On restricted MAD families
Let mathcalI be an ideal on omega. We define textsf{cov}$^{ast
}left( mathcal{I}right) $ as the least size of a family
mathcalBsubseteqI such that for every infinite XinmathcalI there
is BinmathcalB for which BcapX is infinite. We say an textsf{AD}
family mathcalAsubseteqI is a emph{textsf{MAD} family restricted to
}mathcalI if for every infinite XinmathcalI there is $Ain
mathcal{A}suchthatleftvert Xcap Arightvert =omega.$ The cardinal
invariant mathfrakaleft(mathcalIright) is defined as the least
size of an infinite textsf{MAD} family restricted to mathcalI. The
cardinal invariants mathfrako and mathfrakas may be seen as
particular cases of this class of invariants. In this talk, we will prove that
if the maximum of mathfraka and textsf{cov}$^{ast}left(
mathcal{I}right) isomega_{1}thenmathfrak{a}left( mathcal{I}%
right) =omega_{1}.$ We will obtain some corollaries of this result. This is
part of a joint work with Michael Hruv{s}'{a}k and Osvaldo Tellez.