Scope of Time and Matter 2007

TIME can be considered the most fundamental quantity in physics for two good reasons: Firstly, the present definition of the unit of time or frequency by atomic clocks exceeds those of all other basic units by orders of magnitudes in precision and is still being improved. Secondly, all other physics quantities and their units can be related to Time and its unit using physical constants only.

In philosophy and the sciences, time together with space has traditionally been seen as a priori condition of perception, as an independent frame or coordinate system where events take place. Yet, the two major legacies of 20th century's physics - the theory of relativity and quantum mechanics - have taught us to view space and time as much more connected with the phenomena they are labeling. The notion of absolute space and time was first abandoned; more recently increasing doubt has been cast on the notion that there are only four space-time dimensions. It was realized that space-time does not merely represent a stage independent of the drama it is showing: MATTER creates space and time. The expansion of the Universe has been discovered and mapped out with more and more reliability showing there was a beginning of space and time in the big bang with the ultimate fate of the Universe - expansion forever or reversal leading to a big crunch - hanging precariously in the balance. There is increasing evidence not only for abundant `dark matter', but even for a cosmological constant possibly being the effect of some `dark energy'. Very recent data strongly suggest that the cosmic microwave background radiation indeed exhibits the tiny inhomogeneities needed to produce the observed grand structures in a universe that underwent inflation. It also has led to the question whether we really understand the dimensionality of the degrees of freedom of the Universe. Do the initial conditions constitute a three- or merely a two-dimensional manifold?

We have become even emboldened to accept the challenge of deriving the baryon number of today's Universe as a dynamically generated observable rather than as an arbitrary initial condition. An essential ingredient in such an undertaking is the fact that microscopic time reversal does not represent a true symmetry of nature. Violation of this symmetry has indeed been observed in particle physics and major resources are being invested for further experimental studies of this fundamental phenomenon.

Violation of macroscopic time reversal invariance has been known for a long time and has been encoded in the 2nd law of thermodynamics. Our new appreciation of time as a complex entity has led us to raise questions and address problems that before would have seen to clearly fall outside scientific jurisdiction. Is the observed arrow of time - and one aspect of it that truly affects all of us on an existential level, namely aging - merely a consequence of what the odds are for various paths? Or is there a cosmic connection meaning there is a fundamental and immediate change when one goes from a big bang to a big crunch universe?

Quantum mechanics has added more texture and even mystery to the notion of time: the usual interpretation combines a continuous time evolution as controlled by differential equations versus the sudden impact of the `so-called' collaps of the wavefunction. The quantum Zeno effect and the EPR correlations challenge our notions of reality and locality. Our understanding is also tested and maybe even challenged by some phenomena observed in tunneling transitions.

What about the "next and ultimate step", namely quantizing space and time itself? Does a space-time lattice represent the real world on the fundamental level rather than being a technical device to overcome some mathematical challenges of computation?

We are witnessing a fascinating development: branches of the physical sciences that apparently had evolved in completely different directions over the centuries suddenly find themselves neighbours again and looking at problems that are intimately connected. One example is provided by high energy physics, which explores the tiniest domains in space and time, and cosmology, which deals with the largest such entities. The relation between violation of microscopic time reversal symmetry and the baryon number of the Universe, between CP violation and the dark matter of the Universe are wondrous examples of such developments.

This conference is basically and fundamentally interdisciplinary and we hope it can help us to get a better grasp of the "Big Picture", where different phenomena are revealing profound connections.

Ikaros Bigi and Martin Faessler