Recent content by jamesa00789

Yes they are of the same standard brownian motion at different time intervals.

Let Bt1, Bt2 and Bt3 be standard Brownian motions with ~N(0,1). Then what is E[Bt1.Bt2.Bt3] ? Any help would be much appreciated.

Hi, I'm not sure why I'm posting here but because Physicists generally know everything... Im British and I have a First Class Honours degree in Physics (the highest grade possible in the british system) and I'm currently doing a masters in applied mathematics and computing (finishing next...

I've used STP values n = 1.00029, T = 0C and P = 1atm and get 7.72*10^-9 s which is pretty close.

Also about the ionosphere, due to solar radiation ionising gasses in the ionosphere, there are free ions wondering around which can effect some wavelengths of magnetic radiation. Now, data being sent from satellites don't emit light, they emit radio waves with wavelengths of ~1cm, how would...

Give or take some uncertainty and the assumptions made, that probably seems about right.

Sorry, 3.33x10^-8 s

Yes, some numbers would be useful to verify this. Using the previous method, I calculated that light was slowed down by (delta t) 3.33x10^-8 seconds. So I am assuming that for nk = 1.00029 (sea level), this would mean that Pk would be the average pressure at sea level, and Tk would be the...

Thank you so much, you are a genius. I actually got pretty close to that ;)

Great, thanks for your help. Well I'm just going to use this model here, it does match up roughly with the data you provided earlier. I'm trying to calculate the time it takes for a signal to reach sea level, when emitted from a satellite 20,200km above sea level, with atmospheric effects...

Air pressure is proportional to density. I have found a model for air pressure: \text{p0} e^{-z/7000} Where p0 is the air pressure at sea level (101.33 kpa), z is the height in metres. It works surprisingly well with the table you gave above. Then hence: \text{n = } 1+0.00029 e^{-z/7000} I...

Great thanks, I actually assumed this. The pressure decreases exponentially with height, so I'll just align the two. Thanks again.

Refractive index increases from 1 in outer space to the refractive index of air at sea level. I'm trying to find an expression for the refractive index of air at a certain height, anyone? Thanks

I would check this 20min video interview of a qaunt. She has a phd in physics http://www.careerplayer.com/careers/banking-and-investment/capital-markets/quantitative-analytics-/claudia-yastremiz---director-quantitative-analyst-.aspx

It doesn't matter if your a brain box or not. I'm doing physics and then doing a masters in mathematics next year - I never got good grades throughout high school until I realized you have to study to get good grades :) Put the hours in and you'll do fine, regardless of how smart you are. One...