> Therefore, the first Chern class is either negative, or zero, or positive.

@0celo7 boo, so my answer didn't actually help then ...

@JohnRennie If you can find an adapter from that thing to a 25 pin sub D connector, we'd be very grateful

@0celo7 Like this?

mccdaq.com/pdfs/specs/serial488a_data.pdf

how much?

do I need to request a quote

@0celo7 Don't know I'm afraid. Check with your IT people first to make sure it is what you need.

where did you find that

do they have a website

The alternative is to get a 25 pin sub D card for the mobo

@0celo7 google.co.uk/search?q=ieee+488+to+rs-232

but I'm bad with computers and don't know what that's actually called

what is rs-whatever

Your problem is that IEEE-488 and RS-232 aren't just different connectors, they are completely different bus protocols. You can't just make up an adaptor.

Basically you need a dedicated computer in between to convert IEEE-488 signals to RS-232 and vice versa. That's what the kit i linked does.

ok, how do i find a new card that connects to the 25 pin thing

what's the precise name

It might be simpler to get an IEEE-488 card for your PC

do you know what I'm talking about?

@JohnRennie No, the PC has that already

I need a 25 pin card

But I can't find one because I don't know what to google

@0celo7 are you sure? I've never seen an IEEE-488 controller using a 25 pin D connector. Those are normally used for the serial port (or maybe I mean parallel port).

I'm not sure what you mean

RS-232 is shit

We have a card in the PC with the weird connector

IEEE-488 isn't shit

I need to plug in a 25 pin thing into that computer

you can't uncrapify RS-232 without a dedicated machine

so I need a 25 pin card

Ah sorry I misunderstood, I thought the picture you showed was the kit, not the computer.

But I don't know what I'm looking for

@JohnRennie Well

We have an X ray machine plugged into that computer

using the weird thingie

But the plug allows you to stack two things for some reason

so I wanted to go from weird thing to X ray, then convert the thing on the X ray to 25 pin

@0celo7 yes, IEEE-488 allows you to stack lots of different kit. Technically it's called daisy chaining.

@JohnRennie I thought that was an Apple term for Thunderbolt

But you can't use the kit with a 25 pin connector in that way.

ok, so I need a 25 pin card

how do I get one of those

Has your PC got a nine pin connector on the back?

It's in use.

OK, in that case you just need an RS-232 card for the PC to add extra serial ports. They are dirt cheap.

I literally cannot find it

amazon.co.uk/Serial-Port-Cards/b?ie=UTF8&node=430538031

I don't see any there

can you link to a specific one

amazon.co.uk/gp/product/B00NNRYZOE

that's not 25 pin

9 and 25 pin serial ports are compatible. Just use an adaptor cable.

link?

I don't know anything about this

amazon.com/StarTech-com-DB25-Serial-Cable-Adapter/dp/B00066HOWK

?

amazon.co.uk/dp/B00HJU83KS?psc=1

oh crap, how do I know which genders are which

Ah, you got there before me :-)

You want "9 pin female" "25 pin male"

So the one you linked is fine.

are you sure

But those adapters are a bit large and clunky. I would use a cable with a 9 pin female on one end and a 25 pin male on the other. Hang on, let me search.

the thingie I have says "^COMPUTER^" on the male part

so I need a female 25 pin, no?

amazon.co.uk/kenable-Serial-RS232-Modem-Cable/dp/B0079I756S

If you look at the 25 pin connector on your kit you should see that it is female.

So your cable needs to be 25 pin male.

Dude, the computer side is clearly on the male side

Unless females have penises in which case I need to have a talk with my girlfriend

I think what you have there is an adapter to connect to the printer port on the PC.

On a PC printer porrts are female while serial ports are male.

wtf

What a wonderful episode of "0celo7's adventures in tech" ;)

Why is this hard? You can understand homology but not PCs?

Get the manual for your kit and check that the port on it is a serial port. That way you're sure what you need.

are you saying this is an adapter, nothing more?

but it's female on the other side

pretty shitty adapter

@ACuriousMind please please please math.stackexchange.com/questions/1887646/…

I'm desparate

I think the thing in the picture is probably a dongle.

It's quite common to build them into parallel ports.

yes, it's supposed to be a dongle

but you're saying I need a printer port?

@JohnRennie There is no logic to computer hardware

Hang on, now I'm getting lost.

Is it the thing in the picture you need to connect?

Yes

Aaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

In that case you need a printer port.

I need to stick the 25 pins into my PC and make it work

Ignore all the stuff about serial ports.

link?

What PC have you got? What make and model?

@0celo7 I have literally no idea what that question is about

...I dunno, it's a PC

@ACuriousMind I cannot prove eq. 2

@0celo7 I can see that

Dell

amazon.co.uk/s/…

Optiplex 7010

@0celo7 good, Dell is good. What model? Optiplex? Dimension?

Aha I've got a 7010 - hang on I'll dig out the manual

@ACuriousMind The only place Ricci flow comes into play is the $\nabla^2f$ equation, which I have supplied

The rest is straightforward topology

You call linear algebra highly non-trivial and say that is straightforward?!

Yes

Both you and my professor seem to be confused about that

He wonders why I spend 3/4 of our talks on linear algebra

It's because that's the nontrivial part

Well, I see it the other way around. I can't help you with that question

Does the back panel look like this?

@0celo7 or like this?

@0celo7 Hello?

In a nearby tree a raven croaks Nevermore

In the graveyard, by a headstone bearing a carving of a cat, the earth looks disturbed as if something is trying to push through it from below.

In a garret in Chester a middle aged man lies slumped across his desk. His last action, before ennui wreaked its terrible fate upon him was to post a link to a parallel port card for a Dell Optiplex 7010.

@JohnRennie maybe it's time to go outside for a bit?

@JohnRennie You need to drink less coffee

Anyway, is @CuriousOne around? Imma call it that s/he owes me at least having a think at this one

@JohnRennie Can you give me a dupe check on this one? physics.stackexchange.com/questions/273630/… Not sure why it was tagged with QM in the first place, tbh.

@ACuriousMind ummm... because it's not an obvious duplicate? We have room for multiple questions on the same topic at different levels, and we definitely need a version at a level above the existent question. (Ironically, if John had used the QM tag, my vote would have reopened it. Not that I'd have used the unilateral reopen on a controversial question, though.)

@Secret thx for noticing. think the permittivity/ permeability eqn of spacetime is important to analyze further but so far no takers. need sounding boards like Einstein needed Besso. plz drop by sometime/ occasionally chat.stackexchange.com/rooms/9446/theory-salon

You might also like to discuss with slereah and 0celo7 about that 2016 arxiv I linked, it seems someone do take this material science pathway and modelled spacetime as some kind of fabric and the notion of youngs modulus is well defined there

@Secret what game is that?

@vzn Quantum Moves

@Secret skimming it now. wow! thx! o_O looks like exactly what have been musing on some, impressive, has anyone commented on it anywhere? wonder about author bkgs/ credentials

not really, 1) it is recent (and does not knwon to have submitted to a journal), 2) I have not check the authors yet because of being too quantum focused on studying

@Secret the major (unmentioned so far) problem is that analysis along these lines is considered to have been debunked 1century ago with the michelson/morley experiment vs ether hypothesis. so physics establishment/ conventional wisdom regards it as a long-ago resolved issue. but have long thought/ think that it can be revisited successfully/ groundbreakingly in something like this way.

@JohnDuffield ↑ !!!

@ACuriousMind ↑ !!! theres your deformations/ eqns

@DanielSank ↑ !!! theories/experiments/ideas which about the elasticity/permeability/etc of spacetime It would be cool if someone would explain this as I'm sure it could be interesting or new and might shed light into string theory (but not anytime soon)

@EmilioPisanty well, but as I see it, nothing about this new question distinguishes it from the previous one. It doesn't say that the previous question is at too low of a level, for example.

@Secret thx again for sharing, a very big deal, fast glance, looks like it could be the very beginnings of a QM+GR unification along lines conceptually sketched out very vaguely by me earlier if you ask me... any takers? o_O :P

@EmilioPisanty definitely a duplicate

@JohnRennie busy with a client at work

@PhysicsGuy Based off of profmattstrassler.com/articles-and-posts/… I had thought that virtual particles manifest through interactions term in a perturbation expansion--sort of like poles in a multipole expansion. As such, they are more of a mathematical tool, than actual physical objects, but PhysicsGuy's response seems to indicate that they do appear physically somehow. Is that actually true? Man, I really need to learn some QFT.

@WilliamBulmer see my ramblings on this earlier today:

It's now on my todo list to write this up in a more coherent fashion and post it as an answer to one of the many what are virtual particles questions we have on the site.

@0celo7 does the card I posted look OK?

@JohnRennie But in the end, after you have integrated over the entire state space, they cancel out, right? There are no pure states where n of these virtual particles = 0? Sorry, I don't know second quantization, so forgive me if I just wrote garbage.

I mean where $n \neq 0$

@vzn Why are you quoting this?

The point is that we write the interaction as a sum of various processes involving the free field creation and annihilation operators, but that doesn't mean those operators are actually creating and annihilating particles.

@JohnRennie Ehhhh, sure it does!

::hides::

@JohnRennie That makes sense, and aligns with strassler's explanation

And that's why virtual particles don't exist

QED

(Pun intended :-)

@JohnRennie I think the best way to explain virtual particles is with the Dyson series, i.e. just write down some non-relativistic time dependent perturbation theory expansion and explain the terms.

In fact, I have that all written out in nice TeX right now in front of me.

I'd be happy to mail it to you immediately.

@DanielSank found a paper. Tenev/ Horstenmeyer. it gives the vague statements meaning, makes the hunches precise enough to actually be right/ wrong. plz check it out if you actually care about the topic. its full of eqns arxiv.org/pdf/1603.07655.pdf

@vzn Please give link to abstract page, not the pdf.

@JohnRennie I just am confused by the implication that their duration of existence is what is responsible for them being "virtual", rather than the more palatable idea that they are simply mathematical tools, similar in spirit to poles in a multipole expansion

@WilliamBulmer Yeah, the duration thing is sort of irrelevant.

@WilliamBulmer where did I imply that?

@DanielSank arxiv.org/abs/1603.07655.pdf (sigh yes master whatever you desire your wish is my command etc)

@vzn -_-

@JohnRennie You didn't

@vzn Thank you, but lol the url.

@vzn Hmmm... I command you to bring me peeled grapes and baklava!.

::waits::

How do you quote something someone wrote?

@WilliamBulmer Use > at the beginning of the line.

@DanielSank :: your request will be fulfilled thru a proxy, your wife ::

thanks

Or, if you want to link you message, click the little reply arrow thingy.

NB that's > then a space then the quoted text

@vzn lolol

> It looks like this.

I was responding to chat.stackexchange.com/transcript/message/31589359#31589359

@vzn Actually, between the two of us, I'm the baklava maker in the family...

though, to be fair, he might not have actually been implying that

@DanielSank ah. interesting coincidence. my family member was interested/ talented at that too. (your other servant BM can bring you exploded grapes, which maybe technically are also peeled? you know how genies are, reminds me of a movie on that)

@vzn lol

Paging @BernardMeurer

Paging also @JohnRennie regarding the Dyson series...

Hm?

You want some microwaved grapes?

@BernardMeurer I command you, slave!

Jee, okay okay, lemme check if I've got grapes

@BernardMeurer have long been meaning to ask you the outcome of your microwave-grape experiments, but held back, nows a good a time as any... do they ever lose peels as an outcome?

If I set fire to my kitchen a fourth time it's on you

o_O

@DanielSank thanks but I think you overestimate my grasp of QFT :-) I don't even know what a Dyson series is (it's a type of vacuum cleaner isn't it?).

@vzn I didn't get permission to strip our microwave apart :(

@BernardMeurer I guessed that from the fact you're still alive

@JohnRennie Nah, dude, no fields here.

No relativity, no fields. Just time dependent perturbation theory.

I once made a good joke about dyson vacuums and the girl I was with didn't go for a second date lol

@DanielSank When you say sort of, do you mean they are slightly relevant?

@BernardMeurer it reminds me of the old kids joke about science/ removing frog legs, ever heard it? remove 1 leg, remove 2 legs, remove 3 legs, remove 4 legs, conclusion.... o_O

How do I send to facebook?

@vzn They just explode kinda, you'll usually encounter some shrunk carbonated remains of grape

@DanielSank You gotta have a facebook first I think

@BernardMeurer only amazing/ legendary wizards can get girls with physics, and maybe even then they have to suppress that

@vzn My quantum pickup line has worked before

@vzn And it wasn't a physics joke, it was a horrible joke

@vzn I remain not convinced that Bernardo has actually "gotten" a girl with physics.

@DanielSank I have! She's in my dungeon right now!

Ops

@DanielSank exactly/ my point. so what about you? :P

Delete it

I copied it

Dang it

FWIW my address is findable through my profile page. Feel free to use it at your convenience.

→ 1 message moved to Trash

I was about to copy and register it at sketchy websites with dubious content

@BernardMeurer the zen question would you consider "shrunk carbonated remains" peeled or not peeled? that is the question (of the experiment/ hypothesis... aka sort of like particle detected vs undetected)

@BernardMeurer ooh yes please! :-)

@vzn Uhhhh.

@vzn Not peeled

Definitely

@BernardMeurer but wait! maybe it is in a superposition of peeled and not peeled! "schroedingers grape!"

If you get blown up it doesn't mean you've been flayed as well

@JohnRennie Is "sod it" polite for "fuck it"?

@JohnRennie dunno

It's in British

Last night I dreamt about h bar (details later after the bath)

Wtf

cast include ACM, 0celo7 and dmckee looking guy

@DanielSank erm, sodomy, is erm kind of the parity reversal of fuck it :-)

@JohnRennie Ah. That's considerably more precise than I expected.

@BernardMeurer sounds like a horror movie or the latest ISIS news

@JohnRennie It's the what?

@0celo7 British? The card price is in US dollars ...

@BernardMeurer let's just put it behind us

@vzn ISIG - Islamic Grapes

@JohnRennie That's what she said

We're all going to banned any moment now :-)

@BernardMeurer we are Trump is considering banning those :P

If I get banned for making a joke by some rando Jo who doesn't get it (Who I hope is still alive and well) I'll immolate this chat

@BernardMeurer By microwaving it?

@BernardMeurer seem to be no n00bs around today youre safe for the moment

@JohnRennie yes I will burn you all alive :)

Ooh the temptation to flag that :-)

Doesn't that smile look tainted somehow in a sentence like that?

I don't know the emoticon for an evil grin

@JohnRennie >:)

>-)

( ﾟ∀ﾟ)

I'll remember that for next time my dark side threatens to break out.

@DanielSank The saddest cooking show ever youtube.com/watch?v=ZKxhI4I5kq8

@JohnRennie check ur emailz.

@BernardMeurer chging the subj, wondering if you ever read physics papers? or books?

@vzn Yes. I like looking at the pretty figures and drawings

Well

Wait a sec

@DanielSank got it thanks. I'll have a read - I may be some time.

@BernardMeurer lol ok maybe try this one sometime/ join (small) club so far & tell me how "pretty" it is arxiv.org/pdf/1603.07655.pdf

@JohnRennie No problem.

Maybe skip to the discussion section, and then read the math section.

I promise the math is all relatively simple.

I use very explicit notation.

@vzn This is all I have read in the last 2 years

exclude the Quantum Theory one, my grandma gave it to me

I only saw the pretty pictures

Aaaaaaahhhhhhh ...

There's an extra Zizek missing

The unperturbed Hamiltonian would be the free field limit of the particles at infinity, so the perturbation corresponds to the perturabtive terms needed to describe the interacting field.

[] Ok back from bath, begin telling about the dream shortly. If someone felt weird, there's a reality check section after the dream finished sharing

In h bar, there's a discussion that took place involving the usual users (Acuriousmind, dmckee, 0celo7 and a user with a purple blue avatar etc.). During the conversation (there are 2 background conversations going on concurrently with mine, one mainly started by 0celo7), I

discussed with them about the Ripple Dynamics model and I am figuring that the ripple velocities are actually invariants thus should have an associated coordinate transformation rule. I also suspect that the transformation rule will

be less trivial as any segment of the loop (including a path that revisit some points and overlap with itself partially) should also be subjected to coordinate transformation in order to ensure the invariance of the ripple velocity. Later on the day, Acuriousmind said that he would like to hear about the details of that model after 15:00 and I said I won't be available until after 15:00 Stockholm time.

You type fast

Later on after the relevant time is reached (where I saw the sun setting outside my room overlooking at the park), 0celo7 and Acuriousmind joined the discussion. Acuriosmind then posted a mind map of some sort listing all known terms that describe the relationship between one model and another (terms like "opposite", "supersymmetric", "related" etc.).

(I am copy pasting)

The mind map resemble a phylogeny tree with boxes and ovals as the entries. 2/3 of the mind map on the left side the ovals are colored reddish while the remaining 1/3 are colored bluish. There's also a thin vertical strand extending towards the centre of the tree with 4 words forming a column and "unknown" is written in place on where my model is located.

Just before I left h bar, I saw dmckee (or at least someone look like his avatar and Danu), saying that he missed the old golden days when hardcore maths was discussed in h bar and hope to get them back /.../

End of dream

@BernardMeurer lol ok weird coincidence my fave is "quantum theory for dummies" ← actually exists

@vzn I know it does, but why would you read that and not Shankar?

@JohnRennie yes

IMHO For Dummies is an OK learning material (at best) but a GREAT reference material

Although I'm not entirely sure you need the "at infinity" unless you're specifically thinking about a scattering problem.

that C++ for dummies is SUCH a good reference

@BernardMeurer actually have that too! o_O

Also, who are the people who wrote that paper you referenced to me?

Well in QFT particles are only well definied in the limit of the interaction going to zero i.e. infinite separation.

@JohnRennie Uhhh, yeah ok sure.

@Secret Can you explain what a tensor is to me using only emoticons?

@DanielSank No seriously. For an interacting field we can't even say what particles are present.

@Secret very detailed... do you remember your dreams often?

@vzn I have dreams every single night, and I have kept a log for 5 years

@Secret (trying to figure out what to say next...) sounds very jungian.

@Secret That's pretty cool

I barely ever dream

and they're usually meaningless

@JohnRennie Indeed not.

Unless when I eventually solve a bug in a real code on my dream

that happens every so often

@Secret is that something you are working on outside of dreams aka real life? (the paper you cite might be said to relate to "ripple dynamics" incl stuff am working on myself... or heck large swathes/ most of physics...)

@BernardMeurer LEt :) be a tensor. Then :) (:( + :O + :( ) = :):(+:):O+:):(

@Secret Holy shit

@JohnRennie link?

@0celo7 accessories.us.dell.com/sna/…

@0celo7 Mini tower Optiplex 7010s need a full height card while the desktop cases need a half height card. But that card comes with both brackets so should fit either.

I also tend to read things outside my field of study, and mix them in crazy ways (one source of why ACM often get confused at my questions, because the mix is too incoherent and random)

@0celo7 did you see:

@Secret Weird how?

Alos, I am doing my phD in chemistry in a few months

@BernardMeurer Ask 0celo7, and you will notice I tend to end up proving the converse of something that is asked to prove without knowing

@Secret awesome/ congrats! starting you mean? was long wondering about your edu bkg... do you have masters? whats your undergrad?

@vzn Undergrad is chemistry and physics Bachelor. I got good results on my honours thus according to our school's rules, one can do a phD straight away

I did my honours last year

@Secret nice are you US or europe or...? did you do honors thes(es)?

australia

@Secret Ah, cool!

Which school?

@vzn Yes topic is "Investigation of hydrogen production from the photodissociation of acetaldehyde"

@BernardMeurer UNSW

@Secret Sweet! Congrats man

Way cool:

rsc.org/chemistryworld/2014/09/…

@Secret aha that looked familiar & now see you told me already oops