Gradient K\'ahler-Ricci solitons with nonnegative orthogonal bisectional curvature

In this paper, we prove that any complete shrinking gradient K\"ahler-Ricci solitons with positive orthogonal bisectional curvature must be compact. We also obtain a classification of the complete shrinking gradient K\"ahler-Ricci solitons with nonnegative orthogonal bisectional curvature.
Comment: to appear in Results in Math.. Xiaolong Li and Lei Ni obtained the same result in their paper "K\"hler-Ricci Shrinkers and Ancient Solutions with Nonnegative Orthogonal Bisectional Curvature" (see arXiv:1903.02615). Then even obtained more interesting results. arXiv admin note: text overlap with arXiv:1906.00412