6,106 research outputs found
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
Entropy inequalities and Bell inequalities for two-qubit systems
Sufficient conditions for (the non-violation of) the Bell-CHSH inequalities
in a mixed state of a two-qubit system are: 1) The linear entropy of the state
is not smaller than 0.5, 2) The sum of the conditional linear entropies is
non-negative, 3) The von Neumann entropy is not smaller than 0.833, 4) The sum
of the conditional von Neumann entropies is not smaller than 0.280.Comment: Errors corrected. See L. Jakobcyk, quant-ph/040908
Transverse Demagnetization Dynamics of a Unitary Fermi Gas
Understanding the quantum dynamics of strongly interacting fermions is a
problem relevant to diverse forms of matter, including high-temperature
superconductors, neutron stars, and quark-gluon plasma. An appealing benchmark
is offered by cold atomic gases in the unitary limit of strong interactions.
Here we study the dynamics of a transversely magnetized unitary Fermi gas in an
inhomogeneous magnetic field. We observe the demagnetization of the gas, caused
by diffusive spin transport. At low temperatures, the diffusion constant
saturates to the conjectured quantum-mechanical lower bound ,
where is the particle mass. The development of pair correlations,
indicating the transformation of the initially non-interacting gas towards a
unitary spin mixture, is observed by measuring Tan's contact parameter.Comment: 8 pages, 6 figures. Accepted versio
Developing sexual competence? Exploring strategies for the provision of effective sexualities and relationships education
School-based sexualities and relationships education (SRE) offers one of the most promising means of improving young people's sexual health through developing 'sexual competence'. In the absence of evidence on whether the term holds the same meanings for young people and adults (e.g. teachers, researchers, policy-makers), the paper explores 'adult' notions of sexual competence as construed in research data and alluded to in UK Government guidance on SRE, then draws on empirical research with young people on factors that affect the contexts, motivations and outcomes of sexual encounters, and therefore have implications for sexual competence. These data from young people also challenge more traditional approaches to sexualities education in highlighting disjunctions between the content of school-based input and their reported sexual experience. The paper concludes by considering the implications of these insights for developing a shared notion of what SRE is trying to achieve and suggestions for recognition in the content and approaches to SRE.</p
Structured personal care of type 2 diabetes:a 19Â year follow-up of the study Diabetes Care in General Practice (DCGP)
Causation, Measurement Relevance and No-conspiracy in EPR
In this paper I assess the adequacy of no-conspiracy conditions employed in
the usual derivations of the Bell inequality in the context of EPR
correlations. First, I look at the EPR correlations from a purely
phenomenological point of view and claim that common cause explanations of
these cannot be ruled out. I argue that an appropriate common cause explanation
requires that no-conspiracy conditions are re-interpreted as mere common
cause-measurement independence conditions. In the right circumstances then,
violations of measurement independence need not entail any kind of conspiracy
(nor backwards in time causation). To the contrary, if measurement operations
in the EPR context are taken to be causally relevant in a specific way to the
experiment outcomes, their explicit causal role provides the grounds for a
common cause explanation of the corresponding correlations.Comment: 20 pages, 1 figur
Violations of local realism by two entangled quNits are stronger than for two qubits
Tests of local realism vs quantum mechanics based on Bell's inequality employ
two entangled qubits. We investigate the general case of two entangled quNits,
i.e. quantum systems defined in an N-dimensional Hilbert space. Via a numerical
linear optimization method we show that violations of local realism are
stronger for two maximally entangled quNits (N=3,4,...,9), than for two qubits
and that they increase with N. The two quNit measurements can be experimentally
realized using entangled photons and unbiased multiport beamsplitters.Comment: 5 pages, 2 pictures, LaTex, two columns; No changes in the result
MGP versus Kochen-Specker condition in hidden variables theories
Hidden variables theories for quantum mechanics are usually assumed to
satisfy the KS condition. The Bell-Kochen-Specker theorem then shows that these
theories are necessarily contextual. But the KS condition can be criticized
from an operational viewpoint, which suggests that a weaker condition (MGP)
should be adopted in place of it. This leads one to introduce a class of hidden
parameters theories in which contextuality can, in principle, be avoided, since
the proofs of the Bell-Kochen-Specker theorem break down. A simple model
recently provided by the author for an objective interpretation of quantum
mechanics can be looked at as a noncontextual hidden parameters theory, which
shows that such theories actually exist.Comment: 10 pages, new updated footnotes and quotation
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