A classification of all possible realizations of the Galilei, Galilei-similitude and Schrödinger Lie algebras in three dimensional space-time in terms of vector fields under the action of the group of local diffeomorphisms of the space R3 × C is presented. Using this result a variety of general second order evolution equations invariant under the corresponding groups are constructed and their p...

A general method to easily build global and relative operators for any number n of elementary systems if they are defined for 2 is presented. It is based on properties of the morphisms valued in the tensor products of algebras of the kinematics and it allows also the generalization to any n of relations demonstrated for two. The coalgebra structures play a peculiar role in the explicit construc...

baradaran rafii ar, md; motevasseli t, md*; yazdizadeh f, md; ansari sh, md; karimian f, md; sadoughi mm, md; kiani h ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran * corresponding author: [email protected] purpose: to compare anterior segment indices measured by two scheimpflug camera; galilei and pentacam. methods: in this observa...

A solution of the sourceless Einstein's equation with infinite values for the cosmological constant Λ and for the speed of light c is discussed by using Inönü–Wigner contractions of the de Sitter groups and spaces. When Λ → ∞, spacetime becomes a four–dimensional cone, dual to Minkowski space by a spacetime inversion. This inversion relates the four–cone vertex to the infinity of Minkowski spac...

both anorganic bovine bone (abb) and β-tricalcium phosphate (β-tcp) are used in clinical practice as bone substitute materials, but there is limited data comparing these two materials in standardized defects. the aim of this study was to histologically evaluate the effectiveness of abb and β-tcp in the healing of experimentally induced bone defects.eighteen bone defects were created on the calv...

PURPOSE To compare corneal thickness measurements using Pentacam (Oculus, Germany), Sirius (CSO, Italy), Galilei (Ziemer, Switzerland), and RTVue-100 OCT (Optovue Inc., USA). METHODS Sixty-six eyes of 66 healthy volunteers were enrolled. Three consecutive measurements were performed with each device. The mean value of the three measurements was used for subsequent analysis. Central corneal th...

The Landau problem in the noncommutative plane is discussed in the context of realizations of the two-fold centrally extended planar Galilei group and the anyon theory. In 2+1 dimensions, Galilei group admits a two-fold central extension [1, 2] characterized by the algebra with the nonzero Poisson bracket relations {Ki,Pj} = mδij, {Ki,Kj} = −κǫij , (1) {Ki,H} = Pi, {J ,Pi} = ǫijPj , {J ,Ki} = ǫ...

Purpose. To compare anterior corneal keratometry (K) measurements taken by a dual Scheimpflug analyzer and an auto kerato-refractometer. Methods. Sixty-four normal eyes underwent keratometric measurements with both devices. The repeatability of the auto kerato-refractometer measurements was assessed by calculating the coefficient of variation (COV). The interdevice agreement was evaluated using...