General philosophy --
The Advanced Physics Requirement is really a breadth requirement; it's purpose is to make sure students graduating from Caltech leave with a fairly broad knowledge of physics.  At the same time, students can choose what courses they take to satisfy this requirement, following their personal interests.

Course Substitutions for the Advanced Physics Requirement
--What counts for what...

The Advanced Physics categories:
Students need to take a minimum of a one-quarter course in six of the following eight categories:

• Elementary Particle Physics (EP)
• Nuclear Physics (NP)
• Atomic/Molecular/Optical Physics (AMO)
• Condensed Matter Physics (CMP)
• Gravitational Physics (GR)
• Astrophysics (AP)
• Mathematical Physics (MP)
• Interdisciplinary Physics (ID)

• Ph101/Order-of-magnitude -- counts for ID or AP
• Ph102b/Physics of the Interstellar Medium -- counts for counts for AMO, AP or ID
• Ph103/Neuroscience -- counts for ID
• Ph103/Electrons in Nanostructures -- counts for CMP
• Ph103b/Spectroscopy -- counts for AMO, AP or ID
• Ph105 -- counts for ID
• Ph118 -- any term counts for ID
• Ph127 -- two terms counts for CMP or ID
• Ph129 -- any term counts for MP
• Ph130 -- any term counts for CMP
• Ph135 -- individual terms count for AMO, CMP, NP, or EP, depending on content
• Ph135b/String Theory -- individual terms count for MP or EP
• Ph136a (Stat Mech, Optics) -- counts for AMO or ID
• Ph136b (Elasticity, Fluid Dynamics) -- counts for AP or ID
• Ph136c (Plasma, GR) -- counts for GR
• Ph161 -- any term counts for MP or ID
• All physics courses numbering 200 count for something, depending on content
• Ph205abc -- Ph205a counts for ID, or Ph205ab counts for Math; Ph205c counts for EP
• Ph219abc -- Ph219a counts for AMO, ID or MP; or Ph219abc counts for any two of those
• Ph236abc -- Ph236a counts for Gravitational; Ph236bc counts for Astrophysics
• Ay121 -- counts for AP or AMO
• APh114 -- any term counts for CMP

All you have to do for this requirement is take six quarters of reasonably advanced courses.  The list of substitutions above is a guide, but you should feel free to be creative in picking courses -- astronomy, chemistry, and applied physics courses are acceptable, for example.  Pick courses you're interested in!   And yes, courses taken pass/fail satisfy the requirement.

After you have decided what looks interesting, make a list of the courses you will take (or have taken), and how they satisfy the requirement (i.e. which categories). Send your list to Frank Porter for official department approval. Note that your course list must be approved, and the courses must be passed, before you will be allowed to take the Oral Candidacy Exam.

It is possible to take exams for one or more of the Advanced Physics categories, if you have already taken a lot of advanced courses elsewhere.  This route is discouraged, however, so expect the exams to be difficult.  Better if you find some other interesting courses to take, that don't overlap with what you have taken before.