Kazhdan’s Property (T) via Semidefinite Optimization -- from Wolfram Library Archive

Title

Kazhdan’s Property (T) via Semidefinite Optimization

Authors

Tim Netzer

Andreas Thom

Journal / Anthology

Experimental Mathematics

Year:

2015

Volume:

Issue:

Page range:

371–374

Description

Following an idea of Ozawa, we give a new proof of Kazhdan’s property (T) for SL(3, Z) by showing that 2 − /6 is a Hermitian sum of squares in the group algebra, whereis the unnormalized Laplace operator with respect to the natural generating set. This corresponds to a spectral gap of 1/72 ≈ 0.014 for the associated random-walk operator. The sum-of-squares representation was found numerically by a semidefinite programming algorithm and then turned into an exact symbolic representation, provided in an attached Mathematica file.

Subject

Mathematics

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