Prof. Claudia de Rahm's theory of 'Massive Gravity' to explain Dark Energy is getting a lot of press as of late. So let's dig into it. (thread: 1/n)https://www.theguardian.com/science/2020/jan/25/has-physicists-gravity-theory-solved-impossible-dark-energy-riddle …
-
Show this thread
-
Before getting to gravity, recall that forces are transmitted by a 'mediator' which are always bosons EM: the photon, strong force: gluon, weak force: W± & Z. When the symmetry corresponding to the force carrier is unbroken the force carriers are massless (m=0). (2/n)pic.twitter.com/7Y38aPPQOa
5 replies 11 retweets 105 likesShow this thread -
What about Gravity? The symmetry corresponding to gravity is the most respected symmetry in all physics & goes by many names It's the one underlying Einstein's General Theory of Relativity: General Covariance/Gauge-Lorentz Symmetry/ Diffeomorphism Invariance (3/n)pic.twitter.com/Y5DyRN2qMg
6 replies 11 retweets 64 likesShow this thread -
Because this symmetry (General Covariance) has never been observed to be violated, physicists were convinced that the gauge field corresponding to gravity corresponded to an exact, unbroken symmetry I would then immediately follow, then, that the graviton is massless
2 replies 8 retweets 40 likesShow this thread -
But wait!, says de Rahm.. Perhaps Lorentz symmetry could just be an *approximate* symmetry of nature This would happen if the graviton (hμν) has a mass--mass terms for gauge fields always break gauge invariance But!.. look at the first tweet.. (5/n)pic.twitter.com/cgEyMtE73l
1 reply 7 retweets 49 likesShow this thread -
Boom! We see that the graviton (metric; hμν) contains the exponential potential we expected! TL;DR: If the graviton has a mass~hubble rate (H), then large scale gravity can act repulsive and reproduce the Dark Energy observations, with no Dark Energy at all! (n/n)pic.twitter.com/bN8NKU4jAp
12 replies 13 retweets 122 likesShow this thread -
I’m actually rather proud of this mini explanation of gauge gravity
10 replies 2 retweets 101 likesShow this thread -
Replying to @InertialObservr
Amazing thread! Is this the breaking of GL(4,R) -> SO(1,3)? Or is this like complete symmetry breaking, with no massless bosons remaining?
1 reply 0 retweets 0 likes -
This Tweet is unavailable.
-
Replying to @LambdaQG @PotatoAsad
It’s what’s called “explicit symmetry breaking” or “weak symmetry breaking”
3 replies 0 retweets 0 likes
Sorry I meant to say “soft” SB not ‘weak’
-
-
Replying to @InertialObservr @LambdaQG
So THAT'S what soft SB is. Heard the term, never got what it meant. Now I have an example. Thanks!
1 reply 0 retweets 2 likes -
Replying to @PotatoAsad @LambdaQG
It’s far less complicated than this.. it’s just when you have a term that explicitly violates a symmetry, which is also small
0 replies 0 retweets 4 likes
End of conversation
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.