Lattice Gauge Tensor Networks

We present a unified framework to describe lattice gauge theories by means of tensor networks: this framework is efficient as it exploits the high amount of local symmetry content native of these systems describing only the gauge invariant subspace. Compared to a standard tensor network description, the gauge invariant one allows to speed-up real and imaginary time evolution of a factor that is up to the square of the dimension of the link variable. The gauge invariant tensor network description is based on the quantum link formulation, a compact and intuitive formulation for gauge theories on the lattice, and it is alternative to and can be combined with the global symmetric tensor network description. We present some paradigmatic examples that show how this architecture might be used to describe the physics of condensed matter and high-energy physics systems. Finally, we present a cellular automata analysis which estimates the gauge invariant Hilbert space dimension as a function of the number of lattice sites and that might guide the search for effective simplified models of complex theories.Comment: 28 pages, 9 figure

From M-ary Query to Bit Query: a new strategy for efficient large-scale RFID identification

The tag collision avoidance has been viewed as one of the most important research problems in RFID communications and bit tracking technology has been widely embedded in query tree (QT) based algorithms to tackle such challenge. Existing solutions show further opportunity to greatly improve the reading performance because collision queries and empty queries are not fully explored. In this paper, a bit query (BQ) strategy based Mary query tree protocol (BQMT) is presented, which can not only eliminate idle queries but also separate collided tags into many small subsets and make full use of the collided bits. To further optimize the reading performance, a modified dual prefixes matching (MDPM) mechanism is presented to allow multiple tags to respond in the same slot and thus significantly reduce the number of queries. Theoretical analysis and simulations are supplemented to validate the effectiveness of the proposed BQMT and MDPM, which outperform the existing QT-based algorithms. Also, the BQMT and MDPM can be combined to BQMDPM to improve the reading performance in system efficiency, total identification time, communication complexity and average energy cost

PALPAS - PAsswordLess PAssword Synchronization

Tools that synchronize passwords over several user devices typically store the encrypted passwords in a central online database. For encryption, a low-entropy, password-based key is used. Such a database may be subject to unauthorized access which can lead to the disclosure of all passwords by an offline brute-force attack. In this paper, we present PALPAS, a secure and user-friendly tool that synchronizes passwords between user devices without storing information about them centrally. The idea of PALPAS is to generate a password from a high entropy secret shared by all devices and a random salt value for each service. Only the salt values are stored on a server but not the secret. The salt enables the user devices to generate the same password but is statistically independent of the password. In order for PALPAS to generate passwords according to different password policies, we also present a mechanism that automatically retrieves and processes the password requirements of services. PALPAS users need to only memorize a single password and the setup of PALPAS on a further device demands only a one-time transfer of few static data.Comment: An extended abstract of this work appears in the proceedings of ARES 201

Impact of Wind Generators in Power System Stability

Wind electricity is one of the quickest developing renewable resources of power. This rapid development is expected considering the environmental factors, but in terms of power system stability, it comes with a number of concerns. Generators play a vital role on stability for a particular capacity and design of a network. This paper investigated the overall performance of 3 foremost types of wind turbines via small signal stability analysis on IEEE 9 bus system. Simulations have been done and established that the generators dynamic model have significant impact on power system stability at different capacity of the generators

Lie Markov models with purine/pyrimidine symmetry

Continuous-time Markov chains are a standard tool in phylogenetic inference. If homogeneity is assumed, the chain is formulated by specifying time-independent rates of substitutions between states in the chain. In applications, there are usually extra constraints on the rates, depending on the situation. If a model is formulated in this way, it is possible to generalise it and allow for an inhomogeneous process, with time-dependent rates satisfying the same constraints. It is then useful to require that there exists a homogeneous average of this inhomogeneous process within the same model. This leads to the definition of "Lie Markov models", which are precisely the class of models where such an average exists. These models form Lie algebras and hence concepts from Lie group theory are central to their derivation. In this paper, we concentrate on applications to phylogenetics and nucleotide evolution, and derive the complete hierarchy of Lie Markov models that respect the grouping of nucleotides into purines and pyrimidines -- that is, models with purine/pyrimidine symmetry. We also discuss how to handle the subtleties of applying Lie group methods, most naturally defined over the complex field, to the stochastic case of a Markov process, where parameter values are restricted to be real and positive. In particular, we explore the geometric embedding of the cone of stochastic rate matrices within the ambient space of the associated complex Lie algebra. The whole list of Lie Markov models with purine/pyrimidine symmetry is available at http://www.pagines.ma1.upc.edu/~jfernandez/LMNR.pdf.Comment: 32 page

Kesan pembelajaran koperatif terhadap pencapaian Matematik dan sikap terhadap pembelajaran Matematik bagi murid berkebolehan rendah di sekolah rendah bahagian Bintulu

The purpose of this research was to identify the effectiveness of using cooperative learning method towards students' achievement and attitude in learning Mathematics for low achiever primary school in Bintulu. In particular this study seeks to determine whether the low achiever can increase their achievement and attitude in learning Mathematics using the cooperative learning method. This study was a quasi-experimental, the experimental group received teaching method using cooperative learning method, while the control group received traditional lecture method. This study was conducted in a primary school in Sarawak for eight weeks. Two of the Year Five classes have participated in this study, one class for experimental group and another class for control group. A total of 79 respondents have participated, there were 39 students in experimental group (cooperative learning method) and 40 students in control group (traditional lecture method). There were pre-achievement test, post-achievement test, pre-attitude test and post-attitude test used to collect data in this study. The questions of achievement test were based on objective and subjective questions and the attitude test was based on questionnaires. Research findings analyzed using Statistical Package for Social Science (SPSS) version 12.0. Package was chosen because it is more flexible, the researchers can create various transformations of original data in addition to the advantages that statistical procedures can be used measurement variables are Likert Scale according to 4 degrees. Data were collected and analyzed by using descriptive statistics frequency percentages, mean and standard deviation. In addition, Independent-Sample T test also used to see whether there is a significant difference between the students' achievement and attitude with the cooperative learning method. The findings showed that cooperative learning method could enhance the low achiever achievement and attitude in learning Mathematics. In addition, cooperative learning method had shown the positive effects toward the performance of cognitive, social and affective for low achiever students in primary schoo