Bum-Hoon Lee

Spiky strings on AdS4 × CP3

We study a giant magnon and a spike solution for the string rotating on AdS(4) X CP**3 geometry. We consider rigid rotating fundamental string in the SU(2) X SU(2) sector inside the CP**3 and find out the general form of all the conserved charges. We find out the dispersion relation corresponding to both the known giant magnon and the new spike solutions. We further study the finite size correction in both cases.

Multi-gluon scattering: A string-based calculation

Abstract We suggest the use of open bosonic string theory to compute tree-level multi-gluon scattering amplitudes in QCD, since this considerably simplifies the mechsnics of the calculation, as well as manifest the gauge invariance and symmetry structure of the result. We illustrate the method by computing the gluon five-point function.

A dual geometry of the hadron in dense matter

We identify the dual geometry of the hadron phase of dense nuclear matter and investigate the confinement/deconfinement phase transition. We suggest that the low temperature phase of the RN black hole with the full backreaction of the bulk gauge field is described by the zero mass limit of the RN black hole with hard wall. We calculated the density dependence of critical temperature and found that the phase diagram closes. We also study the density dependence of the ρ meson mass.

Is the firewall consistent? Gedanken experiments on black hole complementarity and firewall proposal

In this paper, we discuss the black hole complementarity and the firewall proposal at length. Black hole complementarity is inevitable if we assume the following five things: unitarity, entropy-area formula, existence of an information observer, semi-classical quantum field theory for an asymptotic observer, and the general relativity for an in-falling observer. However, large N rescaling and the AMPS argument show that black hole complementarity is inconsistent. To salvage the basic philosophy of the black hole complementarity, AMPS introduced a firewall around the horizon. According to large N rescaling, the firewall should be located close to the apparent horizon. We investigate the consistency of the firewall with the two critical conditions: the firewall should be near the time-like apparent horizon and it should not affect the future infinity. Concerning this, we have introduced a gravitational collapse with a false vacuum lump which can generate a spacetime structure with disconnected apparent horizons. This reveals a situation that there is a firewall outside of the event horizon, while the apparent horizon is absent. Therefore, the firewall, if it exists, not only does modify the general relativity for an in-falling observer, but also modify the semi-classical quantum field theory for an asymptotic observer.

Correlation functions of magnon and spike

After considering a solitonic string moving in the Poincare

On the giant magnon and spike solutions for strings on AdS3 × S3

AdS

Strange metallic behavior in anisotropic background

and two-dimensional sphere, we calculate the two-point correlation function of magnon and spike in the semi-classical limit without any explicit solution. We also calculate the three-point correlation functions between two heavy and one light operators. We find that the coupling between two heavy and one light operators in the string side is the exactly same as one obtained from the gauge theory by using the RG analysis.

Deconfinement phase transition in holographic QCD with matter

We study solutions for the rotating strings on the sphere with a background NS-NS field and on the anti-de-Sitter spacetime. We show the existence of magnon and single spike solutions on R × S2 in the presence of constant magnetic field as two limiting cases. We also study the solution for strings on AdS3 × S3 with Melvin deformation. The dispersion relations among various conserved charges are shown to receive finite corrections due to the deformation parameter. We further study the rotating string on AdS3 × S3 geometry with two conserved angular momenta on S3 and one spin along the AdS3. We show that there exists two kinds of solutions: a circular string solution and a helical string. We find out the dispersion relation among various charges and give physical interpretation of these solutions.

The CP(n) model on noncommutative plane

We continue our analysis on conductivity in the anisotropic background by employing the D-brane probe technique, where the D-branes play the role of charge carriers. The DC and AC conductivity for massless charge carriers are obtained analytically, while interesting curves for the AC conductivity are also plotted. For massive charge carriers, we calculate the DC and AC conductivities in the dilute limit and we fix the parameters in the Einstein-Maxwell-dilaton theory so that the background exhibits the same scaling behaviors as those for real-world strange metals. The DC conductivity at finite density is also computed.

Mass inflation in f(R) gravity ? A conjecture on the resolution of the mass inflation singularity

In the framework of a holographic QCD approach we study the influence of matter on the deconfinement temperature T{sub c}. We first consider the quark flavor number (N{sub f}) dependence of T{sub c}. We observe that T{sub c} decreases with N{sub f}, which is consistent with a lattice QCD result. We also delve into how the quark number density {rho}{sub q} affects the value of T{sub c}. We find that T{sub c} drops with increasing {rho}{sub q}. In both cases, we confirm that the contributions from quarks are suppressed by 1/N{sub c}, as it should be, compared to the ones from a gravitational action (pure Yang-Mills theory)