Exploring W∞\mathcal{W}_{\infty} in the quadratic basis

We study the operator product expansions in the chiral algebra $\mathcal{W}_{\infty}$, first using the associativity conditions in the basis of primary generating fields and second using a different basis coming from the free field representation in which the OPE takes a simpler quadratic form. The results in the quadratic basis can be compactly written using certain bilocal combinations of the generating fields and we conjecture a closed-form formula for the complete OPE in this basis. Next we show that the commutation relations as well as correlation functions can be easily computed using properties of these bilocal fields. In the last part of this paper we verify the consistency with results derived previously by studying minimal models of $\mathcal{W}_{\infty}$ and comparing them to known reductions of $\mathcal{W}_{\infty}$ to $\mathcal{W}_N$. The results we obtain illustrate nicely the role of triality symmetry in the representation theory of $\mathcal{W}_{\infty}$.Comment: 60 pages, 2 figure

Augmented reality usage for prototyping speed up

The first part of the article describes our approach for solution of this problem by means of Augmented Reality. The merging of the real world model and digital objects allows streamline the work with the model and speed up the whole production phase significantly. The main advantage of augmented reality is the possibility of direct manipulation with the scene using a portable digital camera. Also adding digital objects into the scene could be done using identification markers placed on the surface of the model. Therefore it is not necessary to work with special input devices and lose the contact with the real world model. Adjustments are done directly on the model. The key problem of outlined solution is the ability of identification of an object within the camera picture and its replacement with the digital object. The second part of the article is focused especially on the identification of exact position and orientation of the marker within the picture. The identification marker is generalized into the triple of points which represents a general plane in space. There is discussed the space identification of these points and the description of representation of their position and orientation be means of transformation matrix. This matrix is used for rendering of the graphical objects (e. g. in OpenGL and Direct3D).Comment: Keywords: augmented reality, prototyping, pose estimation, transformation matri

Augmented Reality Implementation Methods in Mainstream Applications

Augmented reality has became an useful tool in many areas from space exploration to military applications. Although used theoretical principles are well known for almost a decade, the augmented reality is almost exclusively used in high budget solutions with a special hardware. However, in last few years we could see rising popularity of many projects focused on deployment of the augmented reality on different mobile devices. Our article is aimed on developers who consider development of an augmented reality application for the mainstream market. Such developers will be forced to keep the application price, therefore also the development price, at reasonable level. Usage of existing image processing software library could bring a significant cut-down of the development costs. In the theoretical part of the article is presented an overview of the augmented reality application structure. Further, an approach for selection appropriate library as well as the review of the existing software libraries focused in this area is described. The last part of the article outlines our implementation of key parts of the augmented reality application using the OpenCV library

Hijacking the Linux Kernel

In this paper, a new method of hijacking the Linux kernel is presented. It is based on analysing the Linux system call handler, where a proper set of instructions is subsequently replaced by a jump to a different function. The ability to change the execution flow in the middle of an existing function represents a unique approach in Linux kernel hacking. The attack is applicable to all kernels from the 2.6 series on the Intel architecture. Due to this, rootkits based on this kind of technique represent a high risk for Linux administrators

W-symmetry, topological vertex and afline Yangian

We discuss the representation theory of the non-linear chiral algebra W1+infinity, of Gaberdiel and Gopakumar and its connection to the Yangian of whose presentation was given by Tsymbaliuk. The characters of completely degenerate representations of W1+infinity are given by the topological vertex. The Yangian picture provides an infinite number of commuting charges which can be explicitly diagonalized in W1+infinity highest weight representations. Many properties that are difficult to study in the W1+infinity picture turn out to have a simple combinatorial interpretation, once translated to the Yangian picture

Design of adaptive constellations and error protection coding for wireless network coding in 5-node butterfly networks

Abstract In this paper, we focus on the design of a reliable communication scheme for generic 5-node wireless butterfly networks (WBN). Since the WBN represents a natural extension of the basic two-way relay communication channel, we follow the paradigm of Wireless Physical Layer Network Coding and we show that the design of novel adaptive constellations is desirable to exploit the promising performance of wireless network coding in WBN. We introduce a systematic constellation design algorithm, and we show that the proposed constellations are capable of outperforming conventional point-to-point modulations in WBN over the whole range of channel signal to noise ratios. To further support the applicability of the proposed constellations in a practical system, we integrate a simple binary channel coding scheme, providing a robust adaptive modulation and coding scheme for relaying in symmetric WBNs with arbitrary channel conditions

Real-Time Java in Space: Potential Benefits and Open Challenges

In this paper we analyze potential benefits of using the Java programming language in spacecraft on-board applications as well as problems with current Real-Time Java implementations that would have to be solved to make this possible. We base our experience on porting the Ovm Real-Time Java Virtual Machine to RTEMS/LEON2 and also our findings in the Real-Time Java Assessment Project funded by ESA