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An asymptotic method for calculating limits of maximal means
Authors:O P Filatov
Institution:(1) Samara State University, USSR
Abstract:For a continuous almost periodic function 
$$f: \mathbb{R}^{m_\tau  }   \times  \mathbb{R}^{m_\gamma  }   \to  \mathbb{R}$$
, we show that the function

$$M_f \left( \mu  \right) =  \mathop {\lim }\limits_{\Delta  \to \infty } \mathop {\sup }\limits_{\tau , \gamma } \frac{1}{\Delta }\smallint _0^\Delta  f\left( {\tau \left( {\mu t} \right),\gamma \left( t \right)} \right)dt,$$
where the supremum is taken over all solutions of the system of differential inclusion 
$$\dot \tau   \in  \mu G_\tau  ,\tau \left( 0 \right)  =  \tau _0 $$
, 
$$\dot \gamma  \in G_{_\gamma  } ,\gamma \left( 0 \right)  =  \gamma _0 $$
, has the following limit (as μ→+0):

$$\Psi _f  = \mathop {\lim }\limits_{\Delta  \to \infty } \mathop {\sup }\limits_\tau  \frac{1}{\Delta }\int_0^\Delta  {\Phi (\tau (\mu t))dt,}         where   \Phi (\tau _0 ) = \mathop {\lim }\limits_{\Delta  \to \infty } \mathop {\sup }\limits_\gamma  \frac{1}{\Delta }\int_0^\Delta  {f(\tau _0 ,\gamma (t))dt} .$$
, Thus if the parameter μ is small, then 
$$\Psi _f   =  \lim _{\mu  \to  + 0} M_f \left( \mu  \right)$$
and the limit of the maximal mean can approximately be determined by solving problems of smaller dimensionality. Moreover, if the compact sets 
$$G_\tau   \subset \mathbb{R}^{m_\tau  } $$
and 
$$G_\gamma   \subset \mathbb{R}^{m_\gamma  } $$
are nondegenerate, then Ψ f is independent of initial data. Translated fromMatematicheskie Zametki, Vol. 66, No. 3, pp. 431–438, September, 1999.
Keywords:almost periodic functions  asymptotic method  limit of maximal means  generalized differential equation  Bochner almost periodic function
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