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Takaaki Ishii

Publications and source records attributed to Takaaki Ishii.

42 records · Page 3Linked to original sources
arXiv2010

Toward Bound-State Approach to Strangeness in Holographic QCD

An approach to realize a hyperon as a bound-state of a two-flavor baryon and a kaon is considered in the context of the Sakai-Sugimoto model of holographic QCD, which approach has been known in the Skyrme model as the bound-state approach to strangeness. As a simple case of study, pseudo-scalar kaon is considered as fluctuation around a baryon. In this case, strongly-bound hyperon-states are absent, different from the case of the Skyrme model. Observed is a weak bound-state which would correspond to Λ(1405).

hep-th↗
arXiv2008

Fiber Bundles and Matrix Models

We investigate relationship between a gauge theory on a principal bundle and that on its base space. In the case where the principal bundle is itself a group manifold, we also study relations of those gauge theories with a matrix model obtained by dimensionally reducing them to zero dimensions. First, we develop the dimensional reduction of Yang-Mills (YM) on the total space to YM-higgs on the base space for a general principal bundle. Second, we show a relationship that YM on an SU(2) bundle is equivalent to the theory around a certain background of YM-higgs on its base space. This is an extension of our previous work (hep-th/0703021), in which the same relationship concerning a U(1) bundle is shown. We apply these results to the case of $SU(n+1)$ as the total space. By dimensionally reducing YM on $SU(n+1)$, we obtain YM-higgs on $SU(n+1)/SU(n)\simeq S^{2n+1}$ and on $SU(n+1)/(SU(n)\times U(1))\simeq CP^n$ and a matrix model. We show that the theory around each monopole vacuum of YM-higgs on $CP^n$ is equivalent to the theory around a certain vacuum of the matrix model in the commutative limit. By combing this with the relationship concerning a U(1) bundle, we realize YM-higgs on $SU(n+1)/SU(n)\simeq S^{2n+1}$ in the matrix model. We see that the relationship concerning a U(1) bundle can be interpreted as Buscher's T-duality.

hep-th↗
arXiv2008

N=4 Super Yang-Mills from the Plane Wave Matrix Model

We propose a nonperturbative definition of N=4 super Yang-Mills (SYM). We realize N=4 SYM on RxS^3 as the theory around a vacuum of the plane wave matrix model. Our regularization preserves sixteen supersymmetries and the gauge symmetry. We perform the 1-loop calculation to give evidences that the superconformal symmetry is restored in the continuum limit.

hep-th↗
arXiv2008

On relationships among Chern-Simons theory, BF theory and matrix model

Chern-Simons theory on a U(1) bundle over a Riemann surface Σ_g of genus g is dimensionally reduced to BF theory with a mass term, which is equivalent to the two-dimensional Yang-Mills on Σ_g. We show that the former is inversely obtained from the latter by the extended matrix T-duality developed in hep-th/0703021. For the case of g=0 (i.e. S^2), the U(1) bundle represents the lens space S^3/Z_p. We find that in this case both the Chern-Simons theory and the BF theory with the mass term are realized in a matrix model. We also construct Wilson loops in the matrix model that correspond to those in the Chern-Simons theory on S^3.

hep-th↗
arXiv2007

T-duality, Fiber Bundles and Matrices

We extend the T-duality for gauge theory to that on curved space described as a nontrivial fiber bundle. We also present a new viewpoint concerning the consistent truncation and the T-duality for gauge theory and discuss the relation between the vacua on the total space and on the base space. As examples, we consider S^3(/Z_k), S^5(/Z_k) and the Heisenberg nilmanifold.

hep-th↗