Class Project

Disclaimer: I am not a physicist, but, hey, neither is Brennan.

Thanks to Robin Lee Powell for translating the inscription that Yin found.

I love these quasi-futuristic exchanges you've come up with. They're really helpful for putting your other posts into perspective - not just facts, but what facts mean for the way we should look at the world.

This is the limit of Eld science, and hence, the limit of public knowledge.

Wait, so these people are doing this only for recreation?

So no multiple dimensions.

You want to make physics heightless and depthless? I suppose it would be a logical next step.

I don't see what's inelegant about more than three space dimensions. It's not like three is a special number (as far as I know).

Make it zero dimensions and call it a "day." All else is Maya.

This is the limit of Eld science, and hence, the limit of public knowledge. Wait, so these people are doing this only for recreation?

No - this is Eliezer's alternate universe storyline in which the science-equivalent is treated as a secret the same way the Pythagoreans did. The initiates - the people with access to the secret knowledge - use it for technology, just as we do, except because the general public doesn't know the science, the tech looks amazing.

The idea, I believe, is to reduce the attraction of bogus secret societies. In Brennan's world, anyone who made one would be challenged to accomplish as great or greater feats than the Bayesians - a task that a mere mystery cult would fail at.

Joke solution:

We're living in a simulation, and the reason GR and QM don't mix is because we're living in a buggy simulation. ;)

Sorry if I'm getting myself derailed, but is there any particular purpose to metaphor of the "Cooperative Conspiracy"? It seems to be smuggling in some kind of critique of group-think, although because this particular conspiracy isn't fully defined the nature of the critique isn't clear. (Although the team claims he is "rumored" to be a member of this conspiracy, they do not seem to be largely alarmed, indicating some measure of philosophical tolerance.) Is the cooperative conspiracy a metaphor for some behavioral phenomenon well known or apparent among researchers?

This is a pre-existing world I built, where the Cooperative Conspiracy is one of many conspiracies struggling in the shadows for control of humankind's destiny.

As for whether the Cooperative Conspiracy is a metaphor for anything, I don't believe the Bardic Conspiracy would want me to answer that question: they hold that people should be free to put their own interpretations on stories.

And on Day 26 they rediscovered string theory, and saw that it was good.

What is the argument behind the confident negative attitude towards string theory/M-theory? I am not a physicist, but in layman's eyes it seems elegant. Is there any special argument or is it just general skepticism towards big unproven theoretical models?

Robin B., I can't speak for Eliezer's characters, but I believe the fashionability of skepticism about string theory has come from the lack of falsifiable predictions, after so many years. No-one has been able to say "this is the ground state". Instead string theorists have studied a large number of possible ground states (distinguished by background geometry), most of them looking nothing like what we see, as they try to get a grip on the theory. The hope used to be that all but one would prove on further study to be unstable. Now there's an interest in anthropic predictions, though that's just one school of thought.

I have read that no-one has ever exhibited a string-theory ground state exactly reproducing the Standard Model, though you can get close. That has to be significant. If such a place can be found in the space of ground states ("moduli space"), you could then try to reason out why it was dynamically favored. And we'll get more information within a few years from the Large Hadron Collider, which will establish whether there's a Higgs boson or something else (I bet on something else; the Higgs was just the simplest way to make a tractable theory and lingers by default).

In string theory's favor is that it generically has spin-1/2 particles (fermions), spin-1 particles (gauge bosons), and spin-2 particles (gravitons). That's a neat trick. So I tend to think either that it is the answer, or that it is just a beast of so many parts that anything you might look for is in there somewhere. In the latter case, it could be compared to the Monster group, the "largest sporadic simple finite group". There are infinitely many finite simple groups, just as there are infinitely many possible field theories, and most of those groups resemble some subgroup of the Monster, just as string theory has spin-1/2, spin-1, and spin-2 fields, just like the real world. It could be that string theory is just the "maximally complicated field theory" (and in fact, mathematically, it has a relationship to the Monster) and that it derives this generic pseudo-predictiveness solely from that. It has a little bit of everything, so anything looks a little bit like it. It would certainly be a mistake to take some real object, like Rubik's cube, discover a few facts about its symmetry group, and then announce that its symmetry group must be the Monster, just because the Monster has subgroups with those properties. It could be that string theorists are making a mistake like that.

On the other hand, what's the alternative? The phenomenological approach to particle physics is just to postulate enough fields with enough properties to explain what you see. You can treat gravity as just another field, contingently present, but then your theory becomes mathematically intractable. Part of string theory's appeal is that you can calculate graviton-graviton scattering, etc., unlike any previous theory of quantum gravity. But the price is that you buy into the unification philosophy. Recently, there have been claims that "contingent" theories of quantum gravity - according to which reality is just a bunch of fields plus gravity, and there's no deeper reason as to why it's that combination of fields - can be made to work; this is the "loop quantum gravity" research program. It's my judgement that string theory is mathematically much more solid. The loop quantum gravity researchers have had to backtrack several times, after making ambitious claims about the construction of consistent "gravity-plus-anything" quantum theories. Right now the evidence (in my semi-lay opinion) points in the other direction, that gravity needs to be part of a larger ensemble of fields with special properties if it is to be quantizable. Which suggests string theory.

How would this Bardic Conspiracy have any real power? Clearly these are storytelling hobbyists in some post-Singularity world, and the others are Bayes hobbyists, wisdom-of-crowds hobbyists, and moral virtue hobbyists.

the two are one and cannot be divided even conceptually, as was accomplished for inertial mass-energy and gravitational mass-energy

Only partly true; it's still a mystery why resistance-to-acceleration-caused-by-electromagnetic-forces has anything to do with propensity-to-curve-spacetime. (You can distinguish between "active" and "passive" gravitational mass.)

I really, really hope that you aren't going to try and publish a theory of quantum gravity, for practical reasons; even if it's more elegant than every other theory yet proposed, the lack of experimental evidence and your lack of credentials will make you seem like a crackpot.

resistance-to-acceleration-caused-by-electromagnetic-forces

Actually never mind that part, this ends up in the Hamiltonian you were talking about via potential energy so you already mentioned this mystery. Still, saying "passive gravitational mass is conceptually the same thing as inertial mass" is more accurate than saying "gravitational mass is conceptually the same thing as inertial mass".

You assume too much about this world, steven.

many conspiracies struggling in the shadows for control of humankind's destiny.

It is Eliezer's fictional world, but I would enjoy it more if one of the conspiracies -- perhaps called the Nonhumanist Conspiracy -- did not particularly care about the destiny of humankind except to the extent that humankind is instrumental to the destiny of something bigger like the universe or the all-there-is.

"Sacred language of science" is a contradiction. I like the story so far, and the inclusion of Lojban.

stevo

Perhaps, Richard, such a group does exist, but its members are not humans.

Hrm... I have several thoughts in relation to this... One perhaps being that we need to perhaps look for a way to replace the energy term with a stress energy tensor...

But, perhaps a more specific interesting thought that I have here relates to almost an "opposite" thought I once had:

Can the space in which the quantum amplitude vectors (forget that they can be decomposed as complex numbers for a moment) move around itself be curved?

Well, this post got me thinking of that again... What would it look like for the "complex plane" to be curved? Well, one form that could take would be to allow an angle other than 2*Pi to be the angle which corresponds to the angle "spinning all the way around"

So, what's that look like? Well, in some form of units, the arrow's state can be represented as something like this:

e^iAx

where x is some measure of distance in configuration space and A is some coefficient...

Wait... does not energy itself show up somewhere in that A?

and if initially x was proportional in some fixed way to angle, would not that A somehow correspond to then a curvature of the complex plane, a change in the angle needed to go all the way around?

So it does look like, at least from one perspective, what energy is doing in QM directly corresponds to something sortakinda like curvature.

Except... you can always locally redefine your distance-in-configuration-space units to make A = 1 or whatever, at least locally... so maybe something along the lines of the change in A, or what A "looks like" given different subspaces factored out of the configuration space.

I have one or two mathematical "toy" ideas I want to play around with regards to that, but it's late, and still I need to think about it a bit more, but, well.... That's the basic notions I've got from the above suggested question.

Anyone else want to go somewhere with that, or smash it? :)

I am here to report that the reasons QM and GR don't like each other are: Short answer: they are competing with each other

Long answer: There is a term that appears in perhaps different forms in both sets of equations that is counted twice. This possibly involves a factor that one of them is multiplied by. That factor may be as Psy-Kosh said a question of flat space versus curved space.

The existence of that factor prevents cancellation or some other thing which gives us infinities.

First find that term and the factor and eliminate them from the equations. Recalculate the constants so that it is no longer necessary. Next make sure the constants are the same over both theories. Combine the final shape of both theories. The next step is critical:

If you still get infinities, make them go away. Relate the way you made them go away to that term and factor.

extirpate that which permits them

link is broken, should point to http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.41.3367

Actually Brennan's idea is common knowledge in physics - energy is derived as the generator of time translation, both in GR and in QFT, so there is nothing new here.

Taji looked over his sheets. "Okay, I think we've got to assume that every avenue that LessWrong was trying is a blind alley, or they would have found it. And if this is possible to do in one month, the answer must be, in some sense, elegant. So no multiple agents. If we start doing anything that looks like we should call it 'HcH', we'd better stop. Maybe begin by considering how failure to understand pre-coherent minds could have led LessWrong astray in formalizing corrigibility."

"The opposite of folly is folly," Hiriwa said. "Let us pretend that LessWrong never existed."

(This could be turned into a longer post but I don't have time...)