453 research outputs found
Spectral Distortion in a Radially Inhomogeneous Cosmology
The spectral distortion of the cosmic microwave background blackbody spectrum
in a radially inhomogeneous spacetime, designed to exactly reproduce a
LambdaCDM expansion history along the past light cone, is shown to exceed the
upper bound established by COBE-FIRAS by a factor of approximately 3700. This
simple observational test helps uncover a slew of pathological features that
lie hidden inside the past light cone, including a radially contracting phase
at decoupling and, if followed to its logical extreme, a naked singularity at
the radially inhomogeneous Big Bang.Comment: 16 pages, 8 figures (added references and clarified discussion; some
numbers revised
Gravitational Wave - Gauge Field Oscillations
Gravitational waves propagating through a stationary gauge field transform
into gauge field waves and back again. When multiple families of flavor-space
locked gauge fields are present, the gravitational and gauge field waves
exhibit novel dynamics. At high frequencies, the system behaves like coupled
oscillators in which the gravitational wave is the central pacemaker. Due to
energy conservation and exchange among the oscillators, the wave amplitudes lie
on a multidimensional sphere, reminiscent of neutrino flavor oscillations. This
phenomenon has implications for cosmological scenarios based on flavor-space
locked gauge fields.Comment: 4 pages, 3 figures, 1 animation; replacement matches published
versio
Effect of humidity on characteristics of hydrogen sensors based on nanocrystalline SnO2 thin films with various catalysts
Stability of characteristics of resistive hydrogen sensors based on thin tin dioxide films with deposited catalysts Pt and Pd
Simulation of Thermal Surface Waves in a Protoplanetary Disk in a Two-Dimensional Approximation
Theoretical models predict that the obscuration of stellar radiation by
irregularities on the surface of a protoplanetary disk can cause
self-generating waves traveling towards the star. However, this process is
traditionally simulated using the 1+1D approach, the key approximations of
which - vertical hydrostatic equilibrium of the disk and vertical diffusion of
IR radiation - can distort the picture. This article presents a two-dimensional
radiative hydrodynamic model of the evolution of an axially symmetric gas and
dust disk. Within this model, but using simplified assumptions from 1+1D
models, we have reproduced the spontaneous generation and propagation of
thermal surface waves. The key conclusion of our work is that taking into
account two-dimensional hydrodynamics and diffusion of IR radiation suppresses
the spontaneous generation and development of thermal waves observed in the
1+1D approximation. The search for the possibility of the existence of surface
thermal waves should be continued by studying the problem for various
parameters of protoplanetary disks.Comment: Accepted for publication in Astronomy Reports (2022
Anomalies of Density, Stresses, and the Gravitational Field in the Interior of Mars
We determined the possible compensation depths for relief harmonics of
different degrees and orders. The relief is shown to be completely compensated
within the depth range of 0 to 1400 km. The lateral distributions of
compensation masses are determined at these depths and the maps are
constructed. The possible nonisostatic vertical stresses in the crust and
mantle of Mars are estimated to be 64 MPa in compression and 20 MPa in tension.
The relief anomalies of the Tharsis volcanic plateau and symmetric feature in
the eastern hemisphere could have arisen and been maintained dynamically due to
two plumes in the mantle substance that are enriched with fluids. The plumes
that originate at the core of Mars can arise and be maintained by the anomalies
of the inner gravitational field achieving +800 mGal in the region of plume
formation, - 1200 mGal above the lower mantle-core transition layer, and -1400
mGal at the crust.Comment: 9 pages, 5 figure
Effect of long-term operation on energy band bending at the SnO2 microcrystals interfaces in thin tin dioxide films with various catalysts
This work presents the results of investigation of stability of energy band bending at the SnO2 microcrystals interfaces in thin films of tin dioxide with deposited Pt and Pd dispersed layers (Pt/Pd/SnO2:Sb) and with the additions of gold in the bulk and on the surface (Au/SnO2:Sb, Au) in long - term operation. Measurements of energy band bending were showed that the significantly variation of this value is observed in first month of the sensor using. Perhaps this phenomenon is caused by the surface reconstruction during operation of sensors and consequently by the increase of density of oxygen ions chemisorbed on the surface of tin dioxide
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