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Questions tagged [variance-gamma]

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2
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1answer
89 views

Characteristic function of CGMY model

I have a basic question about the CGMY model which has characteristic function $$ \Gamma(-Y_p)\left((M-iu)^{Y_p}-M^{Y_p}\right)+\frac{C_n}{C_p}\Gamma(-Y_n)\left((G+iu)^{Y_n}-G^{Y_n}\right) $$ whith $...
3
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0answers
85 views

Can the vega of ITM call-options be negative when the distribution of the underlyings returns is negatively skewed?

While calculating european call option prices, using the variance-gamma model formula provided by Madan, Carr & Chang (1998), I noticed that, holding all other things constant, the value of an ITM ...
8
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2answers
351 views

Confusion with volatility smiles implied by different models

I am reading a book "The concepts and practice of mathematical finance" by Mark Joshi. In Chapter 18 he discusses the shapes and dynamics of smiles under different models. I do not understand what is ...
0
votes
1answer
77 views

Strictly positive variance gamma process?

My goal is to obtain a strictly positive variance-gamma process for the variance process such that, $$Y_{t+1} = Y_t + \mu\Delta + \sqrt{v_t\Delta}\,\,\varepsilon^y_{t+1}\\ \qquad \qquad\quad \,\,\...
2
votes
1answer
226 views

Cumulants of variance gamma with stochastic arrival (VGSA) model

The characteristic function of the VGSA model is defined as a specific parameterization of the characteristic function of the CIR (Cox-Ingersol-Ross mean reverting process) time-change: $ \mathbb{E}e^...
3
votes
0answers
207 views

Risk Neutral Variance Gamma

In the risk neutral version of the Variance Gamma model the stock dynamics are $$S_T=S_0 e^{ (r-q+\omega)t + X(t;\sigma,\nu,\theta)}$$ with $$\omega=\frac{1}{\nu}\ln\left(1-\theta \nu - \frac{\...
3
votes
1answer
87 views

What is the tail index for NIG and/or VG?

...as a function of NIG (Normal Inverse Gaussian) or VG (Variance Gamma) parameters, obviously. I've read that the NIG $\alpha$ is related to the $\alpha$-stable tail parameter, which conversely maps ...
1
vote
1answer
141 views

Why doesn't VG flatten volatility skew for short term options?

The VG process, from my inexpert point-of-view, seems to nearly perfectly model equity distributions. For longer term options, there is little to no volatility, skewness, or kurtosis parameter skew. ...
2
votes
1answer
386 views

Closed form european option prices for a variance gamma process with a randomly distributed drift, volatility, and variance rate

Does an option pricing model with a closed form European option price exist that takes into account randomly distributed drift, volatility, and variance rate? I prefer a modification to the variance ...
8
votes
4answers
2k views

How to simulate stock prices using variance gamma process?

I want to simulate stock prices with the variance gamma process. The model is given by: $S_T=S_0 e^{ {[}(r-1)T + \omega + z{]}} $ where $S_0= $ starting value $T= $ Time $\omega=\frac{T}{\nu}ln(1-...