73,347 research outputs found
Time travel paradoxes, path integrals, and the many worlds interpretation of quantum mechanics
We consider two approaches to evading paradoxes in quantum mechanics with
closed timelike curves (CTCs). In a model similar to Politzer's, assuming pure
states and using path integrals, we show that the problems of paradoxes and of
unitarity violation are related; preserving unitarity avoids paradoxes by
modifying the time evolution so that improbable events bewcome certain. Deutsch
has argued, using the density matrix, that paradoxes do not occur in the "many
worlds interpretation". We find that in this approach account must be taken of
the resolution time of the device that detects objects emerging from a wormhole
or other time machine. When this is done one finds that this approach is viable
only if macroscopic objects traversing a wormhole interact with it so strongly
that they are broken into microscopic fragments.Comment: no figure
The Paradoxes of the Interaction-Free Measurement
Interaction-free measurements introduced by Elitzur and Vaidman [Found. Phys.
23, 987 (1993)] allow finding infinitely fragile objects without destroying
them. Paradoxical features of these and related measurements are discussed. The
resolution of the paradoxes in the framework of the Many-Worlds Interpretation
is proposed.Comment: 8 pages, 7 eps figures. Contribution to the "Mysteries and Paradoxes
in Quantum Mechanics", Garda Lake 200
Paradox as invitation to act in problematic change situations
It has been argued that organizational life typically contains paradoxical situations such as efforts to manage change which nonetheless seem to reinforce inertia. Four logical options for coping with paradox have been explicated, three of which seek resolution and one of which ‘keeps the paradox open’. The purpose of this article is to explore the potential for managerial action where the paradox is held open through the use of theory on ‘serious playfulness’. Our argument is that paradoxes, as intrinsic features in organizational life, cannot always be resolved through cognitive processes. What may be possible, however, is that such paradoxes are transformed, or ‘moved on’ through action and as a result the overall change effort need not be stalled by the existence of embedded paradoxes
Infinity
This essay surveys the different types of infinity that occur in pure and applied mathematics, with emphasis on: 1. the contrast between potential infinity and actual infinity; 2. Cantor's distinction between transfinite sets and absolute infinity; 3. the constructivist view of infinite quantifiers and the meaning of constructive proof; 4. the concept of feasibility and the philosophical problems surrounding feasible arithmetic; 5. Zeno's paradoxes and modern paradoxes of physical infinity involving supertasks
Paradoxes of neutrino oscillations
Despite the theory of neutrino oscillations being rather old, some of its
basic issues are still being debated in the literature. We discuss, in the
framework of the wave packet approach, a number of such issues, including the
relevance of the "same energy" and "same momentum" assumptions, the role of
quantum-mechanical uncertainty relations in neutrino oscillations, the
dependence of the production/detection and propagation coherence conditions
that ensure the observability of neutrino oscillations on neutrino energy and
momentum uncertainties, the question of (in)dependence of the oscillation
probabilities on the neutrino production and detection processes, the
applicability limits of the stationary source approximation, and Lorentz
invariance of the oscillation probability. We also develop a novel approach to
calculation of the oscillation probability in the wave packet picture, based on
the summation/integration conventions different from the standard one, which
gives a new insight into the oscillation phenomenology. We discuss a number of
apparently paradoxical features of the theory of neutrino oscillations.Comment: LaTeX, 45 pages, no figures. v2: references adde
No information or horizon paradoxes for Th. Smiths
'Th'e 'S'tatistical 'm'echanician 'i'n 'th'e 's'treet (our Th. Smiths) must
be surprised upon hearing popular versions of some of today's most discussed
paradoxes in astronomy and cosmology. In fact, rather standard reminders of the
meaning of thermal probabilities in statistical mechanics appear to answer the
horizon problem (one of the major motivations for inflation theory) and the
information paradox (related to black hole physics), at least as they are
usually presented. Still the paradoxes point to interesting gaps in our
statistical understanding of (quantum) gravitational effects
The Downs-Thompson paradox in multimodal networks
Users of the transportation networks generally choose their routes in an independent and uncoordinated way in order to minimize their own perceived costs. This non-cooperative behaviour can lead to a suboptimal utilization of the network and, in some situations, increasing the network capacity can make the subutilization even worse. Such phenomenon is described in literature as traffic or network paradoxes. This paper provides a review on two famous network paradoxes, and also introduces a new one
Physics within a quantum reference frame
We investigate the physics of quantum reference frames. Specifically, we
study several simple scenarios involving a small number of quantum particles,
whereby we promote one of these particles to the role of a quantum observer and
ask what is the description of the rest of the system, as seen by this
observer? We highlight the interesting aspects of such questions by presenting
a number of apparent paradoxes. By unravelling these paradoxes we get a better
understanding of the physics of quantum reference frames.Comment: 11 pages, 4 figures. v2: Published versio
The Insidiously Enchanted Forest
Essay Review of B.C. van Fraassen's *Scientific Representation: Paradoxes of Perspective* (2008
- …