The paper discusses various relationships between the concepts mentioned in the title. In Section 1 Todorcevic functions are shown to arise from both morasses and square. In Section 2 the theme is of supplements to morasses which have some of the flavour of square. Distinctions are drawn between differing concepts. In Section 3 forcing axioms related to the ideas in Section 2 are discussed.

The aim of the paper is to develop the notion of partial probability distributions as being more realistic models of belief systems than the standard accounts. We formulate the theory of partial probability functions independently of any classical semantic notions. We use the partial probability distributions to develop a formal semantics for partial propositional calculi, with extensions to predicate logic and higher order languages. We give a proof theory for the partial logics and obtain soundness and completeness results.

Local connectedness functions for (κ, 1)-simplified morasses, localisations of the coupling function c studied in [M96, §1], are defined and their elementary properties discussed. Several different, useful, canonical ways of arriving at the functions are examined. This analysis is then used to give explicit formulae for generalisations of the local distance functions which were defined recursively in [K00], leading to simple proofs of the principal properties of those functions. It is then extended to the properties of local connectedness functions in (...) the context of κ-M-proper forcing for sucessor κ. The functions are shown to enjoy substantial strengthenings of the properties (particularly the ∆-properties) hitherto proved for both c and for Todorcevic’s ρ-functions in the special case κ = ω1. A couple of examples of the use of local connectedness functions in consort with κ-M-proper forcing are then given. (shrink)

There are simple, purely syntactic axiomatic proof systems for both the logical truths and the logical falsehoods of propositional logic. However, to date no such system has been developed for the logical contingencies, that is, formulas that are both satisfiable and falsifiable. This paper formalizes the purely syntactic axiomatic proof systems for the logical contingencies and proves its soundness as well as completeness.

We prove consistent, assuming there is a supercompact cardinal, that there is a singular strong limit cardinal $\mu$ , of cofinality $\omega$ , such that every $\mu^{+}$ -chromatic graph X on $\mu^{+}$ has an edge colouring c of X into $\mu$ colours for which every vertex colouring g of X into at most $\mu$ many colours has a g-colour class on which c takes every value. The paper also contains some generalisations of the above statement in which $\mu^{+}$ is replaced (...) by other cardinals < $\mu$. (shrink)

We prove consistent, assuming there is a supercompact cardinal, that there is a singular strong limit cardinalμ, of cofinalityω, such that everyμ+-chromatic graphXonμ+has an edge colouringcofXintoμcolours for which every vertex colouringgofXinto at mostμmany colours has ag-colour class on whichctakes every value.The paper also contains some generalisations of the above statement in whichμ+is replaced by other cardinals >μ.

Let µ be a regular cardinal. In this paper I prove two (forcing) existence results concerning structures governed by two parameters, the cardinal µ and an ordinal ρ less than µ+++. The results improve on theorems from [M*2] where the second parameter was always the cardinal µ++.

After a couple of weeks I eventually got around to reading the preprint and started wondering about recasting the argument in my preferred formalism. I arrogantly assumed that this would allow one to smooth out parts of the proof and simplify the details of the definition of the forcing conditions (at the cost of taking the framework set out in §§1,2 below as given). However when I tried to write things down I found myself, to my chagrin, more or less (...) cornered in making my definitions into most of the intricacies that Friedman had been. I suppose that this shows that the original proof is in some sense the natural one (or one of a family of ‘natural’ ones). Nevertheless I obstinately persisted and this note is the result. (shrink)

Dan Talayco has recently defined the gap cohomology group of a tower in p/fin of height ω1. This group is isomorphic to the collection of gaps in the tower modulo the equivalence relation given by two gaps being equivalent if their levelwise symmetric difference is not a gap in the tower, the group operation being levelwise symmetric difference. Talayco showed that the size of this group is always at least 2N0 and that it attains its greatest possible size, 2N1, if (...) ⋄ holds and also in some generic extensions in which CH fails, for example on adding many Cohen or random reals. In this paper it is shown that there is always some tower whose gap cohomology group has size 2N1. It is still open as to whether there are models in which there are towers whose gap cohomology group has size less than 2ω1. (shrink)

κ-M-proper forcing, introduced in [K00] when κ = ω1, is a very powerful new technique for generic stepping up, subsuming all previous generic steppings up using auxiliary functions. A general framework for using κ-M-proper forcing is set out, and a couple of examples of such forcings, adding κ−-thin-very tall scattered spaces and long chains in P(κ) modulo <κ−, are given. These objects are not currently obtainable by the previously known techniques.

This paper concerns the theory of morasses. In the early 1970s Jensen defined (κ,α)-morasses for uncountable regular cardinals κ and ordinals $\alpha . In the early 1980s Velleman defined (κ, 1)-simplified morasses for all regular cardinals κ. He showed that there is a (κ, 1)-simplified morass if and only if there is (κ, 1)-morass. More recently he defined (κ, 2)-simplified morasses and Jensen was able to show that if there is a (κ, 2)-morass then there is a (κ, 2)-simplified morass. (...) In this paper we prove the converse of Jensen's result, i.e., that if there is a (κ, 2)-simplified morass then there is a (κ, 2)-morass. (shrink)

This paper concerns the theory of morasses. In the early 1970s Jensen defined -morasses for uncountable regular cardinals $\kappa$ and ordinals $\alpha < \kappa$. In the early 1980s Velleman defined -simplified morasses for all regular cardinals $\kappa$. He showed that there is a -simplified morass if and only if there is -morass. More recently he defined -simplified morasses and Jensen was able to show that if there is a -morass then there is a -simplified morass. In this paper we prove (...) the converse of Jensen's result, i.e., that if there is a -simplified morass then there is a -morass. (shrink)

This paper concerns the theory of morasses. In the early 1970s Jensen defined -morasses for uncountable regular cardinals $\kappa$ and ordinals $\alpha < \kappa$. In the early 1980s Velleman defined -simplified morasses for all regular cardinals $\kappa$. He showed that there is a -simplified morass if and only if there is -morass. More recently he defined -simplified morasses and Jensen was able to show that if there is a -morass then there is a -simplified morass. In this paper we prove (...) the converse of Jensen's result, i.e., that if there is a -simplified morass then there is a -morass. (shrink)

We show that a $$ -simplified morass can be added by a forcing with working parts of size smaller than $\kappa $. This answers affirmatively the question, asked independently by Shelah and Velleman in the early 1990s, of whether it is possible to do so.Our argument use a modification of a technique of Mitchell’s for adding objects of size $\omega _2$ in which collections of models – all of equal, countable size – are used as side conditions. In our modification, (...) whilst the individual models are, as in Mitchell’s technique, taken ad hoc from quite general classes, the collections of models are very highly structured, in a way that is somewhat different from, perhaps more stringent than, Mitchell’s original, arguably making the method more wieldy and giving the prospect of further uses with more delicate working parts. (shrink)

is a (κ, 1)-simplified morass if θα | α < κ is an increasing sequence of ordinals less than κ, θκ = κ+, and each Fαβ is a collection of maps from θα to θβ such that the following properties hold.