1,189 research outputs found

    THE ELECTRONIC JOURNAL OF COMBINATORICS (2014), DS1.14 References

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    and Computing 11. The results of 143 references depend on computer algorithms. The references are ordered alphabetically by the last name of the first author, and where multiple papers have the same first author they are ordered by the last name of the second author, etc. We preferred that all work by the same author be in consecutive positions. Unfortunately, this causes that some of the abbreviations are not in alphabetical order. For example, [BaRT] is earlier on the list than [BaLS]. We also wish to explain a possible confusion with respect to the order of parts and spelling of Chinese names. We put them without any abbreviations, often with the last name written first as is customary in original. Sometimes this is different from the citations in other sources. One can obtain all variations of writing any specific name by consulting the authors database of Mathematical Reviews a

    Small Ramsey Numbers

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    We present data which, to the best of our knowledge, includes all known nontrivial values and bounds for specific graph, hypergraph and multicolor Ramsey numbers, where the avoided graphs are complete or complete without one edge. Many results pertaining to other more studied cases are also presented. We give references to all cited bounds and values, as well as to previous similar compilations. We do not attempt complete coverage of asymptotic behavior of Ramsey numbers, but concentrate on their specific values

    On Size Bipartite and Tripartite Ramsey Numbers for The Star Forest and Path on 3 Vertices

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    For simple graphs G and H the size multipartite Ramsey number mj(G,H) is the smallest natural number t such that any arbitrary red-blue coloring on the edges of Kjxt contains a red G or a blue H as a subgraph. We studied the size tripartite Ramsey numbers m3(G,H) where G=mK1,n and H=P3. In this paper, we generalize this result. We determine m3(G,H) where G is a star forest, namely a disjoint union of heterogeneous stars, and H=P3. Moreover, we also determine m2(G,H) for this pair of graphs G and H

    Some exact values on Ramsey numbers related to fans

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    For two given graphs FF and HH, the Ramsey number R(F,H)R(F,H) is the smallest integer NN such that any red-blue edge-coloring of the complete graph KNK_N contains a red FF or a blue HH. When F=HF=H, we simply write R2(H)R_2(H). For an positive integer nn, let K1,nK_{1,n} be a star with n+1n+1 vertices, FnF_n be a fan with 2n+12n+1 vertices consisting of nn triangles sharing one common vertex, and nK3nK_3 be a graph with 3n3n vertices obtained from the disjoint union of nn triangles. In 1975, Burr, Erd\H{o}s and Spencer \cite{B} proved that R2(nK3)=5nR_2(nK_3)=5n for n≥2n\ge2. However, determining the exact value of R2(Fn)R_2(F_n) is notoriously difficult. So far, only R2(F2)=9R_2(F_2)=9 has been proved. Notice that both FnF_n and nK3nK_3 contain nn triangles and ∣V(Fn)∣<∣V(nK3)∣|V(F_n)|<|V(nK_3)| for all n≥2n\ge 2. Chen, Yu and Zhao (2021) speculated that R2(Fn)≤R2(nK3)=5nR_2(F_n)\le R_2(nK_3)=5n for nn sufficiently large. In this paper, we first prove that R(K1,n,Fn)=3n−εR(K_{1,n},F_n)=3n-\varepsilon for n≥1n\ge1, where ε=0\varepsilon=0 if nn is odd and ε=1\varepsilon=1 if nn is even. Applying the exact values of R(K1,n,Fn)R(K_{1,n},F_n), we will confirm R2(Fn)≤5nR_2(F_n)\le 5n for n=3n=3 by showing that R2(F3)=14R_2(F_3)=14.Comment: 10 pages, 3 figure

    The bipartite Ramsey numbers BR(C8,C2n)BR(C_8, C_{2n})

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    For the given bipartite graphs G1,G2,…,GtG_1,G_2,\ldots,G_t, the multicolor bipartite Ramsey number BR(G1,G2,…,Gt)BR(G_1,G_2,\ldots,G_t) is the smallest positive integer bb such that any tt-edge-coloring of Kb,bK_{b,b} contains a monochromatic subgraph isomorphic to GiG_i, colored with the iith color for some 1≤i≤t1\leq i\leq t. We compute the exact values of the bipartite Ramsey numbers BR(C8,C2n)BR(C_8,C_{2n}) for n≥2n\geq2

    FK Comae Berenices, King of Spin: The COCOA-PUFS Project

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    COCOA-PUFS is an energy-diverse, time-domain study of the ultra-fast spinning, heavily spotted, yellow giant FK Com (HD117555; G4 III). This single star is thought to be a recent binary merger, and is exceptionally active by measure of its intense ultraviolet and X-ray emissions, and proclivity to flare. COCOA-PUFS was carried out with Hubble Space Telescope in the UV (120-300 nm), using mainly its high-performance Cosmic Origins Spectrograph, but also high-precision Space Telescope Imaging Spectrograph; Chandra X-ray Observatory in the soft X-rays (0.5-10 keV), utilizing its High-Energy Transmission Grating Spectrometer; together with supporting photometry and spectropolarimetry in the visible from the ground. This is an introductory report on the project. FK Com displayed variability on a wide range of time scales, over all wavelengths, during the week-long main campaign, including a large X-ray flare; "super-rotational broadening" of the far-ultraviolet "hot-lines" (e.g., Si IV 139 nm (T~80,000 K) together with chromospheric Mg II 280 nm and C II 133 nm (10,000-30,000 K); large Doppler swings suggestive of bright regions alternately on advancing and retreating limbs of the star; and substantial redshifts of the epoch-average emission profiles. These behaviors paint a picture of a highly extended, dynamic, hot (10 MK) coronal magnetosphere around the star, threaded by cooler structures perhaps analogous to solar prominences, and replenished continually by surface activity and flares. Suppression of angular momentum loss by the confining magnetosphere could temporarily postpone the inevitable stellar spindown, thereby lengthening this highly volatile stage of coronal evolution.Comment: to be published in ApJ
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