C. Ungarelli

Large scale curvature and entropy perturbations for multiple interacting fluids

We present a gauge-invariant formalism to study the evolution of curvature perturbations in a Friedmann-Robertson-Walker universe filled by multiple interacting fluids. We resolve arbitrary perturbations into adiabatic and entropy components and derive their coupled evolution equations. We demonstrate that perturbations obeying a generalized adiabatic condition remain adiabatic in the large-scale limit, even when one includes energy transfer between fluids. As a specific application we study the recently proposed curvaton model, in which the curvaton decays into radiation. We use the coupled evolution equations to show how an initial isocurvature perturbation in the curvaton gives rise to an adiabatic curvature perturbation after the curvaton decays

Status of the GEO600 detector

Of all the large interferometric gravitational-wave detectors, the German/British project GEO600 is the only one which uses dual recycling. During the four weeks of the international S4 data-taking run it reached an instrumental duty cycle of 97% with a peak sensitivity of 7 × 10−22 Hz−1/2 at 1 kHz. This paper describes the status during S4 and improvements thereafter.

The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode.

Condensate cosmology - dark energy from dark matter

School of Physics and Astronomy, University of Birmingham Edgbaston, Birmingham, B15 2TT, UK(February 2, 2008)Imagine a scenario in which the dark energy forms via the condensation of dark matter at somelow redshift. The Compton wavelength therefore changes from small to very large at the transition,unlike quintessence or metamorphosis. We study CMB, large scale structure, supernova and radiogalaxy constraints on condensation by performing a 4 parameter likelihood analysis over the Hubbleconstant and the three parameters associated with Q, the condensate field: Ω

Gravitational waves, inflation and the cosmic microwave background: towards testing the slow-roll paradigm

One of the fundamental and yet untested predictions of inflationary models is the generation of a very weak cosmic background of gravitational radiation. We investigate the sensitivity required for a space-based gravitational wave laser interferometer with peak sensitivity at ~1 Hz to observe such signal as a function of the model parameters and compare it with indirect limits that can be set with data from present and future cosmic microwave background missions. We concentrate on signals predicted by slow-roll single-field inflationary models and instrumental configurations such as those proposed for the LISA follow-on mission: big bang observer.

Commissioning, characterization and operation of the dual-recycled GEO 600

The German-British laser-interferometric gravitational-wave detector GEO 600 is currently being commissioned as part of a worldwide network of gravitational-wave detectors. GEO 600 recently became the first kilometre-scale interferometer to employ dual recycling-an optical configuration that combines power recycling and signal recycling. We present a brief overview of the commissioning of this dual-recycled interferometer, the performance results achieved during a subsequent extended data-taking period, and the plans intended to bring GEO 600 to its final configuration.

A family of filters to search for frequency-dependent gravitational wave stochastic backgrounds

We consider a three-dimensional family of filters based on broken power-law spectra to search for gravitational wave stochastic backgrounds in the data from Earth-based laser interferometers. We show that such templates produce the necessary fitting factor for a wide class of cosmological backgrounds and astrophysical foregrounds, and that the total number of filters required to search for those signals in the data from first generation laser interferometers operating at the design sensitivity is fairly small.