5,039 research outputs found
Effective algorithm of analysis of integrability via the Ziglin's method
In this paper we continue the description of the possibilities to use
numerical simulations for mathematically rigorous computer assisted analysis of
integrability of dynamical systems. We sketch some of the algebraic methods of
studying the integrability and present a constructive algorithm issued from the
Ziglin's approach. We provide some examples of successful applications of the
constructed algorithm to physical systems.Comment: a figure added, version accepted to JDC
Simplicial complexes and complex systems
© 2018 European Physical Society. We provide a short introduction to the field of topological data analysis (TDA) and discuss its possible relevance for the study of complex systems. TDA provides a set of tools to characterise the shape of data, in terms of the presence of holes or cavities between the points. The methods, based on the notion of simplicial complexes, generalise standard network tools by naturally allowing for many-body interactions and providing results robust under continuous deformations of the data. We present strengths and weaknesses of current methods, as well as a range of empirical studies relevant to the field of complex systems, before identifying future methodological challenges to help understand the emergence of collective phenomena
Fixed-point realization of fast nonlinear Fourier transform algorithm for FPGA implementation of optical data processing
The nonlinear Fourier transform (NFT) based signal processing has attracted considerable attention as a promising tool for fibre nonlinearity mitigation in optical transmission. However, the mathematical complexity of NFT algorithms and the noticeable distinction of the latter from the “conventional” (Fourier-based) methods make it difficult to adapt this approach for practical applications. In our work, we demonstrate a hardware implementation of the fast direct NFT operation: it is used to map the optical signal onto its nonlinear Fourier spectrum, i.e. to demodulate the data. The main component of the algorithm is the matrix-multiplier unit, implemented on field-programmable gate arrays (FPGA) and used in our study for the estimation of required hardware resources. To design the best performing implementation in limited resources, we carry out the processing accuracy analysis to estimate the optimal bit width. The fast NFT algorithm that we analyse, is based on the FFT, which leads to the O(N log^{2}_{2} N) method’s complexity for the signal consisting of N samples. Our analysis revealed the significant demand in DSP blocks on the used board, which is caused by the complex-valued matrix operations and FFTs. Nevertheless, it seems to be possible to utilise further the parallelisation of our NFT-processing implementation for the more efficient NFT hardware realisation
Light-shining-through-wall cavity setups for probing ALPs
We discuss the aspects of axion-like-particles (ALPs) searches with
Light-Shining-through-Wall (LSW) experimental setups consisted of two
radio-frequency cavities. We compare the efficiencies of three setups which
involve the cavity pump modes and external magnetic fields. Additionally, we
discuss the sensitivity dependence both on the relative position of two
cylindrical cavities and on their radius-to-length ratio.Comment: 9 pages, 6 figures, 1 table. Revised version, accepted to JETP
Letter
Harmonic oscillators in the Nos\'e - Hoover thermostat
We study the dynamics of an ensemble of non-interacting harmonic oscillators
in a nonlinear dissipative environment described by the Nos\'e - Hoover model.
Using numerical simulation we find the histogram for total energy, which agrees
with the analysis of the Nos\'e - Hoover equations effected with the method of
averaging. The histogram does not correspond to Gibbs' canonical distribution.
We have found oscillations at frequency proportional to ,
the dissipative parameter of thermostat and the characteristic
mass of particle, about the stationary state corresponding to equilibrium. The
oscillations could have an important bearing upon the analysis of simulating
molecular dynamics in the Nos\'e - Hoover thermostat.Comment: 7 pages, 4 figure
Developing and Deploying a Taxi Price Comparison Mobile App in the Wild: Insights and Challenges.
As modern transportation systems become more complex, there is need for
mobile applications that allow travelers to navigate efficiently in cities. In
taxi transport the recent proliferation of Uber has introduced new norms
including a flexible pricing scheme where journey costs can change rapidly
depending on passenger demand and driver supply. To make informed choices on
the most appropriate provider for their journeys, travelers need access to
knowledge about provider pricing in real time. To this end, we developed
OpenStreetcab a mobile application that offers advice on taxi transport
comparing provider prices. We describe its development and deployment in two
cities, London and New York, and analyse thousands of user journey queries to
compare the price patterns of Uber against major local taxi providers. We have
observed large heterogeneity across the taxi transport markets in the two
cities. This motivated us to perform a price validation and measurement
experiment on the ground comparing Uber and Black Cabs in London. The
experimental results reveal interesting insights: not only they confirm
feedback on pricing and service quality received by professional drivers users,
but also they reveal the tradeoffs between prices and journey times between
taxi providers. With respect to journey times in particular, we show how
experienced taxi drivers, in the majority of the cases, are able to navigate
faster to a destination compared to drivers who rely on modern navigation
systems. We provide evidence that this advantage becomes stronger in the centre
of a city where urban density is high
Energy loss for heavy quarks in relation to light partons; is radiative energy loss for heavy quarks anomalous?
The scaling properties of jet suppression measurements are compared for
non-photonic electrons () and neutral pions () in Au + Au
collisions at GeV. For a broad range of transverse momenta
and collision centralities, the comparison is consistent with jet quenching
dominated by radiative energy loss for both heavy and light partons. Less
quenching is indicated for heavy quarks via ; this gives an
independent estimate of the transport coefficient that agrees with
its magnitude obtained from quenching of light partons via 's.Comment: Published versio
The BaBar Event Building and Level-3 Trigger Farm Upgrade
The BaBar experiment is the particle detector at the PEP-II B-factory
facility at the Stanford Linear Accelerator Center. During the summer shutdown
2002 the BaBar Event Building and Level-3 trigger farm were upgraded from 60
Sun Ultra-5 machines and 100MBit/s Ethernet to 50 Dual-CPU 1.4GHz Pentium-III
systems with Gigabit Ethernet. Combined with an upgrade to Gigabit Ethernet on
the source side and a major feature extraction software speedup, this pushes
the performance of the BaBar event builder and L3 filter to 5.5kHz at current
background levels, almost three times the original design rate of 2kHz. For our
specific application the new farm provides 8.5 times the CPU power of the old
system.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, 1 eps figure, PSN MOGT00
- …