Entropy of an Arbitrarily Accelerating Black Hole

The entropy of an arbitrarily accelerating black hole is studied. As the metric is neither axisymmetric nor stationary, its entropy is difficult to calculate. We overcome the difficulty via introduction of a new coordinate system in which ₀₀ is zero at the event horizon's surface r = r_h, and calculate the entropy locally via the improved brick-wall model, that is, the thin film model with the locally thermal equilibrium satisfied. The results confirm that the entropy is proportional to its area both in the stationary space-time and non-stationary one.