The h Bar

8:41 AM

imgur.com/gallery/RmIIc

sheep dynamics

8:57 AM

hallo

wats dat @Slereah

i cannot access the link

why not

ahh....my wifi provider does that...:|

10:02 AM

Having the ricci scalar exponentially growing much dramatically slower does not necessary mean one will not be crushed.

How does the limit of being crushed is reflected in the results of that article?

10:23 AM

well everything can be crushed under some pressure

The point is that it's not divergent, I guess?

I dunno

hmmm... I see...

Can anyone help me out with counting the number of thermodynamic degrees of freedom for a nuclei?

They have 3 translational, but do they also have 3 rotational degrees of freedom? Does rotating a nucleus count?

is your system at a scale where you can resolve individual protons and nuetrons, or it is just an atom?

considering just an atom?

O in that case a single atom has no vibrations nor rotational degrees of freedom

10:32 AM

i dunno but if it was 'just an atom' doesnt that automatically mean it has protons and neutrons in it

Why doesn't it have rotational degrees of freedom though? Like if I rotate it, it changes and stuff

(assuming internal degrees of freedom of the nucleons are unimportant, which is true in most chemistry)

But say that I had like an atom idk like helium 4 or something

in my mind its 2 protons 2 neutrons at like the corner of a square or something

and i can definitely spin that in my mind

like I can sort of understand why spinning a proton doesn't do anything (so doesn't count as a degree of freedom) but if I have a helium surely I can spin it

Because if you rotate an atom (which is described by a spherical probability cloud of electrons (orbitals) with a nucleus that is basically point like at this scale wrt atom), you don't change the atom in a way that can be physically detected

a 2 handled klein bottle is a torus(shhh! its a secret!)

it's kinda like rotating a featureless sphere, you get the same thing no matter how you rotate it

10:35 AM

why can't I physically detect the change? I mean if I have a square and I rotate it, surely I can detect it

featureless sphere I can totally understand

thus you cannot really tell whether you have rotated it at all

but a helium 4 isn't even spherically symmetrical

if I spin it then surely its definitely changing over time

and I could probably detect I dunno some EM waves emitted by the accelerating protons right? Something or other?

whereas an odd number handled klein bottle still remains a klein bottle...

hmm, it turns out it is a bit more complicated in the fuller picture
http://physics.stackexchange.com/questions/168943/in-counting-degrees-of-freedom-of-a-linear-molecule-why-is-rotation-about-the-a

For most chemistry at atmospheric conditions, if we based on the physical arguments here in this PSE answer, the rotation about a symmetric configuration contributes a lot less compared to rotations that are not as symmetric, thus it is effectively cause negligible change in configuration

An atom is pretty much spherically symmetric, thus using the logic here, you probably end up ionising it b…

thanks for the help!

11:01 AM

Note to self: To be checked
The dynamics of an electron moving relative to a muon such that its energy momentum is identical to that of the muon

Check the criteria for the coherance of their quantum states in relativistic conditions, and if coherance is valid, rationale the naive observation that the two particles interfere in the muon's frame of reference bt not in the electron's frame of reference

Rajesh Dachiraju

11:48 AM

For suppose, sssuming this new type of Fourier series : mathoverflow.net/q/208867/14414 is correct, can you think of some interesting things that can be said? My request, if you have some absolutely free time. This is only to help my mathematical thinking. Also anything to do with Physics?

12:13 PM

Look, Penrose says that → is a state that is equal to ↑ + ↓. Why not → = ↑ - ↓? Why is latter equal to ←?

12:24 PM

Isn't up - down the spin 0 part

@Slereah I do not get you. We have up + down and up - down. Why first is right and latter is left? What direction would be down - up?

Oh that's an EPR thing

I dunno

Check the details of the experiment?

Possibly related
http://www.feynmanlectures.caltech.edu/III_09.html

The up and down kinda reminds me of the amonia two state system here, where they form the hilbert basis of the system in question

since these are orthogonal, you canalways define a new pair of orthogonal states that is a linear combination of the old ones

In this case, I am guessing the left and right states are the new pair of base states that is used to describe the experiment

However what it graphically means I have no idea, as I still have trouble picturing something like

$$\frac{1}{\sqrt{2}}(\alpha(1)\beta(2)-\beta(1)\alpha(2))$$

where $\alpha$ and $\beta$ are spin orbitals (representing whether an electron is spin up or spin down respectively)

12:46 PM

Yes, Feynman does something similar though I do not understand what. Actually, I have seen some bases defined somewhat arbitratily reading this paper which also pretends to be the simplest exposition of Bell's paradox arxiv.org/pdf/1212.5214v2.pdf. They define some basis for properties A,B and C. I wondered why that basis and, moreover, what do they mean to say by |Ф+> = a_0 (b_0 + √3 b_1) + a_1(√3 b_0 - b_1 ) / 2√2.

are each of the abc, states?

@Secret They describe in the beginning that a,b and c are binary states. Likewise A stands for golden/copper, B for shiny/dull and etc.

That is, they are properties, or incomplete states.

So if these are states (and not coefficients in a linear combination), then I am guessing that juxapositioning two letters together is doing a tensor product

Thus since $|\Psi\rangle$ is a sum of two tensor products, it might be an entangled state, but I am not really sure because I am not good at hilbert space tensor products

1:02 PM

@Secret Yes, I have the same feeling. But, I would like anybody could explain me what does it mean. The material seems to be something basic for those in quantum computation.

Entanglement is important in quantum computing researches, but other than the two states are correlated no matter how far they are separated, I am not sure about the details

You might be able to catch on Acuriousmind, Yuggib, Danielsank about 2 hours later, they are the quantum guys in this chat

2:07 PM

@Secret Yes, they seem to drink the quantum Kool Aid

user116211

@0celo7: Watched Deadpool?

Stack Exchange Science Fiction & Fantasy Blog: Deadpool Review

@user36790 No.

user116211

;/

user116211

jst bought tickets....

user116211

majorstackings on February 12, 2016

I went to the 9:50 screening of Deadpool last night. I managed to get the center seat in the back row. The theater was about 1/4 full, and even then there was a buzz in the air.

Deadpool, Marvel’s latest comic book character to receive the R-rated movie treatment due to violence and subject matter, drew genre appropriate previews. I couldn’t even absorb the body count before the actual film even started. If you like “shoot -em up bang! bang!” movies, this summer might be your best summer yet.

Deadpool can be a bit of a smart-ass. …

2:41 PM

@ACuriousMind If I can't use $\mathrm{i}$ for $\sqrt{-1}$, should I use $\mathrm{j}$?

why you can't use $i$?

use $\iota$, or $\imath$

you can use $j$ only for quaternions...

;-P

3:08 PM

@yuggib Because i is the current

any decision on the unbased/baseless issue? @Danu

@skillpatrol I went with unbased.

Your graph is completely irrelevant because, as I said, the word "unbased" has a different meaning in everyday life.

@0celo7 then $j$ is the current density

just trying to help

@skillpatrol Thanks anyways for your attempt! :)

3:17 PM

@yuggib but i is the current

i is imaginary :P

i is the current

Huh

That doesn't really work

as long as you're consistent

@yuggib Are those two different?

Q: Draw the way the longitudinal wave spreads

3:41 PM

@0celo7 yep, \imath and \iota

Physics Meta

-1

Draw the way longitudinal wave spreads. I know how to draw how the transverse wave is spread https://picasaweb.google.com/102071315138065861533/February162016#6251906804992968450 COuld you do the same thing for the longitudinal one?

support

s.harp

I have a question which is maybe too stupid for the main website. If in a classical system we look at the grand canonical ensemble we have a probability measure on $\sum_{n=0}^\infty \Lambda^n$ and the measure reduces on $\Lambda^n$ to:

$$\frac{z^n}{n!} \exp(-\beta U(x)_n) dx_1 .. dx_m$$

Where $dx_1 .. dx_n$ is the product of the euclidean measure on $\Lambda$ and $U(x)_n$ the energy function for an $n$-particle system.

If $Z$ is the partition function, then the $m$-point correlation function $\rho(x)_m$ is given by

My question is why in the last expression we have a $1/n!$ and not a $1/n! 1/m!$

@yuggib visually

s.harp

Oops I have forgotten many terms

it appears I cannot edit my message

brainst

3:59 PM

physics.stackexchange.com/questions/235811/… Can anyone please consider answering this question? It seems to be went unnoticed . I posted it 3 days ago! Thank You!

@0celo7 apparently, yes

Q: An ambiguous question on 2 balls

4:10 PM

-1

Two balls A & B are at rest at the bottom of a hill.Sometime after ball A is given a kick up the hill, ball B is also given a kick up the hill. When ball B is going up the hill, ball A is already coming downhill. When they pass by each other what properties will they share in common? The question...

kinematics relative-motion

Best question title.

user116211

o.O

user116211

@ACuriousMind: Just completed three chapters of Reif.

@user36790 Uh, okay? Why do I need that information?

user116211

@ACuriousMind: Can you tell why the work is defined as $\partial W= \sum P dE$?

Q: Will the Polarity of magnet be reversed or will it rotate? Will the ferromagnet melt in varying strong magnetic field Or will the domain strct collaps

@0celo7 I'm not the lord of typography, and you need to learn to just choose something when presented with decisions that will have no real consequence.

user116211

4:14 PM

2

According to the domain theory, Ferromagnetic substance when kept in the external strong magnetic field, it undergoes magnetisation by Rotation and becomes a permanent magnet thereby even after removing the external magnetic field. I got several questions regarding it. I'll list them one by one: ...

electromagnetism magnetic-fields magnetic-moment

@user36790 What is the sum over? What is the $\partial$ supposed to mean? What is $\mathrm{d}E$? I cannot magically divine what your symbols mean.

user116211

@brainst: Try to shorten your title and consolidate it in few words and not words like collaps, strct

user116211

@ACuriousMind: Okay, let me elaborate:

user116211

$P$ is the probability distribution and $E$ is the energy of the state.

FenderLesPaul

@GPhys quiet so far!

user116211

4:19 PM

I could understand heat $Q$ defined as $\partial Q= \sum E_r dP_r$; as when heat is transferred, no external parameter gets changed; only the probability changes.

@ACuriousMind It will have real consequences

My OCD is real

@user36790 If you agree that internal energy is $U = EP$, then this just follows from using the product rule on $\mathrm{d}U = \mathrm{d}(EP)$ and calling one term "heat" (the one with $\mathrm{d}P$) and the other "work" (the one with $\mathrm{d}E$).

user116211

@ACuriousMind got it.

Is it really a good idea to have a ligo tag?

user116211

@Danu quite localised tag.

4:31 PM

@Danu Why does it matter?

@0celo7 Because site management matters (to me).

That includes removing useless/superfluous/bad tags

@Danu We also have lhc, so why not? Asking about a specific experimental setup is certainly on-topic, and there are more than 10 questions for which it can be rightfully used. What do you not like about it?

@ACuriousMind I think it may be too localized.

@Danu Meaning?

That it will never be used again in about 2 weeks

4:32 PM

So?

user116211

@ACuriousMind Most of the questions ultimately concerns of gravitational waves.....

I don't see the issue. (Not trolling.)

@Danu Uh, why? We have had questions on LIGO long before the recent flood, and there will certainly be some in the future.

The questions also do NOT explicitly ask about thing specific to LIGO (except for ~10 or so that came out in the past few days)

@ACuriousMind Less that 5 about the actual LIGO experiment (I am going through all gravitational-waves questions as per Qmech.'s request).

By that, I mean less than 5 before the big announcement.

user116211

@Danu That's what I'm saying but some like asking about the arrangement of the arms of LIGO came too.

4:34 PM

I think almost all questions apply equally well to [any other grav. waves experiment]

@user36790 Sure, there are a few. I'm guessing in total less than 20.

user116211

And that's why it is too localised.

user116211

There are many interferometers other than LIGO; we can't have all them tag as LIGO ;/

@Danu We're not limited in the number of tags on the site. Unless those questions tend to have five tags, and you think there could be a more useful one than ligo being used, I don't see any harm done, and people who want questions specifically about LIGO can use it to search for them

experimental-physics gravitational-waves interferometry ligo

Even something like this doesn't really ask about anything other interferometry-based grav. waves experiments wouldn't do:

8

Q: Can LIGO measure anything?

LIGO, Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. The device measures the phase shift laser beams. If I understand this well, the measurement assumes that a suitable gravitational wave reduces and prolong...

@ACuriousMind I see it just as unnecessary; I agree there is no big harm done.

user116211

Harmless but Unnecessary.

4:38 PM

And...well, the misuse of the tag is not the tag's fault - it's pretty clear that it should be used for questions about LIGO. That careless people tend to use any tag that looks sort-of-kind-of-related to their question is an issue not specific to the tag

@ACuriousMind No, but being more precise about applying it means there will be only about 10 questions tagged with it, most of which don't actually talk about the stuff people want to find when they search for LIGO stuff, namely generic grav. wave detection stuff (I'm fully convinced that this is true, though I have no evidence).

user116211

@ACuriousMind All are not careless people, BTW.

So it's either (1) a misnomer tag that somehow manages to help people find useful information (2) an accurate, useless tag.

@user36790 I did not say that everyone is misusing the tag. Read my sentence again.

4:41 PM

I don't like either of those options very much, though the first seems more agreeable (but less so than just deleting the tag, IMO).

What do you think @JohnRennie?

@Danu If people searching for LIGO actually want questions about gravitational waves, why are they not using gravitational-waves?

@ACuriousMind Because laypeople* is why :P

user116211

People knows....

@Danu So...you're saying we should change the tagging because people who are explicitly not the intended audience of the site misuse it?

Those damn laypeople

4:45 PM

@ACuriousMind Maybe.

What's the bar for not being a layperson

Knowing more analysis than @0celo7

I was going to go with "being able to solve quadratic equations", but that works, too.

GPhys

@FenderLesPaul I'm hoping NYU sends out official today

Jesus Christ

user116211

4:48 PM

Laypeople are those who, after reading Hawking, Green and Kaku, think they have understood everything.

Q: How does LIGO account for curvature of Earth?

This is an example of an actual LIGO question:

3

Using an earth curvature calculator, I found that at a distance of 4 km (the length of LIGO's arms), more 1.26 m is hidden by the horizon. When constructing LIGO, did they account for the curvature of the Earth to allow the beam to travel in a straight line?

experimental-physics spacetime curvature gravitational-waves ligo

I bet the average reader of Hawking, etc. can solve a quadratic equation

Qmechanic

@Danu : I was thinking the same. Maybe it is good to keep the ligo tag temporarily for now while it is popular, and sometime in the future, when new detectors are turned on, replace it with e.g. grav-wave-detectors.

user116211

@Qmechanic Far better.

@Qmechanic Can't we do that now, and make ligo a synonym?

Qmechanic

4:56 PM

@Danu : Yes, eventually, but for the democratic process, please vote.

@Qmechanic Insufficient rep (on ligo questions) :(

user116211

Me too ;/