The h Bar

Slereah

08:44

morning

ACuriousMind

::looks outside:: ah, yes, it would appear to be morning

Slereah

what is even time, anyway

Find out in my upcoming paper

One hard part of defining measurements properly for GR is showing that a proper time clock exists, at least within some bounds

Since everything is affected by gravity it's hard to show

How do you even know what frequency an atom will emit if the Dirac equation depends on the frame field???

B. Brekke

09:43

When summing over Feynman diagrams, I sometimes find the dimensions strange, because the larger diagrams have more internal variables to integrate over. So I am adding diagrams D1 dx1 and D2 dx1dx2dx3 and it looks a bit strange to me

ACuriousMind

Since they represent probability amplitudes, they should be dimension-less.

But I see that it can get confusing because you often use them to compute definitely dimensionful cross sections

B. Brekke

I guess the internal variables x1, x2, x3, which may be momentum or position (or maybe time?) are not dimensionless?

Is D1 dimensionless or integral(D1 dx1)?

ACuriousMind

No, but remember that we usually use natural units so that there are "invisible" factors of $\hbar$ and $c$ everywhere

E.g. there's a power of $\hbar$ for every loop order

B. Brekke

Ah, that is right, I forgot about those

user434058

Should answers to HW questions also be punished with downvotes?

user434058

09:56

Or for that matter, answers to any off topic question?

John Rennie

@FakeMod the problem is that many answers to homework questions are answers in good faith from people who don't know our homework policy.

ACuriousMind

@FakeMod Full answers to HW questions should be flagged for deletion via custom mod flag. How you vote on them is - as with all posts - your own choice.

John Rennie

I feel uneasy downvoting someone who meant well, and it also risks putting off new users.

But as ACM says you can flag the answer for deletion. That's all I usually do.

PM 2Ring

10:48

@FakeMod I'm not comfortable with downvoting answers that are technically correct because that may confuse readers into thinking the answer is incorrect.

Student404Mus

@ZeroTheHero Could you tell me if the first answer is true?
https://physics.stackexchange.com/questions/540489/physical-interpretation-of-triplet-state

Novalium Company

I've uploaded files on GitHub that I want no one to be able to access except me. I've created a private repository with no collaborators added. Is that the option to make it completely private? (e.g I don't want anyone to steal or look at my code)

PM 2Ring

@ACuriousMind FWIW, in the Python room, we do not allow people to ask for answers to their fresh questions. That's primarily to avoid having parallel discussions on the main site & chat. We tell them they need to wait 2 days, when their question becomes eligible for a bounty. However, we do allow people to ask for "meta" assistance with their question, to help them ensure that their question is up to community expectations.

@NovaliumCompany That sounds correct to me, but I've never used that feature so I'm not certain. (I mostly just post Gists, and most of those are public).

Novalium Company

@PM2Ring Mkay, thanks

ACuriousMind

11:05

"I don't want anyone to steal my code" ::weeps in open source::

Novalium Company

11:15

I need help with a History question:
The Japanese foreign market is mainly aimed at America, the second most important market is:
Bulgaria
China
Korea
SSR

Pretty sure it's not the first one

I tried Googling.

plez

I suppose the question is concerned with 1950s (post-WWII) stuff cuz that's what we're studying

The question is so general that it kills my brain cells

ACuriousMind

This question suspiciously sounds like a reading comprehension question - one to which the answer is trivial if you've read/understood the reading material it presupposes...

Why you think random physicists on the internet know Japanese post-WWII economics is beyond me, though :P

John Rennie

@NovaliumCompany Google, Google :-)

> The top export destinations of Japan are China ($136B), the United States ($125B), South Korea ($54.2B), Other Asia ($32.9B) and Hong Kong ($32.1B).

PM 2Ring

@ACuriousMind I think @NovaliumCompany ought to read The Cathedral and the Bazaar

John Rennie

Hmm, the MathJax addon has made a comprehensive mess of that post ...

PM 2Ring

Also see en.wikipedia.org/wiki/The_Cathedral_and_the_Bazaar

Novalium Company

11:28

@ACuriousMind Cuz you're all all-knowing. If I'm an ant, you're zebras compared to me intellectually.

John Rennie

Intellectually I'm an ant but I have ambitions to be a cockroach.

Novalium Company

@JohnRennie Welp, I guess they should teach us to Google properly, cuz in 21st century it proves much more useful than remembering random seemingly useless facts.

John Rennie

I must admit I rely more on Google than memory for many things these days.

Novalium Company

They should teach us to think, not to memorize and apply formulas. My school has no idea what creativity is, what learning from failure is... it's such a disgusting system, glad it's over soon (for me)

The world moves forward but schools stay in 20th century

John Rennie

A little while ago I read a touching novel where the main character has Alzheimers but manages to keep going by continually Googling for all the stuff she has forgotten due to the disease. How well this would work in real life I'm not sure.

Novalium Company

11:33

I have no problem with memorizing. I have a problem with being forced to memorize facts incredibly uninteresting to me.

How do they expect me to remember things I have zero curiosity about and I find completely useless.

ACuriousMind

@JohnRennie This would need the disease to only make you forget technical knowledge. You can't google that the face in front of you is your child, you can't google if you think it's the '50s and you don't know what the shiny rectangle in your hand is...

John Rennie

I give up - anyone else want to try

@ACuriousMind well it was just a novel My Real Children.

ACuriousMind

@NovaliumCompany Playing devil's advocate: It's not about the facts themselves. It's about the skill of reading a text, extracting and retaining information from it and being able to answer such reading comprehension questions.

This skill doesn't really change with the advent of Google - sure, you can Google plenty of facts. You likely could also just have read the corresponding section in your text book. In both cases what's being tested is not your ability to memorize the fact but your ability to extract it from a larger source of information.

PM 2Ring

Here's one of my favourite songs about politics:

Cream - Politician

►

Novalium Company

@ACuriousMind I can still read a text, extract and retain information and answer comprehension questions about something that I actually care about. Something that I'm curious about and I'm eager to learn. In my opinion, learning should be a choice. It should be a journey each person travels through, in their own way, in their own time. I understand that that would be catastrophic for the world and that most people are not particularly curious or eager to learn but still.

I agree that the educational system works for the whole and is, for now, the most optimal system the world has for educating the world but for me personally, it's incredibly dull. What am I even talking about, we'll probably be downloading info with a cable to our brains in a few decades

PM 2Ring

11:53

@JohnRennie Not me, that OP isn't going to budge. I'm very tempted to VTC as non-mainstream...

skullpatrol

@NovaliumCompany do any of these tables make sense to you?

tpg2114

Journals must be having issues finding reviewers... I've reviewed 15 papers since November... I think I need to start saying no

PM 2Ring

12:09

The author of this answer just edited it. In the table at the end of the answer there are blue rectangles after each planet name. At least, that's what they look like in the Samsung browser (which I think is a fork of the Chrome Android browser). Those rectangles are links to Wolfram Alpha. What are those rectangles supposed to look like? I had a brief look at the raw source of the post but it uses a lot of LaTeX that I'm not familiar with.

ACuriousMind

@PM2Ring It's a handheld calculator icon

PM 2Ring

@ACuriousMind Thanks

Sir Cumference

ugh

Semiclassical

12:47

trying to decide if the following is in the spirit of "adiabatic invariance"

Suppose you have a rotating body, with initial angular velocity $\omega_0$, subject to an angular acceleration $\alpha<0$. I track a point on that body which is at a distance $R$ from the axis of rotation.

If the angular acceleration is zero, then this is uniform circular motion and the total acceleration is just the centripetal acceleration: $|\vec{a}|=\omega^2 R$

This no longer holds if the angular acceleration is nonzero. In that case, we have tangential acceleration $\alpha R$ and thus $|\vec{a}|=\sqrt{(\omega^2 R)+(\alpha R)^2}$ where $\omega=\omega_0+\alpha t$

However, if $\alpha$ is small, then the tangential acceleration may be neglected and thus $|\vec{a}|\approx \omega^2 R$ once more. In that case, one has $a\approx v^2/r$ despite the lack of uniform circular motion (i.e., despite the fact that $\omega$ is not constant).

That vaguely reminds me of the concept of an adiabatic invariant but I can't tell if I'm just making it more complicated than it needs be.

(should have been $|\vec{a}|=\sqrt{(\omega^2 R)^2+(\alpha R)^2}$, oops)

user434058

13:12

Should I write something like "Hope this helps!" at the end of my answer? (Bob D always does this, so I am wondering whether it might be a good practice or a useless one)

Student404Mus

@Semiclassical Could you comment about whether the first answer to this question is true?
https://physics.stackexchange.com/questions/540489/physical-interpretation-of-triplet-state/540566#540566

Slereah

That Olbers paradox is driving me mad

ACuriousMind

@FakeMod We're not draconian about it, but in general we discourage that sort of fluff

Slereah

I'm not sure I can solve it short of using the actual value of the convolution of distributions

Semiclassical

which one is "first"? (active/oldest/votes)

Slereah

13:15

which is super annoying

Semiclassical

(better to reference the author of the post)

Slereah

@ACuriousMind How very German

Should we sign off "Now get back to work!"

ACuriousMind

It would at least be better than the flood of strangely intrusive remarks about other people's health and mental well-being that are currently en vogue in the emails I'm getting :P

Student404Mus

@Semiclassical my2ct 's answer

user434058

@ACuriousMind Got it!

ACuriousMind

13:19

@Slereah That's nothing. One of my colleagues always ends his presentations with a slide that says (translated) "If it's all getting too much for you, just work faster."

I haven't yet figured out whether this is meant to be humorous or not :P

Slereah

Well the Germans are famed for their sense of humor

Student404Mus

"It is not correct to interpret that state as describing opposite spins."

Semiclassical

@Student404Mus I take their point to be as such: Suppose you measure the spin z-components $S_{1z},S_{2z}$ for a two-electron state

If you have the singlet state, then you know for sure that $S_{1z}=-S_{2z}$

Student404Mus

huh,

Semiclassical

that is, if one of the measurements comes out as spin-up along a given axis, then the other will give spin-down

the same cannot be said of one of the triplet states.

That requires a caveat, though.

It is the case that spin-z measurements on the L=1, M=0 state will give opposite results for the two particles. That's what it means to have M=0

Student404Mus

13:23

The first part of what you said is what so far I know.

Semiclassical

However, that only works for the z-axis. You needn't have $S_{1x}=S_{2x}$, for instance

In other words: Each of the two M=0 states can be said to have opposite z-components. But, for the singlet state (L=0, M=0), this is also true for the x- and y-components. As such, you can say "spins are opposite" without any real issue.

With the L=1, M=0 state, by contrast, you can't make this further statement. So i that case you can only say that the two particles have opposite z-components of spin.

ACuriousMind

@Semiclassical That strikes me as a dubious ontological claim. You can say that the two particles have opposite z-components of spin after their z-spin has been measured. Prior to measurement, this state has no definite z-components for the individual particles!

Semiclassical

ehhhh. you have $L_z|L=1,M=0\rangle =0$

bolbteppa

"As more distant stars are revealed in this animation depicting an infinite, homogeneous and static universe, they fill the gaps between closer stars. Olbers's paradox argues that as the night sky is dark, at least one of these three assumptions about the nature of the universe must be false."

Semiclassical

and therefore $L_{1z}|L=1,M=0\rangle = - L_{2z}|L=1,M=0\rangle$

I guess the less objectionable phrasing is that, if you measure the total z-component, then this quantity has a definite value for the L=1, M=0 state. From that, you infer that the individual z-components will come out as opposite once measured.

ACuriousMind

13:33

@Semiclassical Sure, but since this is an entangled state when tracing out the other particle you get a mixed state, not an eigenstate of $L_{iz}$. I think this is different from the situation where you do have definite pure states for the component particles, and the way we talk about the state should reflect that

Yes, this makes for awkward phrasing, but the situation is simply rather unclassical and awkward.

Semiclassical

Fair enough. This point of phrasing is something I've gotten into trouble with in the past

in particular, there's a footnote to the long philosophy preprint I contributed to:

"This response to Wayne Myrvold’s request for clarification (see the preceding note) was inspired by a footnote in _Wahrscheinlichkeitstheoretischer Aufbau_ (von Neumann, 1927b, p. 249, note 9). In this footnote, von Neumann points out that the Hamiltonian for the harmonic oscillator $\hat{H}$ has a discrete spectrum even
though it is the sum of two terms, $\hat{p}^2/2m$ and $\alpha \hat{q}^2$, that both have a continuous spectrum. The value of $\hat{H}$ will not be the sum of the values of $\hat{p}^2/2m$ and $\alpha \hat{q}^2$ even though the expectation value $\hat{H}$ will be the sum of …

bolbteppa

2

Q: Does Olber's paradox imply a bright sky or a divergent one

Doing Olber's paradox with specific systems is simple enough. Take stars on a grid of length $\ell$, then the total luminosity is just \begin{equation} L = \sum_{i,j,k} \frac{L_0}{4\pi\ell^2(i^2+j^2+k^2)} \end{equation} which is enough to show divergent. I have attempted to do it for a more rea...

'if you drop all the mathematical language, the result is obvious' haha

Semiclassical

That's perhaps not quite the same issue, but it's a reminder of how the sum of two operators can have a quite different status (for a given quantum state) than either operator by itself.

@ACuriousMind Of course, by that token, the phrase "the spins are opposite" is questionable even for a singlet state

simply by virtue of any spin components only being well-defined after the measurement

ACuriousMind

@Semiclassical Yes, I'd question that phrasing for the singlet, too

Semiclassical

That's fair.

For the singlet, one can at least say the following: If we measure $S_{1z}$, then we can predict the result of measuring $S_{2z}$ with certainty

ACuriousMind

13:43

That's what we call entanglement, yes ;)

(well, not exactly, but it's a consequence of this particular shape of entangled state)

ZeroTheHero

@Student404Mus which one is first?

Semiclassical

28 mins ago, by Semiclassical

which one is "first"? (active/oldest/votes)

lol

Student404Mus

:)

I asked @Semiclassical the same question

Semiclassical

I'd argue that the phrase "the spins are opposite" can be interpreted sensibly for a singlet state, even if the phrasing itself is misleading

Student404Mus

@ZeroTheHero We are discussing my2cts 's answer

Semiclassical

13:46

whereas no such interpretation is possible for L=1, M=0 state

ZeroTheHero

as pointed out by my2cts, there is a question of basis.

“opposite spin” makes sense in any basis.

Student404Mus

I think Quantum world is stronger than human minds though.

Semiclassical

@ZeroTheHero I take ACM's point in the above conversation to be that the phrase "opposite spin" is questionable regardless

ZeroTheHero

I don’t use it.

Semiclassical

fair

ZeroTheHero

13:50

the issue is that this language of “opposite spin” is based on simple geometrical addition of spins, and it comes with its difficulties.

In $\uparrow\downarrow$ the spins are opposite...

but it’s not an eigenstate of $L^2$ so... not sure what it would mean to say spins are opposite in this state. It is true that the projection is 0 so in this sense the spins are opposite...

but $\downarrow\uparrow$ has the same property.

the difficulty is that $\uparrow\downarrow+ \downarrow\uparrow$ has $0$ projections, is made of “opposite spins”, but does not have $S=0$.

so I don’t use this kind of terminology.

Semiclassical

“spin measurements on identical components give opposite results” is about as short of a statement as I can give

(For the singlet state only)

ZeroTheHero

for the singlet state. you get $0$ in any basis so it has the advantage of being basis independent.

Student404Mus

the triplet state is important especially coupling two 1/2-spin particles

Semiclassical

Yeah, the rotation symmetry of the singlet state is really quite handy

Slereah

@bolbteppa Yes I wish to add the ability to downvote comments

ZeroTheHero

13:56

when you couple 2 spin-1/2 particles you get either $S=1$ or $S=0$ so there’s nothing especially important about $S=1$. In fact methinks the $S=0$ states are probably more useful precisely because they are independent of the direction of the quantization axis.

Semiclassical

“Your comment is bad and you should feel bad.”

Student404Mus

lol

Slereah

I wish that kind of argument would pass in papers

Theorem : String theory is true

Proof : Trust me

ZeroTheHero

@Slereah the examples you provide so it is de facto true.

that it does pass in papers...

;)

Semiclassical

What’s the old Oppenheimer line—if we can’t refute it, then we must pass it over in silence

Slereah

13:58

:D

Semiclassical

(Re Bohm)

Slereah

I'm trying to compute the actual probability and it is

\begin{eqnarray}
P(L_{\mathrm{tot}} < K) &=& \lim_{D \to \infty} \int \ldots \int F(K - \sum_{i = 2}^{D(24d^2 + 2)} x_i) \prod_{i = 2}^{D(24d^2 + 2)} f(x_i) dx_i \\
\end{eqnarray}

It is less pleasant

I'm not even sure it's that

I fear that every distribution may have a sum inside

1

A: Behavior of infinite convolution products

Of course there's no such thing as an infinite convolution - if your question is to make any sense we have to recast it as a question about limits of finite convolutions. And then we have to ask in what sense the limit exists. We never get anything interesting as a limit in $L^1$ norm: ...

Hm

I guess that may be the answer

Yuvraj Singh...

Hi guys today I was on my terrace with bottle filled with water, and bottle had holes in its bottom, and earlier the bottle was sealed pack but some amount of water was coming out, and I open the bottle Cap and water start coming out from the holes at very fast rate. And suddenly the bottle had felt down.

I saw that water stop coming out from the bottle.

I couldn't understand what stops the water?

Slereah

14:14

I need to cast everything in terms of the same distribution, though

Student404Mus

@Semiclassical Now, I got it.

I mean not until few minutes ago

:)

Semiclassical

mmkay

Student404Mus

Sorry to be late. I red you replies many times

B. Brekke

I am studying a propagator in real space/real time, but I have to discretize time. It is the Hubbard model, hence nearest neighbor hopping. Is it correct that the particle can only jump one time per time step?

It feels like my propagator would then be hugely dependent on how small my time steps are

Student404Mus

@Semiclassical So, it's alright to say for the singlet state has opposite spins, because, $S^2$ operator takes the same value that of $S_z$. For the triplet state, the case is different. All what could be said about the latter is the projection is opposite, not the "magnitude". And the point where I stuck is, the magnitude confused with the projection.

That's why it's important to emphasize the words.

Semiclassical

14:25

@Student404Mus it's alright compared with the triplet state. As ACM and ZTH both emphasized above, the language of "opposite spins" is problematic for other reasons.

with the more sensible statements being...
For any M=0 state (singlet or triplet), the results of measuring the z-component of spin for the two electrons are guaranteed to be opposite.
For the L=0,M=0 state, this furthermore holds regardless of the axis you measure along. For instance, the results of measuring the x-components of spin for two electrons will also be opposite.

For the L=1,M=0 state, there is no such guarantee: the results only have to be opposite if you measure along the z-axis, and don't have to be opposite if you measure both particles along another axis (e.g. the x-axis).

Student404Mus

Indeed.

All clear.

Semiclassical

One can presumably compute the probability of opposite results in the case of x-measurements for L=1,M=0

my guess is that it's 50-50? But that's emphatically a guess

(it's not a hard calculation but that doesn't mean I feel like doing it)

Student404Mus

Normally, it should be 50-50

it doesn't depend on the quantization axis

Semiclassical

for the singlet state, you're correct

but not for a triplet state

triplet states don't have rotational symmetry

the quantization axis emphatically does matter for a triplet state

Charlie

In the case of the covariance principle and the covariant formulation of EM is there a reason to prefer covarience over contravariance? Or is this just a convention

Surely you can just construct everything contravariently and you just end up with the same equations that transform oppositely

Student404Mus

14:35

the state $\sigma_{\uparrow}(1)\sigma_{\downarrow}(2) + \sigma_{\downarrow}(1)\sigma_{\uparrow}(2)$

states the projection of the spin are opposite for the two particles

regardless the axis.

Semiclassical

That's false.

John Rennie

@Charlie I think you're mixing up two differenct meanings of covariance.

Semiclassical

The z-projection of total spin will be zero, but the x-projection of total spin need not be.

for the singlet state it is, because L=0 in that case

John Rennie

@Charlie when we talk about the covariant formulation of Maxwell's equations we mean general covariance rather than covariance and contravariance of vectors.

Student404Mus

But this is in case you chose the z-axis where the quantization refereed to.

Charlie

14:38

ahh

Student404Mus

If we pick another axis where $S_x=0$

Charlie

So the covarient formulation of Maxwell's equations just means constructing them in tensor form

Student404Mus

we don't know how $S_z$ would be

John Rennie

@Charlie yes

Charlie

Understood, many thanks

Semiclassical

14:40

Ok? But the states $|L=1, M_z=0\rangle$ and $|L=1, M_x=0\rangle$ are different

Student404Mus

yes

for sure

@Semiclassical do you mean probability amplitude?

Semiclassical

i mean the states are different

if you want a statement in terms of probability amplitudes, I'd say that $\langle \uparrow_x \uparrow_x|L=1,M_z=0\rangle \neq 0$

huh. if i do the computation in mathematica, it looks like the probability of opposite results is zero if you measure in the x-direction for the L=1, M_z=0 state

here's a quick computation

consider the state L=1, M_x=0. Up to a factor of 1/sqrt(2), that's $\uparrow_x \downarrow_x+\downarrow_x \uparrow_x$

Student404Mus

ok

Semiclassical

but in the z-basis, we have $\uparrow_x=(\uparrow_z+\downarrow_z)/\sqrt{2}$ and $\downarrow_x=(\uparrow_z-\downarrow_z)/\sqrt{2}$

so therefore we get $$\uparrow_x \downarrow_x+\downarrow_x \uparrow_x=\frac12(\uparrow_z+\downarrow_z)(\uparrow_z-\downarrow_z)+\frac12(\uparrow_z-\downarrow_z)(\uparrow_z+\downarrow_z)$$

which, upon distributing and cancelling, is just $$\frac12\left( \uparrow_z \uparrow_z-\downarrow_z \downarrow_z\right)$$

PM 2Ring

Peter Shor just posted an answer to that triplet state question, but he messed up the Mathjax. physics.stackexchange.com/a/540618/123208 I'd fix it, except I'm on my phone, and I'm not sure whether he intended to include those escaped square brackets or if he thought they'd function like double dollars.

Student404Mus

14:54

fine

Semiclassical

so you don't see opposite results for the z-component when looking at state L=1, M_x=0

in fact, you only see identical results

that's a fun little wrinkle

Student404Mus

yes identical results. That's what I meant before.

Semiclassical

ok

ACuriousMind

@PM2Ring He very likely thought they'd function like double dollars since \[ is one way to enter math mode in real LaTeX

PM 2Ring

@ACuriousMind Right. In that case, I'll fix it.

Semiclassical

14:58

so to sum up: If M_z=0, you definitely see opposite results for the z-components. If L=0, M_z=0, then you see opposite results for the x-components as well. But if L=1, M_z=0, then you instead see identical results for the x-components

(and presumably the same is true for the y-components)

ACuriousMind

@PM2Ring He's already edited it, the post was incomplete anyway

PM 2Ring

Ah, I see you beat me to it. Thanks.

Semiclassical

Another way to put it: The states |L=0, M_z=0> and |L=0, M_x=0> are the same state (up to a possible phase shift)

By contrast, the states |L=1, M_z=0> and |L=1, M_x=0> are different states entirely

so the singlet state is essentially unique and basis-independant, while the triplet states are very much not

Student404Mus

@Semiclassical perfect

Semiclassical

one notable fact: there's no such thing as an L=0 state of three identical particles

which means certain calculations are necessarily a pain in the butt since you can't rely on spherical symmetry at all

Secret

15:09

So thought up some crazy dimensional philosophy:

It is basically inspired from electric multipole expansions and r^n laws

Student404Mus

In my opinion, since |L=0, M_z=0> and |L=0, M_x=0> are the same up to a fixed rotation they sufficiently need to be defined in one frame to be distinguished. Whereas, |L=1, M_z=0> and |L=1, M_x=0> are identical need to be defined in different distinguishable spaces.

Secret

So basically I and a friend observed that the field of dipoles effectively partition space into two halves, one where charges will move towards the dipole and one where charges move away from the dipole

and then for quadrupoles, it does similar things to a point charge but now it is 4 qudrants

Student404Mus

@Semiclassical up to?

Secret

Now looking at gauss law for forces, which is $r^{-m+n+1}$ for a n dimensional charge density in m dimensional ambient space

it seems natural to interpret a dipole is basically a -1D dimensional charge density

Likewise, a similar curious phenomena is observed in relativity, and its 2 time extension in the scifi orthogonal, where spacetime is partitioned into 2 (light cone, elsewhere) and 4 regions (light cone, elsewhere with 2 constrained degrees of freedom) respectively

Thus it seems for a nD, object, n counts the number of constraints or degrees of freedom depending on whether n is positive or negative

so for a -1D dimensional object, it has one constraint, e.g. a directionality in the ambient space, or some other things that can only move in one direction

Using these, it is then straightforward to extend the interpretation to iD by using $i^2=-1$. Coincidently, rotating the lorentz space in a certain way can interchange space and time axes, so it seems to checks out

For n fractional, it is just the usual hausedoff dimensions

however, I have not figure out how to interpret $e^{i\frac{\pi}{4}}$ yet

ACuriousMind

There are no negative dimensions, please stop talking nonsense.

Secret

15:24

ok fine, you can trash the rest in case it distract new users

PM 2Ring

@ACuriousMind To be fair, Secret did warn us that it's crazy. :) But I certainly agree that stuff like that is probably better posted elsewhere.

Secret

@PM2Ring Well, I was actually shocked at that level of reaction from Acuriousmind. Clearly this is way way out of the league compared to my usual weird ideas

I cannot tell if I am overstepping the line from philosophy into crank territory here

but if that is the case, I will not do it again

ACuriousMind

Honestly, I don't usually read what you post here very closely. But I was just thinking that if the first thing I'd seen if I'd stepped into this chat room was someone going on about dipoles in negative dimensions - something which makes no sense at all in mainstream physics I should stress - I wouldn't have stepped by a second time.

This isn't "philosophy", you're just saying things that don't make any sense physically

Secret

15:39

right, understood

PM 2Ring

@Secret :) FWIW, I kinda like your idea of using negative dimensions to denote constraints, in complement of positive dimensions denoting freedoms. But it doesn't suit this room's predominantly mainstream physics culture.

Secret

right I should keep an eye not to disrupt the mainstreamness. I think worldbuilding will indeed be a better place for that kind of wild idea

I just did not realise I stepped over the line this time since in my past posts, most users are still ok and find the mainstream common ground in it to discuss weird ideas in mainstream context

skullpatrol

don't worry about it pal :-)

PM 2Ring

@Secret I suppose that when it's clearly obvious that you're talking about weird stuff (eg your recent posts that talked about Brahman & simulation) then people who aren't interested in that stuff will just ignore those posts. But if it's not clear & obvious that you are talking non-mainstream stuff, then the mods & ROs are (rightly) concerned.

Secret

yeah I clearly overstepped the line into the non mainstream this time, sorry about that

I think most of my recent philosophical posts, some of which Slereah, Semiclassical and others have give some interesting comments, do not touch the mainstream physics, so those are legitimately philosophy

but I think I did not realise this negative dimension thing gone too far into non mainstream, which indeed I agree they are rightfully concerned now I am made aware of that

PM 2Ring

15:56

Maybe you should find a more suitable venue for your musings. You have an interesting imagination, but I feel that the regulars here aren't really a great audience for your ideas.

Slereah

I say we burn the witch

PM 2Ring

Don't we have to test whether or not they float first?

Loong

She's a witch!

►

John Rennie

@PM2Ring wasn't the test being lighter than a duck?

JMac

@PM2Ring Budget cuts. Apparently the first test didn't make much economic sense when you have to burn all the floaters anyways.

ACuriousMind

16:01

European or African duck?

Loong

If @Secret weighs the same as a duck, he's made of wood.

skullpatrol

Peking duck.

Johan Liebert

Well the best test for witches was once shown in Simpsons(👇)!

The Simpsons - Marge is a witch Part 1 of 2 (S9Ep04)

►

Just throw the witch from a cliff if she flies away then....you know she indeed is one. If not then check for someone else. Try and error is the best way to do it.

JMac

Whenever I think of witches I just vaguely remember reading The Crucible as a class in school.

John Rennie

The irony is that at least in England in the 15-16th centuries people would claim to be witches because it offered them a degree of status and protection.

Though the job does indeed have its hazards.

PM 2Ring

16:08

Hey, we had to read The Crucible in school, too. (That was in the mid 1970s, in Australia).

JMac

I mostly remember it because I got assigned to read all the parts of one of the main characters, so like it or not I was quite involved in the class read.

Johan Liebert

> Double, double toil and trouble;
Fire burn and caldron bubble.
Fillet of a fenny snake,
In the caldron boil and bake;
Eye of newt and toe of frog,
Wool of bat and tongue of dog,
Adder's fork and blind-worm's sting,
Lizard's leg and howlet's wing,
For a charm of powerful trouble,
Like a hell-broth boil and bubble.

Double, double toil and trouble;
Fire burn and caldron bubble.
Cool it with a baboon's blood,
Then the charm is firm and good.

Loong

@JohanLiebert off topic, migrated to Chemistry

Johan Liebert

Well certainly I would like to have that potion.( Only if you had some alchemist who would understand that language!)

That is the lyrics of a harry potter song which was taken from a Macbeth (I think).

JMac

Hmmm, come to think of it I think we read Macbeth the same year we read the Crucible... That's a lot of witch based plays for one year.

Johan Liebert

16:18

@JMac Well did you investigate who designed your syllabus?

JMac

No. I didn't even really realize it until right now. I'm not sure how easy it would be to figure out who designed a syllabus ~10 years ago. Though it might not be too hard to find out if those books were required reading by the province or something.

John Rennie

What's a fenny snake? That Shakespeare should have smoked fewer of those herbal cigarettes.

Johan Liebert

Well I belive that your syllabus was switched with that of the Hogwarts (fun fact Hogwartz is in Australia!)

ACuriousMind

@JohnRennie Knowing what kind of snake that is is a sure sign of being a witch, I guess

John Rennie

Googling comes up with a range of possibilities including the option that Shakespeare just thought the word sounded good and it means absolutely nothing :-)

skullpatrol

16:29

Shakespeare kinda rhymes with Snakespeare :-)

Johan Liebert

Shakespeare misspelled funny as fenny.

skullpatrol

\o @TerryBollinger

John Rennie

There are interpretations based on the use of other vowels, but since I don't want to be banned I will not go there :-)

ACuriousMind

I was trying and failing to make any joke in that direction that even qualified as double rather than single entendre :P

John Rennie

:-)

JMac

16:34

@JohnRennie That was my first guess. Didn't Shakespeare invent a bunch of words?

Yuvraj Singh...

@PM2Ring hi.

PM 2Ring

16:47

@YuvrajSingh... Hi.

@JohnRennie Which reminds me...

"Mind you, the Elizabethans had so many words for the female genitals that it is quite hard to speak a sentence of modern English without inadvertently mentioning at least three of them."
— Terry Pratchett, in alt.fan.pratchett

ACuriousMind

@PM2Ring I seem to recall the sort-of inverse story where Puritan doctors had trouble treating their patients because they'd describe anything below the waist as their "ankle", but I can't remember where I read that

skullpatrol

17:33

how can you do labs online? @Semiclassical

Semiclassical

ehhhhhh

today it went like this

first, i talked about the warm-up questions they submitted ahead of time. (the point was to derive the expression for the centripetal acceleration)

then I put them into smaller groups to talk about the lab video that we provided them. this didn't go as energetically as I'd hoped but that wasn't a huge shock

once I felt like they'd come to grips with the video, I brought them back together and walked them through the data analysis (which in this case was basically just "show them Google Sheets formulas")

and gave some suggestions as far as what their next lab report would look like

skullpatrol

I see.

Semiclassical

so, pretty smooth. just a bit exhausting

skullpatrol

17:49

coolio

Aaron Stevens

1

Q: Plausibility of obtaining optical spectra of viruses

Ok, this is a huge long shot, and I also apologise if this is a poor question (I'm a newbie here...). This doesn't seem to me a strictly perfect fit for Chemistry.SE, Biology.SE, or Photography.SE either, so hopefully it's acceptable here, given that there is some level of Physics involved...(ple...

spectroscopy biophysics experimental-technique nanoscience imaging

What do people think about this question in terms of it being considered "engineering"?

As discussed in the comments, it seems like the close banner for engineering type question should be modified. Any thoughts on this?

ACuriousMind

@AaronStevens I understand where that's coming from but I think there isn't really a formulation that fits into the word limit of the close banner that captures what we mean by "engineering". See physics.meta.stackexchange.com/a/6136/50583

skullpatrol

2 hours ago, by Slereah

I say we burn the witch

ACuriousMind

Meta is ten years old at this point, we've had most possible discussions already :P

Transcript for