526 research outputs found
On U_q(SU(2))-symmetric Driven Diffusion
We study analytically a model where particles with a hard-core repulsion
diffuse on a finite one-dimensional lattice with space-dependent, asymmetric
hopping rates. The system dynamics are given by the
\mbox{U[SU(2)]}-symmetric Hamiltonian of a generalized anisotropic
Heisenberg antiferromagnet. Exploiting this symmetry we derive exact
expressions for various correlation functions. We discuss the density profile
and the two-point function and compute the correlation length as well
as the correlation time . The dynamics of the density and the
correlations are shown to be governed by the energy gaps of a one-particle
system. For large systems and depend only on the asymmetry. For
small asymmetry one finds indicating a dynamical exponent
as for symmetric diffusion.Comment: 10 pages, LATE
Will jams get worse when slow cars move over?
Motivated by an analogy with traffic, we simulate two species of particles
(`vehicles'), moving stochastically in opposite directions on a two-lane ring
road. Each species prefers one lane over the other, controlled by a parameter
such that corresponds to random lane choice and
to perfect `laning'. We find that the system displays one large cluster (`jam')
whose size increases with , contrary to intuition. Even more remarkably, the
lane `charge' (a measure for the number of particles in their preferred lane)
exhibits a region of negative response: even though vehicles experience a
stronger preference for the `right' lane, more of them find themselves in the
`wrong' one! For very close to 1, a sharp transition restores a homogeneous
state. Various characteristics of the system are computed analytically, in good
agreement with simulation data.Comment: 7 pages, 3 figures; to appear in Europhysics Letters (2005
Density Profile of the One-Dimensional Partially Asymmetric Simple Exclusion Process with Open Boundaries
The one-dimensional partially asymmetric simple exclusion process with open
boundaries is considered. The stationary state, which is known to be
constructed in a matrix product form, is studied by applying the theory of
q-orthogonal polynomials. Using a formula of the q-Hermite polynomials, the
average density profile is computed in the thermodynamic limit. The phase
diagram for the correlation length, which was conjectured in the previous
work[J. Phys. A {\bf 32} (1999) 7109], is confirmed.Comment: 24 pages, 6 figure
Exact Solution of Two-Species Ballistic Annihilation with General Pair-Reaction Probability
The reaction process is modelled for ballistic reactants on an
infinite line with particle velocities and and initially
segregated conditions, i.e. all A particles to the left and all B particles to
the right of the origin. Previous, models of ballistic annihilation have
particles that always react on contact, i.e. pair-reaction probability .
The evolution of such systems are wholly determined by the initial distribution
of particles and therefore do not have a stochastic dynamics. However, in this
paper the generalisation is made to , allowing particles to pass through
each other without necessarily reacting. In this way, the A and B particle
domains overlap to form a fluctuating, finite-sized reaction zone where the
product C is created. Fluctuations are also included in the currents of A and B
particles entering the overlap region, thereby inducing a stochastic motion of
the reaction zone as a whole. These two types of fluctuations, in the reactions
and particle currents, are characterised by the `intrinsic reaction rate', seen
in a single system, and the `extrinsic reaction rate', seen in an average over
many systems. The intrinsic and extrinsic behaviours are examined and compared
to the case of isotropically diffusing reactants.Comment: 22 pages, 2 figures, typos correcte
1981 Plant viruses
1, Clover viruses - 81HA6, 81MA9, 81BR14, 81BY12, 81BH5, 81AL38, 81ES39 OBJECTIVES: To determine the extent of the \u27Dinninup virus\u27 problem (sub. clover mottle). To further assess the incidence of red leaf virus to determine the incidence of bean yellow mosaic virus. To note the incidence of sub. clover stunt virus. A. BYDV: Survey of incidence - 81BU1, 81BU2, 81BR11, 81BR12, 81MA6, 81MA7, 81AL31, 81AL32, 81JE14, 81JE15, 81KA21, 81KA22, 81NA28, 81N031, 81ES38, 81E26. 2. Barley yellow dwarf virus. BYDV: Genotype x insecticide studies - 81MN14, 81MT29, 81E28, 81MN14. BYDV: differences amongst barley genotypes - 81C19, 81WH31, 81BA30. BYDV: Resistance and yield in CV.Shannon and CV. Proctor - 871BR13, 81MA8, 81AL36, 81JE17 Yield per plot and 100 seed weight - Albany 81AL36 Infection of BYDV in cereal genotypes at Manjimup ( 81MN13)
Spurious phase in a model for traffic on a bridge
We present high-precision Monte Carlo data for the phase diagram of a
two-species driven diffusive system, reminiscent of traffic across a narrow
bridge. Earlier studies reported two phases with broken symmetry; the existence
of one of these has been the subject of some debate. We show that the disputed
phase disappears for sufficiently large systems and/or sufficiently low bulk
mobility.Comment: 8 pages, 3 figures, JPA styl
Status of a DEPFET pixel system for the ILC vertex detector
We have developed a prototype system for the ILC vertex detector based on
DEPFET pixels. The system operates a 128x64 matrix (with ~35x25 square micron
large pixels) and uses two dedicated microchips, the SWITCHER II chip for
matrix steering and the CURO II chip for readout. The system development has
been driven by the final ILC requirements which above all demand a detector
thinned to 50 micron and a row wise read out with line rates of 20MHz and more.
The targeted noise performance for the DEPFET technology is in the range of
ENC=100 e-. The functionality of the system has been demonstrated using
different radioactive sources in an energy range from 6 to 40keV. In recent
test beam experiments using 6GeV electrons, a signal-to-noise ratio of S/N~120
has been achieved with present sensors being 450 micron thick. For improved
DEPFET systems using 50 micron thin sensors in future, a signal-to-noise of 40
is expected.Comment: Invited poster at the International Symposium on the Development of
Detectors for Particle, AstroParticle and Synchrotron Radiation Experiments,
Stanford CA (SNIC06) 6 pages, 12 eps figure
Electronic correlation effects and the Coulomb gap at finite temperature
We have investigated the effect of the long-range Coulomb interaction on the
one-particle excitation spectrum of n-type Germanium, using tunneling
spectroscopy on mechanically controllable break junctions. The tunnel
conductance was measured as a function of energy and temperature. At low
temperatures, the spectra reveal a minimum at zero bias voltage due to the
Coulomb gap. In the temperature range above 1 K the Coulomb gap is filled by
thermal excitations. This behavior is reflected in the temperature dependence
of the variable-range hopping resitivity measured on the same samples: Up to a
few degrees Kelvin the Efros-Shkovskii ln law is obeyed,
whereas at higher temperatures deviations from this law are observed,
indicating a cross-over to Mott's ln law. The mechanism of
this cross-over is different from that considered previously in the literature.Comment: 3 pages, 3 figure
Applying psychological type theory to cathedral visitors : a case study of two cathedrals in England and Wales
This study employs Jungian psychological type theory to profile visitors to Chester Cathedral in England and St Davids Cathedral in Wales. Psychological type theory offers a fourfold psychographic segmentation of visitors, distinguishing between introversion and extraversion, sensing and intuition, thinking and feeling, and judging and perceiving. New data provided by 157 visitors to Chester Cathedral (considered alongside previously published data provided by 381 visitors to St Davids Cathedral) demonstrated that these two cathedrals attract more introverts than extraverts, more sensers than intuitives, and more judgers than perceivers, but equal proportions of thinkers and feelers. Comparison with the population norms demonstrated that extraverts and perceivers are significantly under-represented among visitors to these two cathedrals. The implications of these findings are discussed both for maximising the visitor experiences of those already attracted to these cathedrals and for discovering ways of attracting more extraverts and more perceivers to explore these cathedrals
Diffusion-Annihilation in the Presence of a Driving Field
We study the effect of an external driving force on a simple stochastic
reaction-diffusion system in one dimension. In our model each lattice site may
be occupied by at most one particle. These particles hop with rates
to the right and left nearest neighbouring site resp. if this
site is vacant and annihilate with rate 1 if it is occupied. We show that
density fluctuations (i.e. the moments of the
density distribution at time ) do not depend on the spatial anisotropy
induced by the driving field, irrespective of the initial condition.
Furthermore we show that if one takes certain translationally invariant
averages over initial states (e.g. random initial conditions) even local
fluctuations do not depend on . In the scaling regime the
effect of the driving can be completely absorbed in a Galilei transformation
(for any initial condition). We compute the probability of finding a system of
sites in its stationary state at time if it was fully occupied at time
.Comment: 17 pages, latex, no figure
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