Seminarium:
Teoria prawdopodobieństwa i modelowanie stochastyczne
Osoba referująca:
Georgiy Shevchenko (Kyiv School of Economics)
Data:
czwartek, 30. Styczeń 2025 - 12:15
Sala:
603
Opis:
I will review results regarding a Stratonovich stochastic differential equation
$$
X_t=X_0+\int_0^t |X_s|^\alpha\circ d B_s,
$$
which was introduced in the physical literature under the name ``heterogeneous diffusion process''. It turns out that equation has properties quite different from its Ito counterpart.
Namely, we show that for $\alpha\in(0,1)$ it has infinitely many strong solutions spending zero time at zero. They are given by $X^\theta = \bigl((1-\alpha)B^\theta+(X_0)^{1-\alpha} \bigr)^{1/(1-\alpha)}$, where for $\theta\in(-1,1)$, $B^\theta$ is the $\theta$-skew Brownian motion, and $(x)^{\gamma} = |x|^\gamma \operatorname{sign} x$. It appears that there are no other homogeneous strong Markov solutions to the equation.
To address the non-uniqueness, we consider a perturbation of the equation by a small independent noise. It appears that the solution to such equations converge to the solution of initial equation corresponding to $\theta=0$, i.e. the physically symmetric case.