K. -I. Izawa

Kyoto University, Kioto, Kyōto, Japan

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Publications (52)190.03 Total impact

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    Takumi Imai · K. -I. Izawa
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    ABSTRACT: We investigate characteristic features of realistic parameter choice for primordial inflation with supersymmetric Higgs inflaton as an example of particle physics inflation model. We discuss constraints from observational results and analyze the degree of fine tuning needed to induce slow-roll inflation for wide range of soft supersymmetry breaking scale. The observed amplitude of density fluctuations implies that the minimal fine tuning for the combined electroweak scale and inflaton flatness predicts the spectral index of 0.950--0.965, which includes the central value from observational data.
    05/2013; DOI:10.1093/ptep/ptu054
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    Takumi Imai · K. -I. Izawa · Yuichiro Nakai
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    ABSTRACT: We consider a novel class of constraints on chiral superfields to obtain supersymmetric nonlinear sigma models in four spacetime dimensions, which strictly combine the internal symmetry breaking with spontaneous supersymmetry breaking. The resultant massless modes can be exclusively Nambu-Goldstone bosons without their complex partners and the goldstino that is charged under the internal symmetry. The massive modes show a peculiar relation among their masses and the scales of symmetry breakings.
    Physics Letters B 07/2012; 717(s 1–3). DOI:10.1016/j.physletb.2012.09.025 · 6.02 Impact Factor
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    K. -I. Izawa · Yuichiro Nakai · Takashi Shimomura
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    ABSTRACT: We propose a supersymmetric extension of the standard model whose Higgs sector induces a spontaneous supersymmetry breaking by itself. Unlike the minimal extension, the current Higgs mass bound can be evaded even at the tree-level without the help of the soft breaking terms due to the usual hidden sector, as is reminiscent of the next to minimal case. We also have a possibly light pseudo-goldstino in our visible sector in addition to extra Higgs particles, both of which stem from supersymmetry breaking dynamics. In such a setup of visible supersymmetry breaking, we may see a part of supersymmetry breaking dynamics rather directly in future experiments.
    Journal of High Energy Physics 01/2011; 2011(3). DOI:10.1007/JHEP03(2011)007 · 6.22 Impact Factor
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    K. -I. Izawa · Taichiro Kugo · Tsutomu T. Yanagida
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    ABSTRACT: We consider supersymmetry breaking models with a purely constant superpotential in supergravity. The supersymmetry breaking is induced for the vanishing cosmological constant. As a hidden mediation sector of supersymmetry breaking, it naturally leads to a split spectrum in supersymmetric standard model. We also point out possible utility of our setup to construct nonlinear sigma model and/or Fayet-Iliopoulos-like term in broken supergravity.
    Progress of Theoretical Physics 08/2010; 125(2). DOI:10.1143/PTP.125.261 · 2.06 Impact Factor
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    K. -I. Izawa · Y Nakai · Ryo Takahashi
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    ABSTRACT: We provide nonlinear realization of supergravity with an arbitrary number of supersymmetries by means of coset construction. The number of gravitino degrees of freedom counts the number of supersymmetries, which will be possibly probed in future experiments. We also consider goldstino embedding in the construction to discuss the relation to nonlinear realization with rigid supersymmetries. Comment: 19 pages
    Physical review D: Particles and fields 03/2010; 82(7). DOI:10.1103/PhysRevD.82.075008 · 4.86 Impact Factor
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    ABSTRACT: A new class of models of dynamical supersymmetry breaking is proposed. The models are based on SU(NC) gauge theories with NF(<NC) flavors of quarks and singlets. Dynamically generated superpotential exhibits runaway behavior. By embedding the models into conformal field theories at high energies, the runaway potential is stabilized by strong quantum corrections to the Kähler potential. The quantum corrections are large but nevertheless can be controlled due to superconformal symmetry of the theories.
    Physical review D: Particles and fields 10/2009; 80(8). DOI:10.1103/PhysRevD.80.085017 · 4.86 Impact Factor
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    M. Ibe · K.-I. Izawa · Y. Nakai
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    ABSTRACT: Strongly coupled semi-direct gauge mediation models of supersymmetry breaking through massive mediators with standard model charges are investigated by means of composite degrees of freedom. Sizable mediation is realized to generate the standard model gaugino masses for a small mediator mass without breaking the Supersymmetry (SUSY) [1] is expected to be a crucial ingredient of basic laws in Nature. It is an attractive possibility that SUSY is broken at low energy within the experimental reach in the near future. Among others, low-energy dynamics with gauge mediation between a hidden sector of SUSY breaking and the visible sector of SUSY standard
    Physical review D: Particles and fields 08/2009; 80(3):035002-035002. DOI:10.1103/PHYSREVD.80.035002 · 4.86 Impact Factor
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    Masahiro Ibe · Izawa K. -I · Yuichiro Nakai
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    ABSTRACT: We study gaugino mass generation in the context of semi-direct gauge mediation models, where the messengers are charged under both the hidden sector and the standard model gauge groups while they do not play important roles in dynamical supersymmetry breaking. We clarify the cancellation of the leading contributions of the supersymmetry breaking effects to the gaugino mass in this class of models in terms of the macroscopic effective theory of the hidden sector dynamics. We also consider how to retrofit the model so that we obtain the non-vanishing leading contribution to the gaugino mass. Comment: 14 pages
    Progress of Theoretical Physics 07/2009; 123(2). DOI:10.1143/PTP.123.237 · 2.06 Impact Factor
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    ABSTRACT: Supersymmetric SU(NC) gauge theories possess runaway-type superpotentials for NF < NC, where NF is the flavor number of massless quarks. We show that the runaway behavior can be stabilized for NF ≃ NC by introducing singlets with the aid of perturbative corrections to the Kähler potential, generating (local) minima It is well known that in a supersymmetric (SUSY) QCD based on an SU(NC) gauge theory with NF flavors of quarks Q and antiquarks ˜ Q [1], the dynamically generated superpotential implies a runaway behavior for NF < NC. In this theory we have SUSYinvariant vacua in the limit of meson fields |Q ˜ Q | → ∞. This is consistent with Witten
    Physics Letters B 02/2009; 677(3-4). DOI:10.1016/j.physletb.2009.05.030 · 6.02 Impact Factor
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    ABSTRACT: We argue that the Polonyi problem can be avoided when our supersymmetrybreaking vacuum is surrounded by many supersymmetric vacua. We construct a dynamical class of supersymmetry-breaking models to demonstrate our point. These Theoretical landscape such as in string/M theory is expected to possess an enormous number of metastable vacua in addition to supersymmetric (SUSY) ones. With such vacua sufficiently long-lived in hand, we are led to suspect that our SUSY-breaking state is indeed metastable.
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    K Hamaguchi · K. -I. Izawa · H Nakajima
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    ABSTRACT: Dynamical models of inflation are given with composite inflatons by means of massive supersymmetric gauge theory. Nearly flat directions and stable massive ones in the potential are identified and slow-roll during inflation is examined. This kind of dynamical inflations may be ubiquitous in fundamental unified theory with supersymmetry, which should contain gauge theories for interactions of elementary particles.
    Physics Letters B 02/2008; 662(2). DOI:10.1016/j.physletb.2008.03.001 · 6.02 Impact Factor
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    K. -I. Izawa · Y. Shinbara
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    ABSTRACT: We address an issue what kind of tuning realizes a flat potential for inflaton in supergravity. We restrict ourselves to the case that inflationary dynamics is not affected by separate supersymmetry-breaking effects, and consider examples of a single chiral superfield as an inflaton with its vacuum of the vanishing cosmological constant. The examples potentially include the cases of Polonyi field or right-handed Slow-roll inflation [1] takes place when the potential is flat enough, which is realized through tuning the form of potential by symmetry or by hand. 1 In non-supersymmetric or supersymmetry-broken 2 cases, the required tuning is rather straightforward to flatten a potential with the kinetic term intact. On the other hand, in the supersymmetry-invariant
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    K. -I. Izawa
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    ABSTRACT: We examine the amount of parameter tuning to make slow-roll inflation marginally eternal by considering an R-invariant chaotic inflation as an example of one-parameter tuning in supergravity. The primordial inflation turns out to be possibly marginal in such a setup.
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    M. Ibe · K.-I. Izawa · Y. Shinbara · T.T. Yanagida
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    ABSTRACT: We consider an inflationary model in the hidden-sector broken supergravity with an effectively large cutoff. The inflaton decay into right-handed neutrinos naturally causes the observed baryon asymmetry of the universe with a reheating temperature low enough to avoid the gravitino overproduction. We emphasize that all the phenomenological requirements from cosmology and particle physics are satisfied in the large-cutoff theory.
    Physics Letters B 02/2006; 637(1-2-637):21-26. DOI:10.1016/j.physletb.2006.04.011 · 6.02 Impact Factor
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    M. Ibe · K.-I. Izawa · Y. Nakayama · Y. Shinbara · T. Yanagida
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    ABSTRACT: We extend our models for conformal sequestering of dynamical supersymmetry breaking with decoupling vectorlike matter in several different ways. These extensions enable us to simplify concrete model building, in particular, rendering large gauge group and ad hoc global symmetry for sequestering unnecessary. Conformal sequestering appears highly natural in such circumstances.
    Physical review D: Particles and fields 02/2006; 73(3):35012-035012. DOI:10.1103/PhysRevD.73.035012 · 4.86 Impact Factor
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    M. Ibe · K.-I. Izawa · Y. Nakayama · Y. Shinbara · T. Yanagida
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    ABSTRACT: We provide, in a framework of vectorlike gauge theories, concrete models for conformal sequestering of dynamical supersymmetry (SUSY) breaking in the hidden sector. If the sequestering is sufficiently strong, anomaly mediation of the SUSY breaking may give dominant contributions to the mass spectrum of SUSY standard model particles, leading to negative slepton masses squared. Thus, we also consider a model with gravitational gauge mediation to circumvent the tachyonic slepton problem in pure anomaly-mediation models.
    Physical review D: Particles and fields 01/2006; 73(1). DOI:10.1103/PhysRevD.73.015004 · 4.86 Impact Factor
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    M. Ibe · K. -I. Izawa · Yu Nakayama · Y. Shinbara · T. Yanagida
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    K. -I. Izawa · Tsutomu Yanagida
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    ABSTRACT: A model of gauge mediation with the gravitino mass of order 1eV is considered to motivate 100TeV colliders. Massive mediators with standard-model and supersymmetry-breaking gauge quantum numbers let low-scale dynamics induce sizable soft masses of the standard-model superpartners. We circumvent potential phenomenological difficulties that such low-scale models tend to cause. Comment: 7 pages
    Progress of Theoretical Physics 01/2005; 114(2). DOI:10.1143/PTP.114.433 · 2.06 Impact Factor
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    M. Ibe · K. -I. Izawa · T Yanagida
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    ABSTRACT: Minimal supergravity mediation of supersymmetry breaking has attracted much attention due to its simplicity, which leads to its predictive power. We consider how Nature possibly realizes minimal supergravity through inflationary selection of the theory. Minimality is impressively consistent with the present observational bounds and it might be tested with the aid of low-energy soft parameters obtained in future experiments. Comment: 18 pages, 5 figures
    Physical review D: Particles and fields 09/2004; 71(3). DOI:10.1103/PhysRevD.71.035005 · 4.86 Impact Factor
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    Noriaki Ikeda · K. -I. Izawa
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    ABSTRACT: We investigate an extension of 2D nonlinear gauge theory from the Poisson sigma model based on Lie algebroid to a model with additional two-form gauge fields. Dimensional reduction of 3D nonlinear gauge theory yields an example of such a model, which provides a realization of Courant algebroid by 2D nonlinear gauge theory. We see that the reduction of the base structure generically results in a modification of the target (algebroid) structure.
    Journal of High Energy Physics 08/2004; DOI:10.1088/1126-6708/2004/09/030 · 6.22 Impact Factor