4,696 research outputs found
Tectonic asymmetry of the earth and other planets
The structures of Earth, Mars, Venus, and the Moon are examined and compared. Global tectonic characteristics are presented for each. A comparison of the tectonics reveals the structural asymetry of these planets and the moon. Tectonic asymmetry information for the group is used to interpret certain aspects of the earth's geological past
Using Molecules to Measure Nuclear Spin-Dependent Parity Violation
Nuclear spin-dependent parity violation arises from weak interactions between
electrons and nucleons, and from nuclear anapole moments. We outline a method
to measure such effects, using a Stark-interference technique to determine the
mixing between opposite-parity rotational/hyperfine levels of ground-state
molecules. The technique is applicable to nuclei over a wide range of atomic
number, in diatomic species that are theoretically tractable for
interpretation. This should provide data on anapole moments of many nuclei, and
on previously unmeasured neutral weak couplings
Enhanced sensitivity to time-variation of m_p/m_e in the inversion spectrum of ammonia
We calculate the sensitivity of the inversion spectrum of ammonia to possible
time-variation of the ratio of the proton mass to the electron mass,
mu=m_p/m_e. For the inversion transition (lambda= 1.25 cm^{-1}) the relative
frequency shift is significantly enhanced: delta(omega)/omega=-4.46,
delta(mu)/mu. This enhancement allows one to increase sensitivity to the
time-variation of mu using NH_3 spectra for high redshift objects. We use
published data on microwave spectra of the object B0218+357 to place the limit
delta(mu)/mu =(0.6 +/- 1.9) 10^{-6} at redshift z=0.6847; this limit is several
times better than the limits obtained by different methods and may be
significantly improved. Assuming linear time dependence we obtain
dot{mu}/mu=(-1 +/- 3) 10^{-16} yr^{-1}
Tectonics and volcanisms of Mars
Televised images of Mars transmitted from interplanetary stations are used to develop a theory of the structure and development of the planet. Crater chronology, the structure of planetary bodies in the Earth group, and a comparison of the Earth planetary bodies are among the factors included
A Necessary Condition for existence of Lie Symmetries in Quasihomogeneous Systems of Ordinary Differential Equations
Lie symmetries for ordinary differential equations are studied. In systems of
ordinary differential equations, there do not always exist non-trivial Lie
symmetries around equilibrium points. We present a necessary condition for
existence of Lie symmetries analytic in the neighbourhood of an equilibrium
point. In addition, this result can be applied to a necessary condition for
existence of a Lie symmetry in quasihomogeneous systems of ordinary
differential equations. With the help of our main theorem, it is proved that
several systems do not possess any analytic Lie symmetries.Comment: 15 pages, no figures, AMSLaTe
Radar Range Deception with Time-Modulated Scatterers
Modern radar systems are designed to have high Doppler tolerance to detect
fast-moving targets. This means range and Doppler estimations are inevitably
coupled, opening pathways to concealing objects by imprinting artificial
Doppler signatures on the reflected echoes. Proper temporal control of the
backscattered phase can cause the investigating radar to estimate wrong range
and velocity, thus cloaking the real position and trajectory of the scatterer.
This deception method is exploited here theoretically for arbitrary Doppler
tolerant waveforms and then tested experimentally on an example of the linear
frequency modulated radar, which is the most common waveform of that class used
in practice. The method allows retaining radio silence with a semi passive
(battery assisted) approach that can work well with time-dependent
metasurfaces. Furthermore, as an insight into new capabilities, we demonstrate
that temporally concealed objects could even be made to appear closer than they
truly are without violating the laws of relativity
The First Lyapunov Method for Strongly Non-linear Systems of Differential Equations
The article is aimed to give a brief review of works published by authors during at least last 10 years and devoted to the construction of solutions of systems of ordinary differential equations in a neighbourhood of a nonelementary criticai point
Complete integrability versus symmetry
The purpose of this article is to show that on an open and dense set,
complete integrability implies the existence of symmetry
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