Recent content by Dyson

In my opinion, if the two atoms are polarized having the same spin, they must not form the H2 which means the covalent bond can not be formed. And the interactions between the same spin will be similar to the source of van der waals force which contains dispersion force, inducing...

As far as i know, for discrete data, i can probably utilize the Lagrange's Interpolation or Newton's Interpolation to generate a continuous function. Then, the next step, i think i can calculate the integral using simple Simpson rule or other methods for numerical calculation. Maybe the...

I calculate it like this: \frac{\delta n(r)}{\delta \rho(r^{\prime \prime})}=\int dr^{\prime} r^{\prime}\delta (r^{\prime}-r^{\prime \prime })f(r, r^{\prime})=r^{\prime \prime}f(r,r^{\prime \prime}) So, I think your result is right.

You may solve the problem like this: The solution of the equation can be written as the superposition of e^{ikx} and e^{-ikx}, then, \phi=Ae^{ikx}+Be^{-ikx} In terms of the boundary condition, 0=Ae^{ika}+Be^{-ika} 0=Ae^{-ika}+Be^{ika} These are two equations on two variables A and B. A and B...

You can find complex numbers in many famous equations such as Schroedinger equation, Dirac equation... It seems we often use the form of e(ix). X often represents the phase factor or a certain type of operator. The frequent Fourier transformation is also relative to the complex numbers. We can...

I tend to calculate it in the representation of S_{z}'s. So, S_{z}\mid +>=\frac{\hbar}{2}\mid +> S_{z}\mid - >=-\frac{\hbar}{2}\mid -> Then, according to the definition of exp(\hat{F}), exp(\frac{iS_{z} \phi}{\hbar})\mid + >=exp(\frac{i\phi}{2})\mid + > exp(\frac{iS_{z} \phi}{\hbar})\mid -...

I haven't found any errors.

For the friction, the curve integral of a certain closed contour is not zero. So it is none sense to define a field of it. The curve integral makes sense only when you have defined a definite path.

OH, sorry, my reply actually repeated the RedX's... To my surprise!

My views are as follows: I first regard the kinetic energy is a kind of energy which can show the magnitude of work resulted from the total external force. This definition, to a certain extend, also fits to our intuitions. Then, we may write the formula which may appear frequently in most...

Hi, my opinions are as follows. I hope they can be helpful for you. At the macroscopic level, the diffraction can be observed when the wavelength is comparable to the width of the slit. At the microscopic level, according to your views, the diffraction can be thought of the superposition of...

Using the pertubative expansion and the definition of N-point Green's function.Because of the pertubation,i can only calculate the 2-point Green's function.But i really can't find the equation it satisfies.

Hello! Something about N-point Green's function in QFT really troubles me... In the path-integral formalism,why will we introduce the N-point Green's function? I mean is it enough because we have calculated the 2-point green's function. And in the canonical formalism, it seems we can finish...

Thanks! You give me a guide to learn more knowledge on effective action!

Hello! I wonder is there exist a way to deduct the conserved current equation, generator of the symmetry transformation and so on from a total quantum L with the help of action principle? Many books i have seen deduct the physical quantity from the classical L or...