Tracy–Widom distribution
The Tracy–Widom distribution is a
In practical terms, Tracy–Widom is the crossover function between the two phases of weakly versus strongly coupled components in a system.[1] It also appears in the distribution of the length of the
The distribution is of particular interest in multivariate statistics.[6] For a discussion of the universality of , , see Deift (2007). For an application of to inferring population structure from genetic data see Patterson, Price & Reich (2006). In 2017 it was proved that the distribution F is not infinitely divisible.[7]
Definition as a law of large numbers
Let denote the cumulative distribution function of the Tracy–Widom distribution with given . It can be defined as a law of large numbers, similar to the central limit theorem.
There are typically three Tracy–Widom distributions, , with . They correspond to the three gaussian ensembles: orthogonal (), unitary (), and symplectic ().
In general, consider a gaussian ensemble with beta value , with its diagonal entries having variance 1, and off-diagonal entries having variance , and let be probability that an matrix sampled from the ensemble have maximal eigenvalue , then define[8]
For example:[10]
where the matrix is sampled from the gaussian unitary ensemble with off-diagonal variance .
The definition of the Tracy–Widom distributions may be extended to all (Slide 56 in Edelman (2003), Ramírez, Rider & Virág (2006)).
One may naturally ask for the limit distribution of second-largest eigenvalues, third-largest eigenvalues, etc. They are known.[11][8]
Functional forms
Fredholm determinant
can be given as the Fredholm determinant
of the kernel ("Airy kernel") on square integrable functions on the half line , given in terms of Airy functions Ai by
Painlevé transcendents
can also be given as an integral
in terms of a solution
with boundary condition This function is a
Other distributions are also expressible in terms of the same :[10]
Functional equations
Define
Occurrences
Other than in random matrix theory, the Tracy–Widom distributions occur in many other probability problems.[12]
Let be the length of the longest increasing subsequence in a random permutation sampled uniformly from , the permutation group on n elements. Then the cumulative distribution function of converges to .[13]
Asymptotics
Probability density function
Let be the probability density function for the distribution, then[12]
At the limit, a more precise expression is (equation 49 [12])
Cumulative distribution function
At the limit,[14]
This allows derivation of behavior of . For example,
Painlevé transcendent
The Painlevé transcendent has asymptotic expansion at (equation 4.1 of [15])
Numerics
Numerical techniques for obtaining numerical solutions to the Painlevé equations of the types II and V, and numerically evaluating eigenvalue distributions of random matrices in the beta-ensembles were first presented by Edelman & Persson (2005) using MATLAB. These approximation techniques were further analytically justified in Bejan (2005) and used to provide numerical evaluation of Painlevé II and Tracy–Widom distributions (for ) in S-PLUS. These distributions have been tabulated in Bejan (2005) to four significant digits for values of the argument in increments of 0.01; a statistical table for p-values was also given in this work. Bornemann (2010) gave accurate and fast algorithms for the numerical evaluation of and the density functions for . These algorithms can be used to compute numerically the
Mean | Variance | Skewness | Excess kurtosis | |
---|---|---|---|---|
1 | −1.2065335745820 | 1.607781034581 | 0.29346452408 | 0.1652429384 |
2 | −1.771086807411 | 0.8131947928329 | 0.224084203610 | 0.0934480876 |
4 | −2.306884893241 | 0.5177237207726 | 0.16550949435 | 0.0491951565 |
Functions for working with the Tracy–Widom laws are also presented in the R package 'RMTstat' by Johnstone et al. (2009) and MATLAB package 'RMLab' by Dieng (2006).
For a simple approximation based on a shifted gamma distribution see Chiani (2014).
Shen & Serkh (2022) developed a spectral algorithm for the eigendecomposition of the integral operator , which can be used to rapidly evaluate Tracy–Widom distributions, or, more generally, the distributions of the th largest level at the soft edge scaling limit of Gaussian ensembles, to machine accuracy.
Tracy-Widom and KPZ universality
The Tracy-Widom distribution appears as a limit distribution in the universality class of the
See also
Footnotes
- ^ Mysterious Statistical Law May Finally Have an Explanation, wired.com 2014-10-27
- ^ Baik, Deift & Johansson (1999).
- ^ Sasamoto & Spohn (2010)
- ^ Johansson (2000); Tracy & Widom (2009)).
- ^ Majumdar & Nechaev (2005).
- ^ Johnstone (2007, 2008, 2009).
- ^ Domínguez-Molina (2017).
- ^ ISBN 978-90-481-2810-5.
- ISSN 0550-3213.
- ^ a b Tracy & Widom (1996).
- ISSN 1687-0247.
- ^ S2CID 119122520.
- ^ Baik, Deift & Johansson 1999
- S2CID 16324715.
- S2CID 13912236.
- ISBN 978-0-387-98931-0.
- S2CID 237903590.
- .
- ^ called "Hastings–McLeod solution". Published by Hastings, S.P., McLeod, J.B.: A boundary value problem associated with the second Painlevé transcendent and the Korteweg-de Vries equation. Arch. Ration. Mech. Anal. 73, 31–51 (1980)
References
- Baik, J.; Deift, P.; Johansson, K. (1999), "On the distribution of the length of the longest increasing subsequence of random permutations", MR 1682248.
- Bornemann, F. (2010), "On the numerical evaluation of distributions in random matrix theory: A review with an invitation to experimental mathematics", Markov Processes and Related Fields, 16 (4): 803–866, Bibcode:2009arXiv0904.1581B.
- Chiani, M. (2014), "Distribution of the largest eigenvalue for real Wishart and Gaussian random matrices and a simple approximation for the Tracy–Widom distribution", S2CID 15889291.
- Sasamoto, Tomohiro; Spohn, Herbert (2010), "One-Dimensional Kardar-Parisi-Zhang Equation: An Exact Solution and its Universality", Physical Review Letters, 104 (23): 230602, S2CID 34945972
- Deift, P. (2007), "Universality for mathematical and physical systems" (PDF), S2CID 14133017.
- Dieng, Momar (2006), RMLab, a MATLAB package for computing Tracy-Widom distributions and simulating random matrices.
- Domínguez-Molina, J.Armando (2017), "The Tracy-Widom distribution is not infinitely divisible", Statistics & Probability Letters, 213 (1): 56–60, S2CID 119676736.
- Johansson, K. (2000), "Shape fluctuations and random matrices", S2CID 16291076.
- Johansson, K. (2002), "Toeplitz determinants, random growth and determinantal processes" (PDF), Proc. MR 1957518.
- Johnstone, I. M. (2007), "High dimensional statistical inference and random matrices" (PDF), S2CID 88524958.
- Johnstone, I. M. (2008), "Multivariate analysis and Jacobi ensembles: largest eigenvalue, Tracy–Widom limits and rates of convergence", PMID 20157626.
- Johnstone, I. M. (2009), "Approximate null distribution of the largest root in multivariate analysis", PMID 20526465.
- Majumdar, Satya N.; Nechaev, Sergei (2005), "Exact asymptotic results for the Bernoulli matching model of sequence alignment", Physical Review E, 72 (2): 020901, 4, S2CID 11390762.
- Patterson, N.; Price, A. L.; PMID 17194218.
- Prähofer, M.; Spohn, H. (2000), "Universal distributions for growing processes in 1+1 dimensions and random matrices", S2CID 20814566.
- Shen, Z.; Serkh, K. (2022), "On the evaluation of the eigendecomposition of the Airy integral operator", S2CID 233407802.
- Takeuchi, K. A.; Sano, M. (2010), "Universal fluctuations of growing interfaces: Evidence in turbulent liquid crystals", S2CID 19315093
- Takeuchi, K. A.; Sano, M.; Sasamoto, T.; Spohn, H. (2011), "Growing interfaces uncover universal fluctuations behind scale invariance", PMID 22355553
- S2CID 119690132.
- S2CID 13912236.
- S2CID 17398688
- MR 1989209.
- S2CID 14730756.
Further reading
- Bejan, Andrei Iu. (2005), Largest eigenvalues and sample covariance matrices. Tracy–Widom and Painleve II: Computational aspects and realization in S-Plus with applications (PDF), M.Sc. dissertation, Department of Statistics, The University of Warwick.
- Edelman, A.; Persson, P.-O. (2005), Numerical Methods for Eigenvalue Distributions of Random Matrices, Bibcode:2005math.ph...1068E.
- Edelman, A. (2003), Stochastic Differential Equations and Random Matrices, SIAM Applied Linear Algebra.
- Ramírez, J. A.; Rider, B.; Virág, B. (2006), "Beta ensembles, stochastic Airy spectrum, and a diffusion", Journal of the American Mathematical Society, 24 (4): 919–944, S2CID 10226881.
External links
- Kuijlaars, Universality of distribution functions in random matrix theory (PDF).
- Tracy, C. A.; Widom, H., The distributions of random matrix theory and their applications (PDF).
- Johnstone, Iain; Ma, Zongming; Perry, Patrick; Shahram, Morteza (2009), Package 'RMTstat' (PDF).
- At the Far Ends of a New Universal Law, Quanta Magazine