Soft turning-point connection
At a simple turning point x_t with V′(x_t)>0, an exterior wave decaying to the right, C exp[−∫_(x_t)^x κ dx]/√κ, determines the leading allowed-left wave 2C cos[∫_x^(x_t)k dx−π/4]/√k.
Key knowledge
At a simple turning point x_t with V′(x_t)>0, an exterior wave decaying to the right, C exp[−∫_(x_t)^x κ dx]/√κ, determines the leading allowed-left wave 2C cos[∫_x^(x_t)k dx−π/4]/√k. The finite local Airy solution replaces the divergent WKB amplitude near the turning point.
Values and equations
C e^[−∫_(x_t)^xκ dx]/√κ ⇒ 2C cos[∫_x^(x_t)k dx−π/4]/√k
- x,x_t
- Position and simple turning point m
- k,κ
- Positive allowed/forbidden wavenumbers m⁻¹
- C
- Common WKB coefficient; m⁻¹ for normalized 1D states
- V,E
- Potential energy and eigenenergy J
Conditions and scope
- V(x_t)=E, finite nonzero slope and an overlap region where both local linear-potential Airy asymptotics and WKB apply. The specified forbidden-side solution has no growing component.
- The reliable implication is from a pure decaying tail to the oscillation; reversing an approximate oscillation can generate an undetermined growing tail. Reflect the coordinates for the opposite slope. Higher-order or coalescing turning points need other uniform methods.
Sources · 1
References
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Evidence and review
Quantum Physics III: chapter 3, semiclassical approximation: §3.3 equation 3.3.1, §3.4.1 equations 3.4.19–3.4.23 and 3.4.33–3.4.44, printed pages 59 and 63–66: Airy matching and coefficient/phase. Explicit one-direction reliability warning after 3.4.44 and mirrored connection 3.4.45–3.4.47 retained.
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Entry details
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