Unification: Geometry, Gauge Theory & Quantum Gravity
The quest for a unified theory of all fundamental forces — from string theory and M-theory through loop quantum gravity to the geometric connections between Perelman's Ricci flow, BMS symmetries, and the Standard Model.
This course explores the major approaches to quantum gravity and unification, with full mathematical derivations. Part I covers string theory from the bosonic string to superstring dualities. Part II develops M-theory, D-branes, and the AdS/CFT correspondence. Part III surveys alternative approaches: loop quantum gravity, spin foams, causal sets, asymptotic safety, and emergent gravity. Part IV connects everything through the geometric framework developed in the GR course — Perelman's Ricci flow, the spin memory effect, Lagrangian connections, and the extended master Lagrangian.
Part I: String Theory
From point particles to strings: the bosonic string, superstring types, compactification on Calabi-Yau manifolds, and the web of dualities.
Why Strings?
Graviton from closed strings, UV finiteness, the string length
02The Bosonic String
Nambu-Goto & Polyakov actions, quantization, D=26
03Superstring Types
Type I, IIA, IIB, Heterotic SO(32) & E8×E8
04Compactification
Kaluza-Klein, Calabi-Yau, flux compactifications
05T-Duality & S-Duality
Strong-weak duality, winding modes, mirror symmetry
Part II: M-Theory & Holography
The 11-dimensional mother theory, branes as fundamental objects, and the revolutionary AdS/CFT duality.
M-Theory & 11 Dimensions
Supergravity limit, M2 & M5 branes, duality web
07D-Branes & p-Branes
Open strings on branes, DBI action, gauge theory on branes
08AdS/CFT Correspondence
Maldacena conjecture, bulk-boundary dictionary, examples
09Holographic Principle
Bekenstein bound, covariant entropy bound, ER=EPR
10BH Information Paradox
Hawking radiation, Page curve, islands formula
Part III: Quantum Gravity Approaches
Alternative routes to quantum gravity: canonical quantization, discrete spacetime, and emergent phenomena.
Loop Quantum Gravity
Ashtekar variables, spin networks, area/volume spectra
12Spin Foams
State sum models, Barrett-Crane, EPRL-FK model
13Causal Set Theory
Discrete partial orders, Hauptvermutung, dynamics
14Asymptotic Safety
Weinberg conjecture, functional RG, UV fixed point
15Emergent & Entropic Gravity
Verlinde, Jacobson, thermodynamic spacetime
Part IV: Geometric Unification
The deep geometric skeleton connecting Ricci flow, BMS symmetries, gauge theory, and the master Lagrangian.
Perelman & Ricci Flow
Entropy, surgery, geometrization ↔ gravitational physics
17Spin Memory & BMS
Infrared triangle, soft theorems, celestial CFT
18Lagrangian Connections
EH, GHY, ADM, Bondi-Sachs, Mabuchi — one structure
19SM as Gauge Geometry
Yang-Mills curvature, instantons, Atiyah-Singer
20The Extended Master Lagrangian
All forces + gravity + Perelman unified
Prerequisites
Featured: The Forgotten Geometry
The Forgotten Geometry: A New Path to Unification
A geometric perspective on the quest for a unified theory of all forces.