14,098 research outputs found
Noise-Induced Transition from Translational to Rotational Motion of Swarms
We consider a model of active Brownian agents interacting via a harmonic
attractive potential in a two-dimensional system in the presence of noise. By
numerical simulations, we show that this model possesses a noise-induced
transition characterized by the breakdown of translational motion and the onset
of swarm rotation as the noise intensity is increased. Statistical properties
of swarm dynamics in the weak noise limit are further analytically
investigated.Comment: 7 pages, 7 figure
A Development Environment for Visual Physics Analysis
The Visual Physics Analysis (VISPA) project integrates different aspects of
physics analyses into a graphical development environment. It addresses the
typical development cycle of (re-)designing, executing and verifying an
analysis. The project provides an extendable plug-in mechanism and includes
plug-ins for designing the analysis flow, for running the analysis on batch
systems, and for browsing the data content. The corresponding plug-ins are
based on an object-oriented toolkit for modular data analysis. We introduce the
main concepts of the project, describe the technical realization and
demonstrate the functionality in example applications
Automated Reconstruction of Particle Cascades in High Energy Physics Experiments
We present a procedure for reconstructing particle cascades from event data
measured in a high energy physics experiment. For evaluating the hypothesis of
a specific physics process causing the observed data, all possible
reconstruction versions of the scattering process are constructed from the
final state objects. We describe the procedure as well as examples of physics
processes of different complexity studied at hadron-hadron colliders. We
estimate the performance by 20 microseconds per reconstructed decay vertex, and
0.6 kByte per reconstructed particle in the decay trees.Comment: 8 pages, 2 figures. Submitted to Computational Science & Discover
The Midpoint Rule as a Variational--Symplectic Integrator. I. Hamiltonian Systems
Numerical algorithms based on variational and symplectic integrators exhibit
special features that make them promising candidates for application to general
relativity and other constrained Hamiltonian systems. This paper lays part of
the foundation for such applications. The midpoint rule for Hamilton's
equations is examined from the perspectives of variational and symplectic
integrators. It is shown that the midpoint rule preserves the symplectic form,
conserves Noether charges, and exhibits excellent long--term energy behavior.
The energy behavior is explained by the result, shown here, that the midpoint
rule exactly conserves a phase space function that is close to the Hamiltonian.
The presentation includes several examples.Comment: 11 pages, 8 figures, REVTe
Concepts, Developments and Advanced Applications of the PAX Toolkit
The Physics Analysis eXpert (PAX) is an open source toolkit for high energy
physics analysis. The C++ class collection provided by PAX is deployed in a
number of analyses with complex event topologies at Tevatron and LHC. In this
article, we summarize basic concepts and class structure of the PAX kernel. We
report about the most recent developments of the kernel and introduce two new
PAX accessories. The PaxFactory, that provides a class collection to facilitate
event hypothesis evolution, and VisualPax, a Graphical User Interface for PAX
objects
Subspace hypercyclicity
A bounded linear operator T on Hilbert space is subspace-hypercyclic for a
subspace M if there exists a vector whose orbit under T intersects the subspace
in a relatively dense set. We construct examples to show that
subspace-hypercyclicity is interesting, including a nontrivial
subspace-hypercyclic operator that is not hypercyclic. There is a Kitai-like
criterion that implies subspace-hypercyclicity and although the spectrum of a
subspace-hypercyclic operator must intersect the unit circle, not every
component of the spectrum will do so. We show that, like hypercyclicity,
subspace-hypercyclicity is a strictly infinite-dimensional phenomenon.
Additionally, compact or hyponormal operators can never be
subspace-hypercyclic.Comment: 15 page
Generation of Pure-State Single-Photon Wavepackets by Conditional Preparation Based on Spontaneous Parametric Downconversion
We study the conditional preparation of single photons based on parametric
downconversion, where the detection of one photon from a given pair heralds the
existence of a single photon in the conjugate mode. We derive conditions on the
modal characteristics of the photon pairs, which ensure that the conditionally
prepared single photons are quantum-mechanically pure. We propose specific
experimental techniques that yield photon pairs ideally suited for
single-photon conditional preparation.Comment: 14 pages, 6 figure
Generation of two-photon states with arbitrary degree of entanglement via nonlinear crystal superlattices
We demonstrate a general method of engineering the joint quantum state of
photon pairs produced in spontaneous parametric downconversion (PDC). The
method makes use of a superlattice structure of nonlinear and linear materials,
in conjunction with a broadband pump, to manipulate the group delays of the
signal and idler photons relative to the pump pulse, and realizes a joint
spectral amplitude with arbitrary degree of entanglement for the generated
pairs. This method of group delay engineering has the potential of synthesizing
a broad range of states including factorizable states crucial for quantum
networking and states optimized for Hong-Ou-Mandel interferometry. Experimental
results for the latter case are presented, illustrating the principles of this
approach.Comment: 4 pages, 4 figures, accepted Phys. Rev. Let
- …