582 research outputs found
Discrete Accidental Symmetry for a Particle in a Constant Magnetic Field on a Torus
A classical particle in a constant magnetic field undergoes cyclotron motion
on a circular orbit. At the quantum level, the fact that all classical orbits
are closed gives rise to degeneracies in the spectrum. It is well-known that
the spectrum of a charged particle in a constant magnetic field consists of
infinitely degenerate Landau levels. Just as for the and
potentials, one thus expects some hidden accidental symmetry, in this case with
infinite-dimensional representations. Indeed, the position of the center of the
cyclotron circle plays the role of a Runge-Lenz vector. After identifying the
corresponding accidental symmetry algebra, we re-analyze the system in a finite
periodic volume. Interestingly, similar to the quantum mechanical breaking of
CP invariance due to the -vacuum angle in non-Abelian gauge theories,
quantum effects due to two self-adjoint extension parameters and
explicitly break the continuous translation invariance of the
classical theory. This reduces the symmetry to a discrete magnetic translation
group and leads to finite degeneracy. Similar to a particle moving on a cone, a
particle in a constant magnetic field shows a very peculiar realization of
accidental symmetry in quantum mechanics.Comment: 25 pages, 2 figure
An SBVR Framework for RESTful Web Applications
We propose a framework that can be used to produce functioning web applications from SBVR models. To achieve this, we begin by discussing the concept of declarative application generation and examining the commonalities between SBVR and the RESTful architectural style of the web. We then show how a relational database schema and RESTful interface can be generated from an SBVR model. In this context, we discuss how SBVR can be used to semantically describe hypermedia on the Web and enhance its evolvability and loose coupling properties. Finally, we show that this system is capable of exhibiting process-like behaviour without requiring explicitly defined processes
Scaling anomaly in cosmic string background
We show that the classical scale symmetry of a particle moving in cosmic
string background is broken upon inequivalent quantization of the classical
system, leading to anomaly. The consequence of this anomaly is the formation of
single bound state in the coupling interval \gamma\in(-1,1). The inequivalent
quantization is characterized by a 1-parameter family of self-adjoint extension
parameter \omega. It has been conjectured that the formation of loosely bound
state in cosmic string background may lead to the so called anomalous
scattering cross section for the particles, which is usually seen in molecular
physics.Comment: 4 pages,1 figur
Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight
The first flight of the Antarctic Impulsive Transient Antenna (ANITA)
experiment recorded 16 radio signals that were emitted by cosmic-ray induced
air showers. For 14 of these events, this radiation was reflected from the ice.
The dominant contribution to the radiation from the deflection of positrons and
electrons in the geomagnetic field, which is beamed in the direction of motion
of the air shower. This radiation is reflected from the ice and subsequently
detected by the ANITA experiment at a flight altitude of 36km. In this paper,
we estimate the energy of the 14 individual events and find that the mean
energy of the cosmic-ray sample is 2.9 EeV. By simulating the ANITA flight, we
calculate its exposure for ultra-high energy cosmic rays. We estimate for the
first time the cosmic-ray flux derived only from radio observations. In
addition, we find that the Monte Carlo simulation of the ANITA data set is in
agreement with the total number of observed events and with the properties of
those events.Comment: Added more explanation of the experimental setup and textual
improvement
Loop Quantum Gravity: An Inside View
This is a (relatively) non -- technical summary of the status of the quantum
dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical
evolution of the subject and why the results obtained so far are non --
trivial. The present text can be viewed in part as a response to an article by
Nicolai, Peeters and Zamaklar [hep-th/0501114]. We also explain why certain no
go conclusions drawn from a mathematically correct calculation in a recent
paper by Helling et al [hep-th/0409182] are physically incorrect.Comment: 58 pages, no figure
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
Capturing the heterogeneity of sub-national production in global trade flows
With increasingly complex and globalised supply chains, agricultural production and related impacts are often far removed from the point of final demand and difficult to trace. Accurately linking consumption to production is essential to understand drivers, key actors, and to facilitate actionable adaptation strategies to minimise negative impacts and guarantee food security. Here a hybridised multiregional input-output (MRIO) model, IOTA, is introduced. IOTA utilises sub-national and national level production, trade and environmental data, national scale commodity-use data, and a global economic MRIO, to link sub-national production and associated impacts to regional final consumption. In an example case-study, applying the model to Brazilian soy production and related land use for EU consumption, the relative levels of production in Brazilian states to meet EU demand differ from those of total production, and differ further still between the EU's constituent countries. Patterns can also vary considerably within a country's consumption profile depending on the sector of purchase. The linking of consumption to sub-national production and trade allows for more accurate and meaningful connections to be made between consumer behaviour and the associated impacts and risks. This enhanced understanding of consumption-driven impacts in turn informs, and allows for, more targeted and effective policy interventions to tackle the pressures and risks associated with agricultural commodity production for a global market
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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