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Sunflower (mathematics)

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of a sunflower set is arranged in an intuitive way. Suppose the shared elements of a sunflower set are clumped together at the centre of the diagram, and the nonshared elements are distributed in a circular pattern around the shared elements. Then when the Venn diagram is completed, the lobe-shaped
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give successively weaker conditions which would imply the existence of a large sunflower in a given collection, with the latter being one of the most famous open problems of extremal combinatorics.
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A mathematical sunflower can be pictured as a flower. The kernel of the sunflower is the brown part in the middle, and each set of the sunflower is the union of a petal and the kernel.
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The study of sunflowers generally focuses on when set systems contain sunflowers, in particular, when a set system is sufficiently large to necessarily contain a sunflower.
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For any sunflower size, does every set of uniformly sized sets which is of cardinality greater than some exponential in the set size contain a sunflower?
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partitions. This implies that at least two sets and not all the sets will have an element in common. Hence this is not a sunflower of
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sets are selected from across multiple sets of the partition, then two must be selected from one partition since there are only
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subsets, which encircle the common elements and one or more unique elements, take on the appearance of the petals of a flower.
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subsets is also a sunflower. Similarly, a collection of sets each containing the same elements is also trivially a sunflower.
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sets if in one of the disjoint partitions is sunflower free by assumption of H being sunflower free. Otherwise, if
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Alweiss, Ryan; Lovett, Shachar; Wu, Kewen; Zhang, Jiapeng (June 2020), "Improved bounds for the sunflower lemma",
4537: 4700: 90: 4692: 2867: 3200:. A 2021 paper by Alweiss, Lovett, Wu, and Zhang gives the best progress towards the conjecture, proving that 2719:{\displaystyle |W|\leq \sum _{a\in A}|W_{a}|\leq |A|(f(k-1,r)-1)\leq k(r-1)f(k-1,r)-|A|\leq k(r-1)f(k-1,r)-1.} 4703:
algorithms for finding small sets of elements that contain at least one element from a given family of sets.
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The Sunflower Lemma of Erdős and Rado (Formal proof development in Isabelle/HOL, Archive of Formal Proofs)
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The main research question arising in relation to sunflowers is: under what conditions does there exist a
55: 6169: 4866: 4754:-system theorem states that a countable collection of k-sets contains a countably infinite sunflower or 5413: 4869:. It may for example be used as one of the ingredients in a proof showing that it is consistent with 3203: 3129: 2989: 4874: 4863: 4599:. For example, in 1986, Razborov used the sunflower lemma to prove that the Clique language required 1613: 5961:
Kostochka, Alexandr V. (2000), Althöfer, Ingo; Cai, Ning; Dueck, Gunter; Khachatrian, Levon (eds.),
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A month after the release of the first version of their paper, Rao sharpened the bound to
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The naming arises from a visual similarity to the botanical sunflower, arising when a
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theory at the time. Håstad, Jukna, and Pudlák used it to prove lower bounds on depth-
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at most once. By adding dummy elements, it suffices to only consider set systems
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Bell, Tolson; Chueluecha, Suchakree; Warnke, Lutz (2021), "Note on Sunflowers",
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The Erdős-Rado sunflower lemma can be proved directly through induction. First,
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is often assumed to be a set rather than a collection, so any set can appear in
5962: 5580: 3472:. It is equal to the statement that the original sunflower lemma is optimal in 5678: 5610:(1981), "Every large set of equidistant (0,+1,–1)-vectors forms a sunflower", 4855: 4805: 172: 51: 5686: 5633: 5532: 566: 6129: 5710: 5515:
Proceedings of the 52nd Annual ACM SIGACT Symposium on Theory of Computing
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sunflower (a sunflower with many sets) in a given collection of sets? The
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The best existing lower bound for the Erdos-Rado Sunflower problem for
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Collection of sets in which every two sets have the same intersection
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Flum, Jörg; Grohe, Martin (2006), "A Kernelization of Hitting Set",
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Shanin, N. A. (1946), "A theorem from the general theory of sets",
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on the size of a collection of pairwise incompatible elements in a
4638:(superpolynomial) size monotone circuits, a breakthrough result in 848:
Erdos-Rado Delta System Theorem(corollary of the Sunflower lemma):
6048: 5058:{\displaystyle \langle A_{\alpha }:\alpha <\omega _{2}\rangle } 41: 3080:. The conjecture remains wide open even for fixed low values of 2096:{\displaystyle W_{a}=\{S\setminus \{a\}\mid a\in S,\,S\in W\}.} 1610:
to be a maximal collection of pairwise disjoint sets (that is,
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of these sets make a sunflower. In the general case, suppose
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disjoint copies with the elements added and denote this set
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in which all possible distinct pairs of sets share the same
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must be a collection of distinct sets of size one, and so
5517:, Association for Computing Machinery, pp. 624–630, 2463:, and so it corresponds to at least one of the sets in a 5180:{\displaystyle f(\alpha )=\sup(A_{\alpha }\cap \alpha )} 5123:{\displaystyle \operatorname {cf} (\alpha )=\omega _{1}} 441:
share the same common subset of elements. An element in
1850:{\displaystyle A=A_{1}\cup A_{2}\cup \cdots \cup A_{t}} 5490:, so by further thinning we may stabilize the kernel. 3612:
sequence of distinct elements is not a sunflower. Let
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to every set. This means that, by our assumption that
5893: 5663:(1960), "Intersection theorems for systems of sets", 5476: 5449: 5416: 5391: 5365: 5338: 5304: 5284: 5264: 5244: 5217: 5197: 5136: 5091: 5071: 5019: 4999: 4972: 4945: 4914: 4894: 4837: 4814: 4784: 4760: 4740: 4718: 4667: 4648: 4605: 4540: 4514: 4461: 4441: 4421: 4394: 4367: 4330: 4310: 4283: 4263: 4236: 4216: 4110: 4084: 4058: 4038: 4018: 3991: 3923: 3896: 3870: 3850: 3823: 3797: 3777: 3751: 3725: 3705: 3685: 3659: 3618: 3592: 3566: 3501: 3478: 3443: 3388: 3335: 3255: 3206: 3180: 3132: 3106: 3086: 3066: 3040: 2992: 2966: 2870: 2850: 2830: 2810: 2735: 2499: 2469: 2449: 2422: 2396: 2346: 2319: 2299: 2279: 2259: 2239: 2212: 2186: 2159: 2139: 2112: 2030: 2001: 1974: 1930: 1910: 1890: 1863: 1798: 1769: 1749: 1729: 1702: 1682: 1656: 1616: 1551: 1531: 1511: 1491: 1471: 1424: 1401: 1381: 1336: 1316: 1292: 1272: 1200: 1162: 1142: 1122: 1102: 1082: 1062: 1039: 1019: 984: 964: 944: 909: 883: 857: 823: 803: 783: 763: 743: 723: 697: 677: 657: 628: 590: 551: 545:
subset, but not others. Note that this intersection,
531: 507: 487: 467: 447: 427: 407: 401:. In other words, a set system or collection of sets 375: 355: 335: 315: 292: 272: 250: 225: 205: 181: 157: 119: 69: 6083: 6035: 5948: 845:, the Delta System Theorem, indicates that it does. 3745:elements and add one element to each set in one of 3437:ErdĹ‘s and Rado proved the following lower bound on 5899: 5753:Set Theory: An Introduction to Independence Proofs 5482: 5462: 5443:. Using the continuum hypothesis, there are only 5435: 5402: 5377: 5351: 5321: 5290: 5270: 5250: 5230: 5203: 5179: 5122: 5077: 5057: 5005: 4985: 4958: 4927: 4900: 4843: 4820: 4790: 4766: 4746: 4734:which is essentially equivalent to the ErdĹ‘s-Rado 4724: 4683: 4654: 4630: 4579: 4526: 4497: 4447: 4427: 4407: 4380: 4353: 4316: 4296: 4269: 4249: 4222: 4200: 4090: 4070: 4044: 4024: 4004: 3977: 3909: 3882: 3856: 3836: 3809: 3783: 3763: 3737: 3711: 3691: 3671: 3645: 3604: 3578: 3550: 3484: 3464: 3418: 3374: 3319: 3240: 3192: 3166: 3118: 3092: 3072: 3052: 3026: 2978: 2956:is one of several variations of the conjecture of 2936: 2856: 2836: 2816: 2796: 2718: 2482: 2455: 2435: 2408: 2379: 2332: 2305: 2285: 2265: 2245: 2225: 2198: 2172: 2145: 2125: 2095: 2013: 1987: 1960: 1916: 1896: 1876: 1849: 1781: 1755: 1735: 1715: 1688: 1668: 1642: 1602: 1537: 1517: 1497: 1477: 1457: 1407: 1387: 1367: 1322: 1298: 1278: 1255: 1168: 1148: 1128: 1108: 1088: 1068: 1045: 1025: 1005: 970: 950: 930: 895: 869: 829: 809: 789: 769: 749: 729: 709: 683: 663: 648:, which is defined to be the smallest nonnegative 640: 611: 557: 537: 513: 493: 473: 453: 433: 413: 393: 361: 341: 321: 298: 278: 256: 231: 211: 187: 163: 125: 75: 5925:"Extremal Combinatorics III: Some Basic Theorems" 4595:The sunflower lemma has numerous applications in 4201:{\displaystyle f(a+b,r)\geq (f(a,r)-1)(f(b,r)-1)} 5152: 584:Specifically, researchers analyze the function 1603:{\displaystyle A_{1},A_{2},\ldots ,A_{t}\in W} 6096:Abbott, H.L; Hanson, D; Sauer, N (May 1972). 6003:Abbott, H.L; Hanson, D; Sauer, N (May 1972). 5969:, Boston, MA: Springer US, pp. 143–150, 4257:be two sunflower free families. For each set 3320:{\displaystyle C=O(r^{3}\log(k)\log \log(k))} 8: 5052: 5020: 4580:{\displaystyle 10^{\frac {k}{2}}\leq f(k,3)} 4101:A stronger result is the following theorem: 2087: 2059: 2053: 2044: 817:sets. Though it is not obvious that such an 6098:"Intersection theorems for systems of sets" 6005:"Intersection theorems for systems of sets" 5908: 5666:Journal of the London Mathematical Society 4691:circuits. It has also been applied in the 2206:elements. Furthermore, every sunflower of 6140: 6113: 6102:Journal of Combinatorial Theory, Series A 6020: 6009:Journal of Combinatorial Theory, Series A 5892: 5824: 5787: 5570: 5522: 5475: 5454: 5448: 5421: 5415: 5390: 5364: 5343: 5337: 5303: 5283: 5263: 5243: 5222: 5216: 5196: 5162: 5135: 5114: 5090: 5070: 5046: 5027: 5018: 4998: 4977: 4971: 4950: 4944: 4919: 4913: 4893: 4836: 4813: 4783: 4759: 4739: 4717: 4707:Analogue for infinite collections of sets 4675: 4666: 4647: 4610: 4604: 4545: 4539: 4513: 4490: 4482: 4477: 4471: 4462: 4460: 4440: 4420: 4399: 4393: 4372: 4366: 4346: 4340: 4331: 4329: 4309: 4288: 4282: 4262: 4241: 4235: 4215: 4109: 4083: 4057: 4037: 4017: 4012:is sunflower free since any selection of 3996: 3990: 3970: 3964: 3955: 3947: 3939: 3922: 3901: 3895: 3869: 3849: 3828: 3822: 3796: 3776: 3750: 3724: 3719:be such a set. Take an additional set of 3704: 3684: 3658: 3617: 3591: 3565: 3518: 3500: 3477: 3442: 3387: 3334: 3272: 3254: 3232: 3205: 3179: 3158: 3131: 3105: 3085: 3065: 3039: 3018: 2991: 2965: 2957: 2937:{\displaystyle f(k,r)\leq k(r-1)f(k-1,r)} 2869: 2849: 2829: 2809: 2744: 2736: 2734: 2660: 2652: 2563: 2555: 2547: 2541: 2532: 2520: 2508: 2500: 2498: 2474: 2468: 2448: 2427: 2421: 2395: 2345: 2324: 2318: 2298: 2278: 2258: 2238: 2217: 2211: 2185: 2164: 2158: 2138: 2117: 2111: 2077: 2035: 2029: 2000: 1979: 1973: 1929: 1909: 1889: 1868: 1862: 1841: 1822: 1809: 1797: 1768: 1748: 1728: 1707: 1701: 1681: 1655: 1634: 1621: 1615: 1588: 1569: 1556: 1550: 1530: 1510: 1490: 1470: 1423: 1400: 1380: 1359: 1335: 1315: 1291: 1271: 1244: 1199: 1184: 1161: 1141: 1121: 1101: 1081: 1061: 1038: 1018: 983: 963: 943: 908: 882: 856: 837:must exist, a basic and simple result of 822: 802: 782: 762: 742: 722: 696: 676: 656: 627: 589: 550: 530: 506: 486: 466: 446: 426: 406: 374: 354: 334: 314: 291: 271: 249: 224: 204: 180: 156: 118: 93:. This common intersection is called the 68: 6049:"Quanta Magazine - Illuminating Science" 5887:The original term for this concept was " 1330:of cardinality greater than or equal to 6130:https://mathoverflow.net/a/420288/12176 6128:Lower Bounds for the Sunflower Problem 5919: 5917: 5880: 5852:The sunflower lemma via Shannon entropy 2050: 1256:{\displaystyle f(k,r)\leq k!(r-1)^{k}.} 27:(more unsolved problems in mathematics) 4882: 4361:many sets. Denote this family of sets 3653:denote the size of the largest set of 2797:{\displaystyle |W|\geq k(r-1)f(k-1,r)} 481:or else appears in at most one of the 3551:{\displaystyle (r-1)^{k}\leq f(k,r).} 978:-sets is of cardinality greater than 461:is either found in the common subset 7: 6084:Bell, Chueluecha & Warnke (2021) 4877:does not hold. It was introduced by 3978:{\displaystyle (r-1)|H|\leq |H^{*}|} 6071: 5967:Numbers, Information and Complexity 4591:Applications of the sunflower lemma 1395:contains a sunflower with at least 5911:, has been gradually replacing it. 5894: 5000: 4838: 4815: 4785: 4761: 4741: 4719: 3382:; the current best-known bound is 251: 120: 70: 14: 4858:tool used in proofs to impose an 5963:"Extremal Problems on Δ-Systems" 5436:{\displaystyle A_{i}\subseteq j} 3241:{\displaystyle f(k,r)\leq C^{k}} 3167:{\displaystyle f(k,3)\leq C^{k}} 3027:{\displaystyle f(k,r)\leq C^{k}} 5835:C. R. (Doklady) Acad. Sci. URSS 5703:Parameterized Complexity Theory 2948:ErdĹ‘s-Rado sunflower conjecture 2153:, except that every element of 1643:{\displaystyle A_{i}\cap A_{j}} 141:ErdĹ‘s-Rado sunflower conjecture 18:Unsolved problem in mathematics 5806:"Sunflowers: from soil to oil" 5174: 5155: 5146: 5140: 5104: 5098: 4623: 4617: 4574: 4562: 4505:sets which is sunflower free. 4491: 4483: 4478: 4463: 4347: 4332: 4195: 4186: 4174: 4168: 4165: 4156: 4144: 4138: 4132: 4114: 3971: 3956: 3948: 3940: 3936: 3924: 3864:with an element added form an 3640: 3622: 3542: 3530: 3515: 3502: 3459: 3447: 3413: 3398: 3375:{\displaystyle C=O(r\log(rk))} 3369: 3366: 3357: 3345: 3314: 3311: 3305: 3290: 3284: 3265: 3222: 3210: 3148: 3136: 3008: 2996: 2931: 2913: 2907: 2895: 2886: 2874: 2791: 2773: 2767: 2755: 2745: 2737: 2707: 2689: 2683: 2671: 2661: 2653: 2646: 2628: 2622: 2610: 2601: 2592: 2574: 2568: 2564: 2556: 2548: 2533: 2509: 2501: 2368: 2350: 2233:corresponds to a sunflower of 1955: 1943: 1458:{\displaystyle f(1,r)\leq r-1} 1440: 1428: 1356: 1343: 1241: 1228: 1216: 1204: 1000: 988: 925: 913: 671:such that, for any set system 606: 594: 577:Sunflower lemma and conjecture 421:is a sunflower if all sets in 50:In the mathematical fields of 1: 5322:{\displaystyle S'\subseteq S} 1961:{\displaystyle kt\leq k(r-1)} 1033:contains a sunflower of size 6115:10.1016/0097-3165(72)90103-3 6022:10.1016/0097-3165(72)90103-3 5975:10.1007/978-1-4757-6048-4_14 5855:, What's new (personal blog) 4597:theoretical computer science 4455:. This produces a family of 3419:{\displaystyle C=O(r\log k)} 5470:-many countable subsets of 5463:{\displaystyle \omega _{1}} 5352:{\displaystyle \omega _{2}} 5231:{\displaystyle \omega _{2}} 4986:{\displaystyle \omega _{2}} 4959:{\displaystyle \omega _{2}} 4928:{\displaystyle \omega _{2}} 4871:Zermelo–Fraenkel set theory 4631:{\displaystyle n^{\log(n)}} 2416:intersects with one of the 1723:). Because we assumed that 1368:{\displaystyle k!(r-1)^{k}} 569:; a collection of pairwise 195:, that is, a collection of 6191: 5581:10.1016/j.disc.2021.112367 4498:{\displaystyle |F^{*}||F|} 4277:in F, append every set in 3126:; it is not known whether 2380:{\displaystyle f(k-1,r)-1} 938:such that if a set system 37:sunflower (disambiguation) 34: 4701:fixed-parameter tractable 2944:and the theorem follows. 2293:has no sunflower of size 1743:had no sunflower of size 394:{\displaystyle A\cap B=S} 5909:Deza & Frankl (1981) 5770:Rao, Anup (2020-02-25), 4808:contains an uncountable 4693:parameterized complexity 3791:. Take the union of the 3646:{\displaystyle h(k-1,r)} 2960:, p. 86) that for each 2253:, simply by adding back 1650:is the empty set unless 797:contains a sunflower of 717:has cardinality at most 501:elements. No element of 6141:Flum & Grohe (2006) 5900:{\displaystyle \Delta } 5772:"Coding for Sunflowers" 5679:10.1112/jlms/s1-35.1.85 5533:10.1145/3357713.3384234 5258:is constantly equal to 5006:{\displaystyle \Delta } 4844:{\displaystyle \Delta } 4821:{\displaystyle \Delta } 4791:{\displaystyle \Delta } 4767:{\displaystyle \Delta } 4747:{\displaystyle \Delta } 4725:{\displaystyle \Delta } 4354:{\displaystyle |F^{*}|} 2443:'s, it intersects with 1465:, since the set system 1375:of sets of cardinality 1176:-uniform" set systems. 1116:such that every set in 266:) if there is a subset 257:{\displaystyle \Delta } 126:{\displaystyle \Delta } 76:{\displaystyle \Delta } 5929:Combinatorics and more 5901: 5813:Bull. Amer. Math. Soc. 5484: 5483:{\displaystyle \beta } 5464: 5437: 5404: 5379: 5378:{\displaystyle i<j} 5353: 5323: 5292: 5272: 5271:{\displaystyle \beta } 5252: 5232: 5205: 5181: 5124: 5079: 5059: 5007: 4987: 4960: 4929: 4902: 4845: 4822: 4792: 4768: 4748: 4726: 4685: 4684:{\displaystyle AC_{0}} 4656: 4632: 4581: 4528: 4499: 4449: 4429: 4409: 4382: 4355: 4318: 4298: 4271: 4251: 4224: 4202: 4092: 4072: 4046: 4026: 4006: 3979: 3911: 3884: 3858: 3838: 3811: 3785: 3765: 3739: 3713: 3693: 3673: 3647: 3606: 3580: 3552: 3486: 3466: 3465:{\displaystyle f(k,r)} 3433:Sunflower lower bounds 3420: 3376: 3321: 3242: 3194: 3193:{\displaystyle C>0} 3168: 3120: 3094: 3074: 3054: 3053:{\displaystyle C>0} 3028: 2980: 2979:{\displaystyle r>2} 2958:ErdĹ‘s & Rado (1960 2938: 2858: 2844:set sunflower of size 2838: 2818: 2798: 2720: 2484: 2457: 2437: 2410: 2409:{\displaystyle S\in W} 2381: 2334: 2307: 2287: 2267: 2247: 2227: 2200: 2174: 2147: 2133:is a set system, like 2127: 2097: 2015: 2014:{\displaystyle a\in A} 1989: 1962: 1918: 1898: 1878: 1851: 1783: 1782:{\displaystyle t<r} 1757: 1737: 1717: 1690: 1670: 1644: 1604: 1539: 1525:has no sunflower with 1519: 1499: 1479: 1459: 1409: 1389: 1369: 1324: 1300: 1280: 1257: 1185:ErdĹ‘s & Rado (1960 1170: 1150: 1130: 1110: 1090: 1070: 1047: 1027: 1007: 1006:{\displaystyle f(k,r)} 972: 952: 932: 931:{\displaystyle f(k,r)} 903:, there is an integer 897: 896:{\displaystyle r>0} 871: 870:{\displaystyle k>0} 831: 811: 791: 771: 751: 731: 711: 710:{\displaystyle S\in W} 685: 665: 642: 613: 612:{\displaystyle f(k,r)} 559: 539: 515: 495: 475: 455: 435: 415: 395: 363: 343: 323: 300: 280: 258: 233: 213: 189: 165: 127: 77: 56:extremal combinatorics 47: 6160:Forcing (mathematics) 6036:Alweiss et al. (2020) 5949:Alweiss et al. (2020) 5902: 5711:10.1007/3-540-29953-X 5485: 5465: 5438: 5405: 5380: 5354: 5324: 5293: 5273: 5253: 5233: 5206: 5182: 5125: 5080: 5060: 5008: 4988: 4961: 4935:-sized collection of 4930: 4903: 4846: 4823: 4793: 4769: 4749: 4727: 4686: 4657: 4633: 4582: 4529: 4500: 4450: 4430: 4410: 4408:{\displaystyle F_{A}} 4383: 4381:{\displaystyle F_{A}} 4356: 4319: 4299: 4297:{\displaystyle F^{*}} 4272: 4252: 4250:{\displaystyle F^{*}} 4225: 4203: 4093: 4073: 4047: 4027: 4007: 4005:{\displaystyle H^{*}} 3980: 3912: 3910:{\displaystyle H^{*}} 3885: 3859: 3839: 3837:{\displaystyle H^{*}} 3812: 3786: 3766: 3740: 3714: 3694: 3674: 3648: 3607: 3581: 3553: 3487: 3467: 3421: 3377: 3322: 3243: 3195: 3169: 3121: 3095: 3075: 3055: 3029: 2981: 2939: 2859: 2839: 2819: 2799: 2721: 2485: 2483:{\displaystyle W_{a}} 2458: 2438: 2436:{\displaystyle A_{i}} 2411: 2382: 2335: 2333:{\displaystyle W_{a}} 2308: 2288: 2268: 2248: 2228: 2226:{\displaystyle W_{a}} 2201: 2175: 2173:{\displaystyle W_{a}} 2148: 2128: 2126:{\displaystyle W_{a}} 2098: 2016: 1990: 1988:{\displaystyle W_{a}} 1963: 1919: 1904:, the cardinality of 1899: 1879: 1877:{\displaystyle A_{i}} 1852: 1784: 1758: 1738: 1718: 1716:{\displaystyle A_{i}} 1696:intersects with some 1691: 1671: 1645: 1605: 1540: 1520: 1500: 1480: 1460: 1410: 1390: 1370: 1325: 1301: 1281: 1258: 1171: 1151: 1131: 1111: 1091: 1071: 1048: 1028: 1008: 973: 953: 933: 898: 872: 832: 812: 792: 772: 752: 732: 712: 686: 666: 643: 614: 560: 540: 516: 496: 476: 456: 436: 416: 396: 364: 344: 324: 301: 281: 259: 234: 214: 190: 166: 128: 78: 45: 5891: 5559:Discrete Mathematics 5474: 5447: 5414: 5389: 5363: 5336: 5302: 5282: 5262: 5242: 5215: 5195: 5134: 5089: 5069: 5017: 4997: 4970: 4943: 4912: 4892: 4875:continuum hypothesis 4835: 4812: 4782: 4758: 4738: 4716: 4665: 4646: 4603: 4538: 4512: 4459: 4439: 4419: 4392: 4388:. Take the union of 4365: 4328: 4308: 4281: 4261: 4234: 4214: 4108: 4082: 4056: 4036: 4016: 3989: 3921: 3894: 3868: 3848: 3821: 3795: 3775: 3749: 3723: 3703: 3683: 3657: 3616: 3590: 3564: 3499: 3476: 3441: 3386: 3333: 3253: 3204: 3178: 3130: 3104: 3084: 3064: 3038: 2990: 2964: 2954:sunflower conjecture 2868: 2848: 2828: 2808: 2733: 2497: 2467: 2447: 2420: 2394: 2344: 2317: 2297: 2277: 2257: 2237: 2210: 2184: 2157: 2137: 2110: 2028: 1999: 1972: 1928: 1908: 1888: 1861: 1796: 1767: 1747: 1727: 1700: 1680: 1654: 1614: 1549: 1545:sets. Then consider 1529: 1509: 1489: 1469: 1422: 1399: 1379: 1334: 1314: 1310:, then a set system 1290: 1270: 1198: 1191:, which states that 1187:, p. 86) proved the 1160: 1140: 1120: 1100: 1080: 1060: 1037: 1017: 982: 962: 942: 907: 881: 855: 821: 801: 781: 761: 741: 721: 695: 691:such that every set 675: 655: 626: 588: 549: 529: 505: 485: 465: 445: 425: 405: 373: 353: 333: 313: 290: 270: 248: 223: 203: 179: 155: 117: 67: 35:For other uses, see 5931:. 28 September 2008 5359:such that whenever 4697:hitting set problem 4527:{\displaystyle r=3} 4071:{\displaystyle r-1} 3883:{\displaystyle r-1} 3810:{\displaystyle r-1} 3771:disjoint copies of 3764:{\displaystyle r-1} 3738:{\displaystyle r-1} 3672:{\displaystyle k-1} 3605:{\displaystyle r-1} 3579:{\displaystyle k=1} 3119:{\displaystyle r=3} 2340:must be bounded by 2199:{\displaystyle k-1} 1676:, and every set in 1669:{\displaystyle i=j} 1056:In the literature, 641:{\displaystyle k,r} 306:such that for each 85:is a collection of 5897: 5804:Rao, Anup (2023), 5626:10.1007/BF02579328 5480: 5460: 5433: 5403:{\displaystyle S'} 5400: 5375: 5349: 5319: 5288: 5268: 5248: 5228: 5201: 5177: 5120: 5075: 5055: 5003: 4983: 4956: 4925: 4898: 4841: 4818: 4800:states that every 4788: 4764: 4744: 4722: 4681: 4652: 4640:circuit complexity 4628: 4577: 4524: 4495: 4445: 4425: 4405: 4378: 4351: 4314: 4294: 4267: 4247: 4220: 4198: 4088: 4068: 4042: 4022: 4002: 3975: 3907: 3880: 3854: 3834: 3807: 3781: 3761: 3735: 3709: 3689: 3669: 3643: 3602: 3576: 3548: 3482: 3462: 3416: 3372: 3317: 3238: 3190: 3164: 3116: 3090: 3070: 3060:depending only on 3050: 3034:for some constant 3024: 2976: 2934: 2854: 2834: 2814: 2794: 2716: 2531: 2480: 2453: 2433: 2406: 2377: 2330: 2303: 2283: 2263: 2243: 2223: 2196: 2170: 2143: 2123: 2093: 2011: 1985: 1958: 1914: 1894: 1874: 1847: 1779: 1753: 1733: 1713: 1686: 1666: 1640: 1600: 1535: 1515: 1495: 1475: 1455: 1405: 1385: 1365: 1320: 1296: 1276: 1253: 1166: 1146: 1126: 1106: 1086: 1066: 1043: 1023: 1003: 968: 948: 928: 893: 867: 827: 807: 787: 767: 747: 727: 707: 681: 661: 638: 609: 555: 535: 521:is shared by just 511: 491: 471: 451: 431: 411: 391: 359: 339: 319: 296: 276: 254: 229: 209: 185: 161: 123: 97:of the sunflower. 73: 48: 5984:978-1-4757-6048-4 5826:10.1090/bull/1777 5789:10.19086/da.11887 5776:Discrete Analysis 5763:978-0-444-85401-8 5756:, North-Holland, 5720:978-3-540-29952-3 5669:, Second Series, 5542:978-1-4503-6979-4 5291:{\displaystyle S} 5251:{\displaystyle f} 5204:{\displaystyle S} 5078:{\displaystyle W} 4901:{\displaystyle W} 4711:A version of the 4655:{\displaystyle 3} 4553: 4448:{\displaystyle F} 4428:{\displaystyle A} 4317:{\displaystyle A} 4270:{\displaystyle A} 4223:{\displaystyle F} 4091:{\displaystyle r} 4045:{\displaystyle r} 4025:{\displaystyle r} 3857:{\displaystyle H} 3784:{\displaystyle H} 3712:{\displaystyle H} 3692:{\displaystyle r} 3485:{\displaystyle r} 3093:{\displaystyle r} 3073:{\displaystyle r} 2857:{\displaystyle k} 2837:{\displaystyle r} 2817:{\displaystyle W} 2516: 2456:{\displaystyle A} 2306:{\displaystyle r} 2286:{\displaystyle W} 2266:{\displaystyle a} 2246:{\displaystyle W} 2146:{\displaystyle W} 1917:{\displaystyle A} 1897:{\displaystyle k} 1756:{\displaystyle r} 1736:{\displaystyle W} 1689:{\displaystyle W} 1538:{\displaystyle r} 1518:{\displaystyle W} 1498:{\displaystyle r} 1478:{\displaystyle W} 1408:{\displaystyle r} 1388:{\displaystyle k} 1323:{\displaystyle W} 1299:{\displaystyle r} 1279:{\displaystyle k} 1169:{\displaystyle k} 1149:{\displaystyle k} 1129:{\displaystyle W} 1109:{\displaystyle W} 1089:{\displaystyle W} 1069:{\displaystyle W} 1046:{\displaystyle r} 1026:{\displaystyle F} 971:{\displaystyle k} 951:{\displaystyle F} 830:{\displaystyle n} 810:{\displaystyle r} 790:{\displaystyle W} 770:{\displaystyle n} 750:{\displaystyle W} 730:{\displaystyle k} 684:{\displaystyle W} 664:{\displaystyle n} 558:{\displaystyle S} 538:{\displaystyle W} 514:{\displaystyle U} 494:{\displaystyle W} 474:{\displaystyle S} 454:{\displaystyle U} 434:{\displaystyle W} 414:{\displaystyle W} 362:{\displaystyle W} 342:{\displaystyle B} 322:{\displaystyle A} 299:{\displaystyle U} 279:{\displaystyle S} 232:{\displaystyle W} 219:. The collection 212:{\displaystyle U} 188:{\displaystyle U} 164:{\displaystyle W} 147:Formal definition 6182: 6144: 6138: 6132: 6126: 6120: 6119: 6117: 6093: 6087: 6081: 6075: 6069: 6063: 6062: 6060: 6059: 6045: 6039: 6033: 6027: 6026: 6024: 6000: 5994: 5993: 5992: 5991: 5958: 5952: 5946: 5940: 5939: 5937: 5936: 5921: 5912: 5906: 5904: 5903: 5898: 5885: 5867:Thiemann, RenĂ©. 5856: 5842: 5829: 5828: 5810: 5800: 5791: 5766: 5743: 5731: 5697: 5652: 5599: 5574: 5553: 5526: 5489: 5487: 5486: 5481: 5469: 5467: 5466: 5461: 5459: 5458: 5442: 5440: 5439: 5434: 5426: 5425: 5409: 5407: 5406: 5401: 5399: 5384: 5382: 5381: 5376: 5358: 5356: 5355: 5350: 5348: 5347: 5328: 5326: 5325: 5320: 5312: 5297: 5295: 5294: 5289: 5277: 5275: 5274: 5269: 5257: 5255: 5254: 5249: 5237: 5235: 5234: 5229: 5227: 5226: 5210: 5208: 5207: 5202: 5186: 5184: 5183: 5178: 5167: 5166: 5129: 5127: 5126: 5121: 5119: 5118: 5084: 5082: 5081: 5076: 5064: 5062: 5061: 5056: 5051: 5050: 5032: 5031: 5013:-subsystem. Let 5012: 5010: 5009: 5004: 4992: 4990: 4989: 4984: 4982: 4981: 4965: 4963: 4962: 4957: 4955: 4954: 4934: 4932: 4931: 4926: 4924: 4923: 4907: 4905: 4904: 4899: 4850: 4848: 4847: 4842: 4827: 4825: 4824: 4819: 4797: 4795: 4794: 4789: 4773: 4771: 4770: 4765: 4753: 4751: 4750: 4745: 4731: 4729: 4728: 4723: 4690: 4688: 4687: 4682: 4680: 4679: 4661: 4659: 4658: 4653: 4637: 4635: 4634: 4629: 4627: 4626: 4586: 4584: 4583: 4578: 4555: 4554: 4546: 4533: 4531: 4530: 4525: 4504: 4502: 4501: 4496: 4494: 4486: 4481: 4476: 4475: 4466: 4454: 4452: 4451: 4446: 4434: 4432: 4431: 4426: 4414: 4412: 4411: 4406: 4404: 4403: 4387: 4385: 4384: 4379: 4377: 4376: 4360: 4358: 4357: 4352: 4350: 4345: 4344: 4335: 4323: 4321: 4320: 4315: 4303: 4301: 4300: 4295: 4293: 4292: 4276: 4274: 4273: 4268: 4256: 4254: 4253: 4248: 4246: 4245: 4229: 4227: 4226: 4221: 4207: 4205: 4204: 4199: 4097: 4095: 4094: 4089: 4077: 4075: 4074: 4069: 4051: 4049: 4048: 4043: 4031: 4029: 4028: 4023: 4011: 4009: 4008: 4003: 4001: 4000: 3984: 3982: 3981: 3976: 3974: 3969: 3968: 3959: 3951: 3943: 3916: 3914: 3913: 3908: 3906: 3905: 3889: 3887: 3886: 3881: 3863: 3861: 3860: 3855: 3844:. The copies of 3843: 3841: 3840: 3835: 3833: 3832: 3816: 3814: 3813: 3808: 3790: 3788: 3787: 3782: 3770: 3768: 3767: 3762: 3744: 3742: 3741: 3736: 3718: 3716: 3715: 3710: 3698: 3696: 3695: 3690: 3678: 3676: 3675: 3670: 3652: 3650: 3649: 3644: 3611: 3609: 3608: 3603: 3585: 3583: 3582: 3577: 3557: 3555: 3554: 3549: 3523: 3522: 3491: 3489: 3488: 3483: 3471: 3469: 3468: 3463: 3425: 3423: 3422: 3417: 3381: 3379: 3378: 3373: 3328: 3326: 3324: 3323: 3318: 3277: 3276: 3247: 3245: 3244: 3239: 3237: 3236: 3199: 3197: 3196: 3191: 3173: 3171: 3170: 3165: 3163: 3162: 3125: 3123: 3122: 3117: 3099: 3097: 3096: 3091: 3079: 3077: 3076: 3071: 3059: 3057: 3056: 3051: 3033: 3031: 3030: 3025: 3023: 3022: 2985: 2983: 2982: 2977: 2943: 2941: 2940: 2935: 2863: 2861: 2860: 2855: 2843: 2841: 2840: 2835: 2823: 2821: 2820: 2815: 2803: 2801: 2800: 2795: 2748: 2740: 2725: 2723: 2722: 2717: 2664: 2656: 2567: 2559: 2551: 2546: 2545: 2536: 2530: 2512: 2504: 2489: 2487: 2486: 2481: 2479: 2478: 2462: 2460: 2459: 2454: 2442: 2440: 2439: 2434: 2432: 2431: 2415: 2413: 2412: 2407: 2390:Since every set 2386: 2384: 2383: 2378: 2339: 2337: 2336: 2331: 2329: 2328: 2312: 2310: 2309: 2304: 2292: 2290: 2289: 2284: 2272: 2270: 2269: 2264: 2252: 2250: 2249: 2244: 2232: 2230: 2229: 2224: 2222: 2221: 2205: 2203: 2202: 2197: 2179: 2177: 2176: 2171: 2169: 2168: 2152: 2150: 2149: 2144: 2132: 2130: 2129: 2124: 2122: 2121: 2102: 2100: 2099: 2094: 2040: 2039: 2020: 2018: 2017: 2012: 1994: 1992: 1991: 1986: 1984: 1983: 1967: 1965: 1964: 1959: 1923: 1921: 1920: 1915: 1903: 1901: 1900: 1895: 1884:has cardinality 1883: 1881: 1880: 1875: 1873: 1872: 1856: 1854: 1853: 1848: 1846: 1845: 1827: 1826: 1814: 1813: 1788: 1786: 1785: 1780: 1762: 1760: 1759: 1754: 1742: 1740: 1739: 1734: 1722: 1720: 1719: 1714: 1712: 1711: 1695: 1693: 1692: 1687: 1675: 1673: 1672: 1667: 1649: 1647: 1646: 1641: 1639: 1638: 1626: 1625: 1609: 1607: 1606: 1601: 1593: 1592: 1574: 1573: 1561: 1560: 1544: 1542: 1541: 1536: 1524: 1522: 1521: 1516: 1504: 1502: 1501: 1496: 1484: 1482: 1481: 1476: 1464: 1462: 1461: 1456: 1414: 1412: 1411: 1406: 1394: 1392: 1391: 1386: 1374: 1372: 1371: 1366: 1364: 1363: 1329: 1327: 1326: 1321: 1305: 1303: 1302: 1297: 1285: 1283: 1282: 1277: 1262: 1260: 1259: 1254: 1249: 1248: 1175: 1173: 1172: 1167: 1155: 1153: 1152: 1147: 1136:has cardinality 1135: 1133: 1132: 1127: 1115: 1113: 1112: 1107: 1095: 1093: 1092: 1087: 1075: 1073: 1072: 1067: 1052: 1050: 1049: 1044: 1032: 1030: 1029: 1024: 1012: 1010: 1009: 1004: 977: 975: 974: 969: 957: 955: 954: 949: 937: 935: 934: 929: 902: 900: 899: 894: 876: 874: 873: 868: 836: 834: 833: 828: 816: 814: 813: 808: 796: 794: 793: 788: 776: 774: 773: 768: 756: 754: 753: 748: 736: 734: 733: 728: 716: 714: 713: 708: 690: 688: 687: 682: 670: 668: 667: 662: 647: 645: 644: 639: 619:for nonnegative 618: 616: 615: 610: 564: 562: 561: 556: 544: 542: 541: 536: 520: 518: 517: 512: 500: 498: 497: 492: 480: 478: 477: 472: 460: 458: 457: 452: 440: 438: 437: 432: 420: 418: 417: 412: 400: 398: 397: 392: 368: 366: 365: 360: 348: 346: 345: 340: 328: 326: 325: 320: 305: 303: 302: 297: 285: 283: 282: 277: 263: 261: 260: 255: 238: 236: 235: 230: 218: 216: 215: 210: 194: 192: 191: 186: 170: 168: 167: 162: 132: 130: 129: 124: 82: 80: 79: 74: 19: 6190: 6189: 6185: 6184: 6183: 6181: 6180: 6179: 6150: 6149: 6148: 6147: 6139: 6135: 6127: 6123: 6095: 6094: 6090: 6082: 6078: 6070: 6066: 6057: 6055: 6053:Quanta Magazine 6047: 6046: 6042: 6034: 6030: 6002: 6001: 5997: 5989: 5987: 5985: 5960: 5959: 5955: 5947: 5943: 5934: 5932: 5923: 5922: 5915: 5889: 5888: 5886: 5882: 5877: 5864: 5859: 5845: 5832: 5808: 5803: 5769: 5764: 5746: 5734: 5721: 5700: 5655: 5602: 5556: 5543: 5512: 5508: 5496: 5472: 5471: 5450: 5445: 5444: 5417: 5412: 5411: 5392: 5387: 5386: 5361: 5360: 5339: 5334: 5333: 5305: 5300: 5299: 5280: 5279: 5260: 5259: 5240: 5239: 5218: 5213: 5212: 5193: 5192: 5158: 5132: 5131: 5110: 5087: 5086: 5067: 5066: 5042: 5023: 5015: 5014: 4995: 4994: 4973: 4968: 4967: 4946: 4941: 4940: 4915: 4910: 4909: 4890: 4889: 4833: 4832: 4810: 4809: 4780: 4779: 4756: 4755: 4736: 4735: 4714: 4713: 4709: 4671: 4663: 4662: 4644: 4643: 4606: 4601: 4600: 4593: 4541: 4536: 4535: 4510: 4509: 4467: 4457: 4456: 4437: 4436: 4417: 4416: 4395: 4390: 4389: 4368: 4363: 4362: 4336: 4326: 4325: 4306: 4305: 4284: 4279: 4278: 4259: 4258: 4237: 4232: 4231: 4212: 4211: 4106: 4105: 4080: 4079: 4054: 4053: 4034: 4033: 4014: 4013: 3992: 3987: 3986: 3960: 3919: 3918: 3917:. We have that, 3897: 3892: 3891: 3866: 3865: 3846: 3845: 3824: 3819: 3818: 3793: 3792: 3773: 3772: 3747: 3746: 3721: 3720: 3701: 3700: 3699:sunflower. Let 3681: 3680: 3655: 3654: 3614: 3613: 3588: 3587: 3562: 3561: 3514: 3497: 3496: 3474: 3473: 3439: 3438: 3435: 3429: 3384: 3383: 3331: 3330: 3268: 3251: 3250: 3249: 3228: 3202: 3201: 3176: 3175: 3154: 3128: 3127: 3102: 3101: 3082: 3081: 3062: 3061: 3036: 3035: 3014: 2988: 2987: 2962: 2961: 2950: 2866: 2865: 2846: 2845: 2826: 2825: 2806: 2805: 2731: 2730: 2537: 2495: 2494: 2470: 2465: 2464: 2445: 2444: 2423: 2418: 2417: 2392: 2391: 2342: 2341: 2320: 2315: 2314: 2295: 2294: 2275: 2274: 2255: 2254: 2235: 2234: 2213: 2208: 2207: 2182: 2181: 2160: 2155: 2154: 2135: 2134: 2113: 2108: 2107: 2031: 2026: 2025: 1997: 1996: 1975: 1970: 1969: 1926: 1925: 1906: 1905: 1886: 1885: 1864: 1859: 1858: 1837: 1818: 1805: 1794: 1793: 1765: 1764: 1745: 1744: 1725: 1724: 1703: 1698: 1697: 1678: 1677: 1652: 1651: 1630: 1617: 1612: 1611: 1584: 1565: 1552: 1547: 1546: 1527: 1526: 1507: 1506: 1487: 1486: 1467: 1466: 1420: 1419: 1397: 1396: 1377: 1376: 1355: 1332: 1331: 1312: 1311: 1288: 1287: 1268: 1267: 1240: 1196: 1195: 1189:sunflower lemma 1182: 1180:Sunflower lemma 1158: 1157: 1138: 1137: 1118: 1117: 1098: 1097: 1078: 1077: 1058: 1057: 1035: 1034: 1015: 1014: 980: 979: 960: 959: 940: 939: 905: 904: 879: 878: 853: 852: 819: 818: 799: 798: 779: 778: 759: 758: 739: 738: 719: 718: 693: 692: 673: 672: 653: 652: 624: 623: 586: 585: 579: 547: 546: 527: 526: 503: 502: 483: 482: 463: 462: 443: 442: 423: 422: 403: 402: 371: 370: 351: 350: 331: 330: 311: 310: 288: 287: 268: 267: 246: 245: 221: 220: 201: 200: 177: 176: 153: 152: 149: 137:sunflower lemma 115: 114: 65: 64: 40: 33: 30: 29: 24: 21: 17: 12: 11: 5: 6188: 6186: 6178: 6177: 6172: 6167: 6162: 6152: 6151: 6146: 6145: 6133: 6121: 6108:(3): 381–389. 6088: 6076: 6064: 6040: 6028: 6015:(3): 381–389. 5995: 5983: 5953: 5941: 5913: 5896: 5879: 5878: 5876: 5873: 5872: 5871: 5863: 5862:External links 5860: 5858: 5857: 5843: 5837:, New Series, 5830: 5801: 5767: 5762: 5748:Kunen, Kenneth 5744: 5732: 5719: 5698: 5653: 5620:(3): 225–231, 5600: 5554: 5541: 5509: 5507: 5504: 5503: 5502: 5495: 5492: 5479: 5457: 5453: 5432: 5429: 5424: 5420: 5398: 5395: 5374: 5371: 5368: 5346: 5342: 5318: 5315: 5311: 5308: 5287: 5267: 5247: 5225: 5221: 5211:stationary in 5200: 5176: 5173: 5170: 5165: 5161: 5157: 5154: 5151: 5148: 5145: 5142: 5139: 5117: 5113: 5109: 5106: 5103: 5100: 5097: 5094: 5074: 5054: 5049: 5045: 5041: 5038: 5035: 5030: 5026: 5022: 5002: 4980: 4976: 4953: 4949: 4922: 4918: 4897: 4840: 4817: 4804:collection of 4787: 4763: 4743: 4721: 4708: 4705: 4678: 4674: 4670: 4651: 4625: 4622: 4619: 4616: 4613: 4609: 4592: 4589: 4576: 4573: 4570: 4567: 4564: 4561: 4558: 4552: 4549: 4544: 4523: 4520: 4517: 4493: 4489: 4485: 4480: 4474: 4470: 4465: 4444: 4424: 4402: 4398: 4375: 4371: 4349: 4343: 4339: 4334: 4313: 4291: 4287: 4266: 4244: 4240: 4219: 4197: 4194: 4191: 4188: 4185: 4182: 4179: 4176: 4173: 4170: 4167: 4164: 4161: 4158: 4155: 4152: 4149: 4146: 4143: 4140: 4137: 4134: 4131: 4128: 4125: 4122: 4119: 4116: 4113: 4087: 4067: 4064: 4061: 4041: 4021: 3999: 3995: 3973: 3967: 3963: 3958: 3954: 3950: 3946: 3942: 3938: 3935: 3932: 3929: 3926: 3904: 3900: 3879: 3876: 3873: 3853: 3831: 3827: 3806: 3803: 3800: 3780: 3760: 3757: 3754: 3734: 3731: 3728: 3708: 3688: 3679:-sets with no 3668: 3665: 3662: 3642: 3639: 3636: 3633: 3630: 3627: 3624: 3621: 3601: 3598: 3595: 3575: 3572: 3569: 3547: 3544: 3541: 3538: 3535: 3532: 3529: 3526: 3521: 3517: 3513: 3510: 3507: 3504: 3481: 3461: 3458: 3455: 3452: 3449: 3446: 3434: 3431: 3415: 3412: 3409: 3406: 3403: 3400: 3397: 3394: 3391: 3371: 3368: 3365: 3362: 3359: 3356: 3353: 3350: 3347: 3344: 3341: 3338: 3316: 3313: 3310: 3307: 3304: 3301: 3298: 3295: 3292: 3289: 3286: 3283: 3280: 3275: 3271: 3267: 3264: 3261: 3258: 3235: 3231: 3227: 3224: 3221: 3218: 3215: 3212: 3209: 3189: 3186: 3183: 3161: 3157: 3153: 3150: 3147: 3144: 3141: 3138: 3135: 3115: 3112: 3109: 3100:; for example 3089: 3069: 3049: 3046: 3043: 3021: 3017: 3013: 3010: 3007: 3004: 3001: 2998: 2995: 2975: 2972: 2969: 2949: 2946: 2933: 2930: 2927: 2924: 2921: 2918: 2915: 2912: 2909: 2906: 2903: 2900: 2897: 2894: 2891: 2888: 2885: 2882: 2879: 2876: 2873: 2853: 2833: 2813: 2793: 2790: 2787: 2784: 2781: 2778: 2775: 2772: 2769: 2766: 2763: 2760: 2757: 2754: 2751: 2747: 2743: 2739: 2727: 2726: 2715: 2712: 2709: 2706: 2703: 2700: 2697: 2694: 2691: 2688: 2685: 2682: 2679: 2676: 2673: 2670: 2667: 2663: 2659: 2655: 2651: 2648: 2645: 2642: 2639: 2636: 2633: 2630: 2627: 2624: 2621: 2618: 2615: 2612: 2609: 2606: 2603: 2600: 2597: 2594: 2591: 2588: 2585: 2582: 2579: 2576: 2573: 2570: 2566: 2562: 2558: 2554: 2550: 2544: 2540: 2535: 2529: 2526: 2523: 2519: 2515: 2511: 2507: 2503: 2477: 2473: 2452: 2430: 2426: 2405: 2402: 2399: 2376: 2373: 2370: 2367: 2364: 2361: 2358: 2355: 2352: 2349: 2327: 2323: 2313:, the size of 2302: 2282: 2262: 2242: 2220: 2216: 2195: 2192: 2189: 2167: 2163: 2142: 2120: 2116: 2104: 2103: 2092: 2089: 2086: 2083: 2080: 2076: 2073: 2070: 2067: 2064: 2061: 2058: 2055: 2052: 2049: 2046: 2043: 2038: 2034: 2010: 2007: 2004: 1982: 1978: 1957: 1954: 1951: 1948: 1945: 1942: 1939: 1936: 1933: 1924:is bounded by 1913: 1893: 1871: 1867: 1844: 1840: 1836: 1833: 1830: 1825: 1821: 1817: 1812: 1808: 1804: 1801: 1778: 1775: 1772: 1752: 1732: 1710: 1706: 1685: 1665: 1662: 1659: 1637: 1633: 1629: 1624: 1620: 1599: 1596: 1591: 1587: 1583: 1580: 1577: 1572: 1568: 1564: 1559: 1555: 1534: 1514: 1494: 1474: 1454: 1451: 1448: 1445: 1442: 1439: 1436: 1433: 1430: 1427: 1404: 1384: 1362: 1358: 1354: 1351: 1348: 1345: 1342: 1339: 1319: 1295: 1275: 1264: 1263: 1252: 1247: 1243: 1239: 1236: 1233: 1230: 1227: 1224: 1221: 1218: 1215: 1212: 1209: 1206: 1203: 1181: 1178: 1165: 1145: 1125: 1105: 1085: 1065: 1042: 1022: 1002: 999: 996: 993: 990: 987: 967: 947: 927: 924: 921: 918: 915: 912: 892: 889: 886: 866: 863: 860: 826: 806: 786: 766: 757:has more than 746: 726: 706: 703: 700: 680: 660: 637: 634: 631: 608: 605: 602: 599: 596: 593: 578: 575: 554: 534: 510: 490: 470: 450: 430: 410: 390: 387: 384: 381: 378: 358: 338: 318: 295: 275: 253: 228: 208: 184: 160: 148: 145: 122: 72: 31: 25: 22: 16: 13: 10: 9: 6: 4: 3: 2: 6187: 6176: 6175:Combinatorics 6173: 6171: 6168: 6166: 6163: 6161: 6158: 6157: 6155: 6142: 6137: 6134: 6131: 6125: 6122: 6116: 6111: 6107: 6103: 6099: 6092: 6089: 6085: 6080: 6077: 6073: 6068: 6065: 6054: 6050: 6044: 6041: 6037: 6032: 6029: 6023: 6018: 6014: 6010: 6006: 5999: 5996: 5986: 5980: 5976: 5972: 5968: 5964: 5957: 5954: 5950: 5945: 5942: 5930: 5926: 5920: 5918: 5914: 5910: 5884: 5881: 5874: 5870: 5866: 5865: 5861: 5854: 5853: 5848: 5844: 5840: 5836: 5831: 5827: 5822: 5818: 5814: 5807: 5802: 5799: 5795: 5790: 5785: 5781: 5777: 5773: 5768: 5765: 5759: 5755: 5754: 5749: 5745: 5741: 5737: 5733: 5730: 5726: 5722: 5716: 5712: 5708: 5704: 5699: 5696: 5692: 5688: 5684: 5680: 5676: 5672: 5668: 5667: 5662: 5658: 5654: 5651: 5647: 5643: 5639: 5635: 5631: 5627: 5623: 5619: 5615: 5614: 5613:Combinatorica 5609: 5605: 5601: 5598: 5594: 5590: 5586: 5582: 5578: 5573: 5568: 5565:(7): 112367, 5564: 5560: 5555: 5552: 5548: 5544: 5538: 5534: 5530: 5525: 5520: 5516: 5511: 5510: 5505: 5501: 5498: 5497: 5493: 5491: 5477: 5455: 5451: 5430: 5427: 5422: 5418: 5396: 5393: 5372: 5369: 5366: 5344: 5340: 5332: 5316: 5313: 5309: 5306: 5285: 5265: 5245: 5223: 5219: 5198: 5190: 5189:Fodor's lemma 5171: 5168: 5163: 5159: 5149: 5143: 5137: 5115: 5111: 5107: 5101: 5095: 5092: 5072: 5047: 5043: 5039: 5036: 5033: 5028: 5024: 4978: 4974: 4951: 4947: 4938: 4920: 4916: 4895: 4886: 4884: 4880: 4876: 4872: 4868: 4865: 4861: 4857: 4856:set-theoretic 4854: 4853:combinatorial 4829: 4807: 4803: 4799: 4775: 4733: 4706: 4704: 4702: 4698: 4694: 4676: 4672: 4668: 4649: 4641: 4620: 4614: 4611: 4607: 4598: 4590: 4588: 4571: 4568: 4565: 4559: 4556: 4550: 4547: 4542: 4521: 4518: 4515: 4506: 4487: 4472: 4468: 4442: 4422: 4400: 4396: 4373: 4369: 4341: 4337: 4311: 4289: 4285: 4264: 4242: 4238: 4217: 4208: 4192: 4189: 4183: 4180: 4177: 4171: 4162: 4159: 4153: 4150: 4147: 4141: 4135: 4129: 4126: 4123: 4120: 4117: 4111: 4102: 4099: 4085: 4065: 4062: 4059: 4039: 4019: 3997: 3993: 3965: 3961: 3952: 3944: 3933: 3930: 3927: 3902: 3898: 3890:partition of 3877: 3874: 3871: 3851: 3829: 3825: 3804: 3801: 3798: 3778: 3758: 3755: 3752: 3732: 3729: 3726: 3706: 3686: 3666: 3663: 3660: 3637: 3634: 3631: 3628: 3625: 3619: 3599: 3596: 3593: 3573: 3570: 3567: 3558: 3545: 3539: 3536: 3533: 3527: 3524: 3519: 3511: 3508: 3505: 3493: 3479: 3456: 3453: 3450: 3444: 3432: 3430: 3427: 3410: 3407: 3404: 3401: 3395: 3392: 3389: 3363: 3360: 3354: 3351: 3348: 3342: 3339: 3336: 3308: 3302: 3299: 3296: 3293: 3287: 3281: 3278: 3273: 3269: 3262: 3259: 3256: 3233: 3229: 3225: 3219: 3216: 3213: 3207: 3187: 3184: 3181: 3159: 3155: 3151: 3145: 3142: 3139: 3133: 3113: 3110: 3107: 3087: 3067: 3047: 3044: 3041: 3019: 3015: 3011: 3005: 3002: 2999: 2993: 2973: 2970: 2967: 2959: 2955: 2947: 2945: 2928: 2925: 2922: 2919: 2916: 2910: 2904: 2901: 2898: 2892: 2889: 2883: 2880: 2877: 2871: 2864:sets. Hence, 2851: 2831: 2811: 2788: 2785: 2782: 2779: 2776: 2770: 2764: 2761: 2758: 2752: 2749: 2741: 2713: 2710: 2704: 2701: 2698: 2695: 2692: 2686: 2680: 2677: 2674: 2668: 2665: 2657: 2649: 2643: 2640: 2637: 2634: 2631: 2625: 2619: 2616: 2613: 2607: 2604: 2598: 2595: 2589: 2586: 2583: 2580: 2577: 2571: 2560: 2552: 2542: 2538: 2527: 2524: 2521: 2517: 2513: 2505: 2493: 2492: 2491: 2475: 2471: 2450: 2428: 2424: 2403: 2400: 2397: 2388: 2374: 2371: 2365: 2362: 2359: 2356: 2353: 2347: 2325: 2321: 2300: 2280: 2260: 2240: 2218: 2214: 2193: 2190: 2187: 2165: 2161: 2140: 2118: 2114: 2090: 2084: 2081: 2078: 2074: 2071: 2068: 2065: 2062: 2056: 2047: 2041: 2036: 2032: 2024: 2023: 2022: 2008: 2005: 2002: 1980: 1976: 1952: 1949: 1946: 1940: 1937: 1934: 1931: 1911: 1891: 1869: 1865: 1857:. Since each 1842: 1838: 1834: 1831: 1828: 1823: 1819: 1815: 1810: 1806: 1802: 1799: 1790: 1776: 1773: 1770: 1750: 1730: 1708: 1704: 1683: 1663: 1660: 1657: 1635: 1631: 1627: 1622: 1618: 1597: 1594: 1589: 1585: 1581: 1578: 1575: 1570: 1566: 1562: 1557: 1553: 1532: 1512: 1492: 1472: 1452: 1449: 1446: 1443: 1437: 1434: 1431: 1425: 1416: 1402: 1382: 1360: 1352: 1349: 1346: 1340: 1337: 1317: 1309: 1306:are positive 1293: 1273: 1250: 1245: 1237: 1234: 1231: 1225: 1222: 1219: 1213: 1210: 1207: 1201: 1194: 1193: 1192: 1190: 1186: 1179: 1177: 1163: 1143: 1123: 1103: 1083: 1063: 1054: 1040: 1020: 997: 994: 991: 985: 965: 945: 922: 919: 916: 910: 890: 887: 884: 864: 861: 858: 849: 846: 844: 840: 824: 804: 784: 764: 744: 724: 704: 701: 698: 678: 658: 651: 635: 632: 629: 622: 603: 600: 597: 591: 582: 576: 574: 572: 568: 552: 532: 524: 508: 488: 468: 448: 428: 408: 388: 385: 382: 379: 376: 356: 336: 316: 309: 293: 273: 265: 242: 226: 206: 198: 182: 174: 158: 146: 144: 142: 138: 134: 111: 106: 103: 98: 96: 92: 88: 84: 61: 57: 53: 44: 38: 28: 6170:Intersection 6136: 6124: 6105: 6101: 6091: 6079: 6067: 6056:. Retrieved 6052: 6043: 6031: 6012: 6008: 5998: 5988:, retrieved 5966: 5956: 5951:, p. 3. 5944: 5933:. Retrieved 5928: 5883: 5851: 5847:Tao, Terence 5838: 5834: 5819:(1): 29–38, 5816: 5812: 5782:(2): 11887, 5779: 5775: 5752: 5739: 5736:Jech, Thomas 5702: 5673:(1): 85–90, 5670: 5664: 5617: 5611: 5562: 5558: 5514: 4887: 4851:-lemma is a 4830: 4778: 4776: 4712: 4710: 4699:, to design 4594: 4507: 4209: 4103: 4100: 3559: 3494: 3436: 3428: 2953: 2951: 2824:contains an 2728: 2389: 2105: 1791: 1417: 1266:That is, if 1265: 1188: 1183: 1055: 850: 847: 583: 580: 522: 244: 240: 150: 140: 136: 113: 109: 107: 102:Venn diagram 99: 94: 91:intersection 63: 59: 49: 5657:ErdĹ‘s, Paul 5331:cardinality 4939:subsets of 4860:upper bound 4806:finite sets 4802:uncountable 4324:to produce 4210:Proof. Let 3560:Proof. For 777:sets, then 6165:Set theory 6154:Categories 6072:Rao (2020) 6058:2019-11-10 5990:2022-05-02 5935:2021-12-10 5742:, Springer 5740:Set Theory 5608:Frankl, P. 5572:2009.09327 5524:1908.08483 5506:References 5238:such that 5065:enumerate 2729:Hence, if 369:, we have 173:set system 139:, and the 52:set theory 5895:Δ 5841:: 399–400 5798:202558957 5687:0024-6107 5634:0209-9683 5597:221818818 5551:201314765 5478:β 5452:ω 5428:⊆ 5341:ω 5314:⊆ 5266:β 5220:ω 5172:α 5169:∩ 5164:α 5144:α 5112:ω 5102:α 5096:⁡ 5053:⟩ 5044:ω 5037:α 5029:α 5021:⟨ 5001:Δ 4975:ω 4948:ω 4937:countable 4917:ω 4873:that the 4839:Δ 4828:-system. 4816:Δ 4786:Δ 4774:-system. 4762:Δ 4742:Δ 4720:Δ 4615:⁡ 4557:≤ 4473:∗ 4415:over all 4342:∗ 4290:∗ 4243:∗ 4190:− 4160:− 4136:≥ 4104:Theorem. 4063:− 3998:∗ 3966:∗ 3953:≤ 3931:− 3903:∗ 3875:− 3830:∗ 3802:− 3756:− 3730:− 3664:− 3629:− 3597:− 3586:a set of 3525:≤ 3509:− 3495:Theorem. 3408:⁡ 3355:⁡ 3303:⁡ 3297:⁡ 3282:⁡ 3226:≤ 3174:for some 3152:≤ 3012:≤ 2920:− 2902:− 2890:≤ 2780:− 2762:− 2750:≥ 2711:− 2696:− 2678:− 2666:≤ 2650:− 2635:− 2617:− 2605:≤ 2596:− 2581:− 2553:≤ 2525:∈ 2518:∑ 2514:≤ 2401:∈ 2372:− 2357:− 2191:− 2082:∈ 2069:∈ 2063:∣ 2051:∖ 2006:∈ 1995:for some 1968:. Define 1950:− 1938:≤ 1835:∪ 1832:⋯ 1829:∪ 1816:∪ 1628:∩ 1595:∈ 1579:… 1450:− 1444:≤ 1350:− 1235:− 1220:≤ 851:For each 702:∈ 565:, may be 380:∩ 252:Δ 241:sunflower 199:of a set 151:Suppose 121:Δ 71:Δ 60:sunflower 5849:(2020), 5750:(1980), 5738:(2003), 5661:Rado, R. 5650:14043028 5604:Deza, M. 5494:See also 5397:′ 5310:′ 5298:. Build 1308:integers 621:integers 571:disjoint 308:distinct 5729:2238686 5695:0111692 5642:0637827 5589:4240687 5500:Cap set 5385:are in 5130:, let 5085:. For 4993:-sized 4881: ( 4864:forcing 4695:of the 2804:, then 1013:, then 650:integer 525:of the 264:-system 197:subsets 83:-system 5981:  5796:  5760:  5727:  5717:  5693:  5685:  5648:  5640:  5632:  5595:  5587:  5549:  5539:  5191:, fix 5187:. By 4908:is an 4879:Shanin 4798:-lemma 4732:-lemma 4098:sets. 2021:to be 1415:sets. 133:-lemma 95:kernel 5875:Notes 5809:(PDF) 5794:S2CID 5646:S2CID 5593:S2CID 5567:arXiv 5547:S2CID 5519:arXiv 5410:then 4867:poset 2106:Then 839:ErdĹ‘s 737:, if 567:empty 239:is a 175:over 171:is a 110:large 5979:ISBN 5780:2020 5758:ISBN 5715:ISBN 5683:ISSN 5630:ISSN 5537:ISBN 5370:< 5040:< 4883:1946 4831:The 4777:The 4230:and 3248:for 3185:> 3045:> 2971:> 2952:The 2180:has 1792:Let 1774:< 1286:and 888:> 862:> 843:Rado 841:and 523:some 329:and 243:(or 87:sets 58:, a 54:and 6110:doi 6017:doi 5971:doi 5821:doi 5784:doi 5707:doi 5675:doi 5622:doi 5577:doi 5563:344 5529:doi 5329:of 5278:on 5153:sup 4888:If 4885:). 4612:log 4534:is 4435:in 4304:to 3405:log 3352:log 3300:log 3294:log 3279:log 958:of 349:in 286:of 62:or 6156:: 6106:12 6104:. 6100:. 6051:. 6013:12 6011:. 6007:. 5977:, 5965:, 5927:. 5916:^ 5839:53 5817:60 5815:, 5811:, 5792:, 5778:, 5774:, 5725:MR 5723:, 5713:, 5691:MR 5689:, 5681:, 5671:35 5659:; 5644:, 5638:MR 5636:, 5628:, 5616:, 5606:; 5591:, 5585:MR 5583:, 5575:, 5561:, 5545:, 5535:, 5527:, 5093:cf 4543:10 3985:. 3492:. 3426:. 2986:, 2714:1. 2490:: 2387:. 1789:. 1053:. 877:, 135:, 6143:. 6118:. 6112:: 6086:. 6074:. 6061:. 6038:. 6025:. 6019:: 5973:: 5938:. 5823:: 5786:: 5709:: 5677:: 5624:: 5618:1 5579:: 5569:: 5531:: 5521:: 5456:1 5431:j 5423:i 5419:A 5394:S 5373:j 5367:i 5345:2 5317:S 5307:S 5286:S 5246:f 5224:2 5199:S 5175:) 5160:A 5156:( 5150:= 5147:) 5141:( 5138:f 5116:1 5108:= 5105:) 5099:( 5073:W 5048:2 5034:: 5025:A 4979:2 4952:2 4921:2 4896:W 4677:0 4673:C 4669:A 4650:3 4624:) 4621:n 4618:( 4608:n 4575:) 4572:3 4569:, 4566:k 4563:( 4560:f 4551:2 4548:k 4522:3 4519:= 4516:r 4492:| 4488:F 4484:| 4479:| 4469:F 4464:| 4443:F 4423:A 4401:A 4397:F 4374:A 4370:F 4348:| 4338:F 4333:| 4312:A 4286:F 4265:A 4239:F 4218:F 4196:) 4193:1 4187:) 4184:r 4181:, 4178:b 4175:( 4172:f 4169:( 4166:) 4163:1 4157:) 4154:r 4151:, 4148:a 4145:( 4142:f 4139:( 4133:) 4130:r 4127:, 4124:b 4121:+ 4118:a 4115:( 4112:f 4086:r 4066:1 4060:r 4040:r 4020:r 3994:H 3972:| 3962:H 3957:| 3949:| 3945:H 3941:| 3937:) 3934:1 3928:r 3925:( 3899:H 3878:1 3872:r 3852:H 3826:H 3805:1 3799:r 3779:H 3759:1 3753:r 3733:1 3727:r 3707:H 3687:r 3667:1 3661:k 3641:) 3638:r 3635:, 3632:1 3626:k 3623:( 3620:h 3600:1 3594:r 3574:1 3571:= 3568:k 3546:. 3543:) 3540:r 3537:, 3534:k 3531:( 3528:f 3520:k 3516:) 3512:1 3506:r 3503:( 3480:r 3460:) 3457:r 3454:, 3451:k 3448:( 3445:f 3414:) 3411:k 3402:r 3399:( 3396:O 3393:= 3390:C 3370:) 3367:) 3364:k 3361:r 3358:( 3349:r 3346:( 3343:O 3340:= 3337:C 3327:. 3315:) 3312:) 3309:k 3306:( 3291:) 3288:k 3285:( 3274:3 3270:r 3266:( 3263:O 3260:= 3257:C 3234:k 3230:C 3223:) 3220:r 3217:, 3214:k 3211:( 3208:f 3188:0 3182:C 3160:k 3156:C 3149:) 3146:3 3143:, 3140:k 3137:( 3134:f 3114:3 3111:= 3108:r 3088:r 3068:r 3048:0 3042:C 3020:k 3016:C 3009:) 3006:r 3003:, 3000:k 2997:( 2994:f 2974:2 2968:r 2932:) 2929:r 2926:, 2923:1 2917:k 2914:( 2911:f 2908:) 2905:1 2899:r 2896:( 2893:k 2887:) 2884:r 2881:, 2878:k 2875:( 2872:f 2852:k 2832:r 2812:W 2792:) 2789:r 2786:, 2783:1 2777:k 2774:( 2771:f 2768:) 2765:1 2759:r 2756:( 2753:k 2746:| 2742:W 2738:| 2708:) 2705:r 2702:, 2699:1 2693:k 2690:( 2687:f 2684:) 2681:1 2675:r 2672:( 2669:k 2662:| 2658:A 2654:| 2647:) 2644:r 2641:, 2638:1 2632:k 2629:( 2626:f 2623:) 2620:1 2614:r 2611:( 2608:k 2602:) 2599:1 2593:) 2590:r 2587:, 2584:1 2578:k 2575:( 2572:f 2569:( 2565:| 2561:A 2557:| 2549:| 2543:a 2539:W 2534:| 2528:A 2522:a 2510:| 2506:W 2502:| 2476:a 2472:W 2451:A 2429:i 2425:A 2404:W 2398:S 2375:1 2369:) 2366:r 2363:, 2360:1 2354:k 2351:( 2348:f 2326:a 2322:W 2301:r 2281:W 2261:a 2241:W 2219:a 2215:W 2194:1 2188:k 2166:a 2162:W 2141:W 2119:a 2115:W 2091:. 2088:} 2085:W 2079:S 2075:, 2072:S 2066:a 2060:} 2057:a 2054:{ 2048:S 2045:{ 2042:= 2037:a 2033:W 2009:A 2003:a 1981:a 1977:W 1956:) 1953:1 1947:r 1944:( 1941:k 1935:t 1932:k 1912:A 1892:k 1870:i 1866:A 1843:t 1839:A 1824:2 1820:A 1811:1 1807:A 1803:= 1800:A 1777:r 1771:t 1751:r 1731:W 1709:i 1705:A 1684:W 1664:j 1661:= 1658:i 1636:j 1632:A 1623:i 1619:A 1598:W 1590:t 1586:A 1582:, 1576:, 1571:2 1567:A 1563:, 1558:1 1554:A 1533:r 1513:W 1493:r 1473:W 1453:1 1447:r 1441:) 1438:r 1435:, 1432:1 1429:( 1426:f 1403:r 1383:k 1361:k 1357:) 1353:1 1347:r 1344:( 1341:! 1338:k 1318:W 1294:r 1274:k 1251:. 1246:k 1242:) 1238:1 1232:r 1229:( 1226:! 1223:k 1217:) 1214:r 1211:, 1208:k 1205:( 1202:f 1164:k 1144:k 1124:W 1104:W 1084:W 1064:W 1041:r 1021:F 1001:) 998:r 995:, 992:k 989:( 986:f 966:k 946:F 926:) 923:r 920:, 917:k 914:( 911:f 891:0 885:r 865:0 859:k 825:n 805:r 785:W 765:n 745:W 725:k 705:W 699:S 679:W 659:n 636:r 633:, 630:k 607:) 604:r 601:, 598:k 595:( 592:f 553:S 533:W 509:U 489:W 469:S 449:U 429:W 409:W 389:S 386:= 383:B 377:A 357:W 337:B 317:A 294:U 274:S 227:W 207:U 183:U 159:W 39:. 20::

Index

(more unsolved problems in mathematics)
sunflower (disambiguation)

set theory
extremal combinatorics
sets
intersection
Venn diagram
set system
subsets
distinct
empty
disjoint
integers
integer
Erdős
Rado
Erdős & Rado (1960
integers
Erdős & Rado (1960
theoretical computer science
circuit complexity
parameterized complexity
hitting set problem
fixed-parameter tractable
uncountable
finite sets
combinatorial
set-theoretic
upper bound

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