249,758 research outputs found
Quantum mechanics: Myths and facts
A common understanding of quantum mechanics (QM) among students and practical
users is often plagued by a number of "myths", that is, widely accepted claims
on which there is not really a general consensus among experts in foundations
of QM. These myths include wave-particle duality, time-energy uncertainty
relation, fundamental randomness, the absence of measurement-independent
reality, locality of QM, nonlocality of QM, the existence of well-defined
relativistic QM, the claims that quantum field theory (QFT) solves the problems
of relativistic QM or that QFT is a theory of particles, as well as myths on
black-hole entropy. The fact is that the existence of various theoretical and
interpretational ambiguities underlying these myths does not yet allow us to
accept them as proven facts. I review the main arguments and counterarguments
lying behind these myths and conclude that QM is still a
not-yet-completely-understood theory open to further fundamental research.Comment: 51 pages, pedagogic review, revised, new references, to appear in
Found. Phy
A survey of the ESR model for an objective reinterpretation of quantum mechanics
Most scholars concerned with the foundations of quantum mechanics (QM) think
that contextuality and nonlocality (hence nonobjectivity of physical
properties) are unavoidable features of QM which follow from the mathematical
apparatus of QM. Moreover these features are usually considered as basic in
quantum information processing. Nevertheless they raise still unsolved
problems, as the objectification problem in the quantum theory of measurement.
The extended semantic realism (ESR) model offers a possible way out from these
difficulties by embedding the mathematical formalism of QM into a broader
mathematical formalism and reinterpreting quantum probabilities as conditional
on detection rather than absolute. The embedding allows to recover the formal
apparatus of QM within the ESR model, and the reinterpretation of QM allows to
construct a noncontextual hidden variables theory which justifies the
assumptions introduced in the ESR model and proves its objectivity. According
to the ESR model both linear and nonlinear time evolution occur, depending on
the physical environment, as in QM. In addition, the ESR model, though
objective, implies modified Bell's inequalities that do not conflict with QM,
supplies different mathematical representations of proper and improper
mixtures, provides a general framework in which the local interpretations of
the GHZ experiment obtained by other authors are recovered and explained, and
supports an interpretation of quantum logic which avoids the introduction of
the problematic notion of quantum truth.Comment: 12 page
Remarks on the Qin-Ma Parametrization of Quark Mixing Matrix
Recently, Qin and Ma (QM) have advocated a new Wolfenstein-like
parametrization of the quark mixing matrix based on the triminimal expansion of
the Cabibbo-Kobayashi-Maskawa (CKM) parametrization. The CP-odd phase in the QM
parametrization is around just as that in the CKM parametrization.
We point out that the QM parametrization can be readily obtained from the
Wolfenstein parametrization after appropriate phase redefinition for quark
fields and that the phase in both QM and CKM parametrizations is
related to the unitarity angles , and , namely,
or . We show that both QM and Wolfenstein
parametrizations can be deduced from the CKM and Chau-Keung-Maiani ones. By
deriving the QM parametrization from the Fritzsch-Xing (FX) parametrization of
the quark mixing matrix, we find that the phase of the FX form is in the
vicinity of and hence . We discuss the
seeming discrepancy between the Wolfenstein and QM parametrizations at the high
order of .Comment: 8 pages, a shortened version accepted by PL
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