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Moments, correlations, and cumulants

From equation 6.35, the moments of k spins in the Ising system are given by
eqnarray2755
In the thermodynamic limit this simplifies as
eqnarray2775
where
equation2802

From the moments, the correlations and cumulants may be calculated. Figures 6.86.11 show moments of orders 1 through 4 of neighboring spins. Figures 6.126.14 show the correlation functions of orders 2 through 4 of neighboring spins. Figure 6.15 shows the cumulant function of orders 4 of neighboring spins. Recall that the first three correlation and cumulant functions are equal by order.

 figure2842
Figure 6.8: First order moment - moment of one spin. Note the transitional behavior in the region of the increase in the entropy, where the states tex2html_wrap_inline14507 becomes dominated by tex2html_wrap_inline14509. 

 figure2846
Figure 6.9: Second order moment of two neighboring spins. 

 figure2850
Figure 6.10: Third order moment of three neighboring spins. 

 figure2854
Figure 6.11: Fourth order moment of four neighboring spins. 

 figure2858
Figure 6.12: Second order correlation of two neighboring spins. 

 figure2862
Figure 6.13: Third order correlation of three neighboring spins. 

 figure2866
Figure 6.14: Fourth order correlation of four neighboring spins. 

 figure2870
Figure 6.15: Fourth order cumulant of four neighboring spins. 



David Wolf
Tue Mar 25 08:11:49 CST 1997