Hausdorff Dimension
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Hausdorff Dimension of Singular Vectors
HAUSDORFF DIMENSION OF SINGULAR VECTORS YITWAH CHEUNG AND NICOLAS CHEVALLIER Abstract. We prove that the set of singular vectors in Rd; d ≥ 2; has Hausdorff dimension d2 d d+1 and that the Hausdorff dimension of the set of "-Dirichlet improvable vectors in R d2 d is roughly d+1 plus a power of " between 2 and d. As a corollary, the set of divergent t t −dt trajectories of the flow by diag(e ; : : : ; e ; e ) acting on SLd+1 R= SLd+1 Z has Hausdorff d codimension d+1 . These results extend the work of the first author in [6]. 1. Introduction Singular vectors were introduced by Khintchine in the twenties (see [14]). Recall that d x = (x1; :::; xd) 2 R is singular if for every " > 0, there exists T0 such that for all T > T0 the system of inequalities " (1.1) max jqxi − pij < and 0 < q < T 1≤i≤d T 1=d admits an integer solution (p; q) 2 Zd × Z. In dimension one, only the rational numbers are singular. The existence of singular vectors that do not lie in a rational subspace was proved by Khintchine for all dimensions ≥ 2. Singular vectors exhibit phenomena that cannot occur in dimension one. For instance, when x 2 Rd is singular, the sequence 0; x; 2x; :::; nx; ::: fills the torus Td = Rd=Zd in such a way that there exists a point y whose distance in the torus to the set f0; x; :::; nxg, times n1=d, goes to infinity when n goes to infinity (see [4], chapter V). -
23. Dimension Dimension Is Intuitively Obvious but Surprisingly Hard to Define Rigorously and to Work With
58 RICHARD BORCHERDS 23. Dimension Dimension is intuitively obvious but surprisingly hard to define rigorously and to work with. There are several different concepts of dimension • It was at first assumed that the dimension was the number or parameters something depended on. This fell apart when Cantor showed that there is a bijective map from R ! R2. The Peano curve is a continuous surjective map from R ! R2. • The Lebesgue covering dimension: a space has Lebesgue covering dimension at most n if every open cover has a refinement such that each point is in at most n + 1 sets. This does not work well for the spectrums of rings. Example: dimension 2 (DIAGRAM) no point in more than 3 sets. Not trivial to prove that n-dim space has dimension n. No good for commutative algebra as A1 has infinite Lebesgue covering dimension, as any finite number of non-empty open sets intersect. • The "classical" definition. Definition 23.1. (Brouwer, Menger, Urysohn) A topological space has dimension ≤ n (n ≥ −1) if all points have arbitrarily small neighborhoods with boundary of dimension < n. The empty set is the only space of dimension −1. This definition is mostly used for separable metric spaces. Rather amazingly it also works for the spectra of Noetherian rings, which are about as far as one can get from separable metric spaces. • Definition 23.2. The Krull dimension of a topological space is the supre- mum of the numbers n for which there is a chain Z0 ⊂ Z1 ⊂ ::: ⊂ Zn of n + 1 irreducible subsets. DIAGRAM pt ⊂ curve ⊂ A2 For Noetherian topological spaces the Krull dimension is the same as the Menger definition, but for non-Noetherian spaces it behaves badly. -
Dimension and Dimensional Reduction in Quantum Gravity
May 2017 Dimension and Dimensional Reduction in Quantum Gravity S. Carlip∗ Department of Physics University of California Davis, CA 95616 USA Abstract , A number of very different approaches to quantum gravity contain a common thread, a hint that spacetime at very short distances becomes effectively two dimensional. I review this evidence, starting with a discussion of the physical meaning of “dimension” and concluding with some speculative ideas of what dimensional reduction might mean for physics. arXiv:1705.05417v2 [gr-qc] 29 May 2017 ∗email: [email protected] 1 Why Dimensional Reduction? What is the dimension of spacetime? For most of physics, the answer is straightforward and uncontroversial: we know from everyday experience that we live in a universe with three dimensions of space and one of time. For a condensed matter physicist, say, or an astronomer, this is simply a given. There are a few exceptions—surface states in condensed matter that act two-dimensional, string theory in ten dimensions—but for the most part dimension is simply a fixed, and known, external parameter. Over the past few years, though, hints have emerged from quantum gravity suggesting that the dimension of spacetime is dynamical and scale-dependent, and shrinks to d 2 at very small ∼ distances or high energies. The purpose of this review is to summarize this evidence and to discuss some possible implications for physics. 1.1 Dimensional reduction and quantum gravity As early as 1916, Einstein pointed out that it would probably be necessary to combine the newly formulated general theory of relativity with the emerging ideas of quantum mechanics [1]. -
The Small Inductive Dimension Can Be Raised by the Adjunction of a Single Point
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector MATHEMATICS THE SMALL INDUCTIVE DIMENSION CAN BE RAISED BY THE ADJUNCTION OF A SINGLE POINT BY ERIC K. VAN DOUWEN (Communicated by Prof. R. TIBXMAN at the meeting of June 30, 1973) Unless otherwise indicated, all spaces are metrizable. 1. INTRODUCTION In this note we construct a metrizable space P containing a point p such that ind P\@} = 0 and yet ind P = 1, thus showing that the small inductive dimension of a metrizable space can be raised by the adjunction of a single point. (Without the metrizsbility condition such on example has already been constructed by Dowker [3, p. 258, exercise Cl). So the behavior of the small inductive dimension is in contrast with that of the dimension functions Ind and dim, which, as is well known, cannot be raised by the edjunction of a single point [3, p. 274, exercises B and C]. The construction of our example stems from the proof of the equality of ind and Ind on the class of separable metrizable spaces, as given in [lo, p. 1781. We make use of the fact that there exists a metrizable space D with ind D = 0 and Ind D = 1 [ 141. This space is completely metrizable. Hence our main example, and the two related examples, also are com- pletely metrizable. Following [7, p, 208, example 3.3.31 the example is used to show that there is no finite closed sum theorem for the small inductive dimension, even on the class of metrizable spaces. -
Metrizable Spaces Where the Inductive Dimensions Disagree
TRANSACTIONS OF THE AMERICAN MATHEMATICALSOCIETY Volume 318, Number 2, April 1990 METRIZABLE SPACES WHERE THE INDUCTIVE DIMENSIONS DISAGREE JOHN KULESZA Abstract. A method for constructing zero-dimensional metrizable spaces is given. Using generalizations of Roy's technique, these spaces can often be shown to have positive large inductive dimension. Examples of N-compact, complete metrizable spaces with ind = 0 and Ind = 1 are provided, answering questions of Mrowka and Roy. An example with weight c and positive Ind such that subspaces with smaller weight have Ind = 0 is produced in ZFC. Assuming an additional axiom, for each cardinal X a space of positive Ind with all subspaces with weight less than A strongly zero-dimensional is constructed. I. Introduction There are three classical notions of dimension for a normal topological space X. The small inductive dimension, denoted ind(^T), is defined by ind(X) = -1 if X is empty, ind(X) < n if each p G X has a neighborhood base of open sets whose boundaries have ind < n - 1, and ind(X) = n if ind(X) < n and n is as small as possible. The large inductive dimension, denoted Ind(Jf), is defined by Ind(X) = -1 if X is empty, \t\c\(X) < n if each closed C c X has a neighborhood base of open sets whose boundaries have Ind < n — 1, and Ind(X) = n if Ind(X) < n and n is as small as possible. The covering dimension, denoted by dim(X), is defined by dim(A') = -1 if X is empty, dim(A') < n if for each finite open cover of X there is a finite open refining cover such that no point is in more than n + 1 of the sets in the refining cover and, dim(A") = n if dim(X) < n and n is as small as possible. -
Quasiorthogonal Dimension
Quasiorthogonal Dimension Paul C. Kainen1 and VˇeraK˚urkov´a2 1 Department of Mathematics and Statistics, Georgetown University Washington, DC, USA 20057 [email protected] 2 Institute of Computer Science, Czech Academy of Sciences Pod Vod´arenskou vˇeˇz´ı 2, 18207 Prague, Czech Republic [email protected] Abstract. An interval approach to the concept of dimension is pre- sented. The concept of quasiorthogonal dimension is obtained by relax- ing exact orthogonality so that angular distances between unit vectors are constrained to a fixed closed symmetric interval about π=2. An ex- ponential number of such quasiorthogonal vectors exist as the Euclidean dimension increases. Lower bounds on quasiorthogonal dimension are proven using geometry of high-dimensional spaces and a separate argu- ment is given utilizing graph theory. Related notions are reviewed. 1 Introduction The intuitive concept of dimension has many mathematical formalizations. One version, based on geometry, uses \right angles" (in Greek, \ortho gonia"), known since Pythagoras. The minimal number of orthogonal vectors needed to specify an object in a Euclidean space defines its orthogonal dimension. Other formalizations of dimension are based on different aspects of space. For example, a topological definition (inductive dimension) emphasizing the recur- sive character of d-dimensional objects having d−1-dimensional boundaries, was proposed by Poincar´e,while another topological notion, covering dimension, is associated with Lebesgue. A metric-space version of dimension was developed -
A Metric on the Moduli Space of Bodies
A METRIC ON THE MODULI SPACE OF BODIES HAJIME FUJITA, KAHO OHASHI Abstract. We construct a metric on the moduli space of bodies in Euclidean space. The moduli space is defined as the quotient space with respect to the action of integral affine transformations. This moduli space contains a subspace, the moduli space of Delzant polytopes, which can be identified with the moduli space of sym- plectic toric manifolds. We also discuss related problems. 1. Introduction An n-dimensional Delzant polytope is a convex polytope in Rn which is simple, rational and smooth1 at each vertex. There exists a natu- ral bijective correspondence between the set of n-dimensional Delzant polytopes and the equivariant isomorphism classes of 2n-dimensional symplectic toric manifolds, which is called the Delzant construction [4]. Motivated by this fact Pelayo-Pires-Ratiu-Sabatini studied in [14] 2 the set of n-dimensional Delzant polytopes Dn from the view point of metric geometry. They constructed a metric on Dn by using the n-dimensional volume of the symmetric difference. They also studied the moduli space of Delzant polytopes Den, which is constructed as a quotient space with respect to natural action of integral affine trans- formations. It is known that Den corresponds to the set of equivalence classes of symplectic toric manifolds with respect to weak isomorphisms [10], and they call the moduli space the moduli space of toric manifolds. In [14] they showed that, the metric space D2 is path connected, the moduli space Den is neither complete nor locally compact. Here we use the metric topology on Dn and the quotient topology on Den. -
Lectures on Fractal Geometry and Dynamics
Lectures on fractal geometry and dynamics Michael Hochman∗ June 27, 2012 Contents 1 Introduction 2 2 Preliminaries 3 3 Dimension 4 3.1 A family of examples: Middle-α Cantor sets . 4 3.2 Minkowski dimension . 5 3.3 Hausdorff dimension . 9 4 Using measures to compute dimension 14 4.1 The mass distribution principle . 14 4.2 Billingsley's lemma . 15 4.3 Frostman's lemma . 18 4.4 Product sets . 22 5 Iterated function systems 25 5.1 The Hausdorff metric . 25 5.2 Iterated function systems . 27 5.3 Self-similar sets . 32 5.4 Self-affine sets . 36 6 Geometry of measures 40 6.1 The Besicovitch covering theorem . 40 6.2 Density and differentiation theorems . 45 6.3 Dimension of a measure at a point . 50 6.4 Upper and lower dimension of measures . 52 ∗Send comments to [email protected] 1 6.5 Hausdorff measures and their densities . 55 7 Projections 59 7.1 Marstrand's projection theorem . 60 7.2 Absolute continuity of projections . 63 7.3 Bernoulli convolutions . 65 7.4 Kenyon's theorem . 71 8 Intersections 74 8.1 Marstrand's slice theorem . 74 8.2 The Kakeya problem . 77 9 Local theory of fractals 79 9.1 Microsets and galleries . 80 9.2 Symbolic setup . 81 9.3 Measures, distributions and measure-valued integration . 82 9.4 Markov chains . 83 9.5 CP-processes . 85 9.6 Dimension and CP-distributions . 88 9.7 Constructing CP-distributions supported on galleries . 90 9.8 Spectrum of an Markov chain . -
New Methods for Estimating Fractal Dimensions of Coastlines
New Methods for Estimating Fractal Dimensions of Coastlines by Jonathan David Klotzbach A Thesis Submitted to the Faculty of The College of Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida May 1998 New Methods for Estimating Fractal Dimensions of Coastlines by Jonathan David Klotzbach This thesis was prepared under the direction of the candidate's thesis advisor, Dr. Richard Voss, Department of Mathematical Sciences, and has been approved by the members of his supervisory committee. It was submitted to the faculty of The College of Science and was accepted in partial fulfillment of the requirements for the degree of Master of Science. SUPERVISORY COMMITTEE: ~~~y;::ThesisAMo/ ~-= Mathematical Sciences Date 11 Acknowledgements I would like to thank my advisor, Dr. Richard Voss, for all of his help and insight into the world of fractals and in the world of computer programming. You have given me guidance and support during this process and without you, this never would have been completed. You have been an inspiration to me. I would also like to thank my committee members, Dr. Heinz- Otto Peitgen and Dr. Mingzhou Ding, for their help and support. Thanks to Rich Roberts, a graduate student in the Geography Department at Florida Atlantic University, for all of his help converting the data from the NOAA CD into a format which I could use in my analysis. Without his help, I would have been lost. Thanks to all of the faculty an? staff in the Math Department who made my stay here so enjoyable. -
Zerodimensional Spaces* Jr Isbell
ZERODIMENSIONAL SPACES* J.R. ISBELL (Received February 1, 1955) Introduction. This paper contains some topological results principally concerning zero-dimensional spaces. We observe first that the dimension of a uniform space can be so defined that invariance under completion is trivial. Katetov's result [10], that the covering dimension of normal spaces is preserved under Stone-Cech compactification, follows as a corollary. We obtain sharper results in the zero-dimensional case, including a repre- sentation of the completion of uX as the structure space of the Boolean algebra of uniformly continuous functions on uX to the two-element field. An example shows that inductive dimension zero need not be pre- served under Stone-Cech compactification. The concluding section of the paper answers three questions raised in [9], by counterexamples, and contributes some propositions in continua- tion. Two of the examples were communicated by Professor V. L. Klee. Others who have had a hand in the paper are M. Henriksen, T. Shirota, and H. Trotter, in the counterexamples, and especially S. Ginsburg. The paper grew out of our collaboration [5] with Professor Ginsburg, which involves closely related ideas. 1. Dimension and Completion. The term dimension, unqualified, will refer to the Menger-Urysohn inductive dimension [8]. The Lebesgue covering dimension is known to coincide for metric spaces [11]. We define below two "covering" dimensions for uniform spaces. In this connection we note the special uniformities f and a [18, 14] consisting of all normal coverings having finite resp. countable normal subcoverings. For any uniformity u, the finite coverings in u define a uniformity fu. -
On the Computation of the Hausdorff Dimension of the Walrasian Economy:Further Notes
Munich Personal RePEc Archive On the Computation of the Hausdorff Dimension of the Walrasian Economy:Further Notes Dominique, C-Rene Independent Research 9 August 2009 Online at https://mpra.ub.uni-muenchen.de/16723/ MPRA Paper No. 16723, posted 10 Aug 2009 10:42 UTC ON THE COMPUTATION OF THE HAUSDORFF DIMENSION OF THE WALRASIAN ECONOMY: FURTHER NOTES C-René Dominique* ABSTRACT: In a recent paper, Dominique (2009) argues that for a Walrasian economy with m consumers and n goods, the equilibrium set of prices becomes a fractal attractor due to continuous destructions and creations of excess demands. The paper also posits that the Hausdorff dimension of the attractor is d = ln (n) / ln (n-1) if there are n copies of sizes (1/(n-1)), but that assumption does not hold. This note revisits the problem, demonstrates that the Walrasian economy is indeed self-similar and recomputes the Hausdorff dimensions of both the attractor and that of a time series of a given market. KEYWORDS: Fractal Attractor, Contractive Mappings, Self-similarity, Hausdorff Dimensions of the Walrasian Economy, the Hausdorff dimension of a time series of a given market. INTRODUCTION Dominique (2009) has shown that the equilibrium price vector of a Walrasian pure exchange economy is a closed invariant set E* Rn-1 (where R is the set of real numbers and n-1 are the number of independent prices) rather than the conventionally assumed stationary fixed point. And that the Hausdorff dimension of the attractor lies between one and two if n self-similar copies of the economy can be made. -
Dimensions of Self-Similar Fractals
DIMENSIONS OF SELF-SIMILAR FRACTALS BY MELISSA GLASS A Thesis Submitted to the Graduate Faculty of WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES in Partial Fulfillment of the Requirements for the Degree of MASTER OF ARTS Mathematics May 2011 Winston-Salem, North Carolina Approved By: Sarah Raynor, Ph.D., Advisor James Kuzmanovich, Ph.D., Chair Jason Parsley, Ph.D. Acknowledgments First and foremost, I would like to thank God for making me who I am, for His guidance, and for giving me the strength and ability to write this thesis. Second, I would like to thank my husband Andy for all his love, support and patience even on the toughest days. I appreciate the countless dinners he has made me while I worked on this thesis. Next, I would like to thank Dr. Raynor for all her time, knowledge, and guidance throughout my time at Wake Forest. I would also like to thank her for pushing me to do my best. A special thank you goes out to Dr. Parsley for putting up with me in class! I also appreciate him serving as one of my thesis committee members. I also appreciate all the fun conversations with Dr. Kuzmanovich whether it was about mathematics or mushrooms! Also, I would like to thank him for serving as one of my thesis committee members. A thank you is also in order for all the professors at Wake Forest who have taught me mathematics. ii Table of Contents Acknowledgments . ii List of Figures. v Abstract . vi Chapter 1 Introduction . 1 1.1 Motivation .