Soliton localization in Bose-Einstein condensates with time-dependent harmonic potential and scattering length

We derive exact solitonic solutions of a class of Gross-Pitaevskii equations with time-dependent harmonic trapping potential and interatomic interaction. We find families of exact single-solitonic, multi-solitonic, and solitary wave solutions. We show that, with the special case of an oscillating trapping potential and interatomic interaction, a soliton can be localized indefinitely at an arbitrary position. The localization is shown to be experimentally possible for sufficiently long time even with only an oscillating trapping potential and a constant interatomic interaction.Comment: 19 pages, 11 figures, accepted for publication in J.Phys.

When Statutory Regimes Collide:Will Wisconsin Right to Life and Citizens United Invalidate Federal Tax Regulation of Campaign Activity?

In Federal Election Commission v. Wisconsin Right to Life (2007) and Citizens United v. Federal Elections Commission (2010), the United States Supreme Court dramatically reduced the ability of Congress to regulate campaign finance activities of corporations and others active in elections. Many of the same activities are still subject to restrictions by the Internal Revenue Code, which regulates the type and amount of political campaign activities that certain nonprofits exempt under federal tax law can engage in. In the wake of the campaign finance decisions, the constitutionality of the tax law’s restrictions on campaign activity is now being challenged in the lower courts. This Article analyzes the two recent campaign finance decisions and campaign finance precedents more broadly to determine how, if at all, the Roberts’ Court’s campaign finance jurisprudence is likely to alter existing tax law jurisprudence in the area of campaign activity. It finds that, for the most part, tax law constitutional doctrines have developed independently of other areas of First Amendment free speech law. Based upon an analysis of the distinctive tax law doctrines, the Article concludes that the tax law provision prohibiting section 501(c)(3) charities from engaging in campaigns is likely to withstand challenges arguing that the provision prevents these nonprofits from engaging in protected political speech. However, there is some likelihood that the tax law prohibition is vulnerable to constitutional attack under traditional doctrines of vagueness or overbreadth due to the lack of precision of the terms of the political prohibition, as these have been elaborated by the IRS and the courts to date

S-particles at their naturalness limits

We draw attention on a particular configuration of supersymmetric particle masses, motivated by naturalness and flavour considerations. All its relevant phenomenological properties for the LHC are described in terms of a few physical parameters, irrespective of the underlying theoretical model. This allows a simple characterization of its main features, useful to define a strategy for its discovery.Comment: 13 pages, 8 figures, added reference

Regulating Systemic Risk: Towards an Analytical Framework

The global financial crisis demonstrated the inability and unwillingness of financial market participants to safeguard the stability of the financial system. It also highlighted the enormous direct and indirect costs of addressing systemic crises after they have occurred, as opposed to attempting to prevent them from arising. Governments and international organizations are responding with measures intended to make the financial system more resilient to economic shocks, many of which will be implemented by regulatory bodies over time. These measures suffer, however, from the lack of a theoretical account of how systemic risk propagates within the financial system and why regulatory intervention is needed to disrupt it. In this Article, we address this deficiency by examining how systemic risk is transmitted. We then proceed to explain why, in the absence of regulation, market participants cannot be relied upon to disrupt or otherwise limit the transmission of systemic risk. Finally, we advance an analytical framework to inform systemic risk regulation

Representations of the discrete inhomogeneous Lorentz group and Dirac wave equation on the lattice

We propose the fundamental and two dimensional representation of the Lorentz groups on a (3+1)-dimensional hypercubic lattice, from which representations of higher dimensions can be constructed. For the unitary representation of the discrete translation group we use the kernel of the Fourier transform. From the Dirac representation of the Lorentz group (including reflections) we derive in a natural way the wave equation on the lattice for spin 1/2 particles. Finally the induced representation of the discrete inhomogeneous Lorentz group is constructed by standard methods and its connection with the continuous case is discussed.Comment: LaTeX, 20 pages, 1 eps figure, uses iopconf.sty (late submission

Language of Lullabies: The Russification and De-Russification of the Baltic States

This article argues that the laws for promotion of the national languages are a legitimate means for the Baltic states to establish their cultural independence from Russia and the former Soviet Union