摘要：Time asymmetry and irreversibility are signal features of our
world. They are the reason of our aging and the basis for our belief that
effects are preceded by causes. These features have many
manifestations called arrows of time. In classical physics, some
of these arrows are described by the increase of entropy or
probability, and others by time-asymmetric boundary conditions of
time-symmetric equations (e.g., Maxwell or Einstein). However,
there is some controversy over whether probability or boundary
conditions are more fundamental. For quantum systems, entropy
increase is usually associated with the effects of an environment
or measurement apparatus on a quantum system and is described by
the von Neumann-Liouville equation. But since the traditional (von
Neumann) axioms of quantum mechanics do not allow time-asymmetric
boundary conditions for the dynamical differential equations
(Schrödinger or Heisenberg), there is no quantum analogue of
the radiation arrow of time. In this paper, we review
consequences of a modification of a fundamental axiom of quantum
mechanics. The new quantum theory is time asymmetric and
accommodates an irreversible time evolution of isolated quantum
systems.
