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Hardy–Littlewood maximal function

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1940: 1649: 559: 1638: 735: 2501: 969: 3083: 1288: 2927: 1452: 261: 2195: 2073:
Here we use a standard trick involving the maximal function to give a quick proof of Lebesgue differentiation theorem. (But remember that in the proof of the maximal theorem, we used the Vitali covering lemma.) Let
2323: 1935:{\displaystyle \|Mf\|_{p}^{p}\leq p\int _{0}^{\infty }t^{p-1}\left({2C \over t}\int _{|f|>{\frac {t}{2}}}|f|dx\right)dt=2Cp\int _{0}^{\infty }\int _{|f|>{\frac {t}{2}}}t^{p-2}|f|dxdt=C_{p}\|f\|_{p}^{p}} 2785:
There are several common variants of the Hardy-Littlewood maximal operator which replace the averages over centered balls with averages over different families of sets. For instance, one can define the
2407: 1096: 455: 2599: 2663: 892: 1467: 616: 2707: 2543: 863: 839: 2426: 1994: 2021: 2949: 900: 1160: 2796: 1339: 124: 2092: 2206: 2036: 2051: 2362: 2666: 3266: 1019: 2067: 554:{\displaystyle \left|\{Mf>\lambda \}\right|<{\frac {C_{d}}{\lambda }}\Vert f\Vert _{L^{1}(\mathbf {R} ^{d})}.} 3261: 3135: 2552: 2056: 1633:{\displaystyle \|Mf\|_{p}^{p}=\int \int _{0}^{Mf(x)}pt^{p-1}dtdx=p\int _{0}^{\infty }t^{p-1}|\{Mf>t\}|dt} 730:{\displaystyle \Vert Mf\Vert _{L^{p}(\mathbf {R} ^{d})}\leq C_{p,d}\Vert f\Vert _{L^{p}(\mathbf {R} ^{d})}.} 39: 3256: 2616: 2032: 2024: 803: 570: 868: 2672: 2509: 2047:
Some applications of the Hardy–Littlewood Maximal Inequality include proving the following results:
844: 820: 2496:{\displaystyle \left|\{\Omega g>\varepsilon \}\right|\leq {\frac {2\,M}{\varepsilon }}\|g\|_{1}} 309: 289: 795: 794: = ∞, the inequality is trivial (since the average of a function is no larger than its 345: 59: 17: 2061: 3240: 47: 1966: 3173: 3112: 2028: 341: 333: 271: 3078:{\displaystyle M_{\Delta }f(x)=\sup _{x\in Q_{x}}{\frac {1}{|Q_{x}|}}\int _{Q_{x}}|f(y)|dy} 1999: 3190: 964:{\displaystyle \bigcup _{B\in {\mathcal {F}}}B\subset \bigcup _{B\in {\mathcal {F'}}}5B} 3208: 749: 1283:{\displaystyle |\{Mf>t\}|\leq 5^{d}\sum _{j}|B_{j}|\leq {5^{d} \over t}\int |f|dy.} 3250: 3236: 43: 3178: 3161: 2922:{\displaystyle f^{*}(x)=\sup _{x\in B_{x}}{\frac {1}{|B_{x}|}}\int _{B_{x}}|f(y)|dy} 3096: 2939:
are required to merely contain x, rather than be centered at x. There is also the
2782:. It is unknown whether there is a weak bound that is independent of dimension. 2746:
about spherical maximal functions can be used to show that, for 1 < 
1447:{\displaystyle |\{Mf>t\}|\leq {2C \over t}\int _{|f|>{\frac {t}{2}}}|f|dx,} 1293:
This completes the proof of the weak-type estimate. We next deduce from this the
790:
While there are several proofs of this theorem, a common one is given below: For
256:{\displaystyle Mf(x)=\sup _{r>0}{\frac {1}{|B(x,r)|}}\int _{B(x,r)}|f(y)|\,dy} 2743: 329: 28: 2190:{\displaystyle \Omega f(x)=\limsup _{r\to 0}f_{r}(x)-\liminf _{r\to 0}f_{r}(x)} 806:
to prove the weak-type estimate. (See the article for the proof of the lemma.)
1132:. By the lemma, we can find, among such balls, a sequence of disjoint balls 349: 91: 3202:
The best constant for the centered Hardy–Littlewood maximal inequality
752:
used the Calderón-Zygmund method of rotations to prove the following:
565:
With the Hardy–Littlewood maximal inequality in hand, the following
2318:{\displaystyle f_{r}(x)={\frac {1}{|B(x,r)|}}\int _{B(x,r)}f(y)dy.} 802: < ∞, first we shall use the following version of the 395:). Before stating the theorem more precisely, for simplicity, let { 3231:
Singular Integrals and Differentiability Properties of Functions
3162:"The development of square functions in the work of A. Zygmund" 3103:. Both of these operators satisfy the HL maximal inequality. 2790:
HL maximal operator (using the notation of Stein-Shakarchi)
944: 917: 875: 850: 826: 437: > 0 such that for all λ > 0 and 1329:/2 and 0 otherwise. By the weak-type estimate applied to 90:
returns the maximum of a set of reals, namely the set of
316:
is finite almost everywhere. This is a corollary of the
2402:{\displaystyle \Omega f\leq \Omega g+\Omega h=\Omega g} 2952: 2799: 2675: 2619: 2555: 2512: 2429: 2365: 2209: 2095: 2002: 1969: 1652: 1470: 1342: 1163: 1022: 903: 871: 847: 823: 619: 458: 127: 2742:
are in the above inequalities. However, a result of
2750: < ∞, we can remove the dependence of 2356:) with norm that can be made arbitrary small. Then 841:a family of open balls with bounded diameter. Then 3077: 2921: 2701: 2657: 2593: 2537: 2495: 2401: 2317: 2189: 2015: 1988: 1934: 1632: 1446: 1282: 1090: 963: 886: 857: 833: 729: 553: 255: 3213:Princeton Lectures in Analysis III: Real Analysis 2979: 2823: 2728:It is still unknown what the smallest constants 2557: 2153: 2115: 741:In the strong type estimate the best bounds for 147: 2709:almost everywhere. By the uniqueness of limit, 2605:. It remains to show the limit actually equals 1091:{\displaystyle \int _{B_{x}}|f|dy>t|B_{x}|.} 2039:below for more about optimizing the constant. 3166:Bulletin of the American Mathematical Society 1109:} is a subset of the union of such balls, as 8: 3204:, Annals of Mathematics, 157 (2003), 647–688 2640: 2620: 2520: 2513: 2484: 2477: 2450: 2435: 1918: 1911: 1663: 1653: 1616: 1601: 1481: 1471: 1363: 1348: 1184: 1169: 690: 683: 630: 620: 569:estimate is an immediate consequence of the 514: 507: 479: 464: 1960:. This completes the proof of the theorem. 2344:is continuous and has compact support and 3177: 3064: 3047: 3039: 3034: 3022: 3016: 3007: 3001: 2993: 2982: 2957: 2951: 2908: 2891: 2883: 2878: 2866: 2860: 2851: 2845: 2837: 2826: 2804: 2798: 2685: 2680: 2674: 2643: 2627: 2618: 2576: 2560: 2554: 2523: 2511: 2487: 2467: 2461: 2428: 2364: 2273: 2261: 2238: 2232: 2214: 2208: 2172: 2156: 2134: 2118: 2094: 2007: 2001: 1980: 1968: 1926: 1921: 1905: 1881: 1873: 1861: 1845: 1837: 1829: 1828: 1818: 1813: 1775: 1767: 1755: 1747: 1739: 1738: 1719: 1702: 1692: 1687: 1671: 1666: 1651: 1619: 1596: 1584: 1574: 1569: 1535: 1510: 1505: 1489: 1484: 1469: 1430: 1422: 1410: 1402: 1394: 1393: 1374: 1366: 1343: 1341: 1266: 1258: 1244: 1238: 1230: 1224: 1215: 1209: 1199: 1187: 1164: 1162: 1080: 1074: 1065: 1048: 1040: 1032: 1027: 1021: 942: 941: 934: 916: 915: 908: 902: 874: 873: 870: 849: 848: 846: 825: 824: 822: 713: 708: 698: 693: 671: 653: 648: 638: 633: 618: 537: 532: 522: 517: 496: 490: 457: 246: 241: 224: 203: 191: 168: 162: 150: 126: 3123: 894:consisting of disjoint balls such that 3241:Topics in Real and Functional Analysis 2613:). But this is easy: it is known that 2594:{\displaystyle \lim _{r\to 0}f_{r}(x)} 3129: 3127: 7: 2778: > 0 only depending on 2658:{\displaystyle \|f_{r}-f\|_{1}\to 0} 1002:, by definition, we can find a ball 430: ≥ 1, there is a constant 3136:"Stein's spherical maximal theorem" 571:Marcinkiewicz interpolation theorem 324:Hardy–Littlewood maximal inequality 318:Hardy–Littlewood maximal inequality 3233:. Princeton University Press, 1971 3220:Maximal functions: spherical means 3215:. Princeton University Press, 2005 2958: 2669:) and thus there is a subsequence 2438: 2393: 2384: 2375: 2366: 2096: 2057:Rademacher differentiation theorem 1819: 1693: 1575: 748:are unknown. However subsequently 25: 2420:and so, by the theorem, we have: 757:Theorem (Dimension Independence). 584: ≥ 1, 1 <  33:Hardy–Littlewood maximal operator 18:Hardy-Littlewood maximal function 3222:, Proc. Natl. Acad. Sci. U.S.A. 2549:= 0 almost everywhere; that is, 2052:Lebesgue differentiation theorem 2031:, and the finite version of the 1996:in the proof can be improved to 817:be a separable metric space and 709: 649: 533: 3179:10.1090/s0273-0979-1982-15040-6 1643:By the estimate above we have: 887:{\displaystyle {\mathcal {F}}'} 578:Theorem (Strong Type Estimate). 3065: 3061: 3055: 3048: 3023: 3008: 2972: 2966: 2909: 2905: 2899: 2892: 2867: 2852: 2816: 2810: 2702:{\displaystyle f_{r_{k}}\to f} 2693: 2649: 2588: 2582: 2564: 2538:{\displaystyle \|g\|_{1}\to 0} 2529: 2303: 2297: 2289: 2277: 2262: 2258: 2246: 2239: 2226: 2220: 2184: 2178: 2160: 2146: 2140: 2122: 2108: 2102: 2068:Fractional integration theorem 1882: 1874: 1838: 1830: 1776: 1768: 1748: 1740: 1620: 1597: 1523: 1517: 1431: 1423: 1403: 1395: 1367: 1344: 1267: 1259: 1231: 1216: 1188: 1165: 1081: 1066: 1049: 1041: 858:{\displaystyle {\mathcal {F}}} 834:{\displaystyle {\mathcal {F}}} 719: 704: 659: 644: 543: 528: 242: 238: 232: 225: 219: 207: 192: 188: 176: 169: 140: 134: 1: 2667:approximation of the identity 2064:on nontangential convergence. 424:Theorem (Weak Type Estimate). 275:-dimensional Lebesgue measure 74:and returns another function 763: ≤ ∞ one can pick 610: > 0 such that 375:) then the maximal function 38:is a significant non-linear 2757:on the dimension, that is, 3283: 3195:Bounded Analytic Functions 865:has a countable subfamily 304:, being the supremum over 300:, so the maximal function 1121:}. This is trivial since 312:. It is not obvious that 288:The averages are jointly 2720:almost everywhere then. 1139:such that the union of 5 798:). For 1 <  3197:. Springer-Verlag, 2006 1989:{\displaystyle C=5^{d}} 1963:Note that the constant 3079: 2923: 2703: 2659: 2601:exists for almost all 2595: 2539: 2497: 2403: 2319: 2191: 2017: 1990: 1936: 1634: 1448: 1284: 1092: 984: 965: 888: 859: 835: 783: 739: 731: 563: 555: 308: > 0, is 257: 3207:Rami Shakarchi & 3160:Stein, E. M. (1982). 3099:containing the point 3080: 2924: 2704: 2660: 2596: 2540: 2498: 2412:by continuity. Now, Ω 2404: 2320: 2192: 2033:Vitali covering lemma 2018: 2016:{\displaystyle 3^{d}} 1991: 1937: 1635: 1449: 1285: 1093: 966: 889: 860: 836: 808: 804:Vitali covering lemma 759:For 1 <  754: 732: 575: 556: 421: 258: 58:The operator takes a 2950: 2943:HL maximal operator 2797: 2673: 2617: 2553: 2510: 2427: 2363: 2207: 2093: 2000: 1967: 1650: 1468: 1340: 1161: 1020: 982:with 5 times radius. 901: 869: 845: 821: 617: 603:there is a constant 588: ≤ ∞, and 456: 363:> 1. That is, if 125: 3200:Antonios D. Melas, 1945:where the constant 1931: 1823: 1697: 1676: 1579: 1527: 1494: 3267:Types of functions 3075: 3000: 2919: 2844: 2771:for some constant 2699: 2655: 2591: 2571: 2535: 2493: 2399: 2315: 2187: 2167: 2129: 2037:Discussion section 2013: 1986: 1932: 1917: 1809: 1683: 1662: 1630: 1565: 1501: 1480: 1444: 1280: 1214: 1088: 961: 954: 923: 884: 855: 831: 796:essential supremum 727: 551: 403:} denote the set { 346:sublinear operator 253: 161: 98:for all the balls 60:locally integrable 3262:Harmonic analysis 3226:(1976), 2174–2175 3028: 2978: 2872: 2822: 2556: 2475: 2267: 2152: 2114: 1853: 1763: 1732: 1418: 1387: 1253: 1205: 930: 904: 505: 197: 146: 78:. For any point 48:harmonic analysis 16:(Redirected from 3274: 3229:Elias M. Stein, 3218:Elias M. Stein, 3184: 3183: 3181: 3157: 3151: 3150: 3148: 3146: 3131: 3113:Rising sun lemma 3095:ranges over all 3084: 3082: 3081: 3076: 3068: 3051: 3046: 3045: 3044: 3043: 3029: 3027: 3026: 3021: 3020: 3011: 3002: 2999: 2998: 2997: 2962: 2961: 2932:where the balls 2928: 2926: 2925: 2920: 2912: 2895: 2890: 2889: 2888: 2887: 2873: 2871: 2870: 2865: 2864: 2855: 2846: 2843: 2842: 2841: 2809: 2808: 2708: 2706: 2705: 2700: 2692: 2691: 2690: 2689: 2664: 2662: 2661: 2656: 2648: 2647: 2632: 2631: 2600: 2598: 2597: 2592: 2581: 2580: 2570: 2544: 2542: 2541: 2536: 2528: 2527: 2506:Now, we can let 2502: 2500: 2499: 2494: 2492: 2491: 2476: 2471: 2462: 2457: 2453: 2408: 2406: 2405: 2400: 2324: 2322: 2321: 2316: 2293: 2292: 2268: 2266: 2265: 2242: 2233: 2219: 2218: 2196: 2194: 2193: 2188: 2177: 2176: 2166: 2139: 2138: 2128: 2029:Lebesgue measure 2025:inner regularity 2022: 2020: 2019: 2014: 2012: 2011: 1995: 1993: 1992: 1987: 1985: 1984: 1952:depends only on 1941: 1939: 1938: 1933: 1930: 1925: 1910: 1909: 1885: 1877: 1872: 1871: 1856: 1855: 1854: 1846: 1841: 1833: 1822: 1817: 1790: 1786: 1779: 1771: 1766: 1765: 1764: 1756: 1751: 1743: 1733: 1728: 1720: 1713: 1712: 1696: 1691: 1675: 1670: 1639: 1637: 1636: 1631: 1623: 1600: 1595: 1594: 1578: 1573: 1546: 1545: 1526: 1509: 1493: 1488: 1453: 1451: 1450: 1445: 1434: 1426: 1421: 1420: 1419: 1411: 1406: 1398: 1388: 1383: 1375: 1370: 1347: 1289: 1287: 1286: 1281: 1270: 1262: 1254: 1249: 1248: 1239: 1234: 1229: 1228: 1219: 1213: 1204: 1203: 1191: 1168: 1125:is contained in 1097: 1095: 1094: 1089: 1084: 1079: 1078: 1069: 1052: 1044: 1039: 1038: 1037: 1036: 970: 968: 967: 962: 953: 952: 951: 950: 922: 921: 920: 893: 891: 890: 885: 883: 879: 878: 864: 862: 861: 856: 854: 853: 840: 838: 837: 832: 830: 829: 736: 734: 733: 728: 723: 722: 718: 717: 712: 703: 702: 682: 681: 663: 662: 658: 657: 652: 643: 642: 560: 558: 557: 552: 547: 546: 542: 541: 536: 527: 526: 506: 501: 500: 491: 486: 482: 419:}. Now we have: 334:J. E. Littlewood 328:This theorem of 262: 260: 259: 254: 245: 228: 223: 222: 198: 196: 195: 172: 163: 160: 110:) of any radius 21: 3282: 3281: 3277: 3276: 3275: 3273: 3272: 3271: 3247: 3246: 3243:(lecture notes) 3191:John B. Garnett 3187: 3159: 3158: 3154: 3144: 3142: 3133: 3132: 3125: 3121: 3109: 3093: 3035: 3030: 3012: 3006: 2989: 2953: 2948: 2947: 2937: 2879: 2874: 2856: 2850: 2833: 2800: 2795: 2794: 2776: 2769: 2762: 2755: 2740: 2733: 2726: 2714: 2681: 2676: 2671: 2670: 2639: 2623: 2615: 2614: 2572: 2551: 2550: 2519: 2508: 2507: 2483: 2463: 2434: 2430: 2425: 2424: 2361: 2360: 2269: 2237: 2210: 2205: 2204: 2168: 2130: 2091: 2090: 2062:Fatou's theorem 2045: 2003: 1998: 1997: 1976: 1965: 1964: 1950: 1901: 1857: 1824: 1734: 1721: 1718: 1714: 1698: 1648: 1647: 1580: 1531: 1466: 1465: 1389: 1376: 1338: 1337: 1297:bounds. Define 1240: 1220: 1195: 1159: 1158: 1154:}. It follows: 1144: 1137: 1130: 1070: 1028: 1023: 1018: 1017: 1007: 943: 899: 898: 872: 867: 866: 843: 842: 819: 818: 788: 777:independent of 775: 768: 746: 707: 694: 689: 667: 647: 634: 629: 615: 614: 608: 531: 518: 513: 492: 463: 459: 454: 453: 435: 326: 199: 167: 123: 122: 86:, the function 56: 23: 22: 15: 12: 11: 5: 3280: 3278: 3270: 3269: 3264: 3259: 3249: 3248: 3245: 3244: 3234: 3227: 3216: 3209:Elias M. Stein 3205: 3198: 3186: 3185: 3172:(2): 359–376. 3168:. New Series. 3152: 3134:Tao, Terence. 3122: 3120: 3117: 3116: 3115: 3108: 3105: 3091: 3086: 3085: 3074: 3071: 3067: 3063: 3060: 3057: 3054: 3050: 3042: 3038: 3033: 3025: 3019: 3015: 3010: 3005: 2996: 2992: 2988: 2985: 2981: 2977: 2974: 2971: 2968: 2965: 2960: 2956: 2935: 2930: 2929: 2918: 2915: 2911: 2907: 2904: 2901: 2898: 2894: 2886: 2882: 2877: 2869: 2863: 2859: 2854: 2849: 2840: 2836: 2832: 2829: 2825: 2821: 2818: 2815: 2812: 2807: 2803: 2774: 2767: 2760: 2753: 2738: 2731: 2725: 2722: 2712: 2698: 2695: 2688: 2684: 2679: 2654: 2651: 2646: 2642: 2638: 2635: 2630: 2626: 2622: 2590: 2587: 2584: 2579: 2575: 2569: 2566: 2563: 2559: 2545:and conclude Ω 2534: 2531: 2526: 2522: 2518: 2515: 2504: 2503: 2490: 2486: 2482: 2479: 2474: 2470: 2466: 2460: 2456: 2452: 2449: 2446: 2443: 2440: 2437: 2433: 2410: 2409: 2398: 2395: 2392: 2389: 2386: 2383: 2380: 2377: 2374: 2371: 2368: 2326: 2325: 2314: 2311: 2308: 2305: 2302: 2299: 2296: 2291: 2288: 2285: 2282: 2279: 2276: 2272: 2264: 2260: 2257: 2254: 2251: 2248: 2245: 2241: 2236: 2231: 2228: 2225: 2222: 2217: 2213: 2198: 2197: 2186: 2183: 2180: 2175: 2171: 2165: 2162: 2159: 2155: 2154:lim inf 2151: 2148: 2145: 2142: 2137: 2133: 2127: 2124: 2121: 2117: 2116:lim sup 2113: 2110: 2107: 2104: 2101: 2098: 2071: 2070: 2065: 2059: 2054: 2044: 2041: 2010: 2006: 1983: 1979: 1975: 1972: 1948: 1943: 1942: 1929: 1924: 1920: 1916: 1913: 1908: 1904: 1900: 1897: 1894: 1891: 1888: 1884: 1880: 1876: 1870: 1867: 1864: 1860: 1852: 1849: 1844: 1840: 1836: 1832: 1827: 1821: 1816: 1812: 1808: 1805: 1802: 1799: 1796: 1793: 1789: 1785: 1782: 1778: 1774: 1770: 1762: 1759: 1754: 1750: 1746: 1742: 1737: 1731: 1727: 1724: 1717: 1711: 1708: 1705: 1701: 1695: 1690: 1686: 1682: 1679: 1674: 1669: 1665: 1661: 1658: 1655: 1641: 1640: 1629: 1626: 1622: 1618: 1615: 1612: 1609: 1606: 1603: 1599: 1593: 1590: 1587: 1583: 1577: 1572: 1568: 1564: 1561: 1558: 1555: 1552: 1549: 1544: 1541: 1538: 1534: 1530: 1525: 1522: 1519: 1516: 1513: 1508: 1504: 1500: 1497: 1492: 1487: 1483: 1479: 1476: 1473: 1455: 1454: 1443: 1440: 1437: 1433: 1429: 1425: 1417: 1414: 1409: 1405: 1401: 1397: 1392: 1386: 1382: 1379: 1373: 1369: 1365: 1362: 1359: 1356: 1353: 1350: 1346: 1291: 1290: 1279: 1276: 1273: 1269: 1265: 1261: 1257: 1252: 1247: 1243: 1237: 1233: 1227: 1223: 1218: 1212: 1208: 1202: 1198: 1194: 1190: 1186: 1183: 1180: 1177: 1174: 1171: 1167: 1142: 1135: 1128: 1099: 1098: 1087: 1083: 1077: 1073: 1068: 1064: 1061: 1058: 1055: 1051: 1047: 1043: 1035: 1031: 1026: 1005: 972: 971: 960: 957: 949: 946: 940: 937: 933: 929: 926: 919: 914: 911: 907: 882: 877: 852: 828: 787: 784: 773: 766: 750:Elias M. Stein 744: 738: 737: 726: 721: 716: 711: 706: 701: 697: 692: 688: 685: 680: 677: 674: 670: 666: 661: 656: 651: 646: 641: 637: 632: 628: 625: 622: 606: 562: 561: 550: 545: 540: 535: 530: 525: 521: 516: 512: 509: 504: 499: 495: 489: 485: 481: 478: 475: 472: 469: 466: 462: 433: 359:to itself for 325: 322: 270:| denotes the 264: 263: 252: 249: 244: 240: 237: 234: 231: 227: 221: 218: 215: 212: 209: 206: 202: 194: 190: 187: 184: 181: 178: 175: 171: 166: 159: 156: 153: 149: 145: 142: 139: 136: 133: 130: 92:average values 55: 52: 24: 14: 13: 10: 9: 6: 4: 3: 2: 3279: 3268: 3265: 3263: 3260: 3258: 3257:Real analysis 3255: 3254: 3252: 3242: 3238: 3237:Gerald Teschl 3235: 3232: 3228: 3225: 3221: 3217: 3214: 3210: 3206: 3203: 3199: 3196: 3192: 3189: 3188: 3180: 3175: 3171: 3167: 3163: 3156: 3153: 3141: 3137: 3130: 3128: 3124: 3118: 3114: 3111: 3110: 3106: 3104: 3102: 3098: 3094: 3072: 3069: 3058: 3052: 3040: 3036: 3031: 3017: 3013: 3003: 2994: 2990: 2986: 2983: 2975: 2969: 2963: 2954: 2946: 2945: 2944: 2942: 2938: 2916: 2913: 2902: 2896: 2884: 2880: 2875: 2861: 2857: 2847: 2838: 2834: 2830: 2827: 2819: 2813: 2805: 2801: 2793: 2792: 2791: 2789: 2783: 2781: 2777: 2770: 2764: =  2763: 2756: 2749: 2745: 2741: 2734: 2723: 2721: 2719: 2715: 2696: 2686: 2682: 2677: 2668: 2652: 2644: 2636: 2633: 2628: 2624: 2612: 2608: 2604: 2585: 2577: 2573: 2567: 2561: 2548: 2532: 2524: 2516: 2488: 2480: 2472: 2468: 2464: 2458: 2454: 2447: 2444: 2441: 2431: 2423: 2422: 2421: 2419: 2415: 2396: 2390: 2387: 2381: 2378: 2372: 2369: 2359: 2358: 2357: 2355: 2351: 2347: 2343: 2339: 2335: 2331: 2312: 2309: 2306: 2300: 2294: 2286: 2283: 2280: 2274: 2270: 2255: 2252: 2249: 2243: 2234: 2229: 2223: 2215: 2211: 2203: 2202: 2201: 2181: 2173: 2169: 2163: 2157: 2149: 2143: 2135: 2131: 2125: 2119: 2111: 2105: 2099: 2089: 2088: 2087: 2085: 2081: 2077: 2069: 2066: 2063: 2060: 2058: 2055: 2053: 2050: 2049: 2048: 2042: 2040: 2038: 2034: 2030: 2026: 2023:by using the 2008: 2004: 1981: 1977: 1973: 1970: 1961: 1959: 1955: 1951: 1927: 1922: 1914: 1906: 1902: 1898: 1895: 1892: 1889: 1886: 1878: 1868: 1865: 1862: 1858: 1850: 1847: 1842: 1834: 1825: 1814: 1810: 1806: 1803: 1800: 1797: 1794: 1791: 1787: 1783: 1780: 1772: 1760: 1757: 1752: 1744: 1735: 1729: 1725: 1722: 1715: 1709: 1706: 1703: 1699: 1688: 1684: 1680: 1677: 1672: 1667: 1659: 1656: 1646: 1645: 1644: 1627: 1624: 1613: 1610: 1607: 1604: 1591: 1588: 1585: 1581: 1570: 1566: 1562: 1559: 1556: 1553: 1550: 1547: 1542: 1539: 1536: 1532: 1528: 1520: 1514: 1511: 1506: 1502: 1498: 1495: 1490: 1485: 1477: 1474: 1464: 1463: 1462: 1460: 1441: 1438: 1435: 1427: 1415: 1412: 1407: 1399: 1390: 1384: 1380: 1377: 1371: 1360: 1357: 1354: 1351: 1336: 1335: 1334: 1332: 1328: 1324: 1320: 1316: 1312: 1308: 1304: 1300: 1296: 1277: 1274: 1271: 1263: 1255: 1250: 1245: 1241: 1235: 1225: 1221: 1210: 1206: 1200: 1196: 1192: 1181: 1178: 1175: 1172: 1157: 1156: 1155: 1153: 1149: 1145: 1138: 1131: 1124: 1120: 1116: 1112: 1108: 1104: 1085: 1075: 1071: 1062: 1059: 1056: 1053: 1045: 1033: 1029: 1024: 1016: 1015: 1014: 1012: 1008: 1001: 997: 993: 989: 983: 981: 977: 958: 955: 947: 938: 935: 931: 927: 924: 912: 909: 905: 897: 896: 895: 880: 816: 812: 807: 805: 801: 797: 793: 785: 782: 780: 776: 769: 762: 758: 753: 751: 747: 724: 714: 699: 695: 686: 678: 675: 672: 668: 664: 654: 639: 635: 626: 623: 613: 612: 611: 609: 601: 599: 595: 592: ∈  591: 587: 583: 579: 574: 572: 568: 548: 538: 523: 519: 510: 502: 497: 493: 487: 483: 476: 473: 470: 467: 460: 452: 451: 450: 448: 444: 441: ∈  440: 436: 429: 425: 420: 418: 414: 410: 406: 402: 398: 394: 390: 386: 383:-bounded and 382: 378: 374: 370: 366: 362: 358: 356: 352: 347: 343: 339: 335: 331: 323: 321: 319: 315: 311: 307: 303: 299: 295: 291: 286: 284: 280: 276: 274: 269: 250: 247: 235: 229: 216: 213: 210: 204: 200: 185: 182: 179: 173: 164: 157: 154: 151: 143: 137: 131: 128: 121: 120: 119: 117: 113: 109: 105: 101: 97: 93: 89: 85: 81: 77: 73: 69: 65: 61: 53: 51: 49: 45: 44:real analysis 41: 37: 34: 30: 19: 3230: 3223: 3219: 3212: 3201: 3194: 3169: 3165: 3155: 3143:. Retrieved 3139: 3100: 3097:dyadic cubes 3089: 3087: 2940: 2933: 2931: 2787: 2784: 2779: 2772: 2765: 2758: 2751: 2747: 2736: 2729: 2727: 2717: 2710: 2610: 2606: 2602: 2546: 2505: 2417: 2413: 2411: 2353: 2349: 2345: 2341: 2337: 2333: 2329: 2327: 2199: 2083: 2079: 2075: 2072: 2046: 2043:Applications 1962: 1957: 1953: 1946: 1944: 1642: 1458: 1456: 1330: 1326: 1322: 1318: 1314: 1310: 1306: 1302: 1298: 1294: 1292: 1151: 1147: 1140: 1133: 1126: 1122: 1118: 1114: 1110: 1106: 1102: 1100: 1010: 1009:centered at 1003: 999: 995: 991: 987: 985: 979: 975: 973: 814: 810: 809: 799: 791: 789: 778: 771: 764: 760: 756: 755: 742: 740: 604: 602: 597: 593: 589: 585: 581: 577: 576: 566: 564: 449:), we have: 446: 442: 438: 431: 427: 423: 422: 416: 412: 408: 404: 400: 396: 392: 388: 384: 380: 376: 372: 368: 364: 360: 354: 350: 337: 336:states that 327: 317: 313: 305: 301: 297: 293: 287: 282: 278: 277:of a subset 272: 267: 265: 118:. Formally, 115: 111: 107: 103: 99: 95: 87: 83: 79: 75: 71: 67: 63: 57: 35: 32: 26: 2744:Elias Stein 1333:, we have: 1113:varies in { 567:strong-type 330:G. H. Hardy 29:mathematics 3251:Categories 3140:What's New 3119:References 2788:uncentered 2724:Discussion 2035:. See the 1461:= 5. Then 1013:such that 990:such that 986:For every 310:measurable 290:continuous 54:Definition 3032:∫ 2987:∈ 2959:Δ 2876:∫ 2831:∈ 2806:∗ 2694:→ 2650:→ 2641:‖ 2634:− 2621:‖ 2565:→ 2530:→ 2521:‖ 2514:‖ 2485:‖ 2478:‖ 2473:ε 2459:≤ 2448:ε 2439:Ω 2394:Ω 2385:Ω 2376:Ω 2373:≤ 2367:Ω 2328:We write 2271:∫ 2161:→ 2150:− 2123:→ 2097:Ω 1919:‖ 1912:‖ 1866:− 1826:∫ 1820:∞ 1811:∫ 1736:∫ 1707:− 1694:∞ 1685:∫ 1678:≤ 1664:‖ 1654:‖ 1589:− 1576:∞ 1567:∫ 1540:− 1503:∫ 1499:∫ 1482:‖ 1472:‖ 1391:∫ 1372:≤ 1256:∫ 1236:≤ 1207:∑ 1193:≤ 1025:∫ 939:∈ 932:⋃ 928:⊂ 913:∈ 906:⋃ 691:‖ 684:‖ 665:≤ 631:‖ 621:‖ 515:‖ 508:‖ 503:λ 477:λ 201:∫ 62:function 3107:See also 1325:)| > 1146:covers { 948:′ 881:′ 379:is weak 66: : 42:used in 40:operator 2027:of the 998:) > 974:where 5 415:) > 342:bounded 266:where | 3145:22 May 3088:where 2941:dyadic 2340:where 2200:where 2086:) and 1317:) if | 1101:Thus { 811:Lemma. 31:, the 1457:with 1150:> 1117:> 1105:> 786:Proof 399:> 348:from 344:as a 3147:2011 2735:and 2445:> 1956:and 1843:> 1753:> 1611:> 1408:> 1358:> 1309:) = 1179:> 1060:> 813:Let 580:For 488:< 474:> 426:For 332:and 296:and 155:> 46:and 3174:doi 2980:sup 2824:sup 2761:p,d 2754:p,d 2732:p,d 2558:lim 2416:≤ 2 1301:by 978:is 767:p,d 745:p,d 607:p,d 600:), 340:is 292:in 148:sup 114:at 94:of 50:. 27:In 3253:: 3239:, 3224:73 3211:, 3193:, 3164:. 3138:. 3126:^ 2716:→ 2418:Mg 2348:∈ 2336:+ 2332:= 2078:∈ 1148:Mf 1115:Mf 1103:Mf 992:Mf 770:= 573:: 407:| 387:∈ 385:Mf 377:Mf 367:∈ 320:. 314:Mf 302:Mf 285:. 281:⊂ 106:, 88:Mf 82:∈ 76:Mf 70:→ 3182:. 3176:: 3170:7 3149:. 3101:x 3092:x 3090:Q 3073:y 3070:d 3066:| 3062:) 3059:y 3056:( 3053:f 3049:| 3041:x 3037:Q 3024:| 3018:x 3014:Q 3009:| 3004:1 2995:x 2991:Q 2984:x 2976:= 2973:) 2970:x 2967:( 2964:f 2955:M 2936:x 2934:B 2917:y 2914:d 2910:| 2906:) 2903:y 2900:( 2897:f 2893:| 2885:x 2881:B 2868:| 2862:x 2858:B 2853:| 2848:1 2839:x 2835:B 2828:x 2820:= 2817:) 2814:x 2811:( 2802:f 2780:p 2775:p 2773:C 2768:p 2766:C 2759:C 2752:C 2748:p 2739:d 2737:C 2730:C 2718:f 2713:r 2711:f 2697:f 2687:k 2683:r 2678:f 2665:( 2653:0 2645:1 2637:f 2629:r 2625:f 2611:x 2609:( 2607:f 2603:x 2589:) 2586:x 2583:( 2578:r 2574:f 2568:0 2562:r 2547:f 2533:0 2525:1 2517:g 2489:1 2481:g 2469:M 2465:2 2455:| 2451:} 2442:g 2436:{ 2432:| 2414:g 2397:g 2391:= 2388:h 2382:+ 2379:g 2370:f 2354:R 2352:( 2350:L 2346:g 2342:h 2338:g 2334:h 2330:f 2313:. 2310:y 2307:d 2304:) 2301:y 2298:( 2295:f 2290:) 2287:r 2284:, 2281:x 2278:( 2275:B 2263:| 2259:) 2256:r 2253:, 2250:x 2247:( 2244:B 2240:| 2235:1 2230:= 2227:) 2224:x 2221:( 2216:r 2212:f 2185:) 2182:x 2179:( 2174:r 2170:f 2164:0 2158:r 2147:) 2144:x 2141:( 2136:r 2132:f 2126:0 2120:r 2112:= 2109:) 2106:x 2103:( 2100:f 2084:R 2082:( 2080:L 2076:f 2009:d 2005:3 1982:d 1978:5 1974:= 1971:C 1958:d 1954:p 1949:p 1947:C 1928:p 1923:p 1915:f 1907:p 1903:C 1899:= 1896:t 1893:d 1890:x 1887:d 1883:| 1879:f 1875:| 1869:2 1863:p 1859:t 1851:2 1848:t 1839:| 1835:f 1831:| 1815:0 1807:p 1804:C 1801:2 1798:= 1795:t 1792:d 1788:) 1784:x 1781:d 1777:| 1773:f 1769:| 1761:2 1758:t 1749:| 1745:f 1741:| 1730:t 1726:C 1723:2 1716:( 1710:1 1704:p 1700:t 1689:0 1681:p 1673:p 1668:p 1660:f 1657:M 1628:t 1625:d 1621:| 1617:} 1614:t 1608:f 1605:M 1602:{ 1598:| 1592:1 1586:p 1582:t 1571:0 1563:p 1560:= 1557:x 1554:d 1551:t 1548:d 1543:1 1537:p 1533:t 1529:p 1524:) 1521:x 1518:( 1515:f 1512:M 1507:0 1496:= 1491:p 1486:p 1478:f 1475:M 1459:C 1442:, 1439:x 1436:d 1432:| 1428:f 1424:| 1416:2 1413:t 1404:| 1400:f 1396:| 1385:t 1381:C 1378:2 1368:| 1364:} 1361:t 1355:f 1352:M 1349:{ 1345:| 1331:b 1327:t 1323:x 1321:( 1319:f 1315:x 1313:( 1311:f 1307:x 1305:( 1303:b 1299:b 1295:L 1278:. 1275:y 1272:d 1268:| 1264:f 1260:| 1251:t 1246:d 1242:5 1232:| 1226:j 1222:B 1217:| 1211:j 1201:d 1197:5 1189:| 1185:} 1182:t 1176:f 1173:M 1170:{ 1166:| 1152:t 1143:j 1141:B 1136:j 1134:B 1129:x 1127:B 1123:x 1119:t 1111:x 1107:t 1086:. 1082:| 1076:x 1072:B 1067:| 1063:t 1057:y 1054:d 1050:| 1046:f 1042:| 1034:x 1030:B 1011:x 1006:x 1004:B 1000:t 996:x 994:( 988:x 980:B 976:B 959:B 956:5 945:F 936:B 925:B 918:F 910:B 876:F 851:F 827:F 815:X 800:p 792:p 781:. 779:d 774:p 772:C 765:C 761:p 743:C 725:. 720:) 715:d 710:R 705:( 700:p 696:L 687:f 679:d 676:, 673:p 669:C 660:) 655:d 650:R 645:( 640:p 636:L 627:f 624:M 605:C 598:R 596:( 594:L 590:f 586:p 582:d 549:. 544:) 539:d 534:R 529:( 524:1 520:L 511:f 498:d 494:C 484:| 480:} 471:f 468:M 465:{ 461:| 447:R 445:( 443:L 439:f 434:d 432:C 428:d 417:t 413:x 411:( 409:f 405:x 401:t 397:f 393:R 391:( 389:L 381:L 373:R 371:( 369:L 365:f 361:p 357:) 355:R 353:( 351:L 338:M 306:r 298:r 294:x 283:R 279:E 273:d 268:E 251:y 248:d 243:| 239:) 236:y 233:( 230:f 226:| 220:) 217:r 214:, 211:x 208:( 205:B 193:| 189:) 186:r 183:, 180:x 177:( 174:B 170:| 165:1 158:0 152:r 144:= 141:) 138:x 135:( 132:f 129:M 116:x 112:r 108:r 104:x 102:( 100:B 96:f 84:R 80:x 72:C 68:R 64:f 36:M 20:)

Index

Hardy-Littlewood maximal function
mathematics
operator
real analysis
harmonic analysis
locally integrable
average values
d-dimensional Lebesgue measure
continuous
measurable
G. H. Hardy
J. E. Littlewood
bounded
sublinear operator
L(R)
Marcinkiewicz interpolation theorem
Elias M. Stein
essential supremum
Vitali covering lemma
inner regularity
Lebesgue measure
Vitali covering lemma
Discussion section
Lebesgue differentiation theorem
Rademacher differentiation theorem
Fatou's theorem
Fractional integration theorem
approximation of the identity
Elias Stein
dyadic cubes

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