2,010 research outputs found
Lorentz-violating effects in the Bose-Einstein condensation of an ideal bosonic gas
We have studied the effects of Lorentz-violation in the Bose-Einstein
condensation (BEC) of an ideal boson gas, by assessing both the nonrelativistic
and ultrarelativistic limits. Our model describes a massive complex scalar
field coupled to a CPT-even and Lorentz-violating background. We irst analyze
the nonrelativistic case, at this level by using experimental data, we obtain
upper-bounds for some LIV parameters. In the sequel, we have constructed the
partition function for the relativistic ideal boson gas which to be able of a
consistent description requires the imposition of severe restrictions on some
LIV coefficients. In both cases, we have demonstrated that the LIV
contributions are contained in an overall factor, which multiplies almost all
thermodynamical properties. An exception is the fraction of the condensed
particles.Comment: 7 pages Latex2e. To be published in Modern Physics Letters
Temperature dependence of chemical and biophysical rate processes: Phenomenological approach to deviations from Arrhenius law
Arrhenius plots, which are used to represent the effects of temperature on the rates of chemical and biophysical processes and on various transport phenomena in materials science, may exhibit deviations from linearity. Account of curvature is provided here by a formula which involves a deformation of the exponential function, of the kind recently encountered in treatments of non-extensivity in statistical mechanics. We present here examples on diverse topics – respiration rates of plants, speed of gliding of bacteria, quantum mechanical tunneling in a chemical reaction – illustrating the variety of possible applications and the additional insight that can be gained
Four-path interference and uncertainty principle in photodetachment microscopy
We study the quantal motion of electrons emitted by a pointlike monochromatic
isotropic source into parallel uniform electric and magnetic fields. The
two-path interference pattern in the emerging electron wave due to the electric
force is modified by the magnetic lens effect which periodically focuses the
beam into narrow filaments along the symmetry axis. There, four classical paths
interfere. With increasing electron energy, the current distribution changes
from a quantum regime governed by the uncertainty principle, to an intricate
spatial pattern that yields to a semiclassical analysis.Comment: submitted to Europhysics Letter
Gravitational magnetic monopoles and Majumdar-Papapetrou stars
A large amount of work has been dedicated to studying general relativity
coupled to non-Abelian Yang-Mills type theories. It has been shown that the
magnetic monopole, a solution of the Yang-Mills-Higgs equations can be coupled
to gravitation. For a low Higgs mass there are regular solutions, and for a
sufficiently massive monopole the system develops an extremal magnetic
Reissner-Nordstrom quasi-horizon. These solutions, called quasi-black holes,
although non-singular, are arbitrarily close to having a horizon. However, at
the critical value the quasi-black hole turns into a degenerate spacetime. On
the other hand, for a high Higgs mass, a sufficiently massive monopole develops
also a quasi-black hole, but it turns into an extremal true horizon, with
matter fields outside. One can also put a small Schwarzschild black hole inside
the magnetic monopole, an example of a non-Abelian black hole. Surprisingly,
Majumdar-Papapetrou systems, Abelian systems constructed from extremal dust,
also show a resembling behavior. Previously, we have reported that one can find
Majumdar-Papapetrou solutions which can be arbitrarily close of being a black
hole, displaying quasi-black hole behavior. With the aim of better
understanding the similarities between gravitational monopoles and
Majumdar-Papapetrou systems, we study a system composed of two extremal
electrically charged spherical shells (or stars, generically) in the
Einstein--Maxwell--Majumdar-Papapetrou theory. We review the gravitational
properties of the monopoles, and compare with the properties of the double
extremal electric shell system. These quasi-black holes can help in the
understanding of true black holes, and can give insight into the nature of the
entropy of black holes in the form of entanglement.Comment: 38 pages,9 Figures, minor change
Exposure to violence and PTSD symptoms among Somali women
Posttraumatic stress disorder (PTSD) symptoms, exposure to traumatic stressors, and health care utilization were examined in 84 women attending a primary health care clinic in Mogadishu, Somalia. The Somalia-Posttraumatic Diagnostic Scale was used in this active warzone to measure symptoms. Nearly all women reported high levels of confrontations with violence; half described being exposed to a potentially traumatizing event. Nearly one third had significant PTSD symptoms. Compared to those who did not, women who reported exposure to a traumatic stressor reported more confrontations with violence (7.1 vs. 3.3; p < . 001), health complaints (3.8 vs. 2.9; p = .03), and nearly 3 times as much (p = .03) health service utilization. A potentially traumatizing event was found to be a simplified proxy for assessing mental health distress in women attending a primary health care facility in highly insecure, unpredictable, resource-limited settings
High pressure torsion of nickel powders obtained by electrodeposition
A new synthesis route for the production of bulk nanostructured materials is presented.
Fine Ni powder was made by selected appropriate electrolysis conditions. A
compact material with an average grain size below 40 nm was obtained by subsequent
cold pressing. Then, using the high pressure torsion (HPT) deformation technique dense
bulk nanocrystalline Ni was achieved. The detailed structural investigations of the asprepared
and HPT deformed Ni powder, including X-ray diffraction (XRD) and transmission
electron microscopy (TEM), reveal in both cases the presence of a face centered
cubic (FCC) phase without presence of any oxides. Coherently scattering domain size
measurements by XRD show a value of 24 nm for the as-deposited powder and an even
smaller value of 13.5 nm after HPT deformation. In addition, optical emission spectroscopy
was employed to determine the impurity content of the obtained nanostructured
material, showing a relatively low content of 0.9 % carbon and oxygen. The microhardness
increased after deformation from (1.5 ± 0.08) GPa for the as-deposited Ni powder
to (6.6 ± 0.2) GPa for the HPT deformed Ni powder.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2061
Qualitative Assessment of General Aviation Pilots’ Perceptions of Preflight Weather Briefings
Prior to departing on a flight, General Aviation pilots complete a pre-flight planning process to ensure the safety of their flight. One aspect of the pre-flight planning process is obtaining a briefing on the weather conditions that the pilot might encounter along their flight route. Traditionally pilots have utilized a phone-in service run by Flight Services to aid in their assessment of weather conditions. However, research indicates that pilots are increasingly reliant on conducting self- briefing using online resources. The purpose of this study is to determine pilot perceptions of obtaining a phone-in brief in comparison to self-briefing
Quasiblack holes with pressure: relativistic charged spheres as the frozen stars
In general relativity coupled to Maxwell's electromagnetism and charged
matter, when the gravitational potential and the electric potential field
obey a relation of the form , where , and are arbitrary constants, and (the
speed of light and Newton's constant are put to one), a class of very
interesting electrically charged systems with pressure arises. We call the
relation above between and , the Weyl-Guilfoyle relation, and it
generalizes the usual Weyl relation, for which . For both, Weyl and
Weyl-Guilfoyle relations, the electrically charged fluid, if present, may have
nonzero pressure. Fluids obeying the Weyl-Guilfoyle relation are called
Weyl-Guilfoyle fluids. These fluids, under the assumption of spherical
symmetry, exhibit solutions which can be matched to the electrovacuum
Reissner-Nordstr\"om spacetime to yield global asymptotically flat cold charged
stars. We show that a particular spherically symmetric class of stars found by
Guilfoyle has a well-behaved limit which corresponds to an extremal
Reissner-Nordstr\"om quasiblack hole with pressure, i.e., in which the fluid
inside the quasihorizon has electric charge and pressure, and the geometry
outside the quasihorizon is given by the extremal Reissner-Nordstr\"om metric.
The main physical properties of such charged stars and quasiblack holes with
pressure are analyzed. An important development provided by these stars and
quasiblack holes is that without pressure the solutions, Majumdar-Papapetrou
solutions, are unstable to kinetic perturbations. Solutions with pressure may
avoid this instability. If stable, these cold quasiblack holes with pressure,
i.e., these compact relativistic charged spheres, are really frozen stars.Comment: 16 pages, 8 figures; minor change
- …