Black Hole in the Expanding Universe from Intersecting Branes
  We study physical properties and global structures of a time-dependent,
spherically symmetric solution obtained via the dimensional reduction of
intersecting M-branes. We find that the spacetime describes a maximally charged
black hole which asymptotically tends to the
Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe filled by a stiff matter.
The metric solves the field equations of Einstein-Maxwell-dilaton system, in
which four Abelian gauge fields couple to the dilation with different coupling
constants. The spacetime satisfies the dominant energy condition and is
characterized by two parameters, $Q$ and $\tau$, related to the Maxwell charge
and the relative ratio of black-hole horizon radii, respectively. In spite of
the nontrivial time-dependence of the metric, it turns out that the black hole
event horizon is a Killing horizon. This unexpected symmetry may be ascribed to
the fact that the 11-dimensional (11D) brane configurations are supersymmetric
in the static limit. Finally, combining with laws of trapping horizon, we
discuss the thermodynamic properties of the black hole. It is shown that the
horizon possesses a nonvanishing temperature, contrary to the extremal
Reissner-Nordstr{\o}m (RN) solution.
