We study the dynamics of a dilute Bose gas at zero temperature following a sudden quench of the scattering length from a noninteracting Bose condensate to unitarity (infinite scattering length). We apply three complementary approaches to understand the momentum distribution and loss rates. First, using a time-dependent variational ansatz for the many-body state, we calculate the dynamics of the momentum distribution. Second, we demonstrate that, at short times and large momenta compared to those set by the density, the physics can be well understood within a simple, analytic two-body model. We derive a quantitative prediction for the evolution of Tan's contact, which increases linearly at short times. We also study the three-body losses at finite densities. Consistent with experiments, we observe lifetimes which are long compared to the dynamics of large momentum modes.Ultracold atomic physics offers unique opportunities to study strongly correlated systems due to the tunability of the interatomic interaction, parameterized by the s-wave scattering length, a, via Fano-Feshbach resonances [1]. Particularly interesting are quantum gases at unitarity, where a is much larger than any other length scale in the system. Such systems are predicted to exhibit universal behaviour, which depends only on the mean interparticle separation. Here the physics is highly nonperturbative, with no obvious small parameter. Investigations to date have predominantly focused on the Fermi gas, where three-body recombination is naturally suppressed by statistical repulsion [2]. Over the last decade, a general consensus seems to have emerged on many issues surrounding the unitary Fermi gas [3][4][5][6][7]. Theoretical understanding of the unitary Bose gas is far less developed. Although experiments in the quantum degenerate regime have been able to measure beyond mean field effects, such as the famous Lee-Huang-Yang correction [8,9] for values of na 3 7 × 10 −3 (n being the three dimensional number density), progress towards a unitary Bose gas with na 3 ≫ 1 is hampered by the catastrophic scaling of three-body loss in the system. At zero temperature, in the dilute gas, na 3 ≪ 1, with a ≫ r 0 where r 0 is the van der Waals length, the three-body recombination constant scales universally as L 3 ∝ a 4 /m [10][11][12][13][14]. This a 4 scaling renders any adiabatic transfer from the weakly interacting limit to the unitary limit impossible [15,16]. As a → ∞, although remaining dilute compared to the van der Waals length, the long-range aspects of Efimov physics become important [11][12][13][14]. One approach to limiting losses has emerged by considering non-degenerate unitary Bose gases [17,18], where the thermal de Broglie wavelength, λ T , can provide a small parameter nλ 3 T ≪ 1, and low-recombination regimes exist [19].A brazen new approach adopted in a recent experiment [20] utilizes an effectively diabatic quench in the scattering length to unitarity, with the initial gas temperature deeply degenerate. Although dimensional analysis requir...

The behavior of the spatial two-particle correlation function is surveyed in detail for a uniform onedimensional Bose gas with repulsive contact interactions at finite temperatures. Long-, medium-, and shortrange effects are investigated. The results span the entire range of physical regimes from ideal gas to strongly interacting and from zero temperature to high temperature ͑Gross-Pitaevskii͒ and strongly interacting ͑Tonks-Girardeau͒ gases. We present perturbative analytic methods, available at strong and weak couplings, and first-principles numerical results using imaginary time simulations with the gauge-P representation in regimes where perturbative methods are invalid. Nontrivial effects are observed from the interplay of thermally induced bunching behavior versus interaction induced antibunching.

SUMMARYForty-eight 4-month-old lambs, reared worm-free from birth, were allocated to six groups and offered ad libitum a complete diet containing 139 g crude protein/kg D.M. One group was killed at the outset as initial control (CI). Further groups, ALC, 1, 2, 3 and 4 were dosed daily for 84 days with zero, 1000, 3000, 5000 and 5000 larvae of Ostertagia circumcincta, respectively. Lambs in group 4 also received anthelmintic (fenbendazole, 5 mg/kg) on days 21, 42, 63 and 84. Lambs were killed after 98 days and their carcasses and those of the initial controls analysed for fat, protein and mineral contents.

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