892 reputation
115
bio website joshphysics.com
location Los Angeles
age 28
visits member for 1 year, 11 months
seen 2 days ago

New project: phermi.com

Let me know if you know of any hard physics problems with clever solutions. (email listed to the left)

Personal website: joshphysics.com

Currently a lecturer at the UCLA Department of Physics and Astronomy.

Ph.D. theoretical high energy physics, UCLA.

BA/BS in physics/math, UC Berkeley.


Nov
19
comment Pure Point Spectrum implies Spanning Eigenfunctions
I think this would more appropriately be asked on math.SE.
Nov
2
comment Gradient of a function with base vectors
Isn't this more appropriate for math.SE?
Oct
19
comment What is the dimension of the vector space of functions $f:\mathbb R\to\mathbb R$?
Wonderful! Thanks Asaf.
Oct
19
comment What is the dimension of the vector space of functions $f:\mathbb R\to\mathbb R$?
Wow ok $2^{2^{\aleph_0}}$ it is then. Pretty monstrous (to a non-set-theory aficionado at least). That's a very nice last equation you wrote. Does it have a special name? Where in standard books would I find such wonderful gems?
Sep
27
comment How are eigenvectors/eigenvalues and differential equations connected?
Great answer btw. Would you happen to know of any good references that treat ODEs heavily using linear-algebraic language as in this answer? In particular, a text which discusses Jordan normal form in this context as you allude to would be useful. I'll be teaching a math methods for physics class, and I'd find such a reference very useful.
Sep
23
comment How are eigenvectors/eigenvalues and differential equations connected?
Shouldn't $e^{\lambda y}$ read something like $e^{\lambda t}$ instead?
Sep
4
comment How to calculate this functional derivative?
@Trimok Thanks; edited.
Aug
3
comment What is the probability of being in a “run” of length $k$?
Thanks. This agrees with the expression I wrote it seems since $\sum_j j 2^{-j} = 2$.
Jun
28
comment Special conformal killing fields - solving for integral curves.
@HansLundmark Very slick; thanks.
Jun
28
comment Special conformal killing fields - solving for integral curves.
@Kirill I found where I went wrong; I hadn't originally simply directly computed $\dot y$, so I had obtained the identity $y\cdot(\dot y + b)$ which is of course still true but not what we want. I hope you don't mind if I post my own answer as well and perhaps accept it since it's a bit simpler? Thanks so much for your help!
Jun
28
comment Special conformal killing fields - solving for integral curves.
@Kirill I probably made an error, let me check my algebra.
Jun
28
comment Special conformal killing fields - solving for integral curves.
@Kirill Agreed, but how does one solve the equation at the end for $x$?
Jun
28
comment Special conformal killing fields - solving for integral curves.
Wow, bravo for all this effort. The crazy thing is that I saw this exactly at the same time that I think I've almost figured out a really tricky way to do this. See my edit to the question (the Progress! section) I'll read through this as well. Thanks again.
Jun
4
comment Big O notation for complex-valued functions of a real variable
@TedShifrin Thank you.
Mar
28
comment What extra assumption makes this transformation affine?
@Rahul Ok thanks for the insight.
Mar
28
comment What extra assumption makes this transformation affine?
@Rahul Ah thanks! Does one need to restrict the field over which $V$ is defined?
Mar
28
comment What extra assumption makes this transformation affine?
@BISHD Great! One might think that such curiosity would warrant an upvote ;) ? Thanks for the edits btw.
Mar
28
comment What extra assumption makes this transformation affine?
@BISHD lol ok. I had hoped what I was asking was clear from the context, but I agree it's not entirely clear, so I changed the wording to "how weak one can make additional assumptions." How's that?
Mar
28
comment What extra assumption makes this transformation affine?
@BISHD Yes I understand that. I am not assuming that $f$ is linear.
Mar
28
comment What extra assumption makes this transformation affine?
@BISHD Just a map.