Quantum Gravity Infinities Loops and Strings Vsevolod Ivanov

Quantum Gravity: Infinities, Loops, and Strings Vsevolod Ivanov 2014 • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Introduction • Gravitation and three other fundamental forces have non-compatible formalism • Each breaks down outside its domain • Quantized theory of gravity is desired • Secondary goal: “theory of everything”

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Quick Review of Feynman Diagrams

QED in d Dimensions

Field Theory for Gravity

Mass Dimension of the Coupling Constant

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

SUper GRAvity

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

SUper GRAvity

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Loop Quantum Gravity

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Experimental Tests of Quantum Gravity • Quantum gravitational effects are too weak to test! • Recent proposals: • QG effects in gamma ray bursts • Violation of Lorentz invariance • Polarization of the CMB

CMB Polarization • Temperature creates quadrupole anisotropy • Other effects: • Density fluctuations (scalar) • Vorticity from defects (vector), damped out by inflation • Gravitational waves (tensor) • Two Polarization Types: Curl-free E-mode and Grad-free B-mode

BICEP 2 Measures B-mode Polarization!

Quantum Gravity: Infinities, Loops, and Strings • What is THE question (and why do we care)? • A quantum history • The trouble with gravity • SUGRA, almost sugar but not as sweet • A tale of two revolutions • Loopy nets • Experimentalists flex their muscles • The future?

Future Experimental Tests • Lorentz invariance violation: future experiments will have better precision for higher order terms • Planck probe will measure anisotropies to higher precision • GW-superconductor interactions?

References “Quantum Gravity Notes” M. Spiropilu (2004) "Cosmic Microwave Background Polarization: The Next Key Toward the Origin of the Universe", Y. D. Takahashi "Angular momentum: an approach to combinatorial space-time", R. Penrose "Introduction to Loop Quantum Gravity", Simone Mercuri "Quantum gravity: an introduction to some recent results", Enrique Alvarez "Detection of B-Mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope", D. Hanson et al. , PRL 111, 141301 (2013) "Experimental Search for Quantum Gravity", Sabine Hossenfelder An Introduction to Modern Astrophysics, B. W. Carroll, D. A. Ostlie (1996) Images: http: //astrophysics. pro/wp-content/uploads/2013/03/Quantum-Gravity. jpg http: //upload. wikimedia. org/wikipedia/commons/d/d 2/Spinnetwork. jpg Questions?