Atom Interferometry in a Vertical Optical Lattice

We have studied the interference of degenerate quantum gases in a vertical optical lattice. The coherence of the atoms leads to an interference pattern when the atoms are released from the lattice. This has been shown for a Bose-Einstein condensate in early experiments. Here we demonstrate that also for fermions an interference pattern can be observed provided that the momentum distribution is smaller then the recoil momentum of the lattice. Special attention is given to the role of interactions which wash out the interference pattern for a condensate but do not affect a spin polarized Fermi gas, where collisions at ultra cold temperatures are forbidden. Comparing the interference of the two quantum gases we find a clear superiority of fermions for trapped atom interferometry.Comment: 10 pages, 5 figure

U.S. Climate Litigation in the Age of Trump: Full Term

From beginning to end, the Trump administration pursued an agenda of climate deregulation. The administration aimed a portfolio of actions at weakening federal climate protections and promoting fossil fuels.1 The executive branch did so by aiming to revise and rescind all major Obama-era agency rules to regulate greenhouse gas emissions, leasing public lands for fossil fuel development, attempting to curtail climate impact consideration in National Environmental Policy Act and Endangered Species Act reviews, and withdrawing energy efficiency measures, among other climate deregulation actions.2 Collectively, this effort served to advance the view that humans are not causing serious climate change and that environmental regulations confer many costs and few benefits.3 Litigants responded and interacted with the administration’s climate deregulation agenda by filing hundreds of lawsuits in jurisdictions across the country. This analysis takes stock of 378 lawsuits during the Trump era where climate change was material to the case and the case implicated issues of federal law and/or federal policy. The vast majority of these suits, 89%, aimed to strengthen climate protection or weaken climate deregulation efforts. The other 11% sought to bolster climate deregulation efforts

Anharmonic parametric excitation in optical lattices

We study both experimentally and theoretically the losses induced by parametric excitation in far-off-resonance optical lattices. The atoms confined in a 1D sinusoidal lattice present an excitation spectrum and dynamics substantially different from those expected for a harmonic potential. We develop a model based on the actual atomic Hamiltonian in the lattice and we introduce semiempirically a broadening of the width of lattice energy bands which can physically arise from inhomogeneities and fluctuations of the lattice, and also from atomic collisions. The position and strength of the parametric resonances and the evolution of the number of trapped atoms are satisfactorily described by our model.Comment: 7 pages, 5 figure

ITLOS Advisory Opinion on Climate Change: Summary of Briefs and Statements Submitted to the Tribunal

This report provides a summary of the briefs and statements submitted to the International Tribunal for the Law of the Sea (ITLOS) in response to the Co-Chairs of Commission of Small Island States (COSIS)’ request for an advisory opinion on climate change-related legal questions. The central issue before the ITLOS is whether State Parties to UNCLOS have specific obligations regarding the prevention, reduction, and control of marine environmental pollution stemming from climate change, as well as the protection and preservation of the marine environment concerning climate change impacts. While States and civil society organizations have put forward a variety of arguments in their briefs and statements, they mostly relate to three pivotal aspects of international maritime law: (i) ITLOS’ jurisdiction and ability to issue an advisory opinion on climate change, (ii) the definition of marine pollution under UNCLOS, and (iii) the responsibilities of States in the context of climate change under the UNCLOS. Authors: Ahmed Mohammed Abdelsalam, Sabah Ahmed, Maria Jose Alarcon, Irene Antonopoulos, Jorge Alejandro Carrillo Bañuelos, Valeria Berros, Juan Sebastián Castellanos, Asteropi Chatzinikola-Iliopoulos, Moumita Das Gupta, Antoine De Spiegeleir, Fernand Guevara Mekongo Mballa, Millie John-Pierre, Isabella Kiechle, Jan-Baptist Lemaire, Sol Meckievi, Milagros Mutsios-Ramsay, Yumeno Grace Nishikawa, Natalia Urzola, Ademola Oluborode Jegede, Zunaida Moosa Wadiwal

Direct evaporative cooling of 39K atoms to Bose-Einstein condensation

We report the realization of Bose-Einstein condensates of 39K atoms without the aid of an additional atomic coolant. Our route to Bose-Einstein condensation comprises Sub Doppler laser cooling of large atomic clouds with more than 10^10 atoms and evaporative cooling in optical dipole traps where the collisional cross section can be increased using magnetic Feshbach resonances. Large condensates with almost 10^6 atoms can be produced in less than 15 seconds. Our achievements eliminate the need for sympathetic cooling with Rb atoms which was the usual route implemented till date due to the unfavourable collisional property of 39K. Our findings simplify the experimental set-up for producing Bose-Einstein condensates of 39K atoms with tunable interactions, which have a wide variety of promising applications including atom-interferometry to studies on the interplay of disorder and interactions in quantum gases.Comment: 7 pages, 6 figure

Emergence of turbulence in an oscillating Bose-Einstein condensate

We report on the experimental observation of vortices tangle in an atomic BEC of Rb-87 atoms when an external oscillatory perturbation is introduced in the trap. The vortices tangle configuration is a signature of the presence of a turbulent regime in the cloud. We also show that this turbulent cloud has suppression of the aspect ratio inversion typically observed in quantum degenerate bosonic gases during free expansion. Instead, the cloud expands keeping the ratio between their axis constant. Turbulence in atomic superfluids may constitute an alternative system to investigate decay mechanisms as well as to test fundamental theoretical aspects in this field.Comment: accepted for Phys. Rev. Let