An algorithm to extract the square root in radicals from a multivector (MV) in real Clifford algebras Cl(p,q) for n=p+q <=3 is presented. We show that in the algebras Cl(3,0), Cl(1,2) and Cl(0,3) there are up to four isolated roots in a case of the most general (generic) MV. The algebra Cl(2,1) makes up an exception and the MV here can have up to 16 isolated roots. In addition to isolated roots, a continuum of roots can appear in all algebras except p+q=1. A number of examples are provided to illustrate properties of various roots that may appear in n=3 Clifford algebras.

Square roots of real and complex (complexified) quaternions, namely, the Hamilton's quaternion, coquaternion, nectorine, and conectorine are investigated. The isomorphism between the quaternions and multivectors in Clifford algebras is employed for this purpose. Root examples for all named quaternions are presented from which follows that the real and complex quaternionic roots may assume multiple discrete or continuous forms, or there may be no roots at all.

Square roots of complexified (complex) quaternions, namely, the Hamilton quaternion, coquaternion, nectorine, and conectorine are investigated. The isomorphisms between the complex quaternions and 3-dimensional multivectors of Clifford algebras is employed for this purpose. Root examples for all named quaternions are presented from which follows that the complex quaternionic roots may assume discrete or continuous form, or there may be no roots at all.

The problem of multivector (MV) multiple square roots in real geometric Clifford algebras Cl(p,q) with symbolic coefficients is considered. The method to find multiple MV square roots that is based on R.Bott's periodicity table and matrix eigensystem in Cl(p,q) is proposed. The method can be applied to MV having both numerical and symbolic coefficients. In addition, method allows to determine the domain of the existence of thus obtained spectral square roots. A number of examples is presented for multivectors in low, p+q<= 3, and higher dimensional Clifford algebras, including 4D (anti)-Euclidean space and relativistic Cl(1,3) and Cl(3,1) algebras. Tables of the required basis vectors for conversion of MV to Bott's matrix representation have been found from respective algebra idempotents using ideal theory and presented for real Clifford algebras in Appendix.

Closed form expressions in real Clifford geometric algebras Cl(0,3), Cl(3,0), Cl(1,2), and Cl(2,1) are presented in a coordinate-free form for exponential function when the exponent is a general multivector. The main difficulty in solving the problem is connected with an entanglement (or mixing) of vector and bivector components a and a in a form (a-a), i≠ j≠ k . After disentanglement, the obtained formulas simplify to the well-known Moivre-type trigonometric/hyperbolic function for vector or bivector exponentials. The presented formulas may find wide application in solving GA differential equations, in signal processing, automatic control and robotics.

Closed form expressions for a logarithm of general multivector (MV) in basis-free form in real geometric algebras (GAs) Clp,q are presented for all n = p + q = 3. In contrast to logarithm of complex numbers (isomorphic to Cl0,1), 3D logarithmic functions, due to appearance of two double angle arc tangent functions, allow to include two sets of sheets characterized by discrete coefficients. Formulas for generic and special cases of individual blades and their combinations are provided.

Formulas to calculate multivector exponentials in a base-free representation and in a orthonormal basis are presented for an arbitrary Clifford geometric algebra Cl(p,q). The formulas are based on the analysis of roots of characteristic polynomial of a multivector. Elaborate examples how to use the formulas in practice are presented. The results may be useful in the quantum circuits or in the problems of analysis of evolution of the entangled quantum states.

Formulas to calculate multivector exponentials in a base-free representation and in a given orthogonal basis are presented for an arbitrary Clifford geometric algebra $$ Cl _{p,q}$$ . The formulas are based on the analysis of roots of the characteristic polynomial of a multivector exponent. Elaborate examples how to use the formulas in practice are presented. The results may be useful in theory of quantum circuits or in the problems of analysis of evolution of the entangled quantum states.

Formulas to calculate multivector exponentials in a base-free representation and in a given orthogonal basis are presented for an arbitrary Clifford geometric algebra . The formulas are based on the analysis of roots of the characteristic polynomial of a multivector exponent. Elaborate examples how to use the formulas in practice are presented. The results may be useful in theory of quantum circuits or in the problems of analysis of evolution of the entangled quantum states.

Closed form expressions to calculate the exponential of a general multivector (MV) in Clifford geometric algebras (GAs) Clp;q are presented for n = p + q = 3. The obtained exponential formulas were applied to find exact GA trigonometric and hyperbolic functions of MV argument. We have verified that the presented exact formulas are in accord with series expansion of MV hyperbolic and trigonometric functions. The exponentials may be applied to solve GA differential equations, in signal and image processing, automatic control and robotics.

Closed form expressions for a multivector exponential and logarithm are presented in real Clifford geometric algebras Cl(p,q)when n=p+q=1 (complex and hyperbolic numbers) and n=2 (Hamilton, split and conectorine quaternions). Starting from Cl(0,1) and Cl(1,0) algebras wherein square of a basis vector is either -1 or +1, we have generalized exponential and logarithm formulas to 2D quaternionic algebras, Cl(0,2), Cl(1,1), and Cl(2,0). The sectors in the multivector coefficient space where 2D logarithm exists are found. They are related with a square root of the multivector.

The aim of the paper is to give a uniform picture of complex, hyperbolic, and quaternion algebras from a perspective of the applied Clifford geometric algebra. Closed form expressions for a multivector exponential and logarithm are presented in real geometric algebras Clp;q when n = p + q = 1 (complex and hyperbolic numbers) and n = 2 (Hamilton, split, and conectorine quaternions). Starting from Cl0;1 and Cl1;0 algebras wherein square of a basis vector is either –1 or +1, we have generalized exponential and logarithm formulas to 2D quaternionic algebras Cl0;2, Cl1;1, and Cl2;0. The sectors in the multivector coefficient space, where 2D logarithm exists are found. They are related with a square root of the multivector.

The problem of square root of multivector (MV) in real 3D (n = 3) Clifford algebras Cl3;0, Cl2;1, Cl1;2 and Cl0;3 is considered. It is shown that the square root of general 3D MV can be extracted in radicals. Also, the article presents basis-free roots of MV grades such as scalars, vectors, bivectors, pseudoscalars and their combinations, which may be useful in applied Clifford algebras. It is shown that in mentioned Clifford algebras, there appear isolated square roots and continuum of roots on hypersurfaces (infinitely many roots). Possible numerical methods to extract square root from the MV are discussed too. As an illustration, the Riccati equation formulated in terms of Clifford algebra is solved.

Hamiltonian and eigenstate problem is formulated for a bilayer graphene in terms of Clifford's geometric algebra Cl_3,1. It is shown that such approach allows to perform analytical calculations in a simple way if geometrical algebra rotors are used. The measured quantities are express through spectrum and rotation half-angle of the pseudospin that appears in geometric algebra rotors. Properties of free charge carriers – pseudospin, velocity and Berry phase – in a bilayer graphene are investigated in the presence of the external voltage applied between the two layers.

A simple method of temperature and electron density measurement in quasi-equilibrium plasma at temperatures below 10 kK from the ratio of mass spectrometric signals of the doubly and singly ionized ions of Ba and Pb has been proposed. High masses of the ions and possibility to select the odd isotopes makes it possible to perform measurements at a low mass resolution and low concentrations of the test elements. For atmospheric pressure plasmas at temperatures from 3500K to 8000K the temperature can be determined from the relation T=19,443 (log (NBa++/NBa+(NPb++/NPb+))(-0.871). Sources of uncertainty and accuracy of the results have also been discussed. (C) 2014 Elsevier B.V. All rights reserved.

We introduce a one-dimensional two-component system with the self-focusing cubic nonlinearity concentrated at a symmetric set of two spots. Effects of the spontaneous symmetry breaking (SSB) of localized modes were previously studied in the single-component version of this system. In this work, we study the evolution (in the configuration space of the system) and SSB scenarios for two-component modes of three generic types, as concerns the spatial symmetry of each component: symmetric–symmetric (Sm–Sm), antisymmetric–antisymmetric (AS–AS), and symmetric–antisymmetric (S–AS) ones. In the limit case of the nonlinear potential represented by two δ-functions, solutions are obtained in a semi-analytical form. They feature novel properties, in comparison with the previously studied single-component model. In particular, the SSB of antisymmetric modes is possible solely in the two-component system, and, obviously, S–AS states exist only in the two-component system too. In the general case of the symmetric pair of finite-width nonlinear potential wells, evolution scenarios are very complex. In this case, new results are reported, first, for the single-component model. These are pairs of broken-antisymmetry modes, and of twin-peak symmetric ones, which are generated by saddle-mode bifurcations separated from the transformations previously studied in the single-component setting. With regard to these findings, complex scenarios of the evolution of the two-component solution families are realized in terms of links connecting pairs of modes of three simplest types: (A) two-component ones with unbroken symmetries; (B) single-component modes featuring density peaks in both potential wells; (C) single-component modes which are trapped, essentially, in a single well.

Essentially higher ionization degree of small concentrations of elements in inductively coupled plasma in comparison to the ionization of pure elements is emphasized. This conclusion is used to determine the relative dependence of the sensitivity of the inductively coupled plasma mass spectrometer on the atomic mass. The possibility of evaluation of the ionization temperature and electron density from mass spectrometric signals is proposed. Temperatures about 7000K and 8000K were obtained from the ionization ratio dependences on ionization potentials. Electron densities of the order of magnitude 1015cm−3, in excess to the local thermodynamic equilibrium values, follow from the application of the Saha equation to the measurement results and indicate the recombining character of the plasma in the mass spectrometer measurement region. Effects due to additional ionization from matrix were discussed. The effect is largest on minor abundant ionization state components. Matrix effect is restricted to some temperature interval, which depends on the whole matrix composition and the plasma state. The results show that the local thermodynamic equilibrium modeling, if adequately matching the sample composition, can be useful as a quantitative basis for both description of the plasma state and indication of the character of the nonequilibrium effects.

For the distance learning and scientific cooperation the possibility to run software by Internet is essential. WebMathematica represents technically the most complex part of the website mokslasplius. It (Scienceplus.lt), where a number of sophisticated interactive experiments from diverse areas of physics is realized. Enhanced by specially designed php-webMathematica module, it enables the realization of step-by-step training style pages where many of the intermediate steps can be evaluated and stored with the intention for later reuse in the process of presentation. AnyLogic software package allows one to develop interactive models of various physical systems of different nature: continuous, discrete or hybrid, and publish these models as java applets directly into Internet. We do present examples of web based interactive models collected under the title 'Physics of Risk" - the new field of the applications of physics in social sciences and complexity.The article also analyses integration of various software packages, as open source content management system Drupal, server-side software (Tomcat server, webMatematica), java applets, specialized computer modelling tools for purposes of e-Learning, science popularisation and dissemination of educational information, paying particular attention to the easiness of access to the content of portal, its usability for practical educational processes, and visual appeal.