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Black & Scholes : Gamma Г
Issued on July 16 2011 par Strategies-options.com
In the Black & Scholes model, gamma Г is just the second derivative of an option price with respect to the spot.
Gamma Г is the second derivative of an option price with respect to the spot.
Gamma is a measure of convexity.
I - Maths behind the convexity
For a call :
Γ = ∂² C / ∂ S²
Γ = ∂ Δ / ∂ S = ∂ (exp ( - q.τ ) . N( d1 ) ) / ∂ S
Γ = exp ( - q.τ ) . ( 1 / ( S σ√τ ) ) . N’( d1 )
For a put :
Γ = ∂² P / ∂ S²
Γ = ∂ Δ / ∂ S = ∂ (exp ( - q.τ ) . N( d1 ) - exp ( - q.τ ) ) / ∂ S
Γ = exp ( - q.τ ) . ( 1 / ( S σ√τ ) ) . N’( d1 )
Call and put gamma are the same !
II - Means and 2D graphs
A weak gamma means a small delta variation for a spot move.

A strong gamma means a great variation in delta for a spot move.

III - 3D graphs

■ Gamma is the same for a call or for a put with the same parameters and variables.
■ Gamma is strong as expiry nears.
■ Gamma is maximum around the strike level
Ditm and Dotm options have little to nil gamma.
Next : Black & Scholes : Theta θ
Previous: Black & Scholes : Delta ∆
Pdf connexes :
- Understanding N(d1) and N(d2) : Risk-Adjusted Probabilities in the Black-Scholes Model
- Black-Scholes Option Pricing Model
OPTIONS PRICING MODEL - INDEX
OPTIONS PRICING MODEL - INDEX
OPTIONS PRICING MODEL - CHAPTER I
OPTIONS PRICING MODEL - CHAPTER II
OPTIONS PRICING MODEL - CHAPTER III Strategies-options.com
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