722 research outputs found
Evolutionary Status of Long-Period Radio Pulsars
We analyze the evolutionary status of recently discovered long-period radio
sources PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. We discuss the
hypothesis that all three sources are radio pulsars. In the framework of
standard scenarios, it is often accepted that the pulsar mechanism is switched
off when an external matter can penetrate the light cylinder. If the matter is
stopped outside the light cylinder then the neutron star is at the ejector
stage. We demonstrate that for realistic parameters of the interstellar medium,
the 76-second pulsar PSR J0901-4046 might be at this stage. However, sources
GLEAM-X J1627-52 and GPM J1839-10 with periods s can be ejectors
only in the case of unrealistically large dipolar fields G.
Also, we show that neutron stars with spin periods s and dipolar
magnetic fields G cannot be ejectors in a typical
interstellar medium. Thus, we predict that long-period pulsars with standard
fields will not be discovered.Comment: 7 pages, 2 figures, accepted to Astronomy Letters, translation by the
author
The Effect of Surface Roughness on the Universal Thermal Conductance
We explain the reduction of the thermal conductance below the predicted
universal value observed by Schwab et al. in terms of the scattering of thermal
phonons off surface roughness using a scalar model for the elastic waves. Our
analysis shows that the thermal conductance depends on two roughness
parameters: the roughness amplitude and the correlation length .
At sufficiently low temperatures the conductance decrease from the universal
value quadratically with temperature at a rate proportional to .
Values of equal to 0.22 and equal to about 0.75 of the width of
the conduction pathway give a good fit to the data.Comment: 10 pages, 5 figures. Ref. added, typo correcte
Early Accretion Onset in Long-Period Isolated Pulsars
We model long-term magneto-rotational evolution of isolated neutron stars
with long initial spin periods. This analysis is motivated by the recent
discovery of young long-period neutron stars observed as periodic radio
sources: PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. Our calculations
demonstrate that for realistically rapid spin-down during the propeller stage
all isolated neutron stars with velocities km s are able
to reach the stage of accretion from the interstellar medium within a few
billion years. If neutron stars with long initial spin periods form a
relatively large fraction of all Galactic neutron stars then the number of
isolated accretors is sufficiently larger than it has been predicted by
previous studies.Comment: 12 pages, 2 figures, submitted to PAS
Quantum theory as a relevant framework for the statement of probabilistic and many-valued logic
Based on ideas of quantum theory of open systems we propose the consistent
approach to the formulation of logic of plausible propositions. To this end we
associate with every plausible proposition diagonal matrix of its likelihood
and examine it as density matrix of relevant quantum system. We are showing
that all logical connectives between plausible propositions can be represented
as special positive valued transformations of these matrices. We demonstrate
also the above transformations can be realized in relevant composite quantum
systems by quantum engineering methods. The approach proposed allows one not
only to reproduce and generalize results of well-known logical systems
(Boolean, Lukasiewicz and so on) but also to classify and analyze from unified
point of view various actual problems in psychophysics and social sciences.Comment: 7 page
Synthesis and spectral properties of colloidal solutions of metal sulfides
Cadmium, lead, and zinc sulfides as well as cadmium and lead (cadmium and zinc) complex sulfides have been synthesized in the colloidal state by reaction of metal trifluoroacetates with thioacetamide in ethyl acetate and methylmethacrylate. Synthesis products have been isolated from the reaction solutions and studied by X-ray diffraction, vibrational and electronic spectroscopy, and electronic microscopy. The effect of the composition on spectral properties of formulations has been discussed. The formation of colloidal particles and the stability of solutions are related to the complexation
Tevatron Beam Halo Collimation System: Design, Operational Experience and New Methods
Collimation of proton and antiproton beams in the Tevatron collider is
required to protect CDF and D0 detectors and minimize their background rates,
to keep irradiation of superconducting magnets under control, to maintain
long-term operational reliability, and to reduce the impact of beam-induced
radiation on the environment. In this article we briefly describe the design,
practical implementation and performance of the collider collimation system,
methods to control transverse and longitudinal beam halo and two novel
collimation techniques tested in the Tevatron.Comment: 25 p
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