Schnirelmann density

Schnirelmann density (Redirected from Mann's theorem) Jump to navigation Jump to search In additive number theory, the Schnirelmann density of a sequence of numbers is a way to measure how "dense" the sequence is. It is named after Russian mathematician Lev Schnirelmann, who was the first to study it.[1][2] Conteúdo 1 Definição 2 Propriedades 2.1 Sensitivity 3 Schnirelmann's theorems 4 Additive bases 5 Mann's theorem 6 Waring's problem 7 Schnirelmann's constant 8 Essential components 9 References Definition The Schnirelmann density of a set of natural numbers A is defined as {displaystyle sigma A=inf _{n}{fratura {UMA(n)}{n}},} onde um(n) denotes the number of elements of A not exceeding n and inf is infimum.[3] The Schnirelmann density is well-defined even if the limit of A(n)/n as n → ∞ fails to exist (see upper and lower asymptotic density).

Properties By definition, 0 ≤ A(n) ≤ n and n σA ≤ A(n) for all n, e, portanto, 0 ≤ σA ≤ 1, and σA = 1 if and only if A = N. Além disso, {displaystyle sigma A=0Rightarrow forall epsilon >0 exists n A(n)0} then there exists {estilo de exibição k} de tal modo que {estilo de exibição bigoplus _{i=1}^{k}A=mathbb {N} .} Additive bases A subset {displaystyle Asubseteq mathbb {N} } with the property that {displaystyle Aoplus Aoplus cdots oplus A=mathbb {N} } for a finite sum, is called an additive basis, and the least number of summands required is called the degree (sometimes order) of the basis. Desta forma, the last theorem states that any set with positive Schnirelmann density is an additive basis. Nesta terminologia, the set of squares {estilo de exibição {mathfrak {G}}^{2}={k^{2}}_{k=1}^{infty }} is an additive basis of degree 4. (About an open problem for additive bases, see Erdős–Turán conjecture on additive bases.) Mann's theorem Historically the theorems above were pointers to the following result, at one time known as the {displaystyle alpha +beta } hypothesis. It was used by Edmund Landau and was finally proved by Henry Mann in 1942.

Teorema. (Mann 1942) Deixar {estilo de exibição A} e {estilo de exibição B} be subsets of {estilo de exibição mathbb {N} } . In case that {displaystyle Aoplus Bneq mathbb {N} } , nós ainda temos {estilo de exibição sigma (Aoplus B)geq sigma A+sigma B.} An analogue of this theorem for lower asymptotic density was obtained by Kneser.[4] At a later date, E. Artin and P. Scherk simplified the proof of Mann's theorem.[5] Waring's problem Main article: Waring's problem Let {estilo de exibição k} e {estilo de exibição N} be natural numbers. Deixar {estilo de exibição {mathfrak {G}}^{k}={i^{k}}_{i=1}^{infty }} . Definir {estilo de exibição r_{N}^{k}(n)} to be the number of non-negative integral solutions to the equation {estilo de exibição x_{1}^{k}+x_{2}^{k}+cdots +x_{N}^{k}=n} e {estilo de exibição R_{N}^{k}(n)} to be the number of non-negative integral solutions to the inequality {displaystyle 0leq x_{1}^{k}+x_{2}^{k}+cdots +x_{N}^{k}leq n,} in the variables {estilo de exibição x_{eu}} , respectivamente. Desta forma {estilo de exibição R_{N}^{k}(n)=soma _{i=0}^{n}r_{N}^{k}(eu)} . Nós temos {estilo de exibição r_{N}^{k}(n)>0leftrightarrow nin N{mathfrak {G}}^{k},} {estilo de exibição R_{N}^{k}(n)gek deixou({fratura {n}{N}}certo)^{fratura {N}{k}}.} The volume of the {estilo de exibição N} -dimensional body defined by {displaystyle 0leq x_{1}^{k}+x_{2}^{k}+cdots +x_{N}^{k}leq n} , is bounded by the volume of the hypercube of size {estilo de exibição n^{1/k}} , por isso {estilo de exibição R_{N}^{k}(n)=soma _{i=0}^{n}r_{N}^{k}(eu)leq n^{N/k}} . The hard part is to show that this bound still works on the average, ou seja, Lema. (Linnik) Para todos {displaystyle kin mathbb {N} } existe {estilo de exibição Nin mathbb {N} } and a constant {displaystyle c=c(k)} , depending only on {estilo de exibição k} , tal que para todos {estilo de exibição nin mathbb {N} } , {estilo de exibição r_{N}^{k}(m)0} .

We have thus established the general solution to Waring's Problem: Corolário. (Hilbert 1909) Para todos {estilo de exibição k} existe {estilo de exibição N} , depending only on {estilo de exibição k} , such that every positive integer {estilo de exibição m} can be expressed as the sum of at most {estilo de exibição N} many {estilo de exibição k} -th powers.

Schnirelmann's constant In 1930 Schnirelmann used these ideas in conjunction with the Brun sieve to prove Schnirelmann's theorem,[1][2] that any natural number greater than 1 can be written as the sum of not more than C prime numbers, where C is an effectively computable constant:[6] Schnirelmann obtained C < 800000.[7] Schnirelmann's constant is the lowest number C with this property.[6] Olivier Ramaré showed in (Ramaré 1995) that Schnirelmann's constant is at most 7,[6] improving the earlier upper bound of 19 obtained by Hans Riesel and R. C. Vaughan. Schnirelmann's constant is at least 3; Goldbach's conjecture implies that this is the constant's actual value.[6] In 2013, Harald Helfgott proved Goldbach's weak conjecture for all odd numbers. Therefore Schnirelmann's constant is at most 4. [8][9][10][11] Essential components Khintchin proved that the sequence of squares, though of zero Schnirelmann density, when added to a sequence of Schnirelmann density between 0 and 1, increases the density: {displaystyle sigma (A+{mathfrak {G}}^{2})>sigma (UMA){texto{ por }}0 1, and for every c > 1 there is an essential component which has at most (log x)c elements up to x.[15] Referências ^ Ir para: a b Schnirelmann, L.G. (1930). "On the additive properties of numbers", first published in "Proceedings of the Don Polytechnic Institute in Novocherkassk" (em russo), vol XIV (1930), pp. 3-27, and reprinted in "Uspekhi Matematicheskikh Nauk" (em russo), 1939, não. 6, 9-25. ^ Saltar para: a b Schnirelmann, L.G. (1933). First published as "Über additive Eigenschaften von Zahlen" dentro "Anais Matemáticos" (em alemão), volume 107 (1933), 649-690, and reprinted as "On the additive properties of numbers" dentro "Uspekhin. Matematicheskikh Nauk" (em russo), 1940, não. 7, 7-46. ^ Nathanson (1996) pp.191–192 ^ Nathanson (1990) p.397 ^ E. Artin and P. Scherk (1943) On the sums of two sets of integers, Ana. de matemática 44, page=138-142. ^ Saltar para: a b c d Nathanson (1996) p.208 ^ Gelfond & Linnik (1966) p.136 ^ Helfgott, Harald A. (2013). "Major arcs for Goldbach's theorem". arXiv:1305.2897 [math.NT]. ^ Helfgott, Harald A. (2012). "Minor arcs for Goldbach's problem". arXiv:1205.5252 [math.NT]. ^ Helfgott, Harald A. (2013). "The ternary Goldbach conjecture is true". arXiv:1312.7748 [math.NT]. ^ Helfgoot, Harald A. (2015). "The ternary Goldbach problem". arXiv:1501.05438 [math.NT]. ^ Ruzsa (2009) p.177 ^ Ruzsa (2009) p.179 ^ Linnik, Yu. V. (1942). "On Erdõs's theorem on the addition of numerical sequences". Esteira. Sb. 10: 67-78. Zbl 0063.03574. ^ Ruzsa (2009) p.184 Hilbert, Davi (1909). "Beweis für die Darstellbarkeit der ganzen Zahlen durch eine feste Anzahl nter Potenzen (Waringsches Problem)". Anais Matemáticos. 67 (3): 281–300. doi:10.1007/BF01450405. ISSN 0025-5831. MR 1511530. S2CID 179177986. Schnirelmann, L.G. (1930). "On additive properties of numbers". Ana. Inst. Polytechn. Novočerkassk (em russo). 14: 3-28. JFM 56.0892.02. Schnirelmann, L.G. (1933). "Über additive Eigenschaften von Zahlen". Matemática. Ana. (em alemão). 107: 649–690. doi:10.1007/BF01448914. S2CID 123067485. Zbl 0006.10402. Mann, Henry B. (1942). "A proof of the fundamental theorem on the density of sums of sets of positive integers". Anais da Matemática. Segunda Série. 43 (3): 523–527. doi:10.2307/1968807. ISSN 0003-486X. JSTOR 1968807. MR 0006748. Zbl 0061.07406. Gelfond, A.O.; Linnik, Yu. V. (1966). L.J. Mordell (ed.). Elementary Methods in Analytic Number Theory. George Allen & Unwin. Mann, Henry B. (1976). Addition Theorems: The Addition Theorems of Group Theory and Number Theory (Corrected reprint of 1965 Wiley ed.). Huntington, Nova york: Robert E. Krieger Publishing Company. ISBN 978-0-88275-418-5. MR 0424744. {{cite book}}: External link in |publisher= (help) Nathanson, Melvyn B. (1990). "Best possible results on the density of sumsets". In Berndt, Bruce C.; Diamond, Harold G.; Halberstam, Oi; et al. (ed.). Teoria analítica dos números. Proceedings of a conference in honor of Paul T. Bateman, held on April 25-27, 1989, at the University of Illinois, Urbana, IL (EUA). Progress in Mathematics. Volume. 85. Boston: Birkhauser. pp. 395–403. ISBN 978-0-8176-3481-0. Zbl 0722.11007. Ramaré, O. (1995). "On Šnirel'man's constant". Annali della Scuola Normale Superiore di Pisa. Classe di Scienze. Serie IV. 22 (4): 645–706. Zbl 0851.11057. Recuperado 2011-03-28. Nathanson, Melvyn B. (1996). Teoria Aditiva dos Números: the Classical Bases. Textos de Graduação em Matemática. Volume. 164. Springer-Verlag. ISBN 978-0-387-94656-6. Zbl 0859.11002. Nathanson, Melvyn B. (2000). Elementary Methods in Number Theory. Textos de Graduação em Matemática. Volume. 195. Springer-Verlag. pp. 359–367. ISBN 978-0-387-98912-9. Zbl 0953.11002. Khinchin, UMA. Ya. (1998). Three Pearls of Number Theory. Mineola, Nova Iorque: Dover. ISBN 978-0-486-40026-6. Has a proof of Mann's theorem and the Schnirelmann-density proof of Waring's conjecture. Artin, Emil; Scherk, P. (1943). "On the sums of two set of integers". Ana. de matemática. 44: 138-142. Cojocaru, Alina Carmen; Murty, M. RAM (2005). An introduction to sieve methods and their applications. Textos de estudantes da London Mathematical Society. Volume. 66. Cambridge University Press. pp. 100-105. ISBN 978-0-521-61275-3. Ruzsa, Imre Z. (2009). "Sumsets and structure". In Geroldinger, Alfred; Ruzsa, Imre Z. (ed.). Combinatorial number theory and additive group theory. Advanced Courses in Mathematics CRM Barcelona. Elsholtz, C.; Freiman, G.; Hamidoune, S. O.; Hegyvári, N.; Károlyi, G.; Nathanson, M.; Solymosi, J.; Stanchescu, S. With a foreword by Javier Cilleruelo, Marc Noy and Oriol Serra (Coordinators of the DocCourse). Basileia: Birkhauser. pp. 87–210. ISBN 978-3-7643-8961-1. Zbl 1221.11026. Categorias: Additive number theoryMathematical constants