The h Bar

enumaris

12:00 AM

Even though I played MTG, I don't know any of the lore there either lol...

Semiclassical

was

I knew a good amount of MTG lore from reading the website

ACuriousMind

@heather Heh, well, just wait till the opportunity arises. I started playing with a few friends towards the end of school with the old books from my father, he was so fascinated that his defunct hobby had managed to infect a new generation :D

Semiclassical

but I never really played it myself due to the investment required

enumaris

oh it does say ex-wife

nowadays MTG is virtual

but I still prefer to have physical cards

it feels more collectible

Semiclassical

yeah, they got divorced back in 1994

ACuriousMind

12:01 AM

@enumaris I wish there was a way to play MtG without the collectible aspect

enumaris

Can't you do it virtually?

ACuriousMind

Well, but you still have to "earn" cards and such

enumaris

the collectible part is kinda cool to me tho, it's like lootboxes

lol

Semiclassical

the original Roseanne series was 1988-1996, so they were married during the tenure of that

ACuriousMind

I just wanna play the game, not grind countless hours until I'm allowed to "really" play it

enumaris

12:02 AM

but since I get a physical card, it feels much more worth it

than digital lootboxes

hmmm

Semiclassical

i'm not sure how long lootboxes have for this world, at least in their present extent

enumaris

MTG and stuff like that have been around forever

I feel like...lootboxes are probably here to stay in some fashion...

ACuriousMind

And I'm also not throwing hundreds of bucks at it - too many other games with much better entertainment value for less money out there :P

Semiclassical

yes, if by forever you mean since the 90's :P

enumaris

effectively forever

Semiclassical

12:05 AM

I agree in that I don't foresee them getting banned forthwith

enumaris

@ACuriousMind well the point is to save up some lunch money and then buy a booster pack :P

over an extended period of time

Semiclassical

but I could definitely see restrictions incoming

enumaris

not like throw hundreds at it all in one go

Semiclassical

there's already been some of that already

enumaris

yeah...seems to be...

welp, time for me to head home :D

laters peeps

Semiclassical

12:05 AM

later

ACuriousMind

@enumaris I know, I know....as I said, I'm really not into the collectible aspect

enumaris

T-T

heather

@enumaris have a good day

Emilio Pisanty

12:51 AM

yo @ACuriousMind

booom, rep cap =D

70 down

80 to go

ACuriousMind

@EmilioPisanty Congrats

Emilio Pisanty

=D thx

ACuriousMind

I see you're on a much better track to become legendary than I am :P

Emilio Pisanty

well, I guess "better" can apply to situations that you wouldn't really describe as "good" =P

anyways, I'm out, I'm knackered and I've got a flight tomorrow

g'night

ACuriousMind

g'night!

Physics Meta

2:16 AM

0

Q: Can my deleted question about be reopened?

A question I asked some time ago was deleted because it did not meet the standard of the Physics Stack Exchange website. I decided to revisit the question and modify it. Could this question be reopened?

Cows

2:54 AM

I got a hair cut today. Tomorrow is date night. :D

Sir Cumference

Anyone know some basic topology?

rob

3:43 AM

@SirCumference I know that a donut and a coffee mug are both tori.

John Rennie

@ACuriousMind etymology - noun. From etus meaning eat and mal meaning bad. It is the study of things that are hard to swallow.

Secret

4:01 AM

1

Q: Can a piece of glass get higher than the height the original cup of glass fell from?

If yes, what physics concepts make this possible? This isn't for any class or anything, is just a honest doubt of mine.

newtonian-mechanics potential-energy collision elasticity glass

There are simple but nice questions like these

Sir Cumference

4:14 AM

@rob Not exactly what I was thinking about... :/

vzn

5:02 AM

@enumaris conceptually it looks similar in some ways to geometrodynamics to me and also T + H "spacetime fabric". think it deserves further scrutiny/ analysis/ attn/ inquiry/ investigation etc. author has excellent credentials. think you have a real point about theories not being evaluated on their merits but on subsidiary/ auxillary/ circumstantial aspects, have made it myself repeatedly in here. science is a human endeavor!

David Z

6:11 AM

@Secret Personally, I actually consider that a fairly bad question

Secret

Well, it interests me because it is a small thing I never thought seriously before

student

6:24 AM

if only students would ask "good" questions, learning would be a lot easier :P

but alas, bad questions lead to a bad understanding

David Z

6:39 AM

@Secret Yeah... there are also plenty of questions which are small things that I never thought about seriously, and I do find them interesting, but interesting is not the same as good.

Secret

Right

David Z

One could definitely post a good question about the same physical situation

student

and make it interesting?

^role of a good author

good authors know how to make things interesting

exhibit A

ACuriousMind

9:33 AM

@SirCumference Had you actually written down your question I would be able to answer it now... :P

Avnish Kabaj

9:56 AM

3

Q: Why does the superposition principle for calculating equivalent resistance work for asymmetrical objects?

The method has been discussed in this question: Effective resistance across 2 adjacent vertices of a dodecahedron with each edge $r$ I used this method for an asymmetrical object to calculate its equivalent resistance. The method shouldn't have worked as the branches connecting the o...

electric-circuits electrical-resistance

Help

Plis

knzhou

@enumaris Regarding the causal fermions, I looked into this once. You have to distinguish between mathematical frameworks and scientific theories.

I would certainly believe that this guy has built a mathematical framework equivalent to (a subset of) quantum field theory, but those are like a dime a dozen.

It's like somebody writing a new programming language with 1/10 the features of existing ones. It's not remarkable that other people wouldn't be racing to adopt if it they don't have a reason to.

A totally separate question is whether causal fermions are a scientific theory, i.e. if they make specific predictions about our world.

And the paper really sells that hard, the abstract gives you the impression they somehow uniquely derived the Standard Model. Which can't be right because the SM doesn't look "unique" in any sense.

If you carefully look at the parts of the paper with "predictions", you'll always find the same pattern. Somewhere buried in 20 lemmas and corollaries he postulates the SM is true. Then 20 pages later he acts surprised when his theory outputs the SM.

Like, you don't get to say you derived the gauge group of the SM is SU(3) * SU(2) * U(1) if you literally postulated that to be the case a page earlier.

That's just an indication that your notation sucks!

Besides that SM debacle I didn't find any concrete predictions anywhere (though I only loosely skimmed). At some point he says some stuff equivalent to the modern understanding of effective field theory, but it's just the same stuff in much more complicated notation.

I formed this impression after about 15 minutes of skimming and I think a professional physicist could in half the time. Mathematical structure is cheap, you don't need to understand every last lemma to see there's not going to be a payoff.

Don't confuse "big ideas" with big page counts.

harambe

2:10 PM

Does stefan-boltzman tell us only about the radiative energy lost from a body and not absorbed by it when kept at a different temperature

Sir Cumference

2:23 PM

@ACuriousMind Suppose a function $\vec{v}(t)$ parameterizes a Jordan arc for all $t \in I$. Then can we express its tangent vector as a function of $\vec{v}$ alone, which is defined over $I$?

enumaris

4:03 PM

@knzhou Thank you for your analysis! The paper goes over my head, so I don't feel comfortable evaluating its merits. My understanding of the SM is unfortunately lacking. I could only make some general statements about physical theories and what it means to be a "good physical theory".

@vzn Unfortunately, I'm not the one that has to be convinced to evaluate this fermionic paper. I was never in that particular field, and I am no longer in academia either haha. Also, the paper goes way over my head. :P

vzn

4:38 PM

@enumaris it can be evaluated/ reviewed by anyone, ofc its highly technical and therefore some have better bkg to judge than others. teamwork helps. am not dismissing/ devaluing the negative reviews so far but maybe there is more to it than is being discussed so far. it does look isolated/ like an island right now with almost nobody but 1 working on it. think some bits )( of it seem "in the right direction".

enumaris

Well, I can certainly give an "evaluation". But it won't mean much lol.

There's no reason to expect my evaluation to be valid given it goes way over my head. And even if one assumes my evaluation to be valid, I have no pull in the physics community to get more people working on it.

vzn

@enumaris no doubt its a struggle to interpret/ parse/ translate a lot of papers, deeply technical, this ones no different in that regard. its a general challenge of the field. the "physics community" for all its briliance is still human and therefore subject to some )( groupthink/ herd mentality/ bias etc... (as you just noted...)

bolbteppa

@vzn did we find your toe

There's almost no discussion of this tbh, strange

vzn

@bolbteppa coincidentally after just running into it was poking around at the refs related to Finsters work for awhile independently/ unaware of the lively/ colorful discussion in here. am gratified to trigger some )( collective attn/ analysis.

Felix Finster

Felix Finster (born 6 August 1967, in Mannheim) is a German mathematician working on problems in mathematical physics, geometry and analysis. == Life and work == Finster studied physics and mathematics at Heidelberg University, where he graduated in 1992 with Franz Wegner and Claus Gerhardt. In 1992–1995 he wrote his PhD thesis at ETH Zürich with Konrad Osterwalder. In 1996–1998 he was post-doc at Harvard University. From 1998–2002 he was member of the Max Planck Institute for Mathematics in the Sciences in Leipzig. He got his habilitation in 2000 at Leipzig University. Since 2002 he is f...

bolbteppa

4:53 PM

@vzn he's hardly moved on from string theory if he's going to a conference on it ims.nus.edu.sg/events/2018/wstring/index.php#collapseOrganizer

vzn

2

Q: Is there a mathematical connection between Causal Fermion Systems and Noncommutative geometry?

Well, the title says it all. Upon research, many of the ideas in Felix Finster's Causal Fermion Systems (CFS) and Alain Connes' Noncommutative geometry (NCG) struck me as similar. Both theories involve triples that encode the underlying geometry, from the "objects on it" (more or less). Both con...

non-commutative-geometry

@bolbteppa ?!? lol small )( world Yau at that conference is a collaborator with Finster.

> More specifically, in collaboration with Niky Kamran, Joel Smoller and Shing-Tung Yau he studies the dynamics of waves in a black hole geometry.

vzn

5:15 PM

18 hours ago, by ACuriousMind

First major issue I note is that he defines an operator that produces values of wavefunctions at specific points. But anyone familiar with the actual mathematics of the "contemporary physics" of wavefunctions knows that the value of a wavefunction as a single point is ill-defined/cannot be physically important

↑ a possible key pivot/ bridge between old/ est. and new theory. the fluid paradigm insists (contrary to copenhagen interpretation) that the wavefn is ontological/ measuring/ quantifying something real/ physical. basically, the "density of space". ("spacetime fabric") also called "probability density/ fluid". etc

lılostafa

10:02 PM

@ACuriousMind Congrats

ACuriousMind

@lılostafa Hm? For what?

lılostafa

For the win

(Although the referee played a rather significant role in this victory by his biased judgment.)

ACuriousMind

@enumaris Having thought about it a bit more, I think knzhou's analysis is spot on - there are no true errors in this theory, it seems to be a valid re-encoding of the information contained in other theories. But in order to define one of his causal fermion systems, one needs to already know the space one wants to build it on, which is given by the wavefunctions/states of the physical theory in its standard formulation. So it is not clear what we would gain from this formulation.

For instance, the thing why string theory is so attractive is that you start from a description that doesn't seem to have anything to do with gravity or traditional QFTs at all, and at the end out pop the unique possible SUGRAs in 10d and 11d. I.e. we didn't start from the knowledge that these are the theories we wanted to describe, they just fall out.

@lılostafa Oh. Football.

enumaris

I see...

but if his theory is simply a re-encoding of information in other theories, his theory should still suffer from the same problems right? I.e. it should be unable to unify QM and GR in his theory as well.

ACuriousMind

@enumaris For that there would need to be a specific prediction for this unified QM and GR theory. As far as I've read, what he showed is that his framework can accomodate easily "QFT in curved space" in the same framework as pure QFT. It's possible that there is some improvement over the usualy semiclassical QFT+GR descriptions here, but if it is it's buried so deeply that I wasn't motivated to read that far

I mean, we do have methods that already include both QFT and GR to some extent, see e.g. Hawking radiation and other semiclassical approaches

enumaris

10:10 PM

right...

so how does the unrenormalizablilty of gravity pop up in his theory?

Cus with the current formulation, one can show clearly that GR is not a renormalizable theory. <-- AFAIK that's the reason for the claim "GR and QM are incompatible"

ACuriousMind

@enumaris That I don't know, it's probably somewhere in one of these 500 page papers but I don't have that sort of time :P

enumaris

But you expect that it's somewhere, and maybe he hasn't seen it?

because if it doesn't pop up in his theory, then his theory has something new and improved right?

ACuriousMind

@enumaris Yes, exactly - but non-renormalizability merely means that we cannot hope to use our current methods to predict anything at high energy scales

enumaris

right

ACuriousMind

@enumaris Indeed. But if he had a specific computation that showed e.g. Hawking radiation in full QFT+GR not suffering from renormalizability issues, I'd expect that to be featured a bit more prominently

enumaris

10:13 PM

fair enough

ACuriousMind

It's possible it's there, but I'd sorta expect that to be a claim featured in the abstracts instead of the rather vague "this framework can accomodate both QFT and GR" claims

On the other hand, maybe it's unfair to expect that of a theory that's work in progress.

enumaris

how old is this...

like 20 years old?

ACuriousMind

Yeah. But it seems no one but him and some students of his really has worked on it

enumaris

how many people work on M-theory?

ACuriousMind

Which is understandable - there's no "hook" he presents that really would entice me to say "Hm, if we can work that out, maybe we'll get somewhere".

bolbteppa

10:16 PM

If there's nothing wrong with it and he gets GR and QFT as limits of a quantum theory, it should be a big deal, clearly somethings up?

enumaris

(I still haven't gotten where M-theory and string theories diverge, so is it the same as the # of people working on string theory?)

ACuriousMind

While string theory is very good at having delivered intriguing relations - both physical and mathematical - at most steps of the way, even if not reaching the holy grail of a true and indisputable quantum theory of gravity

@enumaris "M-theory" is a theory that subsumes the five string theories as limits by dimensional reductions, so there's not much of a distinction between a string theorist and an M-theorist

enumaris

I see

maybe a more fair comparison

is

how many people work on non-commutative geometry?

I know only 1 person works on E8...lol...

essentially only 1 person...

ACuriousMind

But M-theory is, for instance, again such an intriguing thing that invites further study: When people found there were five string theories, that was unexpected and a bit weird. And then they slowly, step by step, uncovered this web of dualities that shows that these theories are largely just different ways of looking at the same thing - "M-theory"- in different limits

That's a structure completely unexpected if you just look at the initial starting points

And I think such discoveries are what many theorists are looking for when deciding whether a certain theory is worthwhile pursuing - can you discover non-trivial structures not evident in the initial definition, much like mathematicians like to study structures where some simple definitions imply a host of strong and surprising theorems

But, on the other hand, what do I know? Maybe Finster is just unlucky that he doesn't have as good a PR department as string theory :P

bolbteppa

We need the person who wrote the E8 article that led to all the attention for him to get writing on this one

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