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H. Itoyama

Publications and source records attributed to H. Itoyama.

At least 55 records · Page 3Linked to original sources
arXiv2003

Gluino-Condensate (CIV-DV) Prepotential from its Whitham-Time Derivatives

We describe an expedient way to derive the CIV-DV prepotential in power series expansion in S_i. This is based on integrations of equations for its derivatives with respect to additional (Whitham) moduli T_m. For illustrative purposes, we calculate explicitly the leading terms of the expansion and explicitly check some components of the WDVV equations to the leading order. Extension to any higher order is simple and algorithmic.

hep-th↗
arXiv2002

Calculating Gluino-Condensate Prepotential

We discuss the derivation of the CIV-DV prepotential for arbitrary power n+1 of the original superpotential in the N=1 SUSY YM theory (for arbitrary number n of cuts in the solution of the planar matrix model in the Dijkgraaf-Vafa interpretation). The goal is to hunt for structures, not so much for exact formulas, which are necessarily complicated, before the right language is found to represent them. Some entities, reminiscent of representation theory, clearly emerge, but a lot of work remains to be done to identify the relevant ones. As a practical application, we obtain a cubic (first non-perturbative) contribution to the prepotential for any n.

hep-th↗
arXiv2002

The Dijkgraaf-Vafa prepotential in the context of general Seiberg-Witten theory

We consider the prepotential of Dijkgraaf and Vafa (DV) as one more (and in fact, singular) example of the Seiberg-Witten (SW) prepotentials and discuss its properties from this perspective. Most attention is devoted to the issue of complete system of moduli, which should include not only the sizes of the cuts (in matrix model interpretation), but also their positions, i.e. the number of moduli should be almost doubled, as compared to the DV consideration. We introduce the notion of regularized DV system (not necessarilly related to matrix model) and discuss the WDVV equations. These definitely hold before regularization is lifted, but an adequate limiting procedure, preserving all ingredients of the SW theory, remains to be found.

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arXiv2002

Experiments with the WDVV equations for the gluino-condensate prepotential: the cubic (two-cut) case

We demonstrate by explicit calculation that the first two terms in the CIV-DV prepotential for the two-cut case satisfy the generalized WDVV equations, just as in all other known examples of hyperelliptic Seiberg-Witten models. The WDVV equations are non-trivial in this situation, provided the set of moduli is extended as compared to the Dijkgraaf-Vafa suggestion and includes also moduli, associated with the positions of the cuts (not only with their lengths). Expression for the extra modulus dictated by WDVV equation, however, appears different from a naive expectation implied by the Whitham theory. Moreover, for every value of the "quantum-deformation parameter" 1/g_3, we actually find an entire one-parameter family of solutions to the WDVV equations, of which the conventional prepotential is just a single point.

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arXiv2002

Normalization of Off-shell Boundary State, g-function and Zeta Function Regularization

We consider the model in two dimensions with boundary quadratic deformation (BQD), which has been discussed in tachyon condensation. The partition function of this model (BQD) on a cylinder is determined, using the method of zeta function regularization. We show that, for closed channel partition function, a subtraction procedure must be introduced in order to reproduce the correct results at conformal points. The boundary entropy (g-function) is determined from the partition function and the off-shell boundary state. We propose and consider a supersymmetric generalization of BQD model, which includes a boundary fermion mass term, and check the validity of the subtraction procedure.

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arXiv2002

Progress in QCD next-to-leading order calculations

I review progress related to the calculation of QCD jet cross sections at the NLO accuracy. After a short introduction into the theory of NLO calculations, I discuss two recent developments: the calculation of two- and three-jet leptoproduction at the NLO accuracy and the extension of the dipole subtraction method for computing NLO corrections for processes involving massive partons.

hep-ph↗
arXiv2000

Behavior of Boundary String Field Theory Associated with Integrable Massless Flow

We put forward an idea that the boundary entropy associated with integrable massless flow of thermodynamic Bethe ansatz (TBA) is identified with tachyon action of boundary string field theory. We show that the temperature parameterizing a massless flow in the TBA formalism can be identified with tachyon energy for the classical action at least near the ultraviolet fixed point, i.e. the open string vacuum.

hep-th↗
arXiv2000

Note on Open String/D-brane System and Noncommutative Soliton

This is a summary of a series of papers hep-th/9910263,0005283,0010066 written with B. Chen, T. Matsuo and K. Murakami on a p-p', (p<p^{\prime}) open string with B_{ij} field, which has led us to the explicit identification of the Dp-brane with the noncommutative projector soliton via the gaussian damping factor. A lecture given at Summer Institute 2000, FujiYoshida, Yamanashi, Japan, at August 7-14, 2000.

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arXiv2000

Correspondence between Noncommutative Soliton and Open String/D-brane System via Gaussian Damping Factor

The gaussian damping factor (g.d.f.) and the new interaction vertex with the symplectic tensor are the characteristic properties of the N-point scalar-vector scattering amplitudes of the p-p' (p < p') open string system which realizes noncommutative geometry. The g.d.f. is here interpreted as a form factor of the Dp-brane by noncommutative U(1) current. Observing that the g.d.f. is in fact equal to the Fourier transform of the noncommutative projector soliton introduced by Gopakumar, Minwalla and Strominger, we further identify the Dp-brane in the zero slope limit with the noncommutative soliton state. It is shown that the g.d.f. depends only on the total momentum of N-2 incoming/outgoing photons in the zero slope limit. In the description of the low-energy effective action (LEEA) proposed before, this is shown to follow from the delta function propagator and the form of the initial/final wave functions in the soliton sector which resides in x^{m} m= p+1, ...p' dependent part of the scalar field Φ(x^μ, x^m). The three and four point amplitudes computed from LEEA agree with string calculation. We discuss related issues which are resummation/lifting of infinite degeneracy and conservation of momentum transverse to the Dp-brane.

hep-th↗
arXiv2000

Worldsheet and Spacetime Properties of p-p' System with B Field and Noncommutative Geometry

We study worldsheet and spacetime properties of the p-p' (p < p') open string system with constant B_{ij} field viewed from the Dp' brane. The description of this system in terms of the CFT with spin and twist fields leads us to consider the renormal ordering procedure from the SL(2,R) invariant vacuum to the oscillator vacuum. We compute the attendant two distinct superspace two-point functions as well as their difference (the subtracted two-point function). These bring us an integral (Koba-Nielsen) representation for the multiparticle tree scattering amplitudes consisting of N-2 vectors and two tachyons. We evaluate them explicitly for the N=3,4 cases. Several novel features are observed which include a momentum dependent multiplicative factor to each external vector leg and the emergence of a symplectic tensor multiplying the polarization vectors. In the zero slope limit, the principal parts of the amplitudes translate into a noncommutative field theory in p'+1 dimensions in which a scalar field decaying exponentially in (p'-p) dimensions and a noncommutative U(1) gauge field interact via the minimal coupling and a new interaction. A large number of nearly massless states noted before are shown to propagate in the t-channel.

hep-th↗
arXiv2000

Anomalous Interactions of Five Dimensional USp(2k) Gauge Theory

We consider the five dimensional $USp(2k)$ gauge theory which consists of one antisymmetric and $n_{f}$ fundamental hypermultiplets. This gauge theory is a many-probe generalization of the SU(2) gauge theory in five dimensions considered by Seiberg in the context of probing type I superstring by a D4-brane. This gauge theory can also be obtained from the USp(2k) matrix model by matrix T-dual transformations in the large k limit. We exhibit the anomalous interaction associated with this five dimensional theory on the new phase, where the vacuum expectation values (vevs) of the scalars belonging to the antisymmetric hypermultiplet are also nonvanishing. On the Coulomb phase, the anomalous interaction has been computed in [1, 2].

hep-th↗
arXiv1999

p-p' System with B-field, Branes at Angles and Noncommutative Geometry

We study the generic $p-p^\prime$ system in the presence of constant NS 2-form $B_{ij}$ field. We derive properties concerning with the noncommutativity of D-brane worldvolume, the Green functions and the spectrum of this system. In the zero slope limit, a large number of light states appear as the lowest excitations in appropriate cases. We are able to relate the energies of the lowest states after the GSO projection with the configurations of branes at angles. Through analytic continuation, the system is compared with the branes with relative motion.

hep-th↗
arXiv1999

Nonabelian Monopoles from Matrices: Seeds of the Spacetime Structure

We study the expectation value of (the product) of the one-particle projector (s) in the reduced matrix model and matrix quantum mechanics in general. This quantity is given by the nonabelian Berry phase: we discuss the relevance of this with regard to the spacetime structure. The case of the USp matrix model is examined from this respect. Generalizing our previous work, we carry out the complete computation of this quantity which takes into account both the nature of the degeneracy of the fermions and the presence of the space time points belonging to the antisymmetric representation. We find the singularities as those of the SU(2) Yang monopole connection as well as the pointlike singularities in 9+1 dimensions coming from its SU(8) generalization. The former type of singularities, which extend to four of the directions lying in the antisymmetric representations, may be regarded as seeds of our four dimensional spacetime structure and is not shared by the IIB matrix model. From a mathematical viewpoint, these connections can be generalizable to arbitrary odd space dimensions due to the nontrivial nature of the eigenbundle and the Clifford module structure.

hep-th↗
arXiv1999

Nonabelian Berry Phase, Yang-Mills Instanton and USp(2k) Matrix Model

The nonabelian Berry phase is computed in the T dualized quantum mechanics obtained from the USp(2k) matrix model. Integrating the fermions, we find that each of the spacetime points X_ν^{(i)} is equipped with a pair of su(2) Lie algebra valued pointlike singularities located at a distance m_{(f)} from the orientifold surface. On a four dimensional paraboloid embedded in the five dimensional Euclidean space, these singularities are recognized as the BPST instantons.

hep-th↗
arXiv1999

USp(2k) Matrix Model

We review the construction and theoretical implications of the USp(2k) matrix model in zero dimension introduced in ref. \cite{IT1,IT2}. It is argued that the model provides a constructive approach to Type I superstrings and is at the same time dynamical theory of spacetime points. Three subjects are discussed : semiclassical pictures and series of degenerate perturbative vacua associated with the worldvolume representation of the model, the formation of extended (D-)objects from the fermionic integrations via the (non-)abelian Berry phase, and the Schwinger-Dyson/loop equations which exhibit the joining-splitting interactions required. Lectures presented at the 13th Nishinomiya-Yukawa Memorial Symposium ``Dynamics of Fields and Strings'' (November 12-13,1998) and at the YITP workshop (November 16-18, 1998).

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arXiv1998

USp(2k) Matrix Model: Schwinger-Dyson Equations and Closed-Open String Interactions

We derive the Schwinger-Dyson/loop equations for the USp(2k) matrix model which close among the closed and open Wilson loop variables. These loop equations exhibit a complete set of the joining and splitting interactions required for the nonorientable Type I superstrings. The open loops realize the SO(2n_f) Chan-Paton factor and their linearized loop equations derive the mixed Dirichlet/Neumann boundary conditions.

hep-th↗
arXiv1998

Berry's Connection and USp(2k) Matrix Model

Berry's connection is computed in the USp(2k) matrix model. In T dualized quantum mechanics, the Berry phase exhibits a residual interaction taking place at a distance m_(f) from the orientifold surface via the integration of the fermions in the fundamental representation. This is interpreted as a coupling of the magnetic D2 with the electric D4 branes. We make a comment on the Berry phase associated with the 6D nonabelian gauge anomaly whose cancellation selects the number of flavours n_f=16.

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