arXiv subjects

Nobuhito Maru

Publications and source records attributed to Nobuhito Maru.

At least 109 records · Page 6Linked to original sources

arXiv2005

Color Superconductivity via Supersymmetry

In this talk, a supersymmetric (SUSY) composite model of color superconductivity is discussed. In this model, quark and diquark supermultiplets are dynamically generated as massless composites by a newly introduced confining gauge dynamics. It is analytically shown that the scalar component of diquark supermultiplets develops vacuum expectation value (VEV) at a certain critical chemical potential. We believe that our model well captures aspects of the diquark condensate behavior and helps our understanding of its dynamics in real QCD. The results obtained here might be useful when we consider a theory composed of quarks and diquarks.

hep-ph↗

arXiv2005

Yukawa Coupling Structure in Intersecting D-brane Models

The structure of Yukawa coupling matrices is investigated in type IIA T^6/(Z_2 x Z_2) orientifold models with intersecting D-branes. Yukawa coupling matrices are difficult to be realistic in the conventional models in which the generation structure emerges by the multiple intersection of D-branes in the factorized T^6 = T^2 x T^2 x T^2. We study the new type of flavor structure, where Yukawa couplings are dynamically generated, and show this type of models lead to nontrivial structures of Yukawa coupling matrices, which can be realistic.

hep-th↗

arXiv2004

Color Superconductivity from Supersymmetry

A supersymmetric composite model of color superconductivity is proposed. Quarks and diquarks are dynamically generated as composite fields by a newly introduced strong gauge dynamics. It is shown that the condensation of the scalar component of the diquark supermultiplet occurs when the chemical potential becomes larger than some critical value. We believe that the model well captures aspects of the diquark condensate behavior and helps our understanding of the diquark dynamics in real QCD. The results obtained here might be useful when we consider a theory composed of quarks and diquarks.

hep-ph↗

arXiv2004

An Attempt to Solve the Hierarchy Problem Based on Gravity-Gauge-Higgs Unification Scenario

We discuss a possible scenario to solve the hierarchy problem, in which 4-dimensional bosonic fields with all possible integer spins, graviton, gauge boson and Higgs are unified in a framework of a gravity theory with extra dimensions. The Higgs is identified with the extra space component of the metric tensor. One-loop quantum effect on the Higgs mass-squared is explicitly calculated in a five dimensional gravity theory compactified on $S^1$. We obtain a finite calculable Higgs mass-squared without suffering from quadratic divergence, by virtue of general coordinate transformation invariance, which is argued to be guaranteed by the summation over all Kaluza-Klein modes running in the loop diagrams.

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arXiv2004

Non-BPS walls and their stability in 5d SUSY theory

We review recent work (hep-th/0404114) on non-BPS domain walls in $5d$ SUSY theory. An exact solution of non-BPS multi-walls is found in supersymmetric massive T*(CP1) model in five dimensions. The non-BPS multi-wall solution is found to have no tachyon. The N=1 supersymmetry preserved on the four-dimensional world volume of one wall is broken by the coexistence of the other wall. The supersymmetry breaking is exponentially suppressed as the distance between the walls increases.

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arXiv2004

Radius Stabilization in a Supersymmetric Warped Compactification

A supersymmetric (SUSY) model of radius stabilization is constructed for the S^1/Z_2 warped compactifications with a hypermultiplet in five dimensions. Requiring the continuity of scalar field across the boundaries, we obtain radius stabilization preserving SUSY, realizing the SUSY extension of the Goldberger-Wise mechanism. Even if we allow discontinuities of the Z_2 odd field across the boundary, we always obtain SUSY preservation but obtain the radius stabilization only when the discontinuity is fixed by other mechanism.

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arXiv2004

Warped Supersymmetric Radius Stabilization

A simple model of extra-dimensional radius stabilization in a supersymmetric Randall-Sundrum model is presented. In our model, we introduce only a bulk hypermultiplet and source terms on each boundary branes. With an appropriate choice of model parameters, we find that the radius can be stabilized by supersymmetric vacuum conditions. Since the radion mass can be much larger than the gravitino mass and the supersymmetry breaking scale, the radius stability is ensured even with the supersymmetry breaking. We find a parameter region where unwanted scalar masses induced by quantum corrections through the bulk hypermultiplet and a bulk gravity multiplet are suppressed and the anomaly mediation contributions dominate.

hep-th↗

arXiv2004

Towards Gravity-Gauge-Higgs Unification

We discuss a possibility to solve the gauge hierarchy problem in the framework of Gravity-Gauge-Higgs Unification scenario. We have calculated 1-loop correction to the mass of the scalar field, which is originated from 55-component of the metric, in five dimensional gravity theory with the bulk scalar field compactified on S^1. It is shown that the quadratic divergences are canceled and the finite mass is generated by explicit diagrammatic calculations and the effective potential calculations.

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arXiv2004

Non-BPS Walls and Their Stability in 5D Supersymmetric Theory

An exact solution of non-BPS multi-walls is found in supersymmetric massive T^\star(\mathbb{CP}^1) model in five dimensions. The non-BPS multi-wall solution is found to have no tachyon. Although it is only metastable under large fluctuations, we can give topological stability by considering a model with a double covering of the T^\star(\mathbb{CP}^1) target manifold. The {\cal N}=1 supersymmetry preserved on the four-dimensional world volume of one wall is broken by the coexistence of the other wall. The supersymmetry breaking is exponentially suppressed as the distance between the walls increases.

hep-th↗

arXiv2004

Localized Gauge Multiplet on a Wall

The localization of vector multiplets is examined using the {\cal N}=1 supersymmetric U(1) gauge theory with the Fayet-Iliopoulos term coupled to charged chiral multiplets in four dimensions. The vector field becomes localized on a BPS wall connecting two different vacua that break the gauge symmetry. The vacuum expectation values of charged fields vanish (approximately) around the center of the wall, causing the Higgs mechanism to be ineffective. The mass of the localized vector multiplet is found to be the inverse width of the wall. The model gives an explicit example of this general phenomenon. A five-dimensional version of the model can also be constructed if we abandon supersymmetry.

hep-th↗

arXiv2004

Supersymmetric Radius Stabilization in Warped Extra Dimensions

We propose a simple model of extra-dimensional radius stabilization in a supersymmetric Randall-Sundrum model. In our model, we introduce only a bulk hypermultiplet and source terms (tadpole terms) on each boundary branes. With appropriate choice of model parameters, we find that the radius can be stabilized by supersymmetric vacuum conditions. Since the radion mass can be much larger than the gravitino mass and even the original supersymmetry breaking scale, radius stability is ensured even in the presence of supersymmetry breaking. We find a parameter region in which unwanted scalar masses induced by quantum corrections through the bulk hypermultiplet and a bulk gravity multiplet are suppressed and the anomaly mediation contribution dominates.

hep-th↗

arXiv2003

Sparticle Masses in Product-Group Gauge Theories

In this paper, we investigate a possibility to cause supersymmetry breaking with background modulus fields in product-group gauge theories. The vacuum expectation values of these moduli are found to satisfy several relations and the moduli dependences of the action are fixed by consistency of the model. With this action, we calculate the mass spectrum of vector and matter multiplets up to one-loop order of perturbation theory. As an application of the result, it is found that various properties of higher-dimensional supersymmetry breaking are well captured in corresponding limits in the moduli space. In particular, we have finite radiative corrections to Higgs masses in the case that is closely related to the boundary condition breaking of supersymmetry.

hep-ph↗

arXiv2003

Fat Branes, Orbifolds and Doublet-Triplet Splitting

A simple higher dimensional mechanism of the doublet-triplet splitting is presented in a five dimensional supersymmetric SU(5) GUT on $S^1/Z_2$. The splitting of multiplets is realized by a mass term of Higgs hypermultiplet which explicitly breaks SU(5) gauge symmetry. Depending on the sign of mass, zero mode Higgs doublets and triplets are localized on the either side of the fixed points. The mass splitting is realized due to the difference of magnitudes of the overlap with a brane localized or a bulk singlet field. No unnatural fine-tuning of parameters is needed. The proton stability is ensured by locality {\em without symmetries}. As well as a conventional mass splitting solution, it is shown that the weak scale Higgs triplet is consistent with the proton stability. This result might provide an alternative signature of GUT in future collider experiments.

hep-ph↗

arXiv2003

Stability and Fluctuations on Walls in N=1 Supergravity

The recently found non-BPS multi-wall configurations in the N=1 supergravity in four dimensions is shown to have no tachyonic scalar fluctuations without additional stabilization mechanisms. Mass of radion (lightest massive fluctuation) is found to be proportional to $Lambda {\rm e}^{-πΛR/2}$, where $Λ$ is the inverse width of the wall and $ R$ is the radius of compactified dimension. We obtain localized massless graviton and gravitino forming a supermultiplet with respect to the Killing spinor. The relation between the bulk energy density and the boundary energy density (cosmological constants) is an automatic consequence of the field equation and Einstein equation. In the limit of vanishing gravitational coupling, the Nambu-Goldstone modes are reproduced.

hep-th↗

arXiv2003

Nonanomalous Discrete R-Symmetry and Light Gravitino

We discuss nonanomalous R-symmetry in the supersymmetric grand unified theories. In particular, we explore anomaly-free solutions predicting the gravitino mass in the range of $10^{-3} eV \lsim m_{3/2} \lsim 1 TeV$ when the $μ$-parameter is fixed to be $μ\simeq 1 TeV$. In the minimal SU(5) GUT, we have shown that $μ\simeq 1 TeV$ is obtained only if the gravitino is ultralight with mass $m_{3/2} \sim 10^{-3} eV$. If extra fields ${\bf 5}\oplus{\bf 5^*}$ or ${\bf 10}\oplus{\bf 10^*}$ are introduced, many solutions predicting $m_{3/2} \gsim 10^{-3} eV$ are found. The R-parity is violated due to the vacuum expectation value of the superpotential, but it is controlled by the discrete R-symmetry. We find that the R-parity violating couplings are naturally suppressed much below the experimental bounds for some charge assignments. These charge assignments predict light gravitino with masses of order ${\cal O}(10^{-3} eV)$--${\cal O}(1 MeV)$. These discrete R-symmetries can be considered as solutions to the $μ$-problem in low energy supersymmetry breaking models such as the gauge mediation.

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arXiv2003

Decoupling and lepton flavor violation in extra dimension

We discuss the fermion mass hierarchy and the flavor mixings in the fat brane scenario of five dimensional SUSY theory. The decoupling solution of the sfermion mass spectrum can be realized by introducing the vector-like mirror fields in an extra dimension. In this scenario, both the left- and right-handed sleptons can have sizable flavor mixings. We point out that this sizable flavor mixings can induce the suitable magnitude of the muon anomalous magnetic moment ($g_μ-2$) within the experimental bounds of lepton flavor violating processes.

hep-ph↗

arXiv2003

Field localization in warped gauge theories

We present four-dimensional gauge theories that describe physics on five-dimensional curved (warped) backgrounds, which includes bulk fields with various spins (vectors, spinors, and scalars). Field theory on the AdS$_5$ geometry is examined as a simple example of our formulation. Various properties of bulk fields on this background, e.g., the mass spectrum and field localization behavior, can be achieved within a fully four-dimensional framework. Moreover, that gives a localization mechanism for massless vector fields. We also consider supersymmetric cases, and show in particular that the conditions on bulk masses imposed by supersymmetry on warped backgrounds are derived from a four-dimensional supersymmetric theory on the flat background. As a phenomenological application, models are shown to generate hierarchical Yukawa couplings. Finally, we discuss possible underlying mechanisms which dynamically realize the required couplings to generate curved geometries.

hep-ph↗

arXiv2003

4D construction of bulk supersymmetry breaking

In this letter, we discuss a four-dimensional model with modulus fields which are responsible for supersymmetry breaking. Given non-trivial moduli dependence of the action, the model is found to give a proper description of higher-dimensional supersymmetry breaking. We explicitly calculate gaugino and scalar mass spectrum and show that several classes of scenarios proposed in the literature are described in certain regions of the parameter space of the moduli vacuum expectation values. The model in other generic regions of the moduli space gives unexplored scenarios (mass spectra) of supersymmetry breaking in four dimensions.

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