A linear one in which p and q are equal exemplifies of a martingale, while a periodic radial one may be used to model loss of magnetic confinement of ions in a collisional torus.  An open problem is to find a general formula for the number of finite non-intersecting ones in a plane.  A given non-trivial one always eventually returns to its beginning in one- and two-space, but in 3-space only does so with probability about 0.34, which is known as P?ya's third constant of this kind.  FTP, name this type of Markov chain in which a point takes a certain number of fixed-length "steps" in a probabil
A linear one in which p and q are equal exemplifies of a martingale, while a periodic radial one may be used to model loss of magnetic confinement of ions in a collisional torus.  An open problem is to find a general formula for the number of finite non-intersecting ones in a plane.  A given non-trivial one always eventually returns to its beginning in one- and two-space, but in 3-space only does so with probability about 0.34, which is known as P?ya's third constant of this kind.  FTP, name this type of Markov chain in which a point takes a certain number of fixed-length "steps" in a probabilistic direction and which can be used to model such stochastic processes as Brownian motion and diffusion.
A linear one in which p and q are equal exemplifies of a martingale, while a periodic radial one may be used to model loss of magnetic confinement of ions in a collisional torus.  
random walk (prompt on "Markov chain")