872 research outputs found
Exotic Superconducting Phases of Ultracold Atom Mixtures on Triangular Lattices
We study the phase diagram of two-dimensional Bose-Fermi mixtures of
ultracold atoms on a triangular optical lattice, in the limit when the velocity
of bosonic condensate fluctuations is much larger than the Fermi velocity.
We contrast this work with our previous results for a square lattice system
in Phys. Rev. Lett. {\bf 97}, 030601 (2006).
Using functional renormalization group techniques we show that the phase
diagrams for a triangular lattice contain exotic superconducting phases. For
spin-1/2 fermions on an isotropic lattice we find a competition of -, -,
extended -, and -wave symmetry, as well as antiferromagnetic order. For
an anisotropic lattice, we further find an extended p-wave phase. A Bose-Fermi
mixture with spinless fermions on an isotropic lattice shows a competition
between - and -wave symmetry.
These phases can be traced back to the geometric shapes of the Fermi surfaces
in various regimes, as well as the intrinsic frustration of a triangular
lattice.Comment: 6 pages, 4 figures, extended version, slight modification
Spectroscopy of Superfluid Pairing in Atomic Fermi Gases
We study the dynamic structure factor for density and spin within the
crossover from BCS superfluidity of atomic fermions to the Bose-Einstein
condensation of molecules. Both structure factors are experimentally accessible
via Bragg spectroscopy, and allow for the identification of the pairing
mechanism: the spin structure factor allows for the determination of the two
particle gap, while the collective sound mode in the density structure reveals
the superfluid state.Comment: 4 pages, 3 figure
Luminescence quenching of the triplet excimer state by air traces in gaseous argon
While developing a liquid argon detector for dark matter searches we
investigate the influence of air contamination on the VUV scintillation yield
in gaseous argon at atmospheric pressure. We determine with a radioactive
alpha-source the photon yield for various partial air pressures and different
reflectors and wavelength shifters. We find for the fast scintillation
component a time constant tau1= 11.3 +- 2.8 ns, independent of gas purity.
However, the decay time of the slow component depends on gas purity and is a
good indicator for the total VUV light yield. This dependence is attributed to
impurities destroying the long-lived argon excimer states. The population ratio
between the slowly and the fast decaying excimer states is determined for
alpha-particles to be 5.5 +-0.6 in argon gas at 1100 mbar and room temperature.
The measured mean life of the slow component is tau2 = 3.140 +- 0.067 microsec
at a partial air pressure of 2 x 10-6 mbar.Comment: 7 pages submitted to NIM
Neer vs. anatomically based humeral prostheses - Biomechanical comparison with a comprehensive model of the shoulder
Gezonde winterbijen door het afnemen van broed
De enorme verliezen aan bijenvolken bij veel imkers zijn vaak te herleiden tot een slechte gezondheid van de bjienvolken. Die gezondheid houdt vooral verband met de varroabesmetting van het in augustus en september opgekweekte broed, wat dan leidt tot wintersterfte. Dr. Ralph Büchler stelt zich de vraag of er een fundamentele verbetering van de gezondheidstoestand gerealiseerd kan worden door een verandering van bedrijfsmethode en verzorging van de volken. Hij stelt voor om te leren van de natuurlijke overlevingsstrategieën van bijen. In dit artikel geeft hij resultaten van zijn onderzoek en daaruit leidt hij praktische behandelingsadviezen a
Hoop op varroaresistentie : effectievere selectie met behulp van VSH
Varroa is duidelijk de hoofdoorzaak van de grote bijensterfte zoals we die in Duitsland ook in 2015 weer zien. Onder grote druk wordt wereldwijd aan methoden gewerkt om het probleem onder controle te krijgen. Dr. Ralph Büchler en zijn team werken in Kirchhain al jaren doelgericht aan selectie en teelt van carnicabijen. Bij de selectie op VSH (varroa-gevoelig hygiënisch gedrag) tekenen zich de eerste resultaten af
Improved Method for the Determination of Phospholipase A2 Catalytic Activity Concentration in Human Serum and Ascites
Peer Reviewe
Minimal instances for toric code ground states
A decade ago Kitaev's toric code model established the new paradigm of
topological quantum computation. Due to remarkable theoretical and experimental
progress, the quantum simulation of such complex many-body systems is now
within the realms of possibility. Here we consider the question, to which
extent the ground states of small toric code systems differ from LU-equivalent
graph states. We argue that simplistic (though experimentally attractive)
setups obliterate the differences between the toric code and equivalent graph
states; hence we search for the smallest setups on the square- and triangular
lattice, such that the quasi-locality of the toric code hamiltonian becomes a
distinctive feature. To this end, a purely geometric procedure to transform a
given toric code setup into an LC-equivalent graph state is derived. In
combination with an algorithmic computation of LC-equivalent graph states, we
find the smallest non-trivial setup on the square lattice to contain 5
plaquettes and 16 qubits; on the triangular lattice the number of plaquettes
and qubits is reduced to 4 and 9, respectively.Comment: 14 pages, 11 figure
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