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Expander graph

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containing roughly the larger half of the inputs. To achieve this, sequentially process each matching by comparing the registers paired up by the edges of this matching and correct any inputs that are out of order. Specifically, for each edge of the matching, if the larger input is in the register in
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is the minimum number of edges that need to be cut in order to split the graph in two. The edge expansion normalizes this concept by dividing with smallest number of vertices among the two parts. To see how the normalization can drastically change the value, consider the following example. Take two
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Sorting networks take a set of inputs and perform a series of parallel steps to sort the inputs. A parallel step consists of performing any number of disjoint comparisons and potentially swapping pairs of compared inputs. The depth of a network is given by the number of parallel steps it takes.
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The original motivation for expanders is to build economical robust networks (phone or computer): an expander with bounded degree is precisely an asymptotic robust graph with the number of edges growing linearly with size (number of vertices), for all subsets.
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introduced the zig-zag product in 2003. Roughly speaking, the zig-zag product of two expander graphs produces a graph with only slightly worse expansion. Therefore, a zig-zag product can also be used to construct families of expander graphs. If
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states that, when sampling many independent samples from a random variable in the range , with high probability the average of our samples is close to the expectation of the random variable. The expander walk sampling lemma, due to
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There are many results that show the existence of graphs with good expansion properties through probabilistic arguments. In fact, the existence of expanders was first proved by Pinsker who showed that for a randomly chosen
5007:, typical behavior, explicit constructions, and algorithms. Extremal problems focus on the bounding of expansion parameters, while typical behavior problems characterize how the expansion parameters are distributed over 5712: 3980: 5624: 3427: 2433: 5917:
The vertices of the graph can be thought of as registers that contain inputs and the edges can be thought of as wires that compare the inputs of two registers. At the start, arbitrarily place half of the inputs in
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Note that property (1) implies that the zig-zag product of two expander graphs is also an expander graph, thus zig-zag products can be used inductively to create a family of expander graphs.
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There are four general strategies for explicitly constructing families of expander graphs. The first strategy is algebraic and group-theoretic, the second strategy is analytic and uses
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of a graph is the maximum distance between two vertices, where the distance between two vertices is defined to be the shortest path between them. Chung showed that the diameter of an
4711: 4647: 1395: 1003: 2273: 1824: 1230: 4359:{\displaystyle \phi (\lambda _{1},\lambda _{2})={\frac {1}{2}}(1-\lambda _{2}^{2})\lambda _{2}+{\frac {1}{2}}{\sqrt {(1-\lambda _{2}^{2})^{2}\lambda _{1}^{2}+4\lambda _{2}^{2}}}.} 5301: 4744: 5011:. Explicit constructions focus on constructing graphs that optimize certain parameters, and algorithmic questions study the evaluation and estimation of parameters. 3110:
are known for various variants of expander graphs. The following construction is due to Margulis and has been analysed by Gabber and Galil. For every natural number
2743: 2719: 4590: 2534: 3652: 2853: 5772:. While this is asymptotically the best known depth for a sorting network, the reliance on expanders makes the constant bound too large for practical use. 2309:. Its eigenvalues are between −1 and 1. For not necessarily regular graphs, the spectrum of a graph can be defined similarly using the eigenvalues of the 158: 2036: 5649: 3923: 5545: 7678: 3283: 2356: 1784:. The latter is a weaker notion that holds also for bipartite graphs and is still useful for many applications, such as the Alon-Chung lemma. 7571: 7385: 7341: 7305: 7261: 7206: 7182: 2278:
The normalized versions of these definitions are also widely used and more convenient in stating some results. Here one considers the matrix
2139: 271: 5160: 2951: 3218: 7281: 590: 6774: 1943: 7697: 953:{\displaystyle h(G)=\min _{\emptyset \subsetneq S\subsetneq V(G)}{\frac {E({S},{\overline {S}})}{\min\{|S|,|{\overline {S}}|\}}}.} 418: 3168: 5742:, states that this also holds true when sampling from a walk on an expander graph. This is particularly useful in the theory of 2761: 1675: 1558: 7066: 4965: 712: 130: 59: 7651: 6237:
N. Alon and F. R. K. Chung, Explicit construction of linear sized tolerant networks. Discrete Math., vol. 72, pp. 15-19, 1988.
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is empty. Every connected graph is an expander; however, different connected graphs have different expansion parameters. The
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vertices. The lifted graph inherits the eigenvalues of the original graph, and has some additional eigenvalues. Bilu and
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Bilu, Yonatan; Linial, Nathan (2004-04-08). "Constructing expander graphs by 2-lifts and discrepancy vs. spectral gap".
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in magnitude. They also showed that if the starting graph is a good enough expander, then a good 2-lift can be found in
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expansion. Expander constructions have spawned research in pure and applied mathematics, with several applications to
43: 7198: 3453: 6938: 6149: 5503:, is the minimum number of colors needed such that adjacent vertices have different colors. Hoffman showed that 3590: 1124:{\displaystyle h_{\text{out}}(G)=\min _{0<|S|\leq {\frac {n}{2}}}{\frac {|\partial _{\text{out}}(S)|}{|S|}},} 6572: 2302: 102: 4667: 4603: 1364: 1351:{\displaystyle h_{\text{in}}(G)=\min _{0<|S|\leq {\frac {n}{2}}}{\frac {|\partial _{\text{in}}(S)|}{|S|}},} 6995: 7712: 6899: 5630: 4945: 4762:, who used the method of interlacing polynomials. As a result, they obtained an alternative construction of 4372:
Intuitively, the construction of the zig-zag product can be thought of in the following way. Each vertex of
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is the second largest eigenvalue in absolute value. As a direct consequence, we know that for every fixed
3080: 3767:(1988), Margulis (1988), and Morgenstern (1994) show how Ramanujan graphs can be constructed explicitly. 6154: 5746:, since sampling according to an expander walk uses many fewer random bits than sampling independently. 5425:{\displaystyle \left|E(S,T)-{\frac {d\cdot |S|\cdot |T|}{n}}\right|\leq \lambda {\sqrt {|S|\cdot |T|}}.} 5020: 5004: 1903: 1662: 110: 67: 55: 47: 7542:
Studies in Complexity and Cryptography. Miscellanea on the Interplay between Randomness and Computation
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Similar connections between vertex isoperimetric numbers and the spectral gap have also been studied:
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vertices, each associated to a different edge connected to the vertex. Each vertex is now labeled as
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Friedman, Joel (2004-05-05). "A proof of Alon's second eigenvalue conjecture and related problems".
6362: 6014:. Furthermore, this property remains true throughout the rest of the process. Now, suppose for some 4716: 7675: 7485: 7368: 7053: 2841: 51: 7692: 7632: 7602: 7585: 7507: 7488:(1984), "Difference equations, isoperimetric inequality and transience of certain random walks", 7473: 7427: 7391: 7347: 7311: 7104: 7031: 6964: 6908: 6869: 6846: 6799: 6780: 6662: 6644: 6615: 6581: 6552: 6526: 6485: 6466: 6375: 4747: 3760: 3508: 7285: 2438:
Consequently, for constant degree graphs, vertex and edge expansion are qualitatively the same.
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edges between the two graphs by connecting their vertices one-to-one. The minimum cut will be
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Friedman, Joel; Puder, Doron (2023). "A note on the trace method for random regular graphs".
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Alon, Noga (1986). "Eigenvalues, geometric expanders, sorting in rounds, and ramsey theory".
113:. Informally, a graph is a good expander if it has low degree and high expansion parameters. 7624: 7594: 7559: 7540: 7528: 7497: 7465: 7419: 7403: 7373: 7327: 7293: 7239: 7224: 7116: 7075: 7015: 6976: 6918: 6879: 6830: 6819:
Bilu, Yonatan; Linial, Nathan (2006). "Lifts, discrepancy and nearly optimal spectral gap".
6762: 6755:"Entropy waves, the zig-zag graph product, and new constant-degree expanders and extractors" 6654: 6599: 6544: 6450: 6367: 5154:. If the two sets are not disjoint, edges in their intersection are counted twice, that is, 4961: 4933: 3103: 2837: 2310: 1496: 1492: 1451: 63: 2483:. By standard spectral graph theory, the trivial eigenvalue of the adjacency operator of a 7682: 7615: 6721: 6687: 6144: 5755: 5743: 4969: 4953: 4791: 4766: 4763: 4755: 4650: 4016: 4000: 3992: 3639: 3502: 3092: 3084: 2728: 2704: 2639: 2628:{\displaystyle {\tfrac {1}{2}}(d-\lambda _{2})\leq h(G)\leq {\sqrt {2d(d-\lambda _{2})}}.} 2318: 1524:. It is known that all these eigenvalues are in and more specifically, it is known that 7277: 6294:
B. Mohar. Isoperimetric numbers of graphs. J. Combin. Theory Ser. B, 47(3):274–291, 1989.
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The expansion parameters defined above are related to each other. In particular, for any
86:. Different formalisations of these notions give rise to different notions of expanders: 7440: 7011: 6729: 6595: 6540: 5761:
Expander graphs play an important role in the AKS sorting network, which achieves depth
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In 2003, Joel Friedman both proved the conjecture and specified what is meant by "most
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Hall, Chris; Puder, Doron; Sawin, William F. (2018). "Ramanujan coverings of graphs".
3740:{\displaystyle \lambda =\max _{|\lambda _{i}|<d}|\lambda _{i}|\leq 2{\sqrt {d-1}}.} 2940:{\displaystyle h_{\text{out}}(G)\leq \left({\sqrt {4(d-\lambda _{2})}}+1\right)^{2}-1} 7706: 7606: 7580: 7322:
Ajtai, M.; Komlós, J.; Szemerédi, E. (1987), "Deterministic simulation in LOGSPACE",
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The 43rd Annual IEEE Symposium on Foundations of Computer Science, 2002. Proceedings
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Within the AKS sorting network, expander graphs are used to construct bounded depth
259:{\displaystyle h(G)=\min _{0<|S|\leq {\frac {n}{2}}}{\frac {|\partial S|}{|S|}},} 7548:, Lecture Notes in Computer Science (Vol. 6650), vol. 6650, pp. 451–464, 7431: 7395: 7157: 6379: 5008: 4989: 4025: 3764: 3107: 1912: 39: 31: 7244: 6784: 6517:
Puder, Doron (2015-08-21). "Expansion of random graphs: New proofs, new results".
7670: 7563: 2123:{\displaystyle \lambda =\max _{v\perp u,v\neq 0}{\frac {\|Av\|_{2}}{\|v\|_{2}}},} 7216: 5447:-graphs are corollaries of the expander mixing lemmas, including the following. 4981: 4593: 2638:
In fact, the lower bound is tight. The lower bound is achieved in limit for the
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in which every subset of the vertices that is not "too large" has a "large"
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Gillman, D. (1998), "A Chernoff Bound for Random Walks on Expander Graphs",
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Puder, Doron (2015). "Expansion of random graphs: new proofs, new results".
5707:{\displaystyle \left\lceil \log {\frac {n}{\log(d/\lambda )}}\right\rceil .} 4937: 4600:-regular graph has a 2-lift in which the additional eigenvalues are at most 3975:{\displaystyle \tau =\left\lceil {\frac {{\sqrt {d-1}}+1}{2}}\right\rceil .} 3088: 2521: 7688:
Lecture notes from a course on expanders (by Nati Linial and Avi Wigderson)
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is. This violates the previous property however, and thus the output sets
5619:{\displaystyle \chi (G)\leq O\left({\frac {d}{\log(1+d/\lambda )}}\right).} 7423: 7297: 6737:. Foundations of Computer Science (FOCS), 2015 IEEE 56th Annual Symposium. 6703:. Foundations of Computer Science (FOCS), 2013 IEEE 54th Annual Symposium. 2325:, which are equal to the roots of the eigenvalues of the symmetric matrix 6883: 5295:
Then the expander mixing lemma says that the following inequality holds:
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Hence Ramanujan graphs have an asymptotically smallest possible value of
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of a graph is a subset of vertices with no two vertices adjacent. In an
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vertices, and each edge by a matching between the corresponding sets of
3422:{\displaystyle (x\pm 2y,y),(x\pm (2y+1),y),(x,y\pm 2x),(x,y\pm (2x+1)).} 2428:{\displaystyle h_{\text{out}}(G)\leq h(G)\leq d\cdot h_{\text{out}}(G).} 7511: 6454: 6371: 3087:
and related graph products, and the fourth strategy is based on lifts.
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with an optimization over all non-empty subsets, we can rewrite it as
6804: 2237: 2226:{\displaystyle \|v\|_{2}=\left(\sum _{i=1}^{n}v_{i}^{2}\right)^{1/2}} 356:{\displaystyle \partial S:=\{\{u,v\}\in E(G)\ :\ u\in S,v\notin S\},} 7502: 7358:
Alon, N.; Capalbo, M. (2002), "Explicit unique-neighbor expanders",
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Proceedings 41st Annual Symposium on Foundations of Computer Science
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Proceedings of the 19th Annual ACM Symposium on Theory of Computing
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Proceedings of the 15th Annual ACM Symposium on Theory of Computing
6913: 6874: 6649: 6490: 5285:{\displaystyle E(S,T)=2|E(G)|+E(S\setminus T,T)+E(S,T\setminus S).} 7671:
Brief introduction in Notices of the American Mathematical Society
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then after the matching with this edge is processed, the input in
4964:. They have also been used in proofs of many important results in 2670:. The upper bound is (asymptotically) achieved for a cycle, where 2018:
as this is the largest eigenvalue corresponding to an eigenvector
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Interlacing families I: Bipartite Ramanujan graphs of all degrees
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of equal size such that every subset of vertices of size at most
3012:{\displaystyle h_{\text{in}}(G)\leq {\sqrt {8(d-\lambda _{2})}}.} 101:
A disconnected graph is not an expander, since the boundary of a
7173:, CBMS Regional Conference Series in Mathematics, vol. 92, 6731:
Interlacing families IV: Bipartite Ramanujan graphs of all sizes
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A simpler proof of a slightly weaker result was given by Puder.
3270:{\displaystyle (x,y)\in \mathbb {Z} _{n}\times \mathbb {Z} _{n}} 651:{\displaystyle \min {|\partial S|}=\min E({S},{\overline {S}})} 2008:{\displaystyle \lambda =\max\{|\lambda _{2}|,|\lambda _{n}|\}} 7693:
Lecture notes from a course on expanders (by Prahladh Harsha)
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Yehudayoff, Amir (2012), "Proving expansion in three steps",
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Goldreich, Oded (2011), "Basic Facts about Expander Graphs",
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getting to infinity, the resulting graph is almost surely an
2458:, there is a relationship between the isoperimetric constant 109:
has the best expansion property, but it has largest possible
3646:-regular graphs for which this bound is tight, satisfying 512:{\displaystyle E(A,B)=\{\{u,v\}\in E(G)\ :\ u\in A,v\in B\}} 7194:
Elementary number theory, group theory and Ramanujan graphs
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Pinkser, M. (1973). "On the Complexity of a Concentrator".
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This definition of the spectral gap is from Section 2.3 in
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Davidoff, Guiliana; Sarnak, Peter; Valette, Alain (2003),
2818:{\displaystyle h(G)\leq {\sqrt {d^{2}-\lambda _{2}^{2}}}.} 1724:{\displaystyle \max _{i\neq 1}|\lambda _{i}|\leq \lambda } 1607:{\displaystyle \max _{i\neq 1}|\lambda _{i}|\leq \lambda } 5947:, then swap the two inputs so that the smaller one is in 4750:. This conjecture was proved in the bipartite setting by 772:{\displaystyle E(S,{\overline {S}})=E({\overline {S}},S)} 5063:-regular graph. The approximation is better the smaller 3891:{\displaystyle \lambda \leq 2{\sqrt {d-1}}+\varepsilon } 3830:{\displaystyle \lambda \leq 2{\sqrt {d-1}}+\varepsilon } 1777:{\displaystyle \max _{i\neq 1}\lambda _{i}\leq \lambda } 688:, the optimization can be equivalently done either over 7254:
Expander families and Cayley graphs: A beginner's guide
3158:{\displaystyle \mathbb {Z} _{n}\times \mathbb {Z} _{n}} 544:
In the equation, the minimum is over all nonempty sets
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Intuitively, an expander graph is a finite, undirected
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Alon, Noga (1986-06-01). "Eigenvalues and expanders".
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roughly containing the smaller half of the inputs and
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are the sparsest examples of highly expanding graphs.
2539: 1930:, and it measures the spectral expansion of the graph 577:, i.e., the set of edges with exactly one endpoint in 5652: 5548: 5304: 5163: 4932:
Expander graphs have found extensive applications in
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Relationships between different expansion properties
5059:is approximately what you would expect in a random 3083:, the third strategy is combinatorial and uses the 6304: 6203: 5706: 5618: 5424: 5284: 4738: 4705: 4641: 4584: 4358: 3974: 3890: 3829: 3739: 3618: 3568: 3484: 3421: 3269: 3207: 3157: 3011: 2939: 2817: 2737: 2713: 2627: 2427: 2267: 2225: 2122: 2007: 1818: 1776: 1723: 1606: 1389: 1350: 1123: 952: 771: 650: 511: 355: 258: 5986:-halving. To see this, notice that if a register 4568:of a graph is formed by replacing each vertex by 2520:. An inequality due to Dodziuk and independently 1446:definition of expansion is possible based on the 662:complete graphs with the same number of vertices 7583:(2008), "Undirected connectivity in log-space", 6753:Reingold, O.; Vadhan, S.; Wigderson, A. (2000). 3757:. This makes them excellent spectral expanders. 3663: 2047: 1953: 1743: 1680: 1563: 1257: 1030: 899: 837: 618: 594: 178: 5871:-halver can be constructed as follows. Take an 6199: 6197: 2828:These inequalities are closely related to the 7232:Bulletin of the American Mathematical Society 5795:and halves the inputs into two disjoint sets 5025:The expander mixing lemma states that for an 2479:in the spectrum of the adjacency operator of 8: 7109:Journal of the American Mathematical Society 6996:"On Eigenvalues and Colorings of Graphs, Ii" 6173: 6171: 6169: 5955:. It is clear that this process consists of 5943:and the smaller input is in the register in 5467:-graph, an independent set has size at most 5037:-graph, for any two subsets of the vertices 4436:are connected if it is possible to get from 3485:{\displaystyle \lambda (G)\leq 5{\sqrt {2}}} 3091:showed that certain graphs constructed from 2150: 2143: 2105: 2098: 2087: 2077: 2002: 1956: 941: 902: 506: 458: 446: 443: 347: 299: 287: 284: 7062:"Coloring Graphs with Sparse Neighborhoods" 6270: 6214: 5930:perfect matchings. The goal is to end with 5750:AKS sorting network and approximate halvers 4877:such that the following holds: For a group 4858:. Alon and Roichman showed that for every 4664:Bilu and Linial conjectured that the bound 4653:, thus giving an efficient construction of 2454:-regular, meaning each vertex is of degree 2026:, it can be equivalently defined using the 7698:Definition and application of spectral gap 7410:, vertex isoperimetry and concentration", 7160:(2011). "9.2. Eigenvalues and Expanders". 7000:Annals of the New York Academy of Sciences 6336: 3619:{\displaystyle \lambda <2{\sqrt {d-1}}} 3056:are all bounded above by the spectral gap 1172:. In a variant of this definition (called 522:the edges between the subsets of vertices 7553: 7501: 7459: 7367: 7331: 7288:(1983), "An O(n log n) sorting network", 7243: 7120: 7079: 6947: 6912: 6873: 6803: 6648: 6585: 6530: 6489: 6393: 6361: 6086:registers so there must be some register 6082:. Altogether, this constitutes more than 5682: 5664: 5651: 5595: 5571: 5547: 5412: 5404: 5396: 5388: 5386: 5364: 5356: 5348: 5340: 5331: 5303: 5220: 5188: 5162: 4723: 4718: 4686: 4677: 4669: 4622: 4613: 4605: 4577: 4460:through the following sequence of moves. 4345: 4340: 4324: 4319: 4309: 4299: 4294: 4279: 4269: 4260: 4247: 4242: 4219: 4207: 4194: 4182: 3940: 3937: 3925: 3869: 3858: 3808: 3797: 3721: 3710: 3704: 3695: 3682: 3676: 3667: 3666: 3654: 3603: 3592: 3538: 3526: 3520: 3475: 3455: 3285: 3261: 3257: 3256: 3246: 3242: 3241: 3220: 3201: 3200: 3192: 3188: 3187: 3178: 3174: 3173: 3170: 3149: 3145: 3144: 3134: 3130: 3129: 3126: 2995: 2977: 2959: 2953: 2925: 2903: 2885: 2861: 2855: 2836:and can be seen as a discrete version of 2804: 2799: 2786: 2780: 2763: 2730: 2706: 2611: 2590: 2563: 2538: 2536: 2407: 2364: 2358: 2259: 2255: 2254: 2245: 2213: 2209: 2198: 2193: 2183: 2172: 2153: 2141: 2108: 2090: 2074: 2050: 2038: 1997: 1991: 1982: 1974: 1968: 1959: 1945: 1810: 1806: 1805: 1796: 1762: 1746: 1740: 1710: 1704: 1695: 1683: 1677: 1593: 1587: 1578: 1566: 1560: 1372: 1366: 1337: 1329: 1322: 1307: 1298: 1295: 1283: 1275: 1267: 1260: 1238: 1232: 1110: 1102: 1095: 1080: 1071: 1068: 1056: 1048: 1040: 1033: 1011: 1005: 936: 926: 921: 913: 905: 884: 876: 867: 840: 819: 750: 728: 714: 635: 627: 609: 598: 597: 592: 420: 273: 245: 237: 230: 219: 216: 204: 196: 188: 181: 160: 7225:"Expander graphs and their applications" 6712: 6710: 6678: 6676: 5978:to be the set of inputs in registers in 5970:to be the set of inputs in registers in 4992:, expander graphs are used to construct 4977: 4706:{\displaystyle O({\sqrt {d\log ^{3}d}})} 4642:{\displaystyle O({\sqrt {d\log ^{3}d}})} 3022:Asymptotically speaking, the quantities 2498:and the first non-trivial eigenvalue is 1479:is the number of edges between vertices 1390:{\displaystyle \partial _{\text{in}}(S)} 6994:Hoffman, A. J.; Howes, Leonard (1970). 6326:of the current article (see p.153, l.5) 6258: 6165: 5739: 5270: 5237: 1661:is useful many contexts, including the 7441:"The PCP theorem by gap amplification" 7252:Krebs, Mike; Shaheen, Anthony (2011), 7164:(3rd ed.). John Wiley & Sons. 1188:is replaced by the set of vertices in 7676:Introductory paper by Michael Nielsen 6748: 6746: 6744: 4985: 3782:, are almost Ramanujan. That is, for 3770:In 1985, Alon, conjectured that most 2268:{\displaystyle v\in \mathbb {R} ^{n}} 1819:{\displaystyle u\in \mathbb {R} ^{n}} 1791:is regular, the uniform distribution 709:or over any non-empty subset, since 27:Sparse graph with strong connectivity 7: 6975:(2). Wiley Online Library: 271–284. 6965:"Random Cayley graphs and Expanders" 6506:Hoory, Linial & Wigderson (2006) 6430:Hoory, Linial & Wigderson (2006) 6418:Hoory, Linial & Wigderson (2006) 6406:Hoory, Linial & Wigderson (2006) 6284:Hoory, Linial & Wigderson (2006) 6248:Hoory, Linial & Wigderson (2006) 6227:Hoory, Linial & Wigderson (2006) 6190:Hoory, Linial & Wigderson (2006) 6178:Hoory, Linial & Wigderson (2006) 5862:Ajtai, Komlós & Szemerédi (1983) 5736:Ajtai, Komlós & Szemerédi (1987) 4958:Ajtai, Komlós & Szemerédi (1983) 4746:, which would be optimal due to the 7197:, LMS student texts, vol. 55, 6866:Ramanujan Graphs in Polynomial Time 6761:. IEEE Comput. Soc. pp. 3–13. 5146:denote the number of edges between 7020:10.1111/j.1749-6632.1970.tb56474.x 6305:Bobkov, Houdré & Tetali (2000) 6204:Bobkov, Houdré & Tetali (2000) 4924:Applications and useful properties 3277:, its eight adjacent vertices are 2755:. A better bound is given in as 1369: 1304: 1077: 841: 674:but the edge expansion will be 1. 603: 275: 224: 25: 7122:10.1090/S0894-0347-1989-0965008-X 5071:-regular graph, as well as in an 4773:-lifts by Hall, Puder and Sawin. 4073:-graph, then the zig-zag product 3845:-regular graphs" by showing that 3778:vertices, for sufficiently large 6969:Random Structures and Algorithms 6303:See Theorem 1 and p.156, l.1 in 5783:-halver takes as input a length 4396:refers to an original vertex of 790:because of the normalization by 7067:Journal of Combinatorial Theory 6963:Alon, N.; Roichman, Y. (1994). 4966:computational complexity theory 4885:, consider the Cayley graph on 3626:, there are only finitely many 1405:, i.e., the set of vertices in 1154:, i.e., the set of vertices in 5879:bipartite expander with parts 5690: 5676: 5603: 5583: 5558: 5552: 5413: 5405: 5397: 5389: 5365: 5357: 5349: 5341: 5325: 5313: 5276: 5258: 5249: 5231: 5221: 5217: 5214: 5202: 5196: 5189: 5179: 5167: 5051:, the number of edges between 5001:2006 survey of expander graphs 4906:randomly chosen elements from 4739:{\displaystyle 2{\sqrt {d-1}}} 4700: 4674: 4636: 4610: 4498:Jump across clouds using edge 4306: 4281: 4253: 4229: 4213: 4187: 4111:has the following properties. 3711: 3696: 3683: 3668: 3563: 3557: 3466: 3460: 3450:has second-largest eigenvalue 3413: 3410: 3395: 3380: 3374: 3353: 3347: 3338: 3323: 3314: 3308: 3287: 3234: 3222: 3001: 2982: 2971: 2965: 2909: 2890: 2873: 2867: 2774: 2768: 2617: 2598: 2584: 2578: 2569: 2550: 2419: 2413: 2391: 2385: 2376: 2370: 1998: 1983: 1975: 1960: 1711: 1696: 1594: 1579: 1544:More formally, we refer to an 1409:with at least one neighbor in 1384: 1378: 1338: 1330: 1323: 1319: 1313: 1299: 1276: 1268: 1250: 1244: 1168:with at least one neighbor in 1111: 1103: 1096: 1092: 1086: 1072: 1049: 1041: 1023: 1017: 937: 922: 914: 906: 894: 873: 862: 856: 830: 824: 766: 747: 738: 719: 645: 624: 610: 599: 473: 467: 437: 425: 314: 308: 246: 238: 231: 220: 197: 189: 171: 165: 1: 7245:10.1090/S0273-0979-06-01126-8 7175:American Mathematical Society 6636:Israel Journal of Mathematics 6102:such that the final input of 5926:and decompose the edges into 4836:with high probability, where 4657:-regular expanders for every 366:which can also be written as 46:properties, quantified using 7564:10.1007/978-3-642-22670-0_30 6052:are connected with at least 4819:for all subsets of vertices 4376:is blown up to a "cloud" of 931: 889: 755: 733: 640: 7256:, Oxford University Press, 7105:"Diameters and eigenvalues" 6114:, while the final input of 6094:connected to some register 5803:such that for each integer 4843:is a constant depending on 3509:theorem of Alon and Boppana 1205:vertex isoperimetric number 970:vertex isoperimetric number 779:. The same is not true for 7729: 7658:(published 13 August 2018) 7199:Cambridge University Press 5922:and half of the inputs in 5753: 5722: 5018: 4014: 4004: 4003:Ramanujan graphs based on 3500: 3432:Then the following holds: 3114:, one considers the graph 1668:Spectral expansion can be 7533:10.1137/S0097539794268765 7521:SIAM Journal on Computing 7378:10.1109/SFCS.2002.1181884 7326:, ACM, pp. 132–140, 7169:Chung, Fan R. K. (1997), 6939:SIAM Journal on Computing 6923:10.1016/j.aim.2017.10.042 6864:Michael B. Cohen (2016). 6835:10.1007/s00493-006-0029-7 6659:10.1007/s11856-023-2497-5 6604:10.1007/s00222-014-0560-x 6549:10.1007/s00222-014-0560-x 6215:Alon & Capalbo (2002) 6150:Superstrong approximation 6002:are connected by an edge 5951:and the larger one is in 3999:, gave a construction of 3511:, all sufficiently large 1174:unique neighbor expansion 7650:Hartnett, Kevin (2018), 7402:Bobkov, S.; Houdré, C.; 7162:The Probabilistic Method 7103:Chung, F. R. K. (1989). 6767:10.1109/sfcs.2000.892006 6573:Inventiones Mathematicae 6519:Inventiones Mathematicae 5073:Erdős–Rényi random graph 4910:. Then, in the limit of 4777:Randomized constructions 3515:-regular graphs satisfy 2321:of the adjacency matrix 2303:Markov transition matrix 1633:. The bound given by an 1507:real-valued eigenvalues 7629:10.1145/2421096.2421115 7599:10.1145/1391289.1391291 7490:Trans. Amer. Math. Soc. 7470:10.1145/1236457.1236459 6900:Advances in Mathematics 6271:Alon & Spencer 2011 5829:smallest inputs are in 4950:pseudorandom generators 3106:constructions based on 1859:stationary distribution 152:vertices is defined as 7081:10.1006/jctb.1999.1910 6981:10.1002/rsa.3240050203 6140:Algebraic connectivity 5841:largest inputs are in 5725:Expander walk sampling 5719:Expander walk sampling 5708: 5620: 5426: 5286: 5075:with edge probability 4942:error correcting codes 4740: 4707: 4643: 4586: 4360: 3976: 3892: 3831: 3741: 3620: 3570: 3494: 3486: 3423: 3271: 3209: 3159: 3081:additive combinatorics 3013: 2941: 2819: 2739: 2715: 2629: 2429: 2269: 2227: 2188: 2124: 2009: 1820: 1778: 1725: 1608: 1391: 1352: 1125: 954: 800:. If we want to write 773: 652: 513: 357: 260: 68:error-correcting codes 7424:10.1007/s004930070018 7298:10.1145/800061.808726 7171:Spectral Graph Theory 7147:Textbooks and surveys 6314:there corresponds to 6155:Spectral graph theory 6010:is less than that of 5709: 5621: 5427: 5287: 5021:Expander mixing lemma 5015:Expander mixing lemma 4741: 4708: 4644: 4587: 4361: 3977: 3893: 3832: 3742: 3621: 3571: 3487: 3434: 3424: 3272: 3210: 3160: 3099:Margulis–Gabber–Galil 3014: 2942: 2820: 2740: 2716: 2630: 2430: 2270: 2228: 2168: 2125: 2010: 1821: 1779: 1726: 1663:expander mixing lemma 1609: 1552:-regular graph with 1392: 1353: 1126: 955: 774: 653: 514: 358: 261: 7439:Dinur, Irit (2007), 7054:Krivelevich, Michael 6884:10.1109/FOCS.2016.37 5650: 5546: 5302: 5161: 4717: 4668: 4604: 4576: 4181: 3924: 3857: 3796: 3653: 3591: 3519: 3454: 3284: 3219: 3169: 3125: 3121:with the vertex set 2952: 2854: 2838:Cheeger's inequality 2762: 2738:{\displaystyle \pi } 2729: 2714:{\displaystyle \pi } 2705: 2535: 2442:Cheeger inequalities 2357: 2317:, one considers the 2244: 2140: 2037: 1944: 1795: 1739: 1676: 1559: 1365: 1231: 1004: 818: 713: 591: 419: 272: 159: 127:isoperimetric number 98:, as defined below. 66:, and the theory of 7644:Recent Applications 7333:10.1145/28395.28410 7012:1970NYASA.175..238H 6596:2015InMat.201..845P 6541:2015InMat.201..845P 6416:Definition 5.11 of 6225:cf. Section 2.3 in 5435:Many properties of 5131:More formally, let 4713:can be improved to 4491:, using an edge of 4350: 4329: 4304: 4252: 3774:-regular graphs on 3215:: For every vertex 2842:Riemannian geometry 2809: 2509:is connected, then 2203: 1906:of the vertices of 1865:. That is, we have 103:connected component 62:, design of robust 7681:2016-08-17 at the 7586:Journal of the ACM 7448:Journal of the ACM 6455:10.1007/BF02579166 6392:see, e.g., p.9 of 6372:10.1007/BF02579382 6188:Definition 2.1 in 5704: 5616: 5422: 5282: 4748:Alon-Boppana bound 4736: 4703: 4639: 4596:showed that every 4582: 4356: 4336: 4315: 4290: 4238: 3972: 3888: 3827: 3737: 3694: 3616: 3566: 3482: 3419: 3267: 3205: 3155: 3009: 2937: 2815: 2795: 2735: 2711: 2625: 2548: 2487:-regular graph is 2425: 2265: 2223: 2189: 2120: 2073: 2005: 1816: 1774: 1757: 1721: 1694: 1604: 1577: 1427:Spectral expansion 1387: 1348: 1294: 1121: 1067: 950: 866: 769: 648: 509: 408:the complement of 353: 256: 215: 96:spectral expanders 7573:978-3-642-22669-4 7387:978-0-7695-1822-0 7343:978-0-89791-221-1 7307:978-0-89791-099-6 7271:Research articles 7263:978-0-19-976711-3 7208:978-0-521-53143-6 7184:978-0-8218-0315-8 6726:Nikhil Srivastava 6692:Nikhil Srivastava 6337:Yehudayoff (2012) 5694: 5645:-graph is at most 5607: 5417: 5373: 5005:extremal problems 4962:computer networks 4734: 4698: 4634: 4585:{\displaystyle r} 4548:using an edge of 4351: 4277: 4227: 3963: 3951: 3905:with probability 3880: 3819: 3732: 3662: 3614: 3549: 3480: 3093:finite geometries 3004: 2962: 2912: 2864: 2810: 2620: 2547: 2410: 2367: 2115: 2046: 2028:Rayleigh quotient 1920:is defined to be 1742: 1679: 1672:, as above, with 1562: 1375: 1343: 1310: 1291: 1256: 1241: 1116: 1083: 1064: 1029: 1014: 945: 934: 892: 836: 758: 736: 643: 484: 478: 325: 319: 251: 212: 177: 64:computer networks 60:complexity theory 16:(Redirected from 7720: 7659: 7639: 7609: 7576: 7557: 7547: 7535: 7527:(4): 1203–1220, 7514: 7505: 7480: 7463: 7445: 7434: 7398: 7371: 7354: 7335: 7318: 7292:, pp. 1–9, 7266: 7248: 7247: 7229: 7211: 7187: 7165: 7158:Spencer, Joel H. 7135: 7134: 7124: 7100: 7094: 7093: 7083: 7046: 7040: 7039: 6991: 6985: 6984: 6960: 6954: 6953: 6951: 6933: 6927: 6926: 6916: 6894: 6888: 6887: 6877: 6861: 6855: 6854: 6816: 6810: 6809: 6807: 6795: 6789: 6788: 6750: 6739: 6738: 6736: 6714: 6705: 6704: 6702: 6680: 6671: 6670: 6652: 6630: 6624: 6623: 6589: 6567: 6561: 6560: 6534: 6514: 6508: 6504:Theorem 7.10 of 6502: 6496: 6495: 6493: 6481: 6475: 6474: 6438: 6432: 6428:Theorem 5.12 of 6426: 6420: 6414: 6408: 6402: 6396: 6394:Goldreich (2011) 6390: 6384: 6383: 6365: 6345: 6339: 6333: 6327: 6325: 6313: 6301: 6295: 6292: 6286: 6280: 6274: 6268: 6262: 6256: 6250: 6244: 6238: 6235: 6229: 6223: 6217: 6212: 6206: 6201: 6192: 6186: 6180: 6175: 6129: 6125: 6121: 6117: 6113: 6105: 6101: 6097: 6093: 6089: 6085: 6081: 6077: 6073: 6071: 6070: 6065: 6062: 6051: 6047: 6043: 6035: 6031: 6030: 6029: 6025: 6013: 6009: 6005: 6001: 5997: 5993: 5989: 5985: 5981: 5977: 5973: 5969: 5965: 5959:parallel steps. 5958: 5954: 5950: 5946: 5942: 5937: 5933: 5929: 5925: 5921: 5913: 5912: 5910: 5909: 5904: 5901: 5890: 5886: 5882: 5878: 5874: 5870: 5867: 5856: 5852: 5848: 5844: 5840: 5836: 5832: 5828: 5824: 5820: 5819: 5818: 5814: 5802: 5798: 5794: 5786: 5782: 5778: 5771: 5713: 5711: 5710: 5705: 5700: 5696: 5695: 5693: 5686: 5665: 5644: 5625: 5623: 5622: 5617: 5612: 5608: 5606: 5599: 5572: 5540: 5539: 5538: 5534: 5521: 5515: 5514: 5510: 5502: 5494: 5489:chromatic number 5483: 5482: 5481: 5475: 5466: 5446: 5431: 5429: 5428: 5423: 5418: 5416: 5408: 5400: 5392: 5387: 5379: 5375: 5374: 5369: 5368: 5360: 5352: 5344: 5332: 5291: 5289: 5288: 5283: 5224: 5192: 5153: 5149: 5145: 5127: 5123: 5119: 5117: 5111: 5105: 5104: 5098: 5090: 5089: 5088: 5082: 5070: 5067:is. In a random 5066: 5062: 5058: 5054: 5050: 5036: 4954:sorting networks 4934:computer science 4919: 4913: 4909: 4905: 4888: 4884: 4880: 4876: 4866:, there is some 4865: 4857: 4846: 4842: 4835: 4826: 4818: 4816: 4806: 4789: 4785: 4772: 4767:Ramanujan graphs 4745: 4743: 4742: 4737: 4735: 4724: 4712: 4710: 4709: 4704: 4699: 4691: 4690: 4678: 4660: 4656: 4648: 4646: 4645: 4640: 4635: 4627: 4626: 4614: 4599: 4591: 4589: 4588: 4583: 4571: 4565: 4551: 4547: 4535: 4517: 4505: 4501: 4494: 4490: 4478: 4459: 4447: 4435: 4423: 4412:. Two vertices, 4411: 4407: 4403: 4399: 4395: 4391: 4379: 4375: 4365: 4363: 4362: 4357: 4352: 4349: 4344: 4328: 4323: 4314: 4313: 4303: 4298: 4280: 4278: 4270: 4265: 4264: 4251: 4246: 4228: 4220: 4212: 4211: 4199: 4198: 4169: 4145: 4130: 4122: 4110: 4106: 4082: 4072: 4056: 4052: 4036: 3981: 3979: 3978: 3973: 3968: 3964: 3959: 3952: 3941: 3938: 3916: 3904: 3897: 3895: 3894: 3889: 3881: 3870: 3850: 3844: 3836: 3834: 3833: 3828: 3820: 3809: 3788: 3781: 3777: 3773: 3763:, Phillips, and 3756: 3746: 3744: 3743: 3738: 3733: 3722: 3714: 3709: 3708: 3699: 3693: 3686: 3681: 3680: 3671: 3645: 3640:Ramanujan graphs 3637: 3625: 3623: 3622: 3617: 3615: 3604: 3586: 3582: 3575: 3573: 3572: 3567: 3550: 3539: 3531: 3530: 3514: 3497:Ramanujan graphs 3491: 3489: 3488: 3483: 3481: 3476: 3449: 3442: 3428: 3426: 3425: 3420: 3276: 3274: 3273: 3268: 3266: 3265: 3260: 3251: 3250: 3245: 3214: 3212: 3211: 3206: 3204: 3196: 3191: 3183: 3182: 3177: 3164: 3162: 3161: 3156: 3154: 3153: 3148: 3139: 3138: 3133: 3120: 3113: 3070: 3055: 3046: 3037: 3036: 3035: 3029: 3018: 3016: 3015: 3010: 3005: 3000: 2999: 2978: 2964: 2963: 2960: 2946: 2944: 2943: 2938: 2930: 2929: 2924: 2920: 2913: 2908: 2907: 2886: 2866: 2865: 2862: 2824: 2822: 2821: 2816: 2811: 2808: 2803: 2791: 2790: 2781: 2754: 2744: 2742: 2741: 2736: 2720: 2718: 2717: 2712: 2691: 2669: 2658: 2647: 2634: 2632: 2631: 2626: 2621: 2616: 2615: 2591: 2568: 2567: 2549: 2540: 2519: 2508: 2504: 2497: 2486: 2482: 2478: 2468: 2457: 2453: 2449: 2434: 2432: 2431: 2426: 2412: 2411: 2408: 2369: 2368: 2365: 2349: 2345: 2333: 2324: 2311:Laplacian matrix 2308: 2300: 2296: 2294: 2293: 2288: 2285: 2274: 2272: 2271: 2266: 2264: 2263: 2258: 2232: 2230: 2229: 2224: 2222: 2221: 2217: 2208: 2204: 2202: 2197: 2187: 2182: 2158: 2157: 2129: 2127: 2126: 2121: 2116: 2114: 2113: 2112: 2096: 2095: 2094: 2075: 2072: 2025: 2014: 2012: 2011: 2006: 2001: 1996: 1995: 1986: 1978: 1973: 1972: 1963: 1933: 1929: 1919: 1909: 1901: 1897: 1887:with eigenvalue 1886: 1878: 1874: 1864: 1856: 1846: 1845: 1844: 1838: 1825: 1823: 1822: 1817: 1815: 1814: 1809: 1790: 1783: 1781: 1780: 1775: 1767: 1766: 1756: 1730: 1728: 1727: 1722: 1714: 1709: 1708: 1699: 1693: 1660: 1653: 1644: 1628: 1613: 1611: 1610: 1605: 1597: 1592: 1591: 1582: 1576: 1551: 1547: 1540: 1536: 1523: 1506: 1502: 1497:spectral theorem 1490: 1486: 1482: 1478: 1471: 1467: 1452:adjacency matrix 1444:linear algebraic 1439: 1434: 1422: 1408: 1404: 1396: 1394: 1393: 1388: 1377: 1376: 1373: 1357: 1355: 1354: 1349: 1344: 1342: 1341: 1333: 1327: 1326: 1312: 1311: 1308: 1302: 1296: 1293: 1292: 1284: 1279: 1271: 1243: 1242: 1239: 1223: 1219: 1199: 1196:one neighbor in 1191: 1187: 1171: 1167: 1153: 1145: 1130: 1128: 1127: 1122: 1117: 1115: 1114: 1106: 1100: 1099: 1085: 1084: 1081: 1075: 1069: 1066: 1065: 1057: 1052: 1044: 1016: 1015: 1012: 996: 987:vertex expansion 984: 964:Vertex expansion 959: 957: 956: 951: 946: 944: 940: 935: 927: 925: 917: 909: 897: 893: 885: 880: 868: 865: 810: 799: 797: 789: 778: 776: 775: 770: 759: 751: 737: 729: 708: 707: 706: 702: 695: 687: 685: 673: 669: 665: 657: 655: 654: 649: 644: 636: 631: 614: 613: 602: 580: 576: 568: 561: 560: 559: 555: 547: 540: 518: 516: 515: 510: 482: 476: 411: 407: 394: 387: 385: 362: 360: 359: 354: 323: 317: 265: 263: 262: 257: 252: 250: 249: 241: 235: 234: 223: 217: 214: 213: 205: 200: 192: 151: 147: 143: 131:Cheeger constant 92:vertex expanders 42:that has strong 21: 7728: 7727: 7723: 7722: 7721: 7719: 7718: 7717: 7703: 7702: 7683:Wayback Machine 7667: 7662: 7656:Quanta Magazine 7649: 7646: 7616:ACM SIGACT News 7612: 7579: 7574: 7555:10.1.1.231.1388 7545: 7538: 7518: 7503:10.2307/1999107 7484: 7461:10.1.1.103.2644 7443: 7438: 7409: 7401: 7388: 7357: 7344: 7321: 7308: 7276: 7273: 7264: 7251: 7227: 7215:Hoory, Shlomo; 7214: 7209: 7190: 7185: 7168: 7152: 7149: 7143: 7138: 7102: 7101: 7097: 7048: 7047: 7043: 6993: 6992: 6988: 6962: 6961: 6957: 6949:10.1.1.393.1430 6935: 6934: 6930: 6896: 6895: 6891: 6863: 6862: 6858: 6818: 6817: 6813: 6797: 6796: 6792: 6777: 6752: 6751: 6742: 6734: 6722:Daniel Spielman 6716: 6715: 6708: 6700: 6688:Daniel Spielman 6682: 6681: 6674: 6632: 6631: 6627: 6569: 6568: 6564: 6516: 6515: 6511: 6503: 6499: 6483: 6482: 6478: 6440: 6439: 6435: 6427: 6423: 6415: 6411: 6404:Theorem 2.7 of 6403: 6399: 6391: 6387: 6363:10.1.1.300.5945 6347: 6346: 6342: 6334: 6330: 6323: 6315: 6312: 6308: 6302: 6298: 6293: 6289: 6282:Theorem 2.4 in 6281: 6277: 6269: 6265: 6257: 6253: 6245: 6241: 6236: 6232: 6224: 6220: 6213: 6209: 6202: 6195: 6187: 6183: 6176: 6167: 6163: 6145:Zig-zag product 6136: 6127: 6123: 6119: 6115: 6107: 6103: 6099: 6095: 6091: 6087: 6083: 6079: 6066: 6063: 6057: 6056: 6054: 6053: 6049: 6045: 6037: 6033: 6032:that more than 6027: 6021: 6020: 6015: 6011: 6007: 6003: 5999: 5995: 5991: 5987: 5983: 5979: 5975: 5971: 5967: 5963: 5956: 5952: 5948: 5944: 5940: 5935: 5931: 5927: 5923: 5919: 5905: 5902: 5896: 5895: 5893: 5892: 5888: 5884: 5880: 5876: 5875:vertex, degree 5872: 5868: 5865: 5854: 5850: 5846: 5842: 5838: 5834: 5830: 5826: 5822: 5816: 5810: 5809: 5804: 5800: 5796: 5788: 5787:permutation of 5784: 5780: 5776: 5762: 5758: 5756:Sorting network 5752: 5744:derandomization 5727: 5721: 5669: 5657: 5653: 5648: 5647: 5634: 5576: 5567: 5544: 5543: 5536: 5529: 5528: 5523: 5512: 5506: 5505: 5504: 5496: 5492: 5477: 5470: 5469: 5468: 5456: 5453:independent set 5436: 5333: 5309: 5305: 5300: 5299: 5159: 5158: 5151: 5147: 5132: 5125: 5121: 5113: 5112:| • | 5107: 5100: 5094: 5093: 5092: 5084: 5078: 5077: 5076: 5068: 5064: 5060: 5056: 5052: 5038: 5026: 5023: 5017: 4978:Reingold (2008) 4936:, in designing 4926: 4915: 4911: 4907: 4901: 4890: 4886: 4882: 4878: 4867: 4859: 4848: 4844: 4841: 4837: 4832: 4822: 4820: 4812: 4797: 4795: 4792:bipartite graph 4787: 4783: 4779: 4770: 4715: 4714: 4682: 4666: 4665: 4658: 4654: 4651:polynomial time 4618: 4602: 4601: 4597: 4574: 4573: 4569: 4563: 4559: 4549: 4537: 4525: 4507: 4503: 4499: 4492: 4480: 4468: 4449: 4437: 4425: 4413: 4409: 4405: 4401: 4397: 4393: 4381: 4377: 4373: 4305: 4256: 4203: 4190: 4179: 4178: 4168: 4164: 4160: 4156: 4149: 4143: 4139: 4132: 4128: 4124: 4120: 4116: 4108: 4104: 4100: 4084: 4074: 4070: 4058: 4054: 4050: 4038: 4034: 4019: 4017:Zig-zag product 4013: 4011:Zig-Zag product 3939: 3933: 3922: 3921: 3906: 3899: 3855: 3854: 3851:-regular graphs 3848: 3842: 3794: 3793: 3789:, they satisfy 3783: 3779: 3775: 3771: 3755: 3751: 3700: 3672: 3651: 3650: 3643: 3627: 3589: 3588: 3584: 3581: 3577: 3522: 3517: 3516: 3512: 3505: 3503:Ramanujan graph 3499: 3452: 3451: 3448: 3444: 3440: 3282: 3281: 3255: 3240: 3217: 3216: 3172: 3167: 3166: 3143: 3128: 3123: 3122: 3119: 3115: 3111: 3101: 3077: 3068: 3057: 3054: 3048: 3045: 3039: 3031: 3025: 3024: 3023: 2991: 2955: 2950: 2949: 2899: 2884: 2880: 2879: 2857: 2852: 2851: 2782: 2760: 2759: 2727: 2726: 2703: 2702: 2700: 2693: 2680: 2671: 2667: 2660: 2649: 2646: 2642: 2607: 2559: 2533: 2532: 2514: 2510: 2506: 2503: 2499: 2492: 2488: 2484: 2480: 2477: 2470: 2459: 2455: 2451: 2447: 2444: 2403: 2360: 2355: 2354: 2347: 2346:-regular graph 2343: 2340: 2326: 2322: 2319:singular values 2315:directed graphs 2306: 2301:, which is the 2289: 2286: 2283: 2282: 2280: 2279: 2253: 2242: 2241: 2167: 2163: 2162: 2149: 2138: 2137: 2104: 2097: 2086: 2076: 2035: 2034: 2023: 1987: 1964: 1942: 1941: 1931: 1928: 1921: 1917: 1907: 1899: 1892: 1888: 1884: 1876: 1866: 1862: 1848: 1840: 1836: 1835: 1832: 1827: 1804: 1793: 1792: 1788: 1758: 1737: 1736: 1731:, or it can be 1700: 1674: 1673: 1655: 1652: 1646: 1634: 1618: 1583: 1557: 1556: 1549: 1545: 1538: 1537:if and only if 1531: 1525: 1522: 1516: 1512: 1508: 1504: 1500: 1488: 1484: 1480: 1477: 1473: 1469: 1454: 1437: 1432: 1429: 1410: 1406: 1402: 1368: 1363: 1362: 1328: 1303: 1297: 1234: 1229: 1228: 1221: 1213: 1207: 1197: 1189: 1181: 1177: 1169: 1155: 1151: 1139: 1135: 1101: 1076: 1070: 1007: 1002: 1001: 994: 978: 972: 966: 898: 869: 816: 815: 801: 793: 791: 780: 711: 710: 704: 698: 697: 691: 689: 680: 678: 677:Notice that in 671: 667: 663: 589: 588: 578: 574: 563: 557: 551: 550: 549: 545: 523: 417: 416: 409: 390: 389: 381: 367: 270: 269: 236: 218: 157: 156: 149: 145: 134: 119: 76: 28: 23: 22: 18:Expander graphs 15: 12: 11: 5: 7726: 7724: 7716: 7715: 7713:Graph families 7705: 7704: 7701: 7700: 7695: 7690: 7685: 7673: 7666: 7665:External links 7663: 7661: 7660: 7645: 7642: 7641: 7640: 7610: 7581:Reingold, Omer 7577: 7572: 7536: 7516: 7496:(2): 787–794, 7486:Dodziuk, Jozef 7482: 7436: 7418:(2): 153–172, 7407: 7399: 7386: 7369:10.1.1.103.967 7362:, p. 73, 7355: 7342: 7319: 7306: 7272: 7269: 7268: 7267: 7262: 7249: 7238:(4): 439–561, 7234:, New Series, 7221:Wigderson, Avi 7217:Linial, Nathan 7212: 7207: 7188: 7183: 7166: 7148: 7145: 7144: 7142: 7139: 7137: 7136: 7115:(2): 187–196. 7095: 7060:(1999-09-01). 7058:Sudakov, Benny 7041: 7006:(1): 238–242. 6986: 6955: 6928: 6889: 6856: 6829:(5): 495–519. 6811: 6790: 6775: 6740: 6706: 6672: 6625: 6580:(3): 845–908. 6562: 6525:(3): 845–908. 6509: 6497: 6476: 6433: 6421: 6409: 6397: 6385: 6356:(3): 207–219. 6340: 6328: 6321: 6310: 6296: 6287: 6275: 6263: 6251: 6239: 6230: 6218: 6207: 6193: 6181: 6164: 6162: 6159: 6158: 6157: 6152: 6147: 6142: 6135: 6132: 6036:of the inputs 5754:Main article: 5751: 5748: 5740:Gillman (1998) 5731:Chernoff bound 5723:Main article: 5720: 5717: 5716: 5715: 5703: 5699: 5692: 5689: 5685: 5681: 5678: 5675: 5672: 5668: 5663: 5660: 5656: 5627: 5615: 5611: 5605: 5602: 5598: 5594: 5591: 5588: 5585: 5582: 5579: 5575: 5570: 5566: 5563: 5560: 5557: 5554: 5551: 5485: 5433: 5432: 5421: 5415: 5411: 5407: 5403: 5399: 5395: 5391: 5385: 5382: 5378: 5372: 5367: 5363: 5359: 5355: 5351: 5347: 5343: 5339: 5336: 5330: 5327: 5324: 5321: 5318: 5315: 5312: 5308: 5293: 5292: 5281: 5278: 5275: 5272: 5269: 5266: 5263: 5260: 5257: 5254: 5251: 5248: 5245: 5242: 5239: 5236: 5233: 5230: 5227: 5223: 5219: 5216: 5213: 5210: 5207: 5204: 5201: 5198: 5195: 5191: 5187: 5184: 5181: 5178: 5175: 5172: 5169: 5166: 5120:edges between 5019:Main article: 5016: 5013: 4994:hash functions 4925: 4922: 4899: 4839: 4830: 4778: 4775: 4733: 4730: 4727: 4722: 4702: 4697: 4694: 4689: 4685: 4681: 4676: 4673: 4638: 4633: 4630: 4625: 4621: 4617: 4612: 4609: 4581: 4558: 4555: 4554: 4553: 4519: 4496: 4404:refers to the 4367: 4366: 4355: 4348: 4343: 4339: 4335: 4332: 4327: 4322: 4318: 4312: 4308: 4302: 4297: 4293: 4289: 4286: 4283: 4276: 4273: 4268: 4263: 4259: 4255: 4250: 4245: 4241: 4237: 4234: 4231: 4226: 4223: 4218: 4215: 4210: 4206: 4202: 4197: 4193: 4189: 4186: 4174:Specifically, 4172: 4171: 4166: 4162: 4158: 4154: 4147: 4141: 4137: 4126: 4118: 4102: 4098: 4068: 4048: 4015:Main article: 4012: 4009: 3983: 3982: 3971: 3967: 3962: 3958: 3955: 3950: 3947: 3944: 3936: 3932: 3929: 3887: 3884: 3879: 3876: 3873: 3868: 3865: 3862: 3839: 3838: 3826: 3823: 3818: 3815: 3812: 3807: 3804: 3801: 3753: 3748: 3747: 3736: 3731: 3728: 3725: 3720: 3717: 3713: 3707: 3703: 3698: 3692: 3689: 3685: 3679: 3675: 3670: 3665: 3661: 3658: 3613: 3610: 3607: 3602: 3599: 3596: 3579: 3565: 3562: 3559: 3556: 3553: 3548: 3545: 3542: 3537: 3534: 3529: 3525: 3501:Main article: 3498: 3495: 3479: 3474: 3471: 3468: 3465: 3462: 3459: 3446: 3430: 3429: 3418: 3415: 3412: 3409: 3406: 3403: 3400: 3397: 3394: 3391: 3388: 3385: 3382: 3379: 3376: 3373: 3370: 3367: 3364: 3361: 3358: 3355: 3352: 3349: 3346: 3343: 3340: 3337: 3334: 3331: 3328: 3325: 3322: 3319: 3316: 3313: 3310: 3307: 3304: 3301: 3298: 3295: 3292: 3289: 3264: 3259: 3254: 3249: 3244: 3239: 3236: 3233: 3230: 3227: 3224: 3203: 3199: 3195: 3190: 3186: 3181: 3176: 3152: 3147: 3142: 3137: 3132: 3117: 3100: 3097: 3076: 3073: 3066: 3052: 3043: 3020: 3019: 3008: 3003: 2998: 2994: 2990: 2987: 2984: 2981: 2976: 2973: 2970: 2967: 2958: 2947: 2936: 2933: 2928: 2923: 2919: 2916: 2911: 2906: 2902: 2898: 2895: 2892: 2889: 2883: 2878: 2875: 2872: 2869: 2860: 2826: 2825: 2814: 2807: 2802: 2798: 2794: 2789: 2785: 2779: 2776: 2773: 2770: 2767: 2734: 2710: 2698: 2678: 2665: 2644: 2636: 2635: 2624: 2619: 2614: 2610: 2606: 2603: 2600: 2597: 2594: 2589: 2586: 2583: 2580: 2577: 2574: 2571: 2566: 2562: 2558: 2555: 2552: 2546: 2543: 2512: 2501: 2490: 2475: 2443: 2440: 2436: 2435: 2424: 2421: 2418: 2415: 2406: 2402: 2399: 2396: 2393: 2390: 2387: 2384: 2381: 2378: 2375: 2372: 2363: 2339: 2336: 2262: 2257: 2252: 2249: 2240:of the vector 2234: 2233: 2220: 2216: 2212: 2207: 2201: 2196: 2192: 2186: 2181: 2178: 2175: 2171: 2166: 2161: 2156: 2152: 2148: 2145: 2131: 2130: 2119: 2111: 2107: 2103: 2100: 2093: 2089: 2085: 2082: 2079: 2071: 2068: 2065: 2062: 2059: 2056: 2053: 2049: 2045: 2042: 2016: 2015: 2004: 2000: 1994: 1990: 1985: 1981: 1977: 1971: 1967: 1962: 1958: 1955: 1952: 1949: 1926: 1890: 1830: 1813: 1808: 1803: 1800: 1773: 1770: 1765: 1761: 1755: 1752: 1749: 1745: 1720: 1717: 1713: 1707: 1703: 1698: 1692: 1689: 1686: 1682: 1648: 1615: 1614: 1603: 1600: 1596: 1590: 1586: 1581: 1575: 1572: 1569: 1565: 1541:is bipartite. 1527: 1518: 1514: 1510: 1475: 1428: 1425: 1399:inner boundary 1386: 1383: 1380: 1371: 1359: 1358: 1347: 1340: 1336: 1332: 1325: 1321: 1318: 1315: 1306: 1301: 1290: 1287: 1282: 1278: 1274: 1270: 1266: 1263: 1259: 1255: 1252: 1249: 1246: 1237: 1224:is defined as 1211: 1179: 1148:outer boundary 1137: 1132: 1131: 1120: 1113: 1109: 1105: 1098: 1094: 1091: 1088: 1079: 1074: 1063: 1060: 1055: 1051: 1047: 1043: 1039: 1036: 1032: 1028: 1025: 1022: 1019: 1010: 997:is defined as 976: 965: 962: 961: 960: 949: 943: 939: 933: 930: 924: 920: 916: 912: 908: 904: 901: 896: 891: 888: 883: 879: 875: 872: 864: 861: 858: 855: 852: 849: 846: 843: 839: 835: 832: 829: 826: 823: 768: 765: 762: 757: 754: 749: 746: 743: 740: 735: 732: 727: 724: 721: 718: 659: 658: 647: 642: 639: 634: 630: 626: 623: 620: 617: 612: 608: 605: 601: 596: 584:Intuitively, 520: 519: 508: 505: 502: 499: 496: 493: 490: 487: 481: 475: 472: 469: 466: 463: 460: 457: 454: 451: 448: 445: 442: 439: 436: 433: 430: 427: 424: 364: 363: 352: 349: 346: 343: 340: 337: 334: 331: 328: 322: 316: 313: 310: 307: 304: 301: 298: 295: 292: 289: 286: 283: 280: 277: 266: 255: 248: 244: 240: 233: 229: 226: 222: 211: 208: 203: 199: 195: 191: 187: 184: 180: 176: 173: 170: 167: 164: 123:edge expansion 118: 117:Edge expansion 115: 107:complete graph 88:edge expanders 75: 72: 36:expander graph 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 7725: 7714: 7711: 7710: 7708: 7699: 7696: 7694: 7691: 7689: 7686: 7684: 7680: 7677: 7674: 7672: 7669: 7668: 7664: 7657: 7653: 7648: 7647: 7643: 7638: 7634: 7630: 7626: 7622: 7618: 7617: 7611: 7608: 7604: 7600: 7596: 7592: 7588: 7587: 7582: 7578: 7575: 7569: 7565: 7561: 7556: 7551: 7544: 7543: 7537: 7534: 7530: 7526: 7522: 7517: 7513: 7509: 7504: 7499: 7495: 7491: 7487: 7483: 7479: 7475: 7471: 7467: 7462: 7457: 7453: 7449: 7442: 7437: 7433: 7429: 7425: 7421: 7417: 7413: 7412:Combinatorica 7405: 7400: 7397: 7393: 7389: 7383: 7379: 7375: 7370: 7365: 7361: 7356: 7353: 7349: 7345: 7339: 7334: 7329: 7325: 7320: 7317: 7313: 7309: 7303: 7299: 7295: 7291: 7287: 7286:Szemerédi, E. 7283: 7279: 7275: 7274: 7270: 7265: 7259: 7255: 7250: 7246: 7241: 7237: 7233: 7226: 7222: 7218: 7213: 7210: 7204: 7200: 7196: 7195: 7189: 7186: 7180: 7176: 7172: 7167: 7163: 7159: 7155: 7151: 7150: 7146: 7140: 7132: 7128: 7123: 7118: 7114: 7110: 7106: 7099: 7096: 7091: 7087: 7082: 7077: 7073: 7069: 7068: 7063: 7059: 7055: 7051: 7045: 7042: 7037: 7033: 7029: 7025: 7021: 7017: 7013: 7009: 7005: 7001: 6997: 6990: 6987: 6982: 6978: 6974: 6970: 6966: 6959: 6956: 6950: 6945: 6941: 6940: 6932: 6929: 6924: 6920: 6915: 6910: 6906: 6902: 6901: 6893: 6890: 6885: 6881: 6876: 6871: 6867: 6860: 6857: 6852: 6848: 6844: 6840: 6836: 6832: 6828: 6824: 6823: 6822:Combinatorica 6815: 6812: 6806: 6801: 6794: 6791: 6786: 6782: 6778: 6776:0-7695-0850-2 6772: 6768: 6764: 6760: 6756: 6749: 6747: 6745: 6741: 6733: 6732: 6727: 6723: 6719: 6713: 6711: 6707: 6699: 6698: 6693: 6689: 6685: 6679: 6677: 6673: 6668: 6664: 6660: 6656: 6651: 6646: 6642: 6638: 6637: 6629: 6626: 6621: 6617: 6613: 6609: 6605: 6601: 6597: 6593: 6588: 6583: 6579: 6575: 6574: 6566: 6563: 6558: 6554: 6550: 6546: 6542: 6538: 6533: 6528: 6524: 6520: 6513: 6510: 6507: 6501: 6498: 6492: 6487: 6480: 6477: 6472: 6468: 6464: 6460: 6456: 6452: 6448: 6444: 6443:Combinatorica 6437: 6434: 6431: 6425: 6422: 6419: 6413: 6410: 6407: 6401: 6398: 6395: 6389: 6386: 6381: 6377: 6373: 6369: 6364: 6359: 6355: 6351: 6350:Combinatorica 6344: 6341: 6338: 6332: 6329: 6319: 6306: 6300: 6297: 6291: 6288: 6285: 6279: 6276: 6272: 6267: 6264: 6260: 6255: 6252: 6249: 6243: 6240: 6234: 6231: 6228: 6222: 6219: 6216: 6211: 6208: 6205: 6200: 6198: 6194: 6191: 6185: 6182: 6179: 6174: 6172: 6170: 6166: 6160: 6156: 6153: 6151: 6148: 6146: 6143: 6141: 6138: 6137: 6133: 6131: 6111: 6078:registers in 6076: 6069: 6061: 6041: 6024: 6018: 5982:to obtain an 5966:rounds, take 5960: 5915: 5908: 5900: 5891:has at least 5863: 5858: 5813: 5807: 5792: 5779:-halvers. An 5773: 5769: 5765: 5757: 5749: 5747: 5745: 5741: 5737: 5732: 5726: 5718: 5714: 5701: 5697: 5687: 5683: 5679: 5673: 5670: 5666: 5661: 5658: 5654: 5642: 5638: 5632: 5628: 5626: 5613: 5609: 5600: 5596: 5592: 5589: 5586: 5580: 5577: 5573: 5568: 5564: 5561: 5555: 5549: 5533: 5526: 5519: 5509: 5500: 5490: 5486: 5480: 5474: 5464: 5460: 5454: 5450: 5449: 5448: 5444: 5440: 5419: 5409: 5401: 5393: 5383: 5380: 5376: 5370: 5361: 5353: 5345: 5337: 5334: 5328: 5322: 5319: 5316: 5310: 5306: 5298: 5297: 5296: 5279: 5273: 5267: 5264: 5261: 5255: 5252: 5246: 5243: 5240: 5234: 5228: 5225: 5211: 5208: 5205: 5199: 5193: 5185: 5182: 5176: 5173: 5170: 5164: 5157: 5156: 5155: 5143: 5139: 5135: 5129: 5116: 5110: 5103: 5097: 5087: 5081: 5074: 5049: 5045: 5041: 5034: 5030: 5022: 5014: 5012: 5010: 5009:random graphs 5006: 5002: 4997: 4995: 4991: 4987: 4983: 4979: 4975: 4972: =  4971: 4967: 4963: 4960:) and robust 4959: 4955: 4951: 4947: 4943: 4939: 4935: 4930: 4923: 4921: 4918: 4904: 4897: 4893: 4874: 4870: 4863: 4855: 4851: 4834: 4825: 4815: 4810: 4804: 4800: 4793: 4776: 4774: 4768: 4765: 4761: 4757: 4753: 4749: 4731: 4728: 4725: 4720: 4695: 4692: 4687: 4683: 4679: 4671: 4662: 4652: 4631: 4628: 4623: 4619: 4615: 4607: 4595: 4579: 4567: 4556: 4545: 4541: 4533: 4529: 4523: 4520: 4515: 4511: 4497: 4488: 4484: 4476: 4472: 4466: 4463: 4462: 4461: 4457: 4453: 4445: 4441: 4433: 4429: 4421: 4417: 4389: 4385: 4370: 4353: 4346: 4341: 4337: 4333: 4330: 4325: 4320: 4316: 4310: 4300: 4295: 4291: 4287: 4284: 4274: 4271: 4266: 4261: 4257: 4248: 4243: 4239: 4235: 4232: 4224: 4221: 4216: 4208: 4204: 4200: 4195: 4191: 4184: 4177: 4176: 4175: 4152: 4148: 4135: 4114: 4113: 4112: 4107:-graph where 4096: 4092: 4088: 4081: 4077: 4066: 4062: 4046: 4042: 4031: 4027: 4023: 4018: 4010: 4008: 4006: 4002: 3998: 3994: 3990: 3986: 3969: 3965: 3960: 3956: 3953: 3948: 3945: 3942: 3934: 3930: 3927: 3920: 3919: 3918: 3914: 3910: 3902: 3885: 3882: 3877: 3874: 3871: 3866: 3863: 3860: 3852: 3824: 3821: 3816: 3813: 3810: 3805: 3802: 3799: 3792: 3791: 3790: 3786: 3768: 3766: 3762: 3758: 3734: 3729: 3726: 3723: 3718: 3715: 3705: 3701: 3690: 3687: 3677: 3673: 3659: 3656: 3649: 3648: 3647: 3641: 3635: 3631: 3611: 3608: 3605: 3600: 3597: 3594: 3560: 3554: 3551: 3546: 3543: 3540: 3535: 3532: 3527: 3523: 3510: 3504: 3496: 3493: 3477: 3472: 3469: 3463: 3457: 3438: 3433: 3416: 3407: 3404: 3401: 3398: 3392: 3389: 3386: 3383: 3377: 3371: 3368: 3365: 3362: 3359: 3356: 3350: 3344: 3341: 3335: 3332: 3329: 3326: 3320: 3317: 3311: 3305: 3302: 3299: 3296: 3293: 3290: 3280: 3279: 3278: 3262: 3252: 3247: 3237: 3231: 3228: 3225: 3197: 3193: 3184: 3179: 3150: 3140: 3135: 3109: 3108:Cayley graphs 3105: 3098: 3096: 3094: 3090: 3086: 3082: 3075:Constructions 3074: 3072: 3064: 3060: 3051: 3042: 3034: 3028: 3006: 2996: 2992: 2988: 2985: 2979: 2974: 2968: 2956: 2948: 2934: 2931: 2926: 2921: 2917: 2914: 2904: 2900: 2896: 2893: 2887: 2881: 2876: 2870: 2858: 2850: 2849: 2848: 2845: 2843: 2839: 2835: 2834:Markov chains 2831: 2830:Cheeger bound 2812: 2805: 2800: 2796: 2792: 2787: 2783: 2777: 2771: 2765: 2758: 2757: 2756: 2752: 2748: 2732: 2724: 2708: 2696: 2689: 2685: 2681: 2674: 2663: 2656: 2652: 2641: 2622: 2612: 2608: 2604: 2601: 2595: 2592: 2587: 2581: 2575: 2572: 2564: 2560: 2556: 2553: 2544: 2541: 2531: 2530: 2529: 2527: 2523: 2518: 2496: 2473: 2466: 2462: 2441: 2439: 2422: 2416: 2404: 2400: 2397: 2394: 2388: 2382: 2379: 2373: 2361: 2353: 2352: 2351: 2337: 2335: 2332: 2329: 2320: 2316: 2312: 2305:of the graph 2304: 2299: 2292: 2276: 2260: 2250: 2247: 2239: 2218: 2214: 2210: 2205: 2199: 2194: 2190: 2184: 2179: 2176: 2173: 2169: 2164: 2159: 2154: 2146: 2136: 2135: 2134: 2117: 2109: 2101: 2091: 2083: 2080: 2069: 2066: 2063: 2060: 2057: 2054: 2051: 2043: 2040: 2033: 2032: 2031: 2029: 2021: 1992: 1988: 1979: 1969: 1965: 1950: 1947: 1940: 1939: 1938: 1935: 1924: 1915: 1914: 1905: 1896: 1882: 1873: 1869: 1860: 1855: 1851: 1843: 1833: 1811: 1801: 1798: 1785: 1771: 1768: 1763: 1759: 1753: 1750: 1747: 1734: 1718: 1715: 1705: 1701: 1690: 1687: 1684: 1671: 1666: 1664: 1658: 1651: 1642: 1638: 1632: 1626: 1622: 1601: 1598: 1588: 1584: 1573: 1570: 1567: 1555: 1554: 1553: 1542: 1535: 1530: 1521: 1499:implies that 1498: 1494: 1465: 1461: 1457: 1453: 1449: 1445: 1441: 1426: 1424: 1421: 1417: 1413: 1400: 1381: 1345: 1334: 1316: 1288: 1285: 1280: 1272: 1264: 1261: 1253: 1247: 1235: 1227: 1226: 1225: 1217: 1210: 1206: 1201: 1195: 1185: 1175: 1166: 1162: 1158: 1149: 1143: 1118: 1107: 1089: 1061: 1058: 1053: 1045: 1037: 1034: 1026: 1020: 1008: 1000: 999: 998: 993:) of a graph 992: 991:magnification 988: 982: 975: 971: 963: 947: 928: 918: 910: 886: 881: 877: 870: 859: 853: 850: 847: 844: 833: 827: 821: 814: 813: 812: 808: 804: 796: 787: 783: 763: 760: 752: 744: 741: 730: 725: 722: 716: 701: 694: 684: 675: 637: 632: 628: 621: 615: 606: 587: 586: 585: 582: 572: 571:edge boundary 567: 562:vertices and 554: 542: 538: 534: 530: 526: 503: 500: 497: 494: 491: 488: 485: 479: 470: 464: 461: 455: 452: 449: 440: 434: 431: 428: 422: 415: 414: 413: 406: 402: 398: 393: 384: 379: 375: 371: 350: 344: 341: 338: 335: 332: 329: 326: 320: 311: 305: 302: 296: 293: 290: 281: 278: 267: 253: 242: 227: 209: 206: 201: 193: 185: 182: 174: 168: 162: 155: 154: 153: 141: 137: 132: 128: 124: 116: 114: 112: 108: 104: 99: 97: 93: 89: 85: 81: 73: 71: 69: 65: 61: 57: 53: 49: 45: 41: 37: 33: 19: 7655: 7623:(3): 67–84, 7620: 7614: 7590: 7584: 7541: 7524: 7520: 7493: 7489: 7454:(3): 12–es, 7451: 7447: 7415: 7411: 7359: 7323: 7289: 7253: 7235: 7231: 7193: 7170: 7161: 7112: 7108: 7098: 7074:(1): 73–82. 7071: 7070:. Series B. 7065: 7044: 7003: 6999: 6989: 6972: 6968: 6958: 6937: 6931: 6904: 6898: 6892: 6865: 6859: 6826: 6820: 6814: 6805:math/0312022 6793: 6758: 6730: 6696: 6640: 6634: 6628: 6577: 6571: 6565: 6522: 6518: 6512: 6500: 6479: 6449:(2): 83–96. 6446: 6442: 6436: 6424: 6412: 6400: 6388: 6353: 6349: 6343: 6331: 6317: 6307:. Note that 6299: 6290: 6278: 6266: 6259:Dodziuk 1984 6254: 6242: 6233: 6221: 6210: 6184: 6109: 6074: 6067: 6059: 6039: 6022: 6016: 5961: 5916: 5906: 5898: 5859: 5833:and at most 5811: 5805: 5790: 5774: 5767: 5763: 5759: 5728: 5646: 5640: 5636: 5542: 5531: 5524: 5517: 5507: 5498: 5478: 5472: 5462: 5458: 5442: 5438: 5434: 5294: 5141: 5137: 5133: 5130: 5114: 5108: 5101: 5095: 5091:, we expect 5085: 5079: 5047: 5043: 5039: 5032: 5028: 5024: 4998: 4990:cryptography 4986:Dinur (2007) 4931: 4927: 4916: 4902: 4895: 4891: 4872: 4868: 4861: 4853: 4849: 4828: 4823: 4813: 4808: 4802: 4798: 4786:vertex left 4780: 4663: 4560: 4543: 4539: 4531: 4527: 4524:- Move from 4521: 4513: 4509: 4486: 4482: 4474: 4470: 4467:- Move from 4464: 4455: 4451: 4443: 4439: 4431: 4427: 4419: 4415: 4387: 4383: 4371: 4368: 4173: 4150: 4133: 4094: 4090: 4086: 4079: 4075: 4064: 4060: 4044: 4040: 4020: 3987: 3984: 3912: 3908: 3900: 3840: 3784: 3769: 3759: 3749: 3633: 3629: 3506: 3443:, the graph 3436: 3435: 3431: 3102: 3078: 3062: 3058: 3049: 3040: 3032: 3026: 3021: 2846: 2827: 2750: 2746: 2722: 2701:= 2 – 2cos(2 2694: 2687: 2683: 2676: 2672: 2661: 2654: 2650: 2637: 2528:states that 2516: 2494: 2471: 2469:and the gap 2464: 2460: 2445: 2437: 2341: 2330: 2327: 2297: 2290: 2277: 2235: 2132: 2017: 1936: 1922: 1913:spectral gap 1911: 1894: 1871: 1867: 1853: 1849: 1841: 1828: 1786: 1732: 1669: 1667: 1656: 1649: 1640: 1636: 1630: 1624: 1620: 1616: 1543: 1533: 1528: 1519: 1463: 1459: 1455: 1430: 1419: 1415: 1411: 1398: 1360: 1215: 1208: 1204: 1202: 1193: 1183: 1173: 1164: 1160: 1156: 1147: 1141: 1133: 990: 986: 980: 973: 969: 967: 806: 802: 794: 785: 781: 699: 692: 682: 676: 660: 583: 570: 565: 552: 543: 536: 532: 528: 524: 521: 404: 400: 396: 391: 382: 377: 373: 369: 365: 139: 135: 126: 122: 120: 100: 95: 91: 87: 77: 44:connectivity 40:sparse graph 35: 32:graph theory 29: 7593:(4): 1–24, 6907:: 367–410. 6718:Adam Marcus 6684:Adam Marcus 6643:: 269–282. 6335:see, e.g., 6126:must be an 5914:neighbors. 5845:. The sets 5491:of a graph 4982:PCP theorem 4920:-expander. 4408:th edge of 4053:-graph and 1881:eigenvector 1448:eigenvalues 1220:of a graph 548:of at most 144:of a graph 74:Definitions 7406:(2000), "λ 7404:Tetali, P. 7282:Komlós, J. 7141:References 7050:Alon, Noga 6914:1506.02335 6875:1604.03544 6650:2006.13605 6491:cs/0405020 6130:-halving. 6106:is not in 5962:After all 5864:, a depth 5860:Following 5857:-halving. 4980:) and the 4968:, such as 4946:extractors 4938:algorithms 4811:– 2)| 4807:| ≥ ( 4760:Srivastava 4506:to get to 3997:Srivastava 3898:for every 2020:orthogonal 1937:If we set 1645:-graph on 1487:. Because 690:0 ≤ | 679:min | 80:multigraph 7607:207168478 7550:CiteSeerX 7456:CiteSeerX 7364:CiteSeerX 7278:Ajtai, M. 7131:0894-0347 7090:0095-8956 7028:1749-6632 6944:CiteSeerX 6843:0209-9683 6667:220042379 6612:0020-9910 6587:1212.5216 6557:253743928 6532:1212.5216 6463:1439-6912 6358:CiteSeerX 5688:λ 5674:⁡ 5662:⁡ 5601:λ 5581:⁡ 5562:≤ 5550:χ 5402:⋅ 5384:λ 5381:≤ 5354:⋅ 5338:⋅ 5329:− 5271:∖ 5238:∖ 5209:∩ 4881:of order 4827:| ≤ 4764:bipartite 4729:− 4693:⁡ 4629:⁡ 4338:λ 4317:λ 4292:λ 4288:− 4258:λ 4240:λ 4236:− 4205:λ 4192:λ 4185:ϕ 4030:Wigderson 4001:bipartite 3946:− 3928:τ 3886:ε 3875:− 3864:≤ 3861:λ 3825:ε 3814:− 3803:≤ 3800:λ 3727:− 3716:≤ 3702:λ 3674:λ 3657:λ 3638:-graphs. 3609:− 3595:λ 3552:− 3544:− 3533:≥ 3524:λ 3470:≤ 3458:λ 3393:± 3366:± 3321:± 3294:± 3253:× 3238:∈ 3141:× 3104:Algebraic 3089:Noga Alon 2993:λ 2989:− 2975:≤ 2932:− 2901:λ 2897:− 2877:≤ 2797:λ 2793:− 2778:≤ 2733:π 2709:π 2640:hypercube 2609:λ 2605:− 2588:≤ 2573:≤ 2561:λ 2557:− 2401:⋅ 2395:≤ 2380:≤ 2251:∈ 2170:∑ 2151:‖ 2144:‖ 2106:‖ 2099:‖ 2088:‖ 2078:‖ 2067:≠ 2055:⊥ 2041:λ 1989:λ 1966:λ 1948:λ 1802:∈ 1772:λ 1769:≤ 1760:λ 1751:≠ 1733:one-sided 1719:λ 1716:≤ 1702:λ 1688:≠ 1670:two-sided 1602:λ 1599:≤ 1585:λ 1571:≠ 1548:-vertex, 1493:symmetric 1370:∂ 1305:∂ 1281:≤ 1078:∂ 1054:≤ 932:¯ 890:¯ 851:⊊ 845:⊊ 842:∅ 756:¯ 734:¯ 696:| ≤ 641:¯ 604:∂ 501:∈ 489:∈ 462:∈ 395: := 342:∉ 330:∈ 303:∈ 276:∂ 225:∂ 202:≤ 7707:Category 7679:Archived 7637:18098370 7478:53244523 7352:15323404 7316:15311122 7223:(2006), 7154:Alon, N. 7036:85243045 6942:. SIAM. 6851:14422668 6728:(2015). 6694:(2013). 6620:16411939 6471:41083612 6134:See also 5821:at most 5698:⌉ 5655:⌈ 5631:diameter 5106:• | 4875:) > 0 4847:that is 4790:regular 4756:Spielman 4144:) < 1 4022:Reingold 3993:Spielman 3966:⌉ 3935:⌈ 3917:, where 3761:Lubotzky 3576:, where 3439:For all 3437:Theorem. 3165:, where 2749:) = Θ(1/ 2648:, where 1898:, where 1852:= 1, …, 1847:for all 1787:Because 1472:, where 1440:-regular 666:and add 84:boundary 56:spectral 7512:1999107 7432:1173532 7396:6364755 7008:Bibcode 6592:Bibcode 6537:Bibcode 6380:8666466 6108:(1, …, 6072:⁠ 6055:⁠ 6044:are in 6038:(1, …, 6026:⁄ 5911:⁠ 5894:⁠ 5853:are an 5837:of the 5825:of the 5815:⁄ 5789:(1, …, 5535:⁄ 5511:⁄ 5476:⁄ 5099:⁄ 5083:⁄ 4860:1 > 4131:, then 3847:random 3085:zig-zag 3030:⁄ 2295:⁠ 2281:⁠ 2236:is the 2133:where 1902:is the 1857:is the 1839:⁄ 1735:, with 1517:≥ … ≥ λ 1450:of the 1397:is the 1194:exactly 1146:is the 703:⁄ 569:is the 556:⁄ 7635:  7605:  7570:  7552:  7510:  7476:  7458:  7430:  7394:  7384:  7366:  7350:  7340:  7314:  7304:  7260:  7205:  7181:  7129:  7088:  7034:  7026:  6946:  6849:  6841:  6785:420651 6783:  6773:  6665:  6618:  6610:  6555:  6469:  6461:  6378:  6360:  5541:, then 5118:| 4988:). In 4864:> 0 4821:| 4817:| 4796:| 4752:Marcus 4594:Linial 4392:where 4161:) ≤ λ 4129:< 1 4121:< 1 4057:is an 4028:, and 4026:Vadhan 3989:Marcus 3903:> 0 3787:> 0 3765:Sarnak 3047:, and 2725:) ≈ (2 2686:= Θ(1/ 2682:) = 4/ 2526:Milman 2313:. For 2238:2-norm 1910:. The 1904:degree 1879:is an 1875:, and 1617:as an 1495:, the 1361:where 1134:where 985:(also 798:| 792:| 686:| 483:  477:  324:  318:  268:where 125:(also 111:degree 94:, and 48:vertex 7633:S2CID 7603:S2CID 7546:(PDF) 7508:JSTOR 7474:S2CID 7444:(PDF) 7428:S2CID 7392:S2CID 7348:S2CID 7312:S2CID 7228:(PDF) 7032:S2CID 6909:arXiv 6870:arXiv 6847:S2CID 6800:arXiv 6781:S2CID 6735:(PDF) 6701:(PDF) 6663:S2CID 6645:arXiv 6616:S2CID 6582:arXiv 6553:S2CID 6527:arXiv 6486:arXiv 6467:S2CID 6376:S2CID 6161:Notes 5766:(log 5527:< 4999:In a 4898:) log 4889:with 4566:-lift 4557:Lifts 4083:is a 4037:is a 4005:lifts 3853:have 3507:By a 2657:) = 1 2515:< 2505:. If 2446:When 1826:with 1631:graph 1431:When 1192:with 412:and 388:with 38:is a 34:, an 7568:ISBN 7382:ISBN 7338:ISBN 7302:ISBN 7258:ISBN 7203:ISBN 7179:ISBN 7127:ISSN 7086:ISSN 7024:ISSN 6839:ISSN 6771:ISBN 6608:ISSN 6459:ISSN 6122:and 6058:1 – 5994:and 5974:and 5897:1 – 5883:and 5849:and 5799:and 5738:and 5729:The 5643:, λ) 5629:The 5516:≤ χ( 5487:The 5465:, λ) 5445:, λ) 5150:and 5124:and 5055:and 5035:, λ) 4758:and 4424:and 4400:and 4123:and 3995:and 3907:1 – 3688:< 3642:are 3636:, λ) 3598:< 3587:and 2832:for 2692:and 2659:and 2524:and 2522:Alon 1654:for 1643:, λ) 1627:, λ) 1503:has 1483:and 1442:, a 1418:) \ 1265:< 1203:The 1163:) \ 1038:< 968:The 403:) \ 186:< 121:The 52:edge 7625:doi 7595:doi 7560:doi 7529:doi 7498:doi 7494:284 7466:doi 7420:doi 7374:doi 7328:doi 7294:doi 7240:doi 7117:doi 7076:doi 7016:doi 7004:175 6977:doi 6919:doi 6905:323 6880:doi 6831:doi 6763:doi 6655:doi 6641:256 6600:doi 6578:201 6545:doi 6523:201 6451:doi 6368:doi 6320:− λ 6098:in 6090:in 5998:in 5990:in 5671:log 5659:log 5578:log 5451:An 4794:, 4684:log 4620:log 4561:An 4536:to 4532:l' 4522:Zag 4514:l' 4502:in 4487:k' 4479:to 4465:Zig 4448:to 4165:+ λ 4157:, λ 4140:, λ 4115:If 4101:, λ 4067:, λ 4047:, λ 3664:max 3065:– λ 3044:out 2863:out 2840:in 2697:– λ 2668:= 2 2664:– λ 2474:− λ 2450:is 2409:out 2366:out 2048:max 2022:to 1954:max 1925:− λ 1916:of 1883:of 1861:of 1744:max 1681:max 1659:≠ 1 1564:max 1532:= − 1513:≥ λ 1491:is 1468:of 1435:is 1401:of 1258:min 1180:out 1150:of 1138:out 1082:out 1031:min 1013:out 989:or 977:out 900:min 838:min 619:min 595:min 573:of 179:min 148:on 129:or 54:or 30:In 7709:: 7654:, 7631:, 7621:43 7619:, 7601:, 7591:55 7589:, 7566:, 7558:, 7525:27 7523:, 7506:, 7492:, 7472:, 7464:, 7452:54 7450:, 7446:, 7426:, 7416:20 7414:, 7390:, 7380:, 7372:, 7346:, 7336:, 7310:, 7300:, 7284:; 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Index

Expander graphs
graph theory
sparse graph
connectivity
vertex
edge
spectral
complexity theory
computer networks
error-correcting codes
multigraph
boundary
connected component
complete graph
degree
Cheeger constant
d-regular
linear algebraic
eigenvalues
adjacency matrix
symmetric
spectral theorem
expander mixing lemma
stationary distribution
eigenvector
degree
spectral gap
orthogonal
Rayleigh quotient
2-norm

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