A note on moduli stabilisation in heterotic models in the presence of matter fields

In this brief note we analyse a toy model which can be derived from heterotic string compactifications on half-flat manifolds with SU(3)$\mathit{SU}(3)$ structure at first order in α^′${\alpha }^{\prime }$ (i.e. including matter fields). We show that for this model, finding solutions with viable gauge group poses the same problems as finding solutions in the absence of matter fields.     

An alternative method for CARS-spectra calculation

We propose an alternative method for CARS-spectra calculation. This kind of spectrum-calculation allows the decomposition of the CARS-intensity into physically interpretable components. The method is based on Yuratich's analysis of effects of laser linewidth on CARS-spectroscopy. With the help of an equivalent representation of the plasma-dispersion function the CARS-intensity can be expressed via a Fourier-transform in a very easy manageable form for numerical investigations. As an example we applied our method to the Q-branch-spectrum of N₂.     

An alternative form for Raychaudhuri's equation

Raychaudhuri's equation contains some features that deserve attention, such as the increase witht ² of the difference between half the density parameter and the deceleration parameter. We derive a form of the equation that shows how this happens.     

An alternative for polarized antiproton beams

Presently the most popular way to prepare high quality polarized antiproton beams is the so called spin filter method. The feasibility of the method has been proven for a proton beam and measurements of the spin dependent interaction of antiprotons have been proposed by the PAX collaboration. Another well known source for polarized antiprotons is the $\bar{\Lambda}$ decay which was used at FERMILAB in the only experiment performed so far with polarized antiprotons. An alternative approach for polarized antiproton beams may be the production process itself. If the produced antiprotons show polarization it would be rather simple to handle a polarized antiproton beam in the existing antiproton collector and cooler at CERN just like in the unpolarized case.     

An alternative method for plotting dispersion curves

Solving the frequency equation and plotting the dispersion curves in problems of wave propagation in cylinders and plates, particularly when the material is anisotropic, are complicated tasks. The traditional numerical methods are usually based on determination of the zeros of the frequency equation by using an iterative find-root algorithm. In this paper, an alternative method is proposed which extracts the solution of the frequency equation in the form of dispersion curves from the three-dimensional illustration of the frequency equation. For this purpose, a three-dimensional representation of the real roots of the frequency equation is first plotted. The dispersion curves, which are the numerical solutions of the frequency equation, are then obtained by a suitable cut in the velocity-frequency plane. The advantages of this method include simplicity, high speed, low possibility of numerical error, and presentation of the results in a graphical form that promotes ease of interpretation. This method is not directly applicable to problems which incorporate high damping or leaky waves. However, if the damping is not very high, it could be a good estimate of the true dispersion curves.     

An alternative model for the integral Quantum-Hall-Effect

A new model is proposed to explain the integral Quantum-Hall-Effect without invoking electron localisation. It is shown that this quantum effect is present in all two-dimensional systems, but can only be observed if the contributions to the Hall-voltage and total current arising from a possible internal electric potential are supressed. It is argued that this situation is indeed encountered in the devices used in the experiments. The time dependence of current and voltage are calculated and it is found that within linear response theory the Hall-resistanceR _H =U _y /I _x is quantised up to finite size corrections (l ²/L _y ² ) only for filling factors 0<v2, wherel ²=/eB andL _y is the width of the system. For larger filling factors additional small corrections are found. Experiments to test the competing theories are suggested.     

An alternative search strategy for interstellar communication

Are there any better wavelengths (or frequencies) for gathering information of extraterrestrial intelligence? In recent years scientists have realized that intelligent life may well be found throughout the universe and we are, perhaps, not the only civilization in our galaxy. The paper suggests an alternative search strategy of extraterrestrial life through sky noise windows emphasizing both the ‘water-holes’ and the associated wavelengths. It also suggests that instead of pointing the antenna at known stars, an all sky search would be more appropriate for interstellar communication.     

An alternative Biot's displacement formulation for porous materials

This paper proposes an alternative displacement formulation of Biot's linear model for poroelastic materials. Its advantage is a simplification of the formalism without making any additional assumptions. The main difference between the method proposed in this paper and the original one is the choice of the generalized coordinates. In the present approach, the generalized coordinates are chosen in order to simplify the expression of the strain energy, which is expressed as the sum of two decoupled terms. Hence, new equations of motion are obtained whose elastic forces are decoupled. The simplification of the formalism is extended to Biot and Willis thought experiments, and simpler expressions of the parameters of the three Biot waves are also provided. A rigorous derivation of equivalent and limp models is then proposed. It is finally shown that, for the particular case of sound-absorbing materials, additional simplifications of the formalism can be obtained.     

An alternative flexible electrode for dye-sensitized solar cells

With comparable transparency, flexibility, but a better conductivity, metal-mesh based PEN film provides an alternative low-cost electrode material to the conventional ITO/PEN film for flexible solar cell system. In this article, counter electrodes (CEs) prepared by coating metal-mesh/PEN with a mixture of PEDOT:PSS and carbon black nanoparticle (200?C400?nm) were utilized in flexible dye-sensitized solar cells (DSCs). A high efficiency of 5.5?% was achieved with the DSC based on the metal-mesh/PEN CE, rivaling that of the DSC based on ITO/PEN CE.     

The wall theorem for elastic moduli

New expressions for the elastic moduli of a classical system are derived. They involve only the two-point correlation function and the derivative of the onepoint correlation function, both only on the boundary of the system. These expressions, valid for any interaction derivable from a potential, are proved from a mechanical point of view by generalizing the virial theorem of Clausius, and from a statistical point of view by a direct method that constitutes an alternative to Green's dilatation method.     

An alternative for senile scaling in deep inelastic annihilation

DIA is studied in the frame of a simple EVMD model, yielding precocious scaling for DIS, together with good predictions for photoabsorption and vector meson photoproduction cross sections; we assume validity of the reciprocity relations, and in this model both senile scaling and large DIA cross sections emerge as consequences of strong mixing between the wide, overlapping vector meson levels in the high mass continuum.     

An alternative method for spectrum of a two-electron-quantum dot

The subject of quantum dot has received great theoretical attention because of many attractive features they exhibit in a large class of combinations and different methods have been used. In the present work, we consider a two-electron-quantum dot, obtain the quasi-exact analytical solution of corresponding Schrödinger equation and finally calculate the ground state and the excited state energy eigenvalues of the system by considering oscillating and linear confining terms as well as a Coulomb interaction between the two electrons. The present results are useful to study the optical and magnetic properties of such structures.     

An alternative method for spectrum of a three-electron-quantum dot

We consider the Hamiltonian of a three-electron-quantum dot composed of parabolic confinement plus Coulomb terms. Instead of using the Jacobi coordinates, we apply a unitary transformation to this system. To avoid the complexity, the Taylor expansion of the effective potential is introduced into the problem and thereby a solution is found for the eigenvalues of the corresponding three-body Schrödinger equation in terms of the Wigner parameter.     

An alternative quantum fidelity for mixed states of qudits

We give an alternative definition of quantum fidelity for two density operators on qudits in terms of their Hilbert-Schmidt inner product and their purity. It can be regarded as the well-defined operator fidelity for the two operators and satisfies all Jozsa's four axioms up to a normalization factor. This fidelity is not computationally demanding.     

An alternative approach to electrochemistry

The concepts used conventionally in electrochemistry, single-ion chemical potential and electrostatic potential difference, are not obtainable from measurements in an inhomogeneous system. The use of nonoperational and mutually dependent forces in flux equations has impeded our understanding of electrochemical processes, and has led to wrong conclusions. The equation for entropy production is derived using only operationally defined quantities, chemical potentials of neutral components and the electric potential measured with reversible electrodes. The electric potential enters calculations as external electric work in the first law of thermodynamics. From entropy production, flux equations are obtained where the forces are operationally defined, measurable quantities. Three different problems from electrochemistry are discussed, the liquid junction potential, the Donnan potential, and energy coversion in mitochondria. The conventional method of calculations and the operational method are compared. The operational method permits more detailed calculations of emf, and an understanding of the process from a different approach.     

SYZ duality for parabolic Higgs moduli spaces

We prove the SYZ (Strominger–Yau–Zaslow) duality for the moduli space of full flag parabolic Higgs bundles over a compact Riemann surface. In Hausel and Thaddeus (2003) [12], the SYZ duality was proved for moduli spaces of Higgs vector bundles over a compact Riemann surface.     

An alternative approach to field-aligned coordinates for plasma turbulence simulations

In this work, a new approach to field-aligned coordinates for plasma turbulence is presented, in which the position along the field lines is identified by the toroidal angle. The several advantages of the new approach are discussed. It is also shown that the approach can be generalised to get rid of magnetic coordinates in the poloidal plane altogether. Tests are carried out by comparing codes implementing a basic ion temperature gradient turbulence model with the old and the new methods. Results show an unexpected property of the model, that localized large parallel gradients can intermittently appear in the turbulent regime.