9,496 research outputs found
Information transfer through a one-atom micromaser
We consider a realistic model for the one-atom micromaser consisting of a
cavity maintained in a steady state by the streaming of two-level Rydberg atoms
passing one at a time through it. We show that it is possible to monitor the
robust entanglement generated between two successive experimental atoms passing
through the cavity by the control decoherence parameters. We calculate the
entanglement of formation of the joint two-atom state as a function of the
micromaser pump parameter. We find that this is in direct correspondence with
the difference of the Shannon entropy of the cavity photons before and after
the passage of the atoms for a reasonable range of dissipation parameters. It
is thus possible to demonstrate information transfer between the cavity and the
atoms through this set-up.Comment: Revtex, 5 pages, 2 encapsulated ps figures; added discussion on
information transfer in relation with cavity photon statistics; typos
corrected; Accepted for Publicaiton in Europhysics Letter
Mapping topography and broad vegetation type to characterise the Boxford meadows SSSI (Unit 2)
Understanding the dynamic relationship between hydrology and ecology in a complex wetland setting should be considered integral to the sustainable management and conservation of wetland habitats and future water resource planning. Wetland hydrology can exhibit considerable spatial complexity as a result of sub surface and surface heterogeneity. The latter of which may be determined by the relationship between spatial topography variation and broad vegetation distribution. Any study to investigate such a relationship must be at a spatial resolution sufficient to identify patterns in surface topography and vegetation type.
In this study state of the art survey technology was used to collect and record for subsequent mapping the topographic and vegetation characteristics of the Boxford lowland chalk groundwater dependent terrestrial ecosystem (GDTE). The resultant survey dataset successfully unveiled distinct patterns in topography and vegetation type. The analysis of the data in a Geographical Information System (GIS) desk confirmed for the first time the presence of paleo-channels and a braided fluvial system within the meadows. In addition the combined survey method gives some indication that the type of vegetation present appears to coincide with some of the more distinctive topographical features.
The results demonstrate that combining the field survey campaign alongside desk based GIS analysis is an extremely useful and versatile tool and can provide valuable information to support the decision making process for both further scientific investigation and sustainable habitat management
Clustered bottlenecks in mRNA translation and protein synthesis
We construct an algorithm that generates large, band-diagonal transition
matrices for a totally asymmetric exclusion process (TASEP) with local hopping
rate inhomogeneities. The matrices are diagonalized numerically to find
steady-state currents of TASEPs with local variations in hopping rate. The
results are then used to investigate clustering of slow codons along mRNA.
Ribosome density profiles near neighboring clusters of slow codons interact,
enhancing suppression of ribosome throughput when such bottlenecks are closely
spaced. Increasing the slow codon cluster size, beyond , does not
significantly reduce ribosome current. Our results are verified by extensive
Monte-Carlo simulations and provide a biologically-motivated explanation for
the experimentally-observed clustering of low-usage codons
QCD at finite chemical potential with six time slices
We investigate the Taylor expansion of the baryon number susceptibility, and
hence, pressure, in a series in the baryon chemical potential (mu_B) through a
lattice simulation with light dynamical staggered quarks at a finer lattice
cutoff a=1/6T. We determine the QCD cross over coupling at mu_B=0. We find the
radius of convergence of the series at various temeperatures, and bound the
location of the QCD critical point to be T^E/T_c = 0.94 and mu_B^E/T < 1.8. We
also investigate the extrapolation of various susceptibilities and linkages to
finite chemical potential.Comment: 16 pages, 12 figure
Testing the self-duality of topological lumps in SU(3) lattice gauge theory
We discuss a simple formula which connects the field-strength tensor to a
spectral sum over certain quadratic forms of the eigenvectors of the lattice
Dirac operator. We analyze these terms for the near zero-modes and find that
they give rise to contributions which are essentially either self-dual or anti
self-dual. Modes with larger eigenvalues in the bulk of the spectrum are more
dominated by quantum fluctuations and are less (anti) self-dual. In the high
temperature phase of QCD we find considerably reduced (anti) self-duality for
the modes near the edge of the spectral gap.Comment: Remarks added, to appear in Phys. Rev. Let
Entanglement in a two-identical-particle system
The definition of entanglement in identical-particle system is introduced.
The separability criterion in two-identical particle system is given. The
physical meaning of the definition is analysed. Applications to two-boson and
two-fermion systems are made. It is found new entanglement and correlation
phenomena in identical-boson systems exist, and they may have applications in
the field of quantum information.Comment: 4 page
Chiral symmetry restoration and the Z3 sectors of QCD
Quenched SU(3) lattice gauge theory shows three phase transitions, namely the
chiral, the deconfinement and the Z3 phase transition. Knowing whether or not
the chiral and the deconfinement phase transition occur at the same temperature
for all Z3 sectors could be crucial to understand the underlying microscopic
dynamics. We use the existence of a gap in the Dirac spectrum as an order
parameter for the restoration of chiral symmetry. We find that the spectral gap
opens up at the same critical temperature in all Z3 sectors in contrast to
earlier claims in the literature.Comment: 4 pages, 4 figure
Electronic Structure of Atoms in Magnetic Quadrupole Traps
We investigate the electronic structure and properties of atoms exposed to a
magnetic quadrupole field. The spin-spatial as well as generalized time
reversal symmetries are established and shown to lead to a two-fold degeneracy
of the electronic states in the presence of the field. Low-lying as well as
highly excited Rydberg states are computed and analyzed for a broad regime of
field gradients. The delicate interplay between the Coulomb and various
magnetic interactions leads to complex patterns of the spatial spin
polarization of individual excited states. Electromagnetic transitions in the
quadrupole field are studied in detail thereby providing the selection rules
and in particular the transition wavelengths and corresponding dipole
strengths. The peculiar property that the quadrupole magnetic field induces
permanent electric dipole moments of the atoms is derived and discussed.Comment: 17 pages, 13 figures, accepted for publication in PR
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