arXiv subjects

Hiroyuki Hata

Publications and source records attributed to Hiroyuki Hata.

At least 19 recordsLinked to original sources

arXiv2022

Generating string field theory solutions with matter operators from $KBc$ algebra

The $KBc$ algebra is a subalgebra that has been used to construct classical solutions in Witten's open string field theory, such as the tachyon vacuum solution. The main purpose of this paper is to give various operator sets that satisfy the $KBc$ algebra. In addition, since those sets can contain matter operators arbitrarily, we can reproduce the KOS and the Erler-Maccaferri solutions. Starting with a single D-brane solution on the tachyon vacuum, we replace the original $KBc$ in it with an appropriate set to generate each of the above solutions. Thus, it is expected that the $KBc$ algebra, combined with the single D-brane solution, leads to a more unified description of classical solutions.

hep-th↗

arXiv2021

Interior Product, Lie Derivative and Wilson Line in the $KBc$ Subsector of Open String Field Theory

The open string field theory of Witten (SFT) has a close formal similarity with Chern-Simons theory in three dimensions. This similarity is due to the fact that the former theory has concepts corresponding to forms, exterior derivative, wedge product and integration over the manifold. In this paper, we introduce the interior product and the Lie derivative in the $KBc$ subsector of SFT. The interior product in SFT is specified by a two-component "tangent vector" and lowers the ghost number by one (like the ordinary interior product maps a $p$-form to $(p-1)$-form). The Lie derivative in SFT is defined as the anti-commutator of the interior product and the BRST operator. The important property of these two operations is that they respect the $KBc$ algebra. Deforming the original $(K,B,c)$ by using the Lie derivative, we can consider an infinite copies of the $KBc$ algebra, which we call the $KBc$ manifold. As an application, we construct the Wilson line on the manifold, which could play a role in reproducing degenerate fluctuation modes around a multi-brane solution.

hep-th↗

arXiv2019

Bernoulli Numbers and Multi-brane Solutions in Cubic String Field Theory

In a previous paper [arXiv:1901.01681], we presented an analytic construction of multi-brane solutions in cubic open string field theory (CSFT) for any integer brane number. Our $(N+1)$-brane solution is given in the pure-gauge form $Ψ=U Q_\textrm{B}U^{-1}$ in terms of a unitary string field $U$ which is specified by $[N/2]$ independent real parameters $α_k$. We saw that, for various sample values of $N$ $(=2, 3, 4, 5,\cdots)$, $α_k$ can be consistently determined by two requirements: The energy density from the action should reproduce that of $(N+1)$-branes, and the EOM of the solution against the solution itself should hold. In this paper, we complete our construction by determining $α_k$ satisfying the two requirements for a generic $N$. We find that each $α_k$ is given in a closed form by using the Bernoulli numbers. We also present some supplementary results on our solution; the energy density of the solutions determined from its gravitational coupling, and the unitary string field $U$ as an exponential function.

hep-th↗

arXiv2019

Analytic Construction of Multi-brane Solutions in Cubic String Field Theory for Any Brane Number

We present an analytic construction of multi-brane solutions with any integer brane number in cubic open string field theory (CSFT) on the basis of the $KBc$ algebra. Our solution is given in the pure-gauge form $Ψ=UQ_\textrm{B}U^{-1}$ by a unitary string field $U$, which we choose to satisfy two requirements. First, the energy density of the solution should reproduce that of the $(N+1)$-branes. Second, the EOM of the solution should hold against the solution itself. In spite of the pure-gauge form of $Ψ$, these two conditions are non-trivial ones due to the singularity at $K=0$. For the $(N+1)$-brane solution, our $U$ is specified by $[N/2]$ independent real parameters $α_k$. For the 2-brane ($N=1$), the solution is unique and reproduces the known one. We find that $α_k$ satisfying the two conditions indeed exist as far as we have tested for various integer values of $N$ $(=2, 3, 4, 5, \cdots)$. Our multi-brane solutions consisting only of the elements of the $KBc$ algebra have the problem that the EOM is not satisfied against the Fock states and therefore are not complete ones. However, our construction should be an important step toward understanding the topological nature of CSFT which has similarities to the Chern-Simons theory in three dimensions.

hep-th↗

arXiv2016

BV Analysis of Tachyon Fluctuation around Multi-brane Solutions in Cubic String Field Theory

We study whether the tachyon mode exists as a physical fluctuation on the 2-brane solution and on the tachyon vacuum solution in cubic open string field theory. Our analysis is based on the Batalin-Vilkovisky formalism. We first construct a set of six string states which corresponds to the set of fields and anti-fields containing the tachyon field. Whether the tachyon field can exist as a physical fluctuation is determined by the 6x6 matrix defining the anti-bracket in the present sector. If the matrix is degenerate/non-degenerate, the tachyon field is physical/unphysical. Calculations for the pure-gauge type solutions in the framework of the KBc algebra and using the Ke-regularization lead to the expected results. Namely, the matrix for the anti-bracket is degenerate/non-degenerate in the case of the 2-brane/tachyon-vacuum solution. Our analysis is not complete, in particular, in that we have not identified the four-fold degeneracy of tachyon fluctuation on the 2-brane solution, and moreover that the present six states do not satisfy the hermiticity condition.

hep-th↗

arXiv2013

Inversion Symmetry of Gravitational Coupling in Cubic String Field Theory

It was found that the canonical energy of multi-brane solutions in CSFT constructed by the KBc algebra has a symmetry under the exchange of K=0 and K=\infty (inversion symmetry). On the other hand, the gauge invariant observable (GIO), which is regarded as the energy defined by the gravitational coupling of open string, cannot count the energy from K=\infty and therefore is not equal to the canonical energy. To resolve this discrepancy, we examine the recent argument of Baba and Ishibashi which directly relates the two energies. We find that the gravitational coupling which is equivalent to the canonical energy consists of the GIO and another new term, and the whole has the inversion symmetry.

hep-th↗

arXiv2013

Singularities in K-space and Multi-brane Solutions in Cubic String Field Theory

In a previous paper [arXiv:1111.2389], we studied the multi-brane solutions in cubic string field theory by focusing on the topological nature of the "winding number" N which counts the number of branes. We found that N can be non-trivial owing to the singularity from the zero-eigenvalue of K of the KBc algebra, and that solutions carrying integer N and satisfying the EOM in the strong sense is possible only for N=0,\pm 1. In this paper, we extend the construction of multi-brane solutions to |N|\ge 2. The solutions with N=\pm 2 is made possible by the fact that the correlator is invariant under a transformation exchanging K with 1/K and hence K=\infty eigenvalue plays the same role as K=0. We further propose a method of constructing solutions with |N|\ge 3 by expressing the eigenvalue space of K as a sum of intervals where the construction for |N|\le 2 is applicable.

hep-th↗

arXiv2011

Winding Number in String Field Theory

Motivated by the similarity between cubic string field theory (CSFT) and the Chern-Simons theory in three dimensions, we study the possibility of interpreting N=(π^2/3)\int(U Q_B U^{-1})^3 as a kind of winding number in CSFT taking quantized values. In particular, we focus on the expression of N as the integration of a BRST-exact quantity, N=\int Q_B A, which vanishes identically in naive treatments. For realizing non-trivial N, we need a regularization for divergences from the zero eigenvalue of the operator K in the KBc algebra. This regularization must at same time violate the BRST-exactness of the integrand of N. By adopting the regularization of shifting K by a positive infinitesimal, we obtain the desired value N[(U_tv)^{\pm 1}]=\mp 1 for U_tv corresponding to the tachyon vacuum. However, we find that N[(U_tv)^{\pm 2}] differs from \mp 2, the value expected from the additive law of N. This result may be understood from the fact that Ψ=U Q_B U^{-1} with U=(U_tv)^{\pm 2} does not satisfy the CSFT EOM in the strong sense and hence is not truly a pure-gauge in our regularization.

hep-th↗

arXiv2010

Relativistic Collective Coordinate Quantization of Solitons: Spinning Skyrmion

We develop a consistent relativistic generalization of collective coordinate quantization of field theory solitons. Our principle of introducing collective coordinates is that the equations of motion of the collective coordinates ensure those of the original field theory. We illustrate this principle with the quantization of spinning degrees of freedom of Skyrmion representing baryons. We calculate the leading relativistic corrections to the static properties of nucleons, and find that the corrections are non-negligible ones of 10% to 20%.

hep-th↗

arXiv2010

Relativistic Collective Coordinate System of Solitons and Spinning Skyrmion

We consider constructing the relativistic system of collective coordinates of a field theory soliton on the basis of a simple principle: The collective coordinates must be introduced into the static solution in such a way that the equation of motion of the collective coordinates ensures that of the original field theory. As an illustration, we apply this principle to the quantization of spinning motion of the Skyrmion by incorporating the leading relativistic correction to the rigid body approximation. We calculate the decay constant and various static properties of nucleons, and find that the relativistic corrections are in the range of 5% -- 20%. We also examine how the baryons deform due to the spinning motion.

hep-th↗

arXiv2008

Chiral currents and static properties of nucleons in holographic QCD

We analyze static properties of nucleons in the two flavor holographic QCD model of Sakai and Sugimoto described effectively by a five-dimensional U(2) Yang-Mills theory with the Chern-Simons term on a curved background. The baryons are represented in this model as a soliton, which at a time slice is approximately the BPST instanton with a fixed size. First, we construct a chiral current in four dimensions from the Noether current of local gauge transformations which are non-vanishing on the boundaries of the extra dimension. We examine this chiral current for nucleons with quantized collective coordinates to compute their charge distribution, charge radii, magnetic moments and axial vector coupling. Most of the results are better close to the experimental values than in the Skyrme model. We discuss the problems of our chiral current; non-uniqueness of the local gauge transformation for defining the current, and its gauge-noninvariance.

hep-th↗

arXiv2007

Baryons and the Chern-Simons term in holographic QCD with three flavors

We study dynamical baryons in the holographic QCD model of Sakai and Sugimoto in the case of three flavors and with special interest in the construction of the Chern-Simons (CS) term. The baryon classical solution in this model is given by the BPST instanton, and we carry out the collective coordinate quantization of the solution. The CS term should give rise to a first class constraint which selects baryon states with right spins. However, the original CS term written in terms of the CS 5-form does not work. We instead propose a new CS term which is gauge invariant and is given as an integral over a six dimensional space having as its boundary the original five dimensional spacetime of the holographic model. Collective coordinate quantization using our new CS term leads to correct baryon states and their mass formula.

hep-th↗

arXiv2007

Baryons from instantons in holographic QCD

We consider aspects of dynamical baryons in a holographic dual of QCD that is proposed on the basis of a D4/D8-brane configuration. We construct a soliton solution carrying a unit baryon number and show that it is given by an instanton solution of four-dimensional Yang-Mills theory with fixed size. The Chern-Simons term on the flavor D8-branes plays a crucial role of protecting the instanton from collapsing to zero size. By quantizing the collective coordinates of the soliton, we work out the baryon spectra. Negative-parity baryons as well as baryons with higher spins and isospins can be obtained in a simple manner.

hep-th↗

arXiv2005

Loop Equation in D=4, N=4 SYM and String Field Equation on AdS_5 \times S^5

We consider the loop equation in four-dimensional N=4 SYM, which is a functional differential equation for the Wilson loop W(C) and expresses the propagation and the interaction of the string C. Our W(C) consists of the scalar and the gaugino fields as well as the gauge field. The loop C is specified by six bosonic coordinates y^i(s) and two fermionic coordinates ζ(s) and η(s) besides the four-dimensional spacetime coordinates x^μ(s). We have successfully determined, to quadratic order in ζand η, the parameters in W(C) and the loop differential operator so that the equation of motion of SYM can be correctly reproduced to give the non-linear term of W(C). We extract the most singular and linear part of our loop equation and compare it with the Hamiltonian constraint of the string propagating on AdS_5 \times S^5 background.

hep-th↗

arXiv2005

Exact Results on Equations of Motion in Vacuum String Field Theory

We prove some algebraic relations on the translationally invariant solutions and the lump solutions in vacuum string field theory. We show that up to the subtlety at the midpoint the definition of the half-string projectors of the known sliver solution can be generalized to other solutions. We also find that we can embed the translationally invariant solution into the matrix equation of motion with the zero mode.

hep-th↗

arXiv2005

Boundary and Midpoint Behaviors of Lump Solutions in Vacuum String Field Theory

We discuss various issues concerning the behaviors near the boundary (σ=0,π) and the midpoint (σ=π/2) of the open string coordinate X(σ) and its conjugate momentum P(σ)=-iδ/δX(σ) acting on the matter projectors of vacuum string field theory. Our original interest is in the dynamical change of the boundary conditions of the open string coordinate from the Neumann one in the translationally invariant backgrounds to the Dirichlet one in the D-brane backgrounds. We find that the Dirichlet boundary condition is realized on a lump solution only partially and only when its parameter takes a special value. On the other hand, the string midpoint has a mysterious property: it obeys the Neumann (Dirichlet) condition in the translationally invariant (lump) background.

hep-th↗

arXiv2004

Rolling Tachyon Solution in Vacuum String Field Theory

We construct a time-dependent solution in vacuum string field theory and investigate whether the solution can be regarded as a rolling tachyon solution. First, compactifying one space direction on a circle of radius R, we construct a space-dependent solution given as an infinite number of *-products of a string field with center-of-mass momentum dependence of the form e^{-b p^2/4}. Our time-dependent solution is obtained by an inverse Wick rotation of the compactified space direction. We focus on one particular component field of the solution, which takes the form of the partition function of a Coulomb system on a circle with temperature R^2. Analyzing this component field both analytically and numerically using Monte Carlo simulation, we find that the parameter b in the solution must be set equal to zero for the solution to approach a finite value in the large time limit x^0\to\infty. We also explore the possibility that the self-dual radius R=\sqrt{α'} is a phase transition point of our Coulomb system.

hep-th↗

arXiv2003

Time Dependent Solution in Cubic String Field Theory

We study time dependent solutions in cubic open string field theory which are expected to describe the configuration of the rolling tachyon. We consider the truncated system consisting of component fields of level zero and two, which are expanded in terms of cosh n x^0 modes. For studying the large time behavior of the solution we need to know the coefficients of all and, in particular, large n modes. We examine numerically the coefficients of the n-th mode, and find that it has the leading n-dependence of the form (-β)^n λ^{-n^2} multiplied by a peculiar subleading part with peaks at n=2^m=4,8,16,32,64,128,.... This behavior is also reproduced analytically by solving simplified equations of motion of the tachyon system.

hep-th↗