[Time, the fundamental dimension of our existence, has fascinated artists, philosophers, and scientists of every culture and every century. All of us can remember a moment as a child when time became a personal reality, when we realized what a "year" was, or asked ourselves when "now" happened. Common sense says time moves forward, never backward, from cradle to grave. Nevertheless, Einstein said that time is an illusion. Nature's laws, as he and Newton defined them, describe a timeless, deterministic universe (...) within which we can make predictions with complete certainty. In effect, these great physicists contended that time is reversible and thus meaningless. (shrink)

Two approaches toward the arrow of time for scattering processes have been proposed in rigged Hilbert space quantum mechanics. One, due to Arno Bohm, involves preparations and registrations in laboratory operations and results in two semigroups oriented in the forward direction of time. The other, employed by the Brussels-Austin group, is more general, involving excitations and de-excitations of systems, and apparently results in two semigroups oriented in opposite directions of time. It turns out that these two time arrows can be (...) related to each other via Wigner's extensions of the spacetime symmetry group. Furthermore, their are subtle differences in causality as well as the possibilities for the existence and creation of time-reversed states depending on which time arrow is chosen. (shrink)

Arno Bohm and Ilya Prigogine's Brussels-Austin Group have been working on the quantum mechanical arrow of time and irreversibility in rigged Hilbert space quantum mechanics. A crucial notion in Bohm's approach is the so-called preparation/registration arrow. An analysis of this arrow and its role in Bohm's theory of scattering is given. Similarly, the Brussels-Austin Group uses an excitation/de-excitation arrow for ordering events, which is also analyzed. The relationship between the two approaches is discussed focusing on their semi-group operators and time (...) arrows. Finally a possible realist interpretation of the rigged Hilbert space formulation of quantum mechanics is considered. (shrink)

The author informs us that he would have preferred to title his book Time, the Forgotten Dimension. It is not, he cautions, that scientists fail to consider time or forget to include the term "t" in their equations. But, he insists, from Thales to Einstein and even to Planck and Schroedinger, Western thought has been dominated by the tendency to treat time as a kind of illusion or appearance cloaking a timeless reality. This tendency, taken at the extreme, would treat (...) past, present, and future as if they coexisted and deny to irreversibility, indeterminacy, and creativity the slightest shred of reality. The author, an important contributor to recent "nonequilibrium" thermodynamics, believes that this age-old tendency has finally run its course and needs to be supplemented by a newer and potentially more fruitful tendency to "take time seriously": that is, to study irreversibility and indeterminacy on their own terms, as fundamental features of the real world. The result, he argues, may be the resolution of many heretofore unresolvable problems. (shrink)