41,275 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
Multipartite Nonlocality without Entanglement in Many Dimensions
We present a generic method to construct a product basis exhibiting
Nonlocality Without Entanglement with parties each holding a system of
dimension at least . This basis is generated via a quantum circuit made of
control-Discrete Fourier Transform gates acting on the computational basis. The
simplicity of our quantum circuit allows for an intuitive understanding of this
new type of nonlocality. We also show how this circuit can be used to construct
Unextendible Product Bases and their associated Bound Entangled States. To our
knowledge, this is the first method which, given a general Hilbert space
with , makes it possible to
construct (i) a basis exhibiting Nonlocality Without Entanglement, (ii) an
Unextendible Product Basis, and (iii) a Bound Entangled state.Comment: 8 pages, 4 figure
Berberine for prevention of dementia associated with diabetes and its comorbidities: A systematic review
Background
A growing number of epidemiological studies indicate that metabolic syndrome (MetS) and its associated features play a key role in the development of certain degenerative brain disorders, including Alzheimerâs disease and vascular dementia. Produced by several different medicinal plants, berberine is a bioactive alkaloid with a wide range of pharmacological effects, including antidiabetic effects. However, it is not clear whether berberine could prevent the development of dementia in association with diabetes.
Objective
To give an overview of the therapeutic potential of berberine as a treatment for dementia associated with diabetes.
Search strategy
Database searches A and B were conducted using PubMed and ScienceDirect. In search A, studies on berberineâs antidementia activities were identified using âberberineâ and âdementiaâ as search terms. In search B, recent studies on berberineâs effects on diabetes were surveyed using âberberineâ and âdiabetesâ as search terms.
Inclusion criteria
Clinical and preclinical studies that investigated berberineâs effects associated with MetS and cognitive dysfunction were included.
Data extraction and analysis
Data from studies were extracted by one author, and checked by a second; quality assessments were performed independently by two authors.
Results
In search A, 61 articles were identified, and 22 original research articles were selected. In search B, 458 articles were identified, of which 101 were deemed relevant and selected. Three duplicates were removed, and a total of 120 articles were reviewed for this study. The results demonstrate that berberine exerts beneficial effects directly in the brain: enhancing cholinergic neurotransmission, improving cerebral blood flow, protecting neurons from inflammation, limiting hyperphosphorylation of tau and facilitating ÎČ-amyloid peptide clearance. In addition, evidence is growing that berberine is effective against diabetes and associated disorders, such as atherosclerosis, cardiomyopathy, hypertension, hepatic steatosis, diabetic nephropathy, gut dysbiosis, retinopathy and neuropathy, suggesting indirect benefits for the prevention of dementia.
Conclusion
Berberine could impede the development of dementia via multiple mechanisms: preventing brain damages and enhancing cognition directly in the brain, and indirectly through alleviating risk factors such as metabolic dysfunction, and cardiovascular, kidney and liver diseases. This study provided evidence to support the value of berberine in the prevention of dementia associated with MetS
Local quasi hidden variable modelling and violations of Bell-type inequalities by a multipartite quantum state
We introduce for a general correlation scenario a new simulation model, a
local quasi hidden variable (LqHV) model, where locality and the
measure-theoretic structure inherent to an LHV model are preserved but
positivity of a simulation measure is dropped. We specify a necessary and
sufficient condition for LqHV modelling and, based on this, prove that every
quantum correlation scenario admits an LqHV simulation. Via the LqHV approach,
we construct analogs of Bell-type inequalities for an N-partite quantum state
and find a new analytical upper bound on the maximal violation by an N-partite
quantum state of S_{1}x...xS_{N}-setting Bell-type inequalities - either on
correlation functions or on joint probabilities and for outcomes of an
arbitrary spectral type, discrete or continuous. This general analytical upper
bound is expressed in terms of the new state dilation characteristics
introduced in the present paper and not only traces quantum states admitting an
S_{1}x...xS_{N}-setting LHV description but also leads to the new exact
numerical upper estimates on the maximal Bell violations for concrete N-partite
quantum states used in quantum information processing and for an arbitrary
N-partite quantum state. We, in particular, prove that violation by an
N-partite quantum state of an arbitrary Bell-type inequality (either on
correlation functions or on joint probabilities) for S settings per site cannot
exceed (2S-1)^{N-1} even in case of an infinite dimensional quantum state and
infinitely many outcomes.Comment: Improved, edited versio
Characterizing the nonlocal correlations of particles that never interacted
Quantum systems that have never interacted can become nonlocally correlated
through a process called entanglement swapping. To characterize nonlocality in
this context, we introduce local models where quantum systems that are
initially uncorrelated are described by uncorrelated local variables. While a
pair of maximally entangled qubits prepared in the usual way (i.e., emitted
from a common source) requires a visibility close to 70% to violate a Bell
inequality, we show that an entangled pair generated through entanglement
swapping will already violate a Bell inequality for visibilities as low as 50%
under our assumption.Comment: 5 pages, 2 figure
Comments on the superluminal motion in Cygnus X-3
Following the recent discovery that Cyg X-3 exhibits superluminal motion, the
implications of superluminal expansion and contraction are investigated. We
propose that the effect is due to either a propagating photon pattern or to
outwardly moving shells illuminated by an intense beam of radiation.Comment: accepted for publication in MNRAS; 5 pages, 3 figure
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
Loophole-free Bell's experiment and two-photon all-versus-nothing violation of local realism
We introduce an all-versus-nothing proof of impossibility of
Einstein-Podolsky-Rosen's local elements of reality for two photons entangled
both in polarization and path degrees of freedom, which leads to a Bell's
inequality where the classical bound is 8 and the quantum prediction is 16. A
simple estimation of the detection efficiency required to close the detection
loophole using this proof gives eta > 0.69. This efficiency is lower than that
required for previous proposals.Comment: REVTeX4, 4 page
- âŠ