Paper detail

Area bound for surfaces in generic gravitational field

We define an attractive gravity probe surface (AGPS) as a compact 2-surface $S_α$ with positive mean curvature $k$ satisfying $r^a D_a k / k^2 \ge α$ (for a constant $α>-1/2$) in the local inverse mean curvature flow, where $r^a D_a k$ is the derivative of $k$ in the outward unit normal direction. For asymptotically flat spaces, any AGPS is proved to satisfy the areal inequality $A_α\le 4π[ ( 3+4α)/(1+2α) ]^2(Gm)^2$, where $A_α$ is the area of $S_α$ and $m$ is the Arnowitt-Deser-Misner (ADM) mass. Equality is realized when the space is isometric to the $t=$constant hypersurface of the Schwarzschild spacetime and $S_α$ is an $r=\mathrm{constant}$ surface with $r^a D_a k / k^2 = α$. We adapt the two methods of the inverse mean curvature flow and the conformal flow. Therefore, our result is applicable to the case where $S_α$ has multiple components. For anti-de Sitter (AdS) spaces, a similar inequality is derived, but the proof is performed only by using the inverse mean curvature flow. We also discuss the cases with asymptotically locally AdS spaces.