Selective but not Ramsey

Selective but not Ramsey

We give a partial answer to the following question of Dobrinen: For a given topological Ramsey space R, are the notions of selective for R and Ramsey for R equivalent? Every topological Ramsey space R has an associated notion of Ramsey ultrafilter for R and selective ultrafilter for R (see [1]). If R is taken to be the Ellentuck space then the two concepts reduce to the familiar notions of Rams...

not intervention but participation

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trigeminal neuralgia-divided but not classified

State-selective Rabi and Ramsey magnetic resonance line shapes

We carry out state-selective Rabi and Ramsey magnetic-resonance experiments on ground-state Cs(F54) atoms. Novel line shapes are obtained, which exhibit very sharp features with a width much smaller than the inverse duration of the magnetic-resonance pulse. The sensitivity of ordinary magnetic-resonance experiments with total spin F .1/2 is significantly less than the Heisenberg limit, which ca...

A notion of selective ultrafilter corresponding to topological Ramsey spaces

We introduce the relation of almost-reduction in an arbitrary topological Ramsey space R as a generalization of the relation of almostinclusion on N[∞]. This leads us to a type of ultrafilter U on the set of first approximations of the elements of R which corresponds to the well-known notion of selective ultrafilter on N. The relationship turns out to be rather exact in the sense that it permit...