Density dependences of the mass and self-energies of Λc in nuclear matter are studied in the parity projected QCD sum rule. Effects of nuclear matter are taken into account through the quark and gluon condensates. It is found that the four-quark condensates give dominant contributions. As the density dependences of the four-quark condensates are not known well, we examine two hypotheses. One is based on the factorization hypothesis (F-type) and the other is derived from the perturbative chiral quark model (QM-type). The F-type strongly depends on density, while the QM-type gives a weaker dependence. It is found that, for the F-type dependence, the energy of Λc increases as the density of nuclear matter grows, that is, Λc feels repulsion. On the other hand, the QM-type predicts a weak attraction (∼ 20 MeV at the normal nuclear density) for Λc in nuclear matter. We carry out a similar analysis of the Λ hyperon and find that the F-type density dependence is too strong to explain the observed binding energy of Λ in nuclei. Thus we conclude that the weak density dependence of the four-quark condensate is more realistic. The scalar and vector self-energies of Λc for the QM-type dependence are found to be much smaller than those of the light baryons.

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Charmonium spectral functions in vector and pseudoscalar channels at finite temperature are investigated through the complex Borel sum rules and the maximum entropy method. Our approach enables us to extract the peaks corresponding to the excited charmonia, ψ and η c , as well as those of the ground states, J/ψ and ηc, which has never been achieved in usual QCD sum rule analyses. We show the spectral functions in vacuum and their thermal modification around the critical temperature, which leads to the almost simultaneous melting (or peak disappearance) of the ground and excited states.

A Dp-brane can be regarded as a configuration of infinitely many D(p −2k)-branes in bosonic string. We will show this property of D-branes in the superstring case using the hybrid formalism. It is convenient to study the boundary state for such D-branes to study such property between D-branes. We show that the boundary state for a D3-brane in a constant self-dual gauge field background can be expressed in terms of the boundary state for D-instantons in the hybrid formalism. * )