907 research outputs found
Symmetries, superselection rules, and decoherence
We discuss the applicability of the programme of decoherence -- emergence of
approximate classical behaviour through interaction with the environment -- to
cases where it was suggested that the presence of symmetries would lead to
exact superselection rules. For this discussion it is useful to make a
distinction between pure symmetries and redundancies, which results from an
investigation into the constraint equations of the corresponding theories. We
discuss, in particular, superpositions of states with different charges, as
well as with different masses, and suggest how the corresponding interference
terms, although they exist in principle, become inaccessible through
decoherence.Comment: 12 pages, LATEX, Report Freiburg THEP-94/3
Decoherence: Concepts and Examples
We give a pedagogical introduction to the process of decoherence - the
irreversible emergence of classical properties through interaction with the
environment. After discussing the general concepts, we present the following
examples: Localisation of objects, quantum Zeno effect, classicality of fields
and charges in QED, and decoherence in gravity theory. We finally emphasise the
important interpretational features of decoherence.Comment: 24 pages, LATEX, 9 figures, needs macro lamuphys.sty, to appear in
the Proceedings of the 10th Born Symposiu
Quantum Theory and Time Asymmetry
The relation between quantum measurement and thermodynamically irreversible
processes is investigated. The reduction of the state vector is fundamentally
asymmetric in time and shows an observer-relatedness which may explain the
double interpretation of the state vector as a representation of physical
states as well as of information about them. The concept of relevance being
used in all statistical theories of irreversible thermodynamics is shown to be
based on the same observer-relatedness. Quantum theories of irreversible
processes implicitly use an objectivized process of state vector reduction. The
conditions for the reduction are discussed, and I speculate that the final
(subjective) observer system might even be carried by a spacetime point.Comment: Latex version of a paper published in 1979 (with minor revisions), 18
page
Classical and quantum LTB model for the non-marginal case
We extend the classical and quantum treatment of the Lemaitre-Tolman-Bondi
(LTB) model to the non-marginal case (defined by the fact that the shells of
the dust cloud start with a non-vanishing velocity at infinity). We present the
classical canonical formalism and address with particular care the boundary
terms in the action. We give the general relation between dust time and Killing
time. Employing a lattice regularization, we then derive and discuss for
particular factor orderings exact solutions to all quantum constraints.Comment: 23 pages, no figures, typos correcte
EXAMINING THE VALIDITY OF A COMPUTERIZED CHAKRA MEASURING INSTRUMENT: A Pilot Study
Context: The chakra system, a complex network of energy vortexes that receive and process energy within the body, has been espoused for centuries in Asian and other cultures to playa fundamental role in the health of individuals. Many illnesses are thought to originate as blocked energy within the chakra system, and are often thought to be caused by unresolved psychological trauma. Recently, instruments have been created to measure chakra functioning, but no studies to date have attempted to determine their validity in accordance with chakra theory. Objective: To determine the validity of the Inneracrive Aura Video System 5.1 (lAV system) by examining the relationship between self reported psychological symptoms and chakra levels. Method: Sixty-four university students, 42 Americans and 22 Jamaicans, volunteered to complete the Symptom Checklist 90-R (SCL-90-R) and the IAV system measuring chakra level functioning. Results: The expected overall negative relationship between chakra levels and psychological symptoms was confirmed. Pearson product moment correlation analysis revealed significant negative correlations between chakra levels and psychological symptoms. Implications for future chakra research are discussed
SHEARING IRRADIATED URANIUM PLATES
Natural U plates that were irradiated to 600 and 1500 Mwd/t were cut under water by a guillotine-iype shear. Irradiation reduced the force required for shearing to 50% of that required for unirradiated U. Measurements were made of radioactivity released to treated and untreated water in which the cut sections were stored. (auth
Consistency of Semiclassical Gravity
We discuss some subtleties which arise in the semiclassical approximation to
quantum gravity. We show that integrability conditions prevent the existence of
Tomonaga-Schwinger time functions on the space of three-metrics but admit them
on superspace. The concept of semiclassical time is carefully examined. We
point out that central charges in the matter sector spoil the consistency of
the semiclassical approximation unless the full quantum theory of gravity and
matter is anomaly-free. We finally discuss consequences of these considerations
for quantum field theory in flat spacetime, but with arbitrary foliations.Comment: 12 pages, LATEX, Report Freiburg THEP-94/2
Quantum phantom cosmology
We apply the formalism of quantum cosmology to models containing a phantom
field. Three models are discussed explicitly: a toy model, a model with an
exponential phantom potential, and a model with phantom field accompanied by a
negative cosmological constant. In all these cases we calculate the classical
trajectories in configuration space and give solutions to the Wheeler-DeWitt
equation in quantum cosmology. In the cases of the toy model and the model with
exponential potential we are able to solve the Wheeler-DeWitt equation exactly.
For comparison, we also give the corresponding solutions for an ordinary scalar
field. We discuss in particular the behaviour of wave packets in
minisuperspace. For the phantom field these packets disperse in the region that
corresponds to the Big Rip singularity. This thus constitutes a genuine quantum
region at large scales, described by a regular solution of the Wheeler-DeWitt
equation. For the ordinary scalar field, the Big-Bang singularity is avoided.
Some remarks on the arrow of time in phantom models as well as on the relation
of phantom models to loop quantum cosmology are given.Comment: 21 pages, 6 figure
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