Questions tagged [stochastic-processes]
For questions about stochastic processes, for example random walks and Brownian motion.
16,784 questions
3 votes
1 answer
224 views
How does the Black-Scholes equation handle drift?
I've been reading about the Black-Scholes formula on wikipedia and investopedia and it seems like a lot. My understanding is very limited, but naively it makes sense to me one would be able to assign ...
-1 votes
0 answers
32 views
Why do we need \rho (utilization)<1 in queuing theory?
I’m studying basic queueing theory, in particular a single–server queue with one arrival stream and one server (a G/G/1 type setup). Let A be the interarrival time with mean 𝔼(A), B be the service ...
3 votes
2 answers
110 views
Martingales convergence a.s.
Suppose we know that $P(X=1)=p, P(X=-1)=q=1-p$ We have a martingales a) $M_n = (\frac{q}{p})^{S_n}$, b) $M_n = S_n - n(p-q)$ where $S_n =\sum_{i=0}^n X_i$,( $X_i$ iid). How to show (in a simple way) ...
3 votes
0 answers
100 views
Stochastic exponential and martingales
I have a Question regarding the chapter 5.5.(Girsanov Theorem) of the Book "Brownian Motion,Martingales, and Stochastic Calculus" from le Gall. There is stated in Prop 5.21, that if D is a ...
0 votes
0 answers
23 views
If a Stochastic Differential Equation is bounded [0,1], can we assume that models probability failure; [closed]
I want to model a system in terms of probability of failure. If I use a stochastic differential equation that is bounded [0,1], can I assume that it models probability failure? I know that failure ...
1 vote
1 answer
36 views
Family of i.i.d. random variables is ergodic under shift
Let $(S, \mathcal{S})$ be some measurable state space, $\Omega := S^{\mathbb{N}_0}$, $X_i$ the coordinate maps, $\mathcal{A} := \sigma(X_0, X_1, \dots)$ and $\theta: \Omega \rightarrow \Omega, (x_0, ...
0 votes
0 answers
27 views
Solution to SDE as measurable function of initial value
In Schilling's "Brownian Motion", it is argued in Remark 21.24 that if the stochastic process $X^x$ is the solution to an SDE with initial value $x\in\mathbb{R}$, then it depends measurably ...
0 votes
0 answers
24 views
Convergence of transform of stochastic processes to transform of Brownian bridges
I have two sequences of independent stochastic processes $X^n$ and $Y^n$ that are known to converge weakly to the Brownian bridges $\mathcal X$ and $\mathcal Y$, respectively. For a continuous ...
0 votes
1 answer
20 views
decomposition of levy process under subordination
Let $S$ be an increasing Levy process. Let $Z$ be another Levy process in $R^d$, independent of $S$. A standard result is $X\equiv Z_{S}$ is also Levy. Now, to characterize the distribution of $X$, we ...
3 votes
1 answer
60 views
Convergence of Random Walk and Bounded Martingals
First, consider a symmetric random walk $X_n := Y_1 + \dots + Y_n$, with $P(Y_k = \pm 1) = \frac{1}{2}$ for all $k \in \mathbb{N}$. For $c > 0$ define the stopping time $T_c := \min \{n \geq 0 \,|\,...
3 votes
0 answers
58 views
Representation of stopping time
Let $X$ be a Brownian semimartingale $$ X_t = X_0+\int_0^t\mu_s\,ds+\int_0^t\sigma_s\,dW_s $$ with $\mu$ and $\sigma$ bounded and cadlag, $W$ Brownian motion and $$ \sigma_s = \sigma_0+\int_0^t\mu^{\...
3 votes
0 answers
65 views
A multilinear version of Cauchy-Schwarz inequality
Let $\mathbb{H}_1,\mathbb{H}_2$ be two vector spaces over $\mathbb{R}$, and assume that we have a miltilinear function $f:\mathbb{H}_1\times \mathbb{H}_1\times \mathbb{H}_2\times\mathbb{H}_2\to \...
-2 votes
0 answers
47 views
Hilbert Schmidt operator and random process
One sometimes studies the operator $$ f(s) \mapsto \int_0^1 {\rm cov}(X_\tau X_t) f(\tau) \, d\tau, $$ where $ X $ is a stochastic process (not necessarily ergodic). What is the meaning of this ...
1 vote
2 answers
156 views
Beginner question about Option pricing, Risk and Rational portfolios
I'm a physics student currently reading "Econophysics and Physical Economics by Peter Richmond, J¨urgen Mimkes, and Stefan Hutzler" for the first time and this is my first touch with the ...
3 votes
1 answer
73 views
Running supremum and complete $\sigma$-algebra
I am asked to prove the following: Given $X=(X_t)$ a continuous process and $f : \mathbb{R} \to \mathbb{R}$ measurable. If $(\mathcal{F}, P)$ is a complete $\sigma$-algebra, then $\sup_{s \in [0,t]} f(...