Tricky Casimir
Hi!
Surely, there should be a kind of Casimir attraction also in the
lateral direction.
However, you seem to make an assumption with
makes you estimate a somewhat uncontrolled approximation:
The quoted Casimir force per area is derived for infinite plates, totally...
Calculation of the Casimir effect
Letting you know that I am interested (but don't invest special effort because of this.
The interaction energy between the two finite plates should clearly be more complicated than between two infinite planes, would be interesting to see the details.
Have a clear answer for the first part: after the mesurement of spin along the B axis the particle will be in an eigenstate of spin pojected on B. Unless A and B are collinear, this is not an eigenstate of spin projected on A, thus if we make a third measuremnet (aling A again), the probability...
Not really. The number of degree of freedoms of a free bosonc is the number of Harmonic oscillators you use to describe it. Formally it is divergent, but physically you always have a small-k cutoff. But then even for a single harmonic oscialltor, the corresponding Hilber space has infinite...
"elementarity" of a particle is always scale-dependent!
It would be great (although very surprising) to learn we've reach the bottom, but the problem is that we cann't tell!
No, it is not. Unless one makes such a belief system a requirement to be called "theoretical physicist".
BTW...
down to beliefs
Well, we in the domain of beliefs and personal taste, so your position is a legitimate as mine. Just want to explain why I find the assumption of structureless vacuum im-plausible.
The point of my analogy between the real vacuum and an imaginary solid was precisely to...
So it's a matter of mathematical taste and convenience. For me it seems very strange if the same continuous Poincare-group structure what we use for the empty space (aka physical vacuum) at accessible energies would go ad infinitum to arbitrary small scale.
Imagine I give you a piece of solid...
Wow!
You quote a really impressive body of work, very interesting to learn about such developments. And sorry for not noticing that "dressed particle" approach is a term here.
I will dare to insist on my point (this is not, however, meant to discredit the "dressed particle" picture): any...
Why to dislike UV cut-offs? Any QFT presumably has them.
Hmm, what you refer here to a "fashion" seem to me the only logical explanation.
Namely, any QFT -- whether it comes from particle physics or a condensed matter problem -- is a convenient approximation. We stuff an infinite number of...
Your question is quite broad, I'd just like to comment that QFT is about the ways to solve for quantum mechanical behaviour of a system with an infinite number of degrees of freedom (a field), whenever such physical model is applicable. It by no mean has to deal with electromagnetism (that is...
cos (\pi n) for n = even integer is equal to 1,
while for n = odd inetger, it is equal to -1.
The function (-1)^n has the same property.
Since n is an integer and must be either even or odd,
we can replace cos (\pi n) with (-1)^n .
This is not a homework
Just to make sure there is no misunderstandning: this a research problem, not a homework. (Although what was yesterday's research may turn to be today's homework, but that's a different issue...)
I have been playing around with the following rather elementary 1d field theory problem and got stuck. May you have some good ideas on it.
Let us consider an ideal 1-D elastic spring with just one polarization direction (say, transverse displacement in y-direction while the unperturbed string...
It depends. The problem and solutions proposed in the literature are mostly philosophical. However, if a particular mechanism of solution, like Legett's [mentioned above] or Penrose's leads, to experimentally verifiable predictions in the areas not yet tested, then it is a matter of physics.
But why fear? I would say "fascination and excitement". Many students of quantum mechanics (including me) get "hooked" precisely by the contraintuitive nature of QM and the sense that it never completely fits into your mind.