1,118 research outputs found

    Star 5-edge-colorings of subcubic multigraphs

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    The star chromatic index of a multigraph GG, denoted χs′(G)\chi'_{s}(G), is the minimum number of colors needed to properly color the edges of GG such that no path or cycle of length four is bi-colored. A multigraph GG is star kk-edge-colorable if χs′(G)≤k\chi'_{s}(G)\le k. Dvo\v{r}\'ak, Mohar and \v{S}\'amal [Star chromatic index, J Graph Theory 72 (2013), 313--326] proved that every subcubic multigraph is star 77-edge-colorable, and conjectured that every subcubic multigraph should be star 66-edge-colorable. Kerdjoudj, Kostochka and Raspaud considered the list version of this problem for simple graphs and proved that every subcubic graph with maximum average degree less than 7/37/3 is star list-55-edge-colorable. It is known that a graph with maximum average degree 14/514/5 is not necessarily star 55-edge-colorable. In this paper, we prove that every subcubic multigraph with maximum average degree less than 12/512/5 is star 55-edge-colorable.Comment: to appear in Discrete Mathematics. arXiv admin note: text overlap with arXiv:1701.0410

    Clinical investigation on angle-closure glaucoma patients with cataract treated by phacoemulsification combined with trabeculectomy

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    AIM: To investigate the effectiveness of phacoemulsification with intraocular lens(IOL)implantation combined with trabeculectomy in patients with cataract and angle-closure glaucoma.<p>METHODS: In 36 cases(46 eyes)of angle-closure glaucoma with cataract, phacoemulsification with foldable IOL implantation combined with trabeculectomy was performed. Data of pre- and post-operation, including visual acuity, intraocular pressure, filtering bleb, anterior chamber depth, chamber angle, and funds were all recorded and analyzed in detail.<p>RESULTS: During the follow-up of 3 months to 2 years,visual acuity of 43 eyes(93.5%)got improved, and intraocular pressure in 44 eyes(95.7%)were controlled in normal range(<21mmHg). Mean anterior chamber depth of 35 patients(46 eyes)got deeper from 2.1mm to 3.8mm(average 2.1±0.3mm to 3.8±0.4mm)after operation, with chamber angle opened to some extent. Six eyes(13.0%)got mild to moderate corneal edema, without corneal endothelial decompensation.<p>CONCLUSION: Phacoemulsification with IOL implantation combined with trabeculectomy is an effective and safe surgical technique for patients with angle-closure glaucoma and cataract, with satisfied control of intraocular pressure, deepening of anterior chamber, opening of anterior chamber angle, and improving visual function

    Optical appearance of Einstein-{\AE}ther black hole surrounded by thin disk

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    In Einstein-{\AE}ther theory, the Lorentz symmetry is locally broken in the high-energy regime due to the presence of the{\AE}ther field. This shall leave significant imprint on astronomical observation. In this paper, we investigate the optical appearance of two types of the static and spherically symmetric black holes in Einstein-{\AE}ther theory. Via Euler-Lagrange equation, we obtain the equations of motion of the photon and calculate the total deflection angle of the photon trajectory around the black hole. By classifying the light rays with the total number of orbits, we study the effects of coupling constants on the direct image, lensing ring, and photon ring. The features of the light trajectories are also investigated by comparing with the Einstein-{\AE}ther theory and general relativity. Moreover, we also show the explicit optical appearance of black holes surrounded by thin disk emissions with three characteristic emitted models. The results indicate that the direct image gives the main contribution to the total flux, and the lensing ring just gives a very small contribution, whereas the role of the photon ring is negligible. The optical appearances are also found to significantly rely on these coupling constants.Comment: 19 pages, 6 figure

    Floquet Weyl semimetal phases in light-irradiated higher-order topological Dirac semimetals

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    Floquet engineering, the concept of tailoring a system by a periodic drive, is increasingly exploited to design and manipulate topological phases of matter. In this work, we study periodically driven higher-order topological Dirac semimetals associated with a kk-dependent quantized quadrupole moment by applying circularly polarized light. The undriven Dirac semimetals feature gapless higher-order hinge Fermi arc states which are the consequence of the higher-order topology of the Dirac nodes. Floquet Weyl semimetal phases with hybrid-order topology, characterized by both a kk-dependent quantized quadrupole moment and a kk-dependent Chern number, emerge when illumining circularly polarized light. Such Floquet Weyl semimetals support both hinge Fermi arc states and topological surface Fermi arc states. In addition, Floquet Weyl semimetals with tilted Weyl cones in higher-order topological Dirac semimetals are also discussed. Considering numerous higher-order topological Dirac semimetal materials were recently proposed, our findings can be testable soon.Comment: Accepted for publication as a Letter in Phys. Rev.
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