The maxinmum jump number M(n, k) over a class of n×n matrices of zerosand ones with constant row and column sum k has been investigated by Brualdi andJung in [1] where they proposed the conjectureM(2k, k + 1) = 3...The maxinmum jump number M(n, k) over a class of n×n matrices of zerosand ones with constant row and column sum k has been investigated by Brualdi andJung in [1] where they proposed the conjectureM(2k, k + 1) = 3l - 1 + [k-1/2]In this note, we give two counter-examples to this conjecture.展开更多
The covariant entropy bound conjecture is an important hint for the quantum gravity, with several versions available in the literature. For cosmology, Ashtekar and Wilson-Ewing ever show the consistence between the lo...The covariant entropy bound conjecture is an important hint for the quantum gravity, with several versions available in the literature. For cosmology, Ashtekar and Wilson-Ewing ever show the consistence between the loop gravity theory and one version of this conjecture. Recently, He and Zhang [J. High Energy Phys. 10 (2007) 077] proposed a version for the dynamical horizon of the universe, which validates the entropy bound conjecture for the cosmology filled with perfect fluid in the classical scenario when the universe is far away from the big bang singularity. However, their conjecture breaks down near big bang region. We examine this conjecture in the context of the loop quantum cosmology. With the example of photon gas, this conjecture is protected by the quantum geometry effects as expected.展开更多
We rephrase the Gopakumar-Vafa conjecture on genus zero Gromov-Witten invariants of Calabi-Yau threefolds in terms of the virtual degree of the moduli of pure dimension one stable sheaves and investigate the conjectur...We rephrase the Gopakumar-Vafa conjecture on genus zero Gromov-Witten invariants of Calabi-Yau threefolds in terms of the virtual degree of the moduli of pure dimension one stable sheaves and investigate the conjecture for K3 fibred local Calabi-Yau threefolds.展开更多
基金Supported by the Science Foundation of Hainan(10002)
文摘The maxinmum jump number M(n, k) over a class of n×n matrices of zerosand ones with constant row and column sum k has been investigated by Brualdi andJung in [1] where they proposed the conjectureM(2k, k + 1) = 3l - 1 + [k-1/2]In this note, we give two counter-examples to this conjecture.
基金Supported by the National Natural Science Foundation of China under Grant No. 11175019the Fundamental Research Funds for the Central Universities
文摘The covariant entropy bound conjecture is an important hint for the quantum gravity, with several versions available in the literature. For cosmology, Ashtekar and Wilson-Ewing ever show the consistence between the loop gravity theory and one version of this conjecture. Recently, He and Zhang [J. High Energy Phys. 10 (2007) 077] proposed a version for the dynamical horizon of the universe, which validates the entropy bound conjecture for the cosmology filled with perfect fluid in the classical scenario when the universe is far away from the big bang singularity. However, their conjecture breaks down near big bang region. We examine this conjecture in the context of the loop quantum cosmology. With the example of photon gas, this conjecture is protected by the quantum geometry effects as expected.
基金Partially supported by NSF grants DMS-0200477 and DMS-0233550.
文摘We rephrase the Gopakumar-Vafa conjecture on genus zero Gromov-Witten invariants of Calabi-Yau threefolds in terms of the virtual degree of the moduli of pure dimension one stable sheaves and investigate the conjecture for K3 fibred local Calabi-Yau threefolds.
