142 research outputs found
Wightman function and Casimir densities for Robin plates in the Fulling-Rindler vacuum
Wightman function, the vacuum expectation values of the field square and the
energy-momentum tensor are investigated for a massive scalar field with an
arbitrary curvature coupling parameter in the region between two infinite
parallel plates moving by uniform proper acceleration. We assume that the field
is prepared in the Fulling-Rindler vacuum state and satisfies Robin boundary
conditions on the plates. The mode-summation method is used with a combination
of a variant of the generalized Abel-Plana formula. This allows to extract
manifestly the contributions to the expectation values due to a single boundary
and to present the second plate-induced parts in terms of exponentially
convergent integrals. Various limiting cases are investigated. The vacuum
forces acting on the boundaries are presented as a sum of the self-action and
'interaction' terms. The first one contains well known surface divergences and
needs a further renormalization. The 'interaction' forces between the plates
are investigated as functions of the proper accelerations and coefficients in
the boundary conditions. We show that there is a region in the space of these
parameters in which the 'interaction' forces are repulsive for small distances
and attractive for large distances.Comment: 20 pages, 2 figures, discussion added, accepted for publication in
Int. J. Mod. Phys.
Accelerated Expansion of the Early and Late Universe in Terms of the Scalar-Tensor Theory of Gravitation. I
© 2017 Springer Science+Business Media New YorkThe basic idea behind the evolutionary development of the early universe is that the hot stage was preceded by the inflationary stage. In most modern concepts of the inflationary regime, it is assumed that a specific scalar field (inflaton) is present which expands space at enormous rates, while the temperature falls rapidly, real particles almost vanish, and the universe is filled by a vacuum with the equation of state P = – ɛ. In the first part of this article, the cosmological scalar of the modified Jordan-Brans-Dicke (JBD) theory is chosen to be the inflaton. Problems in the “Einstein” and proper representations of the JBD theory are considered
Some Properties of Stationary Gravitational Fields
© 2015 Springer Science+Business Media New York The problem of stationary gravitational fields is still far from solved, since there is no exact general solution of the Einstein equations for stationary gravitational fields. This paper examines an approach to this problem employing isotropic coordinates which, in particular, make it possible to understand which simplifications yield the Kerr solution
Vacuum Quantum Effects for Parallel Plates Moving by Uniform Acceleration in Static de Sitter Space
The Casimir forces on two parallel plates moving by uniform proper
acceleration in static de Sitter background due to conformally coupled massless
scalar field satisfying Dirichlet boundary conditions on the plates is
investigated. Static de Sitter space is conformally related to the Rindler
space, as a result we can obtain vacuum expectation values of energy-momentum
tensor for conformally invariant field in static de Sitter space from the
corresponding Rindler counterpart by the conformal transformation.Comment: 10 pages, no figures, accepted for publication in Int. J. Mod. Phys.
May Measurement Month 2017: an analysis of blood pressure screening results in Armenia-Europe
Elevated blood pressure (BP) is a growing burden worldwide, leading to over 10 million deaths each year. May Measurement Month (MMM) is a global initiative aimed at raising awareness of high BP and to act as a temporary solution to the lack of screening programmes worldwide. An opportunistic cross-sectional survey of volunteers aged ≥18 was carried out in May 2017. Blood pressure measurement, the definition of hypertension and statistical analysis followed the standard MMM protocol. The study was conducted in public areas (14 sites in Yerevan and 18 in regions), both indoor and outdoor, as well as in 42 primary care centres. A total of 9199 individuals were screened during MMM17 of which 9186 had three BP measurements available. The mean age of screened individuals was 50 ± 16.7 years, 57.3% was female. At the time of screening 17.9% were on antihypertensive medication. After imputation, a percentage of participants with hypertension was 33.9%, and 52.9% of them were on treatment. Of those treated, 77.0% had uncontrolled BP. MMM17 was the largest BP screening campaign undertaken in Armenia. We found that in Armenia, untreated hypertension is common, as is not adequately treated hypertension
Multiple Monoenergetic Gamma Radiography (MMGR) with a compact superconducting cyclotron
Smuggling of special nuclear materials (SNM) and nuclear devices through
borders and ports of entry constitutes a major risk to global security.
Technologies are needed to reliably screen the flow of commerce for the
presence of high- materials such as uranium and plutonium. Here we present
an experimental proof-of-concept of a technique which uses inelastic ()
nuclear reactions to generate monoenergetic photons, which provide means to
measure the areal density and the effective- () of an object
with an accuracy which surpasses that achieved by current methods. We use an
ION-12 superconducting 12~MeV proton cyclotron to produce 4.4,
6.1, 6.9, and 7.1~MeV photons from a variety of nuclear reactions. Using these
photons in a transmission mode we show that we are able to accurately
reconstruct the areal densities and of a test object. This
methodology could enable mobile applications to screen commercial cargoes with
high material specificity, providing a means of distinguishing common cargo
materials from high-Z materials that include uranium and plutonium
An analysis of blood pressure screening of 21 112 participants in Armenia: May Measurement Month 2018.
Elevated blood pressure (BP) is a growing burden worldwide and is the leading cause of mortality and disability-adjusted life years all over the world. May Measurement Month (MMM) is a global initiative aimed to raise awareness of high BP and to act as a temporary solution to the lack of screening programmes worldwide. An opportunistic cross-sectional survey of volunteers aged ≥18 was carried out in May to July 2018. Blood pressure measurement, the definition of hypertension (HTN) and statistical analysis followed the standard MMM protocol. The study was conducted in public areas (17 sites in Yerevan and 22 in regions), both indoor and outdoor, as well as in 78 primary care centres. A total of 21 112 individuals were screened during MMM18, of which 20 732 had three BP measurements available. The mean age of screened individuals was 46.2 ± 17.3 years, 57.8% were female. At the time of screening, 26.1% were on antihypertensive medication. After imputation, the percentage of participants with HTN was 38.7%, and 76.7% of them were aware of their high BP. Of participants receiving treatment, 47.1% had a controlled BP. MMM18 was the largest BP screening campaign undertaken in Armenia. We found that the proportion of HTN is substantial in Armenia, which may be a vital contributor to the growing burden of non-communicable diseases. Our results also suggest that untreated HTN is common and when treated still not adequately controlled in Armenia. The current situation, with an insufficient control rate of HTN, must be changed as soon as possible
Casimir energy in the Fulling--Rindler vacuum
The Casimir energy is evaluated for massless scalar fields under Dirichlet or
Neumann boundary conditions, and for the electromagnetic field with perfect
conductor boundary conditions on one and two infinite parallel plates moving by
uniform proper acceleration through the Fulling--Rindler vacuum in an arbitrary
number of spacetime dimension. For the geometry of a single plate the both
regions of the right Rindler wedge, (i) on the right (RR region) and (ii) on
the left (RL region) of the plate are considered. The zeta function technique
is used, in combination with contour integral representations. The Casimir
energies for separate RR and RL regions contain pole and finite contributions.
For an infinitely thin plate taking RR and RL regions together, in odd spatial
dimensions the pole parts cancel and the Casimir energy for the whole Rindler
wedge is finite. In spatial dimensions the total Casimir energy for a
single plate is negative for Dirichlet scalar and positive for Neumann scalar
and the electromagnetic field. The total Casimir energy for two plates geometry
is presented in the form of a sum of the Casimir energies for separate plates
plus an additional interference term. The latter is negative for all values of
the plates separation for both Dirichlet and Neumann scalars, and for the
electromagnetic field.Comment: 28 pages, 4 figures, references added, typos corrected, accepted for
publication in Phys. Rev.
On the energy-momentum tensor for a scalar field on manifolds with boundaries
We argue that already at classical level the energy-momentum tensor for a
scalar field on manifolds with boundaries in addition to the bulk part contains
a contribution located on the boundary. Using the standard variational
procedure for the action with the boundary term, the expression for the surface
energy-momentum tensor is derived for arbitrary bulk and boundary geometries.
Integral conservation laws are investigated. The corresponding conserved
charges are constructed and their relation to the proper densities is
discussed. Further we study the vacuum expectation value of the energy-momentum
tensor in the corresponding quantum field theory. It is shown that the surface
term in the energy-momentum tensor is essential to obtain the equality between
the vacuum energy, evaluated as the sum of the zero-point energies for each
normal mode of frequency, and the energy derived by the integration of the
corresponding vacuum energy density. As an application, by using the zeta
function technique, we evaluate the surface energy for a quantum scalar field
confined inside a spherical shell.Comment: 25 pages, 2 figures, section and appendix on the surface energy for a
spherical shell are added, references added, accepted for publication in
Phys. Rev.
The role of terminoelements in the organization of names of oncological diseases of the blood and lymphatic systems
The article discusses the principles of the formation of oncological diseases of the circulatory and lymphatic systems.В статье рассмотрены принципы образования названий онкологических заболеваний кровеносной и лимфатической систем
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