1,012 research outputs found
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
Comment on Carlo Rovelli's "An argument against the realistic interpretation of the wave function"
Rovelli's argument against the realistic interpretation of quantum states and
in favor of an ontology of quantum events is refuted.Comment: 3 pages; v2: minor correction
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
The role of the observer in the Everett interpretation
The role attributed to the observer in various interpretations of quantum
mechanics as well as in classical statistical mechanics is discussed, with
particular attention being paid to the Everett interpretation. In this context,
the important difference between "quasi-classical" (robust against decoherence)
and "macroscopically given" (rather than being part of a thermodynamic
ensemble) is pointed out.Comment: v2-6: new abstract; further comments and references added; v3:
published; v6: 14 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
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