| <Previous | January | February | March | April | May | Next> |
Lecture 25: Cosmology
May 1, 2025
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; Supp CH 12: 4, 7, 8
Note: this is only the second half of the hand-in set.
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.
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
- Werewolves of London - Warren Zevon
- Heart of Gold - Neil Young
- Big Yellow Taxi - Joni Mitchell
- I'll Take You There - The Staple Singers
Assigned Problems Guide
- A85: quick and fun and games with balloons.
- Supp 12-1: medium. Plug in the time from the table into the collision energy expression, and then look for particles with that mass (rest energy).
- Supp 12-2: medium-quick. Like problem 1 but the other way around. Take the rest energy of a lambda and anti-lambda pair, and solve for the time after the Big Bang when that energy was available.
- Supp 12-5: medium. Go back to that part of the reading and try to follow the description of each epoch. Sometimes it helps to read the epoch before as well.
- Supp 12-6: medium. Find in the text where it gives the time of quark confinement. Find the corresponding collision energy and look up the appropriate hadron. We're look at just the power of 10, not more specific than that.
- Supp 12-9: medium-long. Start with 3000 $X$'s. From the diagram, how many decay into $q+q$, and how many decay into $\bar q + \bar\ell$. Do the same with the 3000 $\bar X$'s. Now add up all the $q$, all the $\bar q$, etc. Even though you started with an equal number of $X$ and $\bar X$, you should end up with an unequal number of $q$ and $\bar q$.