scholarly journals On Fourier transform multipliers in Lp

1972 ◽  
Vol 13 (2) ◽  
pp. 219-223
Author(s):  
G. O. Okikiolu
Keyword(s):  
Fourier Transform ◽  
Euclidean Space ◽  
Characteristic Function ◽  
Lebesgue Measure ◽  
Real Numbers ◽  
Measurable Functions ◽  
Image Position

We denote by R the set of real numbers, and by Rn, n ≧ 2, the Euclidean space of dimension n. Given any subset E of Rn, n ≧ 1, we denote the characteristic function of E by xE, so that XE(x) = 0 if x ∈ E; and XE(X) = 0 if x ∈ Rn/E.The space L(Rn) Lp consists of those measurable functions f on Rn such that is finite. Also, L∞ represents the space of essentially bounded measurable functions with ║f║>0; m({x: |f(x)| > x}) = O}, where m represents the Lebesgue measure on Rn The numbers p and p′ will be connected by l/p+ l/p′= 1.

The Isometries of Hp

1964 ◽  
Vol 16 ◽  
pp. 721-728 ◽  
Author(s):  
Frank Forelli
Keyword(s):  
Unit Circle ◽  
Lebesgue Measure ◽  
Measurable Functions ◽  
Image Position ◽  
Complex Valued

Let a be the Lebesgue measure on the unit circle |z| = 1 withand let Lp be the space of complex-valued σ-measurable functions f such thatis finite. Hp is the closure in Lp of the algebra of analytic polynomials

scholarly journals On approximating Lebesgue integrals by Riemann sums

1991 ◽  
Vol 33 (2) ◽  
pp. 129-134
Author(s):  
Szilárd GY. Révész ◽  
Imre Z. Ruzsa
Keyword(s):  
Characteristic Function ◽  
Lebesgue Measure ◽  
Real Function ◽  
Riemann Sums ◽  
Function Classes ◽  
Open Set ◽  
Measurable Set ◽  
Image Position ◽  
Good Sequences

If f is a real function, periodic with period 1, we defineIn the whole paper we write ∫ for , mE for the Lebesgue measure of E ∩ [0,1], where E ⊂ ℝ is any measurable set of period 1, and we also use XE for the characteristic function of the set E. Consistent with this, the meaning of ℒp is ℒp [0, 1]. For all real xwe haveif f is Riemann-integrable on [0, 1]. However,∫ f exists for all f ∈ ℒ1 and one would wish to extend the validity of (2). As easy examples show, (cf. [3], [7]), (2) does not hold for f ∈ ℒp in general if p < 2. Moreover, Rudin [4] showed that (2) may fail for all x even for the characteristic function of an open set, and so, to get a reasonable extension, it is natural to weaken (2) towhere S ⊂ ℕ is some “good” increasing subsequence of ℕ. Naturally, for different function classes ℱ ⊂ ℒ1 we get different meanings of being good. That is, we introduce the class of ℱ-good sequences as

Almost Convergence and Well-Distributed Sequences

1968 ◽  
Vol 20 ◽  
pp. 1211-1214 ◽  
Author(s):  
Alan Zame
Keyword(s):  
Characteristic Function ◽  
Almost Convergence ◽  
Real Numbers ◽  
Image Position

A sequence (xn) of real numbers is said to be well-distributed modulo 1 (abbreviated w.d.) if for each subinterval I = [a, b] of [0, 1] we have thatwhere χI is the characteristic function of I modulo 1. A sequence (rn) of positive numbers is lacunary if

scholarly journals On the metric theory of the optimal continued fraction expansion

1997 ◽  
Vol 56 (1) ◽  
pp. 69-79
Author(s):  
R. Nair
Keyword(s):  
Lebesgue Measure ◽  
Continued Fraction ◽  
Natural Numbers ◽  
Real Numbers ◽  
Continued Fraction Expansion ◽  
Image Position ◽  
Special Case

Suppose kn denotes either φ(n) or φ(rn) (n = 1, 2, …) where the polynomial φ maps the natural numbers to themselves and rk denotes the kth rational prime. Let denote the sequence of convergents to a real numbers x for the optimal continued fraction expansion. Define the sequence of approximation constants byIn this paper we study the behaviour of the sequence for all most all x with respect to Lebesgue measure. In the special case where kn = n (n = 1, 2, …) these results are due to Bosma and Kraaikamp.

A NOTE ON INHOMOGENEOUS DIOPHANTINE APPROXIMATION IN BETA-DYNAMICAL SYSTEM

2014 ◽  
Vol 91 (1) ◽  
pp. 34-40 ◽  
Author(s):  
YUEHUA GE ◽  
FAN LÜ
Keyword(s):  
Dynamical System ◽  
Hausdorff Dimension ◽  
Real Number ◽  
Lebesgue Measure ◽  
Diophantine Approximation ◽  
Positive Function ◽  
Real Numbers ◽  
Image Position

AbstractWe study the distribution of the orbits of real numbers under the beta-transformation$T_{{\it\beta}}$for any${\it\beta}>1$. More precisely, for any real number${\it\beta}>1$and a positive function${\it\varphi}:\mathbb{N}\rightarrow \mathbb{R}^{+}$, we determine the Lebesgue measure and the Hausdorff dimension of the following set:$$\begin{eqnarray}E(T_{{\it\beta}},{\it\varphi})=\{(x,y)\in [0,1]\times [0,1]:|T_{{\it\beta}}^{n}x-y|<{\it\varphi}(n)\text{ for infinitely many }n\in \mathbb{N}\}.\end{eqnarray}$$

scholarly journals Decision problems for linear recurrences involving arbitrary real numbers

2021 ◽  
Vol Volume 17, Issue 3 ◽  
Author(s):  
Eike Neumann
Keyword(s):  
Euclidean Space ◽  
Real Number ◽  
Lebesgue Measure ◽  
Decision Problems ◽  
Real Numbers ◽  
Linear Recurrences ◽  
Initial Values ◽  
Problem Instances ◽  
Low Order

We study the decidability of the Skolem Problem, the Positivity Problem, and the Ultimate Positivity Problem for linear recurrences with real number initial values and real number coefficients in the bit-model of real computation. We show that for each problem there exists a correct partial algorithm which halts for all problem instances for which the answer is locally constant, thus establishing that all three problems are as close to decidable as one can expect them to be in this setting. We further show that the algorithms for the Positivity Problem and the Ultimate Positivity Problem halt on almost every instance with respect to the usual Lebesgue measure on Euclidean space. In comparison, the analogous problems for exact rational or real algebraic coefficients are known to be decidable only for linear recurrences of fairly low order.

scholarly journals A metrical result on the discrepancy of (nα)

1998 ◽  
Vol 40 (3) ◽  
pp. 393-425 ◽  
Author(s):  
J. Schoissengeier
Keyword(s):  
Characteristic Function ◽  
Real Number ◽  
Lebesgue Measure ◽  
Fractional Part ◽  
Irrational Numbers ◽  
Metrical Result ◽  
Image Position

In the following let Ω be the set of irrational numbers in the interval [0,1] and let λ be Lebesgue measure restricted to Ω. For any real number x, let {x} = x - [x] be the fractional part of x. Let N be anatural number and let α e Ω. Thenis known as the discrepancy of the sequence (nα)n>1 modulo 1; here c[x, y) denotes the characteristic function of the interval [x, y).

A note on approximation by automorphic images of functions in L1 and L∞

1968 ◽  
Vol 8 (2) ◽  
pp. 222-230 ◽  
Author(s):  
S. R. Harasymiv
Keyword(s):  
Present Note ◽  
Closed Subspace ◽  
Continuous Functions ◽  
Real Numbers ◽  
Measurable Functions ◽  
Integrable Functions ◽  
Image Position ◽  
Bounded Continuous Functions

In [1], it was shown that if ƒ ∈ Lp(Rn), where 1 < p < ∞, then the closed subspace of Lp (Rn) spanned by functions of the form [where a1, …, an, b1, …, bn, are real numbers; ak, ≠ 0; k = 1, …, n] coincides with the whole of Lp(Rn). In the present note, analogous results are derived for the spaces of integrable functions, essentially bounded measurable functions, bounded continuous functions, and continuous functions vanishing at infinity.

Lattice Octahedra

1960 ◽  
Vol 12 ◽  
pp. 297-302 ◽  
Author(s):  
L. J. Mordell
Keyword(s):  
Euclidean Space ◽  
Dimensional Euclidean Space ◽  
Real Numbers ◽  
Linearly Independent ◽  
Image Position

Let Ai, A2, … , An be n linearly independent points in n-dimensional Euclidean space of a lattice Λ. The points ± A1, ±A2, . . , ±An define a closed n-dimensional octahedron (or “cross poly tope“) K with centre at the origin O. Our problem is to find a basis for the lattices Λ which have no points in K except ±A1, ±A2, … , ±An.Let the position of a point P in space be defined vectorially by1where the p are real numbers. We have the following results.When n = 2, it is well known that a basis is2When n = 3, Minkowski (1) proved that there are two types of lattices, with respective bases3When n = 4, there are six essentially different bases typified by A1, A2, A3 and one of4In all expressions of this kind, the signs are independent of each other and of any other signs. This result is a restatement of a result by Brunngraber (2) and a proof is given by Wolff (3).

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