Nonlinear Self-Trapping of Matter Waves in Periodic Potentials

We report the first experimental observation of nonlinear self-trapping of Bose-condensed 87Rb atoms in a one dimensional waveguide with a superimposed deep periodic potential . The trapping effect is confirmed directly by imaging the atomic spatial distribution. Increasing the nonlinearity we move the system from the diffusive regime, characterized by an expansion of the condensate, to the nonlinearity dominated self-trapping regime, where the initial expansion stops and the width remains finite. The data are in quantitative agreement with the solutions of the corresponding discrete nonlinear equation. Our results reveal that the effect of nonlinear self-trapping is of local nature, and is closely related to the macroscopic self-trapping phenomenon already predicted for double-well systems.Comment: 5 pages, 4 figure

Bloch Structures in a Rotating Bose-Einstein Condensate

A rotating Bose-Einstein condensate is shown to exhibit a Bloch band structure without the need of periodic potential. Vortices enter the condensate by a mechanism similar to the Bragg reflection, if the frequency of a rotating drive or the strength of interaction is adiabatically changed. A localized state analogous to a gap soliton in a periodic system is predicted near the edge of the Brillouin zone.Comment: 4 pages, 3 figure

Bright gap solitons of atoms with repulsive interaction

We report on the first experimental observation of bright matter-wave solitons for 87Rb atoms with repulsive atom-atom interaction. This counter intuitive situation arises inside a weak periodic potential, where anomalous dispersion can be realized at the Brillouin zone boundary. If the coherent atomic wavepacket is prepared at the corresponding band edge a bright soliton is formed inside the gap. The strength of our system is the precise control of preparation and real time manipulation, allowing the systematic investigation of gap solitons.Comment: 4 pages, 4 figure

The 3D Geometry of Reflection Nebulae IC 59 and IC 63 with their illuminating Star Gamma Cas

The early-type star $\gamma$ Cas illuminates the reflection nebulae IC 59 and IC 63, creating two photo-dissociation regions (PDRs). Uncertainties about the distances to the nebulae and the resulting uncertainty about the density of the radiation fields incident on their surfaces have hampered the study of these PDRs during the past three decades. We employed far-UV -- optical nebula -- star colour differences of dust-scattered light to infer the locations of the nebulae relative to the plane of the sky containing $\gamma$ Cas, finding IC 63 to be positioned behind the star and IC 59 in front of the star. To obtain the linear distances of the nebulae relative to $\gamma$ Cas, we fit far-infrared archival $\textit{Herschel}$ flux data for IC 59 and IC 63 with modified blackbody (MBB) curves and relate the resulting dust temperatures with the luminosity of $\gamma$ Cas, yielding approximate distances of 4.15 pc for IC 59 and 2.3 pc for IC 63. With these distances, using updated far-UV flux data in the 6 eV - 13.6 eV range for $\gamma$ Cas with two recent determinations of the interstellar extinction for $\gamma$ Cas, we estimate that the far-UV radiation density at the surface of IC 63 takes on values of $G_0$ = 58 or $G_0$ = 38 with respective values for E(B-V) for $\gamma$ Cas of 0.08 and 0.04 mag. This is a substantial reduction from the range 150 $\le$ $G_0$ $\le$ 650 used for IC 63 during the past three decades. The corresponding, even lower new values for IC 59 are $G_0$ = 18 and $G_0$ = 12.Comment: Accepted for publication on January 4th, 2024 by the Monthly Notices of the Royal Astronomical Societ

A rare study from the wintering grounds provides insight into the costs of malaria infection for migratory birds

Malaria parasites can have strong effects on the population dynamics and evolution of migratory bird species. In many species, parasite transmission occurs on the wintering grounds, but studies to determine the consequences of infection have taken place during the breeding season, when malaria parasites circulate at chronic levels. We examined the predictors of malarial infections for great reed warblers during the northern winter in Africa, where active parasite transmission is thought to occur and naïve individuals experience acute infections. Counter to expectations, we found that winter infection intensities were lower than those encountered on the breeding grounds. One potential explanation is that reduced immune function during breeding allows parasites to persist at higher chronic intensities. We found no relationships between the incidence or intensity of infection on condition (as measured by scaled mass index, plasma metabolites, and feather corticosterone), spring migration departure dates, or home range sizes. We also tested a prediction of the Hamilton–Zuk hypothesis and found that male ornament (song) quality was unrelated to parasitic infection status. Overall, our results provide the first evidence that long‐distance migrants captured on their wintering grounds are in the chronic stage of infection, and suggest that winter studies may fare no better than breeding studies at determining the costs of acute malarial infection for great reed warblers.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/jav.0087

Kinks in the discrete sine-Gordon model with Kac-Baker long-range interactions

We study effects of Kac-Baker long-range dispersive interaction (LRI) between particles on kink properties in the discrete sine-Gordon model. We show that the kink width increases indefinitely as the range of LRI grows only in the case of strong interparticle coupling. On the contrary, the kink becomes intrinsically localized if the coupling is under some critical value. Correspondingly, the Peierls-Nabarro barrier vanishes as the range of LRI increases for supercritical values of the coupling but remains finite for subcritical values. We demonstrate that LRI essentially transforms the internal dynamics of the kinks, specifically creating their internal localized and quasilocalized modes. We also show that moving kinks radiate plane waves due to break of the Lorentz invariance by LRI.Comment: 11 pages (LaTeX) and 14 figures (Postscript); submitted to Phys. Rev.