The h Bar

6:32 AM

@PM2Ring hi sir

7:07 AM

@PM2Ring have you read Everett's thesis? I haven't, but I gather he doesn't mention multiple universes at all. His approach is more like different observers choosing different origins for the Hilbert space i.e. it's the same single Hilbert space but seen from different perspectives.

@JohnRennie is position and momentum eigenstates do not belong to L2L2. Moreover the canonical state for a LPS has not Hilbert space norm.

@yuvrajsingh hi

Hi sir @JohnRennie

What are L2L2 and LPS?

@JohnRennie Lebesgue spaces of second degree

7:21 AM

I don't know what a Lebesgue space is, though some Googling suggests that Hilbert spaces are related to Lebesgue spaces. Are you asking if position and momentum eigenfunctions belong to a Hilbert space?

Yes sir, they are assume to be Hilbert vector space of state function @JohnRennie

But I do not why

As far as I know position and momentum eigenfunctions are in the Hilbert space but momentum eigenfunctions aren't normalisable so they aren't considered to be physical.

I'm not sure about position eigenfunctions.

OK I have one more question @JohnRennie

Yes?

@JohnRennie why not all LpLp spaces Hilbert spaces, and what you mean by "It is true that other Hilbert space (modeled over the position space R3) do exist, but they would typically rely on additional structure"

7:27 AM

I don't know enough about Lebesgue spaces to answer.

Difference between Hilbert space and projective Hilbert space @JohnRennie

Please sir

Q: Hilbert space vs. Projective Hilbert space

29

Hilbert space and rays: In a very general sense, we say that quantum states of a quantum mechanical system correspond to rays in the Hilbert space $\mathcal{H}$, such that for any $c∈ℂ$ the state $\psi$ and $c\psi$ map to the same ray and hence are taken as equivalent states. How should one in...

I guess this is what you are asking.

@ScientistSmithYT That's ok. I was very tired too. But there isn't really a lot more I can say about Kaluza-Klein theory anyway. The mathematics gets rather hard, and I can't see how to explain the details in a simple way. To appreciate it properly you really need to have a good understanding of standard general relativity.

7:42 AM

Thanks Sir @JohnRennie

@ScientistSmithYT And before you can understand general relativity you need to be very comfortable with special relativity, and with the mathematics of vector spaces and of fields. The Australian science fiction writer Greg Egan has written a series of excellent articles on special relativity, general relativity, and quantum mechanics called Foundations.

These are technical articles intended for the general reader. They do use a lot of mathematics, but nothing beyond high school algebra and simple calculus.

@JohnRennie No, I haven't read Everett's thesis either, but I know that you're correct: he doesn't mention multiple universes. I forget who added that stuff. I think Everett does describe a branching structure, though, and later writers chose to see those branches as separate worlds.

:waves @yuvrajsingh :)

@PM2Ring Wheeler presumably. Everett quit physics after his PhD and I think Wheeler picked up the idea and developed it.

That sounds right.

Many critics of MWI complain about the branching creating whole new universes, because that seems to defy conservation laws. David Deutsch gets around that by saying that nothing new is getting created. Instead, we start out with an infinite ensemble of identical worlds, and each branch simply splits the ensemble into subsets of the current ensemble, with each subset also consisting of infinite identical worlds. That seems neater to me.

7:59 AM

To actually see the world we require to do measurement In practice this is impossible to realize because the observer is a macroscopic object itself and it will decohere very faster

What Everett theory said @JohnRennie @PM2Ring am I right sir

@yuvrajsingh I don't know the theory well enough to comment. Reading Everett's thesis is on my list of things to do, but not at the top of the list.

@JohnRennie I read this from D. Deutsch, Int. J. Theor. Phys. 24, 1 (1985)

@JohnRennie I have two three quick question s

@yuvrajsingh The concept of decoherence is not in the original MWI of Everett or Wheeler. It's a relatively modern invention, and it can be applied to various interpretations.

@PM2Ring it is

I can send you papers

@JohnRennie is it true that Polarization describes the orientation of a wave, not its amplitude.

How

@yuvrajsingh an EM wave is an oscillating electric field, and an electric field is a vector so it points in a specific direction.

8:13 AM

After passing through a polarizer what changes it has @JohnRennie

In a linearly polarised wave the polarisation just describes the direction of the electric field associated with the wave.

The way to think about a polariser is that the incident wave makes the electrons in the polariser oscillate, and those oscillating electrons then emit a new light wave on the other side of the polariser.

But in a polariser the electrons are constrained to oscillate in one direction, so the wave they emit is polarised in that direction.

Typically polarisers have long chain molecules with the electrons delocalised over the chain. So electrons can oscillate along the chain but not sideways to it. That's why the oscillation is restricted to one direction.

Ok

Q: How can an observation, an empirical measurement be considered to be none mainstream theory?

@yuvrajsingh If the incoming light is already polarised in the direction of the molecules then it makes the electrons in the molecules oscillate along the chain very effectively and you get a polarised wave emitted that is very close to the original intensity.

If the incoming light is polarised normal to the direction of the molecules then it can't make the electrons in the molecules oscillate at all, so no new wave is emitted and the polariser blocks the incoming light.

At angles in between some of the energy in the incident wave goes into making the electrons oscillate so some of the energy goes into the new wave, but not all.

That's why the amplitude of the transmitted wave varies as the cosine of the angle between the incident light direction and the polariser direction.

Physics Meta

8:45 AM

0

I desire to contribute for the community. I want to work within the community guidelines while contributing original perspectives. Please note that "original perspective" does not automatically equate as "non-mainstream". I'm attempting to walk this fine line, and the challenge for your moderator...

discussion

9:01 AM

today is the 108th anniversary of our nation's birth

@CaptainBohemian It's not the 14th of July yet

And it's way more than 108!

@Slereah Is 14th of July France's birthday?

It is the national holiday anyway

Not sure what the actual birth date is

Depend which one you consider, I suppose

Apparently august 10 is the official date of the fall of the monarchy

although it didn't fall forever, so make of that what you will

@CaptainBohemian See en.wikipedia.org/wiki/Bastille_Day

to celebrate our national birthday, we are on holidays from today until October 13.

9:11 AM

1911 – The day after a bomb explodes prematurely, the Wuchang Uprising begins against the Chinese monarchy.

This event?

I forget there was a bomb exploding prematurely before Wuchang Uprising. Xinhai Revolution is event leading to our nation's birth.

but afterwards our nation lost a great part of its territory.

I hope that didn't happen.

it's a civil war, but I really can distinguish our nationals from people from People Reublic of China as long as we speak.

due to the civil war, the people from each of the two Chinas of different sovereignties require visa to enter the other's territory; in the past, it even required flight transit. It leads to a lot of inconvenience.

Q: Could Einstein's theory of Relativity have overlooked a relationship between time and force?

9:45 AM

now people from each of the two Chinas of different sovereignties can fly to the other's territory directly, but visa is still required, even just for flight transit for going to other countries

perhaps I should say today is the 107th anniversary of our nation's birth; I am not quite sure the usage of "anniversary".

Secret

10:42 AM

-4

Does Time dilation effect correspond to a property of the world that is suited to the term's "modulated force" or "force dilation" It seems a simple truth. A modulation in the rate of force-driven systems, represents a modulated value of that system's internal forces. If you take two identical f...

forces relativity time-dilation

I don't think one can experimentally establish a causal relationship between time dilation and change in force due to different reference frames as more fundamental.

You can write time dilation in terms of changes in forces in different reference frames, or vice versa, there is nothing really new introduced here

11:11 AM

What does high radiation mean? Like, when an atomic bomb booms, people say there is radiation. What does that mean? Why for example there is high radiation in Chernobyl and what exactly is that "radiation"?

Loong

@NovaliumCompany Doing that thing again?

@NovaliumCompany Downvoting due to lack of prior research, and close voting as Too Broad. See en.wikipedia.org/wiki/Radioactive_decay and come back with a more specific question.

Speaking of broad questions about nuclear physics, should we close physics.stackexchange.com/q/507214/123208 as too broad, or wait for the OP to edit it to something more focused? Or is there a good dupe target for them?

@Loong SuUuUu

@PM2Ring U feel like a teacher writing me a D on the test

I know I can google, I thought of that, but since I'm an important prince, I will have my answers personally written, otherwise why would I be paying you 500$ a month.

11:44 AM

As I said in the Python room a few months ago:

Imagine that you won a competition, and the prize is a free session with a think-tank who normally charge $1000 per hour. Don't waste that prize!

@NovaliumCompany That was the intention. ;) I'm happy to have a conversation about radiation, but you do need to do some groundwork yourself. You can't expect the people here to give you a complete course from the ground up, in whatever topic currently takes your fancy.

Especially since you've made it quite clear that you aren't interested in formal higher education.

If you want to teach yourself these things, then you have to put in some effort, and not expect people to spoon-feed you like a little child.

Ryan Unger

12:23 PM

@Slereah math.princeton.edu/events/…

@RyanUnger I'm afraid I won't be able to attend

bit of a commute

Ryan Unger

12:47 PM

@Slereah maybe if they still had the concorde

A: An apology to our community, and next steps

Did it disappear on 9/11

Sir Cumference

1:30 PM

479

Thank you for these positive steps. We’ll be reaching out to her directly to apologize for the lack of process, privacy, and to discuss next steps. We’ll keep those discussions completely private unless we both agree to share any of it with the community. I will update this answer when SE c...

Sigh come on SE

1:53 PM

meta.stackexchange.com/questions/334878/… Time for everyone's favourite SE game show "Did we do that on purpose?"

2:05 PM

physics.stackexchange.com/questions/507346/… -_- tries to call something nonsense because he doesn't understand it, then says "Useful to be aware of our flaws". The irony if it is bothering me

I am not getting what irritate you @j Mac can you explain why you making the issue larger, this is the short question, my answer is according to that,

I already said I accept and learn, but you think it is irony, I do not want to sound disrespect.

@JMac Also, air molecules aren't still, but I guess for the OP's question we don't really need to zoom in to that level of magnification.

@PM2Ring I'm pretty sure mentioning that would be the opposite of clearing things up :P

Agreed.

Q: Why does concave mirror simultaneously form 2 images?

@yuvrajsingh Are you referencing this comment? physics.stackexchange.com/questions/507001/… Basically, there are already 2 very clear answers (posted days earlier) that seem to cover everything in your answer, and your wording is quite unclear. Posting late answers that don't add anything new isn't very helpful.

It doesn't help my opinion that you posted and deleted two similar quality answers on that same question in the last few days.

Physics freak

2:26 PM

0

So in an experiment to find focal length of a concave mirror first we had to estimate its rough focal length. I kept an object at point which was beyond the focus in front of the mirror and got its real image on the screen. But as soon as I removed the screen I coould even see an inverted image o...

optics reflection image-processing method-of-images

Someone please answer this question

3:44 PM

@PM2Ring I know I know, I'm just annoying on purpose sometimes. Sorry.

3:57 PM

@NovaliumCompany Ok. Just try to do it less. :)

@PM2Ring I will :-)

I'll be watching... :D

4:28 PM

Instead of school bell, they play us music. Currently, it's Lalala. The previous one was Gucci Flip-Flops

@NovaliumCompany the funeral march? :-)

Q: In SR length contraction, does matter flatten because the space around it flattens or does the structure of the matter flatten?

5:10 PM

Reassure me people. Was I wrong to close this as a duplicate?

-1

Most people believe length contraction is a real spatial phenomenon and if so there's nothing to contract in empty space and since matter contains mostly empty space then it is only the structure of matter that is physically contracting. So now, if a mirror is mounted on a 45 degree plank comin...

special-relativity relativity