6 research outputs found
Does a Computer have an Arrow of Time?
In [Sch05a], it is argued that Boltzmann's intuition, that the psychological
arrow of time is necessarily aligned with the thermodynamic arrow, is correct.
Schulman gives an explicit physical mechanism for this connection, based on the
brain being representable as a computer, together with certain thermodynamic
properties of computational processes. [Haw94] presents similar, if briefer,
arguments. The purpose of this paper is to critically examine the support for
the link between thermodynamics and an arrow of time for computers. The
principal arguments put forward by Schulman and Hawking will be shown to fail.
It will be shown that any computational process that can take place in an
entropy increasing universe, can equally take place in an entropy decreasing
universe. This conclusion does not automatically imply a psychological arrow
can run counter to the thermodynamic arrow. Some alternative possible explana-
tions for the alignment of the two arrows will be briefly discussed.Comment: 31 pages, no figures, publication versio
Detectability, Invasiveness and the Quantum Three Box Paradox
Quantum pre- and post-selection (PPS) paradoxes occur when counterfactual
inferences are made about different measurements that might have been
performed, between two measurements that are actually performed. The 3 box
paradox is the paradigm example of such a paradox, where a ball is placed in
one of three boxes and it is inferred that it would have been found, with
certainty, both in box 1 and in box 2 had either box been opened on their own.
Precisely what is at stake in PPS paradoxes has been unclear, and classical
models have been suggested which are supposed to mimic the essential features
of the problem. We show that the essential difference between the classical and
quantum pre- and post-selection effects lies in the fact that for a quantum PPS
paradox to occur the intervening measurement, had it been performed, would need
to be invasive but non-detectable. This invasiveness is required even for null
result measurements. While some quasi-classical features (such as
non-contextuality and macrorealism) are compatible with PPS paradoxes, it seems
no fully classical model of the 3 box paradox is possible.Comment: 16 pages, no figure
Consequences of temperature fluctuations in observables measured in high energy collisions
We review the consequences of intrinsic, nonstatistical temperature
fluctuations as seen in observables measured in high energy collisions. We do
this from the point of view of nonextensive statistics and Tsallis
distributions. Particular attention is paid to multiplicity fluctuations as a
first consequence of temperature fluctuations, to the equivalence of
temperature and volume fluctuations, to the generalized thermodynamic
fluctuations relations allowing us to compare fluctuations observed in
different parts of phase space, and to the problem of the relation between
Tsallis entropy and Tsallis distributions. We also discuss the possible
influence of conservation laws on these distributions and provide some examples
of how one can get them without considering temperature fluctuations.Comment: Revised version of the invited contribution to The European Physical
Journal A (Hadrons and Nuclei) topical issue about 'Relativistic Hydro- and
Thermodynamics in Nuclear Physics' guest eds. Tamas S. Biro, Gergely G.
Barnafoldi and Peter Va