Akifumi Sako

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• doctor of science
• Professor at Tokyo University of Science

We review the noncommutative deformation of instantons. In the operator formalism, we see the relation between topological charges and noncommutativity. Smooth noncommutative deformations of instantons, spinor zero modes, the Green’s functions and the ADHM construction are studied. We construct their deformations from commutative ones. It is found...

Deformation quantization of instantons in U(N) (N>1) gauge theory in ℝ 4 has been established in recent few years. However for U(1) case, noncommutative instantons are not constructed as deformation solutions. We summarize the results of deformation quantization of instantons and related topics. Then, we discuss on the construction of the noncommut...

We construct a gauge theory on a noncommutative homogeneous K\"ahler manifold, where we employ the deformation quantization with separation of variables for K\"ahler manifolds formulated by Karabegov. A key point in this construction is to obtaining vector fields which act as inner derivations for the deformation quantization. We show that these ve...

We study noncommutative deformation of manifolds by constructing star products. We start from a noncommutative Bbb Rd and discuss more genaral noncommutative manifolds. In general, star products can not be described in concrete expressions without some exceptions. In this article we introduce new examples of noncommutative manifolds with explicit s...

We give explicit expressions of a deformation quantization with separation of variables for \documentclass[12pt]{minimal}\begin{document}${\mathbb C}P^N$\end{document}CPN and \documentclass[12pt]{minimal}\begin{document}${\mathbb C}H^N$\end{document}CHN. This quantization method is one of the ways to perform a deformation quantization of Kähler man...

A quantization of Lie-Poisson algebras is studied. The mass-deformed IIB matrix model admits classical solutions constructed from the basis of any semisimple Lie algebra. We consider the geometry described by the classical solutions of the Lie algebras in the limit where the mass vanishes and the matrix size is infinite. Lie-Poisson varieties are r...

We study some Hermitian Φ ⁴ -matrix model and some real symmetric Φ ⁴ -matrix model whose kinetic terms are given by Tr( E Φ ² ), where E is a positive diagonal matrix without degenerate eigenvalues. We show that the partition functions of these matrix models correspond to zero-energy solutions of a Schödinger type equation with N -body harmonic os...

We study a Hermitian matrix model with a kinetic term given by Tr(HΦ2)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ Tr (H \Phi ^2 )$$\end{document}, where H is a pos...

We study a real symmetric Φ4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Phi ^4$$\end{document}-matrix model whose kinetic term is given by Tr(EΦ2)\documentclass[12...

We study a real symmetric $\Phi^{4}$-matrix model whose kinetic term is given by $\mathrm{Tr}( E \Phi^2)$, where $E$ is a positive diagonal matrix without degenerate eigenvalues. We show that the partition function of this matrix model corresponds to a zero-energy solution of a Schödinger type equation with Calogero-Moser Hamiltonian. A family of d...

We study a Hermitian matrix model with a kinetic term given by $ Tr (H \Phi^2 )$, where $H$ is a positive definite Hermitian matrix, similar as in the Kontsevich Matrix model, but with its potential $\Phi^3$ replaced by $\Phi^4$. We show that its partition function solves an integrable Schr\"odinger-type equation for a non-interacting $N$-body Harm...

There is a matrix model corresponding to a scalar field theory on noncommutative spaces called Grosse-Wulkenhaar model (Φ4 matrix model), which is renormalizable by adding a harmonic oscillator potential to scalar Φ4 theory on Moyal spaces. There are more unknowns in Φ4 matrix model than in Φ3 matrix model, for example, in terms of integrability. W...

There is a matrix model corresponding to a scalar field theory called Grosse-Wulkenhaar model, which is renormalizable by adding a harmonic oscillator potential to scalar Φ4 theory on Moyal spaces. There are more unknowns in Φ4 matrix model than in Φ3 matrix model, for example, in terms of integrability. We then construct a one-matrix model (Φ3-Φ4...

We introduce a category composed of all quantizations of all Poisson algebras. By the category, we can treat in a unified way the various quantizations for all Poisson algebras and develop a new classical limit formulation. This formulation proposes a new method for the inverse problem, that is, the problem of finding the classical limit from a qua...

We give a complex two-dimensional noncommutative locally symmetric Kähler manifold via a deformation quantization with separation of variables. We present an explicit formula of its star product by solving the system of recurrence relations given by Hara–Sako. In the two-dimensional case, this system of recurrence relations gives two types of equat...

Lin, Lu, and Yau formulated the Ricci curvature of edges in simple undirected graphs[2]. Using their formulations, we calculate the Ricci curvatures of Cayley graphs for the dihedral groups, the general quaternion groups, and cyclic groups with some generating sets that are chosen so that their cardinal numbers are less than or equal to four. For t...

We give a complex two-dimensional noncommutative locally symmetric K\"{a}hler manifold via a deformation quantization with separation of variables. We present an explicit formula of its star product by solving the system of recurrence relations given by Hara-Sako. In the two-dimensional case, this system of recurrence relations gives two types of e...

We find the exact solutions of the Φ23 finite matrix model (Grosse-Wulkenhaar model). In the Φ23 finite matrix model, multipoint correlation functions are expressed as G|a11…aN11|…|a1B…aNBB|. The ∑i=1BNi-point function denoted by G|a11…aN11|…|a1B…aNBB| is given by the sum over all Feynman diagrams (ribbon graphs) on Riemann surfaces with B-boundari...

We find the exact solutions of the $\Phi_{2}^{3}$ finite matrix model (Grosse-Wulkenhaar model). In the $\Phi_{2}^{3}$ finite matrix model, multipoint correlation functions are expressed as $G_{|a_{1}^{1}\ldots a_{N_{1}}^{1}|\ldots|a_{1}^{B}\ldots a_{N_{B}}^{B}|}$. The $\displaystyle \sum_{i=1}^{B}N_{i}$-point function denoted by $G_{|a_{1}^{1}\ldo...

We introduce a category composed of all quantizations of all Poisson algebras. By the category, we can treat in a unified way the various quantizations for all Poisson algebras and develop a new classical limit formulation. This formulation proposes a new method for the inverse problem, that is, the problem of finding the classical limit from a qua...

We discuss the relationship between (co)homology groups and categorical diagonalization. We consider the category of chain complexes in the category of finite-dimensional vector spaces over a fixed field. For a fixed chain complex with zero maps as an object, a chain map from the object to another chain complex is defined, and the chain map introdu...

A construction methods of noncommutative locally symmetric K\"ahler manifolds via a deformation quantization with separation of variables was proposed by Sako-Suzuki-Umetsu and Hara-Sako. This construction gives the recurrence relations to determine the star product. These recurrence relations were solved for the case of the arbitrary one-dimension...

We propose a generalization of quantization using a categorical approach. For a fixed Poisson algebra, quantization categories are defined as subcategories of the R-module category equipped with the structure of classical limits. We then construct the generalized quantization categories including matrix regularization, strict deformation quantizati...

A sequence of homology groups as an object in a monoidal homotopy category is discussed. For a morphism which has a fixed object (a sequence of chain complexes) as a domain in a monoidal homotopy category, we consider a mapping cone of the morphism with a proper boundary operator. It is shown that if the mapping cone is homotopy equivalent to zero,...

We show that Hermitian-Einstein metrics can be locally constructed by a map from (anti-)self-dual two-forms on Euclidean R4 to symmetric two-tensors introduced in Yang and Salizzoni [Phys. Rev. Lett. 96 201602 (2006); e-print arXiv:hep-th/0512215]. This correspondence is valid not only for a commutative space but also for a noncommutative space. We...

We propose a generalization of quantization as a categorical way. For a fixed Poisson algebra quantization categories are defined as subcategories of R-module category with the structure of classical limits. We construct the generalized quantization categories including matrix regularization, strict deformation quantization, prequantization, and Po...

We show that Hermitian-Einstein metrics can be locally constructed by a map from (anti-)self-dual two-forms on Euclidean ${\mathbb R}^4$ to symmetric two-tensors introduced in "Gravitational instantons from gauge theory," H. S. Yang and M. Salizzoni, Phys. Rev. Lett. (2006) 201602, [hep-th/0512215]. This correspondence is valid not only for a commu...

We apply a recently developed method to exactly solve the Φ3 matrix model with covariance of a two-dimensional theory, also known as regularised Kontsevich model. Its correlation functions collectively describe graphs on a multi-punctured 2-sphere. We show how Ward–Takahashi identities and Schwinger–Dyson equations lead in a special large-N limit t...

The goal of this paper is to construct the Fock representation of noncommutative Kähler manifolds. Noncommutative Kähler manifolds studied here are constructed by deformation quantization with separation of variables, which was given by Karabegov. The algebra of the noncommutative Kähler manifolds contains the Heisenberg-like algebras. Local comple...

We extend our previous work (on D=2) to give an exact solution of the $\Phi^3_D$ large-N matrix model (or renormalised Kontsevich model) in D=4 and D=6 dimensions. Induction proofs and the difficult combinatorics are unchanged compared with D=2, but the renormalisation - performed according to Zimmermann - is much more involved. As main result we p...

We extend our previous work (on $D=2$) to give an exact solution of the $\Phi^3_D$ large-$\mathcal{N}$ matrix model (or renormalised Kontsevich model) in $D=4$ and $D=6$ dimensions. Induction proofs and the difficult combinatorics are unchanged compared with $D=2$, but the renormalisation - performed according to Zimmermann - is much more involved....

We apply a recently developed method to exactly solve the $\Phi^3$ matrix model with covariance of a two-dimensional theory, also known as regularised Kontsevich model. Its correlation functions collectively describe graphs on a multi-punctured 2-sphere. We show how Ward-Takahashi identities and Schwinger-Dyson equations lead in a special large-$\m...

We derive algebraic recurrence relations to obtain a deformation quantization with separation of variables for a locally symmetric K\"ahler manifold. This quantization method is one of the ways to perform a deformation quantization of K\"ahler manifolds, which is introduced by Karabegov. From the recurrence relations, concrete expressions of star p...

We derive algebraic recurrence relations to obtain a deformation quantization with separation of variables for a locally symmetric K\"ahler manifold. This quantization method is one of the ways to perform a deformation quantization of K\"ahler manifolds, which is introduced by Karabegov. From the recurrence relations, concrete expressions of star p...

We introduce twisted Fock representations of noncommutative K\"ahler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by acting creation operators on a vacuum state. "Twisted" means that creation operators are not hermitian conjugate of ann...

We introduce twisted Fock representations of noncommutative K\"ahler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by acting creation operators on a vacuum state. "Twisted" means that creation operators are not hermitian conjugate of ann...

We give the Fock representation of a noncommutative CPN and gauge theories on it. The Fock representation is constructed based on star products given by deformation quantization with separation of variables and operators which act on states in the Fock space are explicitly described by functions of inhomogeneous coordinates on CPN. Using the Fock r...

We study gauge theories on noncommutative homogeneous Kähler manifolds. To make the noncommutative manifolds, we use the deformation quantization with separation of variables for Kähler manifolds. We construct models of noncommutative gauge theories that are connected with usual Yang-Mills theories in the commutative limits. It is expected that the...

We give the Fock representations of a noncommutative $\mathbb{C}P^N$ and gauge theories on it. The Fock representation is constructed based on star products given by deformation quantization with separation of variables and operators which act on states in the Fock space are explicitly described by functions of inhomogeneous coordinates on ${\mathb...

We construct a gauge theory on a noncommutative homogeneous Kähler manifold by using the deformation quantization with separation of variables for Kähler manifolds. A model of noncommutative gauge theory that is connected with an ordinary Yang–Mills theory in the commutative limit is given. As an examples, we review a noncommutative \( \mathbb{C}P^...

We give explicit expressions of a deformation quantization with separation of variables for CP^N and CH^N. This quantization method is one of the ways to perform a deformation quantization of Kahler manifolds, which is introduced by Karabegov. Star products are obtained as explicit formulae in all order in the noncommutative parameter. We also give...

A method to construct noncommutative instantons as deformations from commutative instantons was provided by Maeda and Sako [J. Geom. Phys. 58, 1784 (2008)]10.1016/j.geomphys.2008.08.006. Using this noncommutative deformed instanton, we investigate the spinor zero modes of the Dirac operator in a noncommutative instanton background on noncommutative...

It is known that if gauge conditions have Gribov zero modes, then topological symmetry is broken. In this paper we apply it to the Witten type topological gravitational theory in dimension n ≥ 3. Our choice of the gauge condition for conformal invariance is R + α = 0, where R is the Ricci scalar curvature. We find when α ≠ 0, topological symmetry i...

We give explicit formulas for star products in ℂPN and ℂHN in all order of a noncommutative parameter. We use a quantization method to perform a deformation quantization of Kähler manifolds, which is introduced by Karabegov. We also investigate the Fock representations of the noncommutative ℂPN and ℂH N.

We review recent developments in noncommutative deformations of instantons in ℝ4. In the operator formalism, we study how to make noncommutative instantons by using the ADHM method, and we review the relation between topological charges and noncommutativity. In the ADHM methods, there exist instantons whose commutative limits are singular. We revie...

A method to construct noncommutative instantons as deformations from commutative instantons was provided in arXiv:0805.3373. Using this noncommutative deformed instanton, we investigate the spinor zero modes of the Dirac operator in a noncommutative instanton background on noncommutative R^4, and we modify the index of the Dirac operator on the non...

We study noncommutative (NC) instantons and vortexes. At first, we construct instanton solutions which are deformations of instanton solutions on commutative Euclidean four-space. We show that the instanton numbers of these NC instanton solutions coincide with the commutative solutions. Next, we also deform vortex solutions similarly and we show th...

We study instanton solutions on noncommutative Euclidean 4-space which are deformations of instanton solutions on commutative Euclidean 4-space. We show that the instanton numbers of these noncommutative instanton solutions coincide with the commutative solutions and conjecture that the instanton number in R4 is preserved for general noncommutative...

We study noncommutative vortex solutions that minimize the action functional of the Abelian Higgs model in 2-dimensional noncommutative Euclidean space. We first consider vortex solutions which are deformed from solutions defined on commutative Euclidean space to the noncommutative one. We construct solutions whose vortex numbers are unchanged unde...

We construct instanton solutions on noncommutative Euclidean 4-space which are deformations of instanton solutions on commutative Euclidean 4-space. We show that the instanton numbers of these noncommutative instanton solutions coincide with the commutative solutions and conjecture that the instanton number in R^4 is preserved for general noncommut...

We study noncommutative vortex solutions that minimize the action functional of the Abelian Higgs model in 2-dimensional noncommutative Euclidean space. We first consider vortex solutions which are deformed from solutions defined on commutative Euclidean space to the noncommutative one. We construct solutions whose vortex numbers are unchanged unde...

We investigate cohomological gauge theories in noncommutative R{sup 2D}. We show that vacuum expectation values of the theories do not depend on noncommutative parameters, and the large noncommutative parameter limit is equivalent to the dimensional reduction. As a result of these facts, we show that a partition function of a cohomological theory d...

We investigate the Seiberg-Witten monopole equations on noncommutative(N.C.) R^4 at the large N.C. parameter limit, in terms of the equivariant cohomology. In other words, N}=2 supersymmetric U(1) gauge theories with hypermultiplet on N.C. R}^4 are studied. It is known that after topological twisting partition functions of N}>1 supersymmetric theor...

We investigate SUSY of Wess-Zumino models in non(anti-)commutative euclidean superspaces. Non(anti-)commutative deformations break 1/2 SUSY, then non(anti-)commutative Wess-Zumino models do not have full SUSY in general. However, we can recover full SUSY at specific coupling constants satisfying some relations. We give a general way to construct fu...

There are two types of non(anti)commutative deformation of D=4, N=1 supersymmetric field theories and D=2, N=2 theories. One is based on the nonsupersymmetric star product and the other is based on the supersymmetric star product. These deformations cause partial breaking of supersymmetry in general. In case of supersymmetric star product, the chir...

We study topological aspects of matrix models and noncommutative cohomological field theories (N.C.CohFT). N.C.CohFT have symmetry under the arbitrary infinitesimal noncommutative parameter $\theta$ deformation. This fact implies that N.C.CohFT possess a less sensitive topological property than K-theory, but the classification of manifolds by N.C.C...

We show that the integral of the first Pontrjagin class is given by an integer and it is identified with instanton number of the U(n) gauge theory on noncommutative 4. Here the dimension of the vector space V that appear in the ADHM construction is called Instanton number. The calculation is done in operator formalism and the first Pontrjagin class...

In non-commutative spaces, it is unknown whether the Pontrjagin class gives integer, as well as, the relation between the instanton number and Pontrjagin class is not clear. Here we define ``Instanton number'' by the size of the matrices Bα in the ADHM construction. We show the analytical derivation of the non-commuatative U(1) instanton number as...

In noncommutative spaces, it is unknown whether the Pontrjagin class gives integer, as well as, the relation between the instanton number and Pontrjagin class is not clear. Here we define ``Instanton number'' by the size of $B_{\alpha}$ in the ADHM construction. We show the analytical derivation of the noncommuatative U(1) instanton number as an in...

We discover the method to make invariants under the shift of noncommutative parameter. This proceeding is short summary of the paper [1] (hep-th/0107033) and for the 10th Tohwa International Symposium on String theory which was held in Fukuoka, July 2001. .

81R60 Noncommutative geometry 81T13 Yang-Mills and other gauge theories (See also 53C07, 58E15) 81T75 Noncommutative geometry methods (See also 46L85, 46L87, 58B34)

We show that it is possible to construct a quantum field theory that is invariant under the translation of the noncommutative parameter $\theta_{\mu\nu}$. This is realized in a noncommutative cohomological field theory. As an example, a noncommutative cohomological scalar field theory is constructed, and its partition function is calculated. The pa...

We show that a partition function of topological twisted N=4 Yang-Mills theory is given by Seiberg-Witten invariants on a Riemannian four manifolds under the condition that the sum of Euler number and signature of the four manifolds vanish. The partition function is the sum of Euler number of instanton moduli space when it is possible to apply the...

The role of reducible connections in non-Abelian Seiberg-Witten invariants is analyzed with massless topological QCD where the monopole is extended to the non-Abelian group version. By giving small external fields, we found that the vacuum expectation value can be separated into a part from Donaldson theory, a part from Abelian monopole theory and...

A role of reducible connections in Non-Abelian Seiberg-Witten invariants is analyzed with massless Topological QCD where monopole is extended to non-Abelian groups version. By giving small external fields, we found that vacuum expectation value can be separated into a part from Donaldson theory, a part from Abelian Monopole theory and a part from n...

It is known that if gauge conditions have Gribov zero modes, then topological symmetry is broken. In this paper we apply it to the Witten type topological gravitational theory in dimension n ≥ 3. Our choice of the gauge condition for conformal invariance is R + α = 0, where R is the Ricci scalar curvature. We find when α ≠ 0, topological symmetry i...

In noncommutative spaces, it is unknown whether the Pontrjagin class gives integer, as well as, the relation between the instanton number and Pontrjagin class is not clear. Here we define "Instanton number" by the size of Bin the ADHM construction. We show the analytical derivation of the noncommuatative U(1) instanton number as an integral of Pont...

We study topological aspects of matrix models and noncommutative cohomological scalar field theories (N.C.CohFT). N.C.CohFT exhibit a symmetry under an arbitrary infinitesimal deformation of the noncommutativity parameter θ. This fact implies that N.C.CohFT possess a less sensitive topological property than K-theory, but the classification of manif...