Recent content by tom8

I am trying to use Weighted Least Squares with a linear model: Y = Xβ + ε, where Y are some observed measurements and β is a vector of estimates. For example, in this case β has two terms: intercept and slope. The weighted least squares solution, as shown here, involves a weight matrix, W...

I see, thank you!

Oh I see. Now I understand your point, but (sorry) isn't the Fermi surface for 1D a line, 2D a circle and 3D a plane, how come now it is a plane for 1D and a cylinder for 2D?

And how is this different? In 1D I can also say that individual points in one line are mapped to isolated points in the other. Collectively, these points constitute the line. In 2D the same is true. Sorry I can't just get it. P.S. let's stick to ideal Fermi surface for the moment.

So you are saying that the divergence in 1D is more than in 2D per one nesting wavevector. If we will sum over all the possible nesting wave vectors in 2D, then so we do in 1D and it is the same. But, if we look at the figure, the 1D case has two parallel lines. Anything other than a horizontal...

Consider the Lindhard response function: \chi(\vec{q})=\int\frac{d\vec{k}}{(2\pi)^d}\frac{f_\vec{k}-f_{\vec{k}+\vec{q}}}{\epsilon_\vec{k}-\epsilon_{\vec{k}+\vec{q}}} where ##\vec{q}## is the wavevector, ##\epsilon## is the free electron energy and ##f## is Fermi-Dirac distribution function. For...

I am a condensed matter grad. student, but do not work on Graphene. I am interested in learning about the fundamental physics in graphene (e.g. the need to use Dirac equation to represent the motion of electrons). I know that many books are there, but not all are geared towards fundamental...

One of the reasons for me to pursue the PhD path was that you are (more) successful when your work have more impact on the society as a whole. One such way to do that is to publish papers, since these, especially at the basic sciences level, eventually affect the life of the people as a whole...

Right. I am looking for 'only' the past couple hundred years. As to what field, I am considering Physical Sciences mainly (i.e. excluding medicine). I would expect that, at least before the beginning of the last century, there was only 'physics' and 'math' to large extent.

Both are fine. Apparently it is hard to separate them, for example Newton was both physicist and mathematician (at least from contribution point of view).

I am looking for a book on the history of science. I do not want one that is targeted to 'general public', in the sense that I want it to be more towards the academic community, i.e. more deeply presented and cited, etc. Are there any recommendations?

Thanks for your reply. I agree that I have to read more about this, especially given my lack of knowledge in this health-related field.

I am doing a project about the SEIR model, which is an epidemic model consisting of 5 ODEs, that classifies people according to 5 categories: S: Susceptible E: Exposed I: Infected R: Recovered I am looking into CDC's website and would like to take Flu as an example. My medical knowledge is...

Thanks for the discussions. I was under the impression that nuclear power is the cheapest, now I think I got my facts straight. I expect that after Fukushima disaster, the use of nuclear power is going to be diminished...

I guess I meant that it is cheaper than other forms of energy, like oil or gas. But perhaps this depends on the exact price of these two.