Nowhere precipitousness of some ideals

In this paper we will present a simple condition for an ideal to be nowhere precipitous. Through this condition we show nowhere precipitousness of fundamental ideals on Pkλ, in particular the non-stationary ideal NSkλ under cardinal arithmetic assumptions.In this section I denotes a non-principal ideal on an infinite set A. Let I+ = PA / I (ordered by inclusion as a forcing notion) and I∣X = {Y ⊂ A: Y ⋂ X ∈ I}, which is also an ideal on A for X ∈ I+. We refer the reader to [8, Section 35] for the general theory of generic ultrapowers associated with an ideal. We recall I is said to be precipitous if ⊨I+ “Ult(V, Ġ) is well-founded” [9].The central notion of this paper is a strong negation of precipitousness [1]:Definition. I is nowhere precipitous if I∣X is not precipitous for every X ∈ I+ i.e., ⊨I+ “Ult(V, Ġ) is ill-founded.”It is useful to characterize nowhere precipitousness in terms of infinite games (see [11, Section 27]). Consider the following game G(I) between two players, Nonempty and Empty [5]. Nonempty and Empty alternately choose Xn ∈ I+ and Yn ∈ I+ respectively so that Xn ⊃ Yn ⊃n+1. After ω moves, Empty wins the game if⋂n<ωXn=⋂n<ωYn = Ø.See [5, Theorem 2] for a proof of the following characterization.Proposition. I is nowhere precipitous if and only if Empty has a winning strategy in G(I).

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Determinacy of Banach games

Journal of Symbolic Logic ◽

10.2307/2273794 ◽

1985 ◽

Vol 50 (1) ◽

pp. 110-122

Author(s):

Howard Becker

Keyword(s):

Winning Strategy ◽

Similar Type ◽

Infinite Games ◽

Real Numbers ◽

Positive Real ◽

Infinite Game ◽

First Time

For any A ⊂ R, the Banach game B(A) is the following infinite game on reals: Players I and II alternately play positive real numbers a1; a2, a3, a4,… such that for n > 1, an < an−1. Player I wins iff ai exists and is in A.This type of game was introduced by Banach in 1935 in the Scottish Book [15], Problem 43. The (rather vague) problem which Banach posed was to characterize those sets A for which I (II) has a winning strategy in B(A). (There are three parts to Problem 43. In the first, Mazur defined a game G**(A) for every set A ⊂ R and conjectured that II has a winning strategy in G**(A) iff A is meager and I has a winning strategy in G**(A) iff A is comeager in some neighborhood; this conjecture was proved by Banach. Presumably Banach had this result in mind when he asked the question about B(A), and hoped for a similar type of characterization.) Incidentally, Problem 43 of the Scottish Book appears to be the first time infinite games of any sort were studied by mathematicians.This paper will not provide the reader with any answer to Banach's question. I know of no nontrivial way to characterize when player I (or II) wins, and I suspect there is none. This paper is concerned with a different (also rather vague) question: For which sets A is the Banach game B(A) determined? To say that B(A) is determined means, of course, that one of the players has a winning strategy for B(A).

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Dummetova koncepcija kao teorija značenja za Hintikkin tip semantike teorije igre (III)

Papers on Philosophy Psychology Sociology and Pedagogy ◽

10.15291/radovifpsp.2709 ◽

2018 ◽

Vol 30 (7) ◽

Author(s):

Heda Festini

Keyword(s):

General Theory ◽

Information Seeking ◽

Proof Theory ◽

Winning Strategy ◽

General Information ◽

Language Games ◽

Inductive Probability ◽

Theory Of Meaning ◽

The Difference ◽

Key Terms

With the analysis of the key terms such as truth/use, proof - verification, falsification, inductive probability/semantic probability, winning/losing, winning strategy, it is shown that Dummett’s general theory of meaning does not include Hintikka’s game theory, that it, the conception of the winning strategy. The difference between them arises from the different understanding of Wittgenstein's idea about language games and from their attitudes toward theoretical proof theory. Hintikka’s semantic games about exploration of the world do not reject the bivalence principle but he gives it a different characteristic - one of the two players always has a winning strategy. Looking at Dummett’s philosophical theory of meaning and the most recent Hintikka’s suggestion about general information - seeking through questioning and answering, the author establishes that Dummett’s falsificational and dialogical games as well as Hintikka’s semantic games are subparts of Hintikka’s general information - seeking game Thus Dummett’s statement that Hintikka’s semantic games can be subsumed under Dummett’s conception is rejected and thus the answer is partly given to Saarinen’s suggestion that new affinity should be established. Apart from the comparison of these views with the outline of possible Wittgenstein’s general theory of meaning as rule - testing, together with his treatment (although not always adequate) of verification/falsification, inductive probability and čonfirmation/corroboration, the advantage of Wittgenstein’s view is affirmed.

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Some weak covering properties and infinite games

Open Mathematics ◽

10.2478/s11533-013-0343-4 ◽

2014 ◽

Vol 12 (2) ◽

Cited By ~ 1

Author(s):

Masami Sakai

Keyword(s):

Winning Strategy ◽

Affirmative Answer ◽

Infinite Games ◽

Menger Space ◽

Selection Principle ◽

Covering Properties

AbstractWe show that (I) there is a Lindelöf space which is not weakly Menger, (II) there is a Menger space for which TWO does not have a winning strategy in the game Gfin(O,Do). These affirmatively answer questions posed in Babinkostova, Pansera and Scheepers [Babinkostova L., Pansera B.A., Scheepers M., Weak covering properties and infinite games, Topology Appl., 2012, 159(17), 3644–3657]. The result (I) automatically gives an affirmative answer of Wingers’ problem [Wingers L., Box products and Hurewicz spaces, Topology Appl., 1995, 64(1), 9–21], too. The selection principle S1(Do,Do) is also discussed in view of a special base. We show that every subspace of a hereditarily Lindelöf space with an ortho-base satisfies S1(Do,Do).

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Random Fourier series on compact abelian hypergroups

Journal of the Australian Mathematical Society. Series A. Pure Mathematics and Statistics ◽

10.1017/s1446788700021741 ◽

1984 ◽

Vol 37 (1) ◽

pp. 45-81 ◽

Cited By ~ 7

Author(s):

John J. F. Fournier ◽

Kenneth A. Ross

Keyword(s):

Fourier Series ◽

General Theory ◽

Conjugacy Classes ◽

Sufficient Condition ◽

Simple Condition ◽

Entropy Condition ◽

Dual Object ◽

Random Fourier Series

AbstractRandom Fourier series are studied for a class of compact abelian hypergroups. The randomizing factors are assumed to be independent and uniformly subgaussian. In the presence of a natural teachnical hypothesis, an entropy condition of Dudley is shown to be sufficient for almost sure continuity. The classical results on almost sure membership in Lp, where p < ∞, are generalized to this setting. As an application, it is shown that a simple condition on the dual object implies that the de Leeuw-Kahane-Katznelson phenomenon occurs. Another application is the analogue of a classical sufficient condition for almost sure continuity. Examples illustrating the general theory are given for the hypergroup of conjugacy classes of SU(2) and for a class of compact countable hypergroups.

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Weakly compact cardinals in models of set theory

Journal of Symbolic Logic ◽

10.2307/2274236 ◽

1985 ◽

Vol 50 (2) ◽

pp. 476-486

Author(s):

Ali Enayat

Keyword(s):

Set Theory ◽

Countable Model ◽

Weakly Compact ◽

Uncountable Cardinal ◽

Power Set ◽

Central Notion ◽

Countable Compactness ◽

Omitting Types ◽

Models Of Set Theory ◽

Generic Ultrapowers

The central notion of this paper is that of a κ-elementary end extension of a model of set theory. A model is said to be a κ-elementary end extension of a model of set theory if > and κ, which is a cardinal of , is end extended in the passage from to , i.e., enlarges κ without enlarging any of its members (see §0 for more detail). This notion was implicitly introduced by Scott in [Sco] and further studied by Keisler and Morley in [KM], Hutchinson in [H] and recently by the author in [E]. It is not hard to see that if has a κ-elementary end extension then κ must be regular in . Keisler and Morley [KM] noticed that this has a converse if is countable, i.e., if κ is a regular cardinal of a countable model then has a κ-elementary end extension. Later Hutchinson [H] refined this result by constructing κ-elementary end extensions 1 and 2 of an arbitrary countable model in which κ is a regular uncountable cardinal, such that 1 adds a least new element to κ while 2 adds no least new ordinal to κ. It is a folklore fact of model theory that the Keisler-Morley result gives soft and short proofs of countable compactness and abstract completeness (i.e. recursive enumera-bility of validities) of the logic L(Q), studied extensively in Keisler's [K2]; and Hutchinson's refinement does the same for stationary logic L(aa), studied by Barwise et al. in [BKM]. The proof of Keisler-Morley and that of Hutchinson make essential use of the countability of since they both rely on the Henkin-Orey omitting types theorem. As pointed out in [E, Theorem 2.12], one can prove these theorems using “generic” ultrapowers just utilizing the assumption of countability of the -power set of κ. The following result, appearing as Theorem 2.14 in [E], links the notion of κ-elementary end extension to that of measurability of κ. The proof using (b) is due to Matti Rubin.

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Concerning n-tactics in the countable-finite game

Journal of Symbolic Logic ◽

10.2178/jsl/1183743727 ◽

1991 ◽

Vol 56 (3) ◽

pp. 786-794 ◽

Cited By ~ 1

Author(s):

Marion Scheepers

Keyword(s):

Positive Integer ◽

Set Theory ◽

Winning Strategy ◽

Perfect Information ◽

Information Strategy ◽

Finite Game ◽

Finite Set ◽

The Axiom Of Choice ◽

Infinite Set ◽

Special Case

In the paper [S1] I introduced a game, denoted by MG(J) (where J is a free ideal on some infinite set S) and called “the meager nowhere dense game for J”. The special case when J is the collection of finite subsets of the set S is called the countable-finite game on S. It proceeds as follows.First player ONE picks a countable set C1, then player TWO picks a finite set F1. Then in the second inning ONE picks a countable set C2 with C1 ⊂ C2 (unless explicitly indicated otherwise, “⊂” means “is a proper subset of”) and TWO responds with a finite set F2, and so on. The players construct a sequence (C1,F1,C2,F2,…,Ck,Fk,…) where for each positive integer k(i) Ck denotes ONE's countable set picked during the kth inning,(ii) Fk denotes TWO's finite set picked during the kth inning, and(iii) Ck ⊂ Ck + 1.Such a sequence is a play of the countable-finite game on S, and TWO wins this play if is contained in . The notion of a winning perfect information strategy is defined as usual (see, for example, [S1]). Zermelo-Fraenkel set theory together with the axiom of choice (denoted by ZFC; for a statement of the axioms see pp. xv–xvi of [K]) is a strong enough theory to build a winning perfect information strategy for player TWO in this game.Does TWO have a winning strategy requiring less than perfect information? Fix a positive integer k. A strategy of TWO which requires knowledge of only at the most the k most recent moves of ONE is said to be a k-tactic. For the countable-finite game on an infinite set S the following facts about the existence of winning k-tactics for TWO are proved in [S1]:1) TWO does not have a winning 1-tactic (Theorem 1 of [S1]).2) If the cardinality of S is less than ℵ2 then TWO has a winning 2-tactic (Corollary 4 of [S1]).3) If TWO has a winning k-tactic in the countable-finite game on an infinite set S, then TWO has a winning 3-tactic (Proposition 15 of [SI]).

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Variations on a game of Gale (III): remainder strategies

Journal of Symbolic Logic ◽

10.2307/2275641 ◽

1997 ◽

Vol 62 (4) ◽

pp. 1253-1264 ◽

Cited By ~ 2

Author(s):

Marion Scheepers ◽

William Weiss

Keyword(s):

Positive Integer ◽

Finite Subset ◽

Winning Strategy ◽

Finite Set ◽

Image Position ◽

Infinite Set

An infinite set X is given. D. Gale, in correspondence with J. Mycielski, described the following game in which players one and two play an inning per positive integer: In the nth inning one chooses a finite subset Xn of X, and two chooses a point xn from (X1∪ … ∪Xn)\{x1,…,xn−1}. A playis won by two if . Gale asked whether two could have a winning strategy which depends for each n on knowledge of only the contents of the setIn mathematical terms, is there a function F defined on the collection of finite subsets of X such that:for every sequence X1, x1, …, Xn, xn,…. where each Xn is a finite subsetof X and for each nwe have We shall call a strategy of this sort a remainder strategy for two. If there is some finite subset U of X such that F(U) ∉ U, then F cannot be a winning remainder strategy for two, because one can defeat F by choosing U each inning. So, when studying remainder strategies for two we may as well assume that for each finite set U ⊂ X, F(U) ∈ U.

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Extreme self-sacrifice beyond fusion: Moral expansiveness and the special case of allyship

Behavioral and Brain Sciences ◽

10.1017/s0140525x18001620 ◽

2018 ◽

Vol 41 ◽

Cited By ~ 2

Author(s):

Daniel Crimston ◽

Matthew J. Hornsey

Keyword(s):

General Theory ◽

Biological Markers ◽

Natural Environment ◽

Relevant Dimension ◽

Special Case

AbstractAs a general theory of extreme self-sacrifice, Whitehouse's article misses one relevant dimension: people's willingness to fight and die in support of entities not bound by biological markers or ancestral kinship (allyship). We discuss research on moral expansiveness, which highlights individuals’ capacity to self-sacrifice for targets that lie outside traditional in-group markers, including racial out-groups, animals, and the natural environment.

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