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Kazuo Ghoroku

Publications and source records attributed to Kazuo Ghoroku.

At least 55 records · Page 3Linked to original sources
arXiv2005

Flavor quark at high temperature from a holographic model

Gauge theory with light flavor quark is studied by embedding a D7 brane in a deconfinement phase background newly constructed. We find a phase transition by observing a jump of the vacuum expectation value of quark bilinear and also of the derivative of D7 energy at a critical temperature. For the model considered here, we also study quark-antiquark potential to see some possible quark-bound states and other physical quantities in the deconfinement phase.

hep-th↗
arXiv2004

Chiral symmetry breaking driven by dilaton

Dynamical properties of gauge theories with light flavor quarks are studied in a dual supergravity by adding a D7-brane probe into the AdS background deformed by the dilaton. By estimating the vev of flavor quark-bilinear in both the supersymmetric and non-supersymmetric gravity duals, we find spontaneous chiral symmetry breaking in the case of the non-supersymmetric background. We also study quark-antiquark potential for light quarks to see the quark confinement in the models considered here.

hep-th↗
arXiv2004

Radius stabilization and brane running in RS1 model

We study the effective potential of a scalar field based on the 5D gauged supergravity for the RS1 brane model in terms of the brane running method. The scalar couples to the brane such that the BPS conditions are satisfied for the bulk configuration. The resulting effective potential implies that the interbrane distance is undetermined in this case, and we need a small BPS breaking term on the brane to stabilize the interbrane distance at a finite length. We also discuss the relationship to the Goldberger-Wise model.

hep-th↗
arXiv2004

Gauge-gravity correspondence in de Sitter braneworld

We study the braneworld solutions based on a solvable model of 5d gauged supergravity with two scalars of conformal dimension three, which correspond to bilinear operators of fermions in the dual $\mathcal{N}=4$ super Yang-Mills theory on the boundary. An accelerating braneworld solution is obtained when both scalars are taken as the form of deformations of the super Yang-Mills theory and the bulk supersymmetry is broken. This solution is smoothly connected to the Poincare invariant brane in the limit of vanishing cosmological constant. The stability of this brane-solution and the correspondence to the gauge theory are addressed.

hep-th↗
arXiv2004

Stability of RS brane for tachyonic scalars

We study the stability of the RS brane embedded in the AdS$_5$ vacuum of 5d gauged supergravity, where many tachyonic scalars exist. We consider a model in which these scalars couple to the brane such that the BPS conditions are satisfied to preserve the bulk supersymmetric configuration. In this case, we find that these tachyons are not trapped on the brane and only the massless dilaton is localized. As a result, the braneworld is stable. Further, the effective action of trapped fields is studied by using the brane running method developed recently, and we find that the action is independent of the brane position.

hep-th↗
arXiv2003

Effective action and brane running

We address the renormalized effective action for a Randall-Sundrum brane running in 5d bulk space. The running behavior of the brane action is obtained by shifting the brane-position without changing the background and the fluctuations. After an appropriate renormalization, we obtain an effective, low energy braneworld action, in which the effective 4d Planck mass is independent of the running-position. We address some implications of this effective action.

hep-th↗
arXiv2003

Dilaton coupled brane-world and field trapping

We address solutions of brane-world with cosmological constant $λ$ by introducing the dilaton in 5d bulk, and we examine the localization of graviton, gauge bosons and dilaton. For those solutions, we find that both graviton and gauge bosons can be trapped for either sign, positive or negative, and wide range of $λ$ due to the non-trivial dilaton. While the dilaton can not be trapped on the brane.

hep-th↗
arXiv2003

Newton's law in de Sitter brane

Newton potential has been evaluated for the case of dS brane embedded in Minkowski, dS$_5$ and AdS$_5$ bulks. We point out that only the AdS$_5$ bulk might be consistent with the Newton's law from the brane-world viewpoint when we respect a small cosmological constant observed at present universe.

hep-th↗
arXiv2003

Instability of thick brane worlds

We examined 5d thick brane worlds constructed by a real scalar field. The solutions are obtained in terms of a simple form of smooth warp factor. For the case of dS brane, we found a disease of the solutions. For example, it is impossible to construct thick-brane worlds with our simple smoothing. This result is independent of supersymmetry or other symmetries.

hep-th↗
arXiv2003

Gauge symmetry and cosmological constant on a brane

We have examined the localization of gauge bosons on the three-brane embedded in 5D bulk space-time, and we find two kinds of branes on which both graviton and gauge bosons can be trapped. One is the dS brane with a positive cosmological constant, and the other is the one with zero cosmological constant or 4D Minkowski brane. Then, which brane is realized would depend on the observation of the cosmological constant of our world.

hep-th↗
arXiv2003

Scalar field localization on a brane with cosmological constant

We address the localization of a scalar field, whose bulk-mass M is considered in a wide range including the tachyonic region,on a three-brane. The brane with non-zero cosmological constant $λ$ is embedded in five dimensional bulk space. We find in this case that the trapped scalar could have mass $m$ which has an upper bound and expressed as $m^2=m_0^2+αM^2\leq β|λ|$ with the calculable numbers $m_0^2, α, β$. We point out that this result would be important to study the stability of the brane and cosmological problems based on the brane-world.

hep-th↗
arXiv2002

Origin of Small Cosmological Constant in Brane-World

We address the relation among the parameters of accelerating brane-universe embedded in five dimensional bulk space. It is pointed out that the tiny cosmological constant of our world can be obtained as quantum corrections around a given brane-solution in the bulk theory or in the field theory on the boundary from the holographic viewpoint.Some implications to the cosmology and constarints on the parameters are also given.

hep-th↗
arXiv2002

Localization of Gravity on Brane Embedded in $AdS_5$ and $dS_5$

We address the localization of gravity on the Friedmann-Robertson-Walker type brane embedded in either $AdS_{5}$ or $dS_{5}$ bulk space,and derive two definite limits between which the value of the bulk cosmological constant has to lie in order to localize the graviton on the brane.The lower limit implies that the brane should be either $dS_{4}$ or 4d Minkowski in the $AdS_{5}$ bulk.The positive upper limit indicates that the gravity can be trapped also on curved brane in the $dS_{5}$ bulk space.Some implications to recent cosmological scenarios are also discussed.

hep-th↗
arXiv2001

Massive vector trapping as a gauge boson on a brane

We propose a mechanism to trap massive vector fields as a photon on the Randall-Sundrum brane embedded in the five dimensional AdS space. This localization-mechanism of the photon is realized by considering a brane action, to which a quadratic potential of the bulk-vector fields is added. We also point out that this potential gives several constraints on the fluctuations of the vector fields in the bulk space.

hep-th↗
arXiv2001

Stability of Randall-Sundrum brane-world and tachyonic scalar

We address the behaviour of the scalar field with negative mass squared in the five dimensional AdS space where the Randall-Sundrum brane-world is embedded. We point out that the tachyonic scalar allowed in the bulk space destabilizes the embedded brane-world where the cosmological constant is zero. The resolution of this instability is discussed from the viewpoint of AdS/CFT correspondence.

hep-th↗
arXiv2000

Beta-functions in Yang-Mills Theory from Non-critical String

The renormalization group equations of the Yang-Mills theory are examined in the non-critical string theory according to the framework of the holography. Under a simple ansatz for the tachyon, we could find several interesting solutions which are classified by the value of the tachyon potential at the vacuum. We show two typical, asymptotic-free solutions which are different in their infrared behaviors. For both types of solutions, we could obtain quark-confinement potential from the Wilson-loop. The stability of the tachyon and the ZigZag symmetry are also discussed for these solutions.

hep-ph↗
arXiv2000

Nonlinear sigma model and Yang-Mills theory through non-critical string

We consider two-dimensional nonlinear sigma model from the viewpoint of the holography, which has been applied to the study of the Yang-Mills theory, based on the non-critical string theory. We can see the renormalization group flows for both the nonlinear sigma model and the Yang-Mills theory at the same time, and the two theories are intimately related through a kind of dual relation of the coupling constants. We address the running behaviors of these coupling constants and also the asymptotic freedom of the Yang-Mills theory.

hep-th↗