Non-Rotating BTZ Black Hole Area Spectrum from Quasi-normal Modes

In this paper, using the quasi-normal frequencies for non-rotating BTZ black hole derived by Cardos and Lemos, also via Boher-Sommerfeld quantization for an adiabatic invariant as $I=\\int {dE\\over \\omega(E)}$, which $E$ is a energy of system and $\\omega(E)$ is vibrational frequency, we show this leads to an equally spaced mass spectrum. The result for area of event horizon is as $A_{n}=2\\pi \\sqrt{\\frac{nm \\hbar}{\\Lambda}}$ which in contrast with area spectrum of black hole in higher dimension is not equally spaced.