4:15 AM
why David has resigned from the moderator of the room?does anyone know why he has resigned?

nebula, nova, supernova all result from the play of white dwarfs.

@JackRod DavidZ was a site moderator from the early days — most of a decade. Life changes happen. I don’t think he has shared any public details.

5:06 AM
He has left contact details.
If you are interested to get in touch...

1 hour later…
6:21 AM
@ACuriousMind, what is the difference between the partition function $\int e^{-L(A)}dA$ and the quantum action $\int e^(i/hL(A))dA$? Can we use either one to describe a quantum system?

7:12 AM
@Charlie Overall when you go GR, try to remember that you're building a structure
you keep adding more features on a mathematical object
You have to try to remember which ones are important for some aspects, and which aren't
You don't need the metric to define vectors, you don't need vectors to define the topology, you don't need the metric to define the connection, etc etc

7:27 AM
Sept 18, 2020: dmckee & David Z are officially no longer Phys.SE moderators. — Qmechanic ♦ 16 hours ago
:-(

2 hours later…
9:35 AM
@juliensurel both are partition functions, the former for a Euclidean theory, the latter for a Lorentzian theory
the Lorentzian version is the "physical" one - the real world is relativistic, this is the integral we "should" take
but it turns out that the Euclidean one is easier to compute and the correlation functions you compute with it can be analytically continued in the time variable to get the Lorentzian versions without having to try to compute the Lorentzian path integral, this procedure goes by the name of Wick rotation and the theorem stating that this analytic continuation gives the correct results is the Osterwalder-Schrader reconstruction theorem
this idea is at the core of mathematically rigorous formulations of path integrals in the vein of Glimm and Jaffe, since the Gaußian measure involved in the Euclidean version can at least in some cases be defined properly, while the oscillating phase in the Lorentzian version doesn't have good convergence properties

10:31 AM
There is a theory for Lorentzian ones, tho

@JingleBells Posting like this borders on SE's definition of spam. If you post something here you made, you need to at the very least disclose clearly you're advertising yourself and ideally explain why it's relevant to the room beyond you wanting to advertise it.
@Slereah pray tell!

That video up above is mine and I'm advertising my idea in this chatroom because I know some people here code and I think it might be relevant to them.

@ACuriousMind Cecil De Witt did a whole thing on it!

@JingleBells Every programmer already uses SO as a code snippet library. How is this better? Also note that a significant fraction of professional programmers take a very unfavorable view of blindly copy-pasting code.
@Slereah this seems to be a path integral in the original sense, i.e. not for fields

11:07 AM
@ACuriousMind nobody's perfect
It's in the imaginary exponent regime tho

@ACuriousMind Sure, SO has a lot of useful code you can search for and copy-paste into your project, but this is better because with VES1 you can also save code you have found useful from all over the internet, not only SO, into a nice little library you can access with a shortcut.

@Slereah I'll give you that but I still feel cheated :P This seems like a generalization of the idea of the Wiener measure to arbitrary manifolds, not like a Lorentzian version of Glimm/Jaffe's Euclidean path integrals for fields

@ACuriousMind perhaps it can be generalized, though

@JingleBells I'm a bit confused in what situation I'd need to copy-paste a code snippet I've already used - if I need to use the same code in different locations, I write a function that makes it reusable, not paste the code!
if I find I need the code across different projects it'll become a small reusable library

I'm sure nlab has the generalization somewhere :p

11:13 AM
@Slereah I'm sure it doesn't because a rigorous formulation of arbitrary path integrals would essentially solve the Yang-Mills millenium problem
they might have a generic description of what categorical properties such a formulation would have to fulfill but no implementation of it :P

@ACuriousMind The VES1 public snippets library is not a library for specialized code. I mean, if your function is specific to your project, that will not be pretty useful to other people, but you can still save it and use it across different files and projects.

@ACuriousMind depends if it's constructive or not

@JingleBells if it's generic code all the more important that I publish it as a library for everyone to use!

If it's just "here are the properties it should obey" that's probably fine

what's the point in everyone copy-pasting e.g. the implementation of a HashMap if someone can just put it up on e.g. GitHub and everyone can then depend on that library?

11:17 AM
@ACuriousMind Sure! Take the example of a javascript function that capitalizes the first letter in every word. You simply save it with a quick shortcut and now not only you but anyone can use it.

@JingleBells again, the way one shares code with other programmers in almost all modern languages is to put it into whatever that languages notion of a reusable module or library is and make it free to DL for everyone
javascript is notorious for doing this e.g. with that module that just snipped off whitespace at the left of a string or whatever

@ACuriousMind Where is this DL? How can I be sure that the DL has what I need...? Why would I bother with a DL when I need only one snippet?

@ACuriousMind also they could have one that works but just for free fields

@Slereah that's true
@JingleBells look, whenever I want to do something sufficiently standard that I'm sure someone else has already written it I put "<language> <thing I want to do>" into Google. In well-maintained languages, I'll find the most used library in that language for this task in the first hit (or the SO answer pointing to the most used library :P).
how exactly you use such a library in your project depends of course on the language but most modern languages have some sort of "package manager" for this purpose making it easy, and this is a very standard workflow for people working in that language

@ACuriousMind Why bother downloading packages and stuff like this when you can download a simple VES1 program that has all sorts of snippets for all sorts of language. You don't have to leave your text editor software to get the code, it's fast, it's simple and easy. Not only that but you can save your own personal snippets.

11:24 AM
and after that I just need to remember the name of the library (or google it again). Not any harder than copy-pasting some snippet, and avoiding duplicating code. Library code is also likely to have been maintained and reviewed by other people, making it more trustworthy than a random snippet - this is the basic idea behind open source!

People will be able to vote on the snippets (or there will be an option to show the most used ones) when describing what you need in the little search bar.

@JingleBells Because copy-pasting code makes it harder to maintain. Say I've pasted this code into five different places in my project and suddenly realize I need to modify that logic a bit for my particular use case. Now I need to manually find all the pasted locations and change each one individiually. This is error-prone, inefficient, and contradicts every principle of designing modular code
Your tool would essentially encourage programmers to write unmaintainable messes of copy-pasted code with no clear design principles, separation of concerns, or DRY guidelines. This is a tool for lazy programmers, not for people who care about code maintainability or quality.
Sure, it would be convenient in the moment. It won't be convenient for the poor future people who have to maintain code produced this way.

What are you talking about? VES1 is not a "code maintenance" software. When you copy-paste code from SO in different places, you still have to edit it manually if you've pasted into multiple locations.

There is a large extant discourse around why copy-pasting code is usually discouraged, and I've barely summarized it above - one buzzword is the Don't Repeat Yourself principle if you want to look it up

I do encourage lazy programming, dull copy-pasting, but that doesn't mean that quality and maintainability (whatever you mean by that) can't be established. VES1 simply gives you access to the code, nothing more. It's a dull library for code snippets.

11:31 AM
@JingleBells You shouldn't do this with code from SO either, of course! Copy-pasting it at most once and making it reusable is the proper way to go.

@ACuriousMind I do not think so

@JackRod now if you told me what exactly you disagree with and why we could have a discussion :P

but yes my brother even say it is the bad practice among devlopers

@JingleBells If you don't know what maintainability means in the context of software I suggest you first research what software development is before you try to write tools for software developers.

I was reading your discussion of copy-pasting of code so I shared my remarks on that

11:36 AM
@JackRod sure, but you just wrote "I do not think so" after I had written several different - though related - thoughts. I still have no idea what you disagree with and why, so you communicated no information to me

@ACuriousMind can you please give me a quick summary
nvm
"Maintainability refers to the ease with which you can repair, improve and understand software code." How VES1 stops you from doing that?

@JingleBells not really, it is a large topic with different camps emphasising different aspects, and sometimes vehemently disagreeing with each other. Buzzwords to search for include technical debt and complexity measures. The desire to write maintainable code is also a motivation for disciplines like TDD (or any other development methodologies, really)

@ACuriousMind you said it is a not good to copy-paste code but what the other options we have then?
proper re-use takes extra time and money (in the short term).

@JackRod I already gave several examples of making code reusable, didn't I?

so everything as it's pros and cons that is what I saying

11:42 AM
it takes more time and money in the long run when people have to hunt and fix bugs in messy code

@ACuriousMind I have experience in coding websites, programming javascript, css design, etc... I relate VES1 to my own problems but I believe you are a hardcore software developer and you deal with plain old C++ and this sorta code. I can't really think of any code (other than your own) that you would get from the internet.

sometimes there are certainly external pressures that make it necessary to cut down on quality, but I'm firmly of the opinion that as a discipline we shouldn't encourage it. Other engineers might sometimes construct stuff not up to e.g. safety standards of their discipline either, but no one wants to give them tools to make that easier either

Lol I have nothing to say more, your choice your wish do it then you will get to know what is good and what is bad
@JingleBells\

@ACuriousMind When you're programming specified software, you know, hardcore complicated stuff, do you at all go and copy paste anything from the net?

@JingleBells My main work is in ABAP, but I've also written (and am writing) code in C, Python, Haskell, Delphi and Rust. I've extensively used libraries produced by other people to solve small and big problems for me.

11:46 AM
@ACuriousMind ABAP ?

the only code I really copy-paste is the boilerplate necessary to use these libraries, but well-designed libraries shouldn't need much of that anyway

@ACuriousMind What libraries? I know about python pip libraries, so is this what you're talking about?

@JingleBells Yes, for example. Python's numpy for numerical calculations is an example of a library solving a "big" problem, the javascript module left-pad that pads whitespace to strings is an example of a library solving a very small problem.
(the latter became rather infamous due to javascripts poor module management, look it up if you haven't heard of it)

@ACuriousMind Sorry, I gotta go, but I'll be back later. I'll think about your feedback, thank you!

1 hour later…
1:18 PM
Hey everyone,

When people say "the gamma ray radiations cover over large areas from 500 cm^2 to 100,000 cm^2", did they mean areas from 23 cm to 316 cm width area? I used an online converter and I got these figures.

You use "an online converter" to simply calculate the square root of a number?

1:49 PM
@FadedGiant lol yes I'm using this endmemo.com/cconvert/cm2cm.php so it is not true at all?
@FadedGiant do you have any idea what they mean by that? I'm curious

A unit converter for "square centimetre to centimetre" doesn't make sense since that's obviously not the same dimension.

@FadedGiant so what is approximate measurement in cm, meter or foot for 500 cm square to 100,000 cm square?

2:15 PM
@ACuriousMind Sup, I was thinking about your feedback. I realized that VES1 should be mainly targeted towards web developers, javascript, css, etc... because you are a "hardcore" software developer and now as I think about it, there really isn't any way VES1 can help in plain ol' software coding in languages like C++, Python, because there really isn't any "common" elements in the code. In the sense, if you build some type of a software, there isn't any part of your code that you can share with
others that will make sense in their project.
What do you think about that?

The mathematical term perverse sheaves refers to a certain abelian category associated to a topological space X, which may be a real or complex manifold, or a more general topologically stratified space, usually singular. This concept was introduced in the thesis of Zoghman Mebkhout, gaining more popularity after the (independent) work of Joseph Bernstein, Alexander Beilinson, and Pierre Deligne (1982) as a formalisation of the Riemann-Hilbert correspondence, which related the topology of singular spaces (intersection homology of Mark Goresky and Robert MacPherson) and the algebraic theory ...
The worst sheaves

2:36 PM
@JingleBells I think "there isn't any part of your code that you can share with others" is a massive misunderstanding of how software development works. Look e.g. at Rust's crate registry. Rust is a language very much intended for what you call "hardcore" software development. Every crate there is functionality that someone thought might be useful to others so they published it there.
These are not executable programs, they are libraries intended to be used by other developers in their projects. This is how software developers share code. Javascript has a similar concept with npm for node modules. In C(++) it's more barebones via including header files but the idea is still the same. Maybe I just don't get what sort of code you think people might put into this VES1 because your video didn't show any examples - all the code was just colored lines.

That's what always amazes me about this chat room. People who talk about gigaelectronvolt nuclear physics but cannot calculate the measurements of a square.

@Slereah they aren't even actual sheaves!
pretty perverse

@ACuriousMind that's what's so perverse

2:56 PM
@ACuriousMind Hmm, alright, regarding this, I have a question - do you, as a "hardcore" software developer, google for a code that you copy-paste into your project?

@JingleBells Usually if I don't know how to do something I'll google how to do it. The results are generally of three types: 1. There exists a ready-made library that does what I want with a simple call. So I'll depend on that library and "copy-paste" the call to where I need it - but the copied code alone doesn't do anything without the library, so I would not have been useful to have quicker access to that one line of code as text.
2. There are several things that do parts of what I want and I have to figure out how to glue them together. You'll often find examples of how to do that if the task is sufficiently common but usually no example works right out of the box for my particular use case - again, understanding the parts is the important thing, not copy-pasting the glue code. 3. It's a major task (e.g. 3D graphics programming) and I have to learn how to use a very complicated framework.
the only times I'd say I'm really just copy-pasting is when I'm learning a new language and copying idiomatic solutions in that language to play around with them

So in hardcore programming, it's all about libraries? Such as Python where I myself constantly do pip install <package>?

I would strike hardcore from that, but yes - that's what programming is - either you're writing a library, you're using one, and very often both.
The dependency graph in this xkcd is not an exaggeration for most large projects :P

Got it, thanks. The idea arose from my own frustration that when I'm doing web development, I frequently find myself going to google and searching for a code to copy-paste, such as proper syntax, or a css fit background image... I never thought about it in plain software development.
In terms of software, there are libraries, yes. I never fully explored where the software is applicable. It's easy to fool yourself (or subconsciouslly pass something) when you're excited about an idea.
What would you say about web development? Do you think VES1 can fit in there?

3:13 PM
By "web development" it sounds as if you mean the front-end part of writing HTML/CSS?

Sure, but what about javascript. For example, look at this - morioh.com/p/a76bc7d72226 There are JS snippets (and HTML, CSS, PHP snippets) scattered across the internet.

because that term usually also includes a back-end part of writing the software that runs on the servers, which isn't that much different from writing any other software, just requires domain knowledge about what's important for such software

I frequently find myself googling how to do a certain javascript thing and then I end up copy pasting the code.

@JingleBells Most of these are one-liners or very close to one. If you understand how they work you should be able to reproduce them after you've seen them there.
copy-pasting them from some repository seems only useful for people who want to produce code without investing any effort into actually understanding how it works
note that all of these also define functions. If you find yourself using them often there is nothing prohibiting you from putting them into your own javascript module that you can then reuse across your projects by calling the functions
(yes, even javascript has understood that modularization is the way to go! See also developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules)

@ACuriousMind The goal is to have one global public module that anyone can access and use. For the "hardcore" programming part, I agree that VES1 is not applicable and it really doesn't make sense. What makes sense it supposedly private snippets for teams that are project dependent (something like functions for the team). But I'm struggling to understand why VES1 is not applicable in HTML, CSS, JS or PHP. SO is full of questions like "PHP how to sort an array" or stuff like that.

3:23 PM
SO is full with questions by people who are apparently unable to read any sort of documentation or understanding anything about how the language they're using works :P If those are your target audience, fine.

If those are my target audience (which is pretty big btw), do you think it'd make sense for them?

I don't really understand how such people work, so I can't say anything about that

@ACuriousMind Alright. Thank you!!!

I just personally think we should not encourage avoiding understanding the tools/languages we're using as developers
if you can't write one line of code on your own, what really is your qualification?

Oh, most people actually understand what they're copy-pasting, they are just lazy to write or have forgotten how to.
But if I start going through what I'm copy-pasting, i'd understand how it works.
I agree that copy-pasting things you can't understand is dumb. You should sit and learn to read the code, but after that, I think it's okay to copy-paste things that work because now you can read through them and understand how they work, make chances, etc...

3:31 PM
Sorry to interject, but what quantum system is described by $\Bbb C^3$? Is this a spin-1 particle?

And VES1, an app for web developers :), can make the copy-pasting of code (that people can understand) easier and faster.
I'm asking web developers for feedback too. @ACuriousMind Again, thanks :--)

Nvm I'm 99% sure it's a spin-1 particle

@Charlie well, that or any other thing with an observable with three eigenvalues :P

true :p I should have added this is under the subsection "spin" in the notes

e.g. a quark's color space is also $\mathbb{C}^3$

3:36 PM
does this relate to the CKM matix?

but that $\mathbb{C}^3$ is not the spin-1 of $\mathrm{SU}(2)$ but the fundamental rep of $\mathrm{SU}(3)$

ok that's roughly what I'm reading atm

@Charlie no, that one acts on the quark types, not colors

ah

well guys, at least I finally failed a project in just 5 days, not +4 months.
idea validation.
I'm talking to web developers and still gathering feedback, but things are tilting towards the "not really worth it" side.

3:56 PM
why, with the entire greek alphabet at your disposal, would you represent the state of the system and the eigenvectors of some random observable with the same symbol

4:52 PM
@Charlie It's a common thing

seems like very poor choice of notation though

You're unlikely to get confused
Since the eigenstates always have a subscript

It's not indecipherable, but you have to read more slowly and carefully for no good reason

5:36 PM
hey guys
I am not sure if it is a good idea to buy the 2nd edition of Sakurai's modern quantum mechanics
I have heard some ppl said that the 2nd edition is worse than the 1st edition?

6:18 PM
People say that about every book
Also I think they say the 2nd volume, Advanced QM (maybe this is what you read?) worse than the first QM book because he didn't finish the 2nd fully or something

6:37 PM
@ACuriousMind What about removing public snippets as a whole? What about private snippets you create for yourself to use across different projects?

7:15 PM
@JingleBells I don't see how that would improve anything. All my points about preferring to re-use via functions and libraries instead of copy-pasting apply internally in developer groups (even groups of one) just as well as in the public sphere.

7:30 PM
@ACuriousMind Forget about libraries. I'm talking about the things you copy-paste from the internet. Or the code that you can save as a private snippet because you constantly use it across your projects.

@JingleBells I don't really know what code you're talking about. If I catch myself typing/pasting the same thing more than twice (and it's more than one line) I'll make a function out of it. With the autocompletion modern IDEs offer I don't see how copy-pasting some snippet I have to search first would be quicker than entering the line assisted by autocompletion.
If copy-pasting things - from the internet or elsewhere - makes up a significant fraction of what you call programming we have very different programming styles.
I don't even spend the majority of my time "programming" writing code!
(not that that's not a reason to make the "writing code" part easier, sure)

I guess I really don't know what code I'm talking about either. I've been gathering feedback and I view the idea from many angles now...
A lot to consider.
- Would not download it. Doesn't want his snippets to be public.
- Would not download it because it's not IDE integrated and is a separate software.
- Would download it. He's gonna use it like a tool to help him remember code and syntax since he's still learning.
@ACuriousMind I don't know why I'm bringing up the topic again considering the fact that it's targetted towards web developers, and you see it from a plain software developer side. And by the way, if I was programming in Java or C++, I too wouldn't have any use for random public code.... I mean... what am I going to google other than the most basic stuff such as "How to sort an array alphabetically".

7:49 PM
@JingleBells I feel we're going in circles - I told you there's plenty you search for. But the solution to most questions I have about programming is usually not "copy-paste this code" but "this library does what you want" or "the following algorithm is the most efficient solution to your problem" or "the traditional solution here is the following design pattern"
Having the algorithm "copy-paste ready" doesn't gain me much because next time I might have to use it in a different language, or with different types involved, etc.

@ACuriousMind What questions do you have?
You're not a web developer, and therefore not in my target audience. You cannot view programming as regular copy-pasting from the internet so what are we talking about.
There's so much points to consider and I don't know what we're discussing at this point.
I will almost certainly not build VES1 but I still want to explore the idea.

I suspect there'd be plenty of web developers insulted by this description just as I am by the idea that programming generally might be reduced to copy-pasting :P

Why would it be reduced to copy-pasting?

Dismissing what acm is saying just because he doesn't fit what you consider to be your target audience sounds a bit like you just want to use confirmation bias.

@JingleBells You seem to believe that there is a certain kind of programming that consists mainly of copying stuff from elsewhere
I believe that this is just bad programming :P

8:00 PM
Why?
I constantly copy paste stuff.
And I understand them.
@Charlie I'm not dismissing anything. I'm just pointing out that the app is not targetted towards him, and he views it from his own perspective.
Ahh I'm really tired

@JingleBells I've explained that at length already.

It's late, I'm tired, let me save you and me some jibber-jabber. Goodnight.
(hopefully to be continued...)

The night is still young! But good night ;)

@ACuriousMind Not when you wake up at 6:10 AM for school ;( cry everitim

...you have school on the weekend?

8:04 PM
@ACuriousMind xDDD no but I'm still in the schedule.

ah, that sucks. (Un)fortunately I never adjust to rhythms that have me waking up before noon :P
getting up early during the week doesn't seem to change how long I sleep "naturally"

How about VES1 but for CSS only? Targetted towards web developers and designers. You're building a website, you don't know what button to put. Press shortcut, choose button style. There must be some IDE plugin for this, right?
I guess I'm not sleeping :P

8:27 PM
@ACuriousMind I have now read the various wikipedia articles on coherent states, including en.wikipedia.org/wiki/Husimi_Q_representation and en.wikipedia.org/wiki/…. I certainly learned a lot, especially about quasiprobability distributions. Before I wondered what people mean when they say that negative probabilities would allow you to reproduce QM without using Hilbert spaces and complex numbers.
Just to clarify: now that I understand, I think that focusing on the fact that some quasiprobability distributions can take on negative values is a mischaracterization of the relevant concepts.
As primarily a mathematician educated during the first wavelet hype, I also started to wonder about how much the subject of coherent states is actually related to the subject of wavelets. There certainly seem to be some common themes. But at least my exposure to wavelets did not need any representation theory of Lie groups. Or perhaps it was just omitted, because mathematicians are not so deep into that subject.

3 hours later…
11:10 PM
@JingleBells God I do not miss high school
My quality of life greatly improved when I no longer had to wake up at 6
That said it's prob gonna go back down when I get a job