Muneto Nitta

Publications (6)0 Total impact

• Source

  Available from: ArXiv

  Article: Gauge symmetry breaking in ten-dimensional Yang-Mills theory dynamically compactified on S^6

  Pravabati Chingangbam, Hironobu Kihara, Muneto Nitta
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  ABSTRACT: We study fluctuation modes in ten-dimensional Yang-Mills theory with a higher derivative term for the gauge field. We consider the ten-dimensional space-time to be a product of a four-dimensional space-time and six-dimensional sphere which exhibits dynamical compactification. Because of the isometry on S^6, there are flat directions corresponding to the Nambu-Goldstone zero modes in the effective theory on the solution. The zero modes are absorbed into gauge fields and form massive vector fields as a consequence of the Higgs-Kibble mechanism. The mass of the vector fields is proportional to the inverse of the radius of the sphere and larger than the mass scale set by the radius because of the higher derivative term. Comment: 18 pages
  12/2009;
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  Available from: ArXiv

  Article: Dynamical Compactification and Inflation in Einstein-Yang-Mills Theory with Higher Derivative Coupling

  Hironobu Kihara, Muneto Nitta, Misao Sasaki, Chul-Moon Yoo, Ignacio Zaballa
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  ABSTRACT: We study cosmology of the Einstein-Yang-Mills theory in ten dimensions with a quartic term in the Yang-Mills field strength. We obtain analytically a class of cosmological solutions in which the extra dimensions are static and the scale factor of the four-dimensional Friedmann-Lemaitre-Robertson-Walker metric is an exponential function of time. This means that the model can explain inflation. Then we look for solutions that describe dynamical compactification of the extra dimensions. The effective cosmological constant $\lambda_1$ in the four-dimensional universe is determined from the gravitational coupling, ten-dimensional cosmological constant, gauge coupling and higher derivative coupling. By numerical integration, the solution with $\lambda_1=0$ is found to behave as a matter-dominated universe which asymptotically approaches flat space-time, while the solution with a non-vanishing $\lambda_1$ approaches de Sitter space-time in the asymptotic future. Comment: 30 pages, 7 figures
  06/2009;
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  Available from: ArXiv

  Article: Generalized Instantons on Complex Projective Spaces

  Hironobu Kihara, Muneto Nitta
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  ABSTRACT: We study a class of generalized self-duality relations in gauge theories on the complex projective space with the Fubini-Study metric. Our theories consist of only gauge fields with gauge group U(n). The pseudo-energies which we consider contain higher orders of field strength and are labeled by an integer p smaller than or equal to [n/2]. For making the Bogomol'nyi completion we need non-single trace terms in the pseudo-energies, unlike the models defined on spheres, which were studied previously. We construct an explicit solution of codimension 2n to generalized self-duality equations as Bogomol'nyi equations, by using a part of the spin connection.
  08/2008;
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  Available from: ArXiv

  Article: Exact Solutions of Einstein-Yang-Mills Theory with Higher-Derivative Coupling

  Hironobu Kihara, Muneto Nitta
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  ABSTRACT: We construct a classical solution of an Einstein-Yang-Mills system with a fourth order term with respect to the field strength of the Yang-Mills field. The solution provides a spontaneous compactification proposed by Cremmer and Scherk; ten-dimensional space-time with a cosmological constant is compactified to the four-dimensional Minkowski space with a six-dimensional sphere S^6 on which an instanton solution exists. The radius of the sphere is not a modulus but is determined by the gauge coupling and the four-derivative coupling constants and the Newton's constant. We also construct a solution of ten-dimensional theory without a cosmological constant compactified to AdS_4 x S^6.
  05/2007;
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  Available from: ArXiv

  Article: A Classical Solution in Six-dimensional Gauge Theory with Higher Derivative Coupling

  Hironobu Kihara, Muneto Nitta
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  ABSTRACT: We show that the spin connection of the standard metric on a six-dimensional sphere gives an exact solution to the generalized self-dual equations suggested by Tchrakian some years ago. We work on an SO(6) gauge theory with a higher-derivative coupling term. The model consists of vector fields only. The pseudo-energy is bound from below by a topological charge which is proportional to the winding number of spatial S^5 around the internal space SO(6). The fifth homotopy group of SO(6) is, indeed, Z. The coupling constant of higher derivative term is quadratic in the radius of the underlying space S^6.
  03/2007;
• Source

  Available from: arxiv.org

  Article: Generalized Monopoles in Six-dimensional Non-Abelian Gauge Theory

  Hironobu Kihara, Yutaka Hosotani, Muneto Nitta
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  ABSTRACT: A spherically symmetric monopole solution is found in SO(5) gauge theory with Higgs scalar fields in the vector representation in six-dimensional Minkowski spacetime. The action of the Yang-Mills fields is quartic in field strengths. The solution saturates the Bogomolny bound and is stable.
  08/2004;