bolbteppa

You come from a separate angle and ask how do we copy the fix of going from non-renormalizable Fermi theory to the SM, one can see that a string model would fix the problems mimicking how one could generalize Fermi theory to the SM

@Charlie GR only arises at low energies as the leading term, when you start to go to higher energies ST predicts correction terms and indeed that the whole approach needs be replaced by the full quantum string, it basically says who cares that the leading order term in an energy Taylor expansion is not good enough on its own its just part of a larger theory

Nobody likes the extra assumptions a string model suggests but the algebra is quite clear the floor is wide open to try to fix it, instead people go on youtube and bash science to people with no background to demonize it all for a tiny bit of ego and personal gain, a lot easier to do the latter

The number of people who can judge that fully is extremely small, and it takes a certain bias to buy into it to commit that much effort that you're only going to find ideologues defending it, this is just a math subject that may offer a twisted way to look at physics maybe but selling it as some alternative to quantum gravity is just unbelievable

@RyderRude $S_{EH} + S_{SM}$, done, I did this with commutative standard geometry, I don't need some broken form of geometry to add these actions where the analog of all the assumptions I made to add these actions is hidden in some complicated formalism which I then call a prediction because its such a mess to untangle

ST doesn't derive the SM + EH action, it derives the EH action plus corrections in a context that explains precisely why it is non-renormalizable not only answering this fundamental problem but offering corrections, and even offering a full quantum theory which it slots into in a certain regime, this alone is unbelievable to find by accident

Getting the SM + EH action is useless, anybody can just add these actions

@RyderRude There are a bunch of choices like the form of the Dirac operators and the underlying algebra, I can make a bunch of choices and get the standard model Lagrangian and Einstein-Hilbert action in a few seconds as well

This is actually unbelievable, no news article hyped that up, if I heard something like that 4 years into researching this stuff that it fails for a simple oscillator only to see something this bad then I would feel completely robbed

> "The LQG quantization procedure, applied to the simple harmonic oscillator, produces a different system than the standard quantization procedure. (Although the spectrum is "close.")." (From the comments)

If LQG was serious I would spend years studying it, the problem is that it's not, its so clear whats going on here that people with barely any physics knowledge know to place it into the anti-establishment underdog category based on the framing in some hyped-up news article purposely written to generate that feeling in the anti-authoritarian underdog championing reader

'Oh I'm going to go down route 2 of the 3 valid approaches to quantizing gravity and throw away years on a 'well-defined' theory only to find out the internet lied to me and I wasted years based on news articles misleading me into thinking what I was doing was valid'

> Bergmann and his group, Dirac, Peres, Arnowit Deser and Misner completed the task in the late fifties and early sixties. The formal equations of the quantum theory were then written down by Wheeler and DeWitt in the middle sixties, but turned out to be too ill-defined. A well defined version of the same equations was successfully found only in the late eighties, with loop quantum gravity.

> "The canonical line of research is the attempt to construct a quantum theory in which the Hilbert space carries a representation of the operators corresponding to the full metric, or some functions of the metric, without background metric to be fixed. The program was set by Bergmann and Dirac in the fifties. Unraveling the canonical structure of GR turned out to be laborious.

@RyderRude This kind of splitting assumes that lqg is a valid approach, the other two in this approach are basically lqg propaganda, this is just not taken seriously, lqg does not even have the classical limit sorted out after decades, it doesn't predict the black hole thing it says it predicts it does it after choosing a number (given a fancy name to make it sound serious) that makes things work

The main contender on the internet right now is some garbage 14 dimensional theory that we're still waiting for the inventor to remember how he defined it decades ago

Let's take say the $E_8 \times E_8$ heterotic string, the floor is right open for anybody to try relate this to reality, good luck, one has to understand what this even means in the first place, far easier to just write it off and go down an anti-science path

Again what does this mean, if you know a way to bring string theory back to reality go right ahead, its not as if every single person working on it isn't already trying to do that

I would say the same about any of the 'alternative approaches', if they were serious they would be supported everywhere but they aren't only one subject has enough merit to get that kind of attention that's just the harsh reality, but if people want to work on say LQG sure let them they should be able to even though its considered a waste of time by most people who actually look into it

@DIRAC1930 What does this even mean, this is just anti-science handwaving (I am guessing fueled by certain anti-science youtubers), string theory is so big there are going to be multiple approaches, even stuff I don't personally like deserves to be worked on one obviously has to keep their mind open

A simple starting point that is so rich and so full of ideas people are still only beginning on this '21st century idea that fell into the 20th century', cranks who think science runs on business deadlines demanding deliverables are trying their best to sabotage that and may yet do some serious damage

@RyderRude pick up a string theory textbook and see what it says for yourself, you're talking about a theory that begins by basically just copying special relativity applied to a 1-dim string instead of a 0-dim particle, a simple starting point that leads to an answer to the problem of quantum gravity, but one would have to read a textbook to see that

@DIRAC1930 If someone is going to bash string theory as mathematical games it wouldn't surprise me that they think hep-th is devoid and they're losing interest, quantum gravity is one of the most fundamental questions in physics and only string theory has a serious argument on this front there is no washing that away no matter what some bitter youtubers say, if one is going to ignore the only serious thing then of course what else is there

Even though nearly all the people bashing it haven't bothered sitting down with a textbook

The reason everybody bashes it is because they understand how serious it is

String theory is the most fundamental idea in physics read it and weep

@DIRAC1930 There is almost nothing in cond-mat that is fundamental lol

@User198 kirkmcd.princeton.edu/examples/damped.pdf

ias.edu/video/…

@User198 Are virtual displacements $\delta \mathbf{r}_i$ in the same vector space of solutions $\mathbf{r}(t)$ of the differential equation? The formulation in the wiki frames $A : V \to V$ as having a solution $u \in V$ of $A u = f$ if for all $v \in V$ we have $ A u \cdot v = f \cdot v$, but in d'Alembert we only allow virtual displacements $\delta \mathbf{r}_i$.

@DIRAC1930 'this 4-d world is just an imaginary construct, no students want to work on 3D theory anymore for fear of losing a job, the kids these days and their newfangled Minkowski diagrams are a symbol of the rot in physics'

@Interstellar The core of linear algebra is linearity

@DIRAC1930 Almost everybody who actually looks into it properly understands why string theory is the main focus of hep-th, when the material is too hard or too time consuming its always easier to write it all off as hypothetical games and sci-fi, you haven't a clue where 26 or 10 or 11D even comes from its all just sci-fi we thought up for fun

Have you tried to study this master theory

@DIRAC1930 have you watched this garbage

For every field configuration, in a gauge theory you have the additional problem of gauge transformations on that field configuration on top of things that lead to the infinite volume of the gauge orbit, FP just factors that out and throws it away

FP is for gauge theories, an arbitrary spinor field is not a gauge field

If your action has multiply minima, the action 'spontaneously' picks one of them, if you re-write your action expanded around a specific chosen minima, the original symmetry acts on the action in a more complicated fashion but its still hidden in there somewhere

The action is still gauge invariant, the original gauge symmetry is still there

Do people need to spend years studying LQG just to check whether this is really true instead of trusting papers which assert this, again there are finite resources, the floor is wide open for an upstart to revolutionize physics, it just doesn't happen for some reason...

LQG at times tries to patch on quantization methods that fail when applied to known theories, this is just unbelievable, most people wont take this seriously

There are finite resources, on the one hand we have a theory (string theory) which basically copies every other theory we're familiar with applied to a non-particle starting point, and finds an insanely rich theory which discovered quantum gravity by accident and even parallels how the Fermi interaction was corrected into the standard model, on the other hand we have a bunch of theories that do random different things or ban people from advancing their 'work of entertainment' etc

You would bring back Lysenkoism and Lamarckism with this absurd thinking

Trying to argue this is inherently bad is just so obviously ridiculous its like trying to demonize special relativity, the only question is whether this idea of higher p-brane objects actually applies to the real world, the supposed alternatives don't do anything like this

String theory (in the usual textbook approach) starts by copying special relativity (which is a 0-brane) in the case of a 1-brane and trying to quantize a point particle I mean string to get the Klein-Gordone equation I mean virasoro constraints, then we add bells and whistles on top of this simple model e.g. fermions, ideas about compactification, etc...

People are underhyping the potential for string theory, even if it doesn't apply to the real world the mathematical benefits of it have yet to be discovered, the only question is whether physicists will be too ignorant to keep supporting it and whether it'll take the open-mindedness of mathematicians to push it to its logical conclusion

Most researchers aren't in a position to know all the details of all these supposed alternatives, it doesn't take long looking at them for most people to see why its a waste of time to focus on these, the floor is wide open for a genius Einstein to prove everyone wrong, there is a reason why when people looked into string theory properly it ended up being the dominant hep-th research program