AN ANALYSIS OF THE MODELS

2019 ◽  
Vol 84 (1) ◽  
pp. 1-26
Author(s):  
RACHID ATMAI

AbstractWe analyze the models $L[T_{2n} ]$, where $T_{2n}$ is a tree on $\omega \times \kappa _{2n + 1}^1 $ projecting to a universal ${\rm{\Pi }}_{2n}^1 $ set of reals, for $n > 1$. Following Hjorth’s work on $L[T_2 ]$, we show that under ${\rm{Det}}\left( {{\rm{}}_{2n}^1 } \right)$, the models $L[T_{2n} ]$ are unique, that is they do not depend of the choice of the tree $T_{2n}$. This requires a generalization of the Kechris–Martin theorem to all pointclasses${\rm{\Pi }}_{2n + 1}^1$. We then characterize these models as constructible models relative to the direct limit of all countable nondropping iterates of${\cal M}_{2n + 1}^\# $. We then show that the GCH holds in $L[T_{2n} ]$, for every $n < \omega $, even though they are not extender models. This analysis localizes the HOD analysis of Steel and Woodin at the even levels of the projective hierarchy.

Author(s):  
B. Hartley ◽  
A. E. Zalesskii

Letqbe a prime power, which will be fixed throughout the paper, letkbe a field, and letbe the field withqelements. LetGn(k)be the general linear groupGL(n, k), andSn(k)the special linear groupSL(n, k). The corresponding groups overwill be denoted simply byGnandSn. We may embedGn(k)inGn+1(k)via the mapForming the direct limit of the resulting system, we obtain thestable general linear groupG∞(k) overk.


1981 ◽  
Vol 46 (2) ◽  
pp. 209-215 ◽  
Author(s):  
Dag Normann

Kleene [7] and Kreisel [8] defined independently the countable (continuous) functionals. Kleene [7] defined the countable functionals of type k to be total functionals of type k acting in a continuous way when restricted to countable arguments of type k − 1. He also defined the associates for countable functionals. They are functions α: N → N containing information about how the functional acts on countable arguments. Kleene [7] showed that the countable functionals are closed under the computations derived from S1–S9 of his paper [6], and that every computable functional has a recursive associate.Kreisel defined the continuous functionals to be equivalence-classes of associates. By his definition it is meaningless to let a continuous functional act upon anything but continuous arguments.One disadvantage of Kleene's approach is that two different functionals may have the same associates We will later see that there may be two functionals φ1 and φ2 with the same associates but such that the relationsare not the same.In more recent papers on the countable functionals it is normal to regard the hierarchy 〈Ct(k)〉kϵN of countable functionals as a type-structure such that the functionals in Ct(k + 1) are maps from Ct(k) to N(Ct(0) = N), see e.g. Bergstra [1] and Gandy and Hyland [3].We will then enjoy the streamlined formalism of a type-structure in which S1–S9 have meaning, but avoid the ambiguities of Kleene's original approach.We will presuppose a brief familiarity with the theory of the countable functionals.


1969 ◽  
Vol 12 (3) ◽  
pp. 337-338 ◽  
Author(s):  
Horst Herrlich

A topological space X is called a direct limit of a family (Xα) of subspaces of X if and only if(1)(2)If X is a direct limit of an increasing sequence (Xn) of closed subspaces then it is well known and easy to prove that X is a T1-space resp. a T4-space provided all Xn are T1-spaces resp. T4-spaces.


1985 ◽  
Vol 28 (1) ◽  
pp. 73-90
Author(s):  
Victor Snaith

Let l be an odd prime and let A be a commutative ring containing 1/l. Let K*(A;Z/lv) denote the mod lv algebraic K-theory of A [3]. As explained in [4] there exists a “Bott element” βv∈K21v–1(l–1)(Z[1/l];Z/lv) and, using the K-theory product we may, following [16, Part IV], formwhich is defined as the direct limit of iterated multiplication by βv. There is a canonical localisation map


1975 ◽  
Vol 27 (3) ◽  
pp. 496-499 ◽  
Author(s):  
Barbara L. Osofsky

Let MR be a right module over the associative ring R (with 1). Assume one has an expression for M as a colimit (direct limit) of a systemover the (directed) poset D. A natural way to get M as a colimit of the family ﹛F∞ —” Fβ|∞, fβ ∈ E﹜ for some subset £ of D is to take E cofinal in D. However, if one is concerned about the cardinality of the set E, cofinal subsets may be too large. Let us look at a specific example. Lazard [3] has shown that any flat MR is a direct limit of finitely generated free R-modules. The cardinality of his indexing set depends on the cardinality of M.


2002 ◽  
Vol 67 (4) ◽  
pp. 1351-1372 ◽  
Author(s):  
Greg Hjorth

We show that the “effective cardinality” of the collection of sets is strictly bigger than the effective cardinality of the . The phrase effective cardinality is vague but can be made exact in the usual ways. For instance:Theorem 1.1. Assume ADL(ℝ)Then in L(ℝ) there is no injection.A few years ago Tony Martin showed a similar result, establishing the non-existence of an injection from to for m sufficiently larger than n. His method did not seem to work for m = n + 1.This present paper gives level by level calculations for the projective hierarchy, but it too falls short of a complete analysis, in as much as it leaves the position of the effective cardinals in the Wadge degrees largely obscure. At the low levels it takes some time for any new cardinals to appear. Whenever Γ1, Γ2 are non-trivial Wadge degrees strictly included in one has.


Author(s):  
Carolyn Nohr ◽  
Ann Ayres

Texts on electron diffraction recommend that the camera constant of the electron microscope be determine d by calibration with a standard crystalline specimen, using the equation


Author(s):  
Kin Lam

The energy of moving ions in solid is dependent on the electronic density as well as the atomic structural properties of the target material. These factors contribute to the observable effects in polycrystalline material using the scanning ion microscope. Here we outline a method to investigate the dependence of low velocity proton stopping on interatomic distances and orientations.The interaction of charged particles with atoms in the frame work of the Fermi gas model was proposed by Lindhard. For a system of atoms, the electronic Lindhard stopping power can be generalized to the formwhere the stopping power function is defined as


Author(s):  
A. Kosiara ◽  
J. W. Wiggins ◽  
M. Beer

A magnetic spectrometer to be attached to the Johns Hopkins S. T. E. M. is under construction. Its main purpose will be to investigate electron interactions with biological molecules in the energy range of 40 KeV to 100 KeV. The spectrometer is of the type described by Kerwin and by Crewe Its magnetic pole boundary is given by the equationwhere R is the electron curvature radius. In our case, R = 15 cm. The electron beam will be deflected by an angle of 90°. The distance between the electron source and the pole boundary will be 30 cm. A linear fringe field will be generated by a quadrupole field arrangement. This is accomplished by a grounded mirror plate and a 45° taper of the magnetic pole.


Author(s):  
N. J. Zaluzec

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation


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