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31.
A. A. Makhnev D. V. Paduchikh 《Proceedings of the Steklov Institute of Mathematics》2009,267(1):149-163
A Moore graph is a regular graph of degree k and diameter d with v vertices such that v ≤ 1 + k + k(k ? 1) + ... + k(k ? 1)d?1. It is known that a Moore graph of degree k ≥ 3 has diameter 2; i.e., it is strongly regular with parameters λ = 0, µ = 1, and v = k 2 + 1, where the degree k is equal to 3, 7, or 57. It is unknown whether there exists a Moore graph of degree k = 57. Aschbacher showed that a Moore graph with k = 57 is not a graph of rank 3. In this connection, we call a Moore graph with k = 57 the Aschbacher graph and investigate its automorphism group G without additional assumptions (earlier, it was assumed that G contains an involution). 相似文献
32.
A. A. Makhnev A. V. Lukoyanov L. V. Nomerovannaya A. A. Shirokov S. N. Barilo G. L. Bychkov S. V. Shiryaev 《Journal of Experimental and Theoretical Physics》2018,126(6):779-783
The anisotropy of the components of the complex permittivity of vanadate Co3V2O8 and Co3V2O8 single crystals in the paramagnetic phase are studied by optical ellipsometry in the spectral region 0.5–5.0 eV. Our experimental results support the weak anisotropy of the optical response detected earlier for axes a and c. The optical properties are also investigated along axis b. The properties of both compounds are compared. The optical spectra of both compounds along axis b are shifted toward low energies as compared to axes a and c. The maximum of the main interband absorption band of Co3V2O8 is shifted toward low energies by 0.25–0.3 eV as compared to Co3V2O8. The electronic structure parameters of both compounds are determined. Optical function spectra are analyzed using the results of ab initio band calculations. 相似文献
33.
E. V. Mostovshchikova S. V. Naumov A. A. Makhnev N. I. Solin S. V. Telegin 《Journal of Experimental and Theoretical Physics》2014,118(2):297-303
The reflectance, the optical density, and the optical conductivity spectra of CaMn1 ? x Mo x O3 (x ≤ 0.07) polycrystals are studied over a wide spectral region. The substitution of Mo6+ ions for Mn4+ ions leads to a strong decrease in the first high-energy phonon band, which is related to vibrations in the MnO6 octahedron. The appearance of band-type charge carriers is detected in CaMn1 ? x Mo x O3 with x ≤ 0.04, and carrier localization is observed in CaMn0.93Mo0.07O3. This localization increases at T < 160 K, i.e., during the transition from the paramagnetic to the antiferromagnetic state with orbital ordering and a monoclinic structure. The optical conductivity spectrum of CaMn0.93Mo0.07O3 exhibits a strong shift of fundamental absorption bands, which is associated with a change in the band structure because of a decrease in the splitting of the 3d levels of Mn in the crystal field. 相似文献
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Mathematical Notes - A. A. Makhnev and M. S. Nirova found the intersection arrays of distance regular graphs with $$\lambda=2$$ and at most 4096 vertices. For graphs of diameter $$4$$ , of most... 相似文献
36.
Doklady Mathematics - An antipodal nonbipartite distance-regular graph Γ of diameter 3 has an intersection array $$\{ k,(r - 1){{c}_{2}},\;1;\;1,\;{{c}_{2}},\;k\} $$ ( $${{c}_{2}} < k -... 相似文献
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We obtain a convenient expression for the parameters of a strongly regular graph with k=2 in terms of the nonprincipal eigenvalues x and –y. It turns out in particular that such graphs are pseudogeometric for pG
x(2x,y–1). We prove that a strongly regular graph with parameters (35,16,6,8) is a quotient of the Johnson graph
(8,4). We also find the parameters of strongly regular graphs in which the neighborhoods of vertices are pseudogeometric graphs for pG
x(2x,t),x3. In consequence, we establish that a connected graph in which the neighborhoods of vertices are pseudogeometric graphs for pG
3(6,2) is isomorphic to the Taylor graph on 72 vertices or to the alternating form graph Alt(4,2) with parameters (64,35,18,20). 相似文献