Recent content by inempty

I think this depends on what you mean by "relativistic". Of course in solids most gapless excitations don't move in the speed of light and real relativisitc effects are not present. But for gapless particles, fundamental equations in the "relativistic" form are often used to describe their...

In the context of field theory, a gap in dispersion relation really means a mass. So a gapless excitation, like goldstone boson, doesn't have a mass hence is always relativistic. This is like the situation of photon in relativity.

We have many engines to search the literature, such as sciencedirect and so on. And we also have google scholar to search the whole literature. Is it a good idea to use only google scholar since it looks complete enough? What's your opinion?

agree with parlyn. The mixing angle couldn't be determined by theoretical considerations but the form of orthogonal matrix can.

I'm not familiar with this topic but I think the key point of neutrino mixing is to write flavour eigenstates in terms of different mass eigenstates and vice versa. But a mass (flavour) eigenstate multiplied a phase factor is still a mass (flavour) eigenstate so It looks that these phase factors...

I think it should be interaction Hamiltonians instead of Lagrangians, since fields in Lagrangians aren't field operators and we can only write field operators in terms of creation and annihilation operators. In addition, to remember the difference between creation/annihilation operators in...

In interaction picture, we can actually do this. However, the creation/annhilation operators are different from ones in the free-particle-case. In other words, if we act a interacion-picture creation operator on a vacuum in-state, we couldn't get a one-particle in-state, Which makes the external...

You could see Weinberg I, chapter 7,8 to find examples. In simple words, the idea to quantize constrained systems is to do canonical transformations, making constraints the forms that just fix the values of several couples of conjugate variables, and to remove these couples. This method is...

I think the point is that to multiply a mass eigenstate with a phase factor should not change the physical result of neutrino mixing, so we can choose to make the matrix real, whose general form will be like this if it is unitary. This is possible for 2-flavour case since we have 4 phase factors...

Things about parastatics have been demonstrated clearly by xepma and element4. Only what I want to tell is an answer, which is simpler and straighter but not as complete as above, to the question and what's written below can also be regarded just as a sidenote.:smile: We needn't hamilitonian be...

3q：）

Hi, I'm a chinese undergraduated student. As I want to apply to some American universities for PhD, I took GRE general test these days. However, I have no concept with what they want to know about applicants through their scores? And how professors will realize applicants with their scores? I'm...

Oh, I got it :) you are right.

Why? I couldn't understand it clearly. After simple calculation it turns out that the basis functions are corresponding to x,y and z. They're not momentum operator's eigenfunctions.

haha