## Conference submissions

#### Resolving non-homogeneous linear differential equations using undetermined coefficients and variation of parameters by means of GeoGebra

Jorge Olivares Funes 1

1Universidad de Antofagasta , Departamento de Matemáticas , Chile

###### Abstract

In this paper, we show how non-homogeneous linear differential equations, especially those of the second order, are solved by means of GeoGebra applets by indeterminate coefficient methods and variation of parameters, for the course of differential equations of engineering students. and pedagogy in mathematics from the University of Antofagasta in Chile. The free software GeoGebra has caused that it is increasingly used in the teaching of mathematics, especially in non-homogeneous linear differential equations, because it facilitates the teaching and learning process.

#### Quantum Field Theory in fractal space-time with negative dimension.

Jaykov Foukzon1

1Israel Institute of Technology, Department of mathematics, Israel

###### Abstract

We introduce Hausdorff-Colombeau measure in respect with negative fractal dimensions. Axiomatic quantum field theory in spacetime with negative fractal dimensions is proposed.Spacetime is modelled as a multifractal subset of $R^{4}$ with positive and negative fractal dimensions.The cosmological constant problem arises because the magnitude of vacuum energy density predicted by quantum field theory is about 120 orders of magnitude larger than the value implied by cosmological observations of accelerating cosmic expansion. We pointed out that the fractal nature of the quantum space-time with negative Hausdorff-Colombeau dimensions can resolve this tension. The classical Quantum Field Theory is widely believed to break down at some fundamental high-energy cutoff $E$ and therefore the quantum fluctuations in the vacuum can be treated classically seriously only up to this high-energy cutoff. In this paper we argue that Quantum Field Theory in fractal space-time with negative Hausdorff- Colombeau dimensions gives high energy cutoff on natural way. In order to obtain disered physical result we apply the canonical Pauli-Villars regularization up to $E$. It means that there exist the ghost-driven acceleration of the univers hidden in cosmological constant. http://arxiv.org/abs/1004.0451

#### The numerical analysis placement method with GeoGebra in linear second order differential equations

Jorge Olivares Funes 1 , Luis Cortés Vega2 , Pablo Martin3 , Elvis Valero4

1Universidad de Antofagasta , Departamento de Matemáticas , Chile
2University of Antofagasta, matemáticas, Chile
3University of Antofagasta, Physics department, Chile

###### Abstract

In this article we will show how to find approximate solutions, using the numerical analysis placement method with the GeoGebra software to the second order linear differential equations of the form d^2y/dx^2+A(x)dy/dx+B (x)y=Q (x), y (0) = y (a) = 0, where "a" is a positive number. The use of GeoGebra in the numerical analysis allows us to simultaneously, interactively and dynamically view the solutions and approximations of the differential equations.

#### The error function in fractional differential equations

Jorge Olivares Funes 1 , Pablo Martin2 , Fernando Maass3 , Elvis Valero4

1Universidad de Antofagasta , Departamento de Matemáticas , Chile
2University of Antofagasta, Physics department, Chile
3University of Antofagasta, Physics department, Chile

###### Abstract

Fractional differential equations have a great importance and application. That is why the relationship between the fractional derivative and the erf (x) function will be shown below. The objective of this work is to solve the fractional differential equation D ^α y (x) =erf (x), and y(0) = 0, where 0<α<1. We will show the type of generalized hypergeometric solutions obtained by defining the fractional derivative of Caputo and the Laplace transform.

#### New quasi-rational aproximation for the modified Bessel functions I1(x).

Pablo Martin1 , Jorge Olivares2 , Adrian Sotomayor3

###### Abstract

New and more accurate approximation to the modified Bessel function I1 has been found by improving the multipoint quasi -rational approximation method, MPQA. The approximation obtained in previous work (1) , has been improved by using the hyperbolic function sinh, instead of cosh. This change also the structure of the approximation , but there is not change in the structure of the approximation , and the number of parameters is also equal.Three terms of the power series and one term of the asymptotic expansion are also used to obtain the parameters of the approximation. In this way there is a decreasing of the relative error from 0.011 to 0.007 . A detail explication of the new procedure is carry on in this presentation. Ref. P. Martin, J. Olivares and A. Sotomayor, “ Precise Analytic Approximation for the Modified Bessel Function I1”, Rev. Mex. Física 63 (2017) 130- 133 .

#### The solution classical feedback optimal control problem without the Bellman Equation

Jaykov Foukzon1

1Israel Institute of Technology, Department of mathematics, Israel

###### Abstract

A new approach, which is proposed in this paper allows one to construct the Bellman function V(t,x) and optimal control u(t) directly,i.e.,without any reference to the Bellman equation, by way of using strong large deviations principle for the solutions Colombeau-Ito's SDE.

#### Solution to the Troesch Problem for Boundary Equations.

Franco Lindstron1

1Universidad Nacional de La Plata, Matemática, Argentina

###### Abstract

This paper shows, for the first time, that the explicit and exact solution to the Troesch nonlinear twopoint boundary value problem may be computed in a direct and straightforward fashion from the general solution obtained by a generalized Sundman transformation for the related differential equation, which appeared to be a special case of a more general equation. As a result, various initial and boundary value problems may be solved explicitly and exactly.

#### Inverse operator of a chaotic dynamics

yehuda roth1

1Oranim college, science, Israel

###### Abstract

It is known that a dissipative environment is well described by the chaotic process while regular dynamics is associated with animate systems. In this paper, we explore the inverse map of some chaotic maps to find that they are always regular. The result that by reversing a chaotic map we obtain a regular process is associated with the birth of animate systems.

#### Modelling meson clouds using coherent states

Manuel Fiolhais1

1University of Coimbra, Department of Physics, Portugal

###### Abstract

The use of coherent states to describe boson systems goes back to the 1960's in the context of the radiation field. Since the 1970's, they have also been applied to meson clouds, mainly pions, in the context of the description of baryons by means of effective models involving a quark core surrounded by scalar and pseudo-scalar mesons. The use of coherent states allows for an {\em ab-initio} quantum mechanical description of the mesons, therefore going beyond semi-classical approximations. The coherent state e.g. for p-wave pions (with angular momentum and isospin quantum numbers both equal to 1) is given by $|\psi > = {\cal N}(\xi) \exp (\sum_{tm} \xi_{tm} a^\dagger _{tm} ) |B>$ where ${\cal N}$ is a normalization factor, $| B >$ is a bare baryon state and $\xi_{tm}$ are amplitudes to be determined variationally. The $a^\dagger _{tm}$ is the creation operator for a pion state with angular momentum third component, $m$, and isospin third component, $t$. The radial profile of the pion amplitude results from a variational calculation and it is frozen. Hence, only angular momentum and isospin matters to construct the coherent state above. As already mentioned, the idea of mathematically modelling the meson clouds by means of coherent states, having in mind a full quantum mechanical description of baryon systems in the framework of chiral effective models, is not new. Actually, the author, among others, published several papers on the topic, in order to obtain various properties of the nucleon, the delta resonance and other excited states. However, the goal here is to bring together many aspects that are scattered in the literature, focusing on the versatility of the coherent states and stressing their capabilities. In this study, instead of the more realistic chiral effective models of quarks and mesons, we use a toy model whose Hamiltonian is written as $H= \sum_{tm} a^\dagger_{tm} a_{tm} + G \sum _{tm} B_{tm} \left[ a_{tm} + (-1)^{t+m} a_{-t-m}^\dagger \right]\!,$ where $B_{tm}$ is a baryon spin-isospin operator. The model describes a system of non self-interacting pions linearly coupled to a bare baryon core, $G$ being the coupling constant. This model is simple enough for its exact solutions to be worked out in the strong and weak regimes. These accurate solutions are then compared with the variational approximate solutions. Because the multi-particle coherent state, $|\psi>$, cannot directly describe a nucleon, with definite angular momentum and isospin quantum numbers $\left( J={1\over 2}, I={1\over 2} \right)$, the Peiers-Yoccoz angular momentum (and isospin) projection method is used to construct a state, $|\psi_N>$, with the proper nucleon quantum numbers. The variational method consists in minimizing the energy with respect to the amplitudes, i.e. $d< H > / d \xi_{tm}=0$, with the normalization condition $<\psi_N|\psi_N>=1$ dully implemented in the process. We show that the so-called hedgehog configuration for the quark core and for the pion amplitudes minimizes the mean-field energy. On the other hand, we show that the (Peierls-Yoccoz) projected coherent state is an extremely powerful ansatz since it reproduces the accurate solutions of the model both in the strong coupling regime (which is not surprising) but also in the weak coupling regime. We emphasise the use of the variation-after-projection method, for which the variational Hilbert space is larger, therefore with the trial function spanning a larger space than in the simpler variation-before-projection method. The toy model turns out to be a valuable tool to test different approaches which might be used in more realistic models with, for instance, self-interacting mesons.

#### Free vibrations of isotropic FG porous annular and elastically restrained plate using DQM

Yajuvindra Kumar 1

1Government Girls Degree College, Behat, Mathematics, India

###### Abstract

In this paper, author studied free vibrations of a functionally graded (FG) annular plate having porosity. The plate is elastically restrained along the boundary. The material properties of the plate are Porosity dependent. An even porosity distribution is taken in the analysis. The mathematical model of the problem is developed using the concept of physical neutral surface of the plate. The physical neutral surface is taken as the reference plane. Out of many, only first three natural frequencies of the plate are reported using differential quadrature method (DQM). A parametric study is conducted to show the effects of porosity and material distribution parameters on the vibration behavior of the plate.

#### Integration of electromagnetic methods of intuba-tion of stratified mediums on the basis of direct and alternating currents

Yuriy Dimitrienko1 , Igor Krasnov2 , Kirill Zubarev3

1Bauman Moscow State Techical University, Fundamental sciences, Russian Federation
2Bauman Moscow State Techical University, Fundamental sciences, Russian Federation
3Bauman Moscow State Techical University, Fundamental sciences, Russian Federation

###### Abstract

In this work the integration of two methods of electroinves-tigation is considered. One method represents intubation by a direct current, the second intubation by alternating cur-rent. The integration is carried out for the purpose of in-crease in accuracy of results of the solution of the inverse task, the problem is solved in a twodimensional approxima-tion. The direct task for the first and second method is solved numerically. The received values were compared with the experimental datas. The inverse task is formulated as a problem of minimization with the functional considering the experimental values received by both the first and second method of electroinvestigation. The problem of optimization is solved on a compact (for each parameter are set top and bottom border).