The Danish effect: when citizens agree with public policy, they’re satisfied with democracy too

Inevitably, most of the people who didn’t vote for the party or parties in power will be less happy with the policies they implement. But in a survey of European countries, Christian Stecker and Markus Tausendpfund found this dissatisfaction extends to their opinion of the state of democracy in general, particularly when the government’s policies on redistribution and EU integration deviate greatly from their own. And while some countries do well when it comes to overall satisfaction – such as Sweden and Denmark – others, like Bulgaria, fare much worse

The Hard VHE Gamma-ray Emission in High-Redshift TeV Blazars: Comptonization of Cosmic Microwave Background Radiation in an Extended Jet?

Observations of very-high-energy (VHE, E > 250 GeV) gamma-ray emission from several blazars at z > 0.1 have placed stringent constraints on the elusive spectrum and intensity of the intergalactic infrared background radiation (IIBR). Correcting their observed VHE spectrum for gamma-gamma absorption even by the lowest plausible level of the IIBR provided evidence for a very hard (photon spectral index Gamma_{ph} < 2) intrinsic source spectrum out to TeV energies. Such a hard VHE gamma-ray spectrum poses a serious challenge to the conventional synchrotron-self-Compton interpretation of the VHE emission of TeV blazars and suggests the emergence of a separate emission component beyond a few hundred GeV. Here we propose that such a very hard, slowly variable VHE emission component in TeV blazars may be produced via Compton upscattering of Cosmic Microwave Background (CMB) photons by shock-accelerated electrons in an extended jet. For the case of 1ES 1101-232, this component could dominate the bolometric luminosity of the extended jet if the magnetic fields are of the order of typical intergalactic magnetic fields B ~ 10 micro-Gauss and electrons are still being accelerated out to TeV energies gamma > 4 X 10^6) on kiloparsec scales along the jet.Comment: Accepted for publication in ApJ Letter

Spatial and temporal correlations in cold Rydberg gases

Rydberg atoms, i.e. atoms with one or more highly excited electrons, show exaggerated properties compared to ground state atoms. For example, their energy levels are very sensitive to external electric fields (Stark effect) and they exhibit strong interatomic interactions, which can lead to a suppression of excitation known as the Rydberg blockade. The latter property makes Rydberg atoms promising candidates for quantum simulation and quantum computing. This work describes the direct observation of the excitation blockade for highly Stark-shifted Rydberg atoms induced by controllable dipole-dipole interactions. We investigate the electric field region around and above the classical ionization threshold, which is typically not considered suitable for blockade experiments. We excite Rydberg atoms in the energy region corresponding to the unperturbed 43S1/2 state at electric fields around 127V/cm out of a magneto-optically trapped cloud of 87Rb atoms with a temperature of 150 μK. We tune the dipole-dipole interaction by the applied electric field thus changing the electric dipole moment of the excited state. The position of the Rydberg atoms is detected by ionization and subsequent ion imaging; the controlled ionization of the atoms is achieved by adiabatic transfer of the Rydberg state to an ionizing state. For the spatially resolved detection of the atoms, a high resolution ion microscope for cold atoms has been developed and experimentally characterized. It features a maximum magnification of 1000 and sub-micrometer spatial resolution. A theoretical treatment of highly Stark-shifted Rydberg states is developed introducing a complex absorbing potential. It is capable of predicting the ionization rates of the Rydberg states for a wide range of electric fields and energies with only one free parameter. Together with the numerical calculations, measurements of the ionization spectra for different Rydberg states are presented. The 43S1/2 state is measured in an electric-field range from 125V/cm to 165V/cm (classical ionization limit 127V/cm), the 70S1/2 state in an electric-field range from 15V/cm to 35V/cm (classical ionization limit 16.1V/cm) and the 100S1/2 state in an electric-field range from 7V/cm to 19V/cm (classical ionization limit 3.7V/cm). Our results show an intricate energy level structure with broad, strongly ionizing states as well as sharp, nearly non-ionizing states. The numerical calculations are also used for the prediction of selective field ionization spectra and the results are used to identify Förster resonances in the Stark spectrum of the 45D5/2 state. Complementary to the spatially resolved measurements in high electric fields, the Rydberg blockade effect is also observed via the excitation number statistics at Förster resonances.Rydbergatome, d.h. Atome mit einem oder mehreren hochangeregten Elektronen, weisen überhöhte Eigenschaften im Vergleich zu Grundzustandsatomen auf. So sind zum Beispiel ihre Energieniveaus sehr empfindlich auf externe elektrische Felder (Stark-Effekt) und sie zeigen starke interatomare Wechselwirkungen, was zu einer Anregungsunterdrückung führen kann, die als Rydberg-Blockade bekannt ist. Letztere Eigenschaft macht Rydbergatome zu vielversprechenden Kandidaten für Quantensimulation und Quantencomputing. Die vorliegende Arbeit beschreibt die direkte Beobachtung der Anregungsblockade für hochgradig Stark-verschobene Rydbergatome induziert durch eine kontrollierbare Dipol-Dipol Wechselwirkung. Dabei wird der elektrischen Feldbereich um und über der klassischen Ionisierungsgrenze untersucht, welcher typischerweise nicht für Blockadeexperimente in Betracht gezogen wird. Rydbergatome werden im Energiebereich zugehörig zum unverschobenen 43S1/2-Zustand in elektrischen Feldern um 127V/cm aus einer magneto-optisch gefangenen Wolke bestehend aus 87Rb Atomen mit einer Temperatur von 150 μK angeregt. Die Stärke der Dipol-Dipol Wechselwirkung wird durch das angelegte elektrische Feld eingestellt, welches das elektrische Dipolmoment des angeregten Zustands verändert. Die Position der Rydbergatome wird nachgewiesen, indem sie ionisiert und durch eine Ionenoptik abgebildet werden. Eine kontrollierte Ionisation der Atome wird dabei durch einen adiabatischen Transfer des Rydbergzustands zu einem ionisierenden Zustand gewährleistet. Für den räumlich aufgelösten Nachweis der Atome wurde ein hochaufgelöstes Ionenmikroskop für kalte Atome entwickelt und experimentell charakterisiert. Es besitzt einen maximalen Vergrößerungsfaktor von 1000 und eine sub-mikrometer Auflösung. Eine theoretische Beschreibung von hochgradig Stark-verschobenen Rydbergzuständen wird durch die Einführung eines komplexen, absorbierenden Potentials ermöglicht. Die Theorie erlaubt die Vorhersage der Ionisationsraten der Rydbergzustände für einen großen Feld- und Energiebereich mit nur einem freien Parameter. Zusätzlich zu den numerischen Berechnungen werden die Ionisationsspektren verschiedener Rydbergzustände vorgestellt. Der 43S1/2-Zustand wird in einem elektrischen Feldbereich von 125V/cm bis 165V/cm gemessen (klassisches Ionisierungslimit von 127V/cm), der 70S1/2-Zustand in einem Feldbereich von 15V/cm bis 35V/cm (klassisches Ionisierungslimit 16.1V/cm) und der 100S1/2- Zustand in einem Feldbereich von 7V/cm bis 19V/cm (klassisches Ionisierungslimit 3.7V/cm). Unsere Ergebnisse zeigen eine komplizierte Energieniveaustruktur sowohl mit breiten, stark ionisierenden Zuständen als auch mit scharfen, nahezu nichtionisierenden Zuständen. Die numerischen Berechnungen werden zudem verwendet, um selektive Feldionisationsspektren vorherzusagen. Die daraus resultierenden Ergebnisse erlauben die Identifikation von Försterresonanzen im Stark-Spektrum des 45D5/2-Zustands. Ergänzend zu den räumlich aufgelösten Messungen im hohen elektrischen Feld wird der Rydberg-Blockadeeffekt auch in der Statistik der Anzahl der nachgewiesenen Rydbergatome an Försterresonanzen beobachtet

Cosmic rays at ultra high energies (Neutrinos!)

Resonant photopion production with the cosmic microwave background predicts a suppression of extragalactic protons above the famous Greisen-Zatsepin-Kuzmin cutoff at about E_{GZK} ~ 5 x 10^10 GeV. Current cosmic ray data measured by the AGASA and HiRes Collaborations do not unambiguously confirm the GZK cutoff and leave a window for speculations about the origin and chemical composition of the highest energy cosmic rays. In this work we analyze the possibility of strongly interacting neutrino primaries and derive model-independent quantitative requirements on the neutrino-nucleon inelastic cross section for a viable explanation of the cosmic ray data. Search results on weakly interacting cosmic particles from the AGASA and RICE experiments are taken into account simultaneously. Using a flexible parameterization of the inelastic neutrino-nucleon cross section we find that a combined fit of the data does not favor the Standard Model neutrino-nucleon inelastic cross section, but requires, at 90 % confidence level, a steep increase within one energy decade around E_{GZK} by four orders of magnitude. We illustrate such an enhancement within some extensions of the Standard Model. The impact of new cosmic ray data or cosmic neutrino search results on this scenario, notably from the Pierre Auger Observatory soon, can be immediately evaluated within our approach.Comment: 11 pages, 10 figures, modified autart.cls include

Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye

Multidimensional government-citizen congruence and satisfaction with democracy

In the first comparative study of multidimensional government-citizen policy congruence, this article shows that citizens are less satisfied with democracy when their views differ from that of the government on policy dimensions beyond the general left-right axis. Satisfaction is reduced by a government that deviates on European integration and redistribution and partly also on social lifestyle, immigration and environmental protection. Furthermore, this analysis identifies the level of political interest as central moderator of this relationship. Satisfaction of citizens with stronger interest in politics suffers more when there is a politically distant government. Combining data from the 2010 Chapel Hill Expert Survey and two waves of the European Social Survey, the analysis builds on information on citizen-government policy congruence of some 45,000 citizens and 31 governments in 15 Western and Central Eastern European countries. The article brings a multidimensional perspective to the study of policy congruence between citizens and governments in a time when the preference structure of parties and citizens has become increasingly complex

Controlling the Dipole Blockade and Ionization Rate of Rydberg Atoms in Strong Electric Fields

We study a novel regime of the Rydberg excitation blockade using highly Stark-shifted, yet long-living, states of Rb atoms subject to electric fields above the classical ionization limit. Such states allow tuning the dipole-dipole interaction strength while their ionization rate can be changed over two orders of magnitude by small variations of the electric field. We demonstrate laser excitation of the interacting Rydberg states followed by their detection using controlled ionization and magnified imaging with high spatial and temporal resolution. Our work reveals the hitherto unexplored possibilities to control the interaction strength and dynamically tune the ionization and detection of Rydberg atoms, which can be useful for realizing and assessing quantum simulators that vary in space and time.Comment: 6 pages, 3 figure