물리:평균장_이론

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물리:평균장_이론 [2017/07/11 16:13] – external edit 127.0.0.1물리:평균장_이론 [2018/05/16 09:52] admin
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 $$e^{ax^2/2} = \sqrt{\frac{aN}{2\pi}} \int_{-\infty}^\infty dm~ e^{-Nam^2/2 + \sqrt{N}amx}$$ $$e^{ax^2/2} = \sqrt{\frac{aN}{2\pi}} \int_{-\infty}^\infty dm~ e^{-Nam^2/2 + \sqrt{N}amx}$$
 이므로 $a=\beta J$과 $x = \frac{1}{\sqrt{N}} \sum_i S_i$를 대입하면 이므로 $a=\beta J$과 $x = \frac{1}{\sqrt{N}} \sum_i S_i$를 대입하면
-$$e^{\frac{\beta J}{2} \frac{1}{N} \left( \sum_i S_i \right)^2} = \frac{\beta J N}{2\pi} \int_{-\infty}^\infty dm~ e^{-N\beta J m^2/2 + \beta J m \sum_i S_i$$+$$e^{\frac{\beta J}{2} \frac{1}{N} \left( \sum_i S_i \right)^2} = \frac{\beta J N}{2\pi} \int_{-\infty}^\infty dm~ e^{-N\beta J m^2/2 + \beta J m \sum_i S_i}$$
 이다. 여기에 대각합을 걸면 $\sum_i S_i$에만 걸리므로, 결과적으로 분배함수는 이다. 여기에 대각합을 걸면 $\sum_i S_i$에만 걸리므로, 결과적으로 분배함수는
 $$Z = \mbox{Tr} \sqrt{\frac{\beta J N}{2\pi}} \int_{-\infty}^\infty dm~ e^{-N\beta Jm^2/2 + \beta (Jm+h) \sum_i S_i}$$ $$Z = \mbox{Tr} \sqrt{\frac{\beta J N}{2\pi}} \int_{-\infty}^\infty dm~ e^{-N\beta Jm^2/2 + \beta (Jm+h) \sum_i S_i}$$
  • 물리/평균장_이론.txt
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