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Abstract. In this paper, the consimilarity of complex matrices is generalized for commutative quaternion matrices. In this regard, the coneigenvalue and coneigenvector for commutative quaternion matrices are defined. Also, the existence of solution to the some commutative quaternion matrix equations is characterized and solutions of these matrix equations are derived by means of real representations of commutative quaternion matrices.

In this paper, we study trajectory ruled surface of a curve with singular points in the Euclidean 3‐space as an application of singularity theory of a space curve with singular points. By considering notion of framed curve, we investigate the trajectory ruled surface and give some results about invariants of these surfaces. Then, we give some examples of trajectory ruled surfaces. Moreover, we determine local diffeomorphic image of these surfaces.

In this paper, we construct a helicoidal surface of type I+ with prescribed weighted mean curvature and Gaussian curvature in the Minkowski 3−space ${\Bbb R}_1^3$with a positive density function. We get a result for minimal case. Also, we give examples of a helicoidal surface with weighted mean curvature and Gaussian curvature.

The resolution of the acceleration vector of rigid body moving along a space curve is well known thanks to Siacci [1]. In this resolution, the acceleration vector is stated as the sum of two special oblique components in the osculating plane of the point of the curve. In this paper, we have studied the Siacci’s theorem for the curves on regular surfaces in 3-dimensional Euclidean space. Also, an example is given for a helix lying on a cylinder.

In [10] one-parameter planar motion was first introduced and the relations between absolute, relative, sliding velocities (and accelerations) in the Euclidean plane E 2 were obtained. Moreover, the relations between the complex velocities of one-parameter motion in the complex plane were provided by [10]. One-parameter planar homothetic motion was defined in the complex plane, [9]. In this paper, analogous to homothetic motion in the complex plane given by [9], one-parameter planar homothetic motion is defined in the hyperbolic plane. Some characteristic properties about the velocity vectors, the acceleration vectors and the pole curves are given. Moreover, in the case of homothetic scale h identically equal to 1, the results given in [15] are obtained as a special case. In addition, three hyperbolic planes, of which two are moving and the other one is fixed, are taken into consideration and a canonical relative system for one-parameter planar hyperbolic homothetic motion is defined. Euler-Savary formula, which gives the relationship between the curvatures of trajectory curves, is obtained with the help of this relative system.Mathematics Subject Classification (2010). 53A17, 11E88.

We give the definition of generalized timelike Mannheim curve in Minkowski space-time . The necessary and sufficient conditions for the generalized timelike Mannheim curve are obtained. We show some characterizations of generalized Mannheim curve.