Positroid Stratification of Orthogonal Grassmannian and ABJM Amplitudes

A novel understanding of scattering amplitudes in terms of on-shell diagrams and positive Grassmannian has been recently established for four dimensional Yang-Mills theories and three dimensional Chern-Simons theories of ABJM type. We give a detailed construction of the positroid stratification of orthogonal Grassmannian relevant for ABJM amplitudes. On-shell diagrams are classified by pairing of external particles. We introduce a combinatorial aid called `OG tableaux' and map each equivalence class of on-shell diagrams to a unique tableau. The on-shell diagrams related to each other through BCFW bridging are naturally grouped by the OG tableaux. Introducing suitably ordered BCFW bridges and positive coordinates, we construct the complete coordinate charts to cover the entire positive orthogonal Grassmannian for arbitrary number of external particles. The graded counting of OG tableaux suggests that the positive orthogonal Grassmannian constitutes a combinatorial polytope.Comment: 32 pages, 23 figures; v2. minor corrections; v3. several clarifications and minor improvement

Holography of Wrapped M5-branes and Chern-Simons theory

We study three-dimensional superconformal field theories on wrapped M5-branes. Applying the gauge/gravity duality and the recently proposed 3d-3d relation, we deduce quantitative predictions for the perturbative free energy of a Chern-Simons theory on hyperbolic 3-space. Remarkably, the perturbative expansion is expected to terminate at two-loops in the large N limit. We check the correspondence numerically in a number of examples, and confirm the N^3 scaling with precise coefficients.Comment: 5 pages, 2 figures. Some clarifications, references added, misprint correcte

Holography of 3d-3d correspondence at Large N

We study the physics of multiple M5-branes compactified on a hyperbolic 3-manifold. On the one hand, it leads to the 3d-3d correspondence which maps an $\mathcal{N}=2$ superconformal field theory to a pure Chern-Simons theory on the 3-manifold. On the other hand, it leads to a warped AdS$_4$ geometry in M-theory holographically dual to the superconformal field theory. Combining the holographic duality and the 3d-3d correspondence, we propose a conjecture for the large $N$ limit of the perturbative free energy of a Chern-Simons theory on hyperbolic 3-manifold. The conjecture claims that the tree, one-loop and two-loop terms all share the same $N^3$ scaling behavior and are proportional to the volume of the 3-manifold, while the three-loop and higher terms are suppressed at large $N$. Under mild assumptions, we prove the tree and one-loop parts of the conjecture. For the two-loop part, we test the conjecture numerically in a number of examples and find precise agreement. We also confirm the suppression of higher loop terms in a few examples.Comment: 37 pages, 7 figure

AdS_5/CFT_4 Four-point Functions of Chiral Primary Operators: Cubic Vertices

We study the exchange diagrams in the computation of four-point functions of all chiral primary operators in D=4, $\mathcal{N}=4$ Super-Yang-Mills using AdS/CFT correspondence. We identify all supergravity fields that can be exchanged and compute the cubic couplings. As a byproduct, we also rederive the normalization of the quadratic action of the exchanged fields. The cubic couplings computed in this paper and the propagators studied extensively in the literature can be used to compute almost all the exchange diagrams explicitly. Some issues in computing the complete four-point function in the massless sector is discussed.Comment: 15 pages, 1 figure; v2. typos correcte

Symplectic Perturbation Theory in Massive Ambitwistor Space: A Zig-Zag Theory of Massive Spinning Particles

We develop a theory of massive spinning particles interacting with background fields in four spacetime dimensions in which holomorphy and chirality play a central role. Applying a perturbation theory of symplectic forms to the massive twistor space as a K\"ahler manifold, we find that the spin precession behavior of a massive spinning particle is directly determined from the manner in which self-dual and anti-self-dual field strengths permeate into "complex spacetime." Especially, the particle shows the minimally coupled precession behavior if self-dual field strength continues holomorphically into the complex: the Newman-Janis shift. In general, computing the momentum impulse shows that the parameters that control generic non-holomorphic continuations are directly related to the coupling constants in the massive-massive-massless spinning on-shell amplitude of Arkani-Hamed, Huang, and Huang, and thus they are interpreted as the single-curvature Wilson coefficients given by Levi and Steinhoff, redefined on complex worldlines. Finally, exact expressions for Kerr and $\sqrt{\text{Kerr}}$ actions are bootstrapped in monochromatic self-dual plane-wave backgrounds from symplectivity and a matching between classical scattering and the on-shell amplitude, from which we obtain all-order exact impulses of classical observables.Comment: 57 pages, 4 figure

The implications of the People's Liberation Army's modernization for the Republic of Korea's security policy

South Korean security has been threatened by North Korea since the Korean War. The collapse of the Soviet Union has required Northeast Asian regional security to be reconfigured. North Korea remains as South Korea's primary threat. China is emerging rapidly and creating several issues directly and indirectly that are related to South Korea. Especially, China's PLA modernization has been remarkable in its capability and ambition. Therefore, threats imposed by China to South Korea may seem significant. Directly, dispute in Socotra Rock and the Northeast Project impose threats to South Korea. The Taiwan issue and the South China Sea dispute indirectly affect South Korean security due to the involvement of the United States forces in the Northeast Asian region. This thesis will reveal that China's PLA modernization coerces South Korea to confront dilemmas in its security policy. In other words, such modernization is a threat to South Korean security.http://archive.org/details/theimplicationso109454415Republic of Korea Navy author