We study the energy dispersions of holographic light mesons and their decay constants on dense nuclear medium. As the spatial momenta of mesons along the boundary direction increase, both observables of the mesons not only increase but also split acc
ording to the isospin charges. The decay constant of the negative meson is more large than that of the positive meson of the same type due to the chemical potentials of the background nucleons.
We study slow-roll inflation with a Gauss-Bonnet term that is coupled to an inflaton field nonminimally. We investigate the inflationary solutions for a specific type of the nonminimal coupling to the Gauss-Bonnet term and inflaton potential both ana
lytically and numerically. We also calculate the observable quantities such as the power spectra of the scalar and tensor modes, the spectral indices, the tensor-to-scalar ratio and the running spectral indices. Finally, we constrain our result with the observational data by Planck and BICEP2 experiment.
We study the holographic light meson spectra and their mass splitting in the nuclear medium. In order to describe the nuclear matter, we take into account the thermal charged AdS geometry with two flavor charges, which can be reinterpreted as the num
ber densities of proton and neutron after some field redefinitions. We show that the meson mass splitting occurs when there exists the density difference between proton and neutron. Depending on the flavor charge, the mass of the positively (negatively) charged meson increases (decreases) as the density difference increases, whereas the neutral meson mass is independent of the density difference. In the regime of the large nucleon density with a relatively large number difference between proton and neutron, we find that negatively charged pion becomes massless in the nuclear medium, so the pion condensate can occur. We also investigate the binding energy of a heavy quarkonium in the nuclear medium, in which the binding energy of a heavy quarkonium becomes weaker as the density difference increases.
We have considered non-conformal fluid dynamics whose gravity dual is a certain Einstein dilaton system with Liouville type dilaton potential, characterized by an intrinsic parameter $eta$. We have discussed the Hawking-Page transition in this framew
ork using hard-wall model and it turns out that the critical temperature of the Hawking-Page transition encapsulates a non-trivial dependence on $eta$. We also obtained transport coefficients such as AC conductivity, shear viscosity and diffusion constant in the hydrodynamic limit, which show non-trivial $eta$ dependent deviations from those in conformal fluids, although the ratio of the shear viscosity to entropy density is found to saturate the universal bound. Some of the retarded correlators are also computed in the high frequency limit for case study.
In the Einestein-dilaton theory with a Liouville potential parameterized by $eta$, we find a Schwarzschild-type black hole solution. This black hole solution, whose asymptotic geometry is described by the warped metric, is thermodynamically stable on
ly for $0 le eta < 2$. Applying the gauge/gravity duality, we find that the dual gauge theory represents a non-conformal thermal system with the equation of state depending on $eta$. After turning on the bulk vector fluctuations with and without a dilaton coupling, we calculate the charge diffusion constant, which indicates that the life time of the quasi normal mode decreases with $eta$. Interestingly, the vector fluctuation with the dilaton coupling shows that the DC conductivity increases with temperature, a feature commonly found in electrolytes.
We study two $1/N_c$ effects on the meson spectra by using the AdS/CFT correspondence where the $1/N_c$ corrections from the chiral condensate and the quark density are controlled by the gravitational backreaction of the massive scalar field and U(1)
gauge field respectively. The dual geometries with zero and nonzero current quark masses are obtained numerically. We discuss meson spectra and binding energy of heavy quarkonium with the subleading corrections in the hard wall model.
By using the gauge/gravity duality, we investigate the dual field theories of the anisotropic backgrounds, which are exact solutions of Einstein-Maxwell-dilaton theory with a Liouville potential. When we turn on the bulk gauge field fluctuation $A_x$
with a non-trivial dilaton coupling, the AC conductivity of this dual field theory is proportional to the frequency with an exponent depending on parameters of the anisotropic background. In some parameter regions, we find that this conductivity can have the negative exponent like the strange metal. In addition, we also investigate another U(1) gauge field fluctuation, which is not coupled with a dilaton field. We classify all possible conductivities of this system and find that the exponent of the conductivity is always positive.
We investigate the interaction between flat membrane and point-like graviton in the plane-wave matrix model. The one-loop effective potential in the large distance limit is computed and is shown to be of r^{-3} type where r is the distance between tw
o objects. This type of interaction has been interpreted as the one incorporating the smearing effect due to the configuration of flat membrane in plane-wave background. Our result supports this interpretation and provides one more evidence about it.
The gluon condensate is very sensitive to the QCD deconfinement transition since its value changes drastically with the deconfinement transition. We calculate the gluon condensate dependence of the heavy quark potential in AdS/CFT to study how the pr
operty of the heavy quarkonium is affected by a relic of the deconfinement transition. We observe that the heavy quark potential becomes deeper as the value of the gluon condensate decreases. We interpret this as a dropping of the heavy quarkonium mass just above the deconfinement transition, which is similar to the results obtained from QCD sum rule and from a bottom-up AdS/QCD model.
We study the possible types of the nucleation of vacuum bubbles. We classify vacuum bubbles in de Sitter background and present some numerical solutions. The thin-wall approximation is employed to obtain the nucleation rate and the radius of vacuum b
ubbles. With careful analysis we confirm that Parkes formula is also applicable to the large true vacuum bubbles. The nucleation of the false vacuum bubble in de Sitter background is also evaluated. The tunneling process in the potential with degenerate vacua is analyzed as the limiting cases of the large true vacuum bubble and false vacuum bubble. Next, we consider the pair creation of black holes in the background of bubble solutions. We obtain static bubble wall solutions of junction equation with black hole pair. The masses of created black holes are uniquely determined by the cosmological constant and surface tension on the wall. Finally, we obtain the rate of pair creation of black holes.
