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Keiichi Akama

Publications and source records attributed to Keiichi Akama.

30 records · Page 2Linked to original sources
arXiv2000

Induced Field Theory on the Brane World - Gravity, Extrinsic Curvature, and Gauge Fields

We show how the gravity, extrinsic curvature, and gauge field theories are induced on dynamically localized brane world. They should obey the Gauss-Codazzi-Ricci equation in addition to their own equations of motion. As an example, we derive the solitonic solution for curved domain wall in five dimensions in terms of gravity and extrinsic curvature fields of the brane, and then derive the effective action for their field theory on the brane.

hep-th↗
arXiv2000

Induced Field Theory on the Brane World

We show how the gravity, gauge, and matter fields are induced on dynamically localized brane world (domain wall, vortex etc.). Solitonic solutions localized on a curved brane in certain field theories in higher dimensions are given in terms of gravity, gauge and extrinsic curvature fields of the brane. Then we deduce the effective field theory on the brane in terms of those fields and the quantum fluctuations of the solitonic solution. The gravity, gauge and the extrinsic curvature fields should obey the Gauss-Codazzi-Ricci equation in addition to their own equations of motion.

hep-th↗
arXiv2000

An Early Proposal of "Brane World"

Here we place the TeX-typeset version of the old preprint SMC-PHYS-66 (1982), which was published in K. Akama, "Pregeometry", in Lecture Notes in Physics, 176, Gauge Theory and Gravitation, Proceedings, Nara, 1982, edited by K. Kikkawa, N. Nakanishi and H. Nariai, (Springer-Verlag) 267--271. In the paper, we presented the picture that we live in a "brane world" (in the present-day terminology) i.e. in a dynamically localized 3-brane in a higher dimensional space. We adopt, as an example, the dynamics of the Nielsen-Olesen vortex type in six dimensional spacetime to localize our space-time within a 3-brane. At low energies, everything is trapped in the 3-brane, and the Einstein gravity is induced through the fluctuations of the 3-brane. The idea is important because it provides a way basically distinct from the "compactification" to hide the extra dimensions which become necessary for various theoretical reasons.

hep-th↗
arXiv1997

Complementarity between Gauge-Boson Compositeness and Asymptotic Freedom

We derive and solve the compositeness condition for the SU(N_c) gauge boson at the next-to-leading order in 1/N_f (N_f is the number of flavors) and the leading order in ln(Λ^2) (Λis the compositeness scale) to obtain an expression for the gauge coupling constant in terms of the compositeness scale. It turns out that the argument of gauge-boson compositeness (with a large Λ) is successful only when N_f/N_c>11/2, in which the asymptotic freedom fails.

hep-ph↗
arXiv1997

Nambu-Jona-Lasinio Model at the Next-to-Leading Order in 1/N

We derived and solved the compositeness condition in the Nambu-Jona-Lasinio model at the next-to-leading order in 1/N, and obtained the expressions for the effective coupling constants in terms of the compositeness scale. In the NJL model with a scalar composite, the next to leading contributions are too large for N=3. In the induced gauge theory with abelian gauge symmetry, the correction term is reasonably suppressed, while, in the SU(N_c) gauge theory with N_f flavors of fermions, the correction is suppressed only for N_f>11N_c/2, complementarily to asymptotic freedom.

nucl-th↗
arXiv1997

Compositeness Condition

By solving the compositeness condition, under which the Yukawa-type model coincides the NJL type model, we obtain the expressions for the effective coupling constants in terms of the compositeness scale at the next-to-leading order in 1/N. In the NJL model with a scalar composite, the next to leading contributions are too large for N_c=3. In the induced gauge theory with abelian gauge symmetry, the correction term is reasonably suppressed, while in the non-abelian gauge theory the corrections are suppressed only when it is asymptotically non-free.

hep-ph↗
arXiv1997

Has the Substructure of Quarks and Leptons Been Found also by the H1 and ZEUS Detectors at HERA?

The significant excess of events recently found by the H1 and ZEUS Collaborations at HERA in the deep-inelastic e^+ p scattering for high momentum-transfers squared Q^2>15000 GeV^2 over the expectation of the standard model can be explained by either one of the following possible consequences of the substructure of quarks and leptons: 1) production of leptoquarks (Phi), 2) exchange of an excited Z boson (Z'), 3) intrinsic form factors of quarks (or leptons), 4) intrinsic anomalous magnetic moments of quarks, 5) production of excited quarks (q^*), and 6) that of excited positrons (e^*+). The masses of these new particles are estimated to be m(Phi) = 280-440 GeV, m(Z') = 210-250 GeV, m(q^*) = 120-140 GeV, and m(e^*+) = 300-370 GeV, although the possibilities 2) and 5) are excluded by the currently available experimental constraints.

hep-ph↗
arXiv1997

Compositeness Condition in the Nambu-Jona-Lasinio Model

The Nambu-Jona-Lasinio model is the special case of the renormalized Yukawa model with the compositeness condition. We use it to calculate the effective coupling constants in terms of the compositeness sale (momentum cut off) at the next-to-leading order in 1/N. The next-to-leading correction is too large in the model of scalar composite, while that in the induced gauge theory is reasonably suppressed due to the gauge cancellation of the leading divergences.

hep-ph↗
arXiv1996

Has the Substructure of Quarks Been Found by the Collider Detector at Fermilab?

The significant excess recently found by the CDF Collaboration in the inclusive jet cross section for jet transverse energies $E_T \ge 200$ GeV over current QCD predictions can be explained either by possible production of excited bosons (excited gluons, weak bosons, Higgs scalars, etc.) or by that of excited quarks. The masses of the excited boson and the excited quark are estimated to be around 1600 GeV and 500 GeV, respectively.

hep-ph↗
arXiv1996

Compositeness Condition for Dynamically Induced Gauge Theories

We show that the compositeness condition for the induced gauge boson in the four-fermion interaction theory actually works beyond the one-loop approximation. The next-to-leading contributions are calculated, and turn out to be reasonably suppressed, so that the leading-order approximation is justified.

hep-ph↗
arXiv1995

Compositeness Condition at the Next-to-Leading Order in the Nambu-Jona-Lasinio Model

We investigate the compositeness condition in four dimensions at the non-trivial order (next-to-leading order in $1/N$ with the number $N$ of the colors), taking the Nambu-Jona-Lasinio model as an example. In spite of its non-renormalizability, the compositeness condition can be successfully derived and solved in compact forms. The resultant problems are discussed.

hep-ph↗