Recent content by eneacasucci

I was referring to the collective lattice displacement field (the deviation of atoms from equilibrium).The reason I phrased it as 'the normal mode is the wave' is that in a periodic crystal structure, the normal modes of vibration take the form of traveling plane waves (characterized by...

Indeed, in Kittel's discussion of phonons, it states: "A phonon of wavevector ##\mathbf{k}## will interact with particles such as photons, neutrons, and electrons as if it had a momentum ##\hbar\mathbf{k}##. However, a phonon does not carry physical momentum." Is it correct what I'm writing in...

I am currently reading Kittel's Introduction to Solid State Physics and am confused by the terminology regarding phonons. On page 99 (8th ed.), regarding Eq. 27, Kittel writes: "The energy of an elastic mode of angular frequency ## \omega ## is ## \epsilon = (n + 1/2)\hbar\omega ## when the...

This explanation is super informative and accurate, I cannot thank you enough for this. My notes were wrong and I was so confused about it.

I've found this image online (ref: https://edurev.in/t/188018/Origin-of-Energy-Bands ), it should be the graphical representation of the potential binding energy between two nearest-neighbor atoms. I don't understand how it can be correlated to the Lennard-Jones pontential graph: , in which we...

I found this image on the wikipedia italian page for the Lennard-Jones potential and I think the derivative displayed are wrong: not only in that reange (below r_eq) the negative derivative of the force should be negative and vice versa, but also the physcal meaning is that F(r) = -...

thank you so much, that is exactly what i was asking

##2\pi \int_{-1}^1 d\mu' = 4\pi## we can't write this, in our case because we have a function ##\varphi## that depends on ##\mu## (or ##\theta##) so the only integral that we can directly solve is the one related to the azimuthal angle (that gives the ##2\pi##), because none of the functions...

Thank you so much! Could I ask you also about this mathematical part "the integral over Omega in spherical coordinates has a part that is shown with the polar angle theta and then there is another integral from 0 to 2\pi for the azimuthal angle. This last integral should have as an integrand 1...

I have a question about the neutron transport equation, my question is more about mathematics, from the book Duderstadt Hamilton I tried to make the calculations, it should be quite simple but still I don't understand where the 2\pi terms went... the integral over Omega in spherical...

So to make it discontinuous we should explicitly define a piecewise function like: f(x)=ln(x) for x>0 and f(x)=0 for x≤0? It is not enough to say "consider ln(x) over whole R" then, right?

it is correct to say that if we consider the whole of R as the domain, the function ln(x)is not continuous, whereas if we consider the domain of the function as the domain, then it is continuous?

oh yes right, I wasn't thinking about it but of course because as per definition: The radius of a circle is perpendicular to the tangent at every point on the circle

Thank you, i Think it is clearer now. I couldn't find on books proper information about those geometrical constructions. So it should be something like this

image construction with concave and convex mirrors I don't know exactly how to explain it but what I have noticed is that when I use the rules for image construction with concave and convex lenses the image is wrong if I don't use the extension of the ray to the tangent to the mirror (purple...