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19
A classification of rapidly growing Ramsey functions
 PROC. AMER. MATH. SOC
, 2003
"... Let f be a numbertheoretic function. A finite set X of natural numbers is called flarge if card(X) ≥ f(min(X)). Let PHf be the Paris Harrington statement where we replace the largeness condition by a corresponding flargeness condition. We classify those functions f for which the statement PHf i ..."
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Let f be a numbertheoretic function. A finite set X of natural numbers is called flarge if card(X) ≥ f(min(X)). Let PHf be the Paris Harrington statement where we replace the largeness condition by a corresponding flargeness condition. We classify those functions f for which the statement PHf is independent of first order (Peano) arithmetic PA.Iffis a fixed iteration of the binary length function, then PHf is independent. On the other hand PHlog ∗ is provable in PA. More precisely let fα(i):=i  H −1 α (i) where  i h denotes the htimes iterated binary length of i and H−1 α denotes the inverse function of the αth member Hα of the Hardy hierarchy. Then PHfα is independent of PA (for α ≤ ε0) iffα = ε0.
On endextensions of models of : exp
 Math. Log. Quart
, 1996
"... Every model of I∆0 is the tally part of a model of the stringlanguage theory ThFO (a main feature of which consists in having induction on notation restricted to certain AC 0 sets). We show how to “smoothly ” introduce in ThFO the binary length function, whereby it is possible to make exponential ..."
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Cited by 4 (1 self)
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Every model of I∆0 is the tally part of a model of the stringlanguage theory ThFO (a main feature of which consists in having induction on notation restricted to certain AC 0 sets). We show how to “smoothly ” introduce in ThFO the binary length function, whereby it is possible to make exponential assumptions in models of ThFO. These considerations entail that every model of I∆0 + ¬exp is a proper initial segment of a model of ThFO and that a modicum of bounded collection is true in these models.
The automorphism group of a countable recursively saturated structure
 Proceedings of the London Mathematical Society, Series 3 , 65:225244
, 1992
"... The automorphism groups of K0categorical structures have been studied extensively by both permutation group theorists and model theorists, and this collaboration has turned out to be very fruitful. (See, for example, [10,6,2].) The notion of a recursively saturated structure generalizes that of a ( ..."
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Cited by 3 (1 self)
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The automorphism groups of K0categorical structures have been studied extensively by both permutation group theorists and model theorists, and this collaboration has turned out to be very fruitful. (See, for example, [10,6,2].) The notion of a recursively saturated structure generalizes that of a (countable)
On Wright’s inductive definition of coherence truth for arithmetic
 Analysis
"... As the first illustration of a potential satisfier for the ‘platitudes for truth ’ in the appendix to his engaging recent discussion of the concept of truth (Wright 1999), Crispin Wright has proposed a notion of ‘truth conceived as coherence ’ for arithmetic. This paper attempts to clarify certain a ..."
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As the first illustration of a potential satisfier for the ‘platitudes for truth ’ in the appendix to his engaging recent discussion of the concept of truth (Wright 1999), Crispin Wright has proposed a notion of ‘truth conceived as coherence ’ for arithmetic. This paper attempts to clarify certain aspects of Wright’s proposal. Take the standard firstorder language of arithmetic L. 1 Let B be some axiom system for arithmetic, which Wright calls the ‘coherence base’. With small notational modifications, Wright proposes the following inductive definition of the concept ‘coheres with B ’ (for Lsentences): (CAt) If ϕ is atomic, then ϕ coheres with B iff B � ϕ. (C¬) ¬ϕ coheres with B iff ϕ does not cohere with B. (C∧) ϕ ∧ ψ coheres with B iff ϕ and ψ cohere with B. (C∨) ϕ ∨ ψ coheres with B iff either ϕ or ψ coheres with B. (C→) ϕ → ψ coheres with B iff either ϕ does not or ψ does cohere with B. (C∀) ∀xϕ coheres with B iff, for each number n, ϕ(n) coheres with B. (C∃) ∃xϕ coheres with B iff, for some number n, ϕ(n) coheres with B. First, note that except for the basis clause (CAt) this is the same as the usual Tarskian inductive definition of truth for arithmetic: 2 (TAt) If ϕ has the form t = u, then ϕ is true iff val(t) = val(u). 3 1 The terms of L are defined recursively from a basis of variables, the constant 0 and the operation symbols s, + and ×. The numerals of L are written n, meaning 0 prefixed by n occurrences of the successor symbol s. The atomic formulas of L are equations of the form t = u (with t, u terms) and complex formulas of L are defined by recursion on complexity as usual. Below, Sent(L) is the set of Lsentences of L, AtSent(L) is the set of atomic Lsentences and Form(L) is the set of Lformulas. In the arithmetic formalization of semantics, we use SentL(x) and ClTmL(x) to mean arithmetic formulas expressing respectively that x is (the code of) a sentence of L or that x is (the code of) a closed term of
Infinite finitely generated fields are biinterpretable with N
"... Using the work of several other mathematicians, principally the results of Poonen refining the work of Pop that algebraic independence is definable within the class of finitely generated fields and of Rumely that the ring of rational integers is uniformly interpreted in global fields, and a theore ..."
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Using the work of several other mathematicians, principally the results of Poonen refining the work of Pop that algebraic independence is definable within the class of finitely generated fields and of Rumely that the ring of rational integers is uniformly interpreted in global fields, and a theorem on the definability of valuations on function fields of curves, we show each infinite finitely generated field considered in the ring language is parametrically biïnterpretable with N. As a consequence, for any finitely generated field there is a firstorder sentence in the language of rings which is true in that field but false in every other finitely generated field, and, hence, Pop’s conjecture that elementarily equivalent finitely generated fields are isomorphic is true.
RANDOM REALS, THE RAINBOW RAMSEY THEOREM, AND ARITHMETIC CONSERVATION
, 2012
"... We investigate the question “To what extent can random reals be used as a tool to establish number theoretic facts? ” Let 2RAN be the principle that for every real X there is a real R which is 2random relative to X. In Section 2, we observe that the arguments of Csima and Mileti [3] can be impleme ..."
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We investigate the question “To what extent can random reals be used as a tool to establish number theoretic facts? ” Let 2RAN be the principle that for every real X there is a real R which is 2random relative to X. In Section 2, we observe that the arguments of Csima and Mileti [3] can be implemented in the base theory RCA0 and so RCA0 + 2RAN implies the Rainbow Ramsey Theorem. In Section 3, we show that the Rainbow Ramsey Theorem is not conservative over RCA0 for arithmetic sentences. Thus, from the CsimaMileti fact that the existence of random reals has infinitarycombinatorial consequences we can conclude that 2RAN has nontrivial arithmetic consequences. In Section 4, we show that 2RAN is conservative over RCA0 + BΣ2 for Π1 1sentences. Thus, the set of firstorder consequences of 2RAN is strictly stronger than P − + I Σ1 and no stronger than P − + BΣ2.
On models constructed by means of the Arithmetized Completeness Theorem
, 2000
"... this paper we will work with a nonstandard model M of PA+ConPA for the language of PA. Since PA is a consistent theory in M, it has a completion C ..."
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this paper we will work with a nonstandard model M of PA+ConPA for the language of PA. Since PA is a consistent theory in M, it has a completion C
Acom" A (Abstract
"... Decentralized systems have existed in nature for thousands of years. Each time you look at a flock of birds in the sky or at ants foraging for food, you witness a decentralized system. They rely of the concept local agent to agent interaction; there is no global communication. This simple local comm ..."
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Decentralized systems have existed in nature for thousands of years. Each time you look at a flock of birds in the sky or at ants foraging for food, you witness a decentralized system. They rely of the concept local agent to agent interaction; there is no global communication. This simple local communication has the capability to expand to many of our existing systems, such as in computer networks. Not only would it be more reliable, but it also has the potential to be more efficient. The future of decentralized systems in our society is promising. This report describes using StarLogo to simulate some simple decentralized systems. The simulations simulate a message traversing through a system of agents and measure message saturation when the message has expired from the system. Individual agents can only receive and send the message for an usercontrollable number of time steps. The results show that for either relatively high densities of agents or for a high number of time steps to retain the message, the message saturation is near 100%. This is exciting information when one considers that parallel uses of these simulations could mimic a network of cell phones or even mimic many tiny robots exploring a distant planet. The applications of using local interactions to perform global tasks are virtually endless. My work will show that simple agents obeying simple rules can lead to grand achievements.