Second Law Violations in Lovelock Gravity for Black Hole Mergers

We study the classical second law of black hole thermodynamics, for Lovelock theories (other than General Relativity), in arbitrary dimensions. Using the standard formula for black hole entropy, we construct scenarios involving the merger of two black holes in which the entropy instantaneously decreases. Our construction involves a Kaluza-Klein compactification down to a dimension in which one of the Lovelock terms is topological. We discuss some open issues in the definition of the second law which might be used to compensate this entropy decrease.Comment: 15 pages, 1 figure, v2 Title change & minor revisions to match published version, v3 fixed accidental deletion of author name

Accessibility and Usability of Government Websites in Tanzania

The government of Tanzania has been embracing information systems specifically websites in order to widen access to government services, lower administrative costs, and to increase public participation in decision making. As a result, almost every ministry, department, and agency (MDA) has developed a website of different kind. However, the majority of existing websites were developed without sufficiently considering user needs which indicates that they do have some usability and accessibility problems. This study used SortSite tool to evaluate accessibility and usability of government websites taking a sample of 22 websites. The report from the SortSite tool was then checked against the W3 WCAG accessibility standards and Section 508 guidelines, and usability issues based on the US Federal (Usability.gov) guidelines. The results show that the majority of websites have many accessibility and usability problems that hinder citizens from accessing them. This study provides recommendations on how to improve usability and accessibility of these websites

Observation of collapse of pseudospin order in bilayer quantum Hall ferromagnets

The Hartree-Fock paradigm of bilayer quantum Hall states with finite tunneling at filling factor $\nu$=1 has full pseudospin ferromagnetic order with all the electrons in the lowest symmetric Landau level. Inelastic light scattering measurements of low energy spin excitations reveal major departures from the paradigm at relatively large tunneling gaps. The results indicate the emergence of a novel correlated quantum Hall state at $\nu$=1 characterized by reduced pseudospin order. Marked anomalies occur in spin excitations when pseudospin polarization collapses by application of in-plane magnetic fields.Comment: ReVTeX4, 4 pages, 3 EPS figure

Observation of soft magnetorotons in bilayer quantum Hall ferromagnets

Inelastic light scattering measurements of low-lying collective excitations of electron double layers in the quantum Hall state at total filling nu_T=1 reveal a deep magnetoroton in the dispersion of charge-density excitations across the tunneling gap. The roton softens and sharpens markedly when the phase boundary for transitions to highly correlated compressible states is approached. The findings are interpreted with Hartree-Fock evaluations that link soft magnetorotons to enhanced excitonic Coulomb interactions and to quantum phase transitions in the ferromagnetic bilayers.Comment: ReVTeX4, 4 pages, 4 EPS figure

Spectroscopy of soft modes and quantum phase transitions in coupled electron bilayers

Strongly-correlated two-dimensional electrons in coupled semiconductor bilayers display remarkable broken symmetry many-body states under accessible and controllable experimental conditions. In the cases of continuous quantum phase transitions soft collective modes drive the transformations that link distinct ground states of the electron double layers. In this paper we consider results showing that resonant inelastic light scattering methods detect soft collective modes of the double layers and probe their evolution with temperature and magnetic field. The light scattering experiments offer venues of research of fundamental interactions and continuous quantum phase transitions in low-dimensional electron liquids.Comment: 10 pages, 7 figure