13,542 research outputs found
On the Consistent Histories Approach to Quantum Mechanics
We review the consistent histories formulations of quantum mechanics
developed by Griffiths, Omn\`es and Gell-Mann and Hartle, and describe the
classification of consistent sets. We illustrate some general features of
consistent sets by a few simple lemmas and examples. We consider various
interpretations of the formalism, and examine the new problems which arise in
reconstructing the past and predicting the future. It is shown that Omn\`es'
characterisation of true statements --- statements which can be deduced
unconditionally in his interpretation --- is incorrect. We examine critically
Gell-Mann and Hartle's interpretation of the formalism, and in particular their
discussions of communication, prediction and retrodiction, and conclude that
their explanation of the apparent persistence of quasiclassicality relies on
assumptions about an as yet unknown theory of experience. Our overall
conclusion is that the consistent histories approach illustrates the need to
supplement quantum mechanics by some selection principle in order to produce a
fundamental theory capable of unconditional predictions.Comment: Published version, to appear in J. Stat. Phys. in early 1996. The
main arguments and conclusions remain unaltered, but there are significant
revisions from the earlier archive version. These include a new subsection on
interpretations of the formalism, other additions clarifying various
arguments in response to comments, and some minor corrections. (87 pages, TeX
with harvmac.
Quasiclassical Dynamics in a Closed Quantum System
We consider Gell-Mann and Hartle's consistent histories formulation of
quantum cosmology in the interpretation in which one history, chosen randomly
according to the decoherence functional probabilities, is realised from each
consistent set. We show that in this interpretation, if one assumes that an
observed quasiclassical structure will continue to be quasiclassical, one
cannot infer that it will obey the predictions of classical or Copenhagen
quantum mechanics.Comment: Published version, to appear in Phys. Rev. A. Clarificatory remarks
added on interpretations outside the scope of the paper. (TeX with harvmac,
13 pages.
Modelling Private Wealth Accumulation and Spend-down in the Italian Microsimulation Model CAPP_DYN: A Life-Cycle Approach
In microsimulation literature a limited number of
models include a module aimed
at analyzing and projecting the evolution of privat
e wealth over time. However, this issue appears
crucial in order to comprehensively evaluate the li
kely distributional effects of institutional
reforms adopted to cope with population ageing. In
this work we describe the implementation in
the Italian dynamic micro simulation model CAPP_DYN
of a new module in which households\u2019
savings and asset allocation are modelled. In parti
cular, we aim to account for possible
behavioural responses to pension reforms in househo
ld savings. To this end, we rely on an
approximate life cycle structural framework for est
imating saving behaviour, while adopting a
traditional stochastic micro simulation approach fo
r asset allocation. In line with Ando and
Nicoletti Altimari (2004), we emphasize the role of
lifetime economic resources in households\u2019
consumption decisions, yet we further account for i
nternal habit formation and subjective
expectations on pension outcomes in the econometric
stage. In addition, we model
intergenerational transfers of private wealth in a
probabilistic fashio
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