# Questions tagged [differential-equations]

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### Book/reference to practice stochastic calculus and PDE for interviews

I will be going through interview processes in next months. I would like to have a book/reference to practice the manipulation of PDE, and stochastic calculus questions. For example, I get a bit ...
598 views

### Prove $E_{\mathbb Q}[X_t | \mathscr F_u] = X_u$ given $Y_t$ is a martingale

Edit years later: No idea why I'm upvoted. I actually am not sure how I'm correct. But maybe I haven't forgotten conditional expectation as much as I thought I have. We are given a filtered ...
251 views

### How to solve numerically the IDE of GUILBAUD & PHAM model?

By the Guilbaud & Pham model (Optimal high frequency trading with limit and market orders, 2011), the authors said that integro-differential-equation (IDE) can be easily solved by numerical method....
274 views

### Conditional Expectation of Integral of Squared Brownian Motion - PDE Approach

I am looking to compute the following using Ito's formula. $$u(t,\beta_t) = \mathbb{E}(\int_t^T\beta_s^2ds|\beta_t)$$ Knowing the properties of brownian motion, it is rather easy to show that the ...
103 views

### Perpetual Option Paying Chooser Option

A perpetual option solves the ODE $$rSV_S+\frac{1}{2}\sigma^2S^2V_{SS}-rV=0$$ The general solution is $$V(S)=aS+bS^{\gamma}$$ where $\gamma=-\frac{2r}{\sigma^2}<0$. For an American put option with ...
494 views

### Transformation of local volatility model

Assume we have an SDE $$dX_t=\mu(X_t)dt + \sigma(X_t)dW_t$$ where $\sigma>0$ and $W_t$ is a Wiener process. Is there a transformation $y(X_t)$ that will make the dynamics of the transformed process ...
185 views

### Implied Volatility is the harmonic average of Local Volatility

I am trying to demonstrate the famous result that states that when $T \rightarrow 0$, the Implied Volatility is the harmonic average of Local Volatility. I am st the final stage, and I have the ...
170 views

### Black-Scholes differential equation rewritten [closed]

I have seen that the Black-Scholes equation $$\frac{\partial V}{\partial t}+\frac{1}{2}\sigma^2S^2\frac{\partial^2 V}{\partial S^2}+ rS\frac{\partial V}{\partial S}-rV=0$$ can also be written in the ...
1 vote
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### To gamble or not to gamble! (solving a system of ODEs maybe?)

Assume we have some money. At every point in time $0\le t \le T$, we can take either action 1 that is to keep our money until $T$ say in a bank and have an expected return of $f(t)$ or take action 2 ...
112 views

### Closed form formula of asset that incorporates another asset's interest rate on top of its own

I'm trying to find a closed form formula for the price of an asset $D$ that has the following properties: The asset grows by some interest rate $\mu$ at every instant. Another asset's ($B$) interest ...
1 vote
323 views

### Using the risk neutral version of the First Fundamental Theorem of Asset Pricing to derive a partial differential equation

I have to use the risk neutral version of the First Fundamental Theorem of Asset Pricing to derive a partial differential equation (PDE) that the price/value process, $V_t = F(t,S_t)$, of a self-...
88 views

### Proof verification : risk free rate [closed]

I want to prove that $$r_t = \theta + (r_0 -\theta)e^{-kt}$$ satisfies $$dr_t = k(\theta-r_t)dt, \ r(0) = r_0$$ I have \begin{split}\frac{1}{\theta - r_t} dr_t = kdt \Rightarrow & \int_0^t \frac{1}...
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1 vote
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### The solution to arithmetic brownian motion

I would like to obtain an explicit solution to $X$ when it satisfies $$dX_t = \mu X_t dt + \sigma dW_t, X_S = x$$ Here, $S > 0$, and we want an explicit solution for $X_T$, $T > S$. I am not ...
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1 vote
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### SVCJ (SVJJ) Duffie et. al Model implementation in Matlab

I'm attempting to implement aforementioned SVCJ model by Duffie et al in MATLAB. so far without success. It's supposed to price vanilla (european) calls . parameters provided, the expected price is: ~...
### Evaluating the SDE $dX_t = t\,dS_t$
The process $S$ is a geometric Brownian motion with an SDE: $dS_t = S_t(\sigma\, dB_t + \mu\, dt)$. I'm stuck evaluating $E(X_t)$ and $V(X_t)$, where $dX_t = t\,dS_t$.