728 research outputs found
Consciousness and the Wigner's friend problem
It is generally agreed that decoherence theory is, if not a complete answer,
at least a great step forward towards a solution of the quantum measurement
problem. It is shown here however that in the cases in which a sentient being
is explicitly assumed to take cognizance of the outcome the reasons we have for
judging this way are not totally consistent, so that the question has to be
considered anew. It is pointed out that the way the Broglie-Bohm model solves
the riddle suggests a possible clue, consisting in assuming that even very
simple systems may have some sort of a proto-consciousness, but that their
``internal states of consciousness'' are not predictive. It is, next, easily
shown that if we imagine the systems get larger, in virtue of decoherence their
internal states of consciousness progressively gain in predictive value. So
that, for macro-systems, they may be identified (in practice) with the
predictive states of consciousness on which we ground our observational
predictions. The possibilities of carrying over this idea to standard quantum
mechanics are then investigated. Conditions of conceptual consistency are
considered and found rather strict, and, finally, two solutions emerge,
differing conceptually very much from one another but in both of which the,
possibly non-predictive, generalized internal states of consciousness play a
crucial role
Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes
Equations for submanifolds, which correspond to embeddings of the
four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are
presented in convenient form in general case. Several specific examples are
considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the
withdrawn preprint arXiv:1012.0320 [gr-qc
Bell inequalities as constraints on unmeasurable correlations
The interpretation of the violation of Bell-Clauser-Horne inequalities is
revisited, in relation with the notion of extension of QM predictions to
unmeasurable correlations. Such extensions are compatible with QM predictions
in many cases, in particular for observables with compatibility relations
described by tree graphs. This implies classical representability of any set of
correlations , , , and the equivalence of the
Bell-Clauser-Horne inequalities to a non void intersection between the ranges
of values for the unmeasurable correlation associated to different
choices for B. The same analysis applies to the Hardy model and to the "perfect
correlations" discussed by Greenberger, Horne, Shimony and Zeilinger. In all
the cases, the dependence of an unmeasurable correlation on a set of variables
allowing for a classical representation is the only basis for arguments about
violations of locality and causality.Comment: Some modifications have been done in order to improve clarity of
presentation and comparison with other approache
Reality, measurement and locality in Quantum Field Theory
It is currently believed that the local causality of Quantum Field Theory
(QFT) is destroyed by the measurement process. This belief is also based on the
Einstein-Podolsky-Rosen (EPR) paradox and on the so-called Bell's theorem, that
are thought to prove the existence of a mysterious, instantaneous action
between distant measurements. However, I have shown recently that the EPR
argument is removed, in an interpretation-independent way, by taking into
account the fact that the Standard Model of Particle Physics prevents the
production of entangled states with a definite number of particles. This result
is used here to argue in favor of a statistical interpretation of QFT and to
show that it allows for a full reconciliation with locality and causality.
Within such an interpretation, as Ballentine and Jarret pointed out long ago,
Bell's theorem does not demonstrate any nonlocality.Comment: 15 pages. Published versio
Relational EPR
We study the EPR-type correlations from the perspective of the relational
interpretation of quantum mechanics. We argue that these correlations do not
entail any form of 'non-locality', when viewed in the context of this
interpretation. The abandonment of strict Einstein realism implied by the
relational stance permits to reconcile quantum mechanics, completeness,
(operationally defined) separability, and locality.Comment: Revised, published versio
A Derivation of Three-Dimensional Inertial Transformations
The derivation of the transformations between inertial frames made by
Mansouri and Sexl is generalised to three dimensions for an arbitrary direction
of the velocity. Assuming lenght contraction and time dilation to have their
relativistic values, a set of transformations kinematically equivalent to
special relativity is obtained. The ``clock hypothesis'' allows the derivation
to be extended to accelerated systems. A theory of inertial transformations
maintaining an absolute simultaneity is shown to be the only one logically
consistent with accelerated movements. Algebraic properties of these
transformations are discussed. Keywords: special relativity, synchronization,
one-way velocity of light, ether, clock hypothesis.Comment: 16 pages (A5), Latex, one figure, to be published in Found. Phys.
Lett. (1997
Quantum Locality
It is argued that while quantum mechanics contains nonlocal or entangled
states, the instantaneous or nonlocal influences sometimes thought to be
present due to violations of Bell inequalities in fact arise from mistaken
attempts to apply classical concepts and introduce probabilities in a manner
inconsistent with the Hilbert space structure of standard quantum mechanics.
Instead, Einstein locality is a valid quantum principle: objective properties
of individual quantum systems do not change when something is done to another
noninteracting system. There is no reason to suspect any conflict between
quantum theory and special relativity.Comment: Introduction has been revised, references added, minor corrections
elsewhere. To appear in Foundations of Physic
Effects of dietary vegetable oil on atlantic salmon hepatocyte fatty acid desaturation and liver fatty acid compositions
Fatty acyl desaturase activities, involved in the conversion of the C18 EFA, 18:2n-6 and 18:3n-3, to the highly unsaturated fatty acids (HUFA) 20:4n-6, 20:5n-3 and 22:6n-3, are known to be under nutritional regulation. Specifically, the activity of the desaturation/elongation pathway is depressed when animals, including fish, are fed fish oils rich in n-3HUFA compared to animals fed vegetable oils rich in C18 EFA. The primary aims of the present study were a) to establish the relative importance of product inhibition (n-3HUFA) versus increased substrate concentration (C18 EFA) and, b) to determine whether 18:2n-6 and 18:3n-3 differ in their effects, on the hepatic fatty acyl desaturation/elongation pathway in Atlantic salmon (Salmo salar). Smolts were fed ten experimental diets containing blends of two vegetable oils, linseed (LO) and rapeseed oil (RO), and fish oil (FO) in a triangular mixture design for 50 weeks. Fish were sampled after 32 and 50 weeks, lipid and fatty acid composition of liver determined, fatty acyl desaturation/elongation activity estimated in hepatocytes using [1-14C]18:3n-3 as substrate, and the data subjected to regression analyses. Dietary 18:2n-6 was positively correlated, and n-3HUFA negatively correlated, with lipid content of liver. Dietary 20:5n-3 and 22:6n-3 were positively correlated with liver fatty acids with a slope greater than unity suggesting relative retention and deposition of these HUFA. In contrast, dietary 18:2n-6 and 18:3n-3 were positively correlated with liver fatty acids with a slope of less than unity suggesting metabolism via β-oxidation and/or desaturation/elongation. Consistent with this, fatty acyl desaturation/elongation in hepatocytes was significantly increased by feeding diets containing vegetable oils. Dietary 20:5n-3 and 22:6n-3 levels were negatively correlated with hepatocyte fatty acyl desaturation. At 32 weeks, 18:2n-6 but not 18:3n-3, was positively correlated with hepatocyte fatty acyl desaturation activity whereas the reverse was true at 50 weeks. The data indicate that both feedback inhibition through increased n-3HUFA and decreased C18 fatty acyl substrate concentration are probably important in determining hepatocyte fatty acyl desaturation activities, and that 18:2n-6 and 18:3n-3 may differ in their effects on this pathway
"Dark energy" in the Local Void
The unexpected discovery of the accelerated cosmic expansion in 1998 has
filled the Universe with the embarrassing presence of an unidentified "dark
energy", or cosmological constant, devoid of any physical meaning. While this
standard cosmology seems to work well at the global level, improved knowledge
of the kinematics and other properties of our extragalactic neighborhood
indicates the need for a better theory. We investigate whether the recently
suggested repulsive-gravity scenario can account for some of the features that
are unexplained by the standard model. Through simple dynamical considerations,
we find that the Local Void could host an amount of antimatter
() roughly equivalent to the mass of a typical
supercluster, thus restoring the matter-antimatter symmetry. The antigravity
field produced by this "dark repulsor" can explain the anomalous motion of the
Local Sheet away from the Local Void, as well as several other properties of
nearby galaxies that seem to require void evacuation and structure formation
much faster than expected from the standard model. At the global cosmological
level, gravitational repulsion from antimatter hidden in voids can provide more
than enough potential energy to drive both the cosmic expansion and its
acceleration, with no need for an initial "explosion" and dark energy.
Moreover, the discrete distribution of these dark repulsors, in contrast to the
uniformly permeating dark energy, can also explain dark flows and other
recently observed excessive inhomogeneities and anisotropies of the Universe.Comment: 6 pages, accepted as a Letter to the Editor by Astrophysics and Space
Scienc
Statistics of the gravitational force in various dimensions of space: from Gaussian to Levy laws
We discuss the distribution of the gravitational force created by a
Poissonian distribution of field sources (stars, galaxies,...) in different
dimensions of space d. In d=3, it is given by a Levy law called the Holtsmark
distribution. It presents an algebraic tail for large fluctuations due to the
contribution of the nearest neighbor. In d=2, it is given by a marginal
Gaussian distribution intermediate between Gaussian and Levy laws. In d=1, it
is exactly given by the Bernouilli distribution (for any particle number N)
which becomes Gaussian for N>>1. Therefore, the dimension d=2 is critical
regarding the statistics of the gravitational force. We generalize these
results for inhomogeneous systems with arbitrary power-law density profile and
arbitrary power-law force in a d-dimensional universe
- …