Poisson germ-grain model 2026-10-14
A Poisson germ-grain model assigns a measurable region to each point of a Poisson point process and takes the union of those regions. A location remains uncovered exactly when no Poisson point has a region containing it, so its coverage probability is determined by the intensity of the corresponding set of germs and marks.
Poisson line process 2026-10-14
Identify an unoriented line not through the origin by , with . A Poisson point process on this parameter space is a random collection of lines. The measure is invariant under rotations and translations; signed coordinates , give the same measure . The number of lines meeting a disk of radius is Poisson with mean .
Randomly shifted lattice point process 2026-10-14
Let have the uniform distribution on and place a point at every , . This is a simple point process, locally finite, and a stationary point process: a translation only changes the phase modulo one, preserving its uniform distribution. For every Borel set , the Tonelli theorem givesIts consecutive points are exactly one unit apart, despite having the same intensity measure as a unit-rate Poisson point process. This is the one-dimensional translated-grid construction.[ref]
Spatial Point Processes and their Applications. Section 2.1, Example 2.3, printed pp. 26-27: randomly translated grids have constant intensity
Every half-open interval of length one contains exactly one point. For and , , each count has the Bernoulli distribution with parameter , andMore generally, an interval of length , with a nonnegative integer and , contains or points with probabilities and . Its count variance is , while a unit-rate Poisson point process has count variance .
For , an intersection inside a disk requires at least two lines to meet that disk. The latter count is Poisson with mean , giving the non-strict bound first. It is strict because two lines with nearby normal angles but separated perpendicular distances can both hit the disk while intersecting outside. Choose two positive-measure parameter boxes forcing this configuration; the event of exactly one line in each box and no other disk-hitting line has positive probability. This also yields a void probability too large to equal that of a Poisson point process with the intersection process's intensity measure.
Place equal masses at points of a homogeneous Poisson point process of intensity on the line, and truncate their signed inverse-power forces symmetrically at radius . For force , with , the characteristic exponent tends to . The cosine integral for a symmetric stable exponent evaluates it as displayed. Thus the weak limit is a symmetric stable distribution. Symmetric truncation is important when the far-field force series is not absolutely summable.
Thinning of a point process 2026-10-14
Thinning removes points from a point process according to a retention rule. Independent retention with probability changes the intensity measure to . For a Poisson point process, the retained and removed point processes are independent Poisson processes.