ar X iv : m at h / 97 10 21 7 v 1 [ m at h . L O ] 1 5 O ct 1 99 7 Ultrafilters on ω — — their ideals and their cardinal characteristics

ar X iv : m at h / 97 05 22 6 v 1 [ m at h . L O ] 1 5 M ay 1 99 7 On a problem of Steve Kalikow

The Kalikow problem for a pair (λ, κ) of cardinal numbers, λ > κ (in particular κ = 2) is whether we can map the family of ω–sequences from λ to the family of ω–sequences from κ in a very continuous manner. Namely, we demand that for η, ν ∈ ωλ we have: η, ν are almost equal if and only if their images are. We show consistency of the negative answer e.g. for אω but we prove it for smaller cardin...

ar X iv : m at h / 98 10 17 9 v 1 [ m at h . L O ] 3 0 O ct 1 99 8 THE YELLOW CAKE

In this paper we consider the following property: (⊛ Da) For every function f : R × R −→ R there are functions g 0 n , g 1 n : R −→ R (for n < ω) such that (∀x, y ∈ R)(f (x, y) = n<ω g 0 n (x)g 1 n (y)). We show that, despite some expectation suggested by [Sh 675], (⊛ Da) does not imply MA(σ–centered). Next, we introduce cardinal characteristics of the continuum responsible for the failure of (...

ar X iv : a st ro - p h / 97 10 36 7 v 1 3 1 O ct 1 99 7 Geometrical parametrization of warps for edge - on galaxies

ar X iv : m at h / 96 05 21 1 v 1 [ m at h . L O ] 1 4 M ay 1 99 6 COMBINATORIAL PRINCIPLES FROM ADDING COHEN REALS

We first formulate several " combinatorial principles " concerning κ × ω matrices of subsets of ω and prove that they are valid in the generic extension obtained by adding any number of Cohen reals to any ground model V , provided that the parameter κ is an ω-inaccessible regular cardinal in V. Then in section 4 we present a large number of applications of these principles, mainly to topology. ...

ar X iv : h ep - p h / 97 10 22 9 v 1 2 O ct 1 99 7 SLAC - PUB - 7663 October 1997 Z ′ INVESTIGATIONS AT FUTURE LEPTON