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2nd Iberian Gravitational Wave Meeting

15-17 February 2012, Barcelona, Spain

2nd IBERIAN GRAVITATIONAL WAVE MEETINGBarcelona, February 15-17, 2012

The organizing committee:

Priscilla CanizaresIvan LloroAlberto LoboMiquel NofrariasCarlos F. SopuertaUlrich Sperhake

http://www.ice.csic.es/research/IGWMweb

http://www.ice.csic.es/research/IGWMweb/

Institut de Ciencies del’Espai (CSIC-IEEC)

ICE (CSIC-IEEC)

2nd Iberian Gravitational Wave Meeting. Barcelona, 15-17 February 2012 3

Programme Summary

Wednesday 15th

10:00 - 11:00 Registration, coffee and Welcome

Session Chair: J.A. Lobo

11:00 - 11:35 [+05] E. Porter eLISA/NGO : a European detector for low frequency

gravitational waves

11:40 - 12:15 [+05] M. Hewitson The LISA Pathfinder mission

12:20 - 12:55 [+05] A. Sintes Towards Gravitational-Wave Astronomy with ground-based

observatories

13:00 - 15:00 Lunch

Session Chair: M. Nofrarias

15:00 - 15:35 [+5] M. Mitchell Quantum enhancement of interferometers and the Heisenberg

limit

15:40 - 16:15 [+5] A. Lobo Latest developments in LISA PathFinder and the Munich Test

16:20 - 16:50 Coffee Break

16:50 - 17:10 [+5] L. Ferraioli Quantitative analysis of LISA Pathfinder test-mass noise

17:15 - 17:35 [+5] N. Karnesis A Bayesian Framework for Model Selection for LISA Pathfinder

17:40 - 18:00 [+5] F. Gibert Modelling the Thermal Diagnostics experiments for LISA

Pathfinder

18:05 - 18:25 [+5] T. Schwarze Deep phase interferometry

18:30 Adjourn

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4 2nd Iberian Gravitational Wave Meeting. Barcelona, 15-17 February 2012

Thursday 16th

Session Chair: E. Porter

09:00 - 09:40 [+05] F. Guzman Gravitational wave observatories: laser interferometry

09:45 - 10:25 [+05] C.F. Sopuerta On the modeling of Intermediate- and Extreme-Mass-Ratio

Inspirals


11:00 - 11:35 [+05] S. Husa The Ninja project and surveys of the binary black hole

parameter space

11:40 - 12:15 [+05] P. Pani Tidal acceleration of black holes and floating orbits in

scalar-tensor theories

12:20 - 12:40 [+05] F. Galeazzi Neutron star simulations with microphysics: issues and recipes

12:45 - 13:05 [+05] S. Bernuzzi Gravitational waves from neutron star binaries: accuracy

and tidal effects in the late inspiral

13:10 - 15:00 Lunch

Session Chair: A. Sintes

15:00 - 15:20 [+5] I. Cordero Partially implicit Runge-Kutta methods for wave-like

-Carrion equations in spherical-type coordinates

15:25 - 15:45 [+5] P. Canizares Testing Chern-Simons Modified Gravity with GW detections

of Extreme-Mass-Ratio Binaries

15:50 - 16:10 [+5] C. Berry Extreme-mass-ratio bursts from the Galactic Centre


16:45 - 17:05 [+5] N. Johnson Multimessenger observations of white dwarf binaries with

-McDaniel gravitational and electromagnetic radiation

17:10 - 17:30 [+5] M. Ruiz Magnetospheres of compact objects in Force-Free Plasma

17:35 - 17:55 [+5] M. Gabler Magneto-elastic oscillations of magnetars

18:00 - 18:20 [+5] S. Gil Experiments on Outreach: From Press Releases to Social

-Casanova Networks and Computer Games

18:25 Adjourn

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Friday 17th

Session Chair: C.F. Sopuerta

09:00 - 09:40 [+05] J.M. Ibanez Current Issues in Numerical Relativistic (Magneto-)

Hydrodynamics

09:45 - 10:25 [+05] C. Trenkel Testing Modified Newtonian Dynamics with LISA Pathfinder


11:00 - 11:35 [+05] D. Espriu Gravitational waves in the presence of a cosmological constant

11:40 - 12:15 [+05] P. Amaro How stars distribute around massive black holes: hope for EM

-Seoane cusps in distress and a probe to DM cusps

12:20 - 12:55 [+05] U. Sperhake Black-hole binary simulations on supercomputers

13:00 - 13:20 [+05] S. Taylor Hubble Without The Hubble: Cosmology Using Advanced

GW Detectors Alone

13:25 End of the Meeting

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Abstracts

Pau Amaro-Seoane (Albert Einstein Institute, Golm, Germany)

How stars distribute around massive black holes: hope for EM cusps in distress and a probe to DM cusps

One of the most interesting sources of gravitational waves is the inspiral of compact objects on to a massive black hole (MBH),

commonly referred to as an extreme-mass ratio inspiral. The small object, typically a stellar black hole, emits significant

amounts of GW along each orbit in the detector bandwidth. On the other hand, recent observations of the Galactic center

revealed a dearth of giant stars inside the inner parsec relative to the numbers theoretically expected for a fully relaxed stellar

cusp. The possibility of unrelaxed nuclei (or, equivalently, with no or only a very shallow cusp) adds substantial uncertainty to

the estimates. I show that under quite generic initial conditions, the time required for the growth of a relaxed, mass segregated

stellar cusp is shorter than a Hubble time for MBHs with masses . 5× 106 M�. I.e. for galactic nuclei well within the eLISA

range, the ESA future GW observatory. I will also discuss the potential role of chaos in the EMRI problem induced by the

stellar cusp, as well as the role of WD EMRIs as a probe to Dark Matter cusps in dense stellar systems.

Sebastiano Bernuzzi (TPI Jena, Germany)

Gravitational waves from neutron star binaries: accuracy and tidal effects in the late inspiral

I will report about results from recent numerical relativity simulations of the late inspiral - merger phase of neutron star

binaries. The impact of truncation and finite extraction errors on the waveforms will be discussed, as well as other systematic

source of uncertainties. The estimated error bars may be relevant in case numerical waveforms are employed for data analysis

purposes. I will present a comparison between nine orbits quasi-circular inspiral and post-Newtonian waveforms, and discuss

the impact of tidal effects. Finally, I will talk about recent findings on tidal signatures in highly eccentric mergers.

Christopher Berry (Institute of Astronomy, University of Cambridge,UK)

Extreme-mass-ratio bursts from the Galactic Centre

An extreme-mass-ratio burst (EMRB) is a short gravitational wave signal emitted by a small object on a highly eccentric orbit

about a much more massive body. Their short duration means they carry less information than extreme-mass-ratio inspirals,

and for this reason have been less well studied. However, an EMRB from our own Galactic centre should be detectable with

a space-borne detector. I will discuss how much information it might be possible to squeeze from an EMRB, and what this

could tell us about the massive black hole at the heart of the Galaxy. In particular, a constraint on the spin of the black hole

would be of interest, since this should be determined by the past history of the black hole, and, by implication, the Galaxy itself.

Priscil·la Canizares (Institute of Astronomy, University of Cambridge,UK)

Testing Chern-Simons Modified Gravity with Gravitational-Wave detections of Extreme-Mass-Ratio Binaries

Binary systems with extreme-mass ratio are one of the most promising sources of Gravitational-Waves (GWs) for space-based

detectors like LISA. These binaries, made up for a Stellar Compact Object (SCO) and a Massive Black Hole (MBH), emit

GW signals which carry information about the spacetime geometry of the MBH and the physical parameters of the system.

Their detection will enable us to explore the strong gravitational field region in the vicinity of the MBH and test the theory

of gravity governing the binary. In this regard, the development of a practical methodology for computing the generation and

propagation of GWs in theories of gravity different than General Relativity (GR) has only recently begun. In this talk we

present a first study to determine to what extent a space-based GW observatory like LISA could distinguish between GR and

other alternative theory of gravity. In particular, we focus on a modified theory of gravity parametrized by a four-dimensional

Chern-Simons (CS) gravitational term. We model the motion of the SCO as evolving geodesics including radiation-reaction

(RR) effects and the GWs are described with a multipolar formalism up to quadrupolar order. With our formalism, we study

a five dimensional space of capture-event parameters, including the CS parameter, finding that a GW detector like LISA could

discriminate between GR and Dynamical Chern-Simons modified theory within a fractional error of ∼ 10−2.

Isabel Cordero Carrion (Max Planck Institute for Astrophysics, Garching, Germany)

Partially implicit Runge-Kutta methods for wave-like equations in spherical-type coordinates

In this talk, I will comment on a set of partially implicit high-order Runge-Kutta methods. The motivation to study these

methods came up when we faced on the numerical solution of the hyperbolic metric sector of the Fully Constrained Formulation

(FCF) of Einstein equations (Cordero-Carrin et al., 2011), which contains the gravitational radiation. These equations can

be viewed as a set of wave-like equations for the metric components. The methods have been designed in order to overcome

numerical instabilities due to the presence of stiff terms in the sources, or coming from geometrical factors due to the partic-

ular choice of (spherical-type) coordinates (as it was the case in the FCF). The application to other formulations of Einstein

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equations as BSSN in spherical coordinates will be also commented.

Domenec Espriu (Institut de Ciencies del Cosmos, Universitat de Barcelona, Barcelona, Spain)

Gravitational waves in the presence of a cosmological constant

The effects of a non-zero cosmological constant on gravitational wave propagation are discussed in the approximation of lin-

earized gravity. For Λ 6= 0 the linearization of Einstein equations is self-consistent only in certain coordinate systems. The

cosmological Friedmann-Robertson-Walker (FRW) coordinates do not belong to this class and the derived linearized solutions

have to be reinterpreted in a coordinate system that is homogeneous and isotropic to make contact with observations. Plane

waves in the linear theory acquire modifications of order√

Λ, both in the amplitude and the phase, when considered in FRW

coordinates. In a certain approximation the equations of motion can be interpreted as describing massive spin-2 particles. How-

ever, the extra degrees of freedom can be approximately gauged away, coupling to matter sources with a strength proportional

to the cosmological constant itself. Finally we discuss the viability of detecting the modifications caused by the cosmological

constant on the amplitude and phase of gravitational waves. In some cases the distortion with respect to gravitational waves

propagating in Minkowski space-time is considerable. The effect of Λ could possibly have an impact on pulsar timing arrays.

Luigi Ferraioli (APC, Paris, France)

Quantitative analysis of LISA Pathfinder test-mass noise

LISA Pathfinder mission is focussed on the low frequency region ( [0.1, 10] mHz) of the available signal spectrum. In such a

region the signal is dominated by the force noise acting on test masses. At the same time, the mission duration is limited to 90

days and typical data segments will be 24 hours in length. Considering those constraints, noise analysis (in spectral domain)

is expected to deal with a limited amount of non-Gaussian data, since the spectrum statistics will be far from Gaussian and

the lowest available frequency is limited by the data length. In this contribution, we present two noise-excess estimators that

are derived for LISA Pathfinder data analysis but that are widely applicable to different frameworks too. One is based on the

statistical properties of the integrated spectrum, the other is based on the Kolmogorov-Smirnov (KS) test. We report a test

on LPF synthetic data that is demonstrating the efficiency of the KS procedure when dealing with spectral data correlations.

The identification of noise parameters (e.g. noise amplitude) can be approached with the same procedures. In particular we

will show that both approaches provide unbiased and accurate results for noise parameter estimation and demonstrate superior

performance with respect to standard weighted least-squares and Huber’s norm.

Sara Gil Casanova (Relativity Group, Universitat de les Illes Balears, Mallorca, Spain)

Experiments on Outreach: From Press Releases to Social Networks and Computer Games

At the UIB Relativity Group we are exploring new ways of doing outreach to appeal to a wider audience, such as using com-

puter games (Space Time Quest, Black Hole Hunter) and social networks (Twitter, Facebook). In this talk I will explain our

experience with these new tools, how they complement more classic tools such as press releases, and their impact on the general

public, students and science journalists.

Michael Gabler (Universitat de Valencia, Valencia, Spain)

Magneto-elastic oscillations of magnetars

Alfven oscillations of strongly magnetized neutron stars coupled to shear modes in the solid crust could possibly explain the

quasi-periodic oscillations (QPOs) observed in the giant ares of soft gamma repeaters. I present results of two-dimensional

simulations of Alfven torsional oscillations in magnetar interiors, modeled as relativistic stars with a dipolar magnetic field.

We use a general relativistic elastomagnetohydrodynamics code in the anelastic approximation, which allows for an effective

suppression of fluid modes and an accurate description of the Alfven and shear waves. The numerical simulations show that for

magnetic fields above 5×1013 G the pure crustal oscillations are rapidly damped transferring energy to the Alfven continuum of

the core. This result is relevant for the interpretation of the observed QPOs in giant ares, since for magnetar-strength magnetic

fields, no crustal modes are expected to be present.

Filippo Galeazzi (Universitat de Valencia, Valencia, Spain)

Neutron star simulations with microphysics: issues and recipes

We present the results of 3D simulations of hot neutron stars in general relativity. We address issues and problems of using

nuclear equations of state (EOS) based on the relativistic mean field approach of G. Shen et al. (2010). We investigate the

impact on the dynamic migration of non rotating neutron stars. Neutrino emission of different species is accounted by a

simplified neutrino cooling scheme.

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Ferran Gibert (Institut de Ciencies de l’Espai (CSIC-IEEC), Bellaterra, Spain)

Modelling the Thermal Diagnostics experiments for LISA Pathfinder

A series of diagnostic experiments are planned to be carried out in the LPF (LISA Pathfinder) to remove different noise inter-

ferences in the Interferometer (IFO) signal. Amongst them, the so-called thermal diagnostics experiments must inject precise

heat loads at specific spots and measure the consequences at different points of the LTP (LPF Technology Package). Through

different thermal effects, including the radiometer effect and the radiation pressure, temperature gradients in the inertial sensor

can create noticeable forces and torques on the test masses that can disturb the IFO signal. In this presentation we report on

the current status of the models of these experiments, which are intended to be implemented in the OSE (Offline Simulation

Environment) simulator of the LPF mission. This modelling is based on different state-space blocks which are being developed

with the LTPDA Toolbox environment, which is a dedicated data analysis tool for the LTP performance.

Felipe Guzman (Albert Einstein Institute, Hannover, Germany)

Gravitational wave observatories: laser interferometry

The Laser Interferometer Space Antenna (LISA) is the concept of a gravitational wave observatory in the frequency range

of 0.1mHz-100mHz. The mission concept consists of a constellation of three spacecraft separated by 109m in an equilateral

triangle, whose center follows the Earth in a heliocentric orbit with an orbital phase offset of about 10 degrees. Challenging

technology is required to ensure pure geodetic trajectories of the six onboard test masses, whose distance fluctuations will

be measured by interspacecraft laser interferometers with picometer accuracy. Currently, ESA is conducting a downselec-

tion process for the L1 mission candidate where the New Gravitational wave Observatory (NGO), a ESA-lead mission for

gravitational wave observation. Similarly, several mission concepts have been proposed in the US for a NASA-led mission,

three of which have been chosen for further studies during 2012. An introduction to laser interferometric gravitational wave

detection, ground-based observatories, and a detailed description of the two European missions, NGO and LISA Pathfinder,

together with an overview of current investigations conducted by the community will be discussed. The current status in

development and implementation of LISA Pathfinder pre-flight systems and latest results of the ongoing ground testing efforts

will also be presented. In addition, a brief description of the US mission concepts chosen for additional studies will be presented.

Martin Hewitson (Albert Einstein Institute, Hannover,Germany)

The LISA Pathfinder mission

LISA Pathfinder (LPF) is a precursor and technology validation mission for LISA, a mission to place a Gravitational Wave

Observatory in space. Some of the key technology needed for LISA, such as micro-Newton propulsion, space-based optical

metrology, drag-free control, and inertial sensing, will be directly tested on LPF. This talk will give an overview of the overall

mission, giving the status of the various key components, a discussion on the key noise sources, and a brief introduction to the

experiments that will be carried out during mission operations.

Sascha Husa (Relativity Group, Universitat de les Illes Balears, Mallorca, Spain)

The Ninja project and surveys of the binary black hole parameter space

In this talk I will present the first paper from the Ninja-2 project, which presents a catalogue of hybrid post-Newtonian - nu-

merical relativity waveforms, and I will discuss further efforts to survey larger portions of the binary black hole parameter space.

Jose M. Ibanez (Universitat de Valencia, Val‘encia, Spain)

Current Issues in Numerical Relativistic (Magneto-)Hydrodynamics

The most spectacular events in the sky detected by current astronomical observatories (ground or space-based) involve matter

evolving in the presence of strong gravitational fields. In these astrophysical scenarios, matter can reach velocities near the

speed of light, and the gravitational field (background or generated by the flow itself) can be so strong that a description in

terms of Einsteins theory of General Relativity is necessary. Some examples of these scenarios are: the stellar core collapse (as a

mechanism of hydrodynamical supernovae), the relativistic outflows released from collapsars or from the remnants of coalescing

binary neutron stars (as a models of formation of gamma-ray bursts), the relativistic jets associated with active galactic nuclei

or microquasars, etc. To improve our knowledge of the physical nature of these energetic phenomena, modern Astrophysics is

demanding the development of robust algorithms and numerical multidimensional relativistic magnetohydrodynamical (MHD)

codes. These codes have to include the coupling to an Einstein solver. The main goal of this talk is to review the present

status of the field of Numerical Relativity extended to the inclusion of matter fields, i.e., the Numerical Relativistic MHD in

a dynamical space-time. I will summarize the present status of the efforts in numerically solving Einstein equations in the

presence of matter and I will give a general overview about some of the many astrophysical applications.

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Nathan Johnson-McDaniel (TPI Jena, Germany)

Multimessenger observations of white dwarf binaries with gravitational and electromagnetic radiation

The population of galactic white dwarf binaries is a rich source of astrophysics in the low-frequency gravitational wave band,

and a prime opportunity for multimessenger astronomy involving gravitational waves: One can combine together gravitational

wave observations with electromagnetic observations of these systems to gain information that cannot easily be accessed with

either messenger alone. For instance, one can obtain the individual masses of the stars in such a binary by combining together

gravitational wave observations with electromagnetic observations of the system’s parallax and mass function. We have as-

sessed the accuracy with which this measurement could be performed, using a population model for the galaxy’s white dwarf

binaries and assuming NGO gravitational wave measurements, Gaia parallax measurements, plus reasonably accurate (likely

ground-based) mass function measurements. We found that one can obtain at least one of the masses with an accuracy of 10s of

percent for hundreds of binaries in this case. Additionally, the higher harmonics of the gravitational radiation are measurable

for strong sources and encode information about the stars’ structure and (co)rotation; this would be a possible measurement

for advanced low-frequency gravitational wave detectors.

Nikos Karnesis (Institut de Ciencies de l’Espai (CSIC-IEEC), Bellaterra, Spain)

A Bayesian Framework for Model Selection for LISA Pathfinder

The LISA Pathfinder mission (LPF) aims to test key technologies for the future LISA mission. The LISA Technology Package

(LTP) on-board LPF, will perform a series of experiments with the aim to fully characterize all noise sources of the instrument.

The LTP Data Analysis team has developed realistic models for the LTP and parameter estimation algorithms for future

in-flight data analysis. During flight operations the team must choose between different models that describe the collected data

and between parameters that are essential for parameter estimation and characterization of the instrument. For that purpose,

a Reversible Jump Markov Chan Monte Carlo (RJMCMC) algorithm has been developed and tested with the available mod-

els and simulated experiments. The RJMCMC is a statistical tool that performs parameter estimation and chooses between

competitive models at the same time. This combination provides RJMCMC with advantages that make it applicable to a

wide range of data analysis experiments. The RJMCMC, together with other methods of model selection are discussed and

compared. All, are part of the LTPDA Matlab toolbox created by the LPF data analysis team.

Alberto Lobo (Institut de Ciencies de l’Espai (CSIC-IEEC), Bellaterra, Spain)

Latest developments in LISA PathFinder and the Munich Test

LISA PathFinder, a fundamental piece for LISA, is essentially ready for flight –were it not for a number of technical drawbacks

which have resulted in some launch delays. After a previous presentation of PathFinder in this Conference, in this talk I will

concentrate on the Spanish contribution to it, as well as review some of the most relevant results of the latest tests on the fully

integrated spacecraft, which took place in Munich in October-November last year.

Morgan Mitchell (ICFO - Institut de Ciencies Fotoniques, Castelldefels, Spain)

Quantum enhancement of interferometers and the Heisenberg limit

Quantum Metrology studies sensitivity enhancement through use of squeezed and entangled quantum states, with gravitational-

wave detection as the original motivation and to date the most advanced application. Squeezing reduces quantum noise below

the standard quantum limit δφ = 1/√N , where φ is the interferometric phase and N is the number of particles used in the

measurement. In principle, this can reach the Heisenberg limit δφ = 1/N in a linear interferometer. We recently demonstrated

sensitivity scaling as N−3/2, i.e., scaling beyond the Heisenberg limit, in a nonlinear interferometer measuring the spin of a

collection of ultra-cold atoms.

Paolo Pani (Instituto Superior Tecnico, Lisboa, Portugal)

Tidal acceleration of black holes and floating orbits in scalar-tensor theories

EMRIs are ones of the targets of future gravitational-wave detectors and they offer a unique opportunity to test General Rel-

ativity in the strong-field. We study whether generic scalar-tensor theories can be further constrained with EMRIs. We show

that in the EMRI limit, all such theories universally reduce to massive or massless Brans-Dicke theory and that black holes do

not emit dipolar radiation to all orders in post-Newtonian theory. For massive theories, superradiance can lead to resonances in

the scalar energy flux that can lead to “floating orbits” outside the innermost stable circular orbit. We interpret these orbits in

terms of tidal acceleration due to resonant polarization effects. If such floating orbits occur in the frequency band of LISA, they

would lead to a large dephasing (∼ 1e6 rads), preventing detection with GR templates. A detection that is consistent with GR

would then rule out floating resonances at frequencies lower than the lowest observed frequency, allowing for the strongest con-

straints yet on massive ST theories. Based on: Phys.Rev.Lett. 107 (2011) 241101, arXiv:1112.3351 [gr-qc] and work in progress.

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Ed Porter (APC Paris, France)

eLISA/NGO : a European detector for low frequency gravitational waves

This year, ESA will decide on the next L-class mission in the Cosmic Vision framework. Until 2011, LISA was a strong can-

didate and was to open up the gravitational wave universe in the millihertz regime. However, due to financial constraints in

the US, NASA was unable to follow the same program timescale as ESA. Therefore a decision was made to push forward with

a European space-based gravitational wave detector. In 2011, ESA carried out a CDF study, and in parallel, an international

team of scientists carried out a mission reformulation study. The result is the eLISA/NGO mission. In this presentation, I

will demonstrate the scientific potential of the mission in terms of the detection of mergers of supermassive black hole binaries,

extreme mass ratio inspirals, white dwarf galactic binaries and the possible study of some cosmological models.

Milton Ruiz (Relativity Group, Universitat de les Illes Balears, Mallorca, Spain)

Title: Magnetospheres of compact objects in Force-Free Plasma

The interaction of compact objects with magnetic fields is important for a variety of energetic phenomena.We study this in-

teraction within the force free approximation. Blandford and Znajek used this approach to show that there is a conversion of

a single black hole’s energy into electromagnetic Poynting flux. We use this, to study this interaction with neutron stars and

black holes as well.

Thomas Schwarze (Albert Einstein Institute, Hannover, Germany)

Deep phase interferometry

We present our research plan and initial results on the development of a dedicated hardware modulation system for the Deep

Modulation interferometry technique. This technique can be used to measure the test mass motion, displacement and angles

in space-based gravitational wave missions. A sinusoidal modulation is applied through a ring piezo-electric actuator to one

arm of a Mach-Zehnder interferometer in order to reach large modulation depths of the order of 10-20 rad. The interferometer

phase is extracted by a complex fit to the harmonic amplitudes of the modulation frequency. A first prototype uses the first

10 harmonic amplitudes and has demonstrated length and angular measurement sensitivities at mHz frequencies of about 20

pm/rtHz and 10 nrad/rtHz, respectively. Initial observations showed that the phase noise has a dependency on the modulation

depth. Our research focuses on the development of a digital modulation system based on Field Programmable Gate Arrays to

perform multi-frequency single-bin discrete Fourier transforms at the required harmonic amplitudes and a dedicated floating-

point microprocessor to conduct the complex fit computations for the phase extraction. A digital signal synthesizer is included

in the design and will use the fit output as input parameters for active control loops of, for example, the modulation depth,

modulation frequency, and interferometer phase state.

Alicia M. Sintes (Relativity Group, Universitat de les Illes Balears, Mallorca, Spain)

Towards Gravitational-Wave Astronomy with ground-based observatories

The ground-based world-wide network of gravitational-wave laser interferometers (LIGO, VIRGO and GEO 600) has the ambi-

tious goal of the first direct detection of gravitational waves. Their detection will provide a fundamental, new tool to probe the

universe, with information on supernovae, colliding black holes and rotating neutron stars. In this talk I will give an overview

of the status of the gravitational wave instruments, review the most significant observational results obtained so far and their

impact on our understanding of gravitational wave sources. I will also briefly outline the future steps to further increase the

reach of the instruments (such as Advanced LIGO or Einstein Telescope) which are expected to lead to the opening of a new

observational window on the universe in the coming years.

Carlos F. Sopuerta (Institut de Ciencies de l’Espai (CSIC-IEEC), Bellaterra, Spain)

On the modeling of Intermediate- and Extreme-Mass-Ratio Inspirals

The existence of Intermediate-Mass Black Holes (IMBHs; 100 to 10000 solar masses) is still uncertain but there is accumulating

observational evidence that these objects are present in some globular clusters. IMBHs are objects that can generate gravita-

tional wave events of interest for the upcoming detectors. The inspiral of a compact stellar-mass object (1− 50 solar masses)

into an IMBH in the case of advanced ground detectors, and the inspiral of an IMBH into a supermasive BH (105 − 107 solar

masses) in the case of space detectors like eLISA would be strong events, usually known as Intermediate-Mass-Ratio Inspirals

(IMRIs). On the other hand, the inspiral of a compact stellar object into a SMBH is an important event for space detectors like

eLISA, usually known as Extreme-Mass-Ratio Inspirals (EMRIs). To build waveform templates for these systems, and due to

the mass ratios involved, we cannot resort to full numerical relativity but instead to complement it with the use of perturbative

techniques. In this talk, I will review the status of the modeling of IMRIs and EMRIs, describe the details of the current main

techniques, and I will also comment on the prospects for the near future.

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Ulrich Sperhake (Institut de Ciencies de l’Espai (CSIC-IEEC), Bellaterra, Spain)

Black-hole binary simulations on supercomouters

Following the breakthroughs of 2005, the field of numerical relativity has generated a wealth of insight into the dynamics of

black-hole binary systems. We review the current status of numerical relativity and the latest predictions about black holes in

astrophysical systems and as sources of gravitational waves for LIGO, VIRGO, GEO600 and spacebase interferometer. We also

briefly discuss the role of black holes in the context of high-energy physics and future opportunities for numerical relativity to

deepen our insight at this interface.

Stephen Taylor (Institute of Astronomy, University of Cambridge, UK)

Hubble Without The Hubble: Cosmology Using Advanced GW Detectors Alone

The Advanced LIGO gravitational wave detector is due to come online in 2015 and will be able to detect inspiraling double-

neutron-star binaries out to ∼ 200 Mpc, an improvement from the ∼ 15 Mpc achievable with initial LIGO. Incorporating

AdLIGO into a global network will boost the directional sensitivity and permit source distance determination. Previous pro-

posals for constraining cosmology with GW’s have relied on the detection of an electromagnetic counterpart to the GW-event

to provide the source redshift. However, we find that it is possible to constrain the Hubble constant and the parameters of the

NS mass function using gravitational-wave data alone. This novel method exploits the narrowness of the NS mass distribution

to extract candidate redshift distributions from the GW-measured redshifted chirp mass. We find that we may be able to

determine the Hubble constant to ±10% using ∼ 100 observations, provided the half-width of the underlying double NS mass

distribution is less than 0.04 solar masses. The expected precision depends linearly on the intrinsic width of the NS mass

function. Although the horizon distance of second-generation detectors will not be large enough to put constraints on other

cosmological parameters, we will also discuss preliminary results for a similar study with the the proposed third-generation

Einstein Telescope.

Christian Trenkel (Astrium Ltd, UK)

Testing Modified Newtonian Dynamics with LISA Pathfinder

It has now been known for almost 80 years that the observed galactic rotation curves cannot be explained assuming just the

visible mass and our standard theory of gravitation. Despite concentrated efforts, the direct search for Dark Matter particles

remains largely fruitless, and various proposals to modify the laws of gravitation have been put forward over the last decades.

The difficulty with these proposals is that almost by definition, significant deviations from standard gravitation only manifest

themselves outside the Solar System, and are therefore beyond the reach of direct experimentation. However, it turns out

that at least one such proposal, based on Modified Newtonian Dynamics, should have measureable effects around gravitational

saddle points inside the Solar System. It has been subsequently pointed out that LISA Pathfinder, a joint ESA/NASA mission

with a launch date only a few years away, could in principle be used as built ie without requiring any modifications to the

hardware or nominal mission to subject this particular theory to a relatively stringent controlled experimental test, at a very

modest additional cost. This talk discusses the feasibility and significance of such a direct test.

List of Participants

1. Pau Amaro-Seoane (Albert Einstein Institute, Golm, Germany) <[email protected]>

2. Mar Bastero Gil (Universidad de Granada, Granada, Spain) <[email protected]>

3. Sebastiano Bernuzzi (TPI Jena, Jena, Germany) <[email protected]>

4. Christopher Berry (Institute of Astronomy, University of Cambridge, UK) <[email protected]>

5. Patrick Brem (ARI, University of Heidelberg, Germany) <[email protected]>

6. Priscil·la Canizares (Institute of Astronomy, University of Cambridge, UK) <[email protected]>

7. Isabel Cordero-Carrion (Max Planck Institute for Astrophysics, Garching, Germany) <[email protected]>

8. Marc Dıaz Aguilo (Institut d’Estudis Espacials de Catalunya (IEEC), Spain) <[email protected]>

9. Domenec Espriu (ICC, Universitat de Barcelona, Barcelona, Spain) <[email protected]>

10. Luigi Ferraioli (APC Paris, France) <[email protected]>

ICE (CSIC-IEEC)


11. Jose A. Font (Universitat de Valencia, Valencia, Spain) <[email protected]>

12. Ryuichi Fujita (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

13. Michael Gabler (Universitat de Valencia, Valencia, Spain) <[email protected]>

14. Filippo Galeazzi (Universitat de Valencia, Valencia, Spain) <[email protected]>

15. Lluıs Gesa Bote (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

16. Alberto Gianolio (ESA, Noordwijk, The Netherlands) <[email protected]>

17. Ferran Gibert (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

18. Sara Gil-Casanova (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

19. Felipe Guzman Cervantes (Albert Einstein Institute Hannover, Germany) <[email protected]>

20. Martin Hewitson (Albert Einstein Institute, Hannover, Germany) <[email protected]>

21. Sascha Husa (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

22. Jose M. Ibanez (Universitat de Valencia, Valencia, Spain) <[email protected]>

23. Oliver Jennrich (ESA, Noordwijk, The Netherlands) <[email protected]>

24. Jose Antonio Jimenez Madrid (ICM (CSIC), Spain) <[email protected]>

25. Nathan Johnson-McDaniel (TPI Jena, Jena, Germany) <[email protected]>

26. Nikos Karnesis (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

27. Mehmet Kavuk (Bogazici University, Turkey) <[email protected]>

28. Andrzej Krolak (Institute of Mathematics, Polish Academy of Sciences, Poland) <[email protected]>

29. Janna Levin (Barnard College/Columbia University, USA) <[email protected]>

30. Ivan Lloro (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

31. Alberto Lobo (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

32. Victor Martın (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

33. Ignacio Mateos (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

34. Morgan Mitchell (ICFO - Institut de Ciencies Fotoniques, Castelldefels, Spain) <[email protected]>

35. Miquel Nofrarias (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

36. Paolo Pani (Instituto Superior Tecnico - Lisbon, Portugal) <[email protected]>

37. Eric Plagnol (APC Paris, France) <[email protected]>

38. Ed Porter (APC Paris, France) <[email protected]>

39. Juan Ramos (Universitat Politecnica de Catalunya, Spain) <[email protected]>

40. Milton Ruiz (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

41. Thomas Schwarze (Albert Einstein Institute, Hannover, Germany) <[email protected]>

42. Alicia M. Sintes (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

43. Carlos F. Sopuerta (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

44. Ulrich Sperhake (Institut de Ciencies de l’Espai (CSIC-IEEC), Spain) <[email protected]>

45. Stephen Taylor (Institute of Astronomy, University of Cambridge, UK) <[email protected]>

46. Christian Trenkel (Astrium Ltd, Stevenage, UK) <[email protected]>

47. Alex Vano Vinuales (Universitat de les Illes Balears, Mallorca, Spain) <[email protected]>

48. Ivan Zhogin (ISSCM SB RAS, Russia) <[email protected]>

ICE (CSIC-IEEC)

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