String Theory and Our Universe by Cumrun Vafa

[@annaclarafenyo8185]

The black hole argument for the charge completeness condition can be violated by conspiracy, for example, particles of charges 2,4,8,16,32,64,128,256 and 77. A charge-1 state required "exists" but only as a parallel comoving combination of particles and anti-particles, and you can combine the charges to make any integer. The argument requires a more careful formulation to avoid these ridiculous conspiracies (I agree they do not occur).

[@msg72freenetde]

if i put two identical strings on top of each other - so each point of string A meets each point of string B - what is the distance between these 2 strings? zero?! so r^-2 is infinity again? seems there is no gain at all...

[@gilleslalancette7933]

excellent presentation from mister Vafa. I love it, it is clear, concise and full of great links into various physics. Thanks for presenting this.

[@msg72freenetde]

Why string-theory decided to declare particles as vibrating stuff? why not declare the space and time as vibrating?

[@marcelodossantos2493]

Initially, physicists just wanted to reproduce some results obtained in the realm of Quantum Chromodynamics. They thought thay maybe hadrons (which are composed of quarks connected by flux tubes) could be described by strings. This happened in the 70s, and led to initial efforts in string theory. Then we found out during the following decades that this theory of vibrating strings actually describes a lot of unexpected stuff - in particular, it describes vibrating spacetime.

[@thedouglasw.lippchannel5546]

Howdy

[@DavidBrown-om8cv]

" As long as there is no gravity in the game, we know how everything works." Without gravity, there would no planet Earth & no human life. Consider 2 hypotheses: (1) String theory (in some form) is the only mathematically plausible way to unify quantum field theory & general relativity theory. (2) The main problem with string theory is that the string theorists refuse to carefully study the many empirical successes of Milgrom's MOND. Is hypothesis (2) wrong? Please google "pavel kroupa green schwarz".

[@brendawilliams8062]

Thankyou

[@annaclarafenyo8185]

MOND is next to impossible in any reasonable theory like string theory, because it involves unmotivated modification to gravity which wrecks the way gravity works as a spin-2 particle. This requires a ton of new light long-range force-fields, which you can introduce, but it makes a mess, and there's no way this is correct, because dark matter explains all the observations much much better, and dark-matter naturally falls out of any string theory.

[@brendawilliams8062]

@@annaclarafenyo8185 that is especially informative. Thankyou