460 research outputs found
Large-amplitude inviscid fluid motion in an accelerating container
Study of dynamic behavior of the liquid-vapor interface of an inviscid fluid in an accelerating cylindrical container includes an analytical-numerical method for determining large amplitude motion. The method is based on the expansion of the velocity potential in a series of harmonic functions with time dependent coefficients
Propagation of the phase of solar modulation
The phase of the 11 year galactic cosmic ray variation, due to a varying rate of emission of long lived propagating regions of enhanced scattering, travels faster than the scattering regions themselves. The radial speed of the 11 year phase in the quasi-steady, force field approximation is exactly twice the speed of the individual, episodic decreases. A time dependent, numerical solution for 1 GeV protons at 1 and 30 Au gives a phase speed which is 1.85 times the propagation speed of the individual decreases
Existence and uniqueness of limit cycles in a class of second order ODE's with inseparable mixed terms
We prove a uniqueness result for limit cycles of the second order ODE . Under mild additional conditions, we
show that such a limit cycle attracts every non-constant solution. As a special
case, we prove limit cycle's uniqueness for an ODE studied in \cite{ETA} as a
model of pedestrians' walk. This paper is an extension to equations with a
non-linear of the results presented in \cite{S}
Positrons in Cosmic Rays from Dark Matter Annihilations for Uplifted Higgs Regions in MSSM
We point out that there are regions in the MSSM parameter space which
successfully provide a dark matter (DM) annihilation explanation for observed
positron excess (e.g. PAMELA), while still remaining in agreement with all
other data sets. Such regions (e.g. the uplifted Higgs region) can realize an
enhanced neutralino DM annihilation dominantly into leptons via a Breit-Wigner
resonance through the CP-odd Higgs channel. Such regions can give the proper
thermal relic DM abundance, and the DM annihilation products are compatible
with current antiproton and gamma ray observations. This scenario can succeed
without introducing any additional degrees of freedom beyond those already in
the MSSM.Comment: 11 pages, 9 figure
Extended Quintessence with non-minimally coupled phantom scalar field
We investigate evolutional paths of an extended quintessence with a
non-minimally coupled phantom scalar field to the Ricci curvature. The
dynamical system methods are used to investigate typical regimes of dynamics at
the late time. We demonstrate that there are two generic types of evolutional
scenarios which approach the attractor (a focus or a node type critical point)
in the phase space: the quasi-oscillatory and monotonic trajectories approach
to the attractor which represents the FRW model with the cosmological constant.
We demonstrate that dynamical system admits invariant two-dimensional
submanifold and discussion that which cosmological scenario is realized depends
on behavior of the system on the phase plane . We formulate
simple conditions on the value of coupling constant for which
trajectories tend to the focus in the phase plane and hence damping
oscillations around the mysterious value . We describe this condition in
terms of slow-roll parameters calculated at the critical point. We discover
that the generic trajectories in the focus-attractor scenario come from the
unstable node. It is also investigated the exact form of the parametrization of
the equation of state parameter (directly determined from dynamics)
which assumes a different form for both scenarios.Comment: revtex4, 15 pages, 9 figures; (v2) published versio
An asymptotic formula for marginal running coupling constants and universality of loglog corrections
Given a two-loop beta function for multiple marginal coupling constants, we
derive an asymptotic formula for the running coupling constants driven to an
infrared fixed point. It can play an important role in universal loglog
corrections to physical quantities.Comment: 16 pages; typos fixed, one appendix removed for quick access to the
main result; to be published in J. Phys.
Some results on homoclinic and heteroclinic connections in planar systems
Consider a family of planar systems depending on two parameters and
having at most one limit cycle. Assume that the limit cycle disappears at some
homoclinic (or heteroclinic) connection when We present a method
that allows to obtain a sequence of explicit algebraic lower and upper bounds
for the bifurcation set The method is applied to two quadratic
families, one of them is the well-known Bogdanov-Takens system. One of the
results that we obtain for this system is the bifurcation curve for small
values of , given by . We obtain
the new three terms from purely algebraic calculations, without evaluating
Melnikov functions
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