up on me. I want friends again, ur really cool
 
I then turn on an intense laser with an energy matching the rest mass of two electrons. Then some time later, the detectors at the end of the room will register some electrons or positrons
 
@AaronStevens Lol yes
 
I wonder if that is the correct way to view pair production
 
@Slereah You can always reduce stuff in the non-identity components to stuff in the identity component
 
@JingleBells Have you seen the movie "whiplash"?
 
3:41 PM
@ACuriousMind IIRC all diffeomorphisms with compact supports can stem from vector fields
Which would certainly help
 
@AaronStevens about some drummer and Jeff Bezos as a rude asshole?
 
@JingleBells Lol you mean JK Simmons?
And yes
 
Fix any element of each of the components (pick the identity for the identity component). Then by applying this and its inverse you always translate into the identity component - your expansions "around the identity" become expansions around the point you picked
 
ye, the poor drummer will probably hear the screams in his face for the rest of his life
I haven't watched it, only parts
 
@JingleBells Ah ok. That philosophy is shared by the main character
 
3:45 PM
@AaronStevens lol I don't care about people knowing who I was. I care about the legacy I leave behind. I understand why you may think that now that I read my message above
But I support the character's view
unless of course, the people at the table are talking about a drunk, broke at 34 guy
 
@JingleBells Ah, like how most people probably don't know who specifically invented headphones, but they are everywhere?
 
@AaronStevens yes
 
@JingleBells Oh well. Still a fun movie. But I play drums so I am biased :P
 
coolio, I've always wanted to try real drums
bum chika bum bum tdum tsiii
Can u imagine dying drunk, broke at 34 and get a single family to talk about some drunken guy that died near their avenue lol.
 
@JingleBells Mission accomplished
 
3:50 PM
not sure if that's what the character imagined :D
 
The Schwinger effect is a predicted physical phenomenon whereby matter is created by a strong electric field. It is also referred to as the Sauter–Schwinger effect, Schwinger mechanism, or Schwinger pair production. It is a prediction of quantum electrodynamics (QED) in which electron-positron pairs are spontaneously created in the presence of an electric field, thereby causing the decay of the electric field. The effect was originally proposed by Fritz Sauter in 1931 and further important work was carried out by Werner Heisenberg and Hans Heinrich Euler in 1936, though it was not until 1951 when...
 
Yeah, probably not
 
ok so, this is still not observed yet
 
I hope one day u see some singing entrepreneur on TV and remember that guy from the hbar
u'll finally see my barbarian face
wtf am I talking about I need some sleep
 
My current intuition on relativistic quantum states:
1. There is some state, maybe the vacuum, which is in a way very complicated
2. Given the correct kind of interaction, particles and other phenomena, each obeying their corresponding symmetries (with the symmetry usually given by group theory) will pop up with some probability
 
4:01 PM
It's movie night tonight, any recommendations?
 
https://plato.stanford.edu/entries/quantum-field-theory/#Field
I think field interpretation, ontological structural realism and trope ontology all work for me as an interpretation of the ontology of quantum field theory
particles is just way too specific and limited
 
@JingleBells What sources of movies will you be using?
 
@AaronStevens umm Google search
ohh sources
 
I don't think you should post links to piracy sites here
But, if you are going that route, a movie that I recently saw that I thought was underrated was "Searching"
 
4:16 PM
Budget: 880,000 USD
Box office: 75.5 million USD
DAAAAAAAAAAMNNNNNNNNN
will watch
thx acuriusmind
acuriusmind is my favorite peep here
 
By underrated I mean I didn't hear much about it
 
that's not what underrated means :D
 
Literally the first I've heard of it, but I also don't really know much about recent movies in general.
 
Haha yeah but I didn't feel like thinking of other words
I think it deserved more hype
underhyped?
 
 
2 hours later…
6:30 PM
What I currently understand from my book on Nuclear Shell Model discussing the Electromagnetic fields is we make a transformation on the fields expressed as follows

$\mathbf{G}=\frac{1}{4 \pi c} \int[\mathbf{r} \times(\mathbf{E} \times \mathbf{H})] d V$

Then averaging over time $T>>1/ \omega$ we obtain for angular momentum per photon

$\frac{\mathbf{G}}{N}=\frac{\hbar \omega}{c} \frac{\int \mathbf{r} \times\left(\mathbf{E}^{*} \times \mathbf{H}+\mathbf{E} \times \mathbf{H}^{*}\right) d V}{\int\left(\mathbf{E}^{*} \mathbf{E}+\mathbf{H}^{*} \mathbf{H}\right) d V}$
I didn't understand how he introduced the last expression, anyway.
 
 
1 hour later…
7:53 PM
I just watched Searching. That is one of the best movies I've seen in my life.
No words...
 
8:19 PM
-12
Q: Additional reputation,badges for users who have weight

ABHIJIT BAGCHIIf a user is medically declared dead but rises like many persons, in other words very aged persons, do you consider their weight at the time of awarding reputations and badges? The reason is not only that The risen ones learn earlier and also through their cognition [they can share valuable info...

@Jenayah-zombies become normal persons when medicines are administered by Doctors, except it is observed they have converse beliefs and ideas. — ABHIJIT BAGCHI 3 hours ago
Um.
So, in case you see any zombies with reputation > 1 or any badges, maybe flag for mod attention. I would like to see that.
 

« first day (3446 days earlier)      last day (1477 days later) »