Recent content by John_Phillips

No, you don't. Any programming requires you to think algorithmically, and that is a skill mathematicians tend to have, but you don't have to be a mathematician to program. John

Is the directory that holds the nr3.h header in your include paths? That is the typical cause of this error. John

I think I know what you mean, but I think asking for it shows a misunderstanding. Screen coordinates are a rectilinear 2 dimensional system, so they are already Cartesian. They just happen to be a Cartesian system with the origin at the upper left corner and the positive y-axis pointing down the...

A quick fix because I was typing at 2AM my time for my last post. The Higgs mechanism isn't a seesaw. Sorry for saying it that way. John

mysearch, If you would like to see the details, including all three of the different expansion rate epochs and calculations of what the rate is in the different epochs (matter dominated, radiation dominated, and vacuum dominated) I would suggest a recent cosmology text. My current personal...

There are questions about whether the CP violation rate is a constant (or close to it) or does it vary with the energy density quickly enough to explain baryogenesis. Some exotic theories allow for a rate that varies enough to fix baryogenesis, but I can't claim to be convinced. Yes, this...

What you are aiming at here is called Noether's theorem. It shows an equivalence between symmetries and conservation laws. Work sometimes called Noether's second theorem extends this idea to infinite dimensional Lie algebras and systems of differential equations. John

A quick caution. If you want to run your program (or maybe a function that does this part of your program) many times in rapid succession, don't use the time(0) function to seed the generator. It will be called to close together, and the numbers in the sequences from the different runs will...

For ehrenfest - For your first question, the trouble you have is about the return type. You are returning a pointer to integers. That will work for one dimensional arrays, but not for higher dimensional arrays. Your 3 by 3 array is actually a pointer to pointers to integers. That is, the first...

Maple circa the mid 1990's was not great. Current Maple is far better. However, I agree with mgb_phys that it is a nearly religious choice and the best way to make it is to see what the people you want to trade information with use.

From a particle physics point of view, it is about cross sections and channels. As noted above, a specific symmetry, called CP symmetry is broken. If CP symmetry is preserved, the event rates for particles and antiparticles in the same interactions should be identical. Empirically, we know this...

To expand slightly on what Marcus said, yes that ratio is about right. It happens to be true that matter/radiation equality (the time when the energy densities in matter and radiation were equal) happened very close to the same redshift as matter radiation decoupling. This is important...