The h Bar

vzn

3:05 PM

@JohnDuffield so hows the book selling? any tour dates? :) :P

John Rennie

@lılostafa do you mean each line of new file is the corresponding lines from the two files concatenated?

John Duffield

@vzn : the official sales stopped years ago. There's just a few secondhand sales at silly-money prices.

vzn

@JohnDuffield (just read the free amazon pgs...) so are you retired?

diobuc eulb

3:22 PM

@BalarkaSen \o/

Balarka Sen

\o

diobuc eulb

\\\O0O///

John Duffield

@vzn : no. I'm not retired. Who said I'm retired? I work full time, in IT. I have a ten-year old son called Rhys. There's a picture of him as a baby on page 57. Here we go. He was lying on his back on our granite worktop.

2

vzn

@JohnDuffield awww, cute! :) was just guessing about the retired part. you seem to have a lot of time to pursue physics. (just reading about the manchester university math tower history, your other kids "vs" science, general STEM level decline etc.) btw youre aware, you & JR are not far from each other geographically? dont know history there.

John Duffield

@vzn : John Rennie's in Chester. It's four or five hours drive from Poole.

vzn

3:29 PM

@JohnDuffield maybe if you two'd have a ~~beer~~ pint or two things might go smoother in here :P

John Duffield

@vzn : they're going pretty smoothly.

vzn

@JohnDuffield lol for the moment o_O :P

John Duffield

@vzn : you will love some of the stuff I've dug up in the last year.

vzn

@JohnDuffield have been digging ½ furiously myself, plz check out my blog sometime, it has strong alignment with some of your directions & am sure youll luv the wild einstein portrait (there since beginning). have met a few cohorts interested in "paradigm shifts" so to speak, slowly/ incrementally/ noticeably building up some. "change is in the air" :) also just shared your electron ref in my chat room plz drop by sometime will do intros chat.stackexchange.com/rooms/9446/theory-salon

John Duffield

See Gustav Mie's Foundations of a theory of matter translated by David Delphenich. Mie said "the two potentials, j and f, embody the physical state of the universal ether".

He also said electrons "are not distinct from the ether. They are not, as has been believed for twenty years, foreign particles in the ether, but they are only places at which the ether takes on a particular state that we give the name of electrical charge". Chapter 2 is Knot Singularities in the Field.

That was in 1913.

vzn

3:38 PM

@JohnDuffield itd be great if you wrote up your new findings since the book was published, would defn like to explore all that, have been haphazardly collecting refs as you cite them even pre your absence, even bookmarking some of your chat lines. never got chance to talk much, yet it was high on my todo list :)

John Duffield

@vzn : I have been writing things up. The working title is the physics detective. As I speak I have 42 articles of circa 5000 words. The above list at 13:59 is some of them. Would you like to see one?

vzn

@JohnDuffield 5k words each? ~5000 x 42? o_O

John Duffield

@vzn : Yes. So far. I have to do maybe 10 or 15 more. I figured on getting the full set ready then putting them on a blog.

vzn

hence the need for a blog. let me try to find 13:59, the default time fmt in here is local time while typing but GMT in transcript afaict

John Duffield

@vzn : here, I've copied and pasted them: time, speed of light, gravity, history of QM and QED, gauge theory, photon, pair production, electron, positron, electromagnetism, magnets, monopoles, charge, mass, proton, neutrino, weak interaction, electroweak, nuclear force, neutron, antimatter, black holes, Hawking radiation, information paradox, firewall, dark matter, big bang, inflation, dark energy, edge of the universe, fate of the universe

vzn

3:45 PM

@JohnDuffield oh right saw that. that reminds me was gonna ask you what your take was on Hawking.

John Duffield

@vzn : I've never been a fan I'm afraid. But if you don't mind I'd rather not go into it now. It's not the time.

vzn

@JohnDuffield (yes ofc) actually just posted on that myself, zilch reaction. chat.stackexchange.com/transcript/71?m=43416639#43416639 think you should feel "free as possible" to express yourself in here, the room is full of many controversial topics. the trick is to go no further than mods allow. sometimes the 3rd rails are clearly delineated & other times they are not. (spking from experience)

John Duffield

@vzn : I don't have a problem with the moderators. I'm civil, and I talk good physics.

I don't have a problem with anybody.

vzn

@JohnDuffield am curious about all that & others are too (have my own inadvertent/ nervous brushes with mods/ flagging etc) & maybe we can talk about it in other room sometime or maybe you can write up your pov on "what happened" somewhere.

John Duffield

@vzn : water under the bridge mate.

Let's talk physics.

vzn

3:59 PM

@JohnDuffield glad to hear you feel that way, although it was a very long bridge so to speak o_O remids me/ have something on that think you should see (if you havent already), will post in other room.

@JohnDuffield sure, re that, you seem to have lots of admirers— think well deserved!— in here wrt that, but so far they are mostly quiet on your return. maybe they were just citing your name ~½-facetiously.

Slereah

I don't think anyone here would really wish to discuss physics with him in earnest

ACuriousMind

@vzn Alright, you know that we don't like discussions of past suspensions here, and you would do well to take an example in JohnDuffield's current attitude to this matter.

vzn

@Slereah he was routinely cited with some admiration eg by 0celo7 during his absence but maybe it was a joke by 0celo7.

John Duffield

@vzn : no probs, I've looked in from time to time.

Slereah

@0celo7 is incapable of expressing any genuine sentiment

He has caught the irony flu

vzn

4:05 PM

@ACuriousMind understand/ familiar w policy as my statement suggests & there was no invitation to discuss the suspension in here.

John Duffield

@Slereah : wouldn't you like to discuss wormholes with me?

Slereah

Not really, no.

ACuriousMind

@vzn Your last few messages have all been references to a past suspension. Don't play dumb.

John Duffield

@Slereah : are you sure? Only I don't think they exist. It might be worth your while if we talked about that.

vzn

@ACuriousMind he was absent for 1 yr. its a ref to his absence.

Slereah

4:08 PM

I don't really think they exist either, but it's not really a topic to discuss with someone who does not seem to know any physics beyond high school

vzn

@Slereah JD has a lot of IT bkg as apparently you do also maybe youd like to discuss that instead. but be nice™

Slereah

Also a terribly dull topic :p

I wouldn't be doing IT if money wasn't involved

vzn

@Slereah feel similarly "join the crowd"

@Slereah lol guess you guys have something else in common :P

Slereah

I hope you mean the "not believing in wormholes" part :p

John Duffield

@Slereah : I know an awful lot of physics. IMHO there's a chain of logic that goes time → speed of light → gravity → black holes → singularity theorems → Hawking radiation → information paradox → firewall and takes in wormholes on the way.

But if you don't really think they exist either, no problem.

John Duffield

4:23 PM

Would anybody like to talk about gravity?

diobuc eulb

fuck gravity dude

shattered the screen on my phone because of it

John Duffield

@diobuceulb : Then you'll be interested to know that If you're falling freely then the two terms are equal and opposite so they cancel out and you're left with an acceleration of zero. Or in other words, when your phone slipped from your hands, it did not accelerate towards the ground.

vzn

@Slereah (later thought: many in here are not past high school, many have not studied physics even in HS, & youve chatted with many of them on misc [non]physics topics etc)

Slereah

I'd rather not discuss about spacetime topology with them, though :p

diobuc eulb

@JohnDuffield sure let's go with that but it decelerated on impact regardless so thinking of it like that isn't going to fix my screen

vzn

4:28 PM

@diobuceulb know the feeling/ empathize, pulling other pkg out, $300 ipad popped out of my backpack onto concrete last summer, screen a thousand tiny shards/ facets of glass

@Slereah think youve likely discussed spacetime topology with non HS/ non physics studying persons in here given your copious engagement with chat/ spacetime topology etc.

John Duffield

@vzn : according to some it was accelerating when it was sitting in your backpack, and accelerating when it was lying on the ground in 1001 pieces. But in between it wasn't.

Slereah

There's about 3 people here with whom I can kinda discuss it

and even then mostly the math aspect

vzn

@Slereah lol know that feeling about how ones chosen/ specialized/ narrow area in physics can be "lonely," can we all relate on that one? :) :P

Slereah

Alas the cool GR people don't come here

where is Ben Crowell and the italian guy when you need them

Hell I'll even take Lubos Motl

vzn

@Slereah so 0celo7 or BaSe is not a "cool GR person" eh? you should be more careful with your careless generalities :P

Slereah

4:33 PM

@vzn @0celo7 isn't really interested in GR as he often says

He likes differential geometry

ACuriousMind

@Slereah Please don't call other people insane.

Slereah

The physical part of GR he's not so much into

Same with Balarka, really

vzn

@Slereah yes 2nd that if Lumo will blog all day why wont he try chat out anyway? and hed be perfect for the speaker session. but be careful what you wish for :P ... anyway guess nobody around here is friends with him. ps does he have any "friends" at all? :P

Slereah

He's more of a topologist than a GR fellow

Well there is that one dude who comments on every post he makes

vzn

@ACuriousMind ("...even if they are," lol) :P

Slereah

4:34 PM

What is the polite way to describe Lubos Motl

vzn

@Slereah Lumo is impolite. so thats sort of an oxymoron eh?

John Duffield

@Slereah : spacetime models space "at all times". It's a static arena. There is no motion through it. Wheeler thought there was. You might want to check out what Ben Crowell said about it. "Objects don't move through spacetime. Objects move through space".

diobuc eulb

@Slereah czech ex-string theorist and activist

vzn

anyway some might even take "mad scientist" label as a compliment, there is a rich history of that, esp/ incl in cartoons... hell it goes all the way back to famous scifi of all time, frankenstein... (can anyone find earlier examples?) :) :P ... (ps fyi theres a very detailed/ carefully curated list on my blog sidebar since early days!) o_O

Slereah

He's more of an angry scientist

@vzn "The Clouds", by Aristophanes

The school of Socrates is basically early mad scientists

vzn

4:38 PM

@Slereah no kidding a greek ref? really? was it a god or a human or a demigod? fascinating

Slereah

It was famed philosopher Socrates

And his many students

Secret

Slereah pseudo-discuss some aspects of wormholes with me, which often end up me spending the rest of the time reading the links he referred to

But as I have said, I knew basically nothing of the details, even though I have learnt GR before and it got rusty

That discussion about the xkcd and the notion of pretentiousness put me into a lot of tension between him though

which is one reason why h bar is not very stable currently and lead to many silent periods

vzn

hmmm, thinking about it, this greek legend seems to me very close to metaphor about a mad scientist, often cited in that context. was he technically human or demigod? did he have any gods in his lineage?

Daedalus

In Greek mythology, Daedalus (; Ancient Greek: Δαίδαλος Daidalos "cunningly wrought", perhaps related to δαιδάλλω "to work artfully"; Latin: Daedalus; Etruscan: Taitale) was a skillful craftsman and artist. He is the father of Icarus, the uncle of Perdix, and possibly also the father of Iapyx, although this is unclear. == Family == His parentage was supplied as a later addition to the mythos, providing him with a father in Metion, Eupalamus, or Palamaon, and a mother, Alcippe, Iphinoe, or Phrasmede. Daedalus had two sons: Icarus and Iapyx, along with a nephew either Talus or Perdix. Athen...

Secret

O btw, I am emotionally insane, I have no doubt about that

ACuriousMind

@vzn No, he was just a stupid human.

vzn

4:42 PM

@Slereah they are not really depicted as crazy are they? just eccentric? maybe early cranks :P

John Rennie

@Slereah I agree that the Visser polyhedral wormholes are somewhat suspect, but take e.g. the Ellis geometry. That's a perfectly good geometry so why do you think there are problems with it?

Slereah

@vzn Fairly excentric

@JohnRennie Well the problems are basically violation of the ANEC

Secret

while I have stopped the shitposting altogether in h bar by Balarka's request, I mostly reside in the math chat room nowadays

vzn

@ACuriousMind so its ok to call legends stupid but not crazy? :P anyway while taking your point, daedalus is not exactly described as stupid

Slereah

I don't think there's any non-quantum scale wormhole that is reasonable

ACuriousMind

4:43 PM

Daedalus is one of the many Greek tragic stories about humans failing due to their hybris, and not really exceptional in that regard.

Slereah

"The Clouds" does contain one of my favorite joke

John Rennie

@Slereah well yes, I agree.

ACuriousMind

@vzn If you genuinely see no difference between calling a fictitious figure stupid and a living person insane, I have nothing to tell you.

Slereah

STREPSIADES

Ah! they're looking for onions. Do not give yourselves so much trouble; I know where there are some, fine big ones. But what are those fellows doing, bent all double?

DISCIPLE

They are sounding the abysses of Tartarus.

STREPSIADES

And what are their arses looking at in the heavens?

DISCIPLE

They are studying astronomy on their own account. But come in so that the master may not find us here.

vzn

@Secret huh, who calls it ----posting? who here has never been criticized in the room?

John Rennie

4:45 PM

@Slereah But are we arguing about whether wormholes exist in reality or whether the wormhole metrics are valid solutions to Einstein's equation?

Slereah

@JohnRennie Oh they are definately solutions

And of course wormholes may exist, but I don't think traversible ones can

Secret

@vzn No, that's an actual term for referring to random meme etc. postings

I am not being accused

Slereah

Except maybe for the self-sustaining ones, but those are about a Planck length big

vzn

@ACuriousMind its good we have mods to draw sharp distinctions around here

John Rennie

As far as I know all traversible wormholes involve exotic matter, which (probably) doesn't exist.

Secret

4:46 PM

@vzn Criticised or not, it is clear I am getting more insane as time went by

Slereah

Well exotic matter isn't too bad

But even worse than that, traversible wormholes violate the averaged null energy condition

which is a very strong constraint

vzn

@Secret the world is insane so maybe you are acclimatizing better :P

John Duffield

@JohnRennie : the point is that if they don't exist they are invalid solutions.

I have a square room with a floor area of 16m². There are two solutions to the square root of 16. But there are no negative carpets measuring -4m by -4m.

Secret

As far I knew, I have been very good at infecting most of you with my insanity, thus I am not terribly worried on what the world thought of me

because, it is very clear the world's is no match against me insanity and will submit under it by 2020

John Rennie

@Slereah whether the violations of the ANEC are any worse than violations of the other energy conditions is debatable. They're all pretty bad.

Slereah

4:49 PM

Except for gravitational squeezing, basically no form of matter can violate the ANEC

@JohnRennie Well a lot of the "classical" energy conditions are violated

By various quantum effects

the ANEC is fairly tough though

vzn

@Secret personally somewhat enjoy your jungian like plumbing of the depths of the unconscious/ archetypes/ dreamworld etc, maybe you are the local cyber shaman (pushing strongly against the local high objectivity gradient), you should look into the area

John Rennie

I confess I'm a bit disappointed. Given that most of us agree exotic matter doesn't exist we already known wormholes don't exist, along with CTCs and superluminal travel.

Slereah

But exotic matter does exist :O

We even use it in experiments!

John Rennie

I thought you were working towards some fundamental issue with the wormhole solutions.

Slereah

Although not for being exotic matter

John Rennie

4:51 PM

An instability or something like that.

Slereah

Squeezed optical states are being used for interferometry

Secret

@JohnRennie Nature seemed so hellbent on forbiddening FTL signalling but making it very hard for us to prove the general case

vzn

@Secret btw meant to mention to you, sounds like "ghosts" a word that is not uncommonly found in serious physics writing... o_O

John Duffield

@Secret : I don't have an issue with FTL signalling. But I do have an issue with people saying it leads to time travel et cetera.

Secret

@vzn ghost fields is not the same thing as what we knew as ghosts. They are field with a negative kinetic term in their lagrangian and signifies some kind of instability in the theory (as far I recall)

@vzn also, re that quanutm organisms thing, the context is answered here in this PSE: physics.stackexchange.com/questions/392008/…

vzn

4:54 PM

@Secret am not familiar with them in that context, there are other contexts.

Slereah

you're thinking of phantom fields

Secret

turns out, we cannot make self replicating quantum systems, which is quite eye opening to me that there is actually something that is only possible in classical mechanics but not quantum

Slereah

An entirely different kind of supernatural apparition

vzn

@Secret there is more analysis of qm in biology these days, aka "quantum biology," its a big paradigm shift, think it will eventually be much larger field. also think your ideas are close to bohms implicate order & urge you to read up on it highly

Secret

@JohnDuffield Well, if you accept the result of modern relativity (beyond the Einstein times), then FTL signalling will mean in one of the reference frames, the signal is travelling back in time. Actually I think this already holds in SR (and that is developed by einstein), no need to go to GR

lılostafa

4:58 PM

@JohnRennie yes exactly

Secret

@Slereah Actually, it does not help that one form of dark energy like scalar field that is proposed to accelerate the universe in some cosmology model is called phantom energy

so we have very confusing spooky terminologies in physics that refers to things that are not spooky

lılostafa

@JohnDuffield It just writes #NAME? in column C after doing that

vzn

@Slereah phantom, another great word that shows up in some diverse physics contexts... :)

John Duffield

@Secret : I don't accept that. Can you provide a reference? Meanwhile, a light wave is a transverse wave. Take a look at seismic waves, where longitudinal P waves are faster than transverse S waves. I don't have an issue with some wave in space moving faster than c.

Slereah

Physics is a very spooky thing

Secret

5:01 PM

Slereah: well yes and no

Slereah

Ghosts, phantoms, skeletons, monsters

Many supernatural things happen

Secret

I wonder when will someone came up with a supernatural field in theoretical physics literature

vzn

@Slereah wow that would be a fantastic blog or essay, would really like to read a survey on all that :P

John Duffield

@lılostafa : you must have done something wrong. Let's start at the beginning. I presume you have your two lists side by side in columns A and B?

Slereah

@vzn I already did one chronicling the appearance of weapons in GR

lılostafa

5:02 PM

@JohnDuffield yes

Slereah

samuel-lereah.com/posts/2018/03/13/…

vzn

@Slereah holy cow when did you get a blog congrats o_O

Slereah

a while back

though I don't really post often

vzn

@Slereah thats ok ppl barely comment either on blogs anymore these days anyway :(

John Duffield

@lılostafa : OK click on column C1 then click on the formula input box to the right of fx then key in =concat(a1,B1).

vzn

5:05 PM

geez doesnt even mention your Msc cmon man (ppl will wonder if you even passed HS physics) :P samuel-lereah.com/about

lılostafa

@JohnDuffield Again, the same result :(

Slereah

Most guns are related to causality issues

Except for that one ballistic exercize

Phase

@Slereah why don't you write about it in your Blag

John Duffield

@lılostafa : #NAME comes up if you have a syntax error. Copy and paste tjhe contents of your formula box onto this chat so I can see it.

John Rennie

@lılostafa what version of Excel?

Slereah

5:11 PM

about what

@vzn It is still under construction

Secret

@JohnDuffield @vzn @slereah @JohnRennie Here's a good reference that covers about tachyon dynamics in SR very well, including a small section explaining how the lack of time ordering of spacelike events allow us to find a frame where a tachyon becomes a particle that travels back in time

Slereah

Causality from FTL signalling is a fairly complicated issue, but under any reasonable definition, it does violate causality

lılostafa

@JohnRennie excel 2013

John Rennie

concatenate not concat

lılostafa

@JohnRennie Nice

Worked

John Rennie

5:17 PM

Cool :-)

Really you want concatenate(a1, " ", b1)

lılostafa

@JohnRennie I do other adjustments elsewhere (notepad++), but since doing stuff in a virtual Linux and copying the results back to windows was a little annoying I thought maybe it can be done in Excel

Secret

anyway, I am heading to sleep, I will respond any questions tomorrow (if any)

Slereah

I'd make more blog posts but I'm not 100% sure what I find hilarious in GR textbooks is a crowdpleaser

John Duffield

@Secret : on page 6 it says this: "this does not mean that there is an upper bound to signal velocity".

Semiclassical

Yeah, I know what you mean. There's a difference between things you personally find interesting/maddening and what a wider audience would care about

Slereah

5:22 PM

Although I should make a post about the assumption of homogeneity in cosmology

Since that is a topic that is LIED about

very much

Semiclassical

What's the usual lie?

Slereah

usually not stated directly, but the lie is that approximate homogeneity translates to a metric that is approximatively FRW

John Duffield

@Slereah : you should, because a gravitational field is a place where space is "neither homogeneous nor isotropic".

vzn

@Slereah know the feeling aka "blogging" its a feature not a bug :)

Slereah

turns out that it is very much a lie since you can construct spacetimes that are approximatively homogeneous but are not FRW metrics

probably not very realistic ones, but it's not an easy problem

Semiclassical

5:26 PM

is there an additional feature that you need to force FRW?

or is "approximate homogeneity -> FRW" just a failure of imagination?

Slereah

Well, Ringstrom has a 700 pages book on the topic

I must admit I haven't read it all yet

So I can't tell

Semiclassical

oof

Slereah

I mean, FRW metric seems to work fine with cosmological data, so it's probably alright

but it's a bit of a leap of faith in textbooks

Semiclassical

Is the other direction easier, i.e. approximately FRW -> approximate homogeneity?

John Duffield

@Semiclassical : IMHO it's a massive misunderstanding, but if you have homogeneous space you don't have any gravitational fields.

Slereah

5:28 PM

@Semiclassical Well there's the almost-EGS theorem

Ehlers–Geren–Sachs theorem

The Ehlers–Geren–Sachs theorem, published in 1968 by Jürgen Ehlers, P. Geren and Rainer K. Sachs, shows that if, in a given universe, all freely falling observers measure the cosmic background radiation to have exactly the same properties in all directions (that is, they measure the background radiation to be isotropic), then that universe is an isotropic and homogeneous FLRW spacetime. Using the fact that, as measured from Earth, the cosmic microwave background is indeed highly isotropic—the temperature characterizing this thermal radiation varies only by tenth of thousandth of a kelvin with the...

which is an averaged version of this theorem

Semiclassical

@Slereah It's the bit in the last few sentences, I gather?

Slereah

Oh actually that's in chapter 4

the last parts are about the stability of the universe

hopefully it is!

vzn

← thinks GR is "terribly dull" just like IT j/k :P

Slereah

GR is a lot of dull things to get into the interesting bits :p

Semiclassical

GR is "the road not travelled" for me

Slereah

5:30 PM

People want to talk about black holes but nobody wants to talk about algebraic classifications of the Ricci tensor

vzn

agreed its very broad and variegated if widely defined, lots of nuance/ edge cases etc, incl black holes in GR defn makes it sexy

Slereah

(spoiler it's dull)

vzn

@Slereah & spking of GR afaict you still have no comment on Tenev + Horstemeyer :(

Slereah

Who are those guys

vzn

@Slereah cited in here a few times, maybe mainly by me, but ref found by secret awhile back, was a bit shocked to find it, wanted to write something similar for years :| ... but, more work in progress

John Duffield

5:32 PM

vzn

@JohnDuffield wrt that it seems to me some new vocabulary is in order. there is some talking-past-each other due to vocabulary/ language differences/ misunderstandings. eg the word "space" is highly overloaded. ps what are you quoting?

John Duffield

@vzn : That's Einstein saying a gravitational field is a place where space is neither homogeneous nor isotropic. So if your universe is isotropic and homogeneous, there are no freely falling observers.

vzn

@JohnDuffield ok, yes, it seems almost to be saying its not euclidean. "neither homogenous/ isotropic" is the technical terms for a kind of density (or more typically, "curvature"). there are strong analogies between curvature and density... was just finding some other einstein refs in your book intro...

John Duffield

@vzn : the "curvature" is where the inhomogeneity is non-linear. Or where the density variation is non-linear.

vzn

@JohnDuffield feel that someone needs to try to look at physics terminology wrt GR very carefully and try to come up with some new distinctions. you seem to feel that some of the existing thinking is "wrong" (hence all the recriminations around here) but maybe its more a terminology problem and coming up with some new terms for the same things with better distinctions. tenev + horstemeyer seems a solid start/ foundation to me at this pt.

John Duffield

5:43 PM

@vzn : I've looked into this very carefully.

vzn

@JohnDuffield understood, am maybe gonna try to buy your book soon, but have to deal with pound-to-dollar conversion/ intercontinental shipping etc... ps plz seriously consider turning it into an ebook, might not be hard...

John Duffield

@vzn : don't buy it at those silly-money prices. Email me. Besides, the new stuff is better.

vzn

@JohnDuffield thx. but your "new stuff" is not yet available yet is it? btw amazon has a ½-decent ebook program, its probably significantly easier than what you already went thru for the paper version.

John Duffield

@vzn : I could let you have a sneak preview.

vzn

@JohnDuffield thx man... will be the 1st to hit your blog :)

@JohnDuffield it was a bit shocking to me that history seems to have utterly wiped away any traces of einstein referring to the density of space... just saw that 1st time in your book intro... theres been a huge shifting verging on a rewriting... agreed some key ideas/ original intent has been lost in the shuffle, ie its not merely cosmetic...

John Duffield

5:52 PM

@vzn : as I've said, IMHO there's some really interesting stuff in the old papers.

Semiclassical

I know at least one guy (who has done serious Einstein history stuff) who has pointed out a few times that there's some big differences between how Einstein talks about gravity and how modern relativists do so, for better or worse.

vzn

@JohnDuffield btw that reminds me, re "terminology difficulties"... let me dig up a supportive quote recently came across by somebody youd never guess in 1M years

John Duffield

Steven Weinberg?

vzn

@Semiclassical plz cite him! did he write it up?

John Duffield

@Semiclassical : who?

Semiclassical

5:54 PM

looking now

vzn

@SolenodonParadoxus Note that Lorentz aether theory is not the same as the standard "luminiferous aether", and experimentally indistinguishable from special relativity in its predictions, the sole difference being in its ontology/metaphysics. — ACuriousMind ♦ Feb 14 at 22:56

Slereah

Early GR is a fairly thorny topic

People were a bit uncertain about how to do many things

Like people weren't really sure if (anti) de Sitter space was really empty or not

Semiclassical

right, he discusses it in this article: physics.umd.edu/grt/taj/675e/QuestforGR.pdf

Slereah

Early works in singularities is a comedy of errors

People basically had no idea how to treat singularities properly

Semiclassical

I have in mind the paragraph at the top of page 20, though that's the punchline

Slereah

5:58 PM

Also Einstein was very stubborn on the topic of singularities

He was very convinced that 1) GR was correct and 2) singularities were not physical

Not a very stable position to hold

Semiclassical

"One consequence of the transformation rules for tensors is that, if all components of a tensor vanish in one coordinate system, they vanish in all of them. The Christoffel symbols then are clearly not tensors. For many modern relativists, this disqualifies them as candidates for the mathematical representation of the gravitational field.
Instead, as mentioned in Section 2, the non-vanishing of the curvature tensor is used as a coordinate-independent criterion for the presence of a gravitational field. To the end of his life, however, Einstein preferred to use the Christoffel symbols instea…

vzn

@Slereah agreed but there may yet be some "baby vs bathwater" challenge there.

Semiclassical

So it's that technical point of "gravity = nonvanishing of curvature tensor" vs "gravity = nonvanishing of Christoffel symbols"

vzn

@Semiclassical did know youre a GR fan. plz take a look at tenev + horstemeyer sometime :)

Slereah

A fairly dangerous idea since that means that Minkowski space has gravity in it

Semiclassical

6:00 PM

lol, I'm not a GR guy

vzn

@Semiclassical fine, "hobbyist/ aficionado/ amateur/ dilettante whatever" like the rest of us :P

Semiclassical

@Slereah yeah, that particular point is raised leading up to that sentence

vzn

@Semiclassical ie "what exactly is a singularity"?

Semiclassical

I don't really see any talk about singularity there.

Slereah

Here's what a singularity is for early GR :

"For $\alpha \neq 0$, it turns out that $r = 0$ and (for positive $\alpha$) also $r = \alpha$ are points at which the line element is not regular. By that I mean that a line element or a gravitational field $g_{\mu\nu}$ is regular at a point if it is possible to introduce by a reversible, one-one transformation a coordinate system, such that in this coordinate system the corresponding functions $g'_{\mu\nu}$ are regular at that point, i.e., they are continuous and arbitrarily differentiable at the point and in a neighborhood of the point, and the determinant g is different from 0."

vzn

6:04 PM

@Semiclassical ?!? look is this semantics? (again?) thought the topic was singularities.

Semiclassical

You may have been talking about singularities.

I was talking about the gravitational field in particular.

And whether Einstein vs. modern relativists would agree that a given scenario has a gravitational field or not.

vzn

@Semiclassical youre being a little difficult. try to spell it out for a "non GR guy." slereah raised the topic of singularities. are you saying singularities dont exist in GR?

Semiclassical

I am claiming nothing at all with regard to singularities.

Slereah

Calm down folks

Semiclassical

But the other point that was being discussed was the extent to which Einstein's understanding of GR would differ from modern relativists. I was pointing out at least one example where that is indeed true.

vzn

6:06 PM

@Semiclassical then not following the conceptual point in all the math technicality.

@Semiclassical thought the coordinate transformations being discussed might be related to/ intertwined with the singularity issue.

John Duffield

@Semiclassical : I've read some other material by Michael Janssen, such as Pascual Jordan’s resolution of the conundrum of the wave-particle duality of light. It's good stuff. But IMHO he doesn't dig deep enough with Einstein's general relativity.

Semiclassical

my knowledge of GR is very shallow, so take this as reportage not as argument on my part

in particular, i know basically nil about how singularities are supposed to be treated

Slereah

Singularities are terrible

Do not treat them at all

vzn

lol a black hole is a singularity :P

Slereah

Oh black hole singularities are the easy one

The hard ones are the weird singularities

Semiclassical

6:10 PM

naked singularities are why people like cosmic censorship

John Duffield

@Slereah : I think you'll be surprised about that.

Semiclassical

(or one reason why)

Slereah

Yeah, except "naked singularities" aren't actually well defined

There's like 20 different definitions

Semiclassical

oof

Slereah

Depending on what kind of singularities you find offensive

vzn

6:11 PM

anyway its not surprising that singularities, an edge case, would take many decades to disentangle (still a work in progress) and that early thinking would be incomplete, tentative, or even erroneous and have to be revised. however, wonder if they (under careful examination) might also point the way toward new theory etc.

John Duffield

I find point-singularities offensive.

Semiclassical

so "naked" is really a cheating way of saying "bad"

Slereah

"naked" means "We'd rather not have to deal with them"

John Duffield

@vzn : many decades to disentangle? I don't think so.

Slereah

Some nakedly singular spacetimes don't even have singularities

In the usual sense of the word

Semiclassical

6:13 PM

I'm reminded of a fairly famous line from a Supreme Court decision.

vzn

@JohnDuffield we still dont even really know exactly what happens in black holes in significant ways, the supposed "easy case"

Semiclassical

"I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that." (emphasis added)

source: en.wikipedia.org/wiki/I_know_it_when_I_see_it

Slereah

@Semiclassical why do you think we call them naked

John Duffield

@vzn : whistles innocently.

Semiclassical

heh

vzn

6:14 PM

@JohnDuffield strange, it doesnt make much sense for you to question my statement if you think any part of physics is incorrect or needs revision.

John Duffield

@vzn : I said earlier that there's a chain of logic that goes time → speed of light → gravity → black holes → singularity theorems → Hawking radiation → information paradox → firewall and takes in wormholes on the way.

vzn

@JohnDuffield think you have some new fresh insight but that fits with the statement its taking decades to figure all this stuff out. or maybe you literally think you have it all figured out? :P honestly think even hawking himself would agree we dont know exactly what happens in black holes, even he had to revise his views substantially in his life. btw re black holes theres some fascinating new empirical approaches yielding substantial new insight, have blogged some already on that...

John Duffield

@vzn : it's more like I've read lots of old papers starting with Einstein and I can see where some authors have made claims that don't tie in with "Einstein and the evidence". And where other authors have.

vzn

@JohnDuffield yes think that careful historical disentanglement will be quite valuable/ crucial on the verge of a new (unified/ coherent/ etc) theory of space+time+matter that is slowly starting to take shape.

John Duffield

@vzn : having read a whole pile of old papers, I have to say it doesn't feel like a new theory, it feels like an old theory.

vzn

6:22 PM

@JohnDuffield agreed, its an old theory that got eclipsed/ lost in the shuffle. its indeed time to revive it. it will not be exactly as it was pictured at the time. its the elephant + blind men and modern men are still missing part of the elephant. btw even the ancient millenias old hindu thought/ legend has some hint of it. :P

ACuriousMind

@Semiclassical Wait...is it called cosmic censorship because censors don't like nudity? Now I feel dumb :P

John Duffield

@vzn : IMHO the issues are not limited to gravity.

Semiclassical

lol, maybe?

Slereah

@ACuriousMind It's because the singularity should be clothed by an event horizon!

ACuriousMind

Yeah, singularities should have some decency

vzn

6:24 PM

@JohnDuffield to say the least. its extremely crosscutting. in 1 word, revolutionary. gravity is one particular important angle/ handle on it.

John Duffield

@Slereah : polite cough. Einstein thought the singularity was the event horizon.

Slereah

@JohnDuffield Yes he did

John Duffield

@Slereah : he was right.

Slereah

That's because the concept of singularit was not well formulated until about the 60's

Wait what am I doing, answering to JD

I fell into the trap

John Duffield

@Slereah : that's what people say. People like Penrose.

vzn

6:26 PM

@Slereah admit it you luv to chat with anyone "promiscuously" :P

Slereah

I'd rather not

John Duffield

@Slereah : wouldn't you rather talk about the parallel antiverse?

vzn

cranks are in the eye of the beholder. besides a word with the same root is cranky and look that one up in the dictionary

Slereah

More importantly who's the namby pamby mama's boy flagging those

John Duffield

Can we just talk physics please?

vzn

6:30 PM

← @#%& whistles past graveyard

ACuriousMind

@Slereah I'd advise to drop the topic.

Slereah

I regret nothiiing

vzn

@Slereah ACM has an "active" moderation style. o_O

Slereah

Not surprising for a German

ACuriousMind

@vzn An active chat requires active moderation :P

vzn

6:33 PM

@Slereah !!! lol thought they were all about freedom of speech but its gone the other way in the culture sometimes hasnt it... aka "hate speech" etc o_O

@ACuriousMind more "active" moderating changes the dialog like the heisenberg uncertainty principle. we would be more "careful" if we knew you were around. at least thats what youve taught me to do repeatedly. maybe try warnings 1st.

ACuriousMind

@vzn You aren't supposed to be careful because I or any other mod is around. You're supposed to behave yourself regardlessly.

vzn

@ACuriousMind you dont seem to admit borderline dialog.

ACuriousMind

And leave me alone with "warnings". There have been plenty of warnings, if you choose to be obtuse it is on you.

John Duffield

OK guys I have to go I'm afraid. It's been good talking to y'all today. Bye.

vzn

@ACuriousMind nobody wants to get in trouble esp incl me afaik. the more people chat, the more likely a random flag will happen etc.

ACuriousMind

6:38 PM

@vzn Random flags without merit will be dismissed. I am on record reversing auto-suspensions for frivolous flags. I don't get your point.

vzn

ok ACM not sure if you will listen or consider this but moding has a subjective element, dont you think?

ACuriousMind

@vzn Sure. If there wasn't, there would be just algorithms and no human moderators.

vzn

@ACuriousMind right, so SE mods are like refs who cant be questioned.

Balarka Sen

What the flipducking shite happened in this room

Semiclassical

^I'd star that, but uh

Balarka Sen

6:52 PM

I made an edit. Star now.

ACuriousMind

@BalarkaSen No ducks were harmed in this room, by flipping or otherwise

Semiclassical

works for me

Balarka Sen

@Slereah Use homeomorphism to escape

Slereah

@BalarkaSen Help I'm in a manifold where the only homeomorphism is the identity

Balarka Sen

An unfortunate 0-dimensional creature

I pity thee

I pithylee

Slereah

6:56 PM

@BalarkaSen u can build it in any dimensions

Using

~non-Hausdorffness~

Balarka Sen

I don't believe you. Any n-dimensional manifold with n > 0 is locally homeomorphic to R^n. Take such a chart R^n and build a piecewise-continuous homeomorphism which takes a point to some other point inside that chart (which can be done, as it's... R^n) and then glue using the gluing lemma with the identity homeomorphism outside that chart

Slereah

There is a weird standard example for it

Balarka Sen

I think you're very wrong.

Slereah

lemme see

I think it's in Gould

books.google.fr/…

though it's a fairly forced example

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