論文 - 青木　健一郎

Non-Equilibrium Steady States and Transport in $phi ^4$ Theory

青木 健一郎

Physics Letters  （ B477 ） 348-354 2000年

研究論文（学術雑誌）, 共著, 査読有り

Physics of the gauged four fermi model in $(1+1)$ dimensions

青木 健一郎

Physical Review  （ D60 ） 096004--1---13 1999年

研究論文（学術雑誌）, 共著, 査読有り

Non-decoupling effects due to a dimensionful coupling

Aoki K.

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics （Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics）  418 （ 1-2 ） 125 - 133 1998年01月

ISSN  03702693

　概要を見る

We show that the dimensionful scalar cubic coupling in 3 + 1 dimensions gives rise to non-decoupling effects and analyze the behavior of these effects. In the process, we clarify how it is perturbatively consistent to construct theories in which the cubic coupling is dominant. We use the scalar sector of the Supersymmetric Standard Model as an example. We discuss how the non-decoupling effects may be analyzed systematically. © 1998 Elsevier Science B.V.

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Non-critical strings at high energy

Aoki K., D'Hoker E.

Nuclear Physics B （Nuclear Physics B）  490 （ 1-2 ） 40 - 74 1997年04月

ISSN  05503213

　概要を見る

We consider scattering amplitudes in non-critical string theory of N external states in the limit where the energy of all external states is large compared to the string tension. We argue that the amplitudes are naturally complex analytic in the matter central charge c and we propose to define the amplitudes for arbitrary value of c by analytic continuation. We show that the high energy limit is dominated by a saddle point that can be mapped onto an equilibrium electrostatic energy configuration of an assembly of N pointlike (Minkowskian) charges, together with a density of charges arising from the Liouville field. We argue that the Liouville charges accumulate on segments of curves, and produce quadratic branch cuts on the world-sheet. The electrostatics problem is solved for string tree level in terms of hyper-elliptic integrals and is given explicitly for three-and four-point functions. We show that the high energy limit should behave in a string-like fashion with exponential dependence on the energy scale for generic values of c. © 1997 Elsevier Science B.V.

High energy scattering of non-critical strings

Aoki K., D'Hoker E.

International Journal of Modern Physics A （International Journal of Modern Physics A）  12 （ 6 ） 1253 - 1263 1997年03月

ISSN  0217751X

　概要を見る

We summarize recent work, in which we consider scattering amplitudes of non-critical strings in the limit where the energy of all external states is large compared to the string tension. We show that the high energy limit is dominated by a saddle point that can be mapped onto an electrostatic equilibrium configuration of an assembly of charges associated with the external states, together with a density of charges arising from the Liouville field. The Liouville charges accumulate on line segments, which produce quadratic branch cuts on the worldsheet. The electrostatics problem is solved for string tree level in terms of hyperelliptic integrals and is given explicitly for the 3- and 4-point functions. For generic values of the central charge, the high energy limit behaves in a string-like fashion, with exponential energy dependence. © World Scientific Publishing Company.

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(1+1)-dimensional QCD with fundamental bosons and fermions

Aoki K., Ichihara T.

Physical Review D （Physical Review D）  52 （ 11 ） 6435 - 6444 1995年

ISSN  05562821

　概要を見る

We analyze the properties of mesons in (1+1)-dimensional QCD with bosonic and fermionic ''quarks'' in the large Nc limit. We study the spectrum in detail and show that it is impossible to obtain massless mesons including boson constituents in this model. We quantitatively show how the QCD mass inequality is realized in two-dimensional QCD. We find that the mass inequality is close to being an equality even when the quarks are light. Methods for obtaining the properties of ''mesons'' formed from boson and/or fermion constituents are formulated in an explicit manner convenient for further study. We also analyze how the physical properties of the mesons such as confinement and asymptotic freedom are realized. © 1995 The American Physical Society.

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Triviality, perturbation theory and Z → bb

Aoki K., Peris S.

Physics Letters B （Physics Letters B）  335 （ 3-4 ） 470 - 478 1994年09月

ISSN  03702693

　概要を見る

We compute the large-mt contributions to the Zbb vertex in the Standard Model non-perturbatively using both the 1/Nc and the 1/NF expansions. Triviality and its consequences for the perturbative result are systematically analyzed. In particular, we point out that the effect of triviality is already important at the two-loop level for a heavy Higgs (600 GeV < MH < 1 TeV) even when the top mass is below 200 GeV. © 1994.

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Non-decoupling, triviality and the ρ{variant} parameter

Aoki K., Peris S.

Zeitschrift für Physik C Particles and Fields （Zeitschrift für Physik C Particles and Fields）  61 （ 2 ） 303 - 312 1994年06月

ISSN  01709739

　概要を見る

The dependence of the ρ{variant} parameter on the mass of the Higgs scalar and the top quark is computed non-perturbatively using the 1/NF expansion in the standard model. We find an explicit expression for the ρ{variant} parameter that requires the presence of a physical cutoff. This should come as no surprise since the theory is presumably trivial. By taking this cutoff into account, we find that the ρ{variant} parameter can take values only within a limited range and has finite ambiguities that are suppressed by inverse powers of the cutoff scale, the so called "scaling-violations". We find that large deviations from the perturbative results are possible, but only when the cutoff effects are also large. © 1994 Springer-Verlag.

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Boson-fermion bound states in two-dimensional QCD

Aoki K.

Physical Review D （Physical Review D）  49 （ 1 ） 573 - 574 1994年

ISSN  05562821

　概要を見る

We derive the boson-fermion bound state equation in a two-dimensional gauge theory in the large-Nc limit. We analyze the properties of this equation and, in particular, find that the mass trajectory is linear with respect to the bound state level for the higher mass states. © 1994 The American Physical Society.

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Large-order behavior of nondecoupling effects in the standard model and triviality

Aoki K.

Physical Review D （Physical Review D）  49 （ 3 ）  1994年

ISSN  05562821

　概要を見る

We compute some nondecoupling effects in the standard model, such as the ρ parameter, to all orders in the coupling constant expansion. We analyze their large order behavior and explicitly show how they are related to the nonperturbative cutoff dependence of these nondecoupling effects due to the triviality of the theory. © 1994 The American Physical Society.

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Nonperturbative evidence for nondecoupling of heavy fermions

Aoki K., Peris S.

Physical Review Letters （Physical Review Letters）  70 （ 12 ） 1743 - 1746 1993年

ISSN  00319007

　概要を見る

We investigate, using a 1/N expansion, the behavior of a parameter in the scalar-fermion sector of the standard model that shows perturbative nondecoupling as the fermion becomes heavy. This low-energy parameter is related to the S parameter defined through W3-B mixing. We obtain the leading 1/N contribution to this parameter that, if expanded perturbatively, collapses to its constant one-loop result. Nonperturbatively, we find that as the mass of the fermion approaches the triviality scale the behavior of the parameter is nonuniversal and shows nondecoupling. © 1993 The American Physical Society.

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W-gravity and generalized Lax equations for (super) Toda theory

Aoki K., D'Hoker E.

Nuclear Physics, Section B （Nuclear Physics, Section B）  387 （ 3 ） 576 - 586 1992年12月

ISSN  05503213

　概要を見る

We generalize the Lax pair and Bäcklund transformations for Toda and N = 1 super Toda equations to the case of arbitrary world-sheet background geometry. We use the fact that the Toda equations express constant curvature conditions, which arise naturally from flatness conditions equivalent to the W-gravity equation of motion. © 1992.

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Large-NF solution of the quark-Higgs sector of the supersymmetric standard model

Aoki K.

Physical Review D （Physical Review D）  46 （ 3 ） 1123 - 1130 1992年

ISSN  05562821

　概要を見る

We solve a model of a Higgs supermultiplet coupled to a quark (or a lepton) supermultiplet in the large-NF limit including the effects of soft supersymmetry-breaking terms. We find that the model needs to be defined with a cutoff and we obtian the spectrum of the model in the region where the masses of the particles remain below the cutoff scale of the model. The model corresponds to the quark-Higgs (or lepton-Higgs) sector of the supersymmetric versions of the standard model when the quantum corrections due to only the Yukawa-Higgs couplings are considered. © 1992 The American Physical Society.

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Effects of fermion back reaction on instantons

Aoki K., Mazur P.

Nuclear Physics, Section B （Nuclear Physics, Section B）  352 （ 2 ） 507 - 527 1991年03月

ISSN  05503213

　概要を見る

We show how systematically incorporate back reaction into fermion number violating amplitudes in Yang-Mills theories. We discuss the possible recovery of unittarity at high energies for these processes. © 1991.

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Large-NF expansion for the Yukawa coupling

Aoki K.

Physical Review D （Physical Review D）  44 （ 5 ） 1547 - 1554 1991年

ISSN  05562821

　概要を見る

By enlarging the number of fermion species and sclar fields, we generalize the Yukawa-Higgs sector of the standard model. We solve this model to leading order in a 1NF expansion. We study the behavior of the fermion mass and the width when they are below the cutoff scale of the theory. Other Yukawa-Higgs models with different chiral structures are also studied. We find that the mass of the fermion is finite and is below the cutoff scale for any finite on-shell Yukawa coupling in the chiral models. © 1991 The American Physical Society.

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Unitarity of closed superstring perturbation theory

Aoki K., D'Hoker E., Phong D.

Nuclear Physics, Section B （Nuclear Physics, Section B）  342 （ 1 ） 149 - 230 1990年09月

ISSN  05503213

　概要を見る

The scattering amplitudes for the covariant formulation of closed Type II and heterotic superstrings are shown to be equivalent, order-by-order in string perturbation theory, to those of the light-cone interacting string picture. This establishes the unitarity of covariant superstring perturbation theory and the Lorentz invariance of the light-cone superstring. © 1990.

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Topological supergravity in two dimensions

Montano D., Aoki K., Sonnenschein J.

Physics Letters B （Physics Letters B）  247 （ 1 ） 64 - 70 1990年09月

ISSN  03702693

　概要を見る

The topological theory of OSp(2|1;R) flat gauge connections is shown to be equivalent to two-dimensional supergravity. By choosing a particular gauge fixing of the SL(2;R) (OSp(2|1;R) invariance we make contact with the Liouville theory approach to two-dimensional gravity (supergravity). We discuss the scaling and multriritical behavior of two-dimensional supergravity. © 1990.

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Correlation of Z<inf>N</inf> super twist fields on the sphere

Aoki K.

Nuclear Physics, Section B （Nuclear Physics, Section B）  326 （ 2 ） 393 - 410 1989年11月

ISSN  05503213

　概要を見る

The correlation function of the ZN super twist fields is calculated on the sphere. Also, the degeneration behavior of the higher genus partition function is used to derive the spectrum of dimensions for the non-abelian super twist fields. © 1989.

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Twisted non-Abelian determinants on Riemann supersurfaces

Aoki K., Periwal V.

Communications in Mathematical Physics （Communications in Mathematical Physics）  124 （ 2 ） 301 - 306 1989年06月

ISSN  00103616

　概要を見る

We calculate the twisted supersymmetric determinants that are necessary for the study of the propagation of spinning strings on arbitrary orbifolds. We calculate the degeneration behaviour of multiloop amplitudes for twisted internal sectors. We use this to derive the spectrum of dimensions of twist fields. © 1989 Springer-Verlag.

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Heat kernels and super determinants of Laplace operators on super Riemann surfaces

Aoki K.

Communications in Mathematical Physics （Communications in Mathematical Physics）  117 （ 3 ） 405 - 429 1988年09月

ISSN  00103616

　概要を見る

Heat kernels of Laplacians on superfields of arbitrary tensor weight on super Riemann surfaces are constructed, and are used to compute the super determinants of these operators in terms of the Selberg super zeta function. © 1988 Springer-Verlag.

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