The h Bar

John Rennie

10:00

Things like how long the list can get and what get's stored along with the board are all specific to the game, so it makes sense for the games to handle them.

Bernardo Meurer

Already, I'll begin work :D

I hope the prof likes this thing lol

John Rennie

When you eventually turn in the project it's going to be a long file with all those structs in. I'd put in lots of commenting to guide whoever is marking it e.g. above the struct _board code put in a comment explaining exactly what this chunk of code is.

I.e. make it absolutely clear to the prof why you've done it this way.

Otherwise, given that he's marking lots of these, he might just think it's too complicated and not read it properly.

Bernardo Meurer

@JohnRennie Absolutely, yeah, once I'm done with the Game functionality I will pause additional stuff and document all the new things

Then I will only have a couple more things to do
1. Game log at the end of game
2. New game dialog
3. Saving a game state to a file that can be later loaded

typedef struct _Game {

    typedef struct _state{
        int score;
        time_t game_time;
        Board board;
        struct _state *next;
    }state;

    void (*move)(Board *, SDL_Keycode);

    // void (*undo)(Board *, SDL_Keycode);

} Game;

Looks reasonable?

John Rennie

Which end of the list are you going to put the active board?

Bernardo Meurer

I was thinking it should be the head

Or wait

No

the tail

John Rennie

10:12

I ask because you'll normally be wanting to undo backwards from the current board, so the current board probably wants to point back to the previous board.

Bernardo Meurer

Indeed

John Rennie

With only one link pointer you can only navigate the list in one direction, and that direction probably wants to be from the current board back towards the initial board.

Bernardo Meurer

So I guess my pointer should be prev

John Rennie

Yes, that was what I was getting at.

Bernardo Meurer

For clarity's sake

John Rennie

10:15

So at each move you calloc a new state, do the move to populate it, set the prev link to the last board then set the game to store the newly calloced state.

Bernardo Meurer

When I go backwards on the list I have to memset the state I left also, right?

John Rennie

I'm not sure what that means.

If you're undoing, e.g. by one move, then just free the board at the end of the list then update the game with the new current board.

Bernardo Meurer

I guess it's better to just free the memory, yeah

I was just being siilly, nevermind

Emilio Pisanty

@Anonjohn Yes, that is likely. As I said, you need to double-check against the literature in the comments to the question.

Anonjohn

@EmilioPisanty I have edited my answer, and have shown the nice bound. I will probably follow up and edit my own answer.

Emilio Pisanty

10:32

@Anonjohn also, note Ruslan's comment on the question and my response to it

Bernardo Meurer

@JohnRennie Should the function pointers for state operations be inside state or in game? Things like adding a new element to the list or counting elements or w/e

Emilio Pisanty

specifically re this paper doi.org/10.1103/PhysRevA.67.012704

Anonjohn

@EmilioPisanty Okay! Thanks!

John Rennie

@BernardoMeurer That's why I was wondering about wrapping the linked list in it's own struct. It would make sense for the functions that manage the list to be in that struct. The only thing is that this is all getting quite complicated.

Emilio Pisanty

@Anonjohn note, though, that your potential-energy curve does not really provide for the existence of a bound state

Bernardo Meurer

10:36

@JohnRennie True

Hm

Emilio Pisanty

the slope is always negative, which means that the antiproton would get repulsed, and there's no three-body bound state

Anonjohn

I haven't really plotted any potential energy curve. Tried a variational minimisation!

@EMilio

Emilio Pisanty

@Anonjohn yes, but your variational minimization is insufficient to show the existence of a three-body bound state

if you had a region in $c$ where the minimization showed the energy was smaller than $-1/2$, then you'd be in business

your results show that it's possible for the electron to stick to the proton and for the antiproton to go on its way, which is not what the question asks for

Anonjohn

@EmilioPisanty Aaaah.... I see what you mean.

Emilio Pisanty

Now, it's not fatal, because the variational minimization provides a bound for the ground-state energy but not an estimate

but the bound is not strong enough to show anything

however

you can probably provide a much better bound if you allow a test function with a small mixing of $2p_z$ wavefunction

that would allow the electron cloud to polarize in response to the antiproton, and you'd be modelling the real physics with some accuracy

and then you'd have a variational-minimization argument that there is indeed a Born-Oppenheimer well for the antiproton

Anonjohn

10:41

@EmilioPisanty I have done exactly that(The p_z wave function) and reduced the bound, but only by very little! This seems much harder than i originally thought.

Emilio Pisanty

(that's still not enough, by the way - there are wells that do not support bound states, so showing that there is a well doesn't get you there)

@Anonjohn ok, fair enough

keep at it, then

Anonjohn

@EmilioPisanty There are? Like what?

Emilio Pisanty

but as I said, do have a look at this one, it probably contains a full answer

@Anonjohn oh, plenty

any well that's shallow enough

if you want a simple example, try a shallow finite square well

Anonjohn

@EmilioPisanty Thats very interesting! Thanks!

Bernardo Meurer

@JohnRennie I guess the only fucntions we need is to count the elements on the list and to transverse it

and these are direct game actions pretty much

so they can just be function in the game struct

Emilio Pisanty

10:47

@Anonjohn btw, your ansatz in that edit is still too rigid. You should allow for a weighed superposition of the $s$ and $p_z$ wavefunctions, with the amplitudes depending on $c$. Plus, the $p_z$ wavefunction should probably read $r\cos(\theta)$ rather than just the bare cosine.

Anonjohn

@EmilioPisanty Thats sensible advise. Thanks!

Ben Niehoff

12:21

@0celouvsky I've just been super busy...have a paper coming out soon!

0celouvsky

@Secret Triangle inequality + replacing the $||e_i||_2$s with the largest one.

Secret

Ah I see, all clear now

Emilio Pisanty

man, if that had been dated two days ago it would've been so much more awesome

0celouvsky

Why?

I watched that video too

Don't know why

Emilio Pisanty

@0celouvsky an April fools' video that had a "battery juice" factory, say, next to an orange-tree farm?

Secret

12:33

Juice battery powered clock

►

old

0celouvsky

Lol

Secret

12:50

[Rallying all quantum guys=Acuriousmind, Emilo Pisanty, yuggib, Danielsank, Heather, Accidental Fourier transform, Ben Niehoff, bolbteppa, Qmechanic, vzn, rob] I have two quantum conceptual questions. I appreciate you guys help on clarifying them, thanks

0

Q: CHSH correlation function. Does it only works for observables with precisely two possible values?

So today in trying to understand more about the CHSH inequality and how a combination of $C_{NOT}$ and Hadamard gate will form the triplet bell state $\frac{1}{\sqrt{2}}(\lvert ++\rangle + \lvert --\rangle)$ with input state $\lvert ++ \rangle$, I decided to pick a rotation operator $R(\theta)$ i...

0

Q: Difference between PR correlations and entanglement correlations?

Recall that for classical correlations, the observables are already determined even before a measurement, and thus knowing information of one subsystem will immediately let you know the corresponding information in another subsystem. For correlations in entanglement, suppose I take the singlet b...

quantum-mechanics non-locality

0celouvsky

13:03

Why is heather in that list?

Secret

because she has rather strong background in quantum computing as demonstrated in her PSE, and it just happens one of those questions above is also a quantum computing question

Meanwhile, dmckee and Slereah are not on that list since past experience told me they are more matching when the question is QFT or particle physics and not (non relativistic) quantum

I am actually not sure if Tanmaths is on that list, because his background is strongly focused on quantum biology which does not always touch upon the more mathematical side of quanutm

(Besides the quantum guys, I also have other lists such as the GR guys, chemistry guys, maths guys, particle guys, and so on...)

Secret

13:25

Of course, the list above are the regulars I knew in this chat, there might be more people in the main site that fit into that list

Emilio Pisanty

13:49

@Secret You know that if you don't @tag people, they don't get notified, right?

Secret

That's true, but given the size of that list, that will be way too many tags...

Emilio Pisanty

just sayin'.

Secret

I have yet to find a good way to solve the "too many tags problem"

Emilio Pisanty

@Secret first question is entirely unclear to me

ditto for the second question

however, your claim that

> [for quantum states] the correlation is on the level of the wavefunction

is at best interpretation-dependent

it's certainly not true from an operationalist viewpoint

Regarding PR boxes, though, it's not clear to me that the answer actually exists

but good luck with your question though

Qmechanic

@EmilioPisanty : It seems that the question has zero physics content, and are off-topic on Phys.SE. (One could argue that it should be a software recommendation question, but these are limited and already have N duplicates.) If not Mathematica.se (which I in hindsight agree is not ideal; whether it is free or not is usually not a valid criterion when discussing recommendations), what other migration site would you suggest?

Emilio Pisanty

14:14

@Qmechanic off-topic for phys.se does not imply on-topic for other sites

Discussion of other migration targets is moot at this point, though

Secret

@EmilioPisanty Operationalist interpretation is new to me, after some brief read about it in quantum diaries, if I understood correctly, I am guessing under that interpretation, since concepts are defined via measurement, the observables only became defined under a measurement and hence the correlations in entanglement will also be in the level of observables, and not the wavefunction. Apologies if I misunderstood

Emilio Pisanty

I feel that it's not a great question but that it's on-topic here. If folks felt it wasn't then I think the correct thing would have been a pass through the close review queue

Secret

I am happy to be clarified on how entanglement works under that interpretation, since wikipedia does not seemed to have that interpretation on the list (unless it is under a different name)

Emilio Pisanty

@Secret that understanding of the interpretation is ok. Not brimming with finesse but overall ok.

Interpretations of quantum mechanics

An interpretation of quantum mechanics is a set of statements which attempt to explain how quantum mechanics informs our understanding of nature. Although quantum mechanics has held up to rigorous and thorough experimental testing, many of these experiments are open to different interpretations. There exist a number of contending schools of thought, differing over whether quantum mechanics can be understood to be deterministic, which elements of quantum mechanics can be considered "real", and other matters. This question is of special interest to philosophers of physics, as physicists continue...

but the explanation is terrible

my go-to place for these things is this lecture

Rob Spekkens - Foundations of quantum mechanics - QuICC Lecture 1

►

from ~25min onwards ish

0celouvsky

Why do we need to interpret quantum mechanics?

Emilio Pisanty

14:22

also from ~51min or so

lecture slides at dropbox.com/s/8c1vawj6pp6izzv/SpekkensQuICCLecture1.pdf?dl=0

@0celouvsky because math does not exist in a vacuum?

because the usual postulates are either incomplete or inconsistent?

see that lecture for details

Naveen Balaji

Hey guys!

user129412

Could anyone help me find a nice diagram that shows me how the gates around a nanowire can define a quantum dot? I'm thinking of a structure like this i.imgur.com/pg9Gnnx.png (the outer two parts are leads, the inner are two tunneling gates and a plunger gate). I don't really see the potential landscape that defines the dot, in contrast to say, having two QPCs in a 2DEG

0celouvsky

@EmilioPisanty how many people actually have to confront the foundations of quantum mechanics in an experimental setting?

Naveen Balaji

Just wondering if there are any "Gravitation" equivalent book in QM

0celouvsky

Book that everyone says is the Bible, but no one has actually read?

Naveen Balaji

14:28

Yeah

Emilio Pisanty

@0celouvsky if you're OK with the theory not actually making sense, then you can just happily sail on

Naveen Balaji

Some parts are amazing in the book, but some are just far too advanced

0celouvsky

maybe Cohen-Tannoudji

Naveen Balaji

Ahh right

That's way outta my budget

0celouvsky

MTW isn't??

It's like $200 used

Naveen Balaji

14:30

My parents got that for me.

0celouvsky

One of my profs has a copy. I need to get onto his will for that thing

Naveen Balaji

Now, I am trying to buy some for myself from the bucks I saved

0celouvsky

Don't do QM

Get some math books

Physics Meta

-1

Q: Reputation suddenly reduced: got no reason

I had a reputation of 126. However, it got reduced to 124 due to a negative vote on an answer. Now I see it has become 116, though I could find no negative vote in my activity page. Can the moderators, or the ones with greater reputation take a look and explain how this happened? Help is great...

support reputation

Naveen Balaji

@0celouvsky What do u suggest

0celouvsky

14:35

do you know analysis of a single real variable?

Naveen Balaji

And the QM book is not for me, buying it for a friend

Secret

For me, measurement is weird. Why and under what conditions will an interaction has to behave like a projector and thus becoming a (von neumann) measurement

Anything else seems rather ok to me when I adopt the $\psi_{ontic}$ interpretation (that the wavefunction is some real, but nonphysical object as defined [here] (https://arxiv.org/abs/1311.7127)

Sometimes the equations for decoherence reminds of many worlds, because its like when the observer/measuring device became a subsystem of a larger entangled state, then subjectve to that device, it sees a well defined eigenstate, but because t…

Naveen Balaji

I need some books for pure maths that I am trying to learn

Any great introductory books?

Bernardo Meurer

@NaveenBalaji What part of pure maths

0celouvsky

@NaveenBalaji abbott

Bernardo Meurer

14:39

Kolmogorov's analysis book is nice

Naveen Balaji

@BernardoMeurer That's the thing I don't know where to start

Secret

I recall in susskind's QM theoretical minimum, he highlights this equation and note how it is actually an entanglement and tell the reader to think more about what that implies

Reading the notes so far Hmm interesting, it seems I might be unawaringly using some of the operationalist approach after all, due to how I always ask how to write a measurement operator so I can do a dry experiment by putting the maths symbols in the right way

0celouvsky

@NaveenBalaji Abbott

Naveen Balaji

@0celouvsky Any good group theory books you know

Yeah just checked out Abbott , buying it

Emilio Pisanty

15:05

@Secret If you assign any amount of ontological reality to the wavefunction, then you're not an operationalist

what you describe there is not what 'operationalist approach' means

Secret

I stand to be corrected, I am currently on the 37:26 mark of the lecture, but thanks for notifying my errors

(yeah ever since that arxiv article, I have a tendency to treat the wavefunction as some "stuff" just like fields and other things. Therefore it is not suprising I get a wrong impression on operationalist and other non psi ontic approaches)

0celouvsky

@NaveenBalaji what kind of group theory?

What you probably mean by group theory is not what I (as a mathematician) would call group theory.

You probably mean representation theory

For that, the standard books are Fulton & Harris, Hall, and Helgason.

But those are probably unintelligible to you right now.

skull petrol

as a mathematician?

0celouvsky

Oh, and Bröcker & tom Dieck.

@skullpetrol Yes?

skull petrol

I've never seen you call yourself that pal.

0celouvsky

15:17

Only all the time

skull petrol

-_-

0celouvsky

Mar 4 at 21:31, by 0celo7

@BenNiehoff I'm a mathematician.

Feb 15 at 16:43, by 0celo7

@ACuriousMind I'm a mathematician

Bernardo Meurer

@skullpetrol He's 100% a mathematician

0celouvsky

Oct 10 '16 at 23:26, by 0celo7

@heather I'm a mathematician. I don't know about quantum computing

@BernardoMeurer More like 50%

skull petrol

49.999...%

Bernardo Meurer

15:19

@0celouvsky In soul you're just a mathematician

You have an engineering major for GDP's sake

but you are a mathematician :P

skull petrol

mathematician

Noun: mathematician (plural mathematicians)

An expert on mathematics.

AccidentalFourierTransform

buuuurn

0celouvsky

@BalarkaSen what is this and why did Amazon put it in my recommended list?

Slereah

I thought @0celouvsky was an engineer

0celouvsky

@Slereah I am

Balarka Sen

15:24

@0celouvsky vOv

Slereah

Trust me, i'm an engineer !

►

Secret

(48:23) The issue I have for many worlds is that besides the problem of how probability is assigned, there's also this personal identity problem

Suppose the measurement device measures the spin of the electron. Therefore by many worlds, all possible outcomes are generated in a superposition and mutually decohere from each other. Now let's say the probabiltiy to enter the spin down branch is 0.5 and 0.5 for the spin up branch, *which* meansurement device enters which branch, and what will another measurement device detect when it tries to check the output of that other measurement device...?

0celouvsky

48:23?

Are you writing bible verses?

Secret

Rob Spekkens - Foundations of quantum mechanics - QuICC Lecture 1

►

my current location in this lecture

skull petrol

Lol @0celouvsky

Secret

15:25

also I don't think that stuff look like bible either

bible is a lot more poetic than that

0celouvsky

Did Julian Springer really like Yellow?

Why are all the springer books yellow

skull petrol

Quantum bible?

To make them stand out @0celouvsky

Slereah

Maybe it's a marketing thing

Recognizability

skull petrol

^

Slereah

A lot of physics books from other brands are green or white

Or black

0celouvsky

15:29

what other brands are there that have a distinctive color

skull petrol

Bibles.

AccidentalFourierTransform

apple

0celouvsky

for books

AccidentalFourierTransform

.... for dummies

Slereah

Is Princeton mostly shades of red?

0celouvsky

15:30

Their lecture notes series is all red/orange, yes

Emilio Pisanty

@Slereah yes, it's been known as a communist hotbed since the early 20th century

skull petrol

Little black books are always black.

0celouvsky

Under what circumstances does one even have converging fourier series in $\Bbb R^n$

skull petrol

...and little.

Slereah

Cambridge seems to be shades of blue

0celouvsky

15:39

Yeah, HE is very blue.

Slereah

Maybe they switched colors since the 70's

0celouvsky

> Let H be a separable Hilbert space with complex inner product ⟨·|·⟩.

What is this, physics?

Slereah

HE and Birrel Davies are yellow

Stephani, Kinks and domain walls, and Rovelli are shades of blue

0celouvsky

Aha!

Ben Niehoff

Princeton should be orange and black, I think

their mascot is a tiger

0celouvsky

15:43

I need that fourier analysis book

Slereah

Milner's book on communication algorithms is grey, though

0celouvsky

Why do you have a CS book

Slereah

maybe they don't have any obvious color pattern

I like CS?

0celouvsky

y tho

Slereah

It's software development I don't like

CS is p. much math

0celouvsky

15:44

I thought you were a software dev

Ben Niehoff

well...there are many clothing stores across the street from Princeton selling orange-black striped ties

Slereah

Yeah

And I don't like it

Ben Niehoff

to go with their blue blazers and Sperry topsiders

Slereah

Also I'm guessing some editors leave the freedom to choose covers to their authors and some don't

I'm guessing O'neill didn't get it

0celouvsky

@BenNiehoff the nutshell books are black

Ben Niehoff

15:46

lol, I have a LaTeX Beamer presentation I'm working on that literally takes 10 minutes to compile

0celouvsky

@Slereah maybe he's just a scrooge

ACuriousMind

@BenNiehoff What on earth did you put in there?

Ben Niehoff

@0celouvsky oh, I didn't know we were talking about books, I thought it was just school colors :p

0celouvsky

context boiiii

Ben Niehoff

@ACuriousMind Lots of fancy TikZ diagrams

Slereah

15:47

This is the cover I want for my book

Ben Niehoff

Image not found

brilliant!

ACuriousMind

Ah, "image not found", a classic :P

0celouvsky

I see it...

It's dinosaurs

Ben Niehoff

is the back cover a red X?

Slereah

Yeah for some reason the picture loads and then a few seconds later becomes image not found

I think the site has some anti hotlinking thing

0celouvsky

15:48

...I still see it

did I break PSE

Slereah

Emilio Pisanty

is it me, or is this pretty funny?

skull petrol

Lol

0celouvsky

He's a robot

Ah, the cube is compact

Isn't it nice how things always work out like that

Slereah

\begin{eqnarray}
[\h \omega_{\alpha \beta} M^{\alpha \beta}, P^0] &=&-{\omega^0}_\nu P^\nu\\
[\h \omega_{\alpha \beta} M^{\alpha \beta}, P^1] &=&-{\omega^1}_\nu P^\nu\\
[\h \omega_{\alpha \beta} M^{\alpha \beta}, P^2] &=&-{\omega^2}_\nu P^\nu\\
[\h \omega_{\alpha \beta} M^{\alpha \beta}, P^3] &=&-{\omega^3}_\nu P^\nu
\end{eqnarray}

0celouvsky

15:51

stop

Emilio Pisanty

@0celouvsky there's no evidence Qmechanic is male

Slereah

For some reason this fucks up in my document

y

Emilio Pisanty

(so far as I know)

0celouvsky

@EmilioPisanty no women on the internet

Slereah

(\h is a shortcut I use for \frac{1}{2})

ACuriousMind

15:53

@Slereah In what exact manner does it "fuck up"? :P

0celouvsky

@ACuriousMind oh god what is your new avatar

skull petrol

An improvement

0celouvsky

the best cover is amazon.com/Panoramic-View-Riemannian-Geometry/dp/3540653171/…

ACuriousMind

@0celouvsky Fall-from-Grace

Slereah

AccidentalFourierTransform

15:54

neeeeeeeerd

Slereah

@0celouvsky played Torment 2 yet?

0celouvsky

@Slereah what the heck is that?

@Slereah never heard of it

AccidentalFourierTransform

nice massless particles you have there

Emilio Pisanty

@Slereah what's \h there?

Slereah

2 mins ago, by Slereah

(\h is a shortcut I use for \frac{1}{2})

AccidentalFourierTransform

15:55

why dont you just type \frac12

Slereah

@0celouvsky just came out

@AccidentalFourierTransform too long!

0celouvsky

@Slereah do \tfrac12

Slereah

1/2 comes up a lot in physics

AccidentalFourierTransform

then type .5

Slereah

Even worse

0celouvsky

15:56

either that or fix the damn brackets

ACuriousMind

@Slereah no spoilers please

AccidentalFourierTransform

also, dont use eqnarray please

2

be professional

Secret

And I have finished listening to the lecture. So, I actually have some quite philosophical questions about operationalist vs realist approaches

So, if I understood correctly, for operationalists, rather than talking about physical states, they talk about settings of the lab instruments, which then when the experiment is ran, quantum mechanics gives the rules on predicting the probability of the outcomes

Whereas for realists (many worlds, psi ontic, bohm, (rest forgot)), the wavefunction is a physical property of the physical state ,which evolves determinstically according to the SE and th…

Slereah

align?

ACuriousMind

@Slereah Well, your first error is that you're using eqnarray. Avoid eqnarray!

AccidentalFourierTransform

15:57

align is fine

but equation+aligned is the correctest way to do it

0celouvsky

Huh, Riemann actually defined Finsler manifolds instead of Riemannian manifolds

He then wrote

> We will now stick to the case of ellipsoids [quadratic forms] because if not the computations would become very complicated.

Slereah

Well it's considered very conceited to name something after yourself in math

skull petrol

in anything

0celouvsky

@Slereah He didn't name them anything

he defined a more general structure first

Transcript for