Proved for Real Hilbert Spaces. Time Derivatives of Observables and Applications
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Sharp Finiteness Principles for Lipschitz Selections: Long Version
Sharp finiteness principles for Lipschitz selections: long version By Charles Fefferman Department of Mathematics, Princeton University, Fine Hall Washington Road, Princeton, NJ 08544, USA e-mail: [email protected] and Pavel Shvartsman Department of Mathematics, Technion - Israel Institute of Technology, 32000 Haifa, Israel e-mail: [email protected] Abstract Let (M; ρ) be a metric space and let Y be a Banach space. Given a positive integer m, let F be a set-valued mapping from M into the family of all compact convex subsets of Y of dimension at most m. In this paper we prove a finiteness principle for the existence of a Lipschitz selection of F with the sharp value of the finiteness number. Contents 1. Introduction. 2 1.1. Main definitions and main results. 2 1.2. Main ideas of our approach. 3 2. Nagata condition and Whitney partitions on metric spaces. 6 arXiv:1708.00811v2 [math.FA] 21 Oct 2017 2.1. Metric trees and Nagata condition. 6 2.2. Whitney Partitions. 8 2.3. Patching Lemma. 12 3. Basic Convex Sets, Labels and Bases. 17 3.1. Main properties of Basic Convex Sets. 17 3.2. Statement of the Finiteness Theorem for bounded Nagata Dimension. 20 Math Subject Classification 46E35 Key Words and Phrases Set-valued mapping, Lipschitz selection, metric tree, Helly’s theorem, Nagata dimension, Whitney partition, Steiner-type point. This research was supported by Grant No 2014055 from the United States-Israel Binational Science Foundation (BSF). The first author was also supported in part by NSF grant DMS-1265524 and AFOSR grant FA9550-12-1-0425. -
On Relaxation of Normality in the Fuglede-Putnam Theorem
proceedings of the american mathematical society Volume 77, Number 3, December 1979 ON RELAXATION OF NORMALITY IN THE FUGLEDE-PUTNAM THEOREM TAKAYUKIFURUTA1 Abstract. An operator means a bounded linear operator on a complex Hubert space. The familiar Fuglede-Putnam theorem asserts that if A and B are normal operators and if X is an operator such that AX = XB, then A*X = XB*. We shall relax the normality in the hypotheses on A and B. Theorem 1. If A and B* are subnormal and if X is an operator such that AX = XB, then A*X = XB*. Theorem 2. Suppose A, B, X are operators in the Hubert space H such that AX = XB. Assume also that X is an operator of Hilbert-Schmidt class. Then A*X = XB* under any one of the following hypotheses: (i) A is k-quasihyponormal and B* is invertible hyponormal, (ii) A is quasihyponormal and B* is invertible hyponormal, (iii) A is nilpotent and B* is invertible hyponormal. 1. In this paper an operator means a bounded linear operator on a complex Hilbert space. An operator T is called quasinormal if F commutes with T* T, subnormal if T has a normal extension and hyponormal if [ F*, T] > 0 where [S, T] = ST - TS. The inclusion relation of the classes of nonnormal opera- tors listed above is as follows: Normal § Quasinormal § Subnormal ^ Hyponormal; the above inclusions are all proper [3, Problem 160, p. 101]. The familiar Fuglede-Putnam theorem is as follows ([3, Problem 152], [4]). Theorem A. If A and B are normal operators and if X is an operator such that AX = XB, then A*X = XB*. -
Locally Symmetric Submanifolds Lift to Spectral Manifolds Aris Daniilidis, Jérôme Malick, Hristo Sendov
Locally symmetric submanifolds lift to spectral manifolds Aris Daniilidis, Jérôme Malick, Hristo Sendov To cite this version: Aris Daniilidis, Jérôme Malick, Hristo Sendov. Locally symmetric submanifolds lift to spectral mani- folds. 2012. hal-00762984 HAL Id: hal-00762984 https://hal.archives-ouvertes.fr/hal-00762984 Submitted on 17 Dec 2012 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Locally symmetric submanifolds lift to spectral manifolds Aris DANIILIDIS, Jer´ ome^ MALICK, Hristo SENDOV December 17, 2012 Abstract. In this work we prove that every locally symmetric smooth submanifold M of Rn gives rise to a naturally defined smooth submanifold of the space of n × n symmetric matrices, called spectral manifold, consisting of all matrices whose ordered vector of eigenvalues belongs to M. We also present an explicit formula for the dimension of the spectral manifold in terms of the dimension and the intrinsic properties of M. Key words. Locally symmetric set, spectral manifold, permutation, symmetric matrix, eigenvalue. AMS Subject Classification. Primary 15A18, 53B25 Secondary 47A45, 05A05. Contents 1 Introduction 2 2 Preliminaries on permutations 4 2.1 Permutations and partitions . .4 2.2 Stratification induced by the permutation group . -
Hilbert Space Quantum Mechanics
qmd113 Hilbert Space Quantum Mechanics Robert B. Griffiths Version of 27 August 2012 Contents 1 Vectors (Kets) 1 1.1 Diracnotation ................................... ......... 1 1.2 Qubitorspinhalf ................................. ......... 2 1.3 Intuitivepicture ................................ ........... 2 1.4 General d ............................................... 3 1.5 Ketsasphysicalproperties . ............. 4 2 Operators 5 2.1 Definition ....................................... ........ 5 2.2 Dyadsandcompleteness . ........... 5 2.3 Matrices........................................ ........ 6 2.4 Daggeroradjoint................................. .......... 7 2.5 Hermitianoperators .............................. ........... 7 2.6 Projectors...................................... ......... 8 2.7 Positiveoperators............................... ............ 9 2.8 Unitaryoperators................................ ........... 9 2.9 Normaloperators................................. .......... 10 2.10 Decompositionoftheidentity . ............... 10 References: CQT = Consistent Quantum Theory by Griffiths (Cambridge, 2002). See in particular Ch. 2; Ch. 3; Ch. 4 except for Sec. 4.3. 1 Vectors (Kets) 1.1 Dirac notation ⋆ In quantum mechanics the state of a physical system is represented by a vector in a Hilbert space: a complex vector space with an inner product. The term “Hilbert space” is often reserved for an infinite-dimensional inner product space having the property◦ that it is complete or closed. However, the term is often used nowadays, as in these notes, in a way that includes finite-dimensional spaces, which automatically satisfy the condition of completeness. ⋆ We will use Dirac notation in which the vectors in the space are denoted by v , called a ket, where v is some symbol which identifies the vector. | One could equally well use something like v or v. A multiple of a vector by a complex number c is written as c v —think of it as analogous to cv of cv. | ⋆ In Dirac notation the inner product of the vectors v with w is written v w . -
13 the Minkowski Bound, Finiteness Results
18.785 Number theory I Fall 2015 Lecture #13 10/27/2015 13 The Minkowski bound, finiteness results 13.1 Lattices in real vector spaces In Lecture 6 we defined the notion of an A-lattice in a finite dimensional K-vector space V as a finitely generated A-submodule of V that spans V as a K-vector space, where K is the fraction field of the domain A. In our usual AKLB setup, A is a Dedekind domain, L is a finite separable extension of K, and the integral closure B of A in L is an A-lattice in the K-vector space V = L. When B is a free A-module, its rank is equal to the dimension of L as a K-vector space and it has an A-module basis that is also a K-basis for L. We now want to specialize to the case A = Z, and rather than taking K = Q, we will instead use the archimedean completion R of Q. Since Z is a PID, every finitely generated Z-module in an R-vector space V is a free Z-module (since it is necessarily torsion free). We will restrict our attention to free Z-modules with rank equal to the dimension of V (sometimes called a full lattice). Definition 13.1. Let V be a real vector space of dimension n. A (full) lattice in V is a free Z-module of the form Λ := e1Z + ··· + enZ, where (e1; : : : ; en) is a basis for V . n Any real vector space V of dimension n is isomorphic to R . -
Common Cyclic Vectors for Normal Operators 11
COMMON CYCLIC VECTORS FOR NORMAL OPERATORS WILLIAM T. ROSS AND WARREN R. WOGEN Abstract. If µ is a finite compactly supported measure on C, then the set Sµ 2 2 ∞ of multiplication operators Mφ : L (µ) → L (µ),Mφf = φf, where φ ∈ L (µ) is injective on a set of full µ measure, is the complete set of cyclic multiplication operators on L2(µ). In this paper, we explore the question as to whether or not Sµ has a common cyclic vector. 1. Introduction A bounded linear operator S on a separable Hilbert space H is cyclic with cyclic vector f if the closed linear span of {Snf : n = 0, 1, 2, ···} is equal to H. For many cyclic operators S, especially when S acts on a Hilbert space of functions, the description of the cyclic vectors is well known. Some examples: When S is the multiplication operator f → xf on L2[0, 1], the cyclic vectors f are the L2 functions which are non-zero almost everywhere. When S is the forward shift f → zf on the classical Hardy space H2, the cyclic vectors are the outer functions [10, p. 114] (Beurling’s theorem). When S is the backward shift f → (f − f(0))/z on H2, the cyclic vectors are the non-pseudocontinuable functions [9, 16]. For a collection S of operators on H, we say that S has a common cyclic vector f, if f is a cyclic vector for every S ∈ S. Earlier work of the second author [19] showed that the set of co-analytic Toeplitz operators Tφ, with non-constant symbol φ, on H2 has a common cyclic vector. -
Mathematical Work of Franciszek Hugon Szafraniec and Its Impacts
Tusi Advances in Operator Theory (2020) 5:1297–1313 Mathematical Research https://doi.org/10.1007/s43036-020-00089-z(0123456789().,-volV)(0123456789().,-volV) Group ORIGINAL PAPER Mathematical work of Franciszek Hugon Szafraniec and its impacts 1 2 3 Rau´ l E. Curto • Jean-Pierre Gazeau • Andrzej Horzela • 4 5,6 7 Mohammad Sal Moslehian • Mihai Putinar • Konrad Schmu¨ dgen • 8 9 Henk de Snoo • Jan Stochel Received: 15 May 2020 / Accepted: 19 May 2020 / Published online: 8 June 2020 Ó The Author(s) 2020 Abstract In this essay, we present an overview of some important mathematical works of Professor Franciszek Hugon Szafraniec and a survey of his achievements and influence. Keywords Szafraniec Á Mathematical work Á Biography Mathematics Subject Classification 01A60 Á 01A61 Á 46-03 Á 47-03 1 Biography Professor Franciszek Hugon Szafraniec’s mathematical career began in 1957 when he left his homeland Upper Silesia for Krako´w to enter the Jagiellonian University. At that time he was 17 years old and, surprisingly, mathematics was his last-minute choice. However random this decision may have been, it was a fortunate one: he succeeded in achieving all the academic degrees up to the scientific title of professor in 1980. It turned out his choice to join the university shaped the Krako´w mathematical community. Communicated by Qingxiang Xu. & Jan Stochel [email protected] Extended author information available on the last page of the article 1298 R. E. Curto et al. Professor Franciszek H. Szafraniec Krako´w beyond Warsaw and Lwo´w belonged to the famous Polish School of Mathematics in the prewar period. -
The Symmetric Theory of Sets and Classes with a Stronger Symmetry Condition Has a Model
The symmetric theory of sets and classes with a stronger symmetry condition has a model M. Randall Holmes complete version more or less (alpha release): 6/5/2020 1 Introduction This paper continues a recent paper of the author in which a theory of sets and classes was defined with a criterion for sethood of classes which caused the universe of sets to satisfy Quine's New Foundations. In this paper, we describe a similar theory of sets and classes with a stronger (more restrictive) criterion based on symmetry determining sethood of classes, under which the universe of sets satisfies a fragment of NF which we describe, and which has a model which we describe. 2 The theory of sets and classes The predicative theory of sets and classes is a first-order theory with equality and membership as primitive predicates. We state axioms and basic definitions. definition of class: All objects of the theory are called classes. axiom of extensionality: We assert (8xy:x = y $ (8z : z 2 x $ z 2 y)) as an axiom. Classes with the same elements are equal. definition of set: We define set(x), read \x is a set" as (9y : x 2 y): elements are sets. axiom scheme of class comprehension: For each formula φ in which A does not appear, we provide the universal closure of (9A :(8x : set(x) ! (x 2 A $ φ))) as an axiom. definition of set builder notation: We define fx 2 V : φg as the unique A such that (8x : set(x) ! (x 2 A $ φ)). There is at least one such A by comprehension and at most one by extensionality. -
A Note on the Definition of an Unbounded Normal Operator
A NOTE ON THE DEFINITION OF AN UNBOUNDED NORMAL OPERATOR MATTHEW ZIEMKE 1. Introduction Let H be a complex Hilbert space and let T : D(T )(⊆ H) !H be a generally unbounded linear operator. In order to begin the discussion about whether or not the operator T is normal, we need to require that T have a dense domain. This ensures that the adjoint operator T ∗ is defined. In the literature, one sees two definitions for what it means for a densely defined operator T to be normal. The first requires that T be closed and that T ∗T = TT ∗ while the second requires that D(T ) = D(T ∗) and kT xk = kT ∗xk for all x 2 D(T ) = D(T ∗). There is no harm in having these competing definitions as they are, in fact, equivalent. While the equivalence of these statements seems to be widely known, the proof is not obvious, and my efforts to find a detailed and self-contained proof of this fact have left me empty-handed. I attempt to give such a proof here. I also want to note that while we say a bounded linear operator T is normal if and only if T ∗T = TT ∗, the lone requirement of T ∗T = TT ∗ for an unbounded densely defined operator does not, in general, imply T is normal. I used [1] and [2] to write this note. 2. Proof of the equivalence We begin with a definition. Definition 2.1. Let T : D(T )(⊆ H) !H be a densely defined operator. We define the T -inner product on D(T ) × D(T ), denoted as h·; ·iT , by the equation hx; yiT = hx; yi + hT x; T yi; for all x; y 2 D(T ): It is easy to see that the T -inner product is, in fact, an inner product on D(T ). -
Spectral Properties of Structured Kronecker Products and Their Applications
Spectral Properties of Structured Kronecker Products and Their Applications by Nargiz Kalantarova A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Doctor of Philosophy in Combinatorics and Optimization Waterloo, Ontario, Canada, 2019 c Nargiz Kalantarova 2019 Examining Committee Membership The following served on the Examining Committee for this thesis. The decision of the Examining Committee is by majority vote. External Examiner: Maryam Fazel Associate Professor, Department of Electrical Engineering, University of Washington Supervisor: Levent Tun¸cel Professor, Deptartment of Combinatorics and Optimization, University of Waterloo Internal Members: Chris Godsil Professor, Department of Combinatorics and Optimization, University of Waterloo Henry Wolkowicz Professor, Department of Combinatorics and Optimization, University of Waterloo Internal-External Member: Yaoliang Yu Assistant Professor, Cheriton School of Computer Science, University of Waterloo ii I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. iii Statement of contributions The bulk of this thesis was authored by me alone. Material in Chapter5 is related to the manuscript [75] that is a joint work with my supervisor Levent Tun¸cel. iv Abstract We study certain spectral properties of some fundamental matrix functions of pairs of sym- metric matrices. Our study includes eigenvalue inequalities and various interlacing proper- ties of eigenvalues. We also discuss the role of interlacing in inverse eigenvalue problems for structured matrices. Interlacing is the main ingredient of many fundamental eigenvalue inequalities. -
An Intuitive Approach to Normal Operators
An Intuitive Approach to Normal Operators Benoit Dherin, Dan Sparks The question In this short document I will transcribe and slightly modify an e-mail sent to me by Benoit Dherin, which explains how one would be lead to the definition of a normal operator. The usual definitions are: the adjoint T ∗ of T is the unique operator satisfying hTv, wi = hv, T ∗wi for all v, w. A normal operator is one such that T ∗T = TT ∗. The question is, where on earth does this definition come from? Consider the following answers: (1) Because complex numbers satisfy zz = zz. (2) Because operators with an orthonormal eigenbasis satisfy TT ∗ = T ∗T. The reason that these answers do not address the question is because they are inherently unnatural. The point is that complex numbers, and operators with orthonormal eigenbases, have many proper- ties. Not every one of those properties is worth centering a definition around, so there should be a reason to look at normal operators in particular. Groundwork; discovering self-adjoint operators Let V be a finite dimensional complex inner product space. The most natural way to think about L(V) is as a noncommutative ring without unit (or as an analyst might simply say, a ring). The prototype of this type of ring is the set of n × n matrices, which L(V) “is,” up to a non-canonical isomorphism. (For each basis of V, there is an isomorphism L(V) Mn×n(C). Better, for each orthonormal basis of V, there is an isomorphism L(V) Mn×n(C) which respects the norm nicely (c.f. -
Optimal Compression of Approximate Inner Products and Dimension Reduction
Optimal compression of approximate inner products and dimension reduction Noga Alon1 Bo'az Klartag2 Abstract Let X be a set of n points of norm at most 1 in the Euclidean space Rk, and suppose " > 0. An "-distance sketch for X is a data structure that, given any two points of X enables one to recover the square of the (Euclidean) distance between them up to an additive error of ". Let f(n; k; ") denote the minimum possible number of bits of such a sketch. Here we determine f(n; k; ") up to a constant factor for all 1 n ≥ k ≥ 1 and all " ≥ n0:49 . Our proof is algorithmic, and provides an efficient algorithm for computing a sketch of size O(f(n; k; ")=n) for each point, so that the square of the distance between any two points can be computed from their sketches up to an additive error of " in time linear in the length of the sketches. We also discuss p the case of smaller " > 2= n and obtain some new results about dimension reduction log(2+"2n) in this range. In particular, we show that for any such " and any k ≤ t = "2 there are configurations of n points in Rk that cannot be embedded in R` for ` < ck with c a small absolute positive constant, without distorting some inner products (and distances) by more than ". On the positive side, we provide a randomized polynomial time algorithm for a bipartite variant of the Johnson-Lindenstrauss lemma in which scalar products are approximated up to an additive error of at most ".