User:Reginald Maudling
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In mathematics, a determinantal point process is a point process, the probability distribution of which is characterized as a determinant of some function. Such processes arise as important tools in random matrix theory, combinatorics, and physics.
Definition
[edit]Let be a locally compact Polish space and be a Radon measure on . Also, consider a measurable function K:Λ2 → ℂ.
We say that is a determinantal point process on with kernel if it is a simple point process on with joint intensities given by
for every n ≥ 1 and x1, . . . , xn ∈ Λ.[1]
Properties
[edit]Existence
[edit]The following two conditions are necessary and sufficient for the existence of a determinantal random point process with intensities ρk.
- Symmetry: ρk is invariant under action of the symmetric group Sk. Thus:
- Positivity: For any N, and any collection of measurable, bounded functions φk:Λk → ℝ, k = 1,. . . ,N with compact support:
- If
- Then
Uniqueness
[edit]A sufficient condition for the uniqueness of a determinantal random process with joint intensities ρk is
For any bounded Borel A⊆Λ.[2]
Examples
[edit]Gaussian Unitary Ensemble
[edit]The eigenvalues of a random m × m Hermitian matrix drawn from the Gaussian Unitary Ensemble (GUE) form a determinantal point process on with kernel
where is the th oscillator wave function defined by
and is the th Hermite polynomial. [3]
Poissonized Plancherel measure
[edit]The poissonized Plancherel measure on partitions of integers (and therefore on Young diagrams) plays an important role in the study of the longest increasing subsequence of a random permutation. The point process corresponding to a random Young diagram, expressed in modified Frobenius coordinates, is a determinantal point process on ℤ + 1⁄2 with the discrete Bessel kernel, given by:
Where
For J the Bessel function of the first kind, and θ the mean used in poissonization.[4]
This serves as an example of a well-defined determinantal point process with non-Hermitian kernel (although its restriction to the positive and negative semi-axis is Hermitian).[2]
Uniform spanning trees
[edit]Let G be a finite, undirected, connected graph, with edge set E. Define Ie:E → ℓ2(E) as follows: first choose some arbitrary set of orientations for the edges E, and for each resulting, oriented edge e, define Ie to be the projection of a unit flow along e onto the subspace of ℓ2(E) spanned by star flows.[5] Then the uniformly random spanning tree of G is a determinantal point process on E, with kernel
- .[1]
References
[edit]- ^ a b Hough, J. B., Krishnapur, M., Peres, Y., and Virág, B., Zeros of Gaussian analytic functions and determinantal point processes. University Lecture Series, 51. American Mathematical Society, Providence, RI, 2009.
- ^ a b c A. Soshnikov, Determinantal random point fields. Russian Math. Surveys, 2000, 55 (5), 923–975.
- ^ B. Valko. Random matrices, lectures 14--15. Course lecture notes, University of Wisconsin-Madison.
- ^ A. Borodin, A. Okounkov, and G. Olshanski, On asymptotics of Plancherel measures for symmetric groups, available via http://xxx.lanl.gov/abs/math/9905032.
- ^ Lyons, R. with Peres, Y., Probability on Trees and Networks. Cambridge University Press, In preparation. Current version available at http://mypage.iu.edu/~rdlyons/