513 reputation
212
bio website arsphysica.wordpress.com
location Sao Paulo, Brazil
age 32
visits member for 4 years, 1 month
seen Nov 20 at 19:52
Physicist, interested in agent-based simulation and statistical physics of models inspired by economic and biological reasoning. Programming in C and Python.

Apr
25
comment Modern and complete references for the $k\cdot p$ method?
Hum... Rereading this now: I forgot to point out where the Kane becomes an approximation. That's when you choose a finite number of basis functions to expand your hamiltonian. You could, in principle, obtain an exact (and infinite dimensional) Kane operator, but this would hardly be practical.
Apr
5
comment What does it mean to say “Gravity is the weakest of the forces”?
@BenCrowell When I first read the question, I assumed the person asking had no knowledge of physics beyond high school physics and I tried to adapt my answer to that context. Feel free to edit my question to add more detail if you want.
Feb
4
comment Can a single classical particle have any entropy?
@sb1 Thanks :). You know, I have the exact opposite feeling. I think information theory have a more fundamental status. In essence information theory is about general rules for how we acquire quantitative knowledge about things. And... physics is a specific stance of this problem. :)
Feb
3
comment Can a single classical particle have any entropy?
@Tim unless I have an uncertainty about its initial position of the particle, or an uncertainty about the position of some other particle that will interact with it... or any other uncertainty about anything that will influence the motion of the particle. Using probability distributions have nothing to do with non-determinist equations of motion. After all, quantum equations of motion are all deterministic!
Feb
3
comment Can a single classical particle have any entropy?
thanks :) . I don't understand why would I need many bodies though. That entropy is the legimate entropy of a single particle, and I can do with it anything I can do with any other entropy.
Feb
2
comment Conserved quantities in generalized n-body problem
Seems like homework. Is this homework?
Jan
31
comment What does it mean to say “Gravity is the weakest of the forces”?
I stand corrected then! :)
Jan
31
comment Modern and complete references for the $k\cdot p$ method?
I liked this question. Made me re-read some parts of my masters dissertation. :P
Jan
31
comment Modern and complete references for the $k\cdot p$ method?
I don't have priviledge to edit the tags, but the tags should include semiconductor-physics and group-theory at least.
Jan
26
comment What experiment would disprove string theory?
If this is right, isn't this the same as saying that we have a family of models (one for each vacuum) that is so incredibly general that any reasonable model (one that satisfy the right set of physical constraints) must very likely belong to this family and that we now must fit a parameter (choose the vacuum - can they be labeled by a discrete or continuous set of parameters?)?
Jan
26
comment What experiment would disprove string theory?
@Lubos Please correct me if I misunderstood completely your answer. You are stating that string theory is logically and mathematically sound, and that there's a good chance that it covers all alternative physically sane models one could come up with (Lorentz invariant, compatible with QFT at low energies, etc...), and that what's left for us is determining what is the right vacuum to fit the theory to our observable reality. Is this a correct?