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Mitsutoshi Fujita

Publications and source records attributed to Mitsutoshi Fujita.

At least 37 records · Page 2Linked to original sources
arXiv2015

Towards a Holographic Bose-Hubbard Model

We present a holographic construction of the large-N Bose-Hubbard model. The model is based on Maxwell fields coupled to charged scalar fields on the AdS2 hard wall. We realize the lobe-shaped phase structure of the Bose-Hubbard model and find that the model admits Mott insulator ground states in the limit of large Coulomb repulsion. In the Mott insulator phases, the bosons are localized on each site. At zero hopping we find that the transitions between Mott insulating phases with different fillings correspond to first order level-crossing phase transitions. At finite hopping we find a holographic phase transition between the Mott phase and a non-homogeneous phase. We then analyze the perturbations of fields around both the Mott insulator phase and inhomogeneous phase. We find almost zero modes in the non-homogeneous phase.

hep-th↗
arXiv2013

Dualities from large N orbifold equivalence in Chern-Simons-matter theories with flavor

We study large N orbifold equivalences involving three-dimensional N=3 and N=4 supersymmetric quiver Chern-Simons-matter theories. The gravity dual of the N=3 Chern-Simons-matter theory is described by AdS4xM7 where the tri-Sasaki manifold M7 is known as the Eschenburg space. We find evidence that a large N orbifold equivalence for the N=4 case continues from the M-theory limit to the weak-coupling limit. For the N=3 case, we find consistent large N equivalences involving a projection changing the nodes of the gauge groups, and also for a projection changing Chern-Simons levels where for the latter projection, the BPS monopole operators behave as expected in large N equivalence. For both cases we show, using the gravity dual, that the critical temperature of the confinement/deconfinement transition does not change and the entropy behaves as expected under the orbifold equivalence. We show that large N orbifold equivalence changing Chern-Simons levels can be explained using the planar equivalence in the mirror dual.

hep-th↗
arXiv2013

From the planar limit to M-theory

The large-N limit of gauge theories has been playing a crucial role in theoretical physics over the decades. Despite its importance, little is known outside the planar limit where the 't Hooft coupling $λ=g_{YM}^2N$ is fixed. In this Letter we consider more general large-N limit --- $λ$ grows with N, e.g., $g_{YM}^2$ is fixed. Such a limit is important particularly in recent attempts to find the nonpertubative formulation of M-theory. Based on various supporting evidence, we propose this limit is essentially identical to the planar limit, in the sense the order of the large-N limit and the strong coupling limit commute. For a wide class of large-N gauge theories, these two limits are smoothly connected, and the analytic continuation from the planar limit is justified. As simple examples, we reproduce a few properties of the six-dimensional N=(2, 0) theory on S^1 from the five-dimensional maximal super Yang-Mills theory, supporting the recent conjecture by Douglas and Lambert et al. that these two theories are identical.

hep-th↗
arXiv2012

A new large-N limit and the planar equivalence outside the planar limit

We consider a new large-N limit, in which the 't Hooft coupling grows with N. We argue that a class of large-N equivalences, which is known to hold in the 't Hooft limit, can be extended to this very strongly coupled limit. Hence this limit may lead to a new way of studying corrections to the 't Hooft limit, while keeping nice properties of the latter. As a concrete example, we describe large-N equivalences between the ABJM theory and its orientifold projection. The equivalence implies that operators neutral under the projection symmetry have the same correlation functions in two theories at large-N. Usual field theory arguments are valid when 't Hooft coupling $λ\sim N/k$ is fixed and observables can be computed by using a planar diagrammatic expansion. With the help of the AdS/CFT correspondence, we argue that the equivalence extends to stronger coupling regions, $N\gg k$, including the M-theory region $N\gg k^5$. We further argue that the orbifold/orientifold equivalences between certain Yang-Mills theories can also be generalized. Such equivalences can be tested both analytically and numerically. Based on calculations of the free energy, we conjecture that the equivalences hold because planar dominance persists beyond the 't Hooft limit.

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arXiv2012

Holographic Entanglement Entropy for d=4 N=2 SCFTs in F-theory

We compute the holographic entanglement entropy in the gravity with higher curvature terms dual to d=4 N=2 SCFTs in F-theory using the method proposed in arXiv:1011.5819. The log term of this entanglement entropy reproduces the A-type anomaly of the dual SCFTs in F- theory using the gravity dual with the higher derivative term, which, using the field redefinition, can be transformed to the Gauss-Bonnet term in the subleading order of a derivative expansion. Our analysis shows that the 1/N^2 correction for the central charges should be produced from the gravity including higher derivative terms up to curvature squared terms. To obtain consistent results, we discuss the holographic c-theorem.

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arXiv2012

SL(2,Z) Action on AdS/BCFT and Hall Conductivities

We study the response of a conserved current to external electromagnetic fields in a holographic system with boundaries using the recently proposed AdS/BCFT (boundary conformal field theory) framework. This, in particular, allows us to extract the Hall current, the Hall conductivity, plus some potentially novel transport coefficients, and relations among them. We also analyze the action of SL(2,Z) duality in the gravity bulk, which acts non-trivially on the conductivity of the BCFT. Finally we consider a type IIA string theory embedding of our setup.

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arXiv2011

Aspects of AdS/BCFT

We expand the results of arXiv:1105.5165, where a holographic description of a conformal field theory defined on a manifold with boundaries (so called BCFT) was proposed, based on AdS/CFT. We construct gravity duals of conformal field theories on strips, balls and also time-dependent boundaries. We show a holographic g-theorem in any dimension. As a special example, we can define a `boundary central charge' in three dimensional conformal field theories and our holographic g-theorem argues that it decreases under RG flows. We also computed holographic one-point functions and confirmed that their scaling property agrees with field theory calculations. Finally, we give an example of string theory embedding of this holography by inserting orientifold 8-planes in AdS(4)xCP(3).

hep-th↗
arXiv2011

Probing AdS Wormholes by Entanglement Entropy

In this paper, we study the Lorentzian AdS wormhole solutions constructed in arXiv:0808.2481 [hep-th]. Each of them is a classical solution interpolating between an AdS space and a flat space in type IIB supergravity. We calculate the holographic entanglement entropy to probe this geometry. Our analysis shows that there exits a mass gap in its holographic dual gauge theory and that the entanglement between the two boundaries is rather suppressed than that we naively expect for wormholes. We also examine the holographic conductivity on a probe D-brane in this spacetime.

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arXiv2011

M5-brane Defect and QHE in AdS_4 x N(1,1)/N=3 SCFT

We study the $d=11$ gravity dual $AdS_4\times N(1,1)$ of the $d=3$ $\mathcal{N}=3$ flavored Chern-Simons-matter (CSM) theory. In the dual gravity side, we analyze the M5-brane making the edge on the boundary of $AdS_4$ and derive the quantized Hall conductivity of the dual gauge theory. In the gauge theory side, this M5-brane intersects the gauge theory at the codimension-one defect.

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arXiv2010

Geometric entropy and third order phase transition in d=4 N=2 SYM with flavor

We analyze the phase structure of $d=4$ $\mathcal{N}=2$ large $N$ SYM theory with flavor on $S^1\times S^3$ by using geometric entropy as an order parameter. We introduce chemical potential conjugate to global U(1) symmetry and find the third order phase transition at finite density by using the geometric entropy as the order parameter. We also find that the geometric entropy at the finite density has an interesting behavior at low temperature and for large $N_f$.

hep-th↗
arXiv2010

BPS operators from the Wilson loop in the 3-dimensional supersymmetric Chern-Simons theory

We consider the small deformation of the point-like Wilson loop in the 3-dimensional $\mathcal{N}=6$ superconformal Chern-Simons theory. By Taylor expansion of the point-like Wilson loop in powers of the loop variables, we obtain the BPS operators that correspond to the excited string states of the dual IIA string theory on the pp wave background. The BPS conditions of the Wilson loop constrain both the loop variables and the forms of the operators obtained in the Taylor expansion.

hep-th↗
arXiv2009

Melting Spectral Functions of the Scalar and Vector Mesons in a Holographic QCD Model

We investigate the finite-temperature spectral functions of heavy quarkonia by using the soft-wall AdS/QCD model. We discuss the scalar, the pseudo-scalar, the vector, and the axial-vector mesons and compare their qualitative features of the melting temperature and growing width. We find that the axial-vector meson melts earlier than the vector meson, while there appears only a slight difference between the scalar and pseudo-scalar mesons which also melt earlier than the vector meson.

hep-ph↗
arXiv2009

Eschenburg space as gravity dual of flavored N=4 Chern-Simons-matter theory

We find 3D flavored N=4 Chern-Simons-matter theory, a kind of N=3 SCFT, has a gravity dual AdS4xM7(t1,t2,t3) where three coprime parameters can be read off according to the number and charge of 5-branes in Type IIB setup. Because M7(t1,t2,t3) has been known in literatures as Eschenburg space, we exploit some of its properties to examine the correspondence between two sides.

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arXiv2009

Fractional Quantum Hall Effect via Holography: Chern-Simons, Edge States, and Hierarchy

We present three holographic constructions of fractional quantum Hall effect (FQHE) via string theory. The first model studies edge states in FQHE using supersymmetric domain walls in N=6 Chern-Simons theory. We show that D4-branes wrapped on CP^1 or D8-branes wrapped on CP^3 create edge states that shift the rank or the level of the gauge group, respectively. These holographic edge states correctly reproduce the Hall conductivity. The second model presents a holographic dual to the pure U(N)_k (Yang-Mills-)Chern-Simons theory based on a D3-D7 system. Its holography is equivalent to the level-rank duality, which enables us to compute the Hall conductivity and the topological entanglement entropy. The third model introduces the first string theory embedding of hierarchical FQHEs, using IIA string on C^2/Z_n.

hep-th↗
arXiv2009

Finite-temperature spectral function of the vector mesons in an AdS/QCD model

We use the soft-wall AdS/QCD model to investigate the finite-temperature effects on the spectral function in the vector channel. The dissociation of the vector meson tower onto the AdS black hole leads to the in-medium mass shift and the width broadening in a way similar to the lattice QCD results for the heavy quarkonium at finite temperature. We also show the momentum dependence of the spectral function and find it consistent with screening in a hot wind.

hep-ph↗
arXiv2008

Disordered Systems and the Replica Method in AdS/CFT

We formulate a holographic description of effects of disorder in conformal field theories based on the replica method and the AdS/CFT correspondence. Starting with $n$ copies of conformal field theories, randomness with a gaussian distribution is described by a deformation of double trace operators. After computing physical quantities, we take the $n \to 0$ limit at the final step. We compute correlation functions in the disordered systems by using the holographic replica method as well as the formulation in the conformal field theory. We find examples where disorder changes drastically the scaling of two point functions. The renormalization group flow of the effective central charge in our disordered systems is also discussed.

hep-th↗
arXiv2008

Non-equilibrium thermodynamics near the horizon and holography

Small perturbations of a black brane are interpreted as small deviations from thermodynamic equilibrium in a dual theory with the AdS/CFT correspondence. In this paper, we calculate hydrodynamics of the dual Yang-Mills theory in the gravity side using membrane paradigm. This method is different from the usual AdS/CFT correspondence and evaluate classical solutions not at boundaries but at the place slightly away from a horizon. There are sound modes or shear modes for gravity perturbation. For sound modes, such calculation at the horizon has not yet been done. Then, we find that boundary stress tensor at the horizon satisfies conservation law in flat space and can represent dissipative parts of stress tensor in the dual theory by holography. Using them, we can read off directly shear and bulk viscosity of the dual theory. Quasinormal modes are solutions to linearized equations obeyed by classical fluctuations of a gravitational background subject to specific boundary conditions and are also gauge-invariant quantities. We use solutions for each fluctuation that compose such quantities and show that quasinormal modes are consistent with the membrane paradigm.

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