An Improved Quasi-Polynomial Algorithm for Approximate Well-Supported Nash Equilibria

We focus on the problem of computing approximate Nash equilibria in bimatrix games. In particular, we consider the notion of approximate well-supported equilibria, which is one of the standard approaches for approximating equilibria. It is already known that one can compute an ε-well-supported Nash equilibrium in time nO (log n/ε2), for any ε > 0, in games with n pure strategies per player. Such a running time is referred to as quasi-polynomial. Regarding faster algorithms, it has remained an open problem for many years if we can have better running times for small values of the approximation parameter, and it is only known that we can compute in polynomial-time a 0.6528-well-supported Nash equilibrium. In this paper, we investigate further this question and propose a much better quasi-polynomial time algorithm that computes a (1/2 + ε)-well-supported Nash equilibrium in time nO(log logn1/ε/ε2), for any ε > 0. Our algorithm is based on appropriately combining sampling arguments, support enumeration, and solutions to systems of linear inequalities.

On a regularity of biharmonic approximations to a nonlinear degenerate elliptic PDE

Under appropriate assumption on the coefficients, we prove that a sequence of biharmonic regularization to a nonlinear degenerate elliptic equation with possibly rough coefficients preserves certain regularity as the approximation parameter tends to zero. In order to obtain the result, we introduce a generalization of the Chebyshev inequality. We also present numerical example.

Singular solutions of a fully nonlinear 2 × 2 system of conservation laws

Existence and admissibility of δ-shock solutions is discussed for the non-convex strictly hyperbolic system of equationsThe system is fully nonlinear, i.e. it is nonlinear with respect to both unknowns, and it does not admit the classical Lax-admissible solution for certain Riemann problems. By introducing complex-valued corrections in the framework of the weak asymptotic method, we show that a compressive δ-shock solution resolves such Riemann problems. By letting the approximation parameter tend to zero, the corrections become real valued, and the solutions can be seen to fit into the framework of weak singular solutions defined by Danilov and Shelkovich. Indeed, in this context, we can show that every 2 × 2 system of conservation laws admits δ-shock solutions.

Hybrid Eigenfunction-Discretization Methodology for Solving Convective Heat Transfer Problems

This paper presents a novel methodology for the solution of problems that include diffusion and advection effects, as naturally occur in convective heat transfer problems. The methodology is based on writing the unknown temperature field in terms of eigenfunction expansions, as traditionally carried-out with the Generalized Integral Transform Technique (GITT). However, a different approach is used for handling advective derivatives. Rather than transforming the advection terms as done in traditional GITT solutions, upwind discretization schemes (UDS) are used prior to the integral transformation. With the introduction of upwind approximations, numerical diffusion is introduced, which can be used to reduce unwanted oscillations that arise at higher Péclet values. This combined methodology is termed the GITT-UDS for convective problems. The procedure is illustrated for a simple case of one-dimensional Burgers’ equation with temperature-dependent velocities. Numerical results are calculated, showing that augmenting the upwind approximation parameter can effectively reduce solution oscillations for higher Péclet values.

Application of MATLAB in Digital Signal Processing

The digital filter is one of the most significant applications of digital signal processing (DSP). The design process is very complex involving the model approximation, parameter selection, computer simulation and a series of work. This paper introduces an efficient design method for the digital filter (IIR and FIR) based on the Signal Processing Toolbox of MATLAB, which makes design easy, fast and greatly reduces the amount of design work, and then proves it by practical examples.

Continuous and Discontinuous Linear Approximation of the Window Spectrum by Least Squares Method

Continuous and Discontinuous Linear Approximation of the Window Spectrum by Least Squares Method This paper presents the general solution of the least-squares approximation of the frequency characteristic of the data window by linear functions combined with zero padding technique. The approximation characteristic can be discontinuous or continuous, what depends on the value of one approximation parameter. The approximation solution has an analytical form and therefore the results have universal character. The paper presents derived formulas, analysis of approximation accuracy, the exemplary characteristics and conclusions, which confirm high accuracy of the approximation. The presented solution is applicable to estimating methods, like the LIDFT method, visualizations, etc.