We consider the massless Dirac operator $H=\alpha \cdot D+Q(x)$ on the Hilbert space $L^{2}(\mathbb{R}^{3},\mathbb{C}^{4})$, where $Q(x)$ is a $4\times4$ Hermitian matrix valued function which… Expand

Abstract. A new species of heteromorph ammonoid Eubostrychoceras valdelaxum sp. nov. is described from the Platyceramus japonicus Zone (the lowermost Campanian) of the Haboro and Mikasa areas in… Expand

Abstract. A possible phylogenetic relationship of two species of Hyphantoceras (Ammonoidea, Nostoceratidae) was proposed, based on newly found specimens with precise stratigraphic occurrences in the… Expand

Time dependent d-dimensional Schrödinger equations i∂tu = H(t)u, H(t) = −(∂x − iA(t, x))2 +V (t, x) are considered in the Hilbert space G = L2(Rd) of square integrable functions. V (t, x) and A(t, x)… Expand

In order to test the hypothesis that complex suture lines in ammonoids reinforced their shell strength, intraspecific variation of sutural complexity and shell morphologies (whorl shape and septal… Expand