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Yoonbai Kim

Publications and source records attributed to Yoonbai Kim.

At least 37 records · Page 2Linked to original sources

Mass-deformed ABJM Theory and LLM Geometries: Exact Holography

We present a detailed account and extension of our claim in arXiv:1610.01490. We test the gauge/gravity duality between the ${\cal N} = 6$ mass-deformed ABJM theory with U$_k(N)\times$U$_{-k}(N)$ gauge symmetry and the 11-dimensional supergravity on LLM geometries with SO(4)/${\mathbb Z}_k$ $\times$SO(4)/${\mathbb Z}_k$ isometry, in the large $N$ limit. Our analysis is based on the evaluation of vacuum expectation values of chiral primary operators from the supersymmetric vacua of mass-deformed ABJM theory and from the implementation of Kaluza-Klein holography to the LLM geometries. We focus on the chiral primary operator with conformal dimension $Δ= 1$. We show that $\langle {\cal O}^{(Δ=1)}\rangle= N^{\frac32} \, f_{(Δ=1)}$ for all supersymmetric vacuum solutions and LLM geometries with $k=1$, where the factor $f_{(Δ)}$ is independent of $N$. We also confirm that the vacuum expectation value of the the energy momentum tensor is vanishing as expected by the supersymmetry. We extend our results to the case of $k\ne 1$ for LLM geometries represented by rectangular-shaped Young-diagrams. In analogy with the Coulomb branch of the ${\cal N} = 4$ super Yang-Mills theory, we argue that the discrete Higgs vacua of the mABJM theory as well as the corresponding LLM geometries are parametrized by the vevs of the chiral primary operators.

hep-th↗

Exact Holography of the Mass-deformed M2-brane Theory

We test the holographic relation between the vacuum expectation values of gauge invariant operators in ${\cal N} = 6$ ${\rm U}_k(N)\times {\rm U}_{-k}(N)$ mass-deformed ABJM theory and the LLM geometries with $\mathbb{Z}_k$ orbifold in 11-dimensional supergravity. To do that, we apply the Kaluza-Klein reduction to construct a 4-dimensional gravity theory and implement the holographic renormalization procedure. We obtain an exact holographic relation for the vacuum expectation values of the chiral primary operator with conformal dimension $Δ= 1$, which is given by $\langle {\cal O}^{(Δ=1)}\rangle= N^{\frac32} \, f_{(Δ=1)}$, for large $N$ and $k=1$. Here factor $f_{(Δ)}$ is independent of $N$. Our results involve infinite number of exact dual relations for all possible supersymmetric Higgs vacua and so provide a nontrivial test of gauge/gravity duality away from the conformal fixed point. We also extend our results to the case of $k\ne 1$ for LLM geometries represented by rectangular-shaped Young-diagrams.

hep-th↗

Abelian Gauge Invariance of the WZ-type Coupling in ABJM Theory

We construct the interaction terms between the worldvolume fields of multiple M2-branes and 3-form gauge field of 11-dimensional supergravity, in the context of ABJM theory. The obtained Wess-Zumino-type coupling is simultaneously invariant under the U$_{\textrm{L}}(N)\times$U$_{\textrm{R}}(N)$ non-Abelian gauge transformation of the ABJM theory and the Abelian gauge transformation of the 3-form field in 11-dimensional supergravity.

hep-th↗

Two-field inflation with non-minimal coupling

Motivated by the recent `Higgs-inflation' scenario based on a single inflaton field, we consider more generic two-field inflation with non-minimal coupling term. The generic analytic expressions are derived for cosmological observables with the product-separable as well as additive-separable potentials when the non-minimal coupling term is dominated by one of the two fields. A hybrid model of the inflaton potential $V=μ^2 ϕ^2 \left[1+\cos(χ/σ)\right]$ with a non-minimal coupling $K=αϕ$, which guarantees the flatness, is closely examined as a concrete example. Compared to the minimal model with $K=0$, the non-minimal model is shown to provide better fit to the recent cosmological observation by WMAP9 and Planck2013 with the relatively lower field values during the inflationary epoch. Most interestingly, a small value of tensor-to-scalar ratio requires a large non-minimal coupling in our scenario. The model produces non-observably small non-Gaussianity in most of parameter space while a large non-Gaussianity($\sim {\mathcal O}(10)$) is obtainable only when the inflation takes place in a limited field space along the top of the potential.

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Abelian Projections of the Mass-deformed ABJM theory and Weakly Curved Dual Geometry

We construct ${\cal N}=2,4$ supersymmetric abelian projections of the ${\cal N}=6$ mass-deformed ABJM theory. There are well-defined dual background geometries for the ${\cal N}=2$ abelian theory, while those geometries are unclear for the ${\cal N}=4$ abelian theory. The ${\cal N}=2$ theory is built on the supersymmetric vacua of the mass-deformed ABJM theory, which are proven to have one-to-one correspondence with the ${\mathbb Z}_k$ quotient of Lin-Lunin-Maldacena geometries. We select one special vacuum of the mass-deformed ABJM theory and show that the corresponding geometry is weakly curved at every point of the entire space transverse to the M2-branes in the large $N$ limit.

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BPS Vortices, $Q$-balls, and $Q$-vortices in ${\cal N}=6$} Chern-Simons Matter Theory

We investigate the vortex-type BPS equations in the ABJM theory without and with mass-deformation. We systematically classify the BPS equations in terms of the number of supersymmetry and the R-symmetries of the undeformed and mass-deformed ABJM theories. For the undeformed case, we analyze the ${\cal N}=2$ BPS equations for U(2)$\times$U(2) gauge symmetry and obtain a coupled differential equation which can be reduced to either Liouville- or Sinh-Gordon-type vortex equations according to the choice of scalar functions. For the mass-deformed case with U($N$)$\times$U($N$) gauge symmetry, we obtain some number of pairs of coupled differential equations from the ${\cal N}=1,2$ BPS equations, which can be reduced to the vortex equations in Maxwell-Higgs theory or Chern-Simons matter theories as special cases. We discuss the solutions. In ${\cal N}=3$ vortex equations Chern-Simons-type vortex equation is not allowed. We also show that ${\cal N}=\frac52, \frac32, \frac12$ BPS equations are equivalent to those with higher integer supersymmetries.

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Partially Supersymmetric ABJM Theory with Flux

Starting with generic Wess-Zumino type coupling to constant four-form and the dual seven-form field strengths in the ABJM theory, we obtain mass-deformed theories with ${\cal N}=2,4$ supersymmetries. These theories contain massless scalar fields and allow the implementation of the Mukhi-Papageorgakis Higgsing procedure. Using this procedure, we connect the Higgsed theories to three-dimensional mass-deformed SYM theories. These are also connected by the four-dimensional ${\cal N}=1^*,2^*$ mass-deformed SYM theories through dimensional reduction. We classify the three-dimensional mass-deformed SYM theories of ${\cal N}=1,2,4$ supersymmetry, of which a few cases of ${\cal N}=1,2$ are connected neither by MP Higgsing procedure nor dimensional reduction.

hep-th↗

Angle Dependence of Landau Level Spectrum in Twisted Bilayer Graphene

In the context of the low energy effective theory, the exact Landau level spectrum of quasiparticles in twisted bilayer graphene with small twist angle is analytically obtained by spheroidal eigenvalues. We analyze the dependence of the Landau levels on the twist angle to find the points, where the two-fold degeneracy for twist angles is lifted in the nonzero modes and below/above which massive/massless fermion pictures become valid. In the perpendicular magnetic field of 10\,T, the degeneracy is removed at $θ_{\rm deg}\sim 3^\circ$ %angles around 3 degrees for a few low levels, specifically, $θ_{\rm deg}\simeq 2.56^\circ$ for the first pair of nonzero levels and $θ_{\rm deg}\simeq 3.50^\circ$ for the next pair. Massive quasiparticle appears at $θ<θ_{\rm c}\simeq 1.17^\circ$ in 10\,T, %angles less than 1.17 degrees. which match perfectly with the recent experimental results. Since our analysis is applicable to the cases of arbitrary constant magnetic fields, we make predictions for the same experiment performed in arbitrary constant magnetic fields, e.g., for B=40\,T we get $θ_{\rm c}\simeq 2.34^\circ$ and the sequence of angles $θ_{\rm deg} = 5.11, 7.01, 8.42,...$ for the pairs of nonzero energy levels. The symmetry restoration mechanism behind the massive/massless transition is conjectured to be a tunneling (instanton) in momentum space.

cond-mat.mes-hall↗

Mass-Deformed Super Yang-Mills Theories from M2-Branes with Flux

We consider $(2+1)$-dimensional mass-deformed SYM theories and their M-theory origin. These are obtained from MP Higgsing of ABJM theory with constant flux and fixing the mass terms via supersymmetry completion. Depending on the choice of the flux, we obtain ${\cal N}=1$, ${\cal N}=2$, and ${\cal N}=4$ mass-deformed SYM theories. For each of these cases we solve the vacuum equation and obtain the fuzzy two sphere solution for the first two cases. We also discuss the D-brane interpretation of the obtained mass-deformed SYM theories.

hep-th↗

Hyperbolic Inflation

We propose a natural scenario for the cosmological inflation with the non-minimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily accompany with the low Kaluza-Klein scale so that the model allows a single field inflation with a scale around $10^{13}$ GeV. The model fulfills all the observed data and predicts a sizable gravitational perturbation, r~0.003.

hep-ph↗

Constraints on Flows in Horava-Lifshitz Gravity by Classical Solutions

We find exact static stringy solutions of Horava-Lifshitz gravity with the projectability condition but imposing the detailed balance condition near the UV fixed point, and propose a method on constraining the possible pattern of flows in Horava-Lifshitz gravity by using the obtained classical solutions. In the obtained vacuum solutions, the parameters related to the speed of the graviton and the coefficients of quartic spatial derivative terms lead to intriguing effects: the change of graviton speed yields a surplus angle and the quartic derivatives make the square of effective electric charge negative. The result of a few tests based on the geometries of a cone, an excess cone, a black string, and a charged (black) string seems suggestive. For example, the flow of constant graviton speed and variable Newton's coupling can be favored in the vicinity of IR fixed point, but the conclusion is indistinct and far from definite yet. Together with the numerous classical solutions, static or time-dependent, which have already been found, the accumulated data from various future tests will give some hints in constraining the flow patterns more deterministic.

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Interaction between M2-branes and Bulk Form Fields

We construct the interaction terms between the world-volume fields of multiple M2-branes and the 3- and 6-form fields in the context of ABJM theory with U($N$)$\times$U($N$) gauge symmetry. A consistency check is made in the simplest case of a single M2-brane, i.e, our construction matches the known effective action of M2-brane coupled to antisymmetric 3-form field. We show that when dimensionally reduced, our couplings coincide with the effective action of D2-branes coupled to R-R 3- and 5-form fields in type IIA string theory. We also comment on the relation between a coupling with a specific 6-form field configuration and the supersymmetry preserving mass deformation in ABJM theory.

hep-th↗

Surplus Angle and Sign-flipped Coulomb Force in Projectable Horava-Lifshitz Gravity

We obtain the static spherically symmetric vacuum solutions of Horava-Lifshitz gravity theory, imposing the detailed balance condition only in the UV limit. We find the solutions in two different coordinate systems, the Painlevé-Gullstrand coordinates and the Poincare coordinates, to examine the consequences of imposing the projectability condition. The solutions in two coordinate systems are distinct due to the non-relativistic nature of the HL gravity. In the Painleve-Gullstrand coordinates complying with the projectability condition, the solution involves an additional integration constant which yields surplus angle and implies attractive Coulomb force between same charges.

hep-th↗

Landau problem for bilayer graphene: Exact results

We consider graphene bilayer in a constant magnetic field of arbitrary orientation (i.e. tilted with respect to the graphene plane). In the low energy approximation to tight binding model with Peierls substitution, we find the exact spectrum of Landau levels. This spectrum is two-fold degenerate in the limit of large in-plane field, which gives rise to a new SU(2) symmetry in this limit.

cond-mat.mes-hall↗

Surplus Solid Angle as an Imprint of Horava-Lifshitz Gravity

We consider the electrostatic field of a point charge coupled to Horava-Lifshitz gravity and find an exact solution describing the space with a surplus (or deficit) solid angle. Although, theoretically in general relativity, a surplus angle is hardly to be obtained in the presence of ordinary matter with positive energy distribution, it seems natural in Horava-Lifshitz gravity. We present the sudden disappearance and reappearance of a star image as an astrophysical effect of a surplus angle. We also consider matter configurations of all possible power law behaviors coupled to Horava-Lifshitz gravity and obtain a series of exact solutions.

hep-th↗

Vortex-type Half-BPS Solitons in ABJM 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 half-BPS 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 half-BPS equations for U(2)xU(2) case reduce to the vortex equation in Maxwell-Higgs theory, which supports static regular multi-vortex solutions. In U(N)xU(N) case with N>2 the nonabelian vortex equation of Yang-Mills-Higgs theory is obtained.

hep-th↗

Coupling between M2-branes and 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.

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