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Homework Statement
I have to show that (the question says deduce from the fact that magnetization is monotonically increasing and a concave function for h>0)
[tex] \left< \sigma^2_{j} \right> - \left \sigma_j \right>^2 \geq 0 [/tex]
and [tex]\left< \left( \sigma^_{j} \right> - \sigma_j \right)^2 \right> \geq 0 [/tex]
Homework Equations
This in the context of a spin-1 Ising paramagnet in external field [tex]h[/tex]
I have the fact that the magnetization is monotonically increasing and a concave function for [tex]h > 0[/tex]
The Attempt at a Solution
I know the expression for an arbitrary observable;
Basically I have;
[tex]\left< \sigma_j \right> = \frac{\sum_{\sigma} \sigma_j e^{\beta h \sum_{j=1}^{N} \sigma_j}}{Z}[/tex]
I'm just not sure how to use the concavity and the fact that m is monotonically increasing to find this result.
Any help is greatly appreciated.