The h Bar

I have one question involving exotic matter $_{\text{because my scifi needs it...}}$ It has been answered by someone pointed out something I overlooked, but I never get the time to revise it with a stronger condition yet to ask deeper

It is possible once I get the coordinate system to align properly, the forces will add in a way that cancels in the way expected for physics

and I might be able to answer my question in the process

Slereah

You can ask me~

Secret

Compared with MSE, my PSE questions are quite compact (laymane sense) and tidy

10/11 of them were answered

Slereah

which one is the exotic matter one

Secret

5:13 PM

The still WIP one

Slereah

Rigid body?

It's not really exotic matter related

Secret

oops I mislabelled

the one benath it

actually

The question in its current state is quite satisfactory because the answers ties to the question nicely

Slereah

Well if you are too liberal with negative energy in your theory there is indeed quite a risk of VACUUM COLLAPSE D:

If there is no minimum energy, fields just drop down infinitely, emitting an infinite amount of energy

In existing negative energy states this isn't much of a problem though

Secret

yup, this has been hinted in the comments in "Is is possible to have a ghost mode that is also tachyonic?"

Slereah

Well, define "possible"

It has been talked about, certainly

Ghost fields were somewhat of a popular topic in the 90's because they were a candidate for accelerated expansion

Secret

5:18 PM

are they commonly employed to model the inflation period or dark energy at those times?

Slereah

Not really, no

As far as I know currently inflation is mostly thought to be from symmetry breaking

(false vacuums contribute to the cosmological constant, from what I recall)

Secret

I see

Btw That ghost field question has been answered, and I suspect it is more voted due to its close ties with theroetical physics or contemporary research focuses

My most highly voted question of my 11 ones is the magnetic monopole one, because despite of 50 years of no signal, it remains as a very hot topic

Slereah

Well topological defects are a common feature of QFT

That has never been observed

it is somewhat frustrating

Secret

and that 50 years of no results is what caused me to be prompted to ask in the opposite direction

Slereah

Well, they are not guaranteed to exist, even in QFT

They depend on initial conditions

and they can't form, since they are linked to topological charge

(although you can have very similar structures forming)

Secret

5:26 PM

I think I have read about them (such as the GUT monopoles) that they are postulated to form by phase transitions as the universe cools down after the big bang, which then the expansion then diluted their distributions

Slereah

They are also not 0-1-2 dimensional structures, despite what is said in pop science

They are indeed built around a string, point or surface, but it's not a discontinuity either

Secret

GUT monopoles are like an onion
Dirac monopoles are connected by a dirac string

Slereah

Of interest if you need them for sci fi things, though

There's a paper about the Casimir effect generated by a domain wall

It is quite interesting

It's a nice addition because doing QFT for the real Casimir effect is quite complicated since it's around a periodic structure

But a domain wall, that is pure QFT you can do by hand

Secret

link to the casmir paper?
Speaking about casmir effect, I think one of the most frequently mention topic about it is photon generation from the vacuum between after you somehow mess with the plates (detaisl forgot) and also the repulsive casmir effect whcih is of great interest to nanotech because it gives another way to manipulate the nanocomponents

Slereah

Do you mean the oscillating mirror

Secret

5:32 PM

I think so, I vaguely remember it is something oscillating

Slereah

arxiv.org/abs/gr-qc/0205134

Secret

popsci likes to report that phenomenon as "making light out of nothing"

Slereah

arxiv.org/abs/hep-th/0301202#

arxiv.org/abs/hep-th/0002179

You can generate particles with an oscillating boundary, yes

It's an old QFT in curved spacetime result

Secret

I am still MILES away from understanding the details, however

Slereah

what is your story about, by the way

Secret

5:36 PM

^ will be answered in next post

O btw this is what I read when I was grade 11, and later year 1:
http://arxiv.org/abs/1105.5587

and that is precisely how I know slightly more about monopoles before I do uni physics

Slereah

Well if you need weird spacetime things, feel free to ask me :p

It is my favorite topic

Secret

I have not decided the story yet, but I kinda have the setting set

and the most important of these is (and the reason why I have bee nreserarching about time travel for 3 years):

Time travel for civillain that is as common as travelling in airplanes, and it works by back to the future style (because I hate fate!)

It is a massive project, driven purely by my interest and desire to jot down the ideas I came up since grade 4

http://secretuniverse.wikia.com/wiki/Secret_Wiki

Slereah

Back to the Future is indeed best

Secret

another important topic is negative mass, which is used to make wormholes

In fact, my negative mass article is one of the highly visited articles there, there's even one instance where Richard Hammond left behind a comment to refer me to it for ideas

but attempt to connect with him had so far received no response, probably because Iscrew up in writing that email and make it sounds more like an advertisement campaign

The scifi is the primary reason I end up reading a lot of monopole articles, and arguably the first time I read journal articles (which at that time it is way over my head thus I can only pick bits I understand at that time)

Slereah

I'm not too fond of magnetic monopoles because the math is kind of horrid

domain walls are much easier to grasp

NeuroFuzzy

5:45 PM

I feel kind of silly... I'm struggling to prove basic Lie algebra stuff in smooth manifold language.

Secret

The progress in the worldbuilding of the scifi wiki was hindered mainly because I am still working on a back to the future type time travel that is comparable to general relativity concepts, which involve a lot of cross checking to ensure the maths behave the way expected for general relativity

which explains why there isn't much there, except articles which are products of some of my emotional tantrums

NeuroFuzzy

Like, if I work with "the representation of a Lie algebra" all the proofs become trivial. If I work with "a left invariant vector field on a smooth manifold with Lie group structure" I waste hours.

Slereah

GR time machines tend to not work out too well

I did send a mail to Visser about a loophole I am wondering about, but still no answer!

Secret

and GR as far I know, are not very compatible with back to the future sytle time travel (also knwon as type 3 time travel)

Slereah

well there's no "leaking" of causality

In any physics thing

it's just a plot device

Secret

5:48 PM

GR makes good "everything set to stone, i.e. type 1" time travel, though
Just CTCs is sufficient to do the job

Slereah

you can look up branching spacetime for the other kind

But there isn't much

Secret

are they related to evett's many worlds interpretation, in that the branching spacetimes don't interact with each other and are branched because of soem events?

Slereah

kinda

there isn't much work done on them

Basically spacetime has branching points at events where it can split into several copies

Secret

I think I have considered something similar before in my time travel model, but maybe my maths is not refined enough to join the dots

Slereah

It is not nice math.

FenderLesPaul

5:54 PM

my language teacher pulled me out of class today and told me I need to work harder because I'm way too behind

feels like high school :p

Slereah

It looks like this : dl.dropboxusercontent.com/u/19940612/…

Secret

Back in 2010, I used to be a big fan of many world interpretation (and its lax version in popsci, which allow the copies to interact (hence the term parallel universe)),

but then somewhere in 2012, I found that the interpretation has some issues (such as energy conservation given so many universes are produced every second and (forgot hierachial or something problem).

Its lax version suffer even more. From analysing more than 30 works of time travel in novels, games, and other media, I found that it is simply WAY TOO MAELABLE and hence PRACTICALLY UNFALSIFIABLE to be useful in prediction …

Slereah

The MWI is an interpretation of QM

0celo7

@FenderLesPaul that's what you get for being a bum

NeuroFuzzy

@Slereah yayyy point set general relativity!

Slereah

5:56 PM

It's not really made to have testable predictions

0celo7

@NeuroFuzzy don't you have Hawking-Ellis

Slereah

Also as far as I know it has no problem with energy conservation

NeuroFuzzy

@0celo7 Yeah but at least THAT'S hausdorff

Slereah

There's one non-Hausdorff manifold in HE

The Taub NUT spacetime

FenderLesPaul

@0celo7 I think she knows I don't give a shit about the class but for some reason gives me good grades every semester

I know absolutely nothing about the language :p

Slereah

5:58 PM

I like how he calls them Y-manifolds

0celo7

are you in an inappropriate relationship with her

Slereah

Because Y is a branching :p

FenderLesPaul

no

Slereah

IT IS A FLUX CAPACITATOR

FenderLesPaul

the only thing I've been in a relationship with is insomnia cookies

still can't gain weight though

Secret

5:59 PM

^^lol

FenderLesPaul

hey it isn't funny :(

I've been trying to gain weight for 4 years

literally haven't gained a pound

Secret

No I am responding two post up, i.e. Sleareah

Slereah

Chocolate bars are the secret

FenderLesPaul

I can't I'm allergic to chocolate

Slereah

Lard then

Secret

6:01 PM

but I don't want to make that bump noise by tagging sleareah

hence the two "^"

NeuroFuzzy

@Secret Oh.

@Secret good idea!

@Secret Now I won't have to inflict that bump noise on people again.

0celo7

no one is allergic to chocolate

also what on earth are insomnia cookies

Secret

^^It only works if the post are not far away

NeuroFuzzy

@Slereah huh, I didn't know that.

Secret

otherwise who would like to read somehting like $\text{^}^{88888888888\dots}$

Slereah

6:04 PM

Non-Hausdorff spacetimes aren't used that much, though

They are not particularly useful

FenderLesPaul

wtf when are they ever used?

Stan Shunpike

@0celo7 nice profile pic

Slereah

They are sometimes proposed as an alternative QM interpretation model

Where each branch corresponds to a quantum measurement or whatever

But I have never seen an actual formulation proposed

FenderLesPaul

@StanShunpike it stands for Timmy Turner

0celo7

@StanShunpike thank you

Secret

6:05 PM

that's really sounding like Evett's

Slereah

Usually it's just like "Here's the topology of the space, now use your imagination"

Stan Shunpike

@FenderLesPaul cmon, lol. Thats a vols logo

0celo7

> PROHIBITED ITEMS
Weapons ~ Alcoholic beverages ~ Cans, bottles, coolers ~ Radios without headsets ~ Open umbrellas ~ Video cameras
Stadium seats with arms ~ Large bags or parcels, including backpacks and large purses ~ Artificial noisemakers

that's no fun

Slereah

Weapons ~ Alcoholic beverages ~ Cans, bottles, coolers ~ Video cameras < sounds like the week end I'm planning

Stan Shunpike

Every phone has a video camera

Wtf

Slereah

6:07 PM

Explosives and booze

Stan Shunpike

@yuggib a "mathematical convenience", that's a nice way of phrasing it.

0celo7

tomorrow at 1800 this campus will be going nuts

@FenderLesPaul GR talk, don't be a bum

obe

tfw you left shankar on the public transit.

0celo7

tfw your roommate turns off the light and you're still in the room

seriously

obe

time to look in lost and found...

0celo7

6:12 PM

he leaves the bathroom light on but now I'm in the dark

@obe wasting time...

obe

i'll look later.

i have a pdf.

FenderLesPaul

@0celo7 ok

I'm only a bum when it comes to general education classes :p

because I give zero fucks about them

0celo7

are you at home

where are you

when will this happen

FenderLesPaul

no I'm in my office

sometime tonight?

0celo7

you need to work in the office

you are a bum

FenderLesPaul

6:14 PM

nuhuh

cries

obe

What is the T for 0celo7?

your university?

FenderLesPaul

Timmy Turner

dmckee

@Secret There is a process for having your account deleted, which is what happened in this case. The user was not subject to any moderation activities. As far as we know he was simply frustrated that the site wasn't what he wanted it to be.

Slereah

Temujin

The university was founded by Genghis Khan

Secret

@dmckee I see, thanks

@Slereah One of the most unaddressed plot point in back to the future style time travel stories is that how does spacetime look to an outsider, that is, how will history be look like to people who are not the one who initiate the change (since on TV, the change often took place when we saw the characters making a change). Another question that is poorly addressed is that why the change took place only at the moment when the change is made (see examples in Looper, Primer, and of course back the the future , there are a couple other examples also)

Slereah

6:19 PM

The most unaddressed point is HOW DOES BIFF GET BACK TO 2015 IN BACK TO THE FUTURE 2

Secret

Using the De Lorean?

Slereah

But why did he not come back to the alternate timeline he created's future

0celo7

@obe home game tomorrow

obe

@0celo7 I was sleeping and that message at 100 vol. scared me.

Slereah

Speaking of Genghis Khan

Did u know

obe

6:22 PM

What game is a home game?

Slereah

In the 13th century, the most powerful christian in the world wasn't the pope

It was a Mongolian priest

0celo7

what is wrong with {world - Americans}

Slereah

Yahballaha III

Secret

^x8 that I am not sure, I have not conpletely finished the analysis on Back to the Future

0celo7

it's a god damn football game played in the home stadium

Slereah

6:23 PM

Ruler of the church of the East

obe

We don't have that in canada. I think.

FenderLesPaul

what's football?

Slereah

Because most of the population was in that region back then

FenderLesPaul

you mean handegg?

Slereah

Really I'm not sure any time travel movie ever really did anything that didn't fuck up the plot

Books can do okay but movies are usually meh

Even Primer is kind of fucky

Secret

6:25 PM

Primer is as far I know the only time travel story that explores gradual bckground time travel

Slereah

One thing that annoys me in time travel movies and such is that usually

Time travel is ALL AT ONCE

There's no gradual development of the technology

It's all "We have time travel now"

0celo7

what is handegg

Slereah

We can send people through

@0celo7 : American football

0celo7

no, american football is american football

Secret

Soem stories have establish the time machine's timeline though, such as how some scientist made a time machine, and then the plots starts from that

a lot of them nowadays that are not type 3 tend to follow wormhole like time travel schemes

that is

Slereah

6:27 PM

Have you read the end of eternity

Quite fucky but a fun story

Secret

not yet

I have not read The Time Machine yet also, though I have analyse the novel of The Time Traveler's Wife

NeuroFuzzy

Is talking about Lie groups in terms of smooth manifolds and not using matrix representations, all that useful?

Slereah

Time travel is kind of a weird concept

Because it's one of the rare fictional concept that is very recent

the idea of travelling to the past didn't exist before the 19th century

obe

@Secret The time machine is a great book.

Slereah

@NeuroFuzzy : Define useful

Secret

6:29 PM

I have a copy of that, I just need to squeeze itme from my chem honours to read it

Slereah

It is certainly done a lot

NeuroFuzzy

Hehehe I'm unable to define "useful"

Slereah

you know math people

They hate representations of mathematical objects

Secret

My currently WIP model that I plan to use in my scifi is kinda simialr to the ADM formalism, in that instead of having a static spacetime manifold (as how GR works) the whole thing is dynamic, evolves with the proper time of the observer

To comply with relativity princple (and because it evovles with proper time), the manifold itself depends on the observer (basically extending length contration and time dilation to the global structure of the manifold)

What I need to iron out is that whether the maths are actually compatible. I suspect the tensro covariance suggested by Acuriousmind migh…

0celo7

@NeuroFuzzy useful means it makes money

obe

6:34 PM

Dude what happened to you?

Were you always like this?

Slereah

Be carefum

ADM formalism outright forbids time travel!

Secret

Above comments showed I really have not read enough stuff. Anyway this is a LONG personal project, thus I just need to take my time to get the basics right

"One cannot understand time travel without mastering both GR (and its variants) and quantum mechanics"

Slereah

Pretty much

You need a foliation to do ADM correctly

Slice up the spacetime into nice spaces at points in time

Which you can't do if you have causality shenanigans

Danu

@ACuriousMind I feel like you had a post containing a more accurate & eloquent version of the rant I posted here:

1

A: Schwarzschild metric, change in coordinates corresponds to change in object?

Your observation is correct! The issue is one that is regrettably rather commonly left unexplained in physics texts: A single coordinate system on a manifold does not define the spacetime. Often, the coordinates useful for computations in physics do not even cover the entire space, i.e. they are ...

Any idea what I'm talking about?

Slereah

Ah, the Skeksis coordinates

Danu

6:45 PM

@dmckee physics.stackexchange.com/a/200636/24653

What a way to get 100+ upvotes!

Also, I'm loving the new "cite" feature! Though I suspect it won't be used all too much.

Secret

@Danu This is why I am a mathematican more than a physicist, because I like to work globally whenever possible and then zoom into the special cases using assumptions

Danu

@Secret Yes? :P

@Secret Hah, thanks for complimenting my accuracy, I guess? :P

Secret

I first learnt about terms like chart, atlas, pullback in sean caroll's lecture notes

one thing I like abotu topology is that it is quite visual

Danu

@Secret That's not topology, though :P

Secret

a lot of concepts can be illustrated with pictures with annotations

oops, I mean differential geometry

Danu

6:49 PM

Carroll's book is where I, too, first heard these words.

However, it didn't teach me much. I needed a more extensive treatment.

Slereah

well topology is somewhat visual too, usually

Danu

This is my 600th consecutive day online on Physics Stack Exchange!

Slereah

On 9/11

Secret

^^cool

Danu

Who can beat that? I think it's longer than @ACuriousMind has even been a member!

@ChrisWhite Maybe?

Slereah

6:52 PM

visited 430 days, 77 consecutive

Damn

Danu

I think I've missed only a single day, discounting the first 30 days after becoming a member

Slereah

I want to post more but that would require being at home more :p

Can't write long ass post at work

Rigor

@Danu congrats

Danu

@Slereah For the past two days, I've really been in the mood for making some posts :)

Slereah

My favorite posts to answer are the one where everyone says "No!"

And I am like "OF COURSE"

And I whip out some weirdo paper

Danu

6:58 PM

@Slereah Yes, we know you like CTC's :P

Slereah

I DO

It's too bad that I know enough about them to know they are probably impossible :p

They have that weird cycle of papers where some guy says "MAYBE CTC POSSIBLE"

And someone else replies "CTC TOTALLY IMPOSSIBLE"

And then back again

Currently the chronology protection thing seems pretty hard to break though

That plus the whole "Any time machine in the future of a Cauchy surface can also develop into another metric in the future"

(although those Cauchy developments have singularities in them, so pick your poison)

Though singularities are probably easier to get rid of with QG than CTCs

(I can talk about CTCs for hours but I will feel less insane if someone answers :p)

Danu

7:16 PM

@Slereah You killed the h bar.

Slereah

Someday I should make a big folder of CTC papers and put it online

THE WORLD MUST KNOW

user54412

7:54 PM

@Danu My best streak was 566 days, from 2012-07-30 (about when I joined) to 2014-02-15. Then SE was down for enough hours I couldn't log in :(

user54412

Feb 17 '14 at 1:04, by Chris White

nooooooooooo - the network was down, thus ending my 560+ day streak

user54412

I was never diligent enough since, and so I miss about 1% of days.

dmckee

@Danu I owe it all to the HNQ. It's certainly not my best answer, after all.

user54412

@dmckee I upvoted that before it was popular to do so ;)

dmckee

It's not a bad answer or anything. It, just very popsci: pithy, accessible and short.

Slereah

8:04 PM

That is the most valuable answer

"What happens if I bike on the moon" is gonna net you more points than "analytic and algebraic topology of locally Euclidean metrization of infinitely differentiable Riemannian manifold"

user54412

While there might be a correlation between votes and difficulty level, I'm pretty sure there isn't much of one between votes and intrinsic quality.

user54412

I think it's just that most answers aren't intrinsically awesome (or else we would redefine "awesome") -- mine certainly aren't -- so the HNQ effect is more likely to land on less awesome Q&As.

Slereah

It's pretty hard to gauge answer quality, though

user54412

Of course we only have two data points trying to counter a widely held anecdotal feeling.

FenderLesPaul

8:22 PM

@Slereah CTCs are a lie

man

Hobson's GR book is terrible

Slereah

They are still quite interesting

FenderLesPaul

I was just kidding lol

Stan Shunpike

Hello

Slereah

I am pretty annoyed when someone answers "X is a theoretical construction, you shouldn't ask questions about it!"

Stan Shunpike

I agree. Everything should be questioned. Questioning either reminds you how cool something is because it is true or you find a hole in it and it turns out to be wrong.

Slereah

8:35 PM

Plus it can be helpful to think about existing topics

Danu

11:08 PM

@ChrisWhite muahahaha, I reign supreme! (601, baby!)

Danu

11:33 PM

For all y'all popcorn munchers out there:

Check out the fight between Alfred Centauri & Gottlieb:

Michael A. Gottleib, if you aren't pulling our legs, and if you have any sense of self-esteem, you should delete this adolescent nonsense and hope that it is soon forgotten. - "I intend to remove myself (for a second time) from the Physics Stack Exchange, only this time permanently, which would be a loss for you" - Check your premises... — Alfred Centauri 23 hours ago

Me-owww!

@JohnDuffield Now that's a hilarious thought.

0celo7

11:45 PM

I volunteer to be a moderator too

@skillpatrol there's literally hordes of Oklahoma fans patrolling the streets

and I have to do laundry tomorrow, I need my white clothes

obe

I am dying from anxiety.

I can't even read anymore.

Idk what to do.

@obe From what?

Preparing for QFT.

@Danu eh

@FenderLesPaul

11:55 PM

that Gottlieb guy has always been a prick

0celo7

are you ready

FenderLesPaul

high on his own position

0celo7

tomorrow will be absolutely nuts

FenderLesPaul

what's tomorrow?

0celo7

over 100,000 people on campus D:

it's gonna be insane

FenderLesPaul

11:56 PM

wtf why?

0celo7

::shakes head::

NeuroFuzzy

@obe you should practice shutting off the part of your brain that worries ^^

0celo7

football

why do you think I changed my avatar

FenderLesPaul

oh

0celo7

first home game of the season

FenderLesPaul

11:57 PM

right that's a thing

obe

@NeuroFuzzy Though 0celo7 said that I'm screwed as an understatement.

NeuroFuzzy

@obe that's also the reason you have TODO lists/schedules: You can plan out, the day before, "I'll just work on these problems", and then when the time comes and you're anxious because you're not doing something else, you shut that part of your brain off and say "it's on the todo list, past me knows better than present me."

obe

@NeuroFuzzy I'll listen to this advice, thanks.

FenderLesPaul

Man if people could shut off the part of their brain that worries

life would be quite something

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