SLIDE 1 BERLIN ICRANet Pescara
Variational Perturbation Theory Variational Perturbation Theory
Hagen Kleinert, FU BERLIN & ICRANet Pescara
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- Hartree-Fock Theory
- Higher Effective Action
But no good in strong-coupling limit!
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Principle of Minimal Sensitivity
(Bridge to Seznec + Zinn (Bridge to Seznec + Zinn-
Justin 1979 previous lecture ) previous lecture )
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Effective Classical Partition Functions Effective Classical Partition Functions
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SLIDE 7 1.0 0.5
0.5 1.0
0.4 0.3 0.2 0.1
0.1 0.2
SLIDE 8 Can go to Higher Can go to Higher-
Order Effective Classical Partition Functions Effective Classical Partition Functions Exercise first at at T=0 Exercise first at at T=0 Higher Higher-
Order Variational Perturbation Theory (1990) Variational Perturbation Theory (1990)
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(*6* (*6*
7/7 7/7 * *
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2 4 6 8 10 1 2 3 4
SLIDE 16 7% 7%
0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0
% % 1*8 1*8
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7*79 ,8 7*79 ,8
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= =
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