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Displaying 441 –
460 of
4762
For a vector field ξ on ℝ² we construct, under certain assumptions on ξ, an ordered model-theoretic structure associated to the flow of ξ. We do this in such a way that the set of all limit cycles of ξ is represented by a definable set. This allows us to give two restatements of Dulac’s Problem for ξ - that is, the question whether ξ has finitely many limit cycles-in model-theoretic terms, one involving the recently developed notion of -rank and the other involving the notion of o-minimality.
We consider a free boundary problem of a two-dimensional Navier-Stokes shear flow. There exist a unique global in time solution of the considered problem as well as the global attractor for the associated semigroup. As in [1] and [2], we estimate from above the dimension of the attractor in terms of given data and the geometry of the domain of the flow. This research is motivated by a free boundary problem from lubrication theory where the domain of the flow is usually very thin and the roughness...
Recently, adult stem cells have become a focus of intensive biomedical research, but the
complex regulation that allows a small population of stem cells to replenish depleted tissues is still
unknown. It has been suggested that specific tissue structures delimit the spaces where stem cells
undergo unlimited proliferation (stem cell niche). In contrast, mathematical analysis suggests that
a feedback control of stem cells on their own proliferation and differentiation (denoted Quorum
Sensing) suffices...
Infectious diseases may have multiple infectious stages with very different epidemiological attributes,
including infectivity and disease progression. These stages are often
assumed to have exponentially distributed durations in epidemiological models. However,
models that use the exponential distribution assumption (EDA) may generate biased and
even misleading results in some cases. This discrepancy is particularly damaging if the models
are employed to assist policy-makers in disease control...
We consider a chaotic system with a double-scroll attractor proposed by Elwakil, composing with a second-order system, which has low-dimensional multiple invariant subspaces and multi-level on-off intermittency. This type of composite system always includes a skew-product structure and some invariant subspaces, which are associated with different levels of laminar phase. In order for the level of laminar phase be adjustable, we adopt a nonlinear function with saturation characteristic to tune the...
Here we present basic ideas and algorithms of Power Geometry and give a survey of some of its applications. In Section 2, we consider one generic ordinary differential equation and demonstrate how to find asymptotic forms and asymptotic expansions of its solutions. In Section 3, we demonstrate how to find expansions of solutions to Painlevé equations by this method, and we analyze singularities of plane oscillations of a satellite on an elliptic orbit. In Section 4, we consider the problem of local...
In [C.W. Gear, T.J. Kaper, I.G. Kevrekidis and A. Zagaris,
SIAM J. Appl. Dyn. Syst. 4 (2005) 711–732],
we developed
a class of iterative algorithms
within the context
of equation-free methods
to approximate
low-dimensional,
attracting,
slow manifolds
in systems
of differential equations
with multiple time scales.
For user-specified values
of a finite number
of the observables,
the mth member
of the class
of algorithms
()
finds iteratively
an approximation
of the appropriate zero
of the (m+1)st...
Tuberculosis (TB) remains a major global health problem. A possible risk factor for TB is
diabetes (DM), which is predicted to increase dramatically over the next two decades,
particularly in low and middle income countries, where TB is widespread. This study aimed
to assess the strength of the association between TB and DM. We present a deterministic
model for TB in a community in order to determine the impact of DM in the spread of the
disease....
Nilsequences arose in the study of the multiple ergodic averages associated to Furstenberg’s proof of Szemerédi’s Theorem and have since played a role in problems in additive combinatorics. Nilsequences are a generalization of almost periodic sequences and we study which portions of the classical theory for almost periodic sequences can be generalized for two step nilsequences. We state and prove basic properties for two step nilsequences and give a classification scheme for them.
This work describes a method to rigorously compute the real Floquet normal form decomposition of the fundamental matrix solution of a system of linear ODEs having periodic coefficients. The Floquet normal form is validated in the space of analytic functions. The technique combines analytical estimates and rigorous numerical computations and no rigorous integration is needed. An application to the theory of dynamical system is presented, together with a comparison with the results obtained by computing...
Associated to analytic Hamiltonian vector fields in having an equilibrium point satisfying a non semisimple resonance, we construct two constants that are invariant with respect to local analytic symplectic changes of coordinates. These invariants vanish when the Hamiltonian is integrable. We also prove that one of these invariants does not vanish on an open and dense set.
Analytic solutions of polynomial-like iterative functional equations with variable coefficients are discussed in the complex field ℂ by reducing to an auxiliary equation and by applying known results for systems of nonlinear functional equations of finite orders.
Currently displaying 441 –
460 of
4762