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Lecture 25: Cosmology
April 30, 2026
Reading Assignment
- Read: Supplementary Reading Ch 12
Objectives
- (Continuing objective) Describe quantum and elementary particle theories in your own words, and discuss applications of the material.
- Describe qualitatively the epochs of the Big Bang standard model of cosmology.
- Calculate the energy, temperature, and time of critical events in the early universe (symmetry breaking, particle decoupling, etc.), given particle data tables. Relate the times/energies/temperatures to the types of particles that abundant during the different epochs.
- Describe three observational evidences that serve as tests of the Big Bang model and modern particle physics.
Homework
- Friday's Assigned Problems:
A85; Supp CH 12: 1, 2, 5, 6, 9
- Monday's Hand-In Problems:
X15 (below); Supp CH 12: 4, 7, 8
Problem X15 The Higgs boson is the messenger particle for the Higgs interaction. Recently, the mass of the Higgs boson was measured to be $125\,\text{GeV/$c^2$}$. In the early universe, real Higgs bosons could be produced in random collisions. Determine the latest time after the Big Bang that Higgs bosons could be easily made from collisions.
Note: this is only the second half of the hand-in set.
Lecture Materials
- Click here for the Lecture overheads. Answers: CT1 - 1; CT2 - 6
Videos of example problems
To see the problem statement, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement.- Video example: Time after Big Bang for end of electro-weak symmetry.
Pre-Class Entertainment
- Do Right Woman, Do Right Man - Aretha Franklin
- Fidelity - Regina Spektor
- Werewolves of London - Warren Zevon
- Big Yellow Taxi - Joni Mitchell
- Heart of Gold - Neil Young