arXiv subjects
Publications and source records attributed to Takashi Nitta.
In this paper, we define a differential operator as a modified Dirac operator. Using the operator, we introduce a quaternionic $k$-vector field on a quaternionic Kähler manifold and show that any quaternionic $k$-vector field corresponds to a holomorphic $k$-vector field on the twistor space. We calculate the dimension of the space of quaternionic $k$-vector fields on $\mathbb{H}P^n$.
A Poisson structure is represented by a bivector whose Schouten bracket vanishes. We study a global Poisson structure on $S^4$ associated with a holomorphic Poisson structure on $\mathbb{CP}^3$. The space of the Poisson structures on $S^4$ is a real algebraic variety in the space of holomorphic Poisson structures on $\mathbb{CP}^3$. We generalize it to $\mathbb{HP}^n$ by using the twistor method. Furthermore, we provide examples of Poisson structures on $S^4$ associated with codimension one holomorphic foliations of degree 2 on $\mathbb{CP}^3$.
A complex contact structure $γ$ is defined by a system of holomorphic local $1$-forms satisfying the completely non-integrability condition. The contact structure induces a subbundle ${\rm Ker}\, γ$ of the tangent bundle and a line bundle $L$. In this paper, we prove that the sheaf of holomorphic $k$-vectors on a complex contact manifold splits into the sum of $\mathcal{O}(\bigwedge^{k}{\rm Ker}\, γ)$ and $\mathcal{O}(L\otimes \bigwedge^{k-1} {\rm Ker}\, γ)$ as sheaves of {\it $\mathbb{C}$-module}. The theorem induces the short exact sequence of cohomology of holomorphic $k$-vectors, and we obtain vanishing theorems for the cohomology of $\mathcal{O}(\bigwedge^{k} \ker γ)$.
The purpose is to formulate a Fourier transformation for the space of functionals, as an infinitesimal meaning. We extend ${\bf R}$ to $ ^{\star}(^{\ast}{\bf R})$ under the base of nonstandard methods for the construction. The domain of a functional is the set of all internal functions from a $ ^{\ast}$-finite lattice to a $ ^{\ast}$-finite lattice with a double meaning. Considering a $ ^{\ast}$-finite lattice with a double meaning, we find how to treat the domain for a functional in our theory of Fourier transformation, and calculate two typical examples.
In our last work, we formulate a Fourier transformation on the infinite-dimensional space of functionals. Here we first calculate the Fourier transformation of infinite-dimensional Gaussian distribution $\exp(-πξ\int_{-\infty}^{\infty}α^2(t)dt)$ for $ξ\in{\bf C}$ with Re$(ξ)>0$, $α\in L^2({\bf R})$, using our formulated Feynman path integral. Secondly we develop the Poisson summation formula for the space of functionals, and define a functional $Z_s$, $s\in {\bf C}$, the Feynman path integral of that corresponds to the Riemann zeta function in the case Re$(s)>1$.
We prove that the connected sums CP_2 # CP_2 and CP_2 # CP_2 # CP_2 admit self-dual metrics with positive Ricci curvature. Moreover, every self-dual metric of positive scalar curvature on CP_2 # CP_2 is conformal to a metric with positive Ricci curvature.