Recent content by K space

This is an exercise from an old examination that I am trying to understand by following the given solution to this problem. The exercise is about to calculate the four spin average <SiSjSkSl> and the indices i,j,k and l, given a Hamiltonian H. Solution: The problem is that i can't follow the...

Since the force is the negative gradien of its potential energy, in a one dimensional case as this we can write, F=-\frac{dU}{dL} or U=-\int FdL Once obtained the potential energy, use the defenition of the heat capacity at constant length, C_L=(\frac{dU}{dT})_L With the given...

I'm a bit confused now when I see different opinions about if the expressions are equal. More simply, if I expand |ψ>=\sum_{a}c_a|a>, will that always implie that I am allowed to expand the corresponding bra as: <ψ|=\sum_{a}c_a^*<a| (with summation over same a) to use in an expression containing...

I'm new to the concepts of quanum mechanics and the bra-ket representation in general. I've seen in the textbook that the compleatness relation is used all the time when working with the bra and kets. I'm a bit confused about how this relation is being used when applied more than once in a...

I'm given an expression for the pressure of air with height z, as P(z)=P(0)e^{(-mgz/k_bT)} Where m is the molecular weight of air. It's know that the pressure of water varies with height above sea-level due to the variation of the pressure of the air. The exercise is about to show that the...