Hi, everybody.

phdcomics.com/comics.php?f=1481

heheh

← has no idea either en.wikipedia.org/wiki/Shoshin

@JohnRennie did someone say "soliton"? =D vzn1.wordpress.com/2017/09/08/… (newly added quotes by DS, JR, ACM etc!)

@vzn

> DS is also on the (chat) record as averse to/ strongly rejecting “alternative interpretations”.

Reference needed.

Also...

> which to me is not really scientific,

Yeah, well, neither is a pretty hefty chunk of the stuff you say around here, so I guess we should get along pretty well.

@Blue Nah, he comes to my place for that.

@DanielSank lol yeah we get along famously as the expr goes right? :P

@vzn Yeah, Batman and Joker but I'm not sure who is who.

@vzn Uh, yeah, I stand by that statement.

Okay

So

I spent the whole day testing all the top BSD's on distrowatch

here's my findings:

I've noticed a number of the theorists at my university have been using iPad Pros for their class notes e.g.

FreeBSD just works, the packages are old, but it install easily, and works well. TrueOS (PC-BSD) works as long as you don't mind the ugly UI, trying to run Gnome+GDM didn't go well. DragonFlyBSD works OK, but the HAMMER filesystem is not for the faint of heart. Net BSD works well, don't even bother with the UI IMHO, runs on EVERYTHING. OpenBSD I didn't bother to test, has the best security by far though, probably should be used just for servers

Also, boot on DragonFly is slow

I also tried VoidLinux, but configuring the rootfs with BTRFS caused Grub to fail

All tests ran on VirtualBox using KVM and Virtio

Trying Void Linux again, this time with a different bootloader config and partitioning

Also all tests ran on EFI

and GPT disks

Conclusion: Just use FreeBSD. If you have a lot of super fast storage use DragonFly and have backups

Note: FreeBSD requires you to do some manual network configuration, it;s simple though

Ok

What do I do now?

I'm just bored

Hello. I don't know about Noether's theorem.

But is charge conservation a result of energy conservation?

Imagine two charges (q). One is at the origin and the other one is at (0,r). Now if suddenly the charge on on one of them or both of them changes, the energy suddenly changes. And I think this cannot happen...So Energy Cons => Charge cons

?

@JohnRennie are you a chemist?

I have some questions about calculations in MOPAC; if you are interested in..

(or anyone)

@HernanMiraola Hi :-)

@JohnRennie :) hi

I am (was, I'm retired) a physical chemist and more specifically a colloid scientist.

I specialised in theoretical chemist at university but that was 40 years ago and I'm afraid I don't know much about modern quantum chemistry packages.

what a pity, I will have to keep looking for help haha

@HernanMiraola Incidentally, re your question I'm not sure what you were getting at in your comments to my answer.

I am trying to calculate standard gibbs free energy for aqueous reactions..

Free energy change you mean?

In principle Gibbs free energies are absolute, but to get the absolute value would mean integrating from absolute zero through several phase changes so in practice we never use absolute values.

About the comments, I was asking if all in physics needs a relative point; I think gibbs free energy, needs it

relative point=reference

As a general rule physics only measures energy differences/changes so we aren't fussed where the reference point is.

As you said ina comment we tend to fix zero energy when everything is at infinity.

so, there isn't any absolute free energy..

Well the Gibbs free energy is by definition G = U + PV - TS

I am a bit confuse cause I have seen: G=H-T*S..

yes..

H = U + PV

but U is relative to some reference..

(as in your answer)

Yes, pressure, volume and entropy all have absolute definitions but the value of the internal energy depends on exactly how you define it.

But apart from ideal systems like an ideal gas it's impossibly hard to calculate absolute Gibbs free energies anyway.

But, anyway, absolute energies, if G depends on U, doesn't have any sense

I apologize if am misunderstanding..

I am sorry

relative energies

You're correct in the sense that the choice of zero internal energy is arbitrary.

And as G is defined in terms of U

I suppose absolute G doesn't have sense..

But energy changes are always well defined, so when you're calculating the Gibbs free energy change for your reactions that's a well defined quantity.

I have a huge disorder with all this

Really? Why?

Well..I don't know even that..when we chose U=0 at infinity (in sch equation)..

what is the meaning? I mean, atoms have internal energy..

It means only: if you have those atoms that is the energy to go from one state to the other?

OK, but in a chemical reaction the internal energy of the atoms doesn't change. So when we calculate the energy afterwards and the energy before the contribution from things like the internal energy of the atoms is the same on both sides. That means we can simply subtract it from both sides.

But we can compare U of two different systems?

Suppose we write the Gibbs free enery as G = G' + X where X is all the stuff like energy of the atomic nucleus etc that we can't calculate and G' is the enthalpy, entropy etc that we can calculate.

(molecules)

Yes I understood what you said..

(nice point of view)

Yes I understand that, you are right. But I have listen lot of times..

This is more stable than this

and X is different

You're saying that maybe X(after) and X(before) are different?

No..suppose molecule A and another molecule B

So, we can calculate G from atoms to molecule

OK ...

G(A)=G'(A)+X(A), and then G(B)=G'(B)+X(B)

Can we compare stability?

OK but we have the same number of atoms before as we have after. The numbers and types of atoms present doesn't change.

And X is the energy of those atoms separated to infinity.

but it is not a reaction

So, by definition, X(after) and X(before) are the same because they are the energies of the same atoms in the same conditions (separated to infinity).

wait..

Suppose we have oxygen, and nitrogen

we calculate from QM the internal energy and somehow G

for oxygen

and G for nitrogen

can we compare G(ox) with G(nitrogen)?

(Is this chatroom a place to talk about all this? I am sorry i'm new on this sites)

You're thinking of some reaction like O2 + N2 -> 2NO ?

No, I am thinking only about the molecules

O2 and N2

without reaction

when a chemist says, 02 is stabler (I don't know if the word stabler exists) than N2, what does he implies?

I suspect that means the Gibbs free energy of formation of O2 is less than the Gibbs free energy of formation of N2.

But..

We don't need to know anything about the atoms? Can we compare those systems?

we have O and O at infinity; it is not the same as N and N..

For any diatomic the energy of formation is the energy change when two atoms initially separated to infinity combine to form the molecule. So it's an energy change by definition.

Yes I agree with that..

So when comparing the energy of formation of O2 and N2 we are comparing two energy changes.

We are not comparing any absolute values.

so on earth only exist changes (?..I don't know why I wanted to say that..

I know there is still something I don't undestand about that, but it is much better..

thanks..

As a general rule we can only ever measure changes and not absolute values.

And only the entropy is an absolute value?(in theoretical world..)

and, for example, kinetic energy? Isn't that measure absolute?

I suppose even entropy is relative. For example there is presumably some entropy change when we form an oxygen nucleus from eight protons and eight neutrons, but we don't normally count that in our calculations of entropy.

Kinetic energy is relative too because it depends on how you define your stationary point. For example what is the kinetic energy of the Earth?

but if I measure it with temperature?

of a gas..

@HernanMiraola If you're using KE to measure the temperature of a gas then we say the centre of mass of the gas is stationary i.e. we measure the gas molecule velocities relative to the centre of mass of the gas as a while.

@JohnRennie I was saying the opposite, measure KE with Temp, but it might be the same

@HernanMiraola In both cases we make a choice of reference point for measuring the velocities.

But is it the same a reference point and a reference state?

I mean, Gibbs free energy is not absolute because we measure changes (from experimental point of view)

OK ...

and from theoretical point of view..is not absolute because..

we need a reference..

point?

(I might be really confused)

Absolute just means there is some unambiguous reference. For example volume is an absolute quantity because we all agree on the meaning of zero volume.

Likewise pressure is absolute because we all agree on what zero pressure means.

mm..I am not sure..for example..

So the difference between absolute and relative is really just a matter of how obvious the reference is and whether we have the freedom to choose different references without changing the physics.

what if I say, absolute is because we dont need that the variable change to measure it..

we can measure presure but don't need the system to vary its pressure..

Well take pressure. That's obviously an absolute quantity, yes?

mm..anything is obvious for me..

haha, but yes

OK, but when you measure the air pressure in your car tyres you're actually measuring the pressure relative to atmospheric pressure.

So even for an obviously absolute quantity like pressure we sometimes measure it in a relative way.

Yes but I don't need the systems to change

Oh, how is italic here?

Put * either side of the word

e.g. write *change* to get change

No spaces between the * and the character next to it

:) thanks

Anyhow, re pressure, what we are actually measuring is a pressure difference.

All the pressure gauges I can think of work by measuring a pressure difference.

But, yes, in principle you can measure an absolute pressure.

So that is different from Gibbs free energy where you can't measure the absolute value of Gibbs free energy.

How'd you put * change * without space and still didn't get it in italics?

maybe..**change**

no..

change

change

yeah that just puts things in bold

magic!

lets try!

link text

physics paper of the month

haha oohh

big band theory

Welcome to $\hbar$!

gah that didn't work

@Avantgarde MathJax isn't enabled by default in chat.

Oh yeah, I missed the "\" in hbar

works now

Ah

But how did you sandwich the asterisks between a word without getting them to italicize?

/italicise :P

Use backquote ` to surround what you type

ah got it

@JohnRennie and we can't also estimate absolute G..

@HernanMiraola the point is that we never care what the absolute value of G is because we can never measure it.

hmm..

yes..

well..I'm leaving..

goodbye and thanks a lot..@JohnRennie

Anyone experienced in Python? It took me 0.6s to find the first 50k prime numbers. I need it to execute/print the output faster.

My code is alright. I'm looking for a faster IDE (is that what you call it?)

You mean the IDLE I have? That takes forever! Sublime Text is way quicker (that's what told me the time taken to finish execution)

It's called Python Shell. I think that's what you mean

@Blue If you mean this - diveintopython3.net/i/ubu-interactive-shell.png

Then that takes painfully long to print the numbers.

But Sublime Text is just a text editor. I need something where I can get the output too. Inputting something from the user, for example, is not available on Sublime, by default

@Blue lemme check

@Blue That's what I had done initially.

Oh I have to use python. It's fine, doesn't matter

hey @AccidentalFourierTransform

facebook.com/memesdefisica/photos/…

ah, here it is

CC @DanielSank

@vzn If you didn't just quote-mine, you'd realize that JR's quote is a play on Asimov's First Law and a joking response to me alluding to said law, and that there was no serious disucssion of quantum interpretations at all around at that point. If you wanna quote people from here, taking jokes out of context is certainly not the best way to go.

@EmilioPisanty Is that like "Hitler learns topology" but "Anakin learns physics"? :P

@Kaumudi.H You're welcome to lurk and delurk as you please ;P

@Kaumudi.H you don't already lurk?

@ACuriousMind hmmmmmm, close but not quite

he's telling the story of Richard Feynman "The Bongo Player"

and how he was capable of studying the quantum electrodynamic vacuum and perturbing it

but unfortunately he was incapable of not getting eaten by a bear

@ACuriousMind apparently windows just removes the password

seems like an awful feature

like...seriously terrible

@EmilioPisanty have you actually looked at Springer's "applied mathematical sciences" series?

it's all pure math :D

@0ßelö7 nope

@Blue I'm reading a paper by someone at IIT

Does that mean he did the JEE?

yeah

you've downgraded

@BalarkaSen Downgraded?

@0ßelö7 You mean your account became entirely unprotected by a password? oO

for reading a paper by someone who took the JEE

@Avantgarde this is a refreshing talk

i don't know if you care about it but pinging anyway

@0ßelö7 It forces the user to change the password regularly but you can disable it.

@ACuriousMind Yup. Computer woke up by itself and when I got on to see what was up it said password expired and I just got in

Like I always put it in sleep mode but at 4AM the lights and fans came on

Woke me up

@BalarkaSen it's a physics paper, so make of that what you wish

@0ßelö7 $\text{JEE}>\text{GRE}$

I think we have a trol

I just apparently saw my neighbour who's been living there for since we moved...

Swear to god I've never seen the man in my life

He's been hiding from you. Either he is a psycho or he thinks you are.

All I know is that he's called Bob

sounds like a pseudonym to me...

arxiv.org/pdf/1707.03811.pdf

The humour of mathematicians

@Blue it looks like a good paper

@Secret meetings.aps.org/Meeting/MAR15/Session/S48.8

> We build up to a full scale simulation of an outbreak in the United States, and discover that for `realistic' parameters, we are largely doomed.

lol

yeah, I know

I was there at the meeting but I couldn't make that talk =|

I will be quite interested to see how the zombies spread according to their model. If they found that we are doomed for so many parameters, then chance are the spread must be extremely rapid and multidirectional

@Secret not necessarily

aps.org/meetings/march/vpr/2015/pressreleases/upload/zombie.pdf

@CooperCape dear god

@BernardoMeurer see above

@CooperCape if that's the bob I think it is, run

Oh... oh Goodd

If you never hear form me again... actually you'll probably be glad less badly worded misunderstood questions...

@CooperCape does he have a dog?

ahhh nope

@Secret a classic paper

Now to make the zombie elements to wander so that they behave like actual zombies...

@BalarkaSen Thanks for the link

Not really, but I will get to Eno's music sometime when I get time. When I'm in the mood for some ambient stuff. My first impression was good

he has a huge musical palette, not just ambient things, even though ambient appears most prominently

@Kaumudi.H If you count bad ones, sure. If you need help, I can try.

I'd check out his latest release if he moves into black metal :P

lol

black metal is pretty dank

So happy you said that

'Zeno effect' verified: Atoms won't move while you watch / cornell chronicle

> Using this tuning, we’ve also been able to demonstrate an effect called ‘emergent classicality’ in this quantum system.” Quantum effects fade, and atoms begin to behave as expected under classical physics.

@0ßelö7 He's going to come with his 1,000 Lumen SureFire R1 Lawman flashlight

@BernardoMeurer not even you can hate on this deal i.gyazo.com/2350c9ddc1be997116e901ae731d841a.png

@0ßelö7 No, go for it

Buy me Shankar

@BernardoMeurer already did, it's coming tomorrow

that book, not Shankar

Shankar is too expensive

:(

@ACuriousMind and other other QFT aware chat room members. Could the coupling of a particle field to the Higgs field be negative, and if so would that give a negative rest mass to the particles of the field concerned?

(If this is a really stupid question say so within the two minutes I have to delete it :-)

@JohnRennie Consider that the parameter that appears in the Lagrangian is $m^2$, not $m$, so it is unclear how a negative mass could enter into a Lagrangian to begin with, regardless of the Higgs mechanism or any other details.

@ACuriousMind what the hell does cohomology have to do with number theory?

@ACuriousMind $m\in\Bbb R\mathrm i$

@ACuriousMind Isn't the mass term you get from the Higgs field something like $yH_0$ where $y$ is the coupling constant and $H_0$ the Higgs VEV?

@0ßelö7 How am I supposed to know that? I don't know any number theory at all

@ACuriousMind you know cohomology

@JohnRennie The term in the Lagrangian is $yH_0$ - the mass is the square root of that.

@0ßelö7 That's imaginary mass, i.e. tachyons, not negative mass

@ACuriousMind Ahhhh, oops.

I thought there was that post by Qmechanic that said tachyons had nothing to do with imaginary mass

@0ßelö7 No, you're thinking of the post that they don't need to be FTL

@ACuriousMind if it's not a silly question, why do we exclude the negative square root? Just because it's an obviously sensible thing to do, or is there a more fundamental reason?

I'm asking because of this question

Gah. I really need Reed and Simon Vol 4 and someone has checked it out from the library

@JohnRennie I don't know any other answer than "the things we observe don't have negative mass, so we don't consider it"

> $180 paperback

@ACuriousMind So the Higgs mechanism could be responsible for a negative mass, if we take the negative root? If I answered the question pointing that out would that be a correct (if somewhat silly) answer?

Elsevier is somthing else

@JohnRennie Frankly, I'm not sure what "negative mass" even means on the level of QFT

$$\lim_{x\to 1-0}s(x)=C$$

wot

That is, I don't know if a QFT in which you have states with negative mass is consistent

Thanks :-)

@yuggib Kato has everything. My god, this book...

@0ßelö7 Literally I hope; that book should be your god ;-P

@yuggib it seems to be a better reference for functional analysis than the books titled functional analysis!

@Sid Yes

@Abcd Indian English is not proper English outside of India.

@0ßelö7 Hmm, I agree. You won't believe me but I stopped using this word last year. But all my friends say it over and over again, so I started using it again in that sense :(

I say it ironically now. But you should say question.

@0ßelö7 Any other word? Btw, I never used "doubt" on Stack Exchange.

I think that's the major complaint

@0ßelö7 What? I didn't get you...

What?

@0ßelö7 What is the "major complaint"?

Indians saying doubt

i have ze dowt

@0ßelö7 Your prof told "doubt" yesterday, right?

That has become proper English, obviously, now. :P

i think it's a cringy word in the context of "i have a question" honestly

but doubt is a fine word otherwise

"Deep into that darkness peering, long I stood there wondering, fearing / Doubting, dreaming dreams no mortal ever dared to dream before" - a Poe boy from a Poe family uses it

@JohnRennie speaking of signs of eqns having real-world implications, reminds me of the famous prediction/ discovery of the positron by dirac. en.wikipedia.org/wiki/Dirac_sea anyway wikipedia had a lot on "negative mass" as cited in original question but zero refs to "higgs"... en.wikipedia.org/wiki/Negative_mass

I like don't like think like the word like is like much like overused but anyways

@BalarkaSen cringes

I contracted level 4 cancer from writing that sentence

send me prayers

@BalarkaSen What is wrong with this sentence?

?!? o_O

> there is no evidence that the new particle recently observed is in fact the Higgs boson.

@BalarkaSen she missed the fucking meeting

looool

Now the light is on but there's no one there

@BalarkaSen she gave me one minute lmao

@BalarkaSen Ok, she said what I want can be done, but we have to meet again to discuss how

looooooool

@BalarkaSen She gave me a time on Friday but said she may or may not be there

@Blue that seems like a really terrible idea

she knows who I am

and who I'm working with

@BalarkaSen they are having a faculty meeting rn. Wonder if I can eavesdrop

@blue no that's creepy

@Blue she's Russian, whatever booze I get will not be sufficient

stop it

@BalarkaSen since when are you the voice of reason?

impossible; i have a password none can guess

namely, "iplaymincraft678%"

quick, screenshot

we don't know his email

it's likely something obscure

[email protected]

[email protected]

@0ßelö7 shit how did you know i have a gmail account

everyone has gmail

@Blue Only problem with google is they're communist

That's why I don't discuss politics via gmail