O-Kab Kwon

Notes on supersymmetry enhancement of ABJM theory

We study the supersymmetry enhancement of ABJM theory. Starting from a = 2 supersymmetric Chern-Simons matter theory with gauge group U(2) × U(2) which is a truncated version of the ABJM theory, we find by using the monopole operator that there is additional = 2 supersymmetry related to the gauge group. We show this additional supersymmetry can combine with = 6 supersymmetry of the original ABJM theory to an enhanced = 8 SUSY with gauge group U(2) × U(2) in the case k = 1,2. We also discuss the supersymmetry enhancement of the ABJM theory with U(N) × U(N) gauge group and find a condition which should be satisfied by the monopole operator.

Electromagnetic string fluid in rolling tachyon

We study Born-Infeld type effective action for unstable D3-brane system including a tachyon and an abelian gauge field, and find the rolling tachyon with constant electric and magnetic fields as the most general homogeneous solution. Tachyonic vacua are characterized by magnitudes of the electric and magnetic fields and the angle between them. Analysis of small fluctuations in this background shows that the obtained configuration may be interpreted as a fluid consisting of string-like objects carrying electric and magnetic fields. They are stretched along one direction and the rolling tachyon move in a perpendicular direction to the strings. Direction of the propagating waves coincides with that of strings with velocity equal to electric field.

Tachyon kinks on unstable Dp-branes

In the context of tachyon effective theory coupled to Born-Infeld electromagnetic fields, we obtain all possible singularity-free static flat configurations of codimension one on unstable Dp-branes. Computed tension and string charge density suggest that the obtained kinks are D(p−1) or D(p−1)F1-branes.

String fluid, tachyon matter, and domain walls

We study classical dynamics of an open string tachyon T of unstable Dp-brane coupled to the gauge field Aμ. In the vacuum with vanishing potential, V = 0, two fluid-like degrees of freedom, string fluid and tachyon matter, survive the tachyon condensation. We offer general analysis of the associated hamiltonian dynamics in arbitrary background. The canonical field equations are organized into two sets, fluid equations of motion augmented by an integrability condition. We show that a large class of motionless and degenerate family of classical solutions exist and represent arbitrary transverse distribution of tachyon matter and flux lines. We further test their stability by perturbing the fluid equation up to the second order. Second half of this note considers possibility of V≠0 in the dynamics. We incorporate V in the hamiltonian equation of motion and consider interaction between domain walls and string fluid. During initial phase of tachyon condensation, topological defect at T = 0 is shown to attract nearby and parallel flux lines. The final state is fundamental strings absorbed and spread in some singular D(p−1) brane soliton. When string fluid is transverse to the domain wall, the latter is known to turn into a smooth solution. We point out that a minimal solution of this sort exists and saturates a BPS energy bound of fundamental string ending on a D(p−1) brane.

Vortex-type half-BPS solitons in Aharony-Bergman-Jafferis-Maldacena theory

We study Aharony-Bergman-Jafferis-Maldacena (ABJM) theory without and with mass deformation. It is shown that maximally supersymmetry preserving, D-term, and F-term mass deformations of single mass parameter are equivalent. We obtain vortex-type halfBPS equations and the corresponding energy bound. For the undeformed ABJM theory, the resulting half-BPS equation is the same as that in supersymmetric Yang-Mills theory and no finite energy regular BPS solution is found. For the mass-deformed ABJM theory, the halfBPS equations for U(2)×U(2) case reduce to the vortex equation in Maxwell-Higgs theory, which supports static regular multi-vortex solutions. In U(N)×U(N) case with N > 2 the nonabelian vortex equation of Yang-Mills-Higgs theory is obtained.

Tachyon tube and supertube

We search for tubular solutions in unstable D3-brane. With critical electric field E = 1, solutions representing supertubes, which are supersymmetric bound states of fundamental strings, D0-branes, and a cylindrical D2-brane, are found and shown to exhibit BPS-like property. We also point out that boosting such a tachyon tube solution generates string flux winding around the tube, resulting in helical electric fluxes on the D2-brane. We also discuss issues related to fundamental string, absence of magnetic monopole, and finally more tachyon tubes with noncritical electric field.

Renormalized Entanglement Entropy Flow in Mass-deformed ABJM Theory

We investigate a mass deformation effect on the renormalized entanglement entropy (REE) near the UV fixed point in (2+1)-dimensional field theory. In the context of the gauge/gravity duality, we use the Lin-Lunin-Maldacena (LLM) geometries corresponding to the vacua of the mass-deformed ABJM theory. We analytically compute the small mass effect for various droplet configurations and show in holographic point of view that the REE is monotonically decreasing, positive, and stationary at the UV fixed point. These properties of the REE in (2+1)-dimensions are consistent with the Zamolodchikov

Coupling between M2-branes and form fields

c

Noncommutative tachyon kinks as D(p−1)-branes from unstable Dp-brane

-function proposed in (1+1)-dimensional conformal field theory.

Interaction between M2-branes and bulk form fields

In the context of low-energy effective theory of multiple M2-branes, we construct the interaction terms between the world-volume fields of M2-branes and the antisymmetric tensor fields of three- and six-forms. By utilizing the compactification procedure, we show coincidence between the dimensionally reduced coupling and the R-R coupling to D-branes in type II string theory. We also discuss that a cubic term proportional to six-form field reproduces the quartic mass-deformation term in the world-volume theory of multiple M2-branes.