40,442 research outputs found
Not throwing out the baby with the bathwater: Bell's condition of local causality mathematically 'sharp and clean'
The starting point of the present paper is Bell's notion of local causality
and his own sharpening of it so as to provide for mathematical formalisation.
Starting with Norsen's (2007, 2009) analysis of this formalisation, it is
subjected to a critique that reveals two crucial aspects that have so far not
been properly taken into account. These are (i) the correct understanding of
the notions of sufficiency, completeness and redundancy involved; and (ii) the
fact that the apparatus settings and measurement outcomes have very different
theoretical roles in the candidate theories under study. Both aspects are not
adequately incorporated in the standard formalisation, and we will therefore do
so. The upshot of our analysis is a more detailed, sharp and clean mathematical
expression of the condition of local causality. A preliminary analysis of the
repercussions of our proposal shows that it is able to locate exactly where and
how the notions of locality and causality are involved in formalising Bell's
condition of local causality.Comment: 14 pages. To be published in PSE volume "Explanation, Prediction, and
Confirmation", edited by Dieks, et a
Gravothermal Catastrophe, an Example
This work discusses gravothermal catastrophe in astrophysical systems and
provides an analytic collapse solution which exhibits many of the catastrophe
properties. The system collapses into a trapped surface with outgoing energy
radiated to a future boundary, and provides an example of catastrophic
collapse.Comment: To appear in Phys. Rev.
Axial anomaly of QED in a strong magnetic field and noncommutative anomaly
The Adler-Bell-Jackiw (ABJ) anomaly of a 3+1 dimensional QED is calculated in
the presence of a strong magnetic field. It is shown that in the regime with
the lowest Landau level (LLL) dominance a dimensional reduction from D=4 to D=2
dimensions occurs in the longitudinal sector of the low energy effective field
theory. In the chiral limit, the resulting anomaly is therefore comparable with
the axial anomaly of a two dimensional massless Schwinger model. It is further
shown that the U(1) axial anomaly of QED in a strong magnetic field is closely
related to the ``nonplanar'' axial anomaly of a conventional noncommutative
QED.Comment: 18 pp, no figure. v2: The version accepted to be publidhed in PR
General properties of Nonsignaling Theories
This article identifies a series of properties common to all theories that do
not allow for superluminal signaling and predict the violation of Bell
inequalities. Intrinsic randomness, uncertainty due to the incompatibility of
two observables, monogamy of correlations, impossibility of perfect cloning,
privacy of correlations, bounds in the shareability of some states; all these
phenomena are solely a consequence of the no-signaling principle and
nonlocality. In particular, it is shown that for any distribution, the
properties of (i) nonlocal, (ii) no arbitrarily shareable and (iii) positive
secrecy content are equivalent.Comment: 10 page
Generalised state spaces and non-locality in fault tolerant quantum computing schemes
We develop connections between generalised notions of entanglement and
quantum computational devices where the measurements available are restricted,
either because they are noisy and/or because by design they are only along
Pauli directions. By considering restricted measurements one can (by
considering the dual positive operators) construct single particle state spaces
that are different to the usual quantum state space. This leads to a modified
notion of entanglement that can be very different to the quantum version (for
example, Bell states can become separable). We use this approach to develop
alternative methods of classical simulation that have strong connections to the
study of non-local correlations: we construct noisy quantum computers that
admit operations outside the Clifford set and can generate some forms of
multiparty quantum entanglement, but are otherwise classical in that they can
be efficiently simulated classically and cannot generate non-local statistics.
Although the approach provides new regimes of noisy quantum evolution that can
be efficiently simulated classically, it does not appear to lead to significant
reductions of existing upper bounds to fault tolerance thresholds for common
noise models.Comment: V2: 18 sides, 7 figures. Corrected two erroneous claims and one
erroneous argumen
Randomised positive control trial of NSAID and antimicrobial treatment for calf fever caused by pneumonia
One hundred and fifty-four preweaning calves were followed between May and October 2015. Calves were fitted with continuous monitoring temperature probes (TempVerified FeverTag), programmed so a flashing light emitting diode (LED) light was triggered following six hours of a sustained ear canal temperature of ≥39.7°C. A total of 83 calves (61.9 per cent) developed undifferentiated fever, with a presumptive diagnosis of pneumonia through exclusion of other calf diseases. Once fever was detected, calves were randomly allocated to treatment groups. Calves in group 1 (NSAID) received 2 mg/kg flunixin meglumine (Allevinix, Merial) for three consecutive days and group 2 (antimicrobial) received 6 mg/kg gamithromycin (Zactran, Merial). If fever persisted for 72 hours after the initial treatment, calves were given further treatment (group 1 received antimicrobial and group 2 received NSAID). Calves in group 1 (NSAID) were five times more likely (P=0.002) to require a second treatment (the antimicrobial) after 72 hours to resolve the fever compared with the need to give group 2 (antimicrobial) calves a second treatment (NSAID). This demonstrates the importance of ongoing monitoring and follow-up of calves with respiratory disease. However, of calves with fever in group 1 (NSAID), 25.7 per cent showed resolution following NSAID-only treatment with no detrimental effect on the development of repeated fever or daily live weight gain. This suggests that NSAID alone may be a useful first-line treatment, provided adequate attention is given to ongoing monitoring to identify those cases that require additional antimicrobial treatment
The Bell Theorem as a Special Case of a Theorem of Bass
The theorem of Bell states that certain results of quantum mechanics violate
inequalities that are valid for objective local random variables. We show that
the inequalities of Bell are special cases of theorems found ten years earlier
by Bass and stated in full generality by Vorob'ev. This fact implies precise
necessary and sufficient mathematical conditions for the validity of the Bell
inequalities. We show that these precise conditions differ significantly from
the definition of objective local variable spaces and as an application that
the Bell inequalities may be violated even for objective local random
variables.Comment: 15 pages, 2 figure
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