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Publications (6 of 6) Show all publications
Courteaut, K. & Johansson, K. (2025). Partition function for the 2d Coulomb gas on a Jordan curve. Annales Fennici Mathematici, 50(1), 109-144
Open this publication in new window or tab >>Partition function for the 2d Coulomb gas on a Jordan curve
2025 (English)In: Annales Fennici Mathematici, ISSN 2737-0690, E-ISSN 2737-114X, Vol. 50, no 1, p. 109-144Article in journal (Refereed) Published
Abstract [en]

We prove an asymptotic formula for the partition function of a 2d Coulomb gas at inverse temperature beta > 0, confined to lie on a Jordan curve. The partition function can include a linear statistic. The asymptotic formula involves a Fredholm determinant related to the Loewner energy of the curve, and also an expression involving the sampling function, the exterior conformal map for the curve and the Grunsky operator. The asymptotic formula also gives a central limit theorem for linear statistics of the particles in the gas.

Place, publisher, year, edition, pages
Finnish Mathematical Society, 2025
Keywords
Log-gas, Coulomb gas, Jordan curve, partition function, free energy, Central Limit Theorem, global fluctuations, linear statistic
National Category
Mathematical sciences
Identifiers
urn:nbn:se:kth:diva-361871 (URN)10.54330/afm.159822 (DOI)001445841500003 ()2-s2.0-105001531220 (Scopus ID)
Note

QC 20250401

Available from: 2025-04-01 Created: 2025-04-01 Last updated: 2026-03-30Bibliographically approved
Courteaut, K., Johansson, K. & Lambert, G. (2024). From Berry–Esseen to super-exponential. Electronic Journal of Probability, 29, Article ID 11.
Open this publication in new window or tab >>From Berry–Esseen to super-exponential
2024 (English)In: Electronic Journal of Probability, E-ISSN 1083-6489, Vol. 29, article id 11Article in journal (Refereed) Published
Abstract [en]

For any integer m < n, where m can depend on n, we study the rate of convergence (Formula Presented) to its limiting Gaussian as n → ∞ for orthogonal, unitary and symplectic Haar distributed random matrices U of size n. In the unitary case, we prove that the total variation distance is less than (Formula Presented) times a constant. This result interpolates between the super-exponential bound obtained for fixed m and the 1/n bound coming from the Berry–Esseen theorem applicable when m ≥ n by a result of Rains. We obtain analogous results for the orthogonal and symplectic groups. In these cases, our total variation upper bound takes the form (Formula Presented) times a constant and the result holds provided n > 2m. For m = 1, we obtain complementary lower bounds and precise asymptotics for the L2-distances as n → ∞, which show how sharp our results are.

Place, publisher, year, edition, pages
Institute of Mathematical Statistics, 2024
Keywords
classical compact groups, Haar measure, Hankel determinants, rate of convergence, Toeplitz determinants
National Category
Mathematical Analysis
Identifiers
urn:nbn:se:kth:diva-344004 (URN)10.1214/23-EJP1068 (DOI)001165378300001 ()2-s2.0-85185324572 (Scopus ID)
Note

QC 20240229

Available from: 2024-02-28 Created: 2024-02-28 Last updated: 2025-12-05Bibliographically approved
Courteaut, K. & Johansson, K. (2024). Multivariate normal approximation for traces of orthogonal and symplectic matrices. Annales de l'I.H.P. Probabilites et statistiques, 60(1), 312-342
Open this publication in new window or tab >>Multivariate normal approximation for traces of orthogonal and symplectic matrices
2024 (English)In: Annales de l'I.H.P. Probabilites et statistiques, ISSN 0246-0203, E-ISSN 1778-7017, Vol. 60, no 1, p. 312-342Article in journal (Refereed) Published
Abstract [en]

We show that the distance in total variation between (Tr U, √12 Tr U2, . . ., √m Tr Um) and a real Gaussian vector, where 1 U is a Haar distributed orthogonal or symplectic matrix of size 2n or 2n + 1, is bounded by 「 (2 mn + 1)− 12 times a correction. The correction term is explicit and holds for all n ≥ m4, for m sufficiently large. For n ≥ m3 we obtain the bound (mn)−c √ mn with an explicit constant c. Our method of proof is based on an identity of Toeplitz + Hankel determinants due to Basor and Ehrhardt, see (Oper. Matrices 3 (2009) 167–86), which is also used to compute the joint moments of the traces.

Place, publisher, year, edition, pages
Institute of Mathematical Statistics, 2024
Keywords
Hankel determinants, Multivariate Gaussian approximation, Toeplitz determinants
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-344577 (URN)10.1214/22-AIHP1332 (DOI)001177499400007 ()2-s2.0-85186940639 (Scopus ID)
Note

QC 20240321

Available from: 2024-03-20 Created: 2024-03-20 Last updated: 2024-04-26Bibliographically approved
Courteaut, K., Johansson, K. & Lambert, G.From Berry-Esseen to super-exponential.
Open this publication in new window or tab >>From Berry-Esseen to super-exponential
(English)Manuscript (preprint) (Other academic)
Abstract [en]

For any integer $m<n$, where $m$ can depend on $n$, we study the rate of convergence of $\frac{1}{\sqrt{m}}\tr \mathbf{U}^m$ to its limiting Gaussian as $n\to\infty$ for orthogonal, unitary and symplectic Haar distributed random matrices $\mathbf{U}$ of size $n$. In the unitary case, we prove that the total variation distance is less than $\Gamma(\floor{n/m}+2)^{-1}m^{-\floor{n/m}}\floor{n/m}^{1/4}\sqrt{\log n}$ times a constant. This result interpolates between the super-exponential bound obtained for fixed $m$ and the $1/n$ bound coming from the Berry-Esseen theorem applicable when $m\ge n$ by a result of Rains. We obtain analogous results for the orthogonal and symplectic groups. In these cases, our total variation upper bound takes the form $\Gamma(2\floor{n/m}+1)^{-1/2}m^{-\floor{n/m}+1}(\log n)^{1/4}$ times a constant and the result holds provided $n \geq 2m$. For $m=1$, we obtain complementary lower bounds and precise asymptotics for the $L^2$-distances as $n\to\infty$, which show how sharp our results are. 

National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:kth:diva-326109 (URN)
Note

QCR 20230426

Available from: 2023-04-24 Created: 2023-04-24 Last updated: 2023-05-04Bibliographically approved
Courteaut, K. & Johansson, K. Multivariate normal approximation for traces of orthogonal and symplectic matrices.
Open this publication in new window or tab >>Multivariate normal approximation for traces of orthogonal and symplectic matrices
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We show that the distance in total variation between $(\tr U, \frac{1}{\sqrt{2}}\tr U^2, \cdots, \frac{1}{\sqrt{m}}\tr U^m)$ and a real Gaussian vector, where $U$ is a Haar distributed orthogonal or symplectic matrix of size $2n$ or $2n+1$, is bounded by $\Gamma(2\frac{n}{m}+1)^{-\frac{1}{2}}$ times a correction. The correction term is explicit and holds for all $n\geq m^4$, for $m$ sufficiently large. For $n\geq m^3$ we obtain the bound $(\frac{n}{m})^{-c\sqrt{\frac{n}{m}}}$ with an explicit constant $c$. Our method of proof is based on an identity of Toeplitz+Hankel determinants due to Basor and Ehrhardt, see \cite{BE}, which is also used to compute the joint moments of the traces.

National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:kth:diva-326107 (URN)
Note

QC 20230425

Available from: 2023-04-24 Created: 2023-04-24 Last updated: 2023-05-04Bibliographically approved
Courteaut, K. & Johansson, K.Partition function for the 2d Coulomb gas on a Jordan curve.
Open this publication in new window or tab >>Partition function for the 2d Coulomb gas on a Jordan curve
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We prove an asymptotic formula for the partition function of a 2d Coulomb gas at inverse temperature $\beta>0$ confined to lie on a Jordan curve. This also gives a central limit theorem for a linear statistic of the particles in the gas.  We obtain different expressions for the asymptotic mean and variance which involve either the exterior conformal mapping of the curve or the Grunsky operator.

National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:kth:diva-326110 (URN)
Note

QCR 20230426

Available from: 2023-04-24 Created: 2023-04-24 Last updated: 2023-05-04Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1193-8355

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