@EmilioPisanty Fair enough, you really need only linear algebra to understand the gist of quantum mechanics. It's just my opinion that having functional analysis is needed to understand some more advanced aspects of it (those that needed to comprehend the quantum research papers) as well it prepares oneself for QFT

heterodox or unorthodox (vs orthodox) pov: QM is far more than "mere" math, but it will take (many?) years to prove this... both mathematically/ experimentally... we now return you to your regularly scheduled programming :P

@vzn not sure that really says anything as of course it's more than math - it's the explanation of physical phenomena, not just math for math's sake.

not that math for math's sake is a bad thing.

@heather hi/ lol, ah! so an opportunity for clarification! my words are partly an allusion to the "subquantum" realm, speculated on by bohm etc, which is now supported by 2 cutting edge experiments, am sure more are in store. :)

If one thing, I hope the knowledge of sub quantum realm can generate a global political unrest

I need to destroy this economy and this whole system

> Total liberation from the constraints

lol! yeah! overthrow the establishment! viva la revolution! :P

Except that one revolution is not enough. We need at least 6 in the span of a single month

I guess listening takes less energy than reading.

@semiclassical Ok after 3 weeks (due to other work commitments) I finally finished reading this paper. Turns out, the only parts that are truly relevant to my interest is p.23-39, particular the part about TS reaction dynamics, which is pretty cool

arxiv.org/abs/1801.04781

Some comments:

1. I actually don't really get that part about bohmian's role in weak values

2. The chemical reactivity part is where I saw the most usefulness that bohmian may provide about information in reaction dynamics: The trajectories highlights where the nodes of the wavefunction is, and how it influence the product fraction of the probability density, which gives a lot more information than just the wavefunction alone

It also has a nice discussion between the relative rate of spreading of the wavefunction vs its propagation, which reminds of the slow pointers scenario.

3. The double slit experiment example demonstrates how bohmian mechanics are often useful to work out which fraction of the probability density goes to where, though not all systems allows such nicely separated pictures

4. I like those diagrams, especially the superposition of vector field plots with contour plots, it shows very tacitly what the wvaepacket is doing

5. Finally, I agree with you that the formalism of bohmian mechanics that is not based on the quantum potential could be more straightforward, as those sections using quantum hydrodynamics is quite confusing due to too much appeal to classical analogies

Revisiting quantum cognition models including the quantum cognition model of humour:

I wonder if bohmian mechanics can give us more information about these phenomenon. For example, mapping the ideation space and the bohmian trajectories then indicate to some extent how ideas flow around to give rise to certain class of ideas

frontiersin.org/articles/10.3389/fphy.2015.00077/full

The main difference between quantum cognition models and quantum mechanics is that a complete model of mental space is not implemented yet, thus the dynamical laws, assume they do exists, is not known and hence one cannot obtain wave functions by solving a dynamical equation. Instead, one need to somehow invert the probability distribution of the data in order to reconstruct a wavefunction, and then use that to reason about other aspects of cognition

Actually, I suspect we may never get a dynamical equation of cognitive process, because the brain is too complex that emergence can play an important role, leading to highly nondeterministic dynamics as there is no way to predict where the critical point of a complex system is without reaching there first

nature.com/articles/nphys3366

cfa.harvard.edu/publications/term/itamp/…

@JakeRose You are misreading. I'm talking about me, not you. I am the one who thinks "can read a book on qm and pretend he is a professor"... whatever. I don't know why you are so negativley turned towards me.

@JakeRose Like every sentence you write towards me is trying to discourage me or tell me I can't do something. If you have anything in mind you want to tell me, let's clear it out.

@JakeRose I may be naive, too ambitious, a bit annoying sometimes... but you don't have to be rude about it. :(

backreaction.blogspot.com/2015/06/…

I think there's also some paper back in 2016 which talked about how time dilation effects can itself be brought into superposition

leading to an uncertainty principle involving the accuracy of clocks

One thing I really really don't like when people teach laymen or beginners about the principles of quantum mechanics, is the way they word the result of the double slit experiment with a which path information detector.

It gives people a misconception that a) the uncertainty principle is a technical problem rather than a fundamental problem and

b) the whole wording making it sounds like nature is making a conspiracy, which by the very nature of human thinking, when humans are faced with conspiracy, they have an irresistible urge to want to surmount it, leading to a volley of questions like:

physics.stackexchange.com/questions/245521/is-it-possible-to-determine-the-slit-a-photon-went-through-in-the-double-slit-ex/245592#245592

physics.stackexchange.com/questions/446034/quantum-double-slit-experiment-with-2-detectors

physics.stackexchange.com/questions/146653/double-slit-information-destruction

and that is not healthy in the education of quantum mechanics to beginners and the general public

> I blame Schrodinger's cat thought experiment for this type of misunderstanding of how quantum mechanics experiments work. — anna v Jan 19 '17 at 8:00

To put it extremely impolitely, all these classes of questions about the double slits, quantum eraser and entanglements, including all sorts of different ways to do the experiment, are none other than a futile attempt of humanity in hoping to recover something that matches their classical intuition and hence an illusion of control

Morning

> Next, a circular polarizer is placed in front of each slit in the double-slit mask, producing clockwise circular polarization in light passing through one slit, and counter-clockwise circular polarization in the other slit. This polarization is measured at the detector, thus "marking" the photons and destroying the interference pattern.

> Finally, a linear polarizer is introduced in the path of the first photon of the entangled pair, giving this photon a diagonal polarization. Entanglement ensures a complementary diagonal polarization in its partner, which passes through the double-slit mask.

> This alters the effect of the circular polarizers: each will produce a mix of clockwise and counter-clockwise polarized light. Thus the second detector can no longer determine which path was taken, and the interference fringes are restored.

the bolded words need a much better rephrasing in order to avoid that human bias of considering it a conspiracy, in order to stop those volley of questions from growing

If I understood correctly from the learning experience of many people who first learnt quantum mechanics, is that they are all very uncomfortable with the notion on how superposition is destroyed when you have something identifiable from the system

Some may argue perhaps all this bias may not be that destructive, after all, we might never end up inventing weak measurement procedures without this urge to measure everything

So, we humans are weird. We are super annoyingly inefficient, but those annoyance are a necessary evil

@Slereah Mornin

quanta.ws/ojs/index.php/quanta/article/view/14/68

This review gives some motivations of weak measurements including the notion of determining the state between two measurements

@Secret agreed. i mean, i'm fine with the quantum potential playing some role---say, as a convenient device for computation or intuition. i'm just reluctant to consider it fundamental in the same way as, say, the guidance equation

@Secret are you bashing that comment (so I need to read your whole text), or are you siding with it?

@EmilioPisanty Ah apologies for the confusion, I am not bashing that comment, I am bashing the notion that implication of the OP by using time of flight information one can somehow preserve the interference. But that might be just my interpretation and bias, and not what the OP means

@Secret ah, then in that case, go right ahead

I just wanted to know whether it was something that required my attention

Nah you are fine, you knew a lot better QM than I am, so you rarely make mistakes

@Secret I still mess up, though. Please tell me when I do.

The thing I am bashing and ranting about is how generally when people taught other people about quantum mechanics, the way they describe how which path information lead to disappearance of interference fringes, makes it very easy for people to a thought process of coming all sorts of ways to preserve it and hence their classical intuition, which I found very damaging to the education of QM

i.e. people get very defensive when they first learnt the notion that measurement can disturb quantum systems, and they demonstrate that defensiveness by postulating all sorts of variations of the experimental setup in order to surmount that fundamental limitation

which, in theory ,all of that can be avoided by pointing out the link that the which path information establishes an entanglement with the detector and the particle, and hence the states can not longer form a superposition

@NovaliumCompany I’m being discouraging to the way you’re trying to learn QM. Because you’re not learning QM. You’re learning fables about QM. I’m not trying to be rude, I’m just being blunt after seeing you be told plenty of times and blatantly ignoring all of us.

@JakeRose a Kantian metaphor I'm fond of: " The light dove cleaving in free flight the thin air, whose resistance it feels, might imagine that her movements would be far more free and rapid in airless space."

Certainly fits the situation well :’)

@Semiclassical I’m not the only one right? I just feel we’ve all said it to him

/her

"Forget it Jake, it's Chinatown."

A blast from the past

I mean, I'm sympathetic to the sense of "weirdness" with QM, and I'm not averse to interpretational questions

but before you try to wrestle with those, you'd better have the formalism down cold

Exactly^^^^

@JakeRose You are correct. I didn't listen at the beginning because I wanted it to be quick and easy, but later I understood that I need to put the effort to at least understand the core basics properly that's why today I bought the book Q is for Quantum which @EmilioPisanty recommended. I will understand every single bit of this book whatever it takes.

@JakeRose I admit I was wrong and foolish but I've learned my lesson to listen to the advice of the more advanced in the field. I hope your attitude gets better although I did deserve it because I was a bit annoying.

@Semiclassical that book ^ doesn’t seem all that mathematical ;) wouldn’t it be better to start at an introductory quantum text?

@NovaliumCompany f(your comments) = my attitude

I freakin love physics so much <3

@Xosrov good

Anyone watching Man Vs Wild now? XD

What's the best thing that I can learn from you in 5 min, that can ve useful for me?

If co2 level has become highest now then why isn't the temperature of our planet also highest now

@Scáthach who told it's highest?

@Scáthach CO2 levels have been higher in the past, but in this context in the past means hundreds of millions of years ago.

@JakeRose yeah, I’m suspicious of QM which are avowedly non-mathematical. They’re not necessarily bad—I have fond memories of Jim Al-Khalili’s “Quantum: A Guide for the Perplexed”—but boy is it easy to muck that up

@Scáthach The CO2 is currently the highest it's been for the last few thousand years at least and probably longer.

Okay

So the temperature is also higher than what it was probably 1000 years ago?

@Scáthach Yes

@Scáthach no, it isn't, it Should be millions of years ago

@Scáthach We didn't have cities with millions of inhabitants built on the coast last time CO2 levels were this high :-)

@AbhasKumarSinha yeah. I misread the article XD

The dinosaurs didn't really care if sea levels rose :-)

True

@Scáthach don't get confused between Climate and Weather

@JohnRennie We're headed for a grim place though

I mean, life on Earth will presumably continue regardless of what happens. But a lot of people and a lot of ecosystems are going to get utterly f-d along the way

Hopefully we have still not passed down the critical point

@SDFG a wet place at least :-)

@Semiclassical I don't agree, the life will soon get vanished, if that isn't stopped (of course long term)

@Semiclassical exactly, and those "lot" is going to be the common people who can't buy their way out of trouble.

Yup

That isn't good.

It isn’t going to be pretty

Believe me, earth will become a beautiful place once humanity vanishes

@JohnRennie Too wet for our liking

@SDFG it's not just people. Millions of species will undergo extinct

@Scáthach As if they aren't anyway going extinct thanks to us

I do think the threat is less “existential” than, say, the threat of global nuclear Armageddon. But that’s mostly a matter of timing: nuclear winter is fast

@Semiclassical I mean I’ve only just had my second year quantum course, which has introduced me to the basic concepts in the field and even I get perplexed over the simple things unless I can bring it back to the mathematics I know

I did an atmospheric science course within the Earth sciences department last year. And let’s just say the researchers don’t have high hopes for us turning things around ;)

One of the few advantages of being old is that I'll be dead before climate change gets really bad! :-)

You lot kind of get it in the shorts though.

@JohnRennie That's very mature but sad :(

It’s fascinating in a clinical sort of way

So long as you forget that you’re in the clinic as well, anyways

@AbhasKumarSinha I'm hoping to be reincarnated as a fish, then I won't care.

@JohnRennie Is it possible to implant meteoroids inside human bodies without even touching the skin? Or meteoroids implanted themselves? m.youtube.com/watch?v=J3kP-42PDnU

@JohnRennie Their proofs and claims seem to be more realistic, full episode here: dailymotion.com/video/x4qo9kj

I got as far as the first mention of alien abduction then lost the will to live

@JohnRennie if you see full episode to understand, their proofs are solid

@JohnRennie I didn’t get past the word meteoroids in his message so you’re doing better than me

Does the Debye temperature depend on the number of moles?

@AbhasKumarSinha I fear watching it might kill more brain cells than I can spare

@JakeRose :-)

I’d suggest a “what’s the dumbest conspiracy theory you know” game but I think that’s more a headache than an amusement

@JohnRennie I fear most, because they are already more technologically advanced than us (if they are) we should work harder!

@Semiclassical XD

Alien conspiracy theories XD lol

Well it's a beautiful sunny evening in the UK so I'm going to get a beer and sit in the sun.

I'll see you all tomorrow.

@JohnRennie have a nice day :)

See this en.m.wikipedia.org/wiki/Bob_Lazar wow

I think I'm too much into alien conspiracy theories...

@JakeRose Your attitude is rude, but my comments aren't. My comments are dumb and probably annoying, but not rude. I don't know how your function works but you should fix it.

I don’t think I’m being rude. I think I’m being blunt after being excessively ignored.

I didn’t say your comments were rude?

Look

this is a physics chat room

I’m not really interested in having a squabble. You’ve said your piece and I’ve said mine.

Lets leave it there.

Alright. Let's leave it here, no hard feelings.

Hello all. I have a electronic current denisity $$\vec{J}=\frac{1}{2} (\vec{B}\times\vec{r})\rho$$, with magn. field $\vec{B}$ and electron density $\rho$ and position $\vec{r}$, I cannot make any sense of the units. Who can help?

I mean B has Tesla r meters and rho meters$^{-3}$

that gives tesla/square meter, which makes no sense.

I know J as Ampere or even Ampere/Tesla (when current susceptibility is adressed) and wiki gives me A/m^2.

but its all different ...

@Rudi_Birnbaum Could you please provide some idea of how you got this equation?

Its everywhere in the literature (i get some link in a minute) (but nowhere resolved in units)

not excatly I go for one more

Are you sure $\rho$ is current density and not electric resistivity?

it's definitely a current density from the context I know, but it may be properly a probability current density

Wait, J isn't the current density?

@NovaliumCompany (alas) theres a longrunning "friction" against popsci in this room with understandable motivations that have played out in your recent dialog. popsci is esp problematic wrt QM in many cases... however its maybe not entirely the fault of popsci...

@SDFG i may be wrong, i'm basing that statement off of earlier conversations with RB

What is $\gamma$ here?

Is it dimensionful or just relativistic gamma?

It should be the current density, but I suppose some units have been changed ...

yeah, something's goofy there

rho is usually the charge density, with units of electrical charge divided by volume

@thermomagneticcondensedboson yes

so $C/m^3$

in SI units yes

@vzn You are implying I've been annoying? Welp, I agree, but I will continue to stand behind my opinion until someone gives me a reasonable argument to think otherwise. @EmilioPisanty did that and I listened to his advice.

J should indeed yield A / m^2

yes, that would be cool

@Rudi_Birnbaum what is $\gamma$ here?

now the eqs in electrodynamics might have non consistent units (cgs vs SI for example)

$\gamma=\rho/e$

so there might be annoying factors hanging around

@Rudi_Birnbaum yuck

strange I konw

I didn't come up with that

I was looking for a neuroscience chat room like this one but I don't think there will be many users active there.

@NovaliumCompany It doesn't look like that to me - vzn seems to be making the unfounded allegation that we were bashing you for having read popular science.

@vzn To be crystal clear: there is no such "friction". The only thing going on here has been repeated polite requests from multiple sides that you clearly distinguish promotional material (i.e. press releases) from journalism when posting here, and your inability to distinguish them from an imagined conspiracy against you.

I'm truly sorry for being this blunt, but if you try to provide misinformation to new users that lack the necessary background to evaluate your comments, then there's no other option. I'm perfectly willing to have a reasoned debate about this if you are.

@EmilioPisanty with you on this one

@JakeRose take it easy on Novalium, btw. S/he clearly means we'll, and already got plenty of an earful from me and Semiclassical.

Yeah, that’s fair. I was just getting irritated by the repetitive nature of it all.

@NovaliumCompany sorry for coming off as an ass. I just didn’t like seeing you step so far in the wrong direction.

I apologize for my ignorance and annoyance towards @JakeRose @EmilioPisanty and @ACuriousMind. I reread the whole discussion and I realized how dull my acting was. Thank you for the patience and I'll make sure such time and energy consuming discussion dont pop up again.

@NovaliumCompany there's no hangups on my side. It took a while, but you eventually got it.

@JakeRose I reread the discussion and I totally understand you.

@EmilioPisanty Thank you! I appriciate it. I just cant imagine how annoying I was. If I were you, I would have given up on myself 100 times already.

I got the Ebook version of Q is for Quantum cuz delivery price to Bulgaria is as much as the book's cost.

@JakeRose I am the one who should be apologizing. :) I reread the discussion and every thing you said is exactly at place.

Now off to bed. Goodnight everybuddy.

@NovaliumCompany I can very well imagine how I would've been had I discovered this site in my high school years. No hard feelings here :) Sleep well.

@NovaliumCompany its not a crime to try to learn QM without the math. however around here it borders on one esp if popsci is involved :(

@NovaliumCompany how do you get that out of my actual words? quite to the contrary think theres been some harsh/ uncivil comments directed at you and think high rep is not a valid justification. on other hand am not taking all of your own comments entirely seriously either... anyway there are few your age that express any interest in QM and that at least is to be encouraged + even commended. :)