The role of acceleration and locality in the twin paradox

We study the role of acceleration in the twin paradox. From the coordinate transformation that relates an accelerated and an inertial observer we find that, from the point of view of the accelerated observer, the rate of the differential lapses of time depends not only on the relative velocity, but also on the product of the acceleration and the distance between the observ ers. However, this result does not have a direct operational interpretation because an observer at a certain position can measure only physical quanti ties that are defined at the same position. For local measurements, the asy mmetry between the two observers can be attributed to the fact that noniner tial coordinate systems, contrary to inertial coordinate systems, can be co rrectly interpreted only locally.