As a new aspect of the Arnold strange duality among 14 unimodal singularities, we point out that there exists a duality in linking pairing on Seifert manifolds associated with singularities.

Let $p$ be a prime and $L$ an $A_{n}$-extension over a number field $K$. The aim of this paper is to estimate the ratio of the $p$-class number of $L$ to the ambiguous $p$-class number of $L$ with respect to $K$.

This paper is concerned with Dedekind sums in finite characteristic. We introduce Dedekind sums for lattices, and establish the reciprocity law for them.

The resultant of two tropical polynomials satisfies the similar properties to the resultant of two polynomials over a field.

Kobayashi’s multiplicity-free theorem asserts that irreducible unitary highest weight representations $\pi$ are multiplicity-free when restricted to any symmetric pairs if $\pi$ is of scalar type. The Hua–Kostant–Schmid–Kobayashi branching laws embody this abstract theorem with explicit irreducible decomposition formulas of holomorphic discrete series representations with respect to symmetric pairs. In this paper, we study the ‘classical limit’ (geometry of coadjoint orbits) of a special case of these representation theoretic theorems in the spirit of the Kirillov–Kostant–Duflo orbit method. \\ First, we consider the Corwin–Greenleaf multiplicity function $n (\mathcal{O}^{G},\,\mathcal{O}^{K})$ for Hermitian symmetric spaces $G/K$. The first main theorem is that $n(\mathcal{O}^{G},\,\mathcal{O}^{K}) \le 1$ for any $G$-coadjoint orbit $\mathcal{O}^{G}$ and any $K$-coadjoint orbit $\mathcal{O}^{K}$ if $\mathcal{O}^{G} \cap \sqrt{-1} ([\mathfrak{k}, \mathfrak{k}] + \mathfrak{p})^{\bot} \ne \emptyset$. Here, $\mathfrak{g} = \mathfrak{k} + \mathfrak{p}$ is the Cartan decomposition of the Lie algebra $\mathfrak{g}$ of $G$. The second main theorem is a necessary and sufficient condition for $n (\mathcal{O}^{G},\,\mathcal{O}^{K}) \ne 0$ by means of strongly orthogonal roots.

In this paper, we investigate some aspects of representation theory of reductive groups over non-algebraically closed fields. Namely, we state and prove relative versions of well-known theorems of Bogomolov and of Sukhanov, which are related to observable and quasi-parabolic subgroups of linear algebraic groups over non-algebraically closed perfect fields.

We classify irreducible complex symmetric spaces that admit proper $SL(2,\mathbf{C})$-actions.$^{*}$

We present three new proofs of the trace theorem of $L_{p}$ Sobolev spaces, which do not rely on the theory of interpolation spaces. The first method originates in Morrey’s proof for the Sobolev embedding theorem concerning the Hölder-Zygmund space. The second method is based on Muramatu’s integral formula and the third method is based on an integral operator with Gauss kernel. These methods give unified viewpoints for the proofs of the trace theorem and the Sobolev embedding theorem.

For a certain quartic polynomial, there exists a homeomorphism between the set of all components of the filled-in Julia set with the Hausdorff metric and some subset of the corresponding symbol space with the ordinary metric. But these sets are not compact with respect to each metric. We introduce a new topology with respect to which these sets are compact.

In this paper we consider a system of equations describing the one-dimensional motion of a self-gravitating, radiative and chemically reactive gas having the free-boundary. For arbitrary large, smooth initial data we prove the unique existence, global in time, of a classical solution of the corresponding problem with fixed domain, obtained by the Lagrangian mass transformation.

In this paper, we treat with an arbitrary given connection $D$ which is not necessarily \textit{metric} or \textit{torsion-free} in the tangent bundle $TM$ over an $n$-dimensional closed (compact and connected) Riemannian manifold $(M,g)$. We find the fact that if any connection $D$ with Weyl structure $(D,g,\omega)$ relative to a 1-form $\omega$ in the tangent bundle is a Yang-Mills connection, then $d\omega=0$. Moreover under the assumption $\sum_{i=1}^{n}[\alpha(e_{i}),R^{D}(e_{i},X)]=0$ $(X \in \mathfrak{X}(M))$, a necessary and sufficient condition for any connection $D$ with Weyl structure $(D,g,\omega)$ to be a Yang-Mills connection is $\delta_{\nabla}R^{D}=0$, where $\{e_{i}\}_{i=1}^{n}$ is an (locally defined) orthonormal frame on $(M,g)$ and $D-\nabla = \alpha \in \Gamma (\bigwedge TM^{\ast} \otimes \mathrm{End}(TM))$, and $\nabla$ is the Levi-Civita connection for $g$ of $(M,g)$.