The Wave Function: It or Bit?

Schroedinger's wave function shows many aspects of a state of incomplete knowledge or information ("bit"): (1) it is usually defined on a space of classical configurations, (2) its generic entanglement is, therefore, analogous to statistical correlations, and (3) it determines probabilities of measurement outcomes. Nonetheless, quantum superpositions (such as represented by a wave function) define individual physical states ("it"). This conceptual dilemma may have its origin in the conventional operational foundation of physical concepts, successful in classical physics, but inappropriate in quantum theory because of the existence of mutually exclusive operations (used for the definition of concepts). In contrast, a hypothetical realism, based on concepts that are justified only by their universal and consistent applicability, favors the wave function as a description of (thus nonlocal) physical reality. The (conceptually local) classical world then appears as an illusion, facilitated by the phenomenon of decoherence, which is consistently explained by the very entanglement that must dynamically arise in a universal wave function.Comment: Several comments added, in particular regarding the role of a "second" quantization and concerning some recently proposed cosmological models. -- 21 pages, Late

Remarks on the Compatibility of Opposite Arrows of Time

I argue that opposite arrows of time, while being logically possible, cannot realistically be assumed to exist during one and the same epoch of this universe.Comment: 10 pages, Latex (2 eps files

Open Questions regarding the Arrow of Time

Conceptual problems regarding the arrow of time in classical physics, quantum physics, cosmology, and quantum gravity are discussed. Particular attention is paid to the dynamical role of the quantum indeterminism, and to various concepts of timelessness.Comment: 14 pages - To appear in The Arrow of Time, Mersini-Houghton, L., and Vaas, R., edts. (Springer). v2: minor changes and added comment

Time in Quantum Theory

The concept of time as used in various applications and interpretations of quantum theory is briefly reviewed.Comment: 6 pages pdf - entry for a forthcoming "Compendium of Quantum Physics". Version 2: minor revision

Roots and Fruits of Decoherence

The concept of decoherence is defined, and discussed in a historical context. This is illustrated by some of its essential consequences which may be relevant for the interpretation of quantum theory. Various aspects of the formalism are also reviewed for this purpose. Contents: 1. Definition of concepts. 2. Roots in nuclear physics. 3. The quantum-to-classical transition. 4. Quantum mechanics without observables. 5. Rules versus tools. 6. Nonlocality. 7. Information loss (paradox?). 8. Dynamics of entanglement. 9. Irreversibility. 10. Concluding remarks.Comment: 19 pages, 3 figures: Talk given at the Seminaire Poincare (Paris, November 2005)- version 2 is a slightly extended and updated version of the proceedings (identical to v1

Toward a Quantum Theory of Observation

The program of a physical concept of information is outlined in the framework of quantum theory. A proposal is made for how to avoid the introduction of axiomatic observables. The conventional (collapse) and the Everett interpretations of quantum theory may in principle lead to different dynamical consequences. Finally, a formal ensemble description not based on a concept of lacking information is discussed.Comment: Latex version of a paper published in 1973 (with corrections), 9 page

Why Bohm's Quantum Theory?

This is a brief reply to Goldstein's article on ``Quantum Theory Without Observers'' in Physics Today. It is pointed out that Bohm's pilot wave theory is successful only because it keeps Schr\"odinger's (exact) wave mechanics unchanged, while the rest of it is observationally meaningless and solely based on classical prejudice.Comment: 5 pages, LaTeX. Several comments added. (To be published in Foundations of Physics Letters

The Problem of Conscious Observation in Quantum Mechanical Description

Epistemological consequences of quantum nonlocality (entanglement) are discussed under the assumption of a universally valid Schr\"odinger equation in the absence of hidden variables. This leads inevitably to a {\it many-minds interpretation}. The recent foundation of quasi-classical neural states in the brain (based on environmental decoherence) permits in principle a formal description of the whole chain of measurement interactions, including the {\it behavior} of conscious observers, without introducing any intermediate classical concepts (for macroscopic "pointer states") or "observables" (for microscopic particle positions and the like) --- thus consistently formalizing Einstein's {\it ganzer langer Weg} from the observed to the observer in quantum mechanical terms.Comment: Published version: new abstract, minor changes, some new references. 14 pages, Late

Time (a-)symmetry in a recollapsing quantum universe

It is argued that Hawking's `greatest mistake' may not have been a mistake at all. According to the canonical quantum theory of gravity for Friedmann type universes, any time arrows of general nature can only be correlated with that of the expansion. For recollapsing universes this seems to be facilitated in part by quantum effects close to their maximum size. Because of the resulting thermodynamical symmetry between expansion and (formal) collapse, black holes must formally become `white' during the collapse phase (while physically only expansion of the universe and black holes can be observed). It is conjectured that the quantum universe remains completely singularity-free in this way (except for the homogeneous singularity) if an appropriate boundary condition for the wave function is able to exclude {\it past} singularities (as is often assumed).Comment: 12 pages, Contribution presented at Mazagon, Spain, October 199

A catalog of optical/near-infrared data on GRB afterglows in the pre-Swift era. I. Light curve information

The present catalog is the result of our attempts to collect all published photometric data on GRB afterglows observed in the pre-Swift era by the end of 2004 in order to gain statistical insight on the phenomenology of GRB afterglows. Part I contains all published data on GRB afterglows in filters we used in Zeh, Klose, & Kann (2005) to create reference light curves and derive light curve parameters (mostly R band, but a few bursts have better data in other colors) including the corresponding references. The catalog includes GCN data as well as data published in refereed journals. No data have been omitted or evaluated in any way (with the exception of a very small number of data that turned out to be not related to an afterglow). Part II will contain color information via the observed light curves in the other photometric bands (Kann et al. 2006, in preparation). Using a simple computer program that can handle strings our catalog is easy to use since all tables are provided in TeX format. For an on-line searchable GCN catalog, we refer to the work done by Quimby et al. (2003). Our catalog includes photometric data on 59 bursts (GRB 970228 - GRB 041006) with altogether 4883 data points. Most data are from GRB 030329 (2759 data points), followed by GRB 021004 (393 data points), while 13 bursts have less than 10 data points. In the case of GRB 030329 we have not included the extensive data list which is on-line provided by Lipkin et al. (2004). (Abridged)Comment: Submitted to astro-ph only. 215 pages, 60 data table