LHC found no supersymmetry any alternatives to string theory

[kodama]

TL;DR

time to move on from string theory

in the 19th and 20th century physicists were looking for the luminous aether and the Michelson Morley experiment found no evidence for aether

ultimately it was Einstein and his special relativity that got rid of the luminous aether

in the 21st century physicists were looking for evidence of supersymmetry and extra dimensions and the Large Hadron Collider found no evidence of supersymmetry

string theory requires supersymmetry but the LHC found no evidence for it.

are there any alternatives to quantum gravity and theory of everything that are worth researching, with the assumption that supersymmetry and extra dimensions do not exist?


are there alternatives to theoretical physics besides string theory that should be taken seriously?

can you get a theory of quantum gravity and theory of everything in 4 dimensions and without supersymmetry, since the LHC found no evidence for either of them?

 

[javisot]

TL;DR: time to move on from string theory

in the 19th and 20th century physicists were looking for the luminous aether and the Michelson Morley experiment found no evidence for aether

ultimately it was Einstein and his special relativity that got rid of the luminous aether

in the 21th century physicists were looking for evidence of supersymmetry and extra dimensions and the Large Hadron Collider found no evidence of supersymmetry

string theory requires supersymmetry but the LHC found no evidence for it.

are there any alternatives to quantum gravity and theory of everything that are worth researching, with the assumption that supersymmetry and extra dimensions do not exist?


are there alternatives to theoretical physics besides string theory that should be taken seriously?

can you get a theory of quantum gravity and theory of everything in 4 dimensions and without supersymmetry, since the LHC found no evidence for either of them?

Suffice it to say that supersymmetry would be found in a different range than expected (we’ve bought ourselves some time).

The theory being tested and wich governs what happens at the LHC is QFT, no ST. The idea of "asymptotic safety" in QFT remains a possibility.

 

[bhobba]

are there any alternatives to quantum gravity and theory of everything that are worth researching, with the assumption that supersymmetry and extra dimensions do not exist?

can you get a theory of quantum gravity and theory of everything in 4 dimensions and without supersymmetry, since the LHC found no evidence for either of them?

Yes - Loop Quantum Gravity.

Also check out:
https://websites.umass.edu/donoghue/research/quantum-gravity-and-effective-field-theory/

We do have a quantum theory of gravity valid to about the Planck scale. In fact, it is now thought that all our theories are only effective field theories valid to about the Planck scale. That is way beyond the LHC or any future envisioned collider.

Hopefully, some finding from somewhere will let us peek beyond the Planck scale.

Thanks
Bill

 

[javisot]

Yes - Loop Quantum Gravity.

Sabine Hossenfelder: Backreaction https://share.google/hk4zvNxU6UEZfs6r7

From wikipedia, https://en.wikipedia.org/wiki/Loop_quantum_gravity, "Gravitons, string theory, supersymmetry, extra dimensions in LQG":

"Since LQG has been formulated in 4 dimensions (with and without supersymmetry), and M-theory requires supersymmetry and 11 dimensions, a direct comparison between the two has not been possible. It is possible to extend mainstream LQG formalism to higher-dimensional supergravity, general relativity with supersymmetry and Kaluza–Klein extra dimensions should experimental evidence establish their existence. It would therefore be desirable to have higher-dimensional Supergravity loop quantizations at one's disposal in order to compare these approaches. A series of papers have been published attempting this.[69][70][71][72][73][74][75][76] Most recently, Thiemann (and alumni) have made progress toward calculating black hole entropy for supergravity in higher dimensions. It will be useful to compare these results to the corresponding super string calculations.[77][78]"

 

[kodama]

I know about loop quantum gravity, but string theorists say it has no credibility whatsoever.

in light of the LHC not finding supersymmetry or extra dimensions, does that elevate loop quantum gravity over string theory? should there be less research into string theory and more research into loop quantum gravity?

 

[PeterDonis]

I know about loop quantum gravity, but string theorists say it has no credibility whatsoever.

These would be the same string theorists that were sure the LHC would find evidence of supersymmetry.

in light of the LHC not finding supersymmetry or extra dimensions, does that elevate loop quantum gravity over string theory?

AFAIK loop quantum gravity hasn't made any testable predictions, so I don't know that the failure of one claimed prediction of string theory "elevates" loop quantum gravity. We simply have no evidence to go on for any guidance as to what kind of quantum gravity theory we should be pursuing.

should there be less research into string theory and more research into loop quantum gravity?

That would be up to whoever is funding the research. As far as I can tell the LHC's failure to find any evidence of supersymmetry hasn't affected the allocation of grant funding in physics very much.

 

[ohwilleke]

That would be up to whoever is funding the research. As far as I can tell the LHC's failure to find any evidence of supersymmetry hasn't affected the allocation of grant funding in physics very much.

Theoretical physics (which is most of what supersymmetry is at this point from a funding perspective) is cheap. A theoretical physicist needs one mid-level professional salary, a laptop, a few journal subscriptions, some access time to a supercomputer, one or two research assistants, a white board, and the physicist's office's share of the building upkeep (the institution usually owns the office building itself, free and clear).

Some of the professorships are endowed, so they don't require annual grant writing to fund.

Much cheaper than experimental HEP physics and with much greater inertia since professors are usually tenured after a few years, creating a permanent right to annually funding, and because higher education institutions tend to be stable or shrinking in study bodies, not growing, so there aren't many new, unspoken for positions. SUSY and String Theory hit a sweet spot in academia demographics and are now locked in, even if, in hindsight, those appointments and funding decisions look ill-advised.

The for profit private sector isn't going to invest in this because new developments in astrophysics or fundamental physics have no economic return on investment in the time frame that private investors operate in.

 

[kodama]

These would be the same string theorists that were sure the LHC would find evidence of supersymmetry.


AFAIK loop quantum gravity hasn't made any testable predictions, so I don't know that the failure of one claimed prediction of string theory "elevates" loop quantum gravity. We simply have no evidence to go on for any guidance as to what kind of quantum gravity theory we should be pursuing.


That would be up to whoever is funding the research. As far as I can tell the LHC's failure to find any evidence of supersymmetry hasn't affected the allocation of grant funding in physics very much.

since the LHC failure to find any evidence of supersymmetry, should that have affected the allocation of grant funding in physics, specifically, either reduce string theory funding or increase loop quantum gravity funding until they reach parity?

 

[kodama]

Theoretical physics (which is most of what supersymmetry is at this point from a funding perspective) is cheap. A theoretical physicist needs one mid-level professional salary, a laptop, a few journal subscriptions, some access time to a supercomputer, one or two research assistants, a white board, and the physicist's office's share of the building upkeep (the institution usually owns the office building itself, free and clear).

Some of the professorships are endowed, so they don't require annual grant writing to fund.

Much cheaper than experimental HEP physics and with much greater inertia since professors are usually tenured after a few years, creating a permanent right to annually funding, and because higher education institutions tend to be stable or shrinking in study bodies, not growing, so there aren't many new, unspoken for positions. SUSY and String Theory hit a sweet spot in academia demographics and are now locked in, even if, in hindsight, those appointments and funding decisions look ill-advised.

The for profit private sector isn't going to invest in this because new developments in astrophysics or fundamental physics have no economic return on investment in the time frame that private investors operate in.

you say its cheap, if its so cheap, why isn't there parity between string theorists and loop quantum gravity theorists?

google how much has been spent on string theory and how much was spent on loop quantum gravity

is it time for parity between the two approaches?

 

[PeterDonis]

since the LHC failure to find any evidence of supersymmetry, should that have affected the allocation of grant funding in physics, specifically, either reduce string theory funding or increase loop quantum gravity funding until they reach parity?

That's not something we can usefully discuss here.

 

[ohwilleke]

you say its cheap, if its so cheap, why isn't there parity between string theorists and loop quantum gravity theorists?

google how much has been spent on string theory and how much was spent on loop quantum gravity

is it time for parity between the two approaches?

Open AI spent $10M to solve a Millenium Prize related to the Navier-Stokes equation. Find someone willing to pony up that much money every year and you could probably double the number of LQG researchers.

There are people who do help professors look for money to fund their research stuff for a living.

For example, my late mother was a university administrator whose job was to help professors find funding their work from grants. Pretty much every university in the world has at least several administrators who have similar missions. That's a corps of maybe ten thousand people in the U.S. alone.

All it really takes is a couple of ambitious profs who are willing to put down their slide rules and dirty their hand to do fundraising by working with the right kind of administrators to get it, and a few university administrators in charge of helping them find grants, and it can happen.

 

[berkeman]

Thread is closed for Moderation.

 

[berkeman]

you say its cheap, if its so cheap, why isn't there parity between string theorists and loop quantum gravity theorists?

google how much has been spent on string theory and how much was spent on loop quantum gravity

is it time for parity between the two approaches?

This thread has stumbled into political funding territory, so is now closed.