Perfect and Scattered Subsets of Generalized Cantor Space II

Speaker: 

Geoff Galgon

Institution: 

UCI

Time: 

Monday, October 19, 2015 - 4:00pm to 5:30pm

Location: 

RH 440R

We will initially discuss games played on subsets of the Cantor space, for which the existence or nonexistence of winning strategies for certain players can provide a characterization of perfectness or scatteredness. We will also give an old characterization of the type of trees in 2^{<\omega} through which outer models can add branches. Finally, we will make some observations about the nature of some generalizations of these topics to the 2^{\kappa} spaces.

Perfect and Scattered Subsets of Generalized Cantor Space

Speaker: 

Geoff Galgon

Institution: 

UCI

Time: 

Monday, October 12, 2015 - 4:00pm to 5:30pm

Location: 

440R

We will recall the standard notions of perfect and scattered subsets of 2^{\omega} and give several equivalent characterizations, make some observations, and record some facts. We will then discuss how some natural analogues to these characterizations diverge from one another in the generalized 2^{\kappa} setting. We will make some observations and give some open questions/directions.

Algorithmic randomness for non-uniform probability measures

Speaker: 

Christopher Porter

Institution: 

University of Florida

Time: 

Monday, May 11, 2015 - 4:00pm to 5:30pm

Host: 

Location: 

RH 440R

The primary goal of this talk is to introduce two equivalent definitions of algorithmically random sequences, one given in terms of a specific collection of effective statistical tests (known as Martin-Löf tests) and another given in terms of initial segment complexity (i.e., Kolmogorov complexity). I will explain how these definitions can be generalized to hold for various computable probability measures on Cantor space, and if time permits, I will discuss recent work with Rupert Hölzl and Wolfgang Merkle in which we study the interplay between (i) the growth rate of the initial segment complexity of sequences random with respect to some computable probability measure and (ii) certain properties of this underlying measure (such as continuity vs. discontinuity).  No background in algorithmic randomness will be assumed.

 

Global Chang conjectures and generic supercompactness

Speaker: 

Monroe Eskew

Institution: 

Tsukuba University, Japan

Time: 

Monday, March 9, 2015 - 4:00pm to 5:30pm

Host: 

Location: 

RH 440R

Starting from a 2-huge cardinal, we construct a model where for all pairs of regular cardinals kappa<lambda, (lambda^+,lambda) --> (kappa^+,kappa) and there is a lambda^+ saturated ideal on P_{kappa^+}(lambda).  Then using a modified Radin forcing we get similar global principles involving singular cardinals but with only finite jumps.

 

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