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Tracy-Widom law for the extreme eigenvalues of sample correlation matrices

Abstract

Let the sample correlation matrix be W=YYTW=YY^T, where Y=(yij)p,nY=(y_{ij})_{p,n} with yij=xij/j=1nxij2y_{ij}=x_{ij}/\sqrt{\sum_{j=1}^nx_{ij}^2}. We assume {xij:1ip,1jn}\{x_{ij}: 1\leq i\leq p, 1\leq j\leq n\} to be a collection of independent symmetric distributed random variables with sub-exponential tails. Moreover, for any ii, we assume xij,1jnx_{ij}, 1\leq j\leq n to be identically distributed. We assume 0<p<n0<p<n and p/nyp/n\rightarrow y with some y(0,1)y\in(0,1) as p,np,n\rightarrow\infty. In this paper, we provide the Tracy-Widom law (TW1TW_1) for both the largest and smallest eigenvalues of WW. If xijx_{ij} are i.i.d. standard normal, we can derive the TW1TW_1 for both the largest and smallest eigenvalues of the matrix R=RRT\mathcal{R}=RR^T, where R=(rij)p,nR=(r_{ij})_{p,n} with rij=(xijxˉi)/j=1n(xijxˉi)2r_{ij}=(x_{ij}-\bar x_i)/\sqrt{\sum_{j=1}^n(x_{ij}-\bar x_i)^2}, xˉi=n1j=1nxij\bar x_i=n^{-1}\sum_{j=1}^nx_{ij}.

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