Linear and nonlinear interactions of an electromagnetic wave with molecules of an isotropic medium induce in them multipole moments which contribute to electric polarization of the system [1]. Out of absorption bands optical rectification (OR) via the second-order susceptibility is forbidden but the fourth-order dipolar electric nonlinearity may cause OR in chiral liquids [2]. However, in absor...

The present study was designed to find out to what extent imaginary companions are created in the diaries of adolescents. A total of 241 adolescents aged 12 to 17 years were investigated to determine the incidence as well as the characteristics and functions of such fictitious individuals in this age group. Content analysis of data obtained from questionnaires revealed that the imaginary compan...

Is the presence of foveal stimulation a necessary prerequisite for rhesus monkeys to perform visually guided eye movements? To answer this question, we trained two rhesus monkeys to direct their eyes towards imaginary targets defined by extrafoveal cues. Independent of the type of target, real or imaginary, the trajectory of target movement determined the type of eye movement produced: steps in...

This paper studies non-proper negative imaginary systems. First, the concept of negative imaginary transfer functions thatmayhavepoles at the origin and infinity is introduced. Then, a generalized lemma is presented to provide a sufficient condition to characterize the non-proper negative imaginary properties of systems. The generalized lemma is given in terms of complex variable s in the quart...

Sign type spectra are an important tool in the investigation of spectral properties of selfadjoint operators in Krein spaces. It is our aim to show that also sign type spectra for normal operators in Krein spaces provide insight in the spectral nature of the operator: If the real part and the imaginary part of a normal operator in a Krein space have real spectra only and if the growth of the re...

We work out the method for evaluating the QCD coupling constant at finite temperature (T ) by making use of the finite T renormalization group equation up to the one-loop order on the basis of the background field method with the imaginary time formalism. The background field method, which maintains the explicit gauge invariance, provides notorious simplifications since one has to calculate onl...

The occurrence of parity-time reversal PT symmetry breaking is discussed in a non-Hermitian spin chain. The Hermiticity of the model is broken by the presence of an alternating, imaginary, transverse magnetic field. A full real spectrum, which occurs if and only if all the eigenvectors are PT symmetric, can appear only in presence of dimerization, i.e., only if the hopping amplitudes between ne...