arXiv subjects

Changrim Ahn

Publications and source records attributed to Changrim Ahn.

At least 37 records · Page 2Linked to original sources

arXiv2014

On the Renormalization Group Flow in Two Dimensional Superconformal Models

We extend the results on the RG flow in the next to leading order to the case of the supersymmetric minimal models SM_p for p>> 1. We explain how to compute the NS and Ramond fields conformal blocks in the leading order in 1/p and follow the renormalization scheme propsed in [1]. As a result we obtained the anomalous dimensions of certain NS and Ramond fields. It turns out that the linear combination expressing the infrared limit of these fields in term of the IR theory SM_{p-2} is exactly the same as those of the nonsupersymmetric minimal theory.

hep-th↗

arXiv2014

String solutions in AdS_3 x S^3 x T^4 with NS-NS B-field

We develop an approach for solving the string equations of motion and Virasoro constraints in any background which has some (unfixed) number of commuting Killing vector fields. It is based on a specific ansatz for the string embedding. We apply the above mentioned approach for strings moving inAdS_3 x S^3 x T^4 with 2-form NS-NS B-field. We succeeded to find solutions for a large class of string configurations on this background. In particular, we derive dyonic giant magnon solutions in the R_t x S^3 subspace, and obtain the leading finite-size correction to the dispersion relation.

hep-th↗

arXiv2012

Worldsheet S-matrix of beta-deformed SYM

We compute perturbative worldsheet S-matrix of beta-deformed AdS/CFT in the strong and weak `t Hooft coupling limit to compare with exact S-matrix. For the purpose we take near BMN limit of TsT-transformed AdS_5 x S^5 with the twisted boundary condition and compute the S-matrix on worldsheet using light-cone gauge fixed Lagrangian. For the weak coupling side, we compute the S-matrix in the SU(3) sector by applying coordinate Bethe ansatz method to the one-loop dilatation operator obtained from the deformed super Yang-Mills theory. These analysis support the conjectured exact S-matrix in the leading order for both sides of beta-deformed AdS/CFT along with appropriate twisted boundary conditions.

hep-th↗

arXiv2012

Exact S-matrices for AdS_3/CFT_2

We propose exact $S$-matrices for the AdS_3/CFT_2 duality between Type IIB strings on AdS_3 x S^3 x M_4 with M_4=S^3 x S^1 or T^4 and the corresponding two-dimensional conformal field theories. We fix the complete two-particle S-matrices for both those cases of AdS_3/CFT_2, on the basis of the symmetries su(1|1) and su(1|1) x su(1|1), respectively preserved by their vacua. A crucial justification comes from the derivation of the all-loop Bethe ansatz matching exactly the recent conjecture proposed by [1] and [2].

hep-th↗

arXiv2012

OPE in planar QCD from integrability

We consider the operator product expansion of local single-trace operators composed of the self-dual components of the field strength tensor in planar QCD. Using the integrability of the one-loop matrix of anomalous dimensions of such operators, we obtain a determinant expression for certain tree-level structure constants in the OPE.

hep-th↗

arXiv2012

Review of AdS/CFT Integrability: An Overview

This is the introductory chapter of a review collection on integrability in the context of the AdS/CFT correspondence. In the collection we present an overview of the achievements and the status of this subject as of the year 2010.

hep-th↗

arXiv2012

Finite-size effects of beta-deformed AdS_5/CFT_4 at strong coupling

We compute both classical and quantum finite-size corrections at leading order in the strong coupling limit for the (dyonic) giant magnon in the Lunin-Maldacena background. Based on the exact S-martix conjectured for the deformed theory, we generalize the Luscher formula to include twisted boundary conditions and show that the results match with those derived both by finite-size classical solutions of the giant magnon and by algebraic curve analysis.

hep-th↗

arXiv2011

TBA, NLO Luscher correction, and double wrapping in twisted AdS/CFT

The ground-state energy of integrably-twisted theories is analyzed in finite volume. We derive the leading and next-to-leading order (NLO) Lüscher-type corrections for large volumes of the vacuum energy for integrable theories with twisted boundary conditions and twisted S-matrix. We then derive the twisted thermodynamic Bethe ansatz (TBA) equations to describe exactly the ground state, from which we obtain an untwisted Y-system. The two approaches are compared by expanding the TBA equations to NLO, and exact agreement is found. We give explicit results for the O(4) model and for the three-parameter family of $γ$-deformed (non-supersymmetric) planar AdS/CFT model, where the ground-state energy can be nontrivial and can acquire finite-size corrections. The NLO corrections, which correspond to double-wrapping diagrams, are explicitly evaluated for the latter model at six loops.

hep-th↗

arXiv2011

Three-point Correlation functions of Giant magnons with finite size

We compute holographic three-point correlation functions or structure constants of a zero-momentum dilaton operator and two (dyonic) giant magnon string states with a finite-size length in the semiclassical approximation. We show that the semiclassical structure constants match exactly with the three-point functions between two su(2) magnon single trace operators with finite size and the Lagrangian in the large 't Hooft coupling constant limit. A special limit J>>sqrt(lambda) of our result is compared with the relevant result based on the Lüscher corrections.

hep-th↗

arXiv2011

Three-point Correlation Function of Giant Magnons in the Lunin-Maldacena background

We compute semiclassical three-point correlation function, or structure constant, of two finite-size (dyonic) giant magnon string states and a light dilaton mode in the Lunin-Maldacena background, which is the γ-deformed, or TsT-transformed AdS_5 x S_γ^5, dual to N = 1 super Yang-Mills theory. We also prove that an important relation between the structure constant and the conformal dimension, checked for the N = 4 super Yang-Mills case, still holds for the γ-deformed string background.

hep-th↗

arXiv2011

Finite-size Giant Magnons on AdS_4 x CP^3_γ

We investigate finite-size giant magnons propagating on γ-deformed AdS_4 x CP^3_γ type IIA string theory background, dual to one parameter deformation of the N=6 super Chern-Simoms-matter theory. Analyzing the finite-size effect on the dispersion relation, we find that it is modified compared to the undeformed case, acquiring γdependence.

hep-th↗

arXiv2011

From Asymptotic Safety to Dark Energy

We consider renormalization group flow applied to the cosmological dynamical equations. A consistency condition arising from energy-momentum conservation links the flow parameters to the cosmological evolution, restricting possible behaviors. Three classes of cosmological fixed points for dark energy plus a barotropic fluid are found: a dark energy dominated universe, which can be either accelerating or decelerating depending on the RG flow parameters, a barotropic dominated universe where dark energy fades away, and solutions where the gravitational and potential couplings cease to flow. If the IR fixed point coincides with the asymptotically safe UV fixed point then the dark energy pressure vanishes in the first class, while (only) in the de Sitter limit of the third class the RG cutoff scale becomes the Hubble scale.

astro-ph.CO↗

arXiv2011

Review of AdS/CFT Integrability, Chapter III.2: Exact world-sheet S-matrix

We review the derivation of the S-matrix for planar N=4 supersymmetric Yang-Mills theory and type IIB superstring theory on an AdS5xS5 background. After deriving the S-matrix for the su(2) and su(3) sectors at the one-loop level based on coordinate Bethe ansatz, we show how su(2|2) symmetry leads to the exact asymptotic S-matrix up to an overall scalar function. We then briefly review the spectrum of bound states by relating these states to simple poles of the S-matrix. Finally, we review the derivation of the asymptotic Bethe equations, which can be used to determine the asymptotic multiparticle spectrum.

hep-th↗

arXiv2011

Twisted Bethe equations from a twisted S-matrix

All-loop asymptotic Bethe equations for a 3-parameter deformation of AdS5/CFT4 have been proposed by Beisert and Roiban. We propose a Drinfeld twist of the AdS5/CFT4 S-matrix, together with c-number diagonal twists of the boundary conditions, from which we derive these Bethe equations. Although the undeformed S-matrix factorizes into a product of two su(2|2) factors, the deformed S-matrix cannot be so factored. Diagonalization of the corresponding transfer matrix requires a generalization of the conventional algebraic Bethe ansatz approach, which we first illustrate for the simpler case of the twisted su(2) principal chiral model. We also demonstrate that the same twisted Bethe equations can alternatively be derived using instead untwisted S-matrices and boundary conditions with operatorial twists.

hep-th↗

arXiv2010

Higher Equations of Motion in N=2 Superconformal Liouville Field Theory

We present an infinite set of higher equations of motion in N=2 supersymmetric Liouville field theory. They are in one to one correspondence with the degenerate representations and are enumerated in addition to the U(1) charge ωby the positive integers m or (m,n) respectively. We check that in the classical limit these equations hold as relations among the classical fields.

hep-th↗

arXiv2010

Finite-size effect for four-loop Konishi of the beta-deformed N=4 SYM

We propose that certain twists of the su(2|2) S-matrix elements describe the beta-deformation of N=4 supersymmetric Yang-Mills theory. We compute the perturbative four-loop anomalous dimension of the Konishi operator of the deformed gauge theory from the Luscher formula based on these twisted S-matrix elements. The result agrees exactly with the perturbative gauge theory computations.

hep-th↗

arXiv2010

Quantum finite-size effects for dyonic magnons in the AdS_4 x CP^3

We compute quantum corrections to finite-size effects for various dyonic giant magnons in the AdS_4 x CP^3 in two different approaches. The off-shell algebraic curve method is used to quantize the classical string configurations in semi-classical way and to compute the corrections to the string energies. These results are compared with the F-term Lüscher formula based on the S-matrix of the AdS_4 / CFT_3. The fact that the two results match exactly provides another stringent test for the all-loop integrability conjecture and the exact S-matrix based on it.

hep-th↗

arXiv2010

Finite-Size Dyonic Giant Magnons in TsT-transformed $AdS_5\times S^5$

We investigate dyonic giant magnons propagating on $γ$-deformed $AdS_5\times S^5$ by Neumann-Rosochatius reduction method with a twisted boundary condition. We compute finite-size effect of the dispersion relations of dyonic giant magnons which generalizes the previously known case of the giant magnons with one angular momentum found by Bykov and Frolov.

hep-th↗