arXiv subjects

Kazunori Takenaga

Publications and source records attributed to Kazunori Takenaga.

At least 37 records · Page 2Linked to original sources

arXiv2006

Effects of Bulk Mass in Gauge-Higgs Unification

We study effects of bulk mass on electroweak symmetry breaking and Higgs mass in the scenario of five dimensional SU(3) gauge-Higgs unification defined on M^4\times S^1/Z_2. The asymptotic form of effective potential for the Higgs field is obtained, from which a transparent and useful expression for the Higgs mass is found. The small vacuum expectation values (VEV) for Higgs field can be realized by choosing bulk mass parameters approriately for a fixed set of matter content. The bulk mass for periodic fermion field, in general, has effects to make the Higgs mass less heavy. On the other hand, the bulk mass for antiperiodic field does not directly affect the Higgs mass, but it contributes to increase or decrease the Higgs mass, depending on how small the VEV is induced due to the antiperiodic field. We give numerical examples to confirm these effects, in which the role of the bulk mass is also definitely clear.

hep-ph↗

arXiv2005

Extended supersymmetry and its reduction on a circle with point singularities

We investigate $N$-extended supersymmetry in one-dimensional quantum mechanics on a circle with point singularities. For any integer $n$, $N=2n+1$ supercharges are explicitly constructed in terms of discrete transformations, and a class of singularities compatible with supersymmetry is clarified. In our formulation, the supersymmetry can be reduced to $M$-extended supersymmetry for any integer $M<N$. The degeneracy of the spectrum and spontaneous supersymmetry breaking are also studied.

hep-th↗

arXiv2005

Effective Potential of Super Yang-Mills theory on M^4\times S^1 and related topics

We study the gauge symmetry breaking of an ${\cal N}=1$ supersymmetric Yang-Mills theory defined on $M^4\times S^1$, taking correctly account of the vacuum expectation values for the adjoint scalar field $\vevΣ$ in vector multiplet in addition to the Wilson line phases $\vev{A_y}$. We evaluate the one-loop effective potential and obtain the vacuum configuration, for which an SU(N) gauge symmetry is not broken. In case of an orbifold $S^1/Z_2$, under appropriate orbifolding boundary conditions, two Higgs doublets are embedded in the zero modes, $A_y^{(0)}$ and $Σ^{(0)}$. We point out that the tree-level scalar potential resulted from the covariant derivative for the adjoint scalar field is identical to the $D$-term of the MSSM. We also briefly mention the mass spectra of the gauge and Higgs sector in the theory.

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arXiv2005

Aspects of Phase Transition in Gauge-Higgs Unification at Finite Temperature

We study the phase transition in gauge-Higgs unification at finite temperature. In particular, we obtain the strong first order electroweak phase transition for a simple matter content yielding the correct order of Higgs mass at zero temperature. Two stage phase transition is found for a particular matter content, which is the strong first order at each stage. We further study supersymmetric gauge models with the Scherk-Schwarz supersymmetry breaking. We again observe the first order electroweak phase transition and multi stage phase transition.

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arXiv2005

Higgs mass in the gauge-Higgs unification

The gauge-Higgs unification theory identifies the zero mode of the extra dimensional component of the gauge field as the usual Higgs doublet. Since this degree of freedom is the Wilson line phase, the Higgs does not have the mass term nor quartic coupling at the tree level. Through quantum corrections, the Higgs can take a vacuum expectation value, and its mass is induced. The radiatively induced mass tends to be small, although it can be lifted to ${\mathcal O}(100)$ GeV by introducing the ${\mathcal O}(10)$ numbers of bulk fields. Perturbation theory becomes unreliable when a large number of bulk fields are introduced. We reanalyze the Higgs mass based on useful expansion formulae for the effective potential and find that even a small number of bulk field can have the suitable heavy Higgs mass. We show that a small (large) number of bulk fields are enough (needed) when the SUSY breaking mass is large (small). We also study the case of introducing the soft SUSY breaking scalar masses in addition to the Scherk-Schwarz SUSY breaking and obtain the heavy Higgs mass due to the effect of the scalar mass.

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arXiv2005

Correct Effective Potential of Supersymmetric Yang-Mills Theory on M^4\times S^1

We study an ${\cal N}=1$ supersymmetric Yang-Mills theory defined on $M^4\times S^1$. The vacuum expectation values for adjoint scalar field in vector multiplet, though important, has been overlooked in evaluating one-loop effective potential of the theory. We correctly take the vacuum expectation values into account in addition to the Wilson line phases to give an expression for the effective potential, and gauge symmetry breaking is discussed. In evaluating the potential, we employ the Scherk-Schwarz mechanism and introduce bare mass for gaugino in order to break supersymmetry. We also obtain masses for the scalars, the adjoint scalar, and the component gauge field for the $S^1$ direction in case of the SU(2) gauge group. We observe that large supersymmetry breaking gives larger mass for the scalar. This analysis is easily applied to the $M^4\times S^1/Z_2$ case.

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arXiv2004

Dynamical Gauge-Higgs Unification in the Electroweak Theory

$SU(2)_L$ doublet Higgs fields are unified with gauge fields in the $U(3)_s \times U(3)_w$ model of Antoniadis, Benakli and Quirós' on the orbifold $M^4 \times (T^2/Z_2)$. The effective potential for the Higgs fields (the Wilson line phases) is evaluated. The electroweak symmetry is dynamically broken to $U(1)_{EM}$ by the Hosotani mechanism. There appear light Higgs particles. There is a phase transition as the moduli parameter of the complex structure of $T^2$ is varied.

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arXiv2004

Partial Gauge Symmetry Breaking via Bare Mass

We study gauge symmetry breaking patterns in supersymmetric gauge models defined on $M^4\times S^1$. Instead of utilizing the Scherk-Schwarz mechanism, supersymmetry is broken by bare mass terms for gaugino and squarks. Though the matter content is the same, depending on the magnitude of the bare mass, the gauge symmetry breaking patterns are different. We present two examples, in one of which the partial gauge symmetry breaking $SU(3)\to SU(2)\times U(1)$ is realized.

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arXiv2004

Dynamical Gauge Symmetry Breaking and Mass Generation on the Orbifold T^2/Z_2

Dynamical gauge symmetry breaking on the orbifold $T^2/Z_2$ is shown to occur through quantum dynamics of Wilson line phases. Different sets of boundary conditions on $T^2/Z_2$ can be related to each other by Wilson line phases, forming equivalence classes. The effective potential for Wilson line phases is evaluated at the one loop level in SU(2) gauge theory. Depending on the fermion content, the SU(2) symmetry can be broken either completely or partially to U(1) without introducing additional Higgs scalar fields. When SU(2) is completely broken, each of three components of the gauge fields may acquire a distinct mass. Masses are generated through the combination of $T^2$ twists and dynamics of Wilson line phases.

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arXiv2003

Supersymmetry and discrete transformations on S^1 with point singularities

We investigate N-extended supersymmetry in one-dimensional quantum mechanics on a circle with point singularities. For any integer n, N=2n supercharges are explicitly constructed and a class of point singularities compatible with supersymmetry is clarified. Key ingredients in our construction are n sets of discrete transformations, each of which forms an su(2) algebra of spin 1/2. The degeneracy of the spectrum and spontaneous supersymmetry breaking are briefly discussed.

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arXiv2003

Effect of Bare Mass on the Hosotani Mechanism

It is pointed out that the existence of bare mass terms for matter fields changes gauge symmetry patterns through the Hosotani mechanism. As a demonstration, we study an SU(2) gauge model with massive adjoint fermions defined on $M^4\otimes S^1$. It turns out that the vacuum structure changes at certain critical values of $mL$, where $m~(L)$ stands for the bare mass (the circumference of $S^1$). The gauge symmetry breaking patterns are different from models with massless adjoint fermions. We also consider a supersymmmetric SU(2) gauge model with adjoint hypermultiplets, in which the supersymmetry is broken by bare mass terms for the gaugino and squark fields instead of the Scherk-Schwarz mechanism.

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arXiv2003

Phase Structures of SU(N) Gauge-Higgs Models on Multiply Connected Spaces

We study an SU(N) gauge-Higgs model with N_F massless fundamental fermions on M^3 \otimes S^1. The model has two kinds of order parameters for gauge symmetry breaking: the component gauge field for the S^1 direction (Hosotani mechanism) and the Higgs field (Higgs mechanism). We find that the model possesses three phases called Hosotani, Higgs and coexisting phases for N=odd, while for N=even, the model has only two phases, the Hosotani and coexisting phases. The phase structure depends on a parameter of the model and the size of the extra dimension. The critical radius and the order of the phase transition are determined. We also consider the case that the representation of matter fields under the gauge group is changed. We find some models, in which there is only one phase, independent of parameters of the models as well as the size of the extra dimension.

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arXiv2003

Supersymmetry in quantum mechanics with point interactions

We investigate supersymmetry in one-dimensional quantum mechanics with point interactions. We clarify a class of point interactions compatible with supersymmetry and present N=2 supersymmetric models on a circle with two point interactions as well as a superpotential. A hidden su(2) structure inherent in the system plays a crucial role to construct the N=2 supercharges. Spontaneous breaking of supersymmetry due to point interactions and an extension to higher N-extended supersymmetry are also discussed.

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arXiv2002

Gauge Symmetry Breaking through the Hosotani Mechanism in Softly Broken Supersymmetric QCD

Gauge symmetry breaking through the Hosotani mechanism (the dynamics of nonintegrable phases) in softly broken supersymmetric QCD with $N_F^{fd}$ flavors is studied. For $N=$ even, there is a single SU(N) symmetric vacuum state, while for $N=$ odd, there is a doubly degenerate SU(N) symmetric vacuum state in the model. We also study generalized supersymmetric QCD by adding $N_F^{adj}$ numbers of massless adjoint matter. The gauge symmetry breaking pattern such as $SU(3)\to SU(2)\times U(1)$ is possible for appropriate choices of the matter content and values of the supersymmetry breaking parameter. The massless state of the adjoint Higgs scalar is also discussed in the models.

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arXiv2002

Multi-phases in gauge theories on non-simply connected spaces

It is pointed out that phase structures of gauge theories compactified on non-simply connected spaces are not trivial. As a demonstration, an SU(2) gauge model on $M^3\otimes S^1$ is studied and is shown to possess three phases: Hosotani, Higgs and coexisting phases. The critical radius and the order of the phase transitions are explicitly determined. A general discussion about phase structures for small and large scales of compactified spaces is given. The appearance of phase transitions suggests a GUT scenario in which the gauge hierarchy problem is replaced by a dynamical problem of how to stabilize a radius of a compactified space in close vicinity to a critical radius.

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arXiv1999

Many-Brane Extention of the Randall-Sundrum Solution

Recently, Randall and Sundrum proposed a static solution to Einstein's equations in five spacetime dimensions with two 3-branes located at the fixed points of $S^1/Z_2$ to solve the hierarchy problem. We extend the solution and construct static and also inflationary solutions to Einstein's equations in five spacetime dimensions, one of which is compactified on $S^1$, with any number of 3-branes whose locations are taken to be arbitrary. We discuss how the hierarchy problem can be explained in our model.

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arXiv1999

Confinement, Chiral Symmetry Breaking and Faddeev-Niemi Decomposition in QCD

We identify two distinct, complementary gauge field configurations for QCD with SU(2) gauge group, one (instanton-like configurations) having to do with chiral symmetry breaking but not with confinement, the other (regularized Wu-Yang monopoles) very likely responsible for confinement but unrelated to chiral symmetry breaking. Our argument is based on a semiclassical analysis of fermion zero modes in these backgrounds, made by use of a gauge field decomposition recently introduced by Faddeev and Niemi. Our result suggests that the two principal dynamical phenomena in QCD, confinement and chiral symmetry breaking, are distinct effects, caused by two competing classes of gauge field configurations.

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arXiv1998

Supersymmetry Breaking through Boundary Conditions Associated with the $U(1)_{R}$

The effects of boundary conditions of the fields for the compactified space directions on the supersymmetric theories are discussed. The boundary conditions can be taken to be periodic up to the degrees of freedom of localized $U(1)_{R}$ transformations. The boundary condition breaks the supersymmery to yield universal soft supersymmetry breaking terms. The 4-dimensional supersymmetric QED with one flavour and the pure supersymmetric QCD are studied as toy models when one of the space coordinates is compactified on $S^1$.

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