The h Bar

Captain Bohemian

05:44

thundering again and starting to rain

I don't like raining in the afternoon

Captain Bohemian

05:56

that you don't have appetite doesn't mean you can't feel hungry

@bolbteppa Asteroid (66391) 1999 KW4 consists of a primary space rock just under a mile wide (about 1.5 km), with a 0.3-mile-wide (0.5-km-wide) companion asteroid – an asteroid moon – orbiting the main asteroid.

After asteroid 1999 KW4 passes by Earth on May 25, 2019 in about 13.5 times the Earth-moon distance, no known asteroid as big or larger than this space rock will approach our planet this close until year 2027.

On June 6, 2027, asteroid 4953 (1990 MU), a 4 km to 9 km (2.5 to 5.5 mi) space rock will safety pass by Earth at 12 lunar distances, and will return on 2058 at nine lunar distances.

during these days when the weather is so hot, I don't really have appetite to eat a usual hot meal though I still feel hungry. Nevertheless, I force myself to eat just to stave off hunger.

I only have the appetite to eat ice.

hunger is a persistent illness whether you like to eat.

whether when it's convenient to reach food.

surprising the rain seems to stop after persisting for several minutes. Then I can go out to solve hunger with convenience.

Slereah

07:11

Trying to write an article on 0-dimensional QFT for the website

Talking about the differential geometry of 0-manifolds is quite fun

Novalium Company

08:03

Can an electric field exist between two perpendicular conductive plates? (instead of parallel)

Slereah

10:17

Math wizards

I need your wizardry

Is there a list of like

Linear functionals depending on the type of function space we consider

ie : what type of integral is a linear functional depending on what function space we consider

For instance some Lebesgue integral for rather nice one

But a stochastic integral for naughty ones

Slereah

10:43

i guess it's like the dual space of said functions but then again the dual may include functionals which aren't integrals

It's hard to find infos on holder continuous integrals that aren't part of stochastic shenanigans

ACuriousMind

10:59

@Slereah There are plenty linear functionals that aren't integrals!

differentiation and evaluation, to name two

Slereah

True

But is there like

A canonical integral associated with each function space

Or somesuch

I dunno

ACuriousMind

I don't think so

Slereah

Trying to think of a good way to associate the correct configuration space to path integrals

ACuriousMind

Of course e.g. $L^p$-spaces have Lebesgue associated with them, but that's a tautology since they're defined by it :P

Slereah

And since the holder continuous functions aren't lebesgue integrable etc etc

ACuriousMind

11:03

If you're interested in integration properties, then I guess you always define your function space precisely as the integrable functions with respect to the integral you want to use

@Slereah In QM, it's just the Wiener space (i.e. all continuous functions).

Slereah

@ACuriousMind True, I do suppose it's just that the other ones are just of measure $0$

Are all continuous functions integrable with a stochastic integral?

(on a compact region)

ACuriousMind

Well, in the path integral, you're not integrating the functions, you're integrating over them!

Slereah

Well sure, but you're integrating with respect to the action functional!

it needs to be defined over that space

IIRC Chaichian even shows that you can integrate over discontinuous functions and it is also of measure zero

although I'm not 100% sure it's rigorous

Hell I think Cecil DeWitt does talk about that kind of nonsense

Defining path integrals with respect to some dual of the Banach space of the configuration space

ACuriousMind

@Slereah All continuous functions are Riemann/Lebesgue integrable over closed intervals.

You don't need anything fancy to define the action functional there

Slereah

@ACuriousMind I thought that wasn't true for like nowhere differentiable functions?

ACuriousMind

11:09

It is true.

Slereah

Hm

why do we need the stochastic integral then

ACuriousMind

Who says we need it?

Slereah

Most books on the topic

ACuriousMind

Are you now talking about the path integration again?

Slereah

Well, I'm talking about the action term in the path integral

ACuriousMind

11:10

Because the path integral w.r.t the Wiener measure is a stochastic integral, if you will

@Slereah OH

The problem is not the notion of integration, it's the derivative in the integrand of the action

Slereah

Ah yes

True

Hard to define the derivative even weakly

I wonder if you could define a path integral over $C^1$ functions instead, and show that it is always zero

ACuriousMind

How could it be?

If you only define your measure on $C^1$, the integration over the whole space cannot be zero, or you didn't have a measure to begin with

Slereah

Well I'm trying to see like... generalities about path integration

ACuriousMind

Read Glimm/Jaffe

Slereah

Take a configuration space $\mathcal{C}$, define some linear functional $S$ on it, define some measure $\mathcal{D} \phi e^{-S}$ on it

It's hard to be sure what's important or not since most books have a very specific action in mind

Yeah I should also read Cecil DeWitt's book on the matter

I think she keeps the configuration space vague for most of it

ACuriousMind

11:16

@Slereah Glimm and Jaffe don't - at least for the first parts of the book where the general machinery of path integration is established

Slereah

Chapter 3 you mean?

ACuriousMind

@Slereah Everything up to 10 or 11 when they start getting very specific to d=2, really

Slereah

Having the zero dimensional case does help since it's a fairly different Banach space

ACuriousMind

Given the enormous amount of machinery that goes into defining path integration on their very specific spaces, I think your idea of doing some "general" path integration on generic function spaces is far outside the current power of our formalisms

We don't even know how to do it for d > 2 in the general case, and not at all for d > 3 last time I looked

Slereah

Well fortunately I'm focusing on zero and one dimension now

Zero's fairly alright :p

It's unfortunate that we don't live in zero dimensions

Like the point in Flatland

^me hanging out in one dimension

Loong

11:27

Also, I apologize for the time I climbed down into your world and everyone freaked out about the lesbian orgy overseen by a priest.

Slereah

heh

The Planiverse is a much better version of Flatland, btw

One of my favorite genre of books is "Weird physical laws", which is unfortunate because there's like a handful of weirdoes writing that kind of book

Greg Egan being a big one

What is the space in the worldline formalism, by the way

For a single particle it's just a 1-manifold, but what about the branching case

Is it a branching manifold???

Is it... Non-Hausdorff???

ACuriousMind

I don't think it's a manifold, the Feynman graphs are just that - graphs.

Slereah

Could you define it on something like that tho

Sum over topologies of branching manifolds

I wonder if branching manifolds are classifiable in one dimension

I had that vague idea that branching manifolds are equivalent to non-Hausdorff ones under identification of the adjacent points

I should try to prove it maybe

At least in one dimension

ACuriousMind

11:47

@Slereah You can call them "branching manifolds" but that doesn't change anything

you won't use any "theory of branching manifolds"

Slereah

Well I mean

Branched manifolds are a thing

Branched manifold

In mathematics, a branched manifold is a generalization of a differentiable manifold which may have singularities of very restricted type and admits a well-defined tangent space at each point. A branched n-manifold is covered by n-dimensional "coordinate charts", each of which involves one or several "branches" homeomorphically projecting into the same differentiable n-disk in Rn. Branched manifolds first appeared in the dynamical systems theory, in connection with one-dimensional hyperbolic attractors constructed by Smale and were formalized by R. F. Williams in a series of papers on expanding...

ACuriousMind

you just compute the integrals over them in the "obvious" way by gluing propagators together, see e.g. chapter 3 in arxiv.org/abs/hep-ph/9412358

@Slereah I know. I'm saying that it is physically completely irrelevant that they may be branching manifolds.

Slereah

How long have you known me

Novalium Company

I'm trying to make a super simple experiment and it doesn't work. I get some electrons with a balloon from silk, I touch the balloon to an aluminium foil ball which hangs on a string. Now the aluminium foil ball should be negatively charged (has more electrons). I put another aluminium foil ball next to the charged one and they should repel, but they don't.

Slereah

since when am I stopped by something being irrelevant or useless

ACuriousMind

11:49

You can sum over "topologies of branching manifolds" or over "classes of graphs". It doesn't make a difference

@Slereah Fair point.

@NovaliumCompany Are you charging both balls?

Slereah

Also do Feynman graphs have a notion of distance on them?

ACuriousMind

No

Slereah

Time separation between two points on the graph

Well there's a difference between the two :p

Novalium Company

@ACuriousMind I tried charging both balls as well, but it doesn't work. Maybe charging by friction with a balloon is a weak method. (since I'm planning to charge titanium dioxide powder that way :P)

ACuriousMind

@Slereah They are graphs with ends that are marked "in" or "out".

There is no time order on their interior vertices

Although you could certainly pointlessly count how many vertices any vertex is away from an "in" end, and establish some sort of partial temporal order by that

Slereah

11:52

Probably

I mean having "measurements" at finite times is certainly a thing

Not everything is a scattering experiment!

ACuriousMind

@Slereah What do you mean?

You can't measure the "interior" of a Feynman graph, it's pure fiction

Slereah

Could b

ACuriousMind

@Slereah The trick is that a Feynman graph doesn't depict scattering. It depicts a perturbative term in the computation of a correlator, you can use it whenever you need to compute correlators

Novalium Company

My old TV seems to stack electrons on it's screen, cuz my hand hairs are attracted to it :D

ACuriousMind

Whether this correlator is a scattering amplitude like in HEP or some condensed matter order parameter doesn't matter in the slightest

@NovaliumCompany Sure, old TVs are essentially just cathode rays

Slereah

11:56

You can use it to make a particle accelerator if you want

(WARNING : DO NOT DO IT)

ACuriousMind

@Slereah It arguably already is a particle accelerator!

But yes, do not dismantle a TV.

Slereah

The CRT is in a big old vacuum and trying to modify what's inside is liable to have some explosive decompression

Novalium Company

Can I use the TV to charge my aluminium foil balls and see if they repel on the desk?

ACuriousMind

You can certainly try (by touching the balls to the screen, that is, not anything that involves opening it!)

Slereah

Futurama - Try this, kids at home !

►

Novalium Company

11:58

Mom, I'm making a particle accelerator, leave me alone xDD

Slereah

Oh also fucking around with a CRT is liable to produce X-rays if done improperly

u may get cancer

Novalium Company

oh shit

Slereah

Well it's fine if you don't touch to the insides

Unfortunately having a not-vacuum inside your CRT will not make a very conducive medium for electrons

You'll get brehmstrallung up the wazoo

ACuriousMind

*bremsstrahlung

Slereah

Look at mister German over here

Herr Bremsstrahlung rolling over in his grave!

Novalium Company

12:01

I think the foil balls are too heavy, and friction also stops the process of them repelling

Slereah

Get a fine dust of foil

You know one of my favorite science joke to this day remain the uncyclopedia article for the erlenmeyer flask

Loong

@Slereah electrocution will probably kill him first

Novalium Company

I just made smaller balls. The TV seems to need to recharge like 10 minutes before shooting out electrons again.

Slereah

"The Erlenmeyer flask (invented by Dr. Henry Flask)"

Novalium Company

My desk is wooden, as far as I know, the charge should stay in the balls

Slereah

12:04

@Loong Electrocution has yet to kill me

and really

Loong

Beppo Brem

Beppo Brem (11 March 1906 in Munich, Germany – September 5, 1990 in Munich, Germany) was a German film actor, who was in over 200 film and television productions between 1932 and 1990. He often played stereotypically Bavarian characters, but managed to find respect as a character actor in later years. == Selected filmography == The Bartered Bride (1932) The Tunnel (1933) Must We Get Divorced? (1933) Um das Menschenrecht (1934) The Young Baron Neuhaus (1934) Marriage Strike (1935) Knockout (1935) The King's Prisoner (1935) The Saint and Her Fool (1935) Donogoo Tonka (1936) The Three Arou...

Slereah

If you're not willing to get electrocuted

Do you even really want to become an experimental physicist

@Loong was he radiant

That reminds me of that time the boys at Los Alamos almost triggered a nuclear chain reaction in their lab by accident

Novalium Company

I just realized the TV won't charge my balls, because they have no physical contact to the electrons themselves.

Slereah

IIRC it was something like just being present near the reactor caused the water in their body to reflect neutrons back onto the pile

Loong

@Slereah I would have to check that particular event. However, that kind of moderation and reflection is actually taken into account in the criticality calculations for dry storages.

Nevertheless, fire water would be worse.

@Slereah And they also did this: en.wikipedia.org/wiki/Demon_core

Novalium Company

12:10

I just charged two small (2 mm) aluminium foil balls with a balloon, put them over glass, and they don't want to repel :(( Maybe friction?

Slereah

@Loong I'll drink it for safekeeping

Novalium Company

Maybe the balls are not charged enough to repel

Is there a cheap machine I can buy that produces charge? (so I can charge objects without rubbing a balloon 100 hours)

Also, for some reason, the aluminium sticks to the balloon, it doesn't repel. (they should charge the negative charge and therefore, repel)

Loong

@Slereah So yes, if you work in a dry storage like this, you are the most important moderator:

Slereah

Remember to hug the core tight

Loong

Don't forget to eat your boron.

Slereah

12:21

Nobody doesn't like molten boron

Loong

3

Slereah

Captain Bohemian

it's very strange that a paper uses the same symbol $\theta$ for both coframe and connection 1-form and another same symbol R for torsion and curvature; the way to distinguish them is the number of their indices.

Slereah

Well why not

Same happens with riemann tensor, ricci scalar and ricci tensor

Captain Bohemian

but those are what gained from contraction

Slereah

12:35

Well $\gamma$ can be a curve or a lorentz factor

And $\phi$ can be a field, a chart or an angle

We only have so many symbols

Captain Bohemian

but that paper uses all those symbols in the same equation

Slereah

We need to start using other alphabets

Loong

@Slereah He got 3.9 Sv during that night.

Slereah

@CaptainBohemian well you're not gonna confuse them

@ACuriousMind are there restrictions on what feynman graphs are allowed in worldline formalism

Captain Bohemian

saying the truth, I am a little irritable today, so as I first read it, I was confused.

Slereah

12:39

I assume only countably many vertex

Novalium Company

Is it possible that the balloon cannot store and therefore give enough charge to the small aluminium balls and that's why they don't repel?

ACuriousMind

@Slereah I'm pretty sure you sum over the exact same graphs as in standard perturbation theory

Slereah

@ACuriousMind sounds reasonable

Captain Bohemian

12:55

@Slereah when I see $\gamma$, I first think of a Dirac matrix.

Slereah

We all see what we want to see

For me it's a curve :p

skillpatrol

@Slereah a dyslexic would see 15 instead of 51 :P

> ...apparently 2 million people are on September 20th.
A further 1,300,000 people said they were interested in the event, scheduled for 20 September 2019, and billed as "Storm Area 51, They Can't Stop All of Us", an attempt to "see them aliens." -- From Wiki.

foxnews.com/science/…

Novalium Company

13:30

I'm experimenting with rubbing a balloon on a silk (to get the electrons) and then touching the balloon to two small aluminium foil balls to see if they'll repel but they don't (if I do it with aluminium foil sheets, they stick to the balloon for some reason, and again, they don't repel). What's happening here?

My final goal is to charge titanium dioxide powder by rubbing a charged balloon in the powder. (I don't know if that will work though) Is that cheapest way to go about doing this?

Please help, I tried engineering forum but no one wants to help me :c

user129412

14:18

Coulomb blockade in a normal metal island separated by a tunnel junction requires the resistance of the junction R >> hbar/e^2. Is there an equivalent condition for a superconducting island, where it is not R that matters but the Josepshson energy Ej?

Emilio Pisanty

15:29

can anyone see any reason why this two-year-old question suddenly got seven votes in one day?

22

Q: Why does the SEDE ReviewTaskResults table not include user data, which is all public anyway?

I wanted to do some data mining on the SEDE, and I ran across a limitation which I cannot understand. The Data Explorer table ReviewTaskResults currently contains the following information: Id ReviewTaskId ReviewTaskResultTypeId (listed in ReviewTaskResultTypes) CreationDate RejectionReasonId ...

@ACuriousMind I thought it was Brennstrahlung

Emilio Pisanty

16:06

@EmilioPisanty nevermind

Emilio Pisanty

16:19

0

Q: Creating an expansion state of light with a laser

Let's say you fire a laser, but you change the source. I assume the laser is producing vortexed light, and it is initially rotating clockwise. What if you suddenly change the rotation at the -source- to counterclockwise for a brief instant, just a picosecond, and then go back to clockwise. Th...

optics

wow

is this just a thin layer of UWYA on top of a mountain of non-mainstream ideas?

JMac

16:31

I know nothing about optics but his comments sound like word salad to me so IDK

Slereah

17:11

"We also need an abstractdefinition, as our branched ^-manifolds arise quite naturally as quotients of foliations(see figures 5 and 6), but with no given embedding."

Dammit, did the inventor of branched manifold prove the thing I'm trying to prove already?

I hope not

Hm

I don't think he wrote it specifically

He mostly wrote it for foliations

But still fairly close to what I had in mind

Eh no matter

I should still write it out

Slereah

17:29

Damn guy stole my idea 50 years before I had it

Also he starts his bibliography with a reference [0]

Emilio Pisanty

@JMac and, it's gone o.o

(deleted by its author, after three very lengthy comments)

JMac

@EmilioPisanty Probably doesn't want us to steal his ideas to get credit for FTL information travel

hpekristiansen

If universes in the multiverse does not interact, how can their existence be tested? In what way is our universe different if the other universes exists or not?

Slereah

17:56

They cannot

Ryan Unger

@hpekristiansen it can’t be detected and hence doesn’t exist

Emilio Pisanty

18:37

@JMac it's not FTL information travel, it's a magical signal generator that's able to break the bandwidth theorem and all of Fourier analysis

Loong

19:54

Emilio Pisanty

23:12

@Loong is that a TIE fighter?

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