59 research outputs found
On the dark matter's halo theoretical description
We argued that the standard field scalar potential couldn't be widely used
for getting the adequate galaxies' curve lines and determining the profiles of
dark matter their halo. For discovering the global properties of scalar fields
that can describe the observable characteristics of dark matter on the
cosmological space and time scales, we propose the simplest form of central
symmetric potential celestial - mechanical type, i.e. U(\phi) = -\mu/\phi. It
was shown that this potential allows get rather satisfactorily dark matter
profiles and rotational curves lines for dwarf galaxies. The good agreement
with some previous results, based on the N-body simulation method, was pointed
out. A new possibility of dwarf galaxies' masses estimation was given, also.Comment: 10p., 18 re
Stability analysis of dynamical regimes in nonlinear systems with discrete symmetries
We present a theorem that allows to simplify linear stability analysis of
periodic and quasiperiodic nonlinear regimes in N-particle mechanical systems
(both conservative and dissipative) with different kinds of discrete symmetry.
This theorem suggests a decomposition of the linearized system arising in the
standard stability analysis into a number of subsystems whose dimensions can be
considerably less than that of the full system. As an example of such
simplification, we discuss the stability of bushes of modes (invariant
manifolds) for the Fermi-Pasta-Ulam chains and prove another theorem about the
maximal dimension of the above mentioned subsystems
Discrete Symmetry and Stability in Hamiltonian Dynamics
In this tutorial we address the existence and stability of periodic and
quasiperiodic orbits in N degree of freedom Hamiltonian systems and their
connection with discrete symmetries. Of primary importance in our study are the
nonlinear normal modes (NNMs), i.e periodic solutions which represent
continuations of the system's linear normal modes in the nonlinear regime. We
examine the existence of such solutions and discuss different methods for
constructing them and studying their stability under fixed and periodic
boundary conditions. In the periodic case, we employ group theoretical concepts
to identify a special type of NNMs called one-dimensional "bushes". We describe
how to use linear combinations such NNMs to construct s(>1)-dimensional bushes
of quasiperiodic orbits, for a wide variety of Hamiltonian systems and exploit
the symmetries of the linearized equations to simplify the study of their
destabilization. Applying this theory to the Fermi Pasta Ulam (FPU) chain, we
review a number of interesting results, which have appeared in the recent
literature. We then turn to an analytical and numerical construction of
quasiperiodic orbits, which does not depend on the symmetries or boundary
conditions. We demonstrate that the well-known "paradox" of FPU recurrences may
be explained in terms of the exponential localization of the energies Eq of
NNM's excited at the low part of the frequency spectrum, i.e. q=1,2,3,....
Thus, we show that the stability of these low-dimensional manifolds called
q-tori is related to the persistence or FPU recurrences at low energies.
Finally, we discuss a novel approach to the stability of orbits of conservative
systems, the GALIk, k=2,...,2N, by means of which one can determine accurately
and efficiently the destabilization of q-tori, leading to the breakdown of
recurrences and the equipartition of energy, at high values of the total energy
E.Comment: 50 pages, 13 figure
Could One Find Petroleum Using Neutrino Oscillations in Matter?
In neutrino physics, it is now widely believed that neutrino oscillations are
influenced by the presence of matter, modifying the energy spectrum produced by
a neutrino beam traversing the Earth. Here, we will discuss the reverse
problem, i.e. what could be learned about the Earth's interior from a single
neutrino baseline energy spectrum, especially about the Earth's mantle. We will
use a statistical analysis with a low-energy neutrino beam under very
optimistic assumptions. At the end, we will note that it is hard to find
petroleum with such a method, though it is not too far away from technical
feasibility.Comment: 6 pages, 4 figures, EPL LaTeX. Final version to be published in
Europhys. Let
High Latitude Dynamics of Atmosphere-Ice-Ocean Interactions
Dynamics of atmosphere–ice–ocean interactions in the high latitudes. What: Scientists from 13 countries involved with modeling and observing the coupled high-latitude weather and climate system discussed our current understanding and challenges in polar prediction, extreme events, and coupled processes on scales ranging from cloud and turbulent processes, from micrometers and a few hundred meters to processes on synoptic-scale weather phenomena and pan-Arctic energy budgets of hundreds to thousands of kilometers. Workshop participants also evaluated research needs to improve numerical models with usages spanning from uncoupled to fully coupled models used for weather and climate prediction (http://highlatdynamics.b.uib.no/). When: 23–27 March 2015. Where: Rosendal, Norwa
Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals
We briefly summarize the reported anomalous effects in deuterated metals at
ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on
important experiments as well as the theoretical basis for the opposition to
interpreting them as cold fusion. Then we critically examine more than 25
theoretical models for CF, including unusual nuclear and exotic chemical
hypotheses. We conclude that they do not explain the data.Comment: 51 pages, 4 Figure
The Maximum Energy and Spectra of Cosmic Rays Accelerated in Active Galactic Nuclei
We computed the energy spectra of the incident (on an air shower array)
ultrahigh-energy (E > 4x10^19 eV) cosmic rays (CRs) that were accelerated in
nearby Seyfert nuclei at redshifts z<= 0.0092 and in BL Lac objects. For our
calculations, we took the distribution of these sources over the sky from
catalogs of active galactic nuclei. In accordance with the possible particle
acceleration mechanisms, the initial CR spectrum was assumed to be
monoenergetic for BL Lac's and a power law for Seyfert nuclei. The CR energy
losses in intergalactic space were computed by the Monte Carlo method. The
artificial proton statistic was 10^5 for each case considered. The computed
spectra of the particles incident on an air shower array agree with the
measurements, which indirectly confirms the adopted acceleration models. At
energies E>=10^20 eV, the spectrum of the protons from nearby Seyfert nuclei
that reached an air shower array closely matches the spectrum of the particles
from BL Lac's. BL Lac's are, on average, several hundred Mpc away. Therefore,
it is hard to tell whether a blackbody cutoff exists or not by analyzing the
shape of the measured spectrum at E>= 5x10^19 eV.Comment: 14 pages, 5 fig. To be Published in Astronomy Letters, 2004, v.30,
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