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We extend our previous definition of quasi-local mass to 2-spheres whose Gauss curvature is negative, and prove its positivity.
A quasi-local mass for 2-spheres with negative Gauss curvature
【摘 要】
：
We extend our previous definition of quasi-local mass to 2-spheres whose Gauss curvature is negative, and prove its positivity.
【出 处】
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Science in China(Series A:Mathematics)
【发表日期】
：
2008年09期
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