49,557 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
Anomalies, Chern-Simons Terms and Chiral Delocalization in Extra Dimensions
Gauge invariant topological interactions, such as the D=5 Chern-Simons terms,
are required in models in extra dimensions that split anomaly free
representations. The Chern-Simons term is necessary to maintain the overall
anomaly cancellations of the theory, but it can have significant, observable,
physical effects. The CS-term locks the KK-mode parity to the parity of
space-time, leaving a single parity symmetry. It leads to new processes amongst
KK-modes, eg, the decay of a KK-mode to a 2-body final state of KK-modes. A
formalism for the effective interaction amongst KK-modes is constructed, and
the decay of a KK-mode to KK-mode plus zero mode is analyzed as an example. We
elaborate the general KK-mode current and anomaly structure of these theories.
This includes a detailed study of the triangle diagrams and the associated
``consistent anomalies'' for Weyl spinors on the boundary branes. We also
develop the non-abelian formalism. We illustrate this by showing in a simple
way how a D=5 Yang-Mills ``quark flavor'' symmetry leads to the D=4 chiral
lagrangian of mesons and the quantized Wess-Zumino-Witten term.Comment: 51 pages, 3 figures; Corrected typos, amplified discussio
Bell's theorem as a signature of nonlocality: a classical counterexample
For a system composed of two particles Bell's theorem asserts that averages
of physical quantities determined from local variables must conform to a family
of inequalities. In this work we show that a classical model containing a local
probabilistic interaction in the measurement process can lead to a violation of
the Bell inequalities. We first introduce two-particle phase-space
distributions in classical mechanics constructed to be the analogs of quantum
mechanical angular momentum eigenstates. These distributions are then employed
in four schemes characterized by different types of detectors measuring the
angular momenta. When the model includes an interaction between the detector
and the measured particle leading to ensemble dependencies, the relevant Bell
inequalities are violated if total angular momentum is required to be
conserved. The violation is explained by identifying assumptions made in the
derivation of Bell's theorem that are not fulfilled by the model. These
assumptions will be argued to be too restrictive to see in the violation of the
Bell inequalities a faithful signature of nonlocality.Comment: Extended manuscript. Significant change
A Tighter Test of Local Lorentz Invariance using PSR J2317+1439
Gravity being a long-range force, one might {\it a priori} expect the
Universe's global matter distribution to select a preferred rest frame for
local gravitational physics. The phenomenology of preferred-frame effects, in
the strong-gravitational field context of binary pulsars, is described by two
parameters and . These parameters vanish
identically in general relativity, and reduce, in the weak-field limit, to the
two parametrized post-Newtonian (PPN) parameters and .
We derive a limit of (90\%~C.L.) using
the very low eccentricity binary pulsar PSR J2317+1439, improving by a factor
of 3 on previous limits.Comment: 4 pages, LaTeX, requires aaspp4.sty and flushrt.sty, submitted to Ap
Thermal and Magnetic Quantum Discord in Heisenberg models
We investigate how the quantum correlations (quantum discord) of a two-qubit
one dimensional XYZ Heisenberg chain in thermal equilibrium depends on the
temperature (T) of the bath and also on an external magnetic field B. We show
that the behavior of the thermal quantum discord (QD) differs in many
unexpected ways from the thermal entanglement. For example, we show situations
where QD increases with T when entanglement decreases, cases where QD increases
with T even in regions with zero entanglement, and that QD signals a quantum
phase transition even at finite T. We also show that by properly tuning B or
the interaction between the qubits we get non-zero QD for any T and we present
a new effect not seen for entanglement, the regrowth of thermal QD.Comment: 4 pages, 5 figures, RevTex, double column; v2: published versio
Loophole-free Bell test based on local precertification of photon's presence
A loophole-free violation of Bell inequalities is of fundamental importance
for demonstrating quantum nonlocality and long-distance device-independent
secure communication. However, transmission losses represent a fundamental
limitation for photonic loophole-free Bell tests. A local precertification of
the presence of the photons immediately before the local measurements may solve
this problem. We show that local precertification is feasible by integrating
three current technologies: (i) enhanced single-photon down-conversion to
locally create a flag photon, (ii) nanowire-based superconducting single-photon
detectors for a fast flag detection, and (iii) superconducting transition-edge
sensors to close the detection loophole. We carry out a precise space-time
analysis of the proposed scheme, showing its viability and feasibility.Comment: REVTeX4, 7 Pages, 1 figur
T-Parity Violation by Anomalies
Little Higgs theories often rely on an internal parity ("T-parity'') to
suppress non-standard electroweak effects or to provide a dark matter
candidate. We show that such a symmetry is generally broken by anomalies, as
described by the Wess-Zumino-Witten term. We study a simple SU(3) x SU(3)/SU(3)
Little Higgs scheme where we obtain a minimal form for the topological
interactions of a single Higgs field. The results apply to more general models,
including [SU(3) x SU(3)/SU(3)]^4, SU(5)/SO(5), and SU(6)/Sp(6).Comment: 17 page
Topological Physics of Little Higgs Bosons
Topological interactions will generally occur in composite Higgs or Little
Higgs theories, extra-dimensional gauge theories in which A_5 plays the role of
a Higgs boson, and amongst the pNGB's of technicolor. This phenomena arises
from the chiral and anomaly structure of the underlying UV completion theory,
and/or through chiral delocalization in higher dimensions. These effects are
described by a full Wess-Zumino-Witten term involving gauge fields and pNGB's.
We give a general discussion of these interactions, some of which may have
novel signatures at future colliders, such as the LHC and ILC.Comment: 22 page
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 Alzheimer’s 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 berberine’s antidementia activities were identified using “berberine” and “dementia” as search terms. In search B, recent studies on berberine’s effects on diabetes were surveyed using “berberine” and “diabetes” as search terms.
Inclusion criteria
Clinical and preclinical studies that investigated berberine’s 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 β-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
There’s just huge anxiety: ontological security, moral panic, and the decline in young people’s mental health and well-being in the UK
This study aims to critically discuss factors associated with a recent dramatic rise in recorded mental health issues amongst UK youth. It draws from interviews and focus groups undertaken with young people, parents and professionals. We offer valuable new insights into significant issues affecting young people’s mental health and well-being that are grounded in their lived experiences and in those who care for and work with them. By means of a thematic analysis of the data, we identified an increase in anxiety related to: future orientation, social media use, education, austerity, and normalization of mental distress and self-harm. We apply the notion of ontological security in our interpretation of how socio-cultural and political changes have increased anxiety amongst young people and consequent uncertainty about the self, the world and the future, leading to mental health problems. There are also problems conceptualizing and managing adolescent mental health, including increased awareness, increased acceptance of these problems, and stigmatisation. We relate this to the tendency for moral panic and widespread dissemination of problems in a risk society. In our conclusion, we highlight implications for future research, policy and practice
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