Fundamental Physics: Gamma-Ray Absorption and Axion-Like Particles - Class 1

Explore fundamental physics concepts in this comprehensive lecture from the Latin-American School on CTA Science. Delve into topics such as pair production thresholds, cross-sections, background radiation fields, and extragalactic background light (EBL) measurements. Examine the role of stars in EBL composition, various EBL models, and optical depth. Learn how gamma-ray observations can constrain EBL and discover direct modeling techniques for EBL ingredients. Investigate parity transformation, charge-parity, and the strong CP problem. Gain insights into axions and axion-like particles (ALPs), their evolution in an expanding universe, and the axion/ALP parameter space. Enhance your understanding of fundamental physics principles and their applications in astrophysics and cosmology.

Intro
AIM OF MY LECTURES: UNDERSTAND THIS PLOT
OUTLINE LECTURE 1
THRESHOLD FOR PAIR PRODUCTION
CROSS SECTION FOR PAIR PRODUCTION
BACKGROUND RADIATION FIELDS
EBL MEASUREMENTS
INGREDIENTS TO THE EBL: STARS
ADDITIONAL CONTRIBUTIONS?
EBL MODELS
OPTICAL DEPTH
CONSTRAINING THE EBL WITH GAMMA-RAY OBSERVATIONS
MODEL THE EBL INGREDIENTS DIRECTLY
CONCLUSIONS y-RAY ABSORPTION
PARITY TRANSFORMATION
CHARGE-PARITY
AXION SOLVES THE STRONG CP PROBLEM
AXIONLIKE PARTICLES (ALPs)
EVOLUTION OF AXION/ALP FIELD IN AN EXPANDING UNIVERSE
THE AXION / ALP PARAMETER SPACE