Online seminar arranged for the general audience comprising of the researchers, PhDs, graduates, undergraduates, and high school students who desperately wanted to know the essence of string theory and its phenomenology in layman term. This was primarily for the students who either are in their sophomore/junior year or have not taken advanced physics or maths courses; therefore, I decided to keep my presentation as simple as possible and did not include much mathematics in it. [Link to the PDF]
Summary of the talk:
- Three forces are combined. Gravity is not.
- QFT is discrete. Gravity is continuous.
- QFT + Gravity is not successful.
- Loop Quantum Gravity, Causal Set Theory, and String Theory.
- Basic building blocks are not particles but little strings of energy.
- Different resonant frequencies correspond to different particles.
- Dimensions of strings are close to Planck length.
- Open strings are gauge particles (SM). Closed strings are gravitons.
- There are five string theories. All five need 10 space-time dimensions. All five make an M theory in 11 dimensions. All five are consistent with supersymmetry.
- Open strings attach to hypothetical surfaces called D-branes. Closed strings do not attach to those.
- There are fields associated with D brands.
- There are some dualities in string theory like T-Duality, AdS/CFT duality, etc.
- AdS space gives gravity of GR (naively speaking).
- CFT is a scale transformation of fields.
- AdS/CFT correspondence is an emergence of Holography.
- A 5D brane is embedded in 6D spacetime.
- String theory may not be tested directly in experiments but it has the claim for the only candidate of quantum gravity. It also resolves many fundamental questions of the universe.