- #1

Hl3

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## Homework Statement

The occupation of each single-particle state with wave vector k =/= 0 in the ground state is given by n

_{k}= <0|b

_{k}

^{†}b

_{k}|0>

where b and b† are bogoliubov transformaition. Find an expression for n

_{k}.

b

_{k}= cosh(θ)a

_{k}- sinh(θ) a

^{†}

_{-k}

b

_{k}

^{†}= cosh(θ)a

^{†}

_{k}- sinh(θ)a

_{-k}

## Homework Equations

## The Attempt at a Solution

I don't fully understand the notaition with zeros. I believe n

_{k}would equal to 0, however question asks for the expression for n

_{k}. thnaks in advance