Impact of Numerical Relativity information on effective-one-body waveform models

We present a comprehensive comparison of the spin-aligned effective-one-body (EOB) waveform model of Nagar et al. [Phys. Rev. D93, 044046 (2016)], informed using 40 numerical-relativity (NR) datasets, against a set of 149, $\ell=m=2$, NR waveforms freely available through the Simulation Extreme Spacetime (SXS) catalog. We find that, without further calibration, these EOBNR waveforms have unfaithfulness (at design Advanced-LIGO sensitivity and evaluated with total mass $M$ varying as $10M_\odot\leq M \leq 200M_\odot$) always below $1\%$ against all NR waveforms except for three outliers, that still never exceed the $3\%$ level; with a minimal retuning of the (effective) next-to-next-to-next-to-leading-order spin-orbit coupling parameter for the non-equal-mass and non-equal-spin sector, that only needs three more NR waveforms, one is left with another two (though different) outliers, with maximal unfaithfulness of up to only $2\%$ for a total mass of $200M_\odot$. We show this is the effect of slight inaccuracies in the phenomenological description of the postmerger waveform of Del Pozzo and Nagar [arXiv:1606.03952] that was constructed by interpolating over only 40NR simulations. We argue that this is easily fixed by using either an alternative ringdown description (e.g., the superposition of quasi-normal-modes) or an improved version of the phenomenological representation. By analyzing a NR waveform with mass ratio $8$ and dimensionless spins $+0.85$ obtained with the BAM code, we conclude that the model would benefit from NR simulations specifically targeted at improving the postmerger-ringdown phenomenological fits for mass ratios $\gtrsim 8$ and spins $\gtrsim 0.8$.Comment: 24 pages, 20 figures, submitted to Phys. Rev.

Gravitational-Wave Asteroseismology with Fundamental Modes from Compact Binary Inspirals

The first detection of gravitational waves (GWs) from the binary neutron star (NS) inspiral GW170817 has opened a unique channel for probing the fundamental properties of matter at supra-nuclear densities inaccessible elsewhere in the Universe. This observation yielded the first constraints on the equation of state (EoS) of NS matter from the GW imprint of tidal interactions. Tidal signatures in the GW arise from the response of a matter object to the spacetime curvature sourced by its binary companion. They crucially depend on the EoS and are predominantly characterised by the tidal deformability parameters $\Lambda_{\ell}$, where $\ell=2,3$ denotes the quadrupole and octupole respectively. As the binary evolves towards merger, additional dynamical tidal effects become important when the orbital frequency approaches a resonance with the stars' internal oscillation modes. Among these modes, the fundamental ($f_\ell$-)modes have the strongest tidal coupling and can give rise to a cumulative imprint in the GW signal even if the resonance is not fully excited. Here we present the first direct constraints on fundamental oscillation mode frequencies for GW170817 using an inspiral GW phase model with an explicit dependence on the $f$-mode frequency and without assuming any relation between $f_\ell$ and $\Lambda_\ell$. We rule out anomalously small values of $f_\ell$ and, for the larger companion, determine a lower bound on the $f_2$-mode ($f_3$-mode) frequency of $\geq 1.39$ kHz ($\geq 1.86$ kHz) at the 90\% credible interval (CI). We then show that networks of future GW detectors will be able to measure $f$-mode frequencies to within tens of Hz from the inspiral alone. Such precision astroseismology will enable novel tests of fundamental physics and the nature of compact binaries.Comment: 8 pages, 5 figure

Reconstructing the Thermal Sunyaev-Zel'dovich Effect in 3D

The thermal Sunyaev-Zel'dovich (tSZ) effect measures the line-of-sight projection of the thermal pressure of free electrons and lacks any redshift information. By cross correlating the tSZ effect with an external cosmological tracer we can recover a good fraction of this lost information. Weak lensing (WL) is thought to provide an unbiased probe of the dark Universe, with many WL surveys having sky coverage that overlaps with tSZ surveys. Generalising the tomographic approach, we advocate the use of the spherical Fourier-Bessel (sFB) expansion to perform an analysis of the cross-correlation between the projected (2D) tSZ Compton $y$-parameter maps and 3D weak lensing convergence maps. We use redshift dependent linear biasing and the halo model as a tool to investigate the tSZ-WL cross-correlations in 3D. We use the Press-Schechter (PS) and the Sheth-Tormen (ST) mass-functions in our calculations, finding that the results are quite sensitive to detailed modelling. We provide detailed analysis of surveys with photometric and spectroscopic redshifts. The signal-to-noise (S/N) of the cross-spectra $\mathcal{C}_{\ell} (k)$ for individual 3D modes, defined by the radial and tangential wave numbers $(k;\ell)$, remains comparable to, but below, unity though optimal binning is expected to improve this. The results presented can be generalised to analyse other CMB secondaries, such as the kinetic Sunyaev-Zel'dovich (kSZ) effect.Comment: 27 pages, 12 Figures. Published in MNRA

A Multipolar Effective One Body Model for Non-Spinning Black Hole Binaries

We introduce \TEOBiResumSM{}, a nonspinning inspiral-merger-ringdown waveform model built within the effective one body (EOB) framework that includes gravitational waveform modes beyond the dominant quadrupole $(\ell,|m|) = (2,2)$. The model incorporates: (i) an improved Pad\'e resummation of the factorized waveform amplitudes $\rho_{\ell m}^{\rm orb}$ entering the EOB-resummed waveform where the 3PN, mass-ratio dependent, terms are hybridized with test-mass limit terms up to 6PN relative order for most of the multipoles up to $\ell=6$ included; (ii) an improved determination of the effective 5PN function $a_6^c(\nu)$ entering the EOB interaction potential done using the most recent, error-controlled, nonspinning numerical relativity (NR) waveforms from the Simulating eXtreme Spacetimes (SXS) collaboration; and (iii) a NR-informed phenomenological description of the multipolar ringdown. Such representation stems from 19 NR waveforms with mass ratios up to $m_1/m_2=18$ as well as test-mass waveform data, although it does not incorporate mode-mixing effects. The NR-completed higher modes through merger and ringdown considered here are: $(\ell,|m|) = \lbrace (2,1), (3,3), (3,2),(3,1),(4,4), (4,3),(4,2), (4,1),(5,5)\rbrace$. For simplicity, the other subdominant modes, up to $\ell=8$, are approximated by the corresponding, purely analytical, factorized and resummed EOB waveform. To attempt an estimate of (some of) the underlying analytic uncertainties of the model, we also contrast the effect of the 6PN-hybrid Pad\'e-resummed $\rho_{\ell m}$'s with the standard $3^{+2}$PN, Taylor-expanded, ones used in previous EOB works. The maximum unfaithfulness $\bar{F}$ against the SXS waveforms including all NR-completed modes up to $\ell=m=5$ is always $\lesssim 2\%$ for binaries with total mass $M$ as $50 M_{\odot} \leq M \lesssim 200 M_{\odot}$.Comment: 24 pages, 18 figures. Improved figures and presentation. Submitted to Phys. Rev.

Validity of common modelling approximations for precessing binary black holes with higher-order modes

The current paradigm for constructing waveforms from precessing compact binaries is to first construct a waveform in a non-inertial, co-precessing binary source frame followed by a time-dependent rotation to map back to the physical, inertial frame. A key insight in the construction of these models is that the co-precessing waveform can be effectively mapped to some equivalent aligned spin waveform. Secondly, the time-dependent rotation implicitly introduces $m$-mode mixing, necessitating an accurate description of higher-order modes in the co-precessing frame. We assess the efficacy of this modelling strategy in the strong field regime using Numerical Relativity simulations. We find that this framework allows for the highly accurate construction of $(2,\pm 2)$ modes in our data set, while for higher order modes, especially the $(2,|1|), (3,|2|)$ and $(4,|3|)$ modes, we find rather large mismatches. We also investigate a variant of the approximate map between co-precessing and aligned spin waveforms, where we only identify the slowly varying part of the time domain co-precessing waveforms with the aligned-spin one, but find no significant improvement. Our results indicate that the simple paradigm to construct precessing waveforms does not provide an accurate description of higher order modes in the strong-field regime, and demonstrate the necessity for modelling mode asymmetries and mode-mixing to significantly improve the description of precessing higher order modes.Comment: Improved version: correcting typos, adding acknowledgement and more reference

Collective Employee Representation and the Impact of Law: Initial Response to the Employment Relations Act 1999.

Using data gathered primarily during interviews with managers and trade union officials, this article examines how trade unions and employers have reacted to the introduction of the statutory procedure for union recognition in the Employment Relations Act 1999 (ERA). Findings indicate that the ERA and the drift of EU influence have had a substantial effect in shifting the balance of employer attitudes towards greater approval of trade unions and have accelerated the rate at which employers are redesigning their relationships with unions. Although employers are tending to restrict unions' influence over traditional issues such as pay-setting, they are increasingly seeking their assistance in implementing difficult organisational changes. The article explores the impact of such changes on trade union activity and collective representation more broadly.Collective bargaining, employee representation, trade union recognition labour legislation

Exhaustion and Technological Development: a macro-dynamic policy model

The main components of the problem complex posed by the Club of Rome are what the joint effect will be, and how it can be influenced, of (i) population growth, (ii) increase of pollution, (iii) the exhaustion of material resources and (iv) technological development. From the discussions of the last few years my main impressions are that policies to curb population growth and pollution are within reach, even though formidable obstacles will have to be faced. Put in oversimplified terms, the population explosion begins to be seen by a rapidly increasing number of people as a danger; various means to put a break on it have been developed and there is a group of countries where the effect of their use begins to be visible. Also a number of expert calculations on the means needed to keep pollution under control suggest that these are of the order of 4 per cent of national income for some developed countries; a figure not too deconcerting. The author is indebted to Professors O. Rademaker and H. Linnemann for helpful comments on an earlier draft of this article. Of course the responsibility for the present text is mine

Reciprocal Learning: An Intergenerational Computer Training Model for Young Adults Working with Elders Follow-Up Evaluation: Summer 2006 - Report Series # 15

The goal of this evaluation, conducted in the summer of 2006, was to capture the experiences of young adults who participated as ‘senior tech tutors’ for elders in the computer training program. The training was piloted in the Internet Café at the Sheridan Elder Research Centre (SERC) in the fall of 2005. Twelve young adults participated in the training to become ‘senior tech tutors. An additional three participated in tutoring without having attended the training but were provided with instructional hand-outs. These three tech tutors had prior education and experience in the field of gerontology. Feedback interviews were conducted over the telephone. These interviews took place over an eight-week period. The relationships that tech tutors formed with their ‘student’ elders had an impact on tech tutors’ goals, their views about aging and their career aspirations

Galaxy clustering in 3D and modified gravity theories

We study Modified Gravity (MG) theories by modelling the redshifted matter power spectrum in a spherical Fourier-Bessel (sFB) basis. We use a fully non-linear description of the real-space matter power-spectrum and include the lowest-order redshift-space correction (Kaiser effect), taking into account some additional non-linear contributions. Ignoring relativistic corrections, which are not expected to play an important role for a shallow survey, we analyse two different modified gravity scenarios, namely the generalised Dilaton scalar-tensor theories and the f(R) models in the large curvature regime. We compute the 3D power spectrum C s ℓ (k 1 ,k 2 ) for various such MG theories with and without redshift space distortions, assuming precise knowledge of background cosmological parameters. Using an all-sky spectroscopic survey with Gaussian selection function φ(r)∝exp(−r 2 /r 2 0 ) , r 0 =150h −1 Mpc , and number density of galaxies N ¯ =10 −4 Mpc −3 , we use a χ 2 analysis, and find that the lower-order (ℓ≤25) multipoles of C s ℓ (k,k ′ ) (with radial modes restricted to k25 modes can further reduce the error bars and thus in principle make cosmological gravity constraints competitive with solar system tests. However this will require an accurate modelling of non-linear redshift space distortions. Using a tomographic β(a) -m(a) parameterization we also derive constraints on specific parameters describing the Dilaton models of modified gravity

Chef image's influence on tourists' dining experiences

Highlights • Tourists’ teppanyaki restaurant dining experience is examined. • A chef’s image has a positive influence on experiential value. • Interaction with other customers positively influences experiential value. • Service quality has a positive influence on diners’ experiential value