2,142 research outputs found
Evidence of in-play insider trading on a UK betting exchange
International audienceAn open question in market microstructure is whether 'informed' traders have an advantage due to access to private, inside, information; or due to a superior ability to process public information. In this paper we attempt to answer this question with data from a sports betting exchange taken during play. Uniquely, this allows us to time-stamp information events to the nearest second, and to ensure we are observing all relevant information regarding the value of an asset. We find evidence of inside information but not of a superior ability to process public information. The first finding suggests that a subset of the betting population are observing the action before the wider public (possibly due to delays in the television signal), and betting using this informational advantage
Energies of knot diagrams
We introduce and begin the study of new knot energies defined on knot
diagrams. Physically, they model the internal energy of thin metallic solid
tori squeezed between two parallel planes. Thus the knots considered can
perform the second and third Reidemeister moves, but not the first one. The
energy functionals considered are the sum of two terms, the uniformization term
(which tends to make the curvature of the knot uniform) and the resistance term
(which, in particular, forbids crossing changes). We define an infinite family
of uniformization functionals, depending on an arbitrary smooth function
and study the simplest nontrivial case , obtaining neat normal forms
(corresponding to minima of the functional) by making use of the Gauss
representation of immersed curves, of the phase space of the pendulum, and of
elliptic functions
Three-body recombination in a three-state Fermi gas with widely tunable interactions
We investigate the stability of a three spin state mixture of ultracold
fermionic Li atoms over a range of magnetic fields encompassing three
Feshbach resonances. For most field values, we attribute decay of the atomic
population to three-body processes involving one atom from each spin state and
find that the three-body loss coefficient varies by over four orders of
magnitude. We observe high stability when at least two of the three scattering
lengths are small, rapid loss near the Feshbach resonances, and two unexpected
resonant loss features. At our highest fields, where all pairwise scattering
lengths are approaching , we measure a three-body loss
coefficient and a trend
toward lower decay rates for higher fields indicating that future studies of
color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be
feasible
Cooling dynamics of ultracold two-species Fermi-Bose mixtures
We compare strategies for evaporative and sympathetic cooling of two-species
Fermi-Bose mixtures in single-color and two-color optical dipole traps. We show
that in the latter case a large heat capacity of the bosonic species can be
maintained during the entire cooling process. This could allow to efficiently
achieve a deep Fermi degeneracy regime having at the same time a significant
thermal fraction for the Bose gas, crucial for a precise thermometry of the
mixture. Two possible signatures of a superfluid phase transition for the Fermi
species are discussed.Comment: 4 pages, 3 figure
Measurement of the Zero Crossing in a Feshbach Resonance of Fermionic 6-Li
We measure a zero crossing in the scattering length of a mixture of the two
lowest hyperfine states of 6-Li. To locate the zero crossing, we monitor the
decrease in temperature and atom number arising from evaporation in a CO2 laser
trap as a function of magnetic field B. The temperature decrease and atom loss
are minimized for B=528(4) G, consistent with no evaporation. We also present
preliminary calculations using potentials that have been constrained by the
measured zero crossing and locate a broad Feshbach resonance at approximately
860 G, in agreement with previous theoretical predictions. In addition, our
theoretical model predicts a second and much narrower Feshbach resonance near
550 G.Comment: Five pages, four figure
Efficient and robust initialization of a qubit register with fermionic atoms
We show that fermionic atoms have crucial advantages over bosonic atoms in
terms of loading in optical lattices for use as a possible quantum computation
device. After analyzing the change in the level structure of a non-uniform
confining potential as a periodic potential is superimposed to it, we show how
this structure combined with the Pauli principle and fermion degeneracy can be
exploited to create unit occupancy of the lattice sites with very high
efficiency.Comment: 4 pages, 3 figure
Auger decay, Spin-exchange, and their connection to Bose-Einstein condensation of excitons in Cu_2O
In view of the recent experiments of O'Hara, et al. on excitons in Cu_2O, we
examine the interconversion between the angular-momentum triplet-state excitons
and the angular-momentum singlet-state excitons by a spin-exchange process
which has been overlooked in the past. We estimate the rate of this
particle-conserving mechanism and find a substantially higher value than the
Auger process considered so far. Based on this idea, we give a possible
explanation of the recent experimental observations, and make certain
predictions, with the most important being that the singlet-state excitons in
Cu_2O is a very serious candidate for exhibiting the phenomenon of
Bose-Einstein condensation.Comment: 4 pages, RevTex, 1 ps figur
Stiff knots
We report on the geometry and mechanics of knotted stiff strings. We discuss
both closed and open knots. Our two main results are: (i) Their equilibrium
energy as well as the equilibrium tension for open knots depend on the type of
knot as the square of the bridge number; (ii) Braid localization is found to be
a general feature of stiff strings entanglements, while angles and knot
localization are forbidden. Moreover, we identify a family of knots for which
the equilibrium shape is a circular braid. Two other equilibrium shapes are
found from Monte Carlo simulations. These three shapes are confirmed by
rudimentary experiments. Our approach is also extended to the problem of the
minimization of the length of a knotted string with a maximum allowed
curvature.Comment: Submitted to Phys. Rev.
Pure Gas of Optically Trapped Molecules Created from Fermionic Atoms
We report on the production of a pure sample of up to 3x10^5 optically
trapped molecules from a Fermi gas of 6Li atoms. The dimers are formed by
three-body recombination near a Feshbach resonance. For purification a
Stern-Gerlach selection technique is used that efficiently removes all trapped
atoms from the atom-molecule mixture. The behavior of the purified molecular
sample shows a striking dependence on the applied magnetic field. For very
weakly bound molecules near the Feshbach resonance, the gas exhibits a
remarkable stability with respect to collisional decay.Comment: 4 pages, 5 figure
Evaluation and decentralised governance: Examples of inspections in polycentric education systems
Across Europe schools and other service providers increasingly operate in networks to provide inclusive education or develop and implement more localized school-to-school improvement models. As some education systems move towards more decentralized decision-making where multiple actors have an active role in steering and governing schools, the tasks and responsibilities of Inspectorates of Education must also change. This paper reflects on these changes and suggests ‘polycentric’ inspection models that fit such a decentralized context. Examples of inspection frameworks and methods from Northern Ireland, England and the Netherlands are provided, as well as a brief discussion of the potential impact of such ‘polycentric’ models
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