The Mermin-Wagner Theorem - Condensed Matter Theory Group
The Mermin-Wagner Theorem - Condensed Matter Theory Group
The Mermin-Wagner Theorem - Condensed Matter Theory Group
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k<br />
How symmetry breaking occurs in principle<br />
Actors<br />
Proof of the <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem<br />
Discussion<br />
A, A †<br />
<br />
+<br />
<strong>The</strong> Bogoliubov inequality<br />
<strong>The</strong> <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem<br />
= S <br />
− +<br />
(−k + K), S (k − K)<br />
k<br />
= <br />
<br />
i(k−K)(Ri−Rj)<br />
e S −<br />
k<br />
i,j<br />
= 2N <br />
≤ 2N 2<br />
Si i<br />
i<br />
= 2 2 N 2 S(S + 1)<br />
(S x i ) 2 + (S y<br />
i )2<br />
i<br />
S +<br />
j<br />
Andreas Werner <strong>The</strong> <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem<br />
+<br />
<br />
+ S +<br />
j<br />
<br />
−<br />
Si
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