/sci/ - Science & Math » Thread #9578512

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Anonymous Sun 11 Mar 23:34:18 2018 No.9578512 View Reply Original Report

Quoted By: >>9578754 >>9578759 >>9578872

>fall for the physics meme
>buy Ashcroft
>read first chapter
>cgs units
>handwavy af use of $\frac{\mathrm dt}\tau$ as an infinitesimal probability where any sane mathematician would simply postulate an exponential law
>writes $\frac{\mathrm d\mathscr E}{\mathrm dT} \left(-\mathbf\nabla T\right)$ but it's actually a product, not the derivative evaluated at $-\mathbf\nabla T$
>first exercise is literally expected to be solved by approximating a binomial law as a Poisson law with $n\ =\ 1$ (and would have been both more rigorous and trivial af if postulating an exponential law as stated above)
>second exercise requires assuming $\left\langle \mathbf v^2 \right\rangle\ =\ \left\langle \mathbf v \right\rangle^2$
And you fuckers make fun of CS for its lack of rigorous math...

Anonymous

Anonymous Mon 12 Mar 2018 01:11:18 No.9578754 Report

Quoted By: >>9578839 >>9578927

>>9578512
I kinda understand too why you are frustrated, because sometimes physicists, in order to make self contained books for people without much mathematical knowledge in certain fields, have to use some weird interpratation that is really shit, or it makes it impossible to understand or use. However, if you understand the math, then just learn the physics you moron. Understand why they are making those assumptions, what systems can you imagine that behave in certain ways, try different approaches and look for physical examples and nonphysical ones. I.e. don't complain about the lack of rigor, because physics is not about that you twat. Also, people make fun of CS, mainly because it's a shit degree except for few academic positions, and software developers are better off just practicing how to code.

Anonymous

Anonymous Mon 12 Mar 2018 01:14:44 No.9578759 Report

Quoted By: >>9578883

>>9578512
SI metric units > Amerimutt retard units

Anonymous

Anonymous Mon 12 Mar 2018 01:52:34 No.9578839 Report

Quoted By: >>9578862

>>9578754
>in order to make self contained books for people without much mathematical knowledge in certain fields
lmao the same exercise with the Poisson law also involves a convolution product. Anybody who knows that has no excuse for not mastering the exponential law. Physicists are retards.

Anonymous

Anonymous Mon 12 Mar 2018 02:00:45 No.9578862 Report

Quoted By: >>9578878

>>9578839
Why are you so sure about that? Maybe he wants to build some result that's useful in certain cases or whatever. Why not post the problems and shit instead of complaining like a faggot?

Anonymous

Anonymous Mon 12 Mar 2018 02:05:38 No.9578872 Report

Quoted By:

>>9578512
People are just jealous of the CS master race. Ignore them and tell them to start practice making me my morning sausage egg McMuffin

Anonymous

Anonymous Mon 12 Mar 2018 02:08:06 No.9578878 Report

Quoted By: >>9578917

>>9578862
Assumption: In Drude's model, at any time, the time before the next collision and since the previous collision is random and such that the probability of the collision occuring during an infinitesimal time $\mathrm dt$ is $\frac{\mathrm dt}\tau$ .

Exercise is called Poisson distribution.
Question a: show the probability of the next collision not occuring before $t$ is $\mathrm e^{-\frac t\tau}$ .

Question b: show the probability of the next collision occurring between $t$ and $t\,+\,\mathrm dt$ is $\frac1\tau\,\mathrm e^{-\frac t\tau}\,\mathrm dt$

Tell me what I don't gain by replacing the assumption with "The time before the next collision and since the previous one both follow an exponential law $\mathscr E\left(\tau\right)$ ."

Anonymous

Anonymous Mon 12 Mar 2018 02:11:28 No.9578883 Report

Quoted By:

>>9578759
>cgs is American

Anonymous

Anonymous Mon 12 Mar 2018 02:23:46 No.9578917 Report

Quoted By:

>>9578878
Well, again, physicists who are in undergrad aren't expected to know probability distributions, or at least by heart. Obviously someone in the field will know that, but the exercise is trying to build everything using physical ideas, because that's how a lot of physical models are created. If you find it trivial, go look into a higher level text and see how you do.

Anonymous

Anonymous Mon 12 Mar 2018 02:26:53 No.9578927 Report

Quoted By:

>>9578754
>don't complain about the lack of rigor, because physics is not about that you twat
fpbp

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