1. Particle Physics
PHY 361

2. Standard Model of Particles
SPACE
TIME
Strong Interaction
E&M Interaction
lepton
baryon
meson
Weak Interaction
Hadronic Interaction
(residual nuclear force)

3. Standard Model of Automobiles
Annihilation
Higgs?
Degenerate Fermi Gas or a Bose Einstein Condensate?
Particle Decay

4. Symmetries Continuous Symmetries
space-time translation
rotational invariance
Lorentz boosts
guage invariance
Noether’s Theorem continuous symmetries correspond to conserved quantities
energy-momentum
angular momentum
center-of-momentum
electric charge
Discrete Symmetries
particle exchange
parity P : x  -x
time T : t  -t
charge C : q  -q
Discrete Theorems
spin-statistics theorem
CPT theorem

5. Be careful, some idiot’s
Auto – Symmetries
U-turn Operator
CP (charge, parity)
Reverse Operator
T (time) R
Chunnel Operator
P (parity)
100
km/h
km/h
99.7
A little more seriously, let me talk about some discrete symmetries like parity in the context of cars.
Imagine two countries separated by water where cars drive on the opposite sides of the road.
So in one country we have left-sided cars, and in the other, right-sided cars.
Now if I drive through this tunnel, I change from a right-handed car to a left-handed car.
As a conscious law-abiding citizen, I ask myself: are the laws the same now?
For the strong force, electromagnetism, and gravity, I get the reassuring answer: yes.
But for the weak force, I get a complete shock: Right-handed cars are absolutely illegal.
The same goes for left-handed anti-cars.
We see that charge conjugation, going from a car to an anti-car in the same lane is also forbidden,
because then we could convert back to a right-handed car.
So neither charge conjugation nor parity have a symmetry are preserved by the law.
In the car world this makes sense and saves a lot of headaches
(and neck pain), but in the particle world, it makes us ask
uncomfortable questions, like why like this country and not that?
Is some other symmetry preserved? Maybe: I can go from a left-handed car to a right-handed anti-car.
It turns out that this symmetry is very closely respected, but not exactly.
Is all lost? There is one other symmetry: Time, which is represented as driving backwards.
But now you say: isn’t an anti-car just a negative energy car driving backwards in time? Why yes!
As far as I can tell, that is the jest of the CPT theorem, which is closely related to the Pauli exclusion principle.
With all these deep and natural symmetries, it’s no wonder that this poor driver was overcome with charge-confusion.
Now a disclaimer: Physics students, do not use this model to answer questions on your tests. L R
I’m coming
home …
Be careful, some idiot’s
going the wrong way
on the freeway.
Only one? They’re
all over the place!
CPT theorem: ALL laws are invariant under CPT