The Role of True Finiteness in the Admissible Recursively Enumerable Degrees

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Publisher : American Mathematical Soc.
ISBN 13 : 0821838857
Total Pages : 114 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis The Role of True Finiteness in the Admissible Recursively Enumerable Degrees by : Noam Greenberg

Download or read book The Role of True Finiteness in the Admissible Recursively Enumerable Degrees written by Noam Greenberg and published by American Mathematical Soc.. This book was released on 2006 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: When attempting to generalize recursion theory to admissible ordinals, it may seem as if all classical priority constructions can be lifted to any admissible ordinal satisfying a sufficiently strong fragment of the replacement scheme. We show, however, that this is not always the case. In fact, there are some constructions which make an essential use of the notion of finiteness which cannot be replaced by the generalized notion of $\alpha$-finiteness. As examples we discuss bothcodings of models of arithmetic into the recursively enumerable degrees, and non-distributive lattice embeddings into these degrees. We show that if an admissible ordinal $\alpha$ is effectively close to $\omega$ (where this closeness can be measured by size or by cofinality) then such constructions maybe performed in the $\alpha$-r.e. degrees, but otherwise they fail. The results of these constructions can be expressed in the first-order language of partially ordered sets, and so these results also show that there are natu

A Hierarchy of Turing Degrees

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Publisher : Princeton University Press
ISBN 13 : 0691199663
Total Pages : 234 pages
Book Rating : 4.6/5 (911 download)

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Book Synopsis A Hierarchy of Turing Degrees by : Rod Downey

Download or read book A Hierarchy of Turing Degrees written by Rod Downey and published by Princeton University Press. This book was released on 2020-06-16 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Alpha]-c.a. functions -- The hierarchy of totally [alpha]-c.a. degrees -- Maximal totally [alpha]-c.a. degrees -- Presentations of left-c.e. reals -- m-topped degrees -- Embeddings of the 1-3-1 lattice -- Prompt permissions.

Invariant Means and Finite Representation Theory of $C^*$-Algebras

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839160
Total Pages : 122 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Invariant Means and Finite Representation Theory of $C^*$-Algebras by : Nathanial Patrick Brown

Download or read book Invariant Means and Finite Representation Theory of $C^*$-Algebras written by Nathanial Patrick Brown and published by American Mathematical Soc.. This book was released on 2006 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various subsets of the tracial state space of a unital C$*$-algebra are studied. The largest of these subsets has a natural interpretation as the space of invariant means. II$ 1$-factor representations of a class of C$*$-algebras considered by Sorin Popa are also studied. These algebras are shown to have an unexpected variety of II$ 1$-factor representations. In addition to developing some general theory we also show that these ideas are related to numerous other problems inoperator algebras.

Finite Sections of Band-Dominated Operators

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Publisher : American Mathematical Soc.
ISBN 13 : 0821840428
Total Pages : 104 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Finite Sections of Band-Dominated Operators by : Steffen Roch

Download or read book Finite Sections of Band-Dominated Operators written by Steffen Roch and published by American Mathematical Soc.. This book was released on 2008 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this text is to review recent advances and to present new results in the numerical analysis of the finite sections method for general band and band-dominated operators. The main topics are the stability of the finite sections method and the asymptotic behavior of singular values. The latter topic is closely related with compactness and Fredholm properties of approximation sequences, and the paper can also serve as an introduction into this remarkable field of numerical analysis. Further the author discusses the behavior of approximation numbers, determinants, essential spectra and essential pseudospectra as well as the localization of pseudomodes of finite sections of band-dominated operators.

On Boundary Interpolation for Matrix Valued Schur Functions

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Publisher : American Mathematical Soc.
ISBN 13 : 0821840479
Total Pages : 122 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis On Boundary Interpolation for Matrix Valued Schur Functions by : Vladimir Bolotnikov

Download or read book On Boundary Interpolation for Matrix Valued Schur Functions written by Vladimir Bolotnikov and published by American Mathematical Soc.. This book was released on 2006 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: A number of interpolation problems are considered in the Schur class of $p\times q$ matrix valued functions $S$ that are analytic and contractive in the open unit disk. The interpolation constraints are specified in terms of nontangential limits and angular derivatives at one or more (of a finite number of) boundary points. Necessary and sufficient conditions for existence of solutions to these problems and a description of all the solutions when these conditions are met is given.The analysis makes extensive use of a class of reproducing kernel Hilbert spaces ${\mathcal{H (S)$ that was introduced by de Branges and Rovnyak. The Stein equation that is associated with the interpolation problems under consideration is analyzed in detail. A lossless inverse scattering problem isalso considered.

The Hilbert Function of a Level Algebra

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839403
Total Pages : 154 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis The Hilbert Function of a Level Algebra by : A. V. Geramita

Download or read book The Hilbert Function of a Level Algebra written by A. V. Geramita and published by American Mathematical Soc.. This book was released on 2007 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Let $R$ be a polynomial ring over an algebraically closed field and let $A$ be a standard graded Cohen-Macaulay quotient of $R$. The authors state that $A$ is a level algebra if the last module in the minimal free resolution of $A$ (as $R$-module) is of the form $R(-s)a$, where $s$ and $a$ are positive integers. When $a=1$ these are also known as Gorenstein algebras. The basic question addressed in this paper is: What can be the Hilbert Function of a level algebra? The authors consider the question in several particular cases, e.g., when $A$ is an Artinian algebra, or when $A$ is the homogeneous coordinate ring of a reduced set of points, or when $A$ satisfies the Weak Lefschetz Property. The authors give new methods for showing that certain functions are NOT possible as the Hilbert function of a level algebra and also give new methods to construct level algebras. In a (rather long) appendix, the authors apply their results to give complete lists of all possible Hilbert functions in the case that the codimension of $A = 3$, $s$ is small and $a$ takes on certain fixed values.

Ramanujan's Forty Identities for the Rogers-Ramanujan Functions

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Publisher : American Mathematical Soc.
ISBN 13 : 082183973X
Total Pages : 110 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Ramanujan's Forty Identities for the Rogers-Ramanujan Functions by : Bruce C. Berndt

Download or read book Ramanujan's Forty Identities for the Rogers-Ramanujan Functions written by Bruce C. Berndt and published by American Mathematical Soc.. This book was released on 2007 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sir Arthur Conan Doyle's famous fictional detective Sherlock Holmes and his sidekick Dr. Watson go camping and pitch their tent under the stars. During the night, Holmes wakes his companion and says, ``Watson, look up at the stars and tell me what you deduce.'' Watson says, ``I see millions of stars, and it is quite likely that a few of them are planets just like Earth. Therefore there may also be life on these planets.'' Holmes replies, ``Watson, you idiot. Somebody stole ourtent.'' When seeking proofs of Ramanujan's identities for the Rogers-Ramanujan functions, Watson, i.e., G. N. Watson, was not an ``idiot.'' He, L. J. Rogers, and D. M. Bressoud found proofs for several of the identities. A. J. F. Biagioli devised proofs for most (but not all) of the remaining identities.Although some of the proofs of Watson, Rogers, and Bressoud are likely in the spirit of those found by Ramanujan, those of Biagioli are not. in particular, Biagioli used the theory of modular forms. Haunted by the fact that little progress has been made into Ramanujan's insights on these identities in the past 85 years, the present authors sought ``more natural'' proofs. Thus, instead of a missing tent, we have had missing proofs, i.e., Ramanujan's missing proofs of his forty identities for theRogers-Ramanujan functions. in this paper, for 35 of the 40 identities, the authors offer proofs that are in the spirit of Ramanujan. Some of the proofs presented here are due to Watson, Rogers, and Bressoud, but most are new. Moreover, for several identities, the authors present two or threeproofs. For the five identities that they are unable to prove, they provide non-rigorous verifications based on an asymptotic analysis of the associated Rogers-Ramanujan functions. This method, which is related to the 5-dissection of the generating function for cranks found in Ramanujan's lost notebook, is what Ramanujan might have used to discover several of the more difficult identities. Some of the new methods in this paper can be employed to establish new identities for the Rogers-Ramanujanfunctions.

An Axiomatic Approach to Function Spaces, Spectral Synthesis, and Luzin Approximation

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839837
Total Pages : 112 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis An Axiomatic Approach to Function Spaces, Spectral Synthesis, and Luzin Approximation by : Lars Inge Hedberg

Download or read book An Axiomatic Approach to Function Spaces, Spectral Synthesis, and Luzin Approximation written by Lars Inge Hedberg and published by American Mathematical Soc.. This book was released on 2007 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors define axiomatically a large class of function (or distribution) spaces on $N$-dimensional Euclidean space. The crucial property postulated is the validity of a vector-valued maximal inequality of Fefferman-Stein type. The scales of Besov spaces ($B$-spaces) and Lizorkin-Triebel spaces ($F$-spaces), and as a consequence also Sobolev spaces, and Bessel potential spaces, are included as special cases. The main results of Chapter 1 characterize our spaces by means of local approximations, higher differences, and atomic representations. In Chapters 2 and 3 these results are applied to prove pointwise differentiability outside exceptional sets of zero capacity, an approximation property known as spectral synthesis, a generalization of Whitney's ideal theorem, and approximation theorems of Luzin (Lusin) type.

Tangential Boundary Stabilization of Navier-Stokes Equations

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Publisher : American Mathematical Soc.
ISBN 13 : 0821838741
Total Pages : 146 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Tangential Boundary Stabilization of Navier-Stokes Equations by : Viorel Barbu

Download or read book Tangential Boundary Stabilization of Navier-Stokes Equations written by Viorel Barbu and published by American Mathematical Soc.. This book was released on 2006 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to inject dissipation as to force local exponential stabilization of the steady-state solutions, an Optimal Control Problem (OCP) with a quadratic cost functional over an infinite time-horizon is introduced for the linearized N-S equations. As a result, the same Riccati-based, optimal boundary feedback controller which is obtained in the linearized OCP is then selected and implemented also on the full N-S system. For $d=3$, the OCP falls definitely outside the boundaries of established optimal control theory for parabolic systems with boundary controls, in that the combined index of unboundedness--between the unboundedness of the boundary control operator and the unboundedness of the penalization or observation operator--is strictly larger than $\tfrac{3}{2}$, as expressed in terms of fractional powers of the free-dynamics operator. In contrast, established (and rich) optimal control theory [L-T.2] of boundary control parabolic problems and corresponding algebraic Riccati theory requires a combined index of unboundedness strictly less than 1. An additional preliminary serious difficulty to overcome lies at the outset of the program, in establishing that the present highly non-standard OCP--with the aforementioned high level of unboundedness in control and observation operators and subject, moreover, to the additional constraint that the controllers be pointwise tangential--be non-empty; that is, it satisfies the so-called Finite Cost Condition [L-T.2].

Stability of Spherically Symmetric Wave Maps

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Publisher : American Mathematical Soc.
ISBN 13 : 0821838776
Total Pages : 96 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Stability of Spherically Symmetric Wave Maps by : Joachim Krieger

Download or read book Stability of Spherically Symmetric Wave Maps written by Joachim Krieger and published by American Mathematical Soc.. This book was released on 2006 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a study of Wave Maps from ${\mathbf{R}}^{2+1}$ to the hyperbolic plane ${\mathbf{H}}^{2}$ with smooth compactly supported initial data which are close to smooth spherically symmetric initial data with respect to some $H^{1+\mu}$, $\mu>0$.

Classical Function Theory, Operator Dilation Theory, and Machine Computation on Multiply-Connected Domains

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Publisher : American Mathematical Soc.
ISBN 13 : 0821840460
Total Pages : 176 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Classical Function Theory, Operator Dilation Theory, and Machine Computation on Multiply-Connected Domains by : Jim Agler

Download or read book Classical Function Theory, Operator Dilation Theory, and Machine Computation on Multiply-Connected Domains written by Jim Agler and published by American Mathematical Soc.. This book was released on 2008 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work begins with the presentation of generalizations of the classical Herglotz Representation Theorem for holomorphic functions with positive real part on the unit disc to functions with positive real part defined on multiply-connected domains. The generalized Herglotz kernels that appear in these representation theorems are then exploited to evolve new conditions for spectral set and rational dilation conditions over multiply-connected domains. These conditions form the basis for the theoretical development of a computational procedure for probing a well-known unsolved problem in operator theory, the so called rational dilation conjecture. Arbitrary precision algorithms for computing the Herglotz kernels on circled domains are presented and analyzed. These algorithms permit an effective implementation of the computational procedure which results in a machine generated counterexample to the rational dilation conjecture.

Complicial Sets Characterising the Simplicial Nerves of Strict $\omega $-Categories

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Publisher : American Mathematical Soc.
ISBN 13 : 0821841424
Total Pages : 208 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Complicial Sets Characterising the Simplicial Nerves of Strict $\omega $-Categories by : Dominic Verity

Download or read book Complicial Sets Characterising the Simplicial Nerves of Strict $\omega $-Categories written by Dominic Verity and published by American Mathematical Soc.. This book was released on 2008 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary purpose of this work is to characterise strict $\omega$-categories as simplicial sets with structure. The author proves the Street-Roberts conjecture in the form formulated by Ross Street in his work on Orientals, which states that they are exactly the ``complicial sets'' defined and named by John Roberts in his handwritten notes of that title (circa 1978). On the way the author substantially develops Roberts' theory of complicial sets itself and makes contributions to Street's theory of parity complexes. In particular, he studies a new monoidal closed structure on the category of complicial sets which he shows to be the appropriate generalisation of the (lax) Gray tensor product of 2-categories to this context. Under Street's $\omega$-categorical nerve construction, which the author shows to be an equivalence, this tensor product coincides with those of Steiner, Crans and others.

Semisolvability of Semisimple Hopf Algebras of Low Dimension

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839489
Total Pages : 138 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Semisolvability of Semisimple Hopf Algebras of Low Dimension by : Sonia Natale

Download or read book Semisolvability of Semisimple Hopf Algebras of Low Dimension written by Sonia Natale and published by American Mathematical Soc.. This book was released on 2007 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The author proves that every semisimple Hopf algebra of dimension less than $60$ over an algebraically closed field $k$ of characteristic zero is either upper or lower semisolvable up to a cocycle twist.

Invariant Differential Operators for Quantum Symmetric Spaces

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Publisher : American Mathematical Soc.
ISBN 13 : 0821841319
Total Pages : 104 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Invariant Differential Operators for Quantum Symmetric Spaces by : Gail Letzter

Download or read book Invariant Differential Operators for Quantum Symmetric Spaces written by Gail Letzter and published by American Mathematical Soc.. This book was released on 2008 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper studies quantum invariant differential operators for quantum symmetric spaces in the maximally split case. The main results are quantum versions of theorems of Harish-Chandra and Helgason: There is a Harish-Chandra map which induces an isomorphism between the ring of quantum invariant differential operators and the ring of invariants of a certain Laurent polynomial ring under an action of the restricted Weyl group. Moreover, the image of the center under this map is the entire invariant ring if and only if the underlying irreducible symmetric pair is not of four exceptional types. In the process, the author finds a particularly nice basis for the quantum invariant differential operators that provides a new interpretation of difference operators associated to Macdonald polynomials.

Torus Fibrations, Gerbes, and Duality

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Publisher : American Mathematical Soc.
ISBN 13 : 0821840924
Total Pages : 104 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Torus Fibrations, Gerbes, and Duality by : Ron Donagi

Download or read book Torus Fibrations, Gerbes, and Duality written by Ron Donagi and published by American Mathematical Soc.. This book was released on 2008 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Let $X$ be a smooth elliptic fibration over a smooth base $B$. Under mild assumptions, the authors establish a Fourier-Mukai equivalence between the derived categories of two objects, each of which is an $\mathcal{O} DEGREES{\times}$ gerbe over a genus one fibration which is a twisted form

Exponential Genus Problems in One-Relator Products of Groups

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839454
Total Pages : 170 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis Exponential Genus Problems in One-Relator Products of Groups by : Andrew James Duncan

Download or read book Exponential Genus Problems in One-Relator Products of Groups written by Andrew James Duncan and published by American Mathematical Soc.. This book was released on 2007 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exponential equations in free groups were studied initially by Lyndon and Schutzenberger and then by Comerford and Edmunds. Comerford and Edmunds showed that the problem of determining whether or not the class of quadratic exponential equations have solution is decidable, in finitely generated free groups. In this paper the author shows that for finite systems of quadratic exponential equations decidability passes, under certain hypotheses, from the factor groups to free products and one-relator products.

On Necessary and Sufficient Conditions for $L^p$-Estimates of Riesz Transforms Associated to Elliptic Operators on $\mathbb {R}^n$ and Related Estimates

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Publisher : American Mathematical Soc.
ISBN 13 : 0821839411
Total Pages : 102 pages
Book Rating : 4.8/5 (218 download)

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Book Synopsis On Necessary and Sufficient Conditions for $L^p$-Estimates of Riesz Transforms Associated to Elliptic Operators on $\mathbb {R}^n$ and Related Estimates by : Pascal Auscher

Download or read book On Necessary and Sufficient Conditions for $L^p$-Estimates of Riesz Transforms Associated to Elliptic Operators on $\mathbb {R}^n$ and Related Estimates written by Pascal Auscher and published by American Mathematical Soc.. This book was released on 2007 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: This memoir focuses on $Lp$ estimates for objects associated to elliptic operators in divergence form: its semigroup, the gradient of the semigroup, functional calculus, square functions and Riesz transforms. The author introduces four critical numbers associated to the semigroup and its gradient that completely rule the ranges of exponents for the $Lp$ estimates. It appears that the case $p2$ which is new. The author thus recovers in a unified and coherent way many $Lp$ estimates and gives further applications. The key tools from harmonic analysis are two criteria for $Lp$ boundedness, one for $p2$ but in ranges different from the usual intervals $(1,2)$ and $(2,\infty)$.