The h Bar

Q: Why are downvotes (on the meta side) regarded as a (negative) answer to your question (on which you can answer yes or no)?

3:13 AM

@antimony There's several benefits -- the first is compression. I can take a large number of data points and fit it into N terms for an Nth order equation. The second is super-resolution. With a fit, I can find values anywhere I want between the data points quite easily (which could be done with a lookup table also, but that's just fitting on a subset of the data so it's quite similar anyway)

The third is really related to the first, which is removal of noise from the signal. This is part of compression as well, but if I have a set of 10,000 samples, depending on the fit, you can reduce the impact of outliers and so on. In a lookup table, it's harder to identify whether a region of the table is reliable or whether it's noisy

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Unrelated:

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RewCie

4:33 AM

JR Sir >>>>>>

That's it. That's the fact.

Physics Meta

9:36 AM

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In this question I asked whether it is a good thing to edit a question with the purpose of downvoting it. It got downvoted 7 times (up till now). This was written: Downvotes on Meta are different than on the main site. Here they indicate disagreement with the idea that it is okay to edit a quest...

discussion questions down-votes

bolbteppa

12:07 PM

What Does a Quantum Field Theory Course in the 1970s/1980s at Harvard Look Like?

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Physics Meta

12:32 PM

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Q: Is it possible to make this community more welcoming?

I recently have been cyber-stalked by a particular user on both physics meta and the main site. The past 3 times I have logged on, this one user instantly downvotes whatever I post without reading it, and then makes an insulting comment to me. I brought this up to the Mod's in comments (again) a...

discussion

BioPhysicist

1:40 PM

Geeze, someone really doesn't like me lol

I didn't even realize I was engaging with the same person when I was commenting on their posts

rob

@BioPhysicist Without saying much publicly: that user has had a rough week. Please assume it’s not you.

2:02 PM

@tpg2114 "We have placed a horn on a horse" curiously does not specify where they placed the horn. I'm now imagining the NASA version of a "unicorn" looking more like a spiky camel

BioPhysicist

Considering the complaints in the post have been explicitly said to me it's hard not to. I'm thinking of commenting an apology, but I'm not sure if that would make things worse.

@ACuriousMind That's where there's so many versions of the CAD... Need to optimize the horn location through rapid design iterations

ah, makes sense

rob

2:18 PM

@BioPhysicist I won’t advise you about apologizing or not. I’m skirting the line of revealing private information closer than I usually like, but: to the extent that it’s you, it’s not only you. You’re not the only person who doesn’t always notice usernames.

In a too-close-to-home scenario, the whole hardware_v8_final_final_yesterday_today.cad thing bit me last week. I have been trying to get a simulation working for the past 6 months or so but it turns out I was given geometry that wasn't real and operating conditions that would never work

But since I was using a newly-developed code feature that was done during a sprint to "demonstrate capability," it had no V&V done so I spent forever trying to figure out why my code was wrong. And it's for a problem nobody has ever done before so we don't have a guide for how to do it, so I spent the next forever trying to figure out why my models were all wrong

Turns out I just can't trust experimentalists...

BioPhysicist

@rob True. Thanks for the input

@tpg2114 Why can't our models just live in isolation? ;)

I know right? Forget digital twins, I want to have digital only-child's

2:55 PM

@tpg2114 V&V?

Verification and Validation

My only proof that it was implemented correctly and well-suited to the problem were some pretty pictures of stuff flowing around, but 0 actual quantitative data

Oh, and that hypersonic turkey from Thanksgiving!

Nov 23 '20 at 16:04, by tpg2114

That was the extent of my proof the code works

it's more than I have for plenty of the decades-old code I find lying around over here! :P

The folks around here, even the scientific-computing folks, seem to misunderstand what "Agile" software means... I think they are under the impression it means we do "sprints" between capability demonstrations but keep on sprinting to new topics before people realize our previous capability doesn't work right

If you can keep outrunning your mistakes and then move to a new position before they catch up to you, you can get ahead it seems.

I'd bet a majority of "agile" practitioners misunderstand what it's really supposed to mean

or, well, maybe not the practitioners themselves, but many workplaces have structures that are fundamentally opposed to how people are supposed to work in agile environments

3:12 PM

Indeed... that's absolutely true where I work.

I think there's also a lot of people who just jump on the "Let's do agile!" because they heard a summary about it somewhere

Which leads to very interesting interpretations of what it means.

Q: Why my question has been closed?

3:23 PM

it's not necessarily a bad thing to have such structures - everything doesn't become magically better if you try to do them agile-by-the-book, I think.

but the pretend-to-be-agile-but-not-really is almost never helpful

Shing

4:23 PM

um.....

is AccidentalTaylorExpansion just AccidentalFourierTransform?

Physics Meta

4:46 PM

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I would not have wanted to write this, in fact I am so sorry of the fact that many times some questions are not considered as they are too stupid. My question Scalar curvature is $0$ for Schwarzschild solution has been closed soon after the writing. I have not undertand why...in effect I have tr...

discussion scope questions homework-and-exercises close-reasons

@Shing A Taylor expansion and a Fourier transform are very different things ;)

on a more serious note, please don't accuse other users of having multiple accounts - if you really have reason to believe a user is using multiple accounts you can raise a moderator flag on one of their posts, but it's generally not forbidden - only if you use them to do stuff you couldn't do with a single account like upvoting yourself.

Shing

5:34 PM

@ACuriousMind um, I didn't even know if that's breaking any laws(?) I just like AccidentalFourierTransform's answers a lot, no idea I should follow one more guy (AccidentalTaylorExpansion's answers look good too, but I haven't give them serious look)

5:50 PM

I feel so bad for people that are in the process of learning about tensors from physics textbooks every time I see a post on PSE asking about what on earth covariance and contravariance mean geometrically

differential geometry is not magic, but physics tests sure make it look like it is :P

It seems like tensors are something we go so far out of our way to make "physically intuitive" in physics and I've never seen it not cause more confusion than it alleviates

I wonder how much the current progression of physics has a negative impact on those learning it, students are expected to learn more and more complicated physics earlier in their physics education and it seems like the necessary mathematical background gets more and more compressed

presumably there was a time when quantum mechanics and GR were standard postgraduate topics, but now introductory string theory, supersymmetry and gauge theory are all master level topics

@Charlie I feel physics education, like most education, varies so widely in structure and form it's impossible to say in general

for instance, I had enough room to take most of the math courses needed to understand what was "really" going on, but it seems people at other unis and especially other countries often have very different schedules with less potential to just go learn the math if they want to

and I know plenty of people for whom the physics math was enough and they never really worried about it - remember, most physicists aren't really "theoretical physicists", let alone QFT people or string theorists

6:16 PM

Physics math seems very much like something that is learned through exposure rather than careful analysis like you would expect in regular math. Most of the language in high(-ish, as far as I'm able to know) level physics is very colloquial and e.g. the same word/phrase can mean fairly different things in different contexts, which to the uninitiated (like chemistry students, where calculus is a fancy shmancy mathematical tool) almost always causes confusion

I guess there's no sense to complaining about it, but it does add an extra layer of difficulty lol

A frequent (but not necessarily the worst) offender being the synonymous usage of symmetry, covariance and invariance

@Charlie I hear ya. The most common error is to confuse invariance and covariance...

@ACuriousMind of course what is "really going on" is in the eye of the beholder...

completely agree, hence my scare quotes around "really" ;)

Honestly you'd think there was no difference because many physicists will use those words completely interchangably

(general) covariance is a terrible word anyway because it has a rather different established mathematical meaning (as the opposite of contravariance)

@Charlie Having worked and published with mathematicians, I have come to peace with their way of doing things. I know enough to know that I'm not a mathematician, and enough to know that one can obscure many things by using fancy math.

Yes one can think of a Fourier decomposition as an example of an infinite-dimensional space with an inner product: while technically correct it's not a terribly practical definition for most people in physics.

6:27 PM

pff, Fourier transforms are just an elementary example of Pontryagin duality

yeah that too... and there's the point of view of group theory where you do a character expansion...

more seriously though - the infinite-dimensional space with inner product viewpoint becomes very natural in quantum mechanics, but you're right no one would think about it in classical physics in those terms

of course! and in some sense that's the thorny part of this argument: it is entirely correct to think of FT as an example of an infinite-dimensional inner product space... like any expansion for that matter...

and regrettably not that many students realize that the eigenfunction expansion of QM is in fact nothing but another more "sophisticated" example of FT.

Actually while this topic is being brought up, I always wondered why whenever I've seen the FT written in the mathematical context it is an integral over an exponential, but in qft you have an integral over two exponentials, $e^{ipx}$ and $e^{-ipx}$

but in the case of FT the sine and cosine functions are rarely presented as solutions of an eigenvalue problem...

6:33 PM

just one of the many things that's been in the back of my mind that I haven't given much though, presumably there is an innocent enough reason

and probably an example of where learning fourier analysis in a non-physics context would solve all my problems, the only times I've used fourier anlysis in my entire life is when I've been forced to in qft, it's still a bit mysterious to me

@Charlie seee physics.stackexchange.com/a/216194/50583

it's not a generic Fourier transform, it's specifically for something that obeys the free equation of motion