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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",
4548: 4711: 101: 4703: 2878: 3211:. A 2021 paper by Alweiss, Lovett, Wu, and Zhang gives the best progress towards the conjecture, proving that 2730:{\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.} 4714:
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
66: 6180: 4877: 4765:-system theorem states that a countable collection of k-sets contains a countably infinite sunflower or 5424: 4880:. It may for example be used as one of the ingredients in a proof showing that it is consistent with 3214: 3140: 3000: 4885: 4874: 4610:. For example, in 1986, Razborov used the sunflower lemma to prove that the Clique language required 1624: 5972:
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
5973: 5591: 3483:. It is equal to the statement that the original sunflower lemma is optimal in 5689: 5621:(1981), "Every large set of equidistant (0,+1,–1)-vectors forms a sunflower", 4866: 4816: 183: 62: 5697: 5644: 5543: 577: 6140: 5721: 5526:
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
4649:(superpolynomial) size monotone circuits, a breakthrough result in 859:
Erdos-Rado Delta System Theorem(corollary of the Sunflower lemma):
6059: 5069:{\displaystyle \langle A_{\alpha }:\alpha <\omega _{2}\rangle } 52: 3091:. The conjecture remains wide open even for fixed low values of 2107:{\displaystyle W_{a}=\{S\setminus \{a\}\mid a\in S,\,S\in W\}.} 1621:
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
5528:, Association for Computing Machinery, pp. 624–630, 2474:, and so it corresponds to at least one of the sets in a 5191:{\displaystyle f(\alpha )=\sup(A_{\alpha }\cap \alpha )} 5134:{\displaystyle \operatorname {cf} (\alpha )=\omega _{1}} 452:
share the same common subset of elements. An element in
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sequence of distinct elements is not a sunflower. Let
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to every set. This means that, by our assumption that
5904: 5674:(1960), "Intersection theorems for systems of sets", 5487: 5460: 5427: 5402: 5376: 5349: 5315: 5295: 5275: 5255: 5228: 5208: 5147: 5102: 5082: 5030: 5010: 4983: 4956: 4925: 4905: 4848: 4825: 4795: 4771: 4751: 4729: 4678: 4659: 4616: 4551: 4525: 4472: 4452: 4432: 4405: 4378: 4341: 4321: 4294: 4274: 4247: 4227: 4121: 4095: 4069: 4049: 4029: 4002: 3934: 3907: 3881: 3861: 3834: 3808: 3788: 3762: 3736: 3716: 3696: 3670: 3629: 3603: 3577: 3512: 3489: 3454: 3399: 3346: 3266: 3217: 3191: 3143: 3117: 3097: 3077: 3051: 3003: 2977: 2881: 2861: 2841: 2821: 2746: 2510: 2480: 2460: 2433: 2407: 2357: 2330: 2310: 2290: 2270: 2250: 2223: 2197: 2170: 2150: 2123: 2041: 2012: 1985: 1941: 1921: 1901: 1874: 1809: 1780: 1760: 1740: 1713: 1693: 1667: 1627: 1562: 1542: 1522: 1502: 1482: 1435: 1412: 1392: 1347: 1327: 1303: 1283: 1211: 1173: 1153: 1133: 1113: 1093: 1073: 1050: 1030: 995: 975: 955: 920: 894: 868: 834: 814: 794: 774: 754: 734: 708: 688: 668: 639: 601: 562: 556:
subset, but not others. Note that this intersection,
542: 518: 498: 478: 458: 438: 418: 412:. In other words, a set system or collection of sets 386: 366: 346: 326: 303: 283: 261: 236: 216: 192: 168: 130: 80: 6094: 6046: 5959: 856:, the Delta System Theorem, indicates that it does. 3756:elements and add one element to each set in one of 3448:ErdĹ‘s and Rado proved the following lower bound on 5910: 5764:Set Theory: An Introduction to Independence Proofs 5493: 5473: 5454:. Using the continuum hypothesis, there are only 5446: 5413: 5388: 5362: 5332: 5301: 5281: 5261: 5241: 5214: 5190: 5133: 5088: 5068: 5016: 4996: 4969: 4938: 4911: 4854: 4831: 4801: 4777: 4757: 4745:which is essentially equivalent to the ErdĹ‘s-Rado 4735: 4694: 4665: 4641: 4590: 4537: 4508: 4458: 4438: 4418: 4391: 4364: 4327: 4307: 4280: 4260: 4233: 4211: 4101: 4081: 4055: 4035: 4015: 3988: 3920: 3893: 3867: 3847: 3820: 3794: 3774: 3748: 3722: 3702: 3682: 3656: 3615: 3589: 3561: 3495: 3475: 3429: 3385: 3330: 3251: 3203: 3177: 3129: 3103: 3083: 3063: 3037: 2989: 2967:is one of several variations of the conjecture of 2947: 2867: 2847: 2827: 2807: 2729: 2493: 2466: 2446: 2419: 2390: 2343: 2316: 2296: 2276: 2256: 2236: 2209: 2183: 2156: 2136: 2106: 2024: 1998: 1971: 1927: 1907: 1887: 1860: 1792: 1766: 1746: 1726: 1699: 1679: 1653: 1613: 1548: 1528: 1508: 1488: 1468: 1418: 1398: 1378: 1333: 1309: 1289: 1266: 1179: 1159: 1139: 1119: 1099: 1079: 1056: 1036: 1016: 981: 961: 941: 906: 880: 840: 820: 800: 780: 760: 740: 720: 694: 674: 659:, which is defined to be the smallest nonnegative 651: 622: 568: 548: 524: 504: 484: 464: 444: 424: 404: 372: 352: 332: 309: 289: 267: 242: 222: 198: 174: 136: 86: 5936:"Extremal Combinatorics III: Some Basic Theorems" 4606:The sunflower lemma has numerous applications in 4212:{\displaystyle f(a+b,r)\geq (f(a,r)-1)(f(b,r)-1)} 5163: 595:Specifically, researchers analyze the function 1614:{\displaystyle A_{1},A_{2},\ldots ,A_{t}\in W} 6107:Abbott, H.L; Hanson, D; Sauer, N (May 1972). 6014:Abbott, H.L; Hanson, D; Sauer, N (May 1972). 5980:, Boston, MA: Springer US, pp. 143–150, 4268:be two sunflower free families. For each set 3331:{\displaystyle C=O(r^{3}\log(k)\log \log(k))} 8: 5063: 5031: 4591:{\displaystyle 10^{\frac {k}{2}}\leq f(k,3)} 4112:A stronger result is the following theorem: 2098: 2070: 2064: 2055: 828:sets. Though it is not obvious that such an 6109:"Intersection theorems for systems of sets" 6016:"Intersection theorems for systems of sets" 5919: 5677:Journal of the London Mathematical Society 4702:circuits. It has also been applied in the 2217:elements. Furthermore, every sunflower of 6151: 6124: 6113:Journal of Combinatorial Theory, Series A 6031: 6020:Journal of Combinatorial Theory, Series A 5903: 5835: 5798: 5581: 5533: 5486: 5465: 5459: 5432: 5426: 5401: 5375: 5354: 5348: 5314: 5294: 5274: 5254: 5233: 5227: 5207: 5173: 5146: 5125: 5101: 5081: 5057: 5038: 5029: 5009: 4988: 4982: 4961: 4955: 4930: 4924: 4904: 4847: 4824: 4794: 4770: 4750: 4728: 4718:Analogue for infinite collections of sets 4686: 4677: 4658: 4621: 4615: 4556: 4550: 4524: 4501: 4493: 4488: 4482: 4473: 4471: 4451: 4431: 4410: 4404: 4383: 4377: 4357: 4351: 4342: 4340: 4320: 4299: 4293: 4273: 4252: 4246: 4226: 4120: 4094: 4068: 4048: 4028: 4023:is sunflower free since any selection of 4007: 4001: 3981: 3975: 3966: 3958: 3950: 3933: 3912: 3906: 3880: 3860: 3839: 3833: 3807: 3787: 3761: 3735: 3730:be such a set. Take an additional set of 3715: 3695: 3669: 3628: 3602: 3576: 3529: 3511: 3488: 3453: 3398: 3345: 3283: 3265: 3243: 3216: 3190: 3169: 3142: 3116: 3096: 3076: 3050: 3029: 3002: 2976: 2968: 2948:{\displaystyle f(k,r)\leq k(r-1)f(k-1,r)} 2880: 2860: 2840: 2820: 2755: 2747: 2745: 2671: 2663: 2574: 2566: 2558: 2552: 2543: 2531: 2519: 2511: 2509: 2485: 2479: 2459: 2438: 2432: 2406: 2356: 2335: 2329: 2309: 2289: 2269: 2249: 2228: 2222: 2196: 2175: 2169: 2149: 2128: 2122: 2088: 2046: 2040: 2011: 1990: 1984: 1940: 1920: 1900: 1879: 1873: 1852: 1833: 1820: 1808: 1779: 1759: 1739: 1718: 1712: 1692: 1666: 1645: 1632: 1626: 1599: 1580: 1567: 1561: 1541: 1521: 1501: 1481: 1434: 1411: 1391: 1370: 1346: 1326: 1302: 1282: 1255: 1210: 1195: 1172: 1152: 1132: 1112: 1092: 1072: 1049: 1029: 994: 974: 954: 919: 893: 867: 848:must exist, a basic and simple result of 833: 813: 793: 773: 753: 733: 707: 687: 667: 638: 600: 561: 541: 517: 497: 477: 457: 437: 417: 385: 365: 345: 325: 302: 282: 260: 235: 215: 191: 167: 129: 104:. This common intersection is called the 79: 6060:"Quanta Magazine - Illuminating Science" 5898:The original term for this concept was " 1341:of cardinality greater than or equal to 6141:https://mathoverflow.net/a/420288/12176 6139:Lower Bounds for the Sunflower Problem 5930: 5928: 5891: 5863:The sunflower lemma via Shannon entropy 2061: 1267:{\displaystyle f(k,r)\leq k!(r-1)^{k}.} 38:(more unsolved problems in mathematics) 4893: 4372:many sets. Denote this family of sets 3664:denote the size of the largest set of 2808:{\displaystyle |W|\geq k(r-1)f(k-1,r)} 492:or else appears in at most one of the 3562:{\displaystyle (r-1)^{k}\leq f(k,r).} 989:-sets is of cardinality greater than 472:is either found in the common subset 7: 6095:Bell, Chueluecha & Warnke (2021) 4888:does not hold. It was introduced by 3989:{\displaystyle (r-1)|H|\leq |H^{*}|} 6082: 5978:Numbers, Information and Complexity 4602:Applications of the sunflower lemma 1406:contains a sunflower with at least 5922:, has been gradually replacing it. 5905: 5011: 4849: 4826: 4796: 4772: 4752: 4730: 3393:; the current best-known bound is 262: 131: 81: 25: 4869:tool used in proofs to impose an 5974:"Extremal Problems on Δ-Systems" 5447:{\displaystyle A_{i}\subseteq j} 3252:{\displaystyle f(k,r)\leq C^{k}} 3178:{\displaystyle f(k,3)\leq C^{k}} 3038:{\displaystyle f(k,r)\leq C^{k}} 5846:C. R. (Doklady) Acad. Sci. URSS 5714:Parameterized Complexity Theory 2959:ErdĹ‘s-Rado sunflower conjecture 2164:, except that every element of 1654:{\displaystyle A_{i}\cap A_{j}} 152:ErdĹ‘s-Rado sunflower conjecture 29:Unsolved problem in mathematics 5817:"Sunflowers: from soil to oil" 5185: 5166: 5157: 5151: 5115: 5109: 4634: 4628: 4585: 4573: 4516:sets which is sunflower free. 4502: 4494: 4489: 4474: 4358: 4343: 4206: 4197: 4185: 4179: 4176: 4167: 4155: 4149: 4143: 4125: 3982: 3967: 3959: 3951: 3947: 3935: 3875:with an element added form an 3651: 3633: 3553: 3541: 3526: 3513: 3470: 3458: 3424: 3409: 3386:{\displaystyle C=O(r\log(rk))} 3380: 3377: 3368: 3356: 3325: 3322: 3316: 3301: 3295: 3276: 3233: 3221: 3159: 3147: 3019: 3007: 2942: 2924: 2918: 2906: 2897: 2885: 2802: 2784: 2778: 2766: 2756: 2748: 2718: 2700: 2694: 2682: 2672: 2664: 2657: 2639: 2633: 2621: 2612: 2603: 2585: 2579: 2575: 2567: 2559: 2544: 2520: 2512: 2379: 2361: 2244:corresponds to a sunflower of 1966: 1954: 1469:{\displaystyle f(1,r)\leq r-1} 1451: 1439: 1367: 1354: 1252: 1239: 1227: 1215: 1011: 999: 936: 924: 682:such that, for any set system 617: 605: 588:Sunflower lemma and conjecture 432:is a sunflower if all sets in 61:In the mathematical fields of 1: 5333:{\displaystyle S'\subseteq S} 1972:{\displaystyle kt\leq k(r-1)} 1044:contains a sunflower of size 6126:10.1016/0097-3165(72)90103-3 6033:10.1016/0097-3165(72)90103-3 5986:10.1007/978-1-4757-6048-4_14 5866:, What's new (personal blog) 4608:theoretical computer science 4466:. This produces a family of 3430:{\displaystyle C=O(r\log k)} 5481:-many countable subsets of 5474:{\displaystyle \omega _{1}} 5363:{\displaystyle \omega _{2}} 5242:{\displaystyle \omega _{2}} 4997:{\displaystyle \omega _{2}} 4970:{\displaystyle \omega _{2}} 4939:{\displaystyle \omega _{2}} 4882:Zermelo–Fraenkel set theory 4642:{\displaystyle n^{\log(n)}} 2427:intersects with one of the 1734:). Because we assumed that 1379:{\displaystyle k!(r-1)^{k}} 580:; a collection of pairwise 206:, that is, a collection of 6202: 5592:10.1016/j.disc.2021.112367 4509:{\displaystyle |F^{*}||F|} 4288:in F, append every set in 3137:; it is not known whether 2391:{\displaystyle f(k-1,r)-1} 949:such that if a set system 48:sunflower (disambiguation) 45: 4712:fixed-parameter tractable 2955:and the theorem follows. 2304:has no sunflower of size 1754:had no sunflower of size 405:{\displaystyle A\cap B=S} 5920:Deza & Frankl (1981) 5781:Rao, Anup (2020-02-25), 4819:contains an uncountable 4704:parameterized complexity 3802:. Take the union of the 3657:{\displaystyle h(k-1,r)} 2971:, p. 86) that for each 2264:, simply by adding back 1661:is the empty set unless 808:contains a sunflower of 728:has cardinality at most 512:elements. No element of 6152:Flum & Grohe (2006) 5911:{\displaystyle \Delta } 5783:"Coding for Sunflowers" 5690:10.1112/jlms/s1-35.1.85 5544:10.1145/3357713.3384234 5269:is constantly equal to 5017:{\displaystyle \Delta } 4855:{\displaystyle \Delta } 4832:{\displaystyle \Delta } 4802:{\displaystyle \Delta } 4778:{\displaystyle \Delta } 4758:{\displaystyle \Delta } 4736:{\displaystyle \Delta } 4365:{\displaystyle |F^{*}|} 2454:'s, it intersects with 1476:, since the set system 1386:of sets of cardinality 1187:-uniform" set systems. 1127:such that every set in 277:) if there is a subset 268:{\displaystyle \Delta } 137:{\displaystyle \Delta } 87:{\displaystyle \Delta } 5940:Combinatorics and more 5912: 5824:Bull. Amer. Math. Soc. 5495: 5494:{\displaystyle \beta } 5475: 5448: 5415: 5390: 5389:{\displaystyle i<j} 5364: 5334: 5303: 5283: 5282:{\displaystyle \beta } 5263: 5243: 5216: 5192: 5135: 5090: 5070: 5018: 4998: 4971: 4940: 4913: 4856: 4833: 4803: 4779: 4759: 4737: 4696: 4695:{\displaystyle AC_{0}} 4667: 4643: 4592: 4539: 4510: 4460: 4440: 4420: 4393: 4366: 4329: 4309: 4282: 4262: 4235: 4213: 4103: 4083: 4057: 4037: 4017: 3990: 3922: 3895: 3869: 3849: 3822: 3796: 3776: 3750: 3724: 3704: 3684: 3658: 3617: 3591: 3563: 3497: 3477: 3476:{\displaystyle f(k,r)} 3444:Sunflower lower bounds 3431: 3387: 3332: 3253: 3205: 3204:{\displaystyle C>0} 3179: 3131: 3105: 3085: 3065: 3064:{\displaystyle C>0} 3039: 2991: 2990:{\displaystyle r>2} 2969:ErdĹ‘s & Rado (1960 2949: 2869: 2855:set sunflower of size 2849: 2829: 2809: 2731: 2495: 2468: 2448: 2421: 2420:{\displaystyle S\in W} 2392: 2345: 2318: 2298: 2278: 2258: 2238: 2211: 2185: 2158: 2144:is a set system, like 2138: 2108: 2026: 2025:{\displaystyle a\in A} 2000: 1973: 1929: 1909: 1889: 1862: 1794: 1793:{\displaystyle t<r} 1768: 1748: 1728: 1701: 1681: 1655: 1615: 1550: 1536:has no sunflower with 1530: 1510: 1490: 1470: 1420: 1400: 1380: 1335: 1311: 1291: 1268: 1196:ErdĹ‘s & Rado (1960 1181: 1161: 1141: 1121: 1101: 1081: 1058: 1038: 1018: 1017:{\displaystyle f(k,r)} 983: 963: 943: 942:{\displaystyle f(k,r)} 914:, there is an integer 908: 907:{\displaystyle r>0} 882: 881:{\displaystyle k>0} 842: 822: 802: 782: 762: 742: 722: 721:{\displaystyle S\in W} 696: 676: 653: 624: 623:{\displaystyle f(k,r)} 570: 550: 526: 506: 486: 466: 446: 426: 406: 374: 354: 334: 311: 291: 269: 244: 224: 200: 176: 138: 88: 67:extremal combinatorics 58: 6171:Forcing (mathematics) 6047:Alweiss et al. (2020) 5960:Alweiss et al. (2020) 5913: 5722:10.1007/3-540-29953-X 5496: 5476: 5449: 5416: 5391: 5365: 5335: 5304: 5284: 5264: 5244: 5217: 5193: 5136: 5091: 5071: 5019: 4999: 4972: 4946:-sized collection of 4941: 4914: 4857: 4834: 4804: 4780: 4760: 4738: 4697: 4668: 4644: 4593: 4540: 4511: 4461: 4441: 4421: 4419:{\displaystyle F_{A}} 4394: 4392:{\displaystyle F_{A}} 4367: 4330: 4310: 4308:{\displaystyle F^{*}} 4283: 4263: 4261:{\displaystyle F^{*}} 4236: 4214: 4104: 4084: 4058: 4038: 4018: 4016:{\displaystyle H^{*}} 3991: 3923: 3921:{\displaystyle H^{*}} 3896: 3870: 3850: 3848:{\displaystyle H^{*}} 3823: 3797: 3777: 3751: 3725: 3705: 3685: 3659: 3618: 3592: 3564: 3498: 3478: 3432: 3388: 3333: 3254: 3206: 3180: 3132: 3106: 3086: 3066: 3040: 2992: 2950: 2870: 2850: 2830: 2810: 2732: 2496: 2494:{\displaystyle W_{a}} 2469: 2449: 2447:{\displaystyle A_{i}} 2422: 2393: 2346: 2344:{\displaystyle W_{a}} 2319: 2299: 2279: 2259: 2239: 2237:{\displaystyle W_{a}} 2212: 2186: 2184:{\displaystyle W_{a}} 2159: 2139: 2137:{\displaystyle W_{a}} 2109: 2027: 2001: 1999:{\displaystyle W_{a}} 1974: 1930: 1915:, the cardinality of 1910: 1890: 1888:{\displaystyle A_{i}} 1863: 1795: 1769: 1749: 1729: 1727:{\displaystyle A_{i}} 1707:intersects with some 1702: 1682: 1656: 1616: 1551: 1531: 1511: 1491: 1471: 1421: 1401: 1381: 1336: 1312: 1292: 1269: 1182: 1162: 1142: 1122: 1102: 1082: 1059: 1039: 1019: 984: 964: 944: 909: 883: 843: 823: 803: 783: 763: 743: 723: 697: 677: 654: 625: 571: 551: 527: 507: 487: 467: 447: 427: 407: 375: 355: 335: 312: 292: 270: 245: 225: 201: 177: 139: 89: 56: 5902: 5570:Discrete Mathematics 5485: 5458: 5425: 5400: 5374: 5347: 5313: 5293: 5273: 5253: 5226: 5206: 5145: 5100: 5080: 5028: 5008: 4981: 4954: 4923: 4903: 4886:continuum hypothesis 4846: 4823: 4793: 4769: 4749: 4727: 4676: 4657: 4614: 4549: 4523: 4470: 4450: 4430: 4403: 4399:. Take the union of 4376: 4339: 4319: 4292: 4272: 4245: 4225: 4119: 4093: 4067: 4047: 4027: 4000: 3932: 3905: 3879: 3859: 3832: 3806: 3786: 3760: 3734: 3714: 3694: 3668: 3627: 3601: 3575: 3510: 3487: 3452: 3397: 3344: 3264: 3215: 3189: 3141: 3115: 3095: 3075: 3049: 3001: 2975: 2965:sunflower conjecture 2879: 2859: 2839: 2819: 2744: 2508: 2478: 2458: 2431: 2405: 2355: 2328: 2308: 2288: 2268: 2248: 2221: 2195: 2168: 2148: 2121: 2039: 2010: 1983: 1939: 1919: 1899: 1872: 1807: 1778: 1758: 1738: 1711: 1691: 1665: 1625: 1560: 1556:sets. Then consider 1540: 1520: 1500: 1480: 1433: 1410: 1390: 1345: 1325: 1321:, then a set system 1301: 1281: 1209: 1202:, which states that 1198:, p. 86) proved the 1171: 1151: 1131: 1111: 1091: 1071: 1048: 1028: 993: 973: 953: 918: 892: 866: 832: 812: 792: 772: 752: 732: 706: 702:such that every set 686: 666: 637: 599: 560: 540: 516: 496: 476: 456: 436: 416: 384: 364: 344: 324: 301: 281: 259: 234: 214: 190: 166: 128: 78: 46:For other uses, see 5942:. 28 September 2008 5370:such that whenever 4708:hitting set problem 4538:{\displaystyle r=3} 4082:{\displaystyle r-1} 3894:{\displaystyle r-1} 3821:{\displaystyle r-1} 3782:disjoint copies of 3775:{\displaystyle r-1} 3749:{\displaystyle r-1} 3683:{\displaystyle k-1} 3616:{\displaystyle r-1} 3590:{\displaystyle k=1} 3130:{\displaystyle r=3} 2351:must be bounded by 2210:{\displaystyle k-1} 1687:, and every set in 1680:{\displaystyle i=j} 1067:In the literature, 652:{\displaystyle k,r} 317:such that for each 96:is a collection of 5908: 5815:Rao, Anup (2023), 5637:10.1007/BF02579328 5491: 5471: 5444: 5414:{\displaystyle S'} 5411: 5386: 5360: 5330: 5299: 5279: 5259: 5239: 5212: 5188: 5131: 5086: 5066: 5014: 4994: 4967: 4936: 4909: 4852: 4829: 4811:states that every 4799: 4775: 4755: 4733: 4692: 4663: 4651:circuit complexity 4639: 4588: 4535: 4506: 4456: 4436: 4416: 4389: 4362: 4325: 4305: 4278: 4258: 4231: 4209: 4099: 4079: 4053: 4033: 4013: 3986: 3918: 3891: 3865: 3845: 3818: 3792: 3772: 3746: 3720: 3700: 3680: 3654: 3613: 3587: 3559: 3493: 3473: 3427: 3383: 3328: 3249: 3201: 3175: 3127: 3101: 3081: 3071:depending only on 3061: 3045:for some constant 3035: 2987: 2945: 2865: 2845: 2825: 2805: 2727: 2542: 2491: 2464: 2444: 2417: 2388: 2341: 2314: 2294: 2274: 2254: 2234: 2207: 2181: 2154: 2134: 2104: 2022: 1996: 1969: 1925: 1905: 1885: 1858: 1790: 1764: 1744: 1724: 1697: 1677: 1651: 1611: 1546: 1526: 1506: 1486: 1466: 1416: 1396: 1376: 1331: 1307: 1287: 1264: 1177: 1157: 1137: 1117: 1097: 1077: 1054: 1034: 1014: 979: 959: 939: 904: 878: 838: 818: 798: 778: 758: 738: 718: 692: 672: 649: 620: 566: 546: 532:is shared by just 522: 502: 482: 462: 442: 422: 402: 370: 350: 330: 307: 287: 265: 240: 220: 196: 172: 134: 108:of the sunflower. 84: 59: 18:Delta-system lemma 5995:978-1-4757-6048-4 5837:10.1090/bull/1777 5800:10.19086/da.11887 5787:Discrete Analysis 5774:978-0-444-85401-8 5767:, North-Holland, 5731:978-3-540-29952-3 5680:, Second Series, 5553:978-1-4503-6979-4 5302:{\displaystyle S} 5262:{\displaystyle f} 5215:{\displaystyle S} 5089:{\displaystyle W} 4912:{\displaystyle W} 4722:A version of the 4666:{\displaystyle 3} 4564: 4459:{\displaystyle F} 4439:{\displaystyle A} 4328:{\displaystyle A} 4281:{\displaystyle A} 4234:{\displaystyle F} 4102:{\displaystyle r} 4056:{\displaystyle r} 4036:{\displaystyle r} 3868:{\displaystyle H} 3795:{\displaystyle H} 3723:{\displaystyle H} 3703:{\displaystyle r} 3496:{\displaystyle r} 3104:{\displaystyle r} 3084:{\displaystyle r} 2868:{\displaystyle k} 2848:{\displaystyle r} 2828:{\displaystyle W} 2527: 2467:{\displaystyle A} 2317:{\displaystyle r} 2297:{\displaystyle W} 2277:{\displaystyle a} 2257:{\displaystyle W} 2157:{\displaystyle W} 1928:{\displaystyle A} 1908:{\displaystyle k} 1767:{\displaystyle r} 1747:{\displaystyle W} 1700:{\displaystyle W} 1549:{\displaystyle r} 1529:{\displaystyle W} 1509:{\displaystyle r} 1489:{\displaystyle W} 1419:{\displaystyle r} 1399:{\displaystyle k} 1334:{\displaystyle W} 1310:{\displaystyle r} 1290:{\displaystyle k} 1180:{\displaystyle k} 1160:{\displaystyle k} 1140:{\displaystyle W} 1120:{\displaystyle W} 1100:{\displaystyle W} 1080:{\displaystyle W} 1057:{\displaystyle r} 1037:{\displaystyle F} 982:{\displaystyle k} 962:{\displaystyle F} 841:{\displaystyle n} 821:{\displaystyle r} 801:{\displaystyle W} 781:{\displaystyle n} 761:{\displaystyle W} 741:{\displaystyle k} 695:{\displaystyle W} 675:{\displaystyle n} 569:{\displaystyle S} 549:{\displaystyle W} 525:{\displaystyle U} 505:{\displaystyle W} 485:{\displaystyle S} 465:{\displaystyle U} 445:{\displaystyle W} 425:{\displaystyle W} 373:{\displaystyle W} 353:{\displaystyle B} 333:{\displaystyle A} 310:{\displaystyle U} 290:{\displaystyle S} 243:{\displaystyle W} 230:. The collection 223:{\displaystyle U} 199:{\displaystyle U} 175:{\displaystyle W} 158:Formal definition 16:(Redirected from 6193: 6155: 6149: 6143: 6137: 6131: 6130: 6128: 6104: 6098: 6092: 6086: 6080: 6074: 6073: 6071: 6070: 6056: 6050: 6044: 6038: 6037: 6035: 6011: 6005: 6004: 6003: 6002: 5969: 5963: 5957: 5951: 5950: 5948: 5947: 5932: 5923: 5917: 5915: 5914: 5909: 5896: 5878:Thiemann, RenĂ©. 5867: 5853: 5840: 5839: 5821: 5811: 5802: 5777: 5754: 5742: 5708: 5663: 5610: 5585: 5564: 5537: 5500: 5498: 5497: 5492: 5480: 5478: 5477: 5472: 5470: 5469: 5453: 5451: 5450: 5445: 5437: 5436: 5420: 5418: 5417: 5412: 5410: 5395: 5393: 5392: 5387: 5369: 5367: 5366: 5361: 5359: 5358: 5339: 5337: 5336: 5331: 5323: 5308: 5306: 5305: 5300: 5288: 5286: 5285: 5280: 5268: 5266: 5265: 5260: 5248: 5246: 5245: 5240: 5238: 5237: 5221: 5219: 5218: 5213: 5197: 5195: 5194: 5189: 5178: 5177: 5140: 5138: 5137: 5132: 5130: 5129: 5095: 5093: 5092: 5087: 5075: 5073: 5072: 5067: 5062: 5061: 5043: 5042: 5024:-subsystem. Let 5023: 5021: 5020: 5015: 5003: 5001: 5000: 4995: 4993: 4992: 4976: 4974: 4973: 4968: 4966: 4965: 4945: 4943: 4942: 4937: 4935: 4934: 4918: 4916: 4915: 4910: 4861: 4859: 4858: 4853: 4838: 4836: 4835: 4830: 4808: 4806: 4805: 4800: 4784: 4782: 4781: 4776: 4764: 4762: 4761: 4756: 4742: 4740: 4739: 4734: 4701: 4699: 4698: 4693: 4691: 4690: 4672: 4670: 4669: 4664: 4648: 4646: 4645: 4640: 4638: 4637: 4597: 4595: 4594: 4589: 4566: 4565: 4557: 4544: 4542: 4541: 4536: 4515: 4513: 4512: 4507: 4505: 4497: 4492: 4487: 4486: 4477: 4465: 4463: 4462: 4457: 4445: 4443: 4442: 4437: 4425: 4423: 4422: 4417: 4415: 4414: 4398: 4396: 4395: 4390: 4388: 4387: 4371: 4369: 4368: 4363: 4361: 4356: 4355: 4346: 4334: 4332: 4331: 4326: 4314: 4312: 4311: 4306: 4304: 4303: 4287: 4285: 4284: 4279: 4267: 4265: 4264: 4259: 4257: 4256: 4240: 4238: 4237: 4232: 4218: 4216: 4215: 4210: 4108: 4106: 4105: 4100: 4088: 4086: 4085: 4080: 4062: 4060: 4059: 4054: 4042: 4040: 4039: 4034: 4022: 4020: 4019: 4014: 4012: 4011: 3995: 3993: 3992: 3987: 3985: 3980: 3979: 3970: 3962: 3954: 3927: 3925: 3924: 3919: 3917: 3916: 3900: 3898: 3897: 3892: 3874: 3872: 3871: 3866: 3855:. The copies of 3854: 3852: 3851: 3846: 3844: 3843: 3827: 3825: 3824: 3819: 3801: 3799: 3798: 3793: 3781: 3779: 3778: 3773: 3755: 3753: 3752: 3747: 3729: 3727: 3726: 3721: 3709: 3707: 3706: 3701: 3689: 3687: 3686: 3681: 3663: 3661: 3660: 3655: 3622: 3620: 3619: 3614: 3596: 3594: 3593: 3588: 3568: 3566: 3565: 3560: 3534: 3533: 3502: 3500: 3499: 3494: 3482: 3480: 3479: 3474: 3436: 3434: 3433: 3428: 3392: 3390: 3389: 3384: 3339: 3337: 3335: 3334: 3329: 3288: 3287: 3258: 3256: 3255: 3250: 3248: 3247: 3210: 3208: 3207: 3202: 3184: 3182: 3181: 3176: 3174: 3173: 3136: 3134: 3133: 3128: 3110: 3108: 3107: 3102: 3090: 3088: 3087: 3082: 3070: 3068: 3067: 3062: 3044: 3042: 3041: 3036: 3034: 3033: 2996: 2994: 2993: 2988: 2954: 2952: 2951: 2946: 2874: 2872: 2871: 2866: 2854: 2852: 2851: 2846: 2834: 2832: 2831: 2826: 2814: 2812: 2811: 2806: 2759: 2751: 2736: 2734: 2733: 2728: 2675: 2667: 2578: 2570: 2562: 2557: 2556: 2547: 2541: 2523: 2515: 2500: 2498: 2497: 2492: 2490: 2489: 2473: 2471: 2470: 2465: 2453: 2451: 2450: 2445: 2443: 2442: 2426: 2424: 2423: 2418: 2401:Since every set 2397: 2395: 2394: 2389: 2350: 2348: 2347: 2342: 2340: 2339: 2323: 2321: 2320: 2315: 2303: 2301: 2300: 2295: 2283: 2281: 2280: 2275: 2263: 2261: 2260: 2255: 2243: 2241: 2240: 2235: 2233: 2232: 2216: 2214: 2213: 2208: 2190: 2188: 2187: 2182: 2180: 2179: 2163: 2161: 2160: 2155: 2143: 2141: 2140: 2135: 2133: 2132: 2113: 2111: 2110: 2105: 2051: 2050: 2031: 2029: 2028: 2023: 2005: 2003: 2002: 1997: 1995: 1994: 1978: 1976: 1975: 1970: 1934: 1932: 1931: 1926: 1914: 1912: 1911: 1906: 1895:has cardinality 1894: 1892: 1891: 1886: 1884: 1883: 1867: 1865: 1864: 1859: 1857: 1856: 1838: 1837: 1825: 1824: 1799: 1797: 1796: 1791: 1773: 1771: 1770: 1765: 1753: 1751: 1750: 1745: 1733: 1731: 1730: 1725: 1723: 1722: 1706: 1704: 1703: 1698: 1686: 1684: 1683: 1678: 1660: 1658: 1657: 1652: 1650: 1649: 1637: 1636: 1620: 1618: 1617: 1612: 1604: 1603: 1585: 1584: 1572: 1571: 1555: 1553: 1552: 1547: 1535: 1533: 1532: 1527: 1515: 1513: 1512: 1507: 1495: 1493: 1492: 1487: 1475: 1473: 1472: 1467: 1425: 1423: 1422: 1417: 1405: 1403: 1402: 1397: 1385: 1383: 1382: 1377: 1375: 1374: 1340: 1338: 1337: 1332: 1316: 1314: 1313: 1308: 1296: 1294: 1293: 1288: 1273: 1271: 1270: 1265: 1260: 1259: 1186: 1184: 1183: 1178: 1166: 1164: 1163: 1158: 1147:has cardinality 1146: 1144: 1143: 1138: 1126: 1124: 1123: 1118: 1106: 1104: 1103: 1098: 1086: 1084: 1083: 1078: 1063: 1061: 1060: 1055: 1043: 1041: 1040: 1035: 1023: 1021: 1020: 1015: 988: 986: 985: 980: 968: 966: 965: 960: 948: 946: 945: 940: 913: 911: 910: 905: 887: 885: 884: 879: 847: 845: 844: 839: 827: 825: 824: 819: 807: 805: 804: 799: 787: 785: 784: 779: 767: 765: 764: 759: 747: 745: 744: 739: 727: 725: 724: 719: 701: 699: 698: 693: 681: 679: 678: 673: 658: 656: 655: 650: 630:for nonnegative 629: 627: 626: 621: 575: 573: 572: 567: 555: 553: 552: 547: 531: 529: 528: 523: 511: 509: 508: 503: 491: 489: 488: 483: 471: 469: 468: 463: 451: 449: 448: 443: 431: 429: 428: 423: 411: 409: 408: 403: 379: 377: 376: 371: 359: 357: 356: 351: 339: 337: 336: 331: 316: 314: 313: 308: 296: 294: 293: 288: 274: 272: 271: 266: 249: 247: 246: 241: 229: 227: 226: 221: 205: 203: 202: 197: 181: 179: 178: 173: 143: 141: 140: 135: 93: 91: 90: 85: 30: 21: 6201: 6200: 6196: 6195: 6194: 6192: 6191: 6190: 6161: 6160: 6159: 6158: 6150: 6146: 6138: 6134: 6106: 6105: 6101: 6093: 6089: 6081: 6077: 6068: 6066: 6064:Quanta Magazine 6058: 6057: 6053: 6045: 6041: 6013: 6012: 6008: 6000: 5998: 5996: 5971: 5970: 5966: 5958: 5954: 5945: 5943: 5934: 5933: 5926: 5900: 5899: 5897: 5893: 5888: 5875: 5870: 5856: 5843: 5819: 5814: 5780: 5775: 5757: 5745: 5732: 5711: 5666: 5613: 5567: 5554: 5523: 5519: 5507: 5483: 5482: 5461: 5456: 5455: 5428: 5423: 5422: 5403: 5398: 5397: 5372: 5371: 5350: 5345: 5344: 5316: 5311: 5310: 5291: 5290: 5271: 5270: 5251: 5250: 5229: 5224: 5223: 5204: 5203: 5169: 5143: 5142: 5121: 5098: 5097: 5078: 5077: 5053: 5034: 5026: 5025: 5006: 5005: 4984: 4979: 4978: 4957: 4952: 4951: 4926: 4921: 4920: 4901: 4900: 4844: 4843: 4821: 4820: 4791: 4790: 4767: 4766: 4747: 4746: 4725: 4724: 4720: 4682: 4674: 4673: 4655: 4654: 4617: 4612: 4611: 4604: 4552: 4547: 4546: 4521: 4520: 4478: 4468: 4467: 4448: 4447: 4428: 4427: 4406: 4401: 4400: 4379: 4374: 4373: 4347: 4337: 4336: 4317: 4316: 4295: 4290: 4289: 4270: 4269: 4248: 4243: 4242: 4223: 4222: 4117: 4116: 4091: 4090: 4065: 4064: 4045: 4044: 4025: 4024: 4003: 3998: 3997: 3971: 3930: 3929: 3928:. We have that, 3908: 3903: 3902: 3877: 3876: 3857: 3856: 3835: 3830: 3829: 3804: 3803: 3784: 3783: 3758: 3757: 3732: 3731: 3712: 3711: 3710:sunflower. Let 3692: 3691: 3666: 3665: 3625: 3624: 3599: 3598: 3573: 3572: 3525: 3508: 3507: 3485: 3484: 3450: 3449: 3446: 3440: 3395: 3394: 3342: 3341: 3279: 3262: 3261: 3260: 3239: 3213: 3212: 3187: 3186: 3165: 3139: 3138: 3113: 3112: 3093: 3092: 3073: 3072: 3047: 3046: 3025: 2999: 2998: 2973: 2972: 2961: 2877: 2876: 2857: 2856: 2837: 2836: 2817: 2816: 2742: 2741: 2548: 2506: 2505: 2481: 2476: 2475: 2456: 2455: 2434: 2429: 2428: 2403: 2402: 2353: 2352: 2331: 2326: 2325: 2306: 2305: 2286: 2285: 2266: 2265: 2246: 2245: 2224: 2219: 2218: 2193: 2192: 2171: 2166: 2165: 2146: 2145: 2124: 2119: 2118: 2042: 2037: 2036: 2008: 2007: 1986: 1981: 1980: 1937: 1936: 1917: 1916: 1897: 1896: 1875: 1870: 1869: 1848: 1829: 1816: 1805: 1804: 1776: 1775: 1756: 1755: 1736: 1735: 1714: 1709: 1708: 1689: 1688: 1663: 1662: 1641: 1628: 1623: 1622: 1595: 1576: 1563: 1558: 1557: 1538: 1537: 1518: 1517: 1498: 1497: 1478: 1477: 1431: 1430: 1408: 1407: 1388: 1387: 1366: 1343: 1342: 1323: 1322: 1299: 1298: 1279: 1278: 1251: 1207: 1206: 1200:sunflower lemma 1193: 1191:Sunflower lemma 1169: 1168: 1149: 1148: 1129: 1128: 1109: 1108: 1089: 1088: 1069: 1068: 1046: 1045: 1026: 1025: 991: 990: 971: 970: 951: 950: 916: 915: 890: 889: 864: 863: 830: 829: 810: 809: 790: 789: 770: 769: 750: 749: 730: 729: 704: 703: 684: 683: 664: 663: 635: 634: 597: 596: 590: 558: 557: 538: 537: 514: 513: 494: 493: 474: 473: 454: 453: 434: 433: 414: 413: 382: 381: 362: 361: 342: 341: 322: 321: 299: 298: 279: 278: 257: 256: 232: 231: 212: 211: 188: 187: 164: 163: 160: 148:sunflower lemma 126: 125: 76: 75: 51: 44: 41: 40: 35: 32: 28: 23: 22: 15: 12: 11: 5: 6199: 6197: 6189: 6188: 6183: 6178: 6173: 6163: 6162: 6157: 6156: 6144: 6132: 6119:(3): 381–389. 6099: 6087: 6075: 6051: 6039: 6026:(3): 381–389. 6006: 5994: 5964: 5952: 5924: 5907: 5890: 5889: 5887: 5884: 5883: 5882: 5874: 5873:External links 5871: 5869: 5868: 5854: 5848:, New Series, 5841: 5812: 5778: 5773: 5759:Kunen, Kenneth 5755: 5743: 5730: 5709: 5664: 5631:(3): 225–231, 5611: 5565: 5552: 5520: 5518: 5515: 5514: 5513: 5506: 5503: 5490: 5468: 5464: 5443: 5440: 5435: 5431: 5409: 5406: 5385: 5382: 5379: 5357: 5353: 5329: 5326: 5322: 5319: 5298: 5278: 5258: 5236: 5232: 5222:stationary in 5211: 5187: 5184: 5181: 5176: 5172: 5168: 5165: 5162: 5159: 5156: 5153: 5150: 5128: 5124: 5120: 5117: 5114: 5111: 5108: 5105: 5085: 5065: 5060: 5056: 5052: 5049: 5046: 5041: 5037: 5033: 5013: 4991: 4987: 4964: 4960: 4933: 4929: 4908: 4851: 4828: 4815:collection of 4798: 4774: 4754: 4732: 4719: 4716: 4689: 4685: 4681: 4662: 4636: 4633: 4630: 4627: 4624: 4620: 4603: 4600: 4587: 4584: 4581: 4578: 4575: 4572: 4569: 4563: 4560: 4555: 4534: 4531: 4528: 4504: 4500: 4496: 4491: 4485: 4481: 4476: 4455: 4435: 4413: 4409: 4386: 4382: 4360: 4354: 4350: 4345: 4324: 4302: 4298: 4277: 4255: 4251: 4230: 4208: 4205: 4202: 4199: 4196: 4193: 4190: 4187: 4184: 4181: 4178: 4175: 4172: 4169: 4166: 4163: 4160: 4157: 4154: 4151: 4148: 4145: 4142: 4139: 4136: 4133: 4130: 4127: 4124: 4098: 4078: 4075: 4072: 4052: 4032: 4010: 4006: 3984: 3978: 3974: 3969: 3965: 3961: 3957: 3953: 3949: 3946: 3943: 3940: 3937: 3915: 3911: 3890: 3887: 3884: 3864: 3842: 3838: 3817: 3814: 3811: 3791: 3771: 3768: 3765: 3745: 3742: 3739: 3719: 3699: 3690:-sets with no 3679: 3676: 3673: 3653: 3650: 3647: 3644: 3641: 3638: 3635: 3632: 3612: 3609: 3606: 3586: 3583: 3580: 3558: 3555: 3552: 3549: 3546: 3543: 3540: 3537: 3532: 3528: 3524: 3521: 3518: 3515: 3492: 3472: 3469: 3466: 3463: 3460: 3457: 3445: 3442: 3426: 3423: 3420: 3417: 3414: 3411: 3408: 3405: 3402: 3382: 3379: 3376: 3373: 3370: 3367: 3364: 3361: 3358: 3355: 3352: 3349: 3327: 3324: 3321: 3318: 3315: 3312: 3309: 3306: 3303: 3300: 3297: 3294: 3291: 3286: 3282: 3278: 3275: 3272: 3269: 3246: 3242: 3238: 3235: 3232: 3229: 3226: 3223: 3220: 3200: 3197: 3194: 3172: 3168: 3164: 3161: 3158: 3155: 3152: 3149: 3146: 3126: 3123: 3120: 3111:; for example 3100: 3080: 3060: 3057: 3054: 3032: 3028: 3024: 3021: 3018: 3015: 3012: 3009: 3006: 2986: 2983: 2980: 2960: 2957: 2944: 2941: 2938: 2935: 2932: 2929: 2926: 2923: 2920: 2917: 2914: 2911: 2908: 2905: 2902: 2899: 2896: 2893: 2890: 2887: 2884: 2864: 2844: 2824: 2804: 2801: 2798: 2795: 2792: 2789: 2786: 2783: 2780: 2777: 2774: 2771: 2768: 2765: 2762: 2758: 2754: 2750: 2738: 2737: 2726: 2723: 2720: 2717: 2714: 2711: 2708: 2705: 2702: 2699: 2696: 2693: 2690: 2687: 2684: 2681: 2678: 2674: 2670: 2666: 2662: 2659: 2656: 2653: 2650: 2647: 2644: 2641: 2638: 2635: 2632: 2629: 2626: 2623: 2620: 2617: 2614: 2611: 2608: 2605: 2602: 2599: 2596: 2593: 2590: 2587: 2584: 2581: 2577: 2573: 2569: 2565: 2561: 2555: 2551: 2546: 2540: 2537: 2534: 2530: 2526: 2522: 2518: 2514: 2488: 2484: 2463: 2441: 2437: 2416: 2413: 2410: 2387: 2384: 2381: 2378: 2375: 2372: 2369: 2366: 2363: 2360: 2338: 2334: 2324:, the size of 2313: 2293: 2273: 2253: 2231: 2227: 2206: 2203: 2200: 2178: 2174: 2153: 2131: 2127: 2115: 2114: 2103: 2100: 2097: 2094: 2091: 2087: 2084: 2081: 2078: 2075: 2072: 2069: 2066: 2063: 2060: 2057: 2054: 2049: 2045: 2021: 2018: 2015: 1993: 1989: 1968: 1965: 1962: 1959: 1956: 1953: 1950: 1947: 1944: 1935:is bounded by 1924: 1904: 1882: 1878: 1855: 1851: 1847: 1844: 1841: 1836: 1832: 1828: 1823: 1819: 1815: 1812: 1789: 1786: 1783: 1763: 1743: 1721: 1717: 1696: 1676: 1673: 1670: 1648: 1644: 1640: 1635: 1631: 1610: 1607: 1602: 1598: 1594: 1591: 1588: 1583: 1579: 1575: 1570: 1566: 1545: 1525: 1505: 1485: 1465: 1462: 1459: 1456: 1453: 1450: 1447: 1444: 1441: 1438: 1415: 1395: 1373: 1369: 1365: 1362: 1359: 1356: 1353: 1350: 1330: 1306: 1286: 1275: 1274: 1263: 1258: 1254: 1250: 1247: 1244: 1241: 1238: 1235: 1232: 1229: 1226: 1223: 1220: 1217: 1214: 1192: 1189: 1176: 1156: 1136: 1116: 1096: 1076: 1053: 1033: 1013: 1010: 1007: 1004: 1001: 998: 978: 958: 938: 935: 932: 929: 926: 923: 903: 900: 897: 877: 874: 871: 837: 817: 797: 777: 768:has more than 757: 737: 717: 714: 711: 691: 671: 648: 645: 642: 619: 616: 613: 610: 607: 604: 589: 586: 565: 545: 521: 501: 481: 461: 441: 421: 401: 398: 395: 392: 389: 369: 349: 329: 306: 286: 264: 239: 219: 195: 171: 159: 156: 133: 83: 42: 36: 33: 27: 24: 14: 13: 10: 9: 6: 4: 3: 2: 6198: 6187: 6186:Combinatorics 6184: 6182: 6179: 6177: 6174: 6172: 6169: 6168: 6166: 6153: 6148: 6145: 6142: 6136: 6133: 6127: 6122: 6118: 6114: 6110: 6103: 6100: 6096: 6091: 6088: 6084: 6079: 6076: 6065: 6061: 6055: 6052: 6048: 6043: 6040: 6034: 6029: 6025: 6021: 6017: 6010: 6007: 5997: 5991: 5987: 5983: 5979: 5975: 5968: 5965: 5961: 5956: 5953: 5941: 5937: 5931: 5929: 5925: 5921: 5895: 5892: 5885: 5881: 5877: 5876: 5872: 5865: 5864: 5859: 5855: 5851: 5847: 5842: 5838: 5833: 5829: 5825: 5818: 5813: 5810: 5806: 5801: 5796: 5792: 5788: 5784: 5779: 5776: 5770: 5766: 5765: 5760: 5756: 5752: 5748: 5744: 5741: 5737: 5733: 5727: 5723: 5719: 5715: 5710: 5707: 5703: 5699: 5695: 5691: 5687: 5683: 5679: 5678: 5673: 5669: 5665: 5662: 5658: 5654: 5650: 5646: 5642: 5638: 5634: 5630: 5626: 5625: 5624:Combinatorica 5620: 5616: 5612: 5609: 5605: 5601: 5597: 5593: 5589: 5584: 5579: 5576:(7): 112367, 5575: 5571: 5566: 5563: 5559: 5555: 5549: 5545: 5541: 5536: 5531: 5527: 5522: 5521: 5516: 5512: 5509: 5508: 5504: 5502: 5488: 5466: 5462: 5441: 5438: 5433: 5429: 5407: 5404: 5383: 5380: 5377: 5355: 5351: 5343: 5327: 5324: 5320: 5317: 5296: 5276: 5256: 5234: 5230: 5209: 5201: 5200:Fodor's lemma 5182: 5179: 5174: 5170: 5160: 5154: 5148: 5126: 5122: 5118: 5112: 5106: 5103: 5083: 5058: 5054: 5050: 5047: 5044: 5039: 5035: 4989: 4985: 4962: 4958: 4949: 4931: 4927: 4906: 4897: 4895: 4891: 4887: 4883: 4879: 4876: 4872: 4868: 4867:set-theoretic 4865: 4864:combinatorial 4840: 4818: 4814: 4810: 4786: 4744: 4717: 4715: 4713: 4709: 4705: 4687: 4683: 4679: 4660: 4652: 4631: 4625: 4622: 4618: 4609: 4601: 4599: 4582: 4579: 4576: 4570: 4567: 4561: 4558: 4553: 4532: 4529: 4526: 4517: 4498: 4483: 4479: 4453: 4433: 4411: 4407: 4384: 4380: 4352: 4348: 4322: 4300: 4296: 4275: 4253: 4249: 4228: 4219: 4203: 4200: 4194: 4191: 4188: 4182: 4173: 4170: 4164: 4161: 4158: 4152: 4146: 4140: 4137: 4134: 4131: 4128: 4122: 4113: 4110: 4096: 4076: 4073: 4070: 4050: 4030: 4008: 4004: 3976: 3972: 3963: 3955: 3944: 3941: 3938: 3913: 3909: 3901:partition of 3888: 3885: 3882: 3862: 3840: 3836: 3815: 3812: 3809: 3789: 3769: 3766: 3763: 3743: 3740: 3737: 3717: 3697: 3677: 3674: 3671: 3648: 3645: 3642: 3639: 3636: 3630: 3610: 3607: 3604: 3584: 3581: 3578: 3569: 3556: 3550: 3547: 3544: 3538: 3535: 3530: 3522: 3519: 3516: 3504: 3490: 3467: 3464: 3461: 3455: 3443: 3441: 3438: 3421: 3418: 3415: 3412: 3406: 3403: 3400: 3374: 3371: 3365: 3362: 3359: 3353: 3350: 3347: 3319: 3313: 3310: 3307: 3304: 3298: 3292: 3289: 3284: 3280: 3273: 3270: 3267: 3244: 3240: 3236: 3230: 3227: 3224: 3218: 3198: 3195: 3192: 3170: 3166: 3162: 3156: 3153: 3150: 3144: 3124: 3121: 3118: 3098: 3078: 3058: 3055: 3052: 3030: 3026: 3022: 3016: 3013: 3010: 3004: 2984: 2981: 2978: 2970: 2966: 2958: 2956: 2939: 2936: 2933: 2930: 2927: 2921: 2915: 2912: 2909: 2903: 2900: 2894: 2891: 2888: 2882: 2875:sets. Hence, 2862: 2842: 2822: 2799: 2796: 2793: 2790: 2787: 2781: 2775: 2772: 2769: 2763: 2760: 2752: 2724: 2721: 2715: 2712: 2709: 2706: 2703: 2697: 2691: 2688: 2685: 2679: 2676: 2668: 2660: 2654: 2651: 2648: 2645: 2642: 2636: 2630: 2627: 2624: 2618: 2615: 2609: 2606: 2600: 2597: 2594: 2591: 2588: 2582: 2571: 2563: 2553: 2549: 2538: 2535: 2532: 2528: 2524: 2516: 2504: 2503: 2502: 2486: 2482: 2461: 2439: 2435: 2414: 2411: 2408: 2399: 2385: 2382: 2376: 2373: 2370: 2367: 2364: 2358: 2336: 2332: 2311: 2291: 2271: 2251: 2229: 2225: 2204: 2201: 2198: 2176: 2172: 2151: 2129: 2125: 2101: 2095: 2092: 2089: 2085: 2082: 2079: 2076: 2073: 2067: 2058: 2052: 2047: 2043: 2035: 2034: 2033: 2019: 2016: 2013: 1991: 1987: 1963: 1960: 1957: 1951: 1948: 1945: 1942: 1922: 1902: 1880: 1876: 1868:. Since each 1853: 1849: 1845: 1842: 1839: 1834: 1830: 1826: 1821: 1817: 1813: 1810: 1801: 1787: 1784: 1781: 1761: 1741: 1719: 1715: 1694: 1674: 1671: 1668: 1646: 1642: 1638: 1633: 1629: 1608: 1605: 1600: 1596: 1592: 1589: 1586: 1581: 1577: 1573: 1568: 1564: 1543: 1523: 1503: 1483: 1463: 1460: 1457: 1454: 1448: 1445: 1442: 1436: 1427: 1413: 1393: 1371: 1363: 1360: 1357: 1351: 1348: 1328: 1320: 1317:are positive 1304: 1284: 1261: 1256: 1248: 1245: 1242: 1236: 1233: 1230: 1224: 1221: 1218: 1212: 1205: 1204: 1203: 1201: 1197: 1190: 1188: 1174: 1154: 1134: 1114: 1094: 1074: 1065: 1051: 1031: 1008: 1005: 1002: 996: 976: 956: 933: 930: 927: 921: 901: 898: 895: 875: 872: 869: 860: 857: 855: 851: 835: 815: 795: 775: 755: 735: 715: 712: 709: 689: 669: 662: 646: 643: 640: 633: 614: 611: 608: 602: 593: 587: 585: 583: 579: 563: 543: 535: 519: 499: 479: 459: 439: 419: 399: 396: 393: 390: 387: 367: 347: 327: 320: 304: 284: 276: 253: 237: 217: 209: 193: 185: 169: 157: 155: 153: 149: 145: 122: 117: 114: 109: 107: 103: 99: 95: 72: 68: 64: 55: 49: 39: 19: 6181:Intersection 6147: 6135: 6116: 6112: 6102: 6090: 6078: 6067:. Retrieved 6063: 6054: 6042: 6023: 6019: 6009: 5999:, retrieved 5977: 5967: 5962:, p. 3. 5955: 5944:. Retrieved 5939: 5894: 5862: 5858:Tao, Terence 5849: 5845: 5830:(1): 29–38, 5827: 5823: 5793:(2): 11887, 5790: 5786: 5763: 5750: 5747:Jech, Thomas 5713: 5684:(1): 85–90, 5681: 5675: 5628: 5622: 5573: 5569: 5525: 4898: 4862:-lemma is a 4841: 4789: 4787: 4723: 4721: 4710:, to design 4605: 4518: 4220: 4114: 4111: 3570: 3505: 3447: 3439: 2964: 2962: 2835:contains an 2739: 2400: 2116: 1802: 1428: 1277:That is, if 1276: 1199: 1194: 1066: 861: 858: 594: 591: 533: 255: 251: 161: 151: 147: 124: 120: 118: 113:Venn diagram 110: 105: 102:intersection 74: 70: 60: 5668:ErdĹ‘s, Paul 5342:cardinality 4950:subsets of 4871:upper bound 4817:finite sets 4813:uncountable 4335:to produce 4221:Proof. Let 3571:Proof. For 788:sets, then 6176:Set theory 6165:Categories 6083:Rao (2020) 6069:2019-11-10 6001:2022-05-02 5946:2021-12-10 5753:, Springer 5751:Set Theory 5619:Frankl, P. 5583:2009.09327 5535:1908.08483 5517:References 5249:such that 5076:enumerate 2740:Hence, if 380:, we have 184:set system 150:, and the 63:set theory 5906:Δ 5852:: 399–400 5809:202558957 5698:0024-6107 5645:0209-9683 5608:221818818 5562:201314765 5489:β 5463:ω 5439:⊆ 5352:ω 5325:⊆ 5277:β 5231:ω 5183:α 5180:∩ 5175:α 5155:α 5123:ω 5113:α 5107:⁡ 5064:⟩ 5055:ω 5048:α 5040:α 5032:⟨ 5012:Δ 4986:ω 4959:ω 4948:countable 4928:ω 4884:that the 4850:Δ 4839:-system. 4827:Δ 4797:Δ 4785:-system. 4773:Δ 4753:Δ 4731:Δ 4626:⁡ 4568:≤ 4484:∗ 4426:over all 4353:∗ 4301:∗ 4254:∗ 4201:− 4171:− 4147:≥ 4115:Theorem. 4074:− 4009:∗ 3977:∗ 3964:≤ 3942:− 3914:∗ 3886:− 3841:∗ 3813:− 3767:− 3741:− 3675:− 3640:− 3608:− 3597:a set of 3536:≤ 3520:− 3506:Theorem. 3419:⁡ 3366:⁡ 3314:⁡ 3308:⁡ 3293:⁡ 3237:≤ 3185:for some 3163:≤ 3023:≤ 2931:− 2913:− 2901:≤ 2791:− 2773:− 2761:≥ 2722:− 2707:− 2689:− 2677:≤ 2661:− 2646:− 2628:− 2616:≤ 2607:− 2592:− 2564:≤ 2536:∈ 2529:∑ 2525:≤ 2412:∈ 2383:− 2368:− 2202:− 2093:∈ 2080:∈ 2074:∣ 2062:∖ 2017:∈ 2006:for some 1979:. Define 1961:− 1949:≤ 1846:∪ 1843:⋯ 1840:∪ 1827:∪ 1639:∩ 1606:∈ 1590:… 1461:− 1455:≤ 1361:− 1246:− 1231:≤ 862:For each 713:∈ 576:, may be 391:∩ 263:Δ 252:sunflower 210:of a set 162:Suppose 132:Δ 82:Δ 71:sunflower 5860:(2020), 5761:(1980), 5749:(2003), 5672:Rado, R. 5661:14043028 5615:Deza, M. 5505:See also 5408:′ 5321:′ 5309:. Build 1319:integers 632:integers 582:disjoint 319:distinct 5740:2238686 5706:0111692 5653:0637827 5600:4240687 5511:Cap set 5396:are in 5141:, let 5096:. For 5004:-sized 4892: ( 4875:forcing 4706:of the 2815:, then 1024:, then 661:integer 536:of the 275:-system 208:subsets 94:-system 5992:  5807:  5771:  5738:  5728:  5704:  5696:  5659:  5651:  5643:  5606:  5598:  5560:  5550:  5202:, fix 5198:. By 4919:is an 4890:Shanin 4809:-lemma 4743:-lemma 4109:sets. 2032:to be 1426:sets. 144:-lemma 106:kernel 5886:Notes 5820:(PDF) 5805:S2CID 5657:S2CID 5604:S2CID 5578:arXiv 5558:S2CID 5530:arXiv 5421:then 4878:poset 2117:Then 850:ErdĹ‘s 748:, if 578:empty 250:is a 186:over 182:is a 121:large 5990:ISBN 5791:2020 5769:ISBN 5726:ISBN 5694:ISSN 5641:ISSN 5548:ISBN 5381:< 5051:< 4894:1946 4842:The 4788:The 4241:and 3259:for 3196:> 3056:> 2982:> 2963:The 2191:has 1803:Let 1785:< 1297:and 899:> 873:> 854:Rado 852:and 534:some 340:and 254:(or 98:sets 69:, a 65:and 6121:doi 6028:doi 5982:doi 5832:doi 5795:doi 5718:doi 5686:doi 5633:doi 5588:doi 5574:344 5540:doi 5340:of 5289:on 5164:sup 4899:If 4896:). 4623:log 4545:is 4446:in 4315:to 3416:log 3363:log 3311:log 3305:log 3290:log 969:of 360:in 297:of 73:or 6167:: 6117:12 6115:. 6111:. 6062:. 6024:12 6022:. 6018:. 5988:, 5976:, 5938:. 5927:^ 5850:53 5828:60 5826:, 5822:, 5803:, 5789:, 5785:, 5736:MR 5734:, 5724:, 5702:MR 5700:, 5692:, 5682:35 5670:; 5655:, 5649:MR 5647:, 5639:, 5627:, 5617:; 5602:, 5596:MR 5594:, 5586:, 5572:, 5556:, 5546:, 5538:, 5104:cf 4554:10 3996:. 3503:. 3437:. 2997:, 2725:1. 2501:: 2398:. 1800:. 1064:. 888:, 146:, 6154:. 6129:. 6123:: 6097:. 6085:. 6072:. 6049:. 6036:. 6030:: 5984:: 5949:. 5834:: 5797:: 5720:: 5688:: 5635:: 5629:1 5590:: 5580:: 5542:: 5532:: 5467:1 5442:j 5434:i 5430:A 5405:S 5384:j 5378:i 5356:2 5328:S 5318:S 5297:S 5257:f 5235:2 5210:S 5186:) 5171:A 5167:( 5161:= 5158:) 5152:( 5149:f 5127:1 5119:= 5116:) 5110:( 5084:W 5059:2 5045:: 5036:A 4990:2 4963:2 4932:2 4907:W 4688:0 4684:C 4680:A 4661:3 4635:) 4632:n 4629:( 4619:n 4586:) 4583:3 4580:, 4577:k 4574:( 4571:f 4562:2 4559:k 4533:3 4530:= 4527:r 4503:| 4499:F 4495:| 4490:| 4480:F 4475:| 4454:F 4434:A 4412:A 4408:F 4385:A 4381:F 4359:| 4349:F 4344:| 4323:A 4297:F 4276:A 4250:F 4229:F 4207:) 4204:1 4198:) 4195:r 4192:, 4189:b 4186:( 4183:f 4180:( 4177:) 4174:1 4168:) 4165:r 4162:, 4159:a 4156:( 4153:f 4150:( 4144:) 4141:r 4138:, 4135:b 4132:+ 4129:a 4126:( 4123:f 4097:r 4077:1 4071:r 4051:r 4031:r 4005:H 3983:| 3973:H 3968:| 3960:| 3956:H 3952:| 3948:) 3945:1 3939:r 3936:( 3910:H 3889:1 3883:r 3863:H 3837:H 3816:1 3810:r 3790:H 3770:1 3764:r 3744:1 3738:r 3718:H 3698:r 3678:1 3672:k 3652:) 3649:r 3646:, 3643:1 3637:k 3634:( 3631:h 3611:1 3605:r 3585:1 3582:= 3579:k 3557:. 3554:) 3551:r 3548:, 3545:k 3542:( 3539:f 3531:k 3527:) 3523:1 3517:r 3514:( 3491:r 3471:) 3468:r 3465:, 3462:k 3459:( 3456:f 3425:) 3422:k 3413:r 3410:( 3407:O 3404:= 3401:C 3381:) 3378:) 3375:k 3372:r 3369:( 3360:r 3357:( 3354:O 3351:= 3348:C 3338:. 3326:) 3323:) 3320:k 3317:( 3302:) 3299:k 3296:( 3285:3 3281:r 3277:( 3274:O 3271:= 3268:C 3245:k 3241:C 3234:) 3231:r 3228:, 3225:k 3222:( 3219:f 3199:0 3193:C 3171:k 3167:C 3160:) 3157:3 3154:, 3151:k 3148:( 3145:f 3125:3 3122:= 3119:r 3099:r 3079:r 3059:0 3053:C 3031:k 3027:C 3020:) 3017:r 3014:, 3011:k 3008:( 3005:f 2985:2 2979:r 2943:) 2940:r 2937:, 2934:1 2928:k 2925:( 2922:f 2919:) 2916:1 2910:r 2907:( 2904:k 2898:) 2895:r 2892:, 2889:k 2886:( 2883:f 2863:k 2843:r 2823:W 2803:) 2800:r 2797:, 2794:1 2788:k 2785:( 2782:f 2779:) 2776:1 2770:r 2767:( 2764:k 2757:| 2753:W 2749:| 2719:) 2716:r 2713:, 2710:1 2704:k 2701:( 2698:f 2695:) 2692:1 2686:r 2683:( 2680:k 2673:| 2669:A 2665:| 2658:) 2655:r 2652:, 2649:1 2643:k 2640:( 2637:f 2634:) 2631:1 2625:r 2622:( 2619:k 2613:) 2610:1 2604:) 2601:r 2598:, 2595:1 2589:k 2586:( 2583:f 2580:( 2576:| 2572:A 2568:| 2560:| 2554:a 2550:W 2545:| 2539:A 2533:a 2521:| 2517:W 2513:| 2487:a 2483:W 2462:A 2440:i 2436:A 2415:W 2409:S 2386:1 2380:) 2377:r 2374:, 2371:1 2365:k 2362:( 2359:f 2337:a 2333:W 2312:r 2292:W 2272:a 2252:W 2230:a 2226:W 2205:1 2199:k 2177:a 2173:W 2152:W 2130:a 2126:W 2102:. 2099:} 2096:W 2090:S 2086:, 2083:S 2077:a 2071:} 2068:a 2065:{ 2059:S 2056:{ 2053:= 2048:a 2044:W 2020:A 2014:a 1992:a 1988:W 1967:) 1964:1 1958:r 1955:( 1952:k 1946:t 1943:k 1923:A 1903:k 1881:i 1877:A 1854:t 1850:A 1835:2 1831:A 1822:1 1818:A 1814:= 1811:A 1788:r 1782:t 1762:r 1742:W 1720:i 1716:A 1695:W 1675:j 1672:= 1669:i 1647:j 1643:A 1634:i 1630:A 1609:W 1601:t 1597:A 1593:, 1587:, 1582:2 1578:A 1574:, 1569:1 1565:A 1544:r 1524:W 1504:r 1484:W 1464:1 1458:r 1452:) 1449:r 1446:, 1443:1 1440:( 1437:f 1414:r 1394:k 1372:k 1368:) 1364:1 1358:r 1355:( 1352:! 1349:k 1329:W 1305:r 1285:k 1262:. 1257:k 1253:) 1249:1 1243:r 1240:( 1237:! 1234:k 1228:) 1225:r 1222:, 1219:k 1216:( 1213:f 1175:k 1155:k 1135:W 1115:W 1095:W 1075:W 1052:r 1032:F 1012:) 1009:r 1006:, 1003:k 1000:( 997:f 977:k 957:F 937:) 934:r 931:, 928:k 925:( 922:f 902:0 896:r 876:0 870:k 836:n 816:r 796:W 776:n 756:W 736:k 716:W 710:S 690:W 670:n 647:r 644:, 641:k 618:) 615:r 612:, 609:k 606:( 603:f 564:S 544:W 520:U 500:W 480:S 460:U 440:W 420:W 400:S 397:= 394:B 388:A 368:W 348:B 328:A 305:U 285:S 238:W 218:U 194:U 170:W 50:. 31:: 20:)

Index

Delta-system lemma
(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

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