Attractive Bose-Einstein Condensates in three dimensions under rotation: Revisiting the problem of stability of the ground state in harmonic traps

We study harmonically trapped ultracold Bose gases with attractive interparticle interactions under external rotation in three spatial dimensions and determine the critical value of the attraction strength where the gas collapses as a function of the rotation frequency. To this end we examine the stationary state in the corotating frame with a many-body approach as well as within the Gross-Pitaevskii theory of systems in traps with different anisotropies. In contrast to recently reported results [N. A. Jamaludin, N. G. Parker, and A. M. Martin, Phys. Rev. A \textbf{77}, 051603(R) (2008)], we find that the collapse is not postponed in the presence of rotation. Unlike repulsive gases, the properties of the attractive system remain practically unchanged under rotation in isotropic and slightly anisotropic traps.Comment: 15 pages, 1 figure, 1 tabl

Phases, many-body entropy measures and coherence of interacting bosons in optical lattices

Already a few bosons with contact interparticle interactions in small optical lattices feature a variety of quantum phases: superfluid, Mott-insulator and fermionized Tonks gases can be probed in such systems. To detect these phases -- pivotal for both experiment and theory -- as well as their many-body properties we analyze several distinct measures for the one-body and many-body Shannon information entropies. We exemplify the connection of these entropies with spatial correlations in the many-body state by contrasting them to the Glauber normalized correlation functions. To obtain the ground-state for lattices with commensurate filling (i.e. an integer number of particles per site) for the full range of repulsive interparticle interactions we utilize the multiconfigurational time-dependent Hartree method for bosons (MCTDHB) in order to solve the many-boson Schr\"odinger equation. We demonstrate that all emergent phases -- the superfluid, the Mott insulator, and the fermionized gas can be characterized equivalently by our many-body entropy measures and by Glauber's normalized correlation functions. In contrast to our many-body entropy measures, single-particle entropy cannot capture these transitions.Comment: 11 pages, 7 figures, software available at http://ultracold.or

Models of Party Democracy : Patterns of Party Regulation in Post-War European Constitutions

This article investigates the ways in which political parties are codified in modern democratic constitutions, providing a unique cross-sectional and longitudinal overview of the patterns of party constitutionalization in post-war Europe. Although the constitutions of western liberal democracies traditionally have paid little attention to the role of parties, evidence suggests that in contemporary democracies, both old and new, they are increasingly accorded a formal constitutional status. Little is known, however, about the substantive content of their constitutional position or about the normative connotations of their constitutional codification. In this article, we demonstrate that there is a clear correlation between the nature and the intensity of party constitutionalization and the newness and historical experience of democracy and that, with time, the constitutional regulation of the extra-parliamentary organization and the parties’ rights and duties has gained in importance at the expense of their parliamentary and electoral roles. The analysis furthermore suggests that three distinct models of party constitutionalization can be identified – Defending Democracy, Parties in Public Office, and Parties as Public Utilities – each of which is related to a particular conception of party democracy

Parametric Excitation of a Bose-Einstein Condensate: From Faraday Waves to Granulation

We explore, both experimentally and theoretically, the response of an elongated Bose-Einstein condensate to modulated interactions. We identify two distinct regimes differing in modulation frequency and modulation strength. Longitudinal surface waves are generated either resonantly or parametrically for modulation frequencies near the radial trap frequency or twice the trap frequency, respectively. The dispersion of these waves, the latter being a Faraday wave, is well-reproduced by a mean-field theory that accounts for the 3D nature of the elongated condensate. In contrast, in the regime of lower modulation frequencies we find that no clear resonances occur, but with increased modulation strength, the condensate forms an irregular granulated distribution that is outside the scope of a mean-field approach. We find that the granulated condensate is characterized by large quantum fluctuations and correlations, which are well-described with single-shot simulations obtained from wavefunctions computed by a beyond mean-field theory at zero temperature, the multiconfigurational time-dependent Hartree for bosons method.Comment: To be published in PRX (2019

ALISON SAAR: Of Aether and Earthe

Drawing inspiration from the imagery of African, Caribbean and Latin American folk art as well as found objects and her own upbringing in a multiracial artist family, Los Angeles artist Alison Saar (born 1956) creates works that reflect on the duality of body and spirit within the context of a larger cultural setting, focusing in particular on black womanhood. In life-size wooden sculptures and mixed-media portraits, Saar crafts complex narratives about diasporic identity. This publication accompanies an exhibition co-organized by the Benton Museum of Art at Pomona College in Claremont, California and the Armory Center for the Arts in Pasadena, California. Alongside photographic reproductions of Saar\u27s work, the cloth bound catalog contains an interview between Saar and the exhibit\u27s co-curator, never-before-published photographs from the artist\u27s childhood and poetry by Camille Dungy, Harryette Mullen and Evie Shockley. Exhibition: Benton Museum of Art at Pomona College, Claremont, USA (01.09.-19.12.2020

From parliamentary pay to party funding: the acceptability of informal institutions in advanced democracies

While direct state funding of political parties has been a prominent theme in cross-national research over the last decade, we still know little about party strategies to access state resources that are not explicitly earmarked for partisan usage. This paper looks at one widespread but often overlooked informal party practice: the ‘taxing’ of MP salaries, i.e., the regular transfer of fixed salary shares to party coffers. Building on notions of informal institutions developed in work on new democracies, our theoretical approach specifies factors that shape the acceptability of this legally non-enforceable intra-organisational practice. It is tested through a selection model applied to a unique data set covering 124 parties across 19 advanced democracies. Controlling for a range of party- and institutional-level variables, we find that the presence of a taxing rule and the collection of demanding tax shares are more common in leftist parties (high internal acceptability) and in systems in which the penetration of state institutions by political parties is intense (high external acceptability)