The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on ‘Black holes, Gravitational waves and Fundamental Physics’.

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1 The final equations provided age-, height-, sex-, and ethnic-specific predicted values and lower limits of normal for spirometry. The predicted equations for Caucasians were derived from 55 428 individuals and represent the largest 'all-age' spirometry reference values published to date. The methodological approach used by the Task Force is identical to that previously used to develop the Stanojevic et al. 'all-age' spirometry reference equations for Caucasians, 2 which we have recently shown to be appropriate for contemporary Australasian subjects. 3 The aim of this analysis was to ascertain how well the new European Respiratory Society GLI 2012 reference ranges fit contemporary Australasian spirometric data. Spirometry outcomes from 2066 Caucasian subjects aged 4-80 years (55% male) collected from 14 centres across Australia and New Zealand were included.3 Height-, age-and gender-specific Z-scores for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flows between 25% and 75% of FVC (FEF25-75) and FEV1/FVC were calculated for GLI 2012 equations using custom-made software. 4 We defined the minimum physiologically relevant difference to be 0.5 Z-scores, equating to a difference of~6% predicted.Mean (SD) Z-scores for the contemporary Australasian data were 0.23 (1.00) for FEV1, 0.23 (1.00) for FVC, -0.03 (0.87) for FEV1/FVC and 0.07 (0.95) for FEF25-75, all of which were well within range considered to be physiologically irrelevant. The mean Z-score differences equated to absolute and percent predicted differences of 89 mL and 3%, respectively, for FEV1, 117 mL and 3.2% for FVC, 127 mL/s, and 5.9% for FEF25-75 and a difference in FEV1/FVC of -0.49%. Although there were some weak, albeit statistically significant, associations between the spirometry Z-scores and age, height and sex or a combination of

Spirometry from contemporary Australasian healthy subjects fits the all-age reference ranges well. While the current study supports the use of the all-age reference ranges, the between-centre differences highlight the need for spirometry to be used in conjunction with other clinical findings.

We suggest that nonminimally coupled scalar fields can lead to modifications of the microphysics in the interiors of relativistic stars. As a concrete example, we consider the generation of a non-zero photon mass in such high-density environments. This is achieved by means of a light gravitational scalar, and the scalarization phase transition in scalar-tensor theories of gravitation. Two distinct models are presented, and phenomenological implications are briefly discussed.PACS numbers: 04.50. Kd,04.40.Dg Scalar-tensor theories [1][2][3][4] can be thought of as theories of gravity with an additional scalar field Φ that couples non minimally to the metricg µν but does not couple to the matter fields, Ψ A . The latter couple minimally tog µν only. In this representation, known as the Jordan frame, the action readsand the weak equivalence principle (WEP) is manifest. Here Φ has the interpretation of a varying inverse gravitational constant, S m denotes the matter action, andR is the Ricci scalar ofg µν . One can also reformulate this action in terms of another metric and a redefined scalar field, in the so called Einstein frame. The scalar field and the metric in this frame are related to their Jordan frame counterparts by,where G ⋆ is a bare gravitational constant. The form of A 2 (φ) is determined by the choice of ω(Φ) and the requirement that the kinetic term for φ be canonical. That is, the Einstein frame action readswhere R is the Ricci scalar of g µν . In the absence of matter the theory clearly reduces to general relativity (GR) with a minimally coupled scalar field. In this representation the deviation from GR is encoded in the nonmiminal coupling between the matter and φ. After some manipulations the field equation for the scalar field can be put into the form [1][2][3][4][5] where T is the trace of the Einstein frame stress-energy tensorTheories in which dA(φ 0 )/dφ = 0 for some constant φ 0 , admit GR solutions with a trivial scalar configuration, as the scalar's equation is trivially satisfied and g µν effectively satisfies Einstein's equation with a rescaled gravitational coupling. Note that such theories have ω(Φ 0 ) → ∞ in the Jordan frame, where Φ 0 ≡ Φ(φ 0 ) (see Ref.[6] for a more detailed discussion). Certain theories in this class exhibit a remarkable property dubbed spontaneous scalarization [4,5,7]. It is convenient to expand the logarithmic derivative of the conformal factor around φ = φ 0 asIn and around stars of relatively low densities, such as the Sun, the scalar remains at the trivial configuration, φ = φ 0 , and the metric is that of GR. As a result the theory is indistinguishable from GR in the weak field limit. However, for β 0 < ∼ −4, compact stars above a threshold central density undergo a phase transition and develop a large scalar charge, even in the absence of an external scalar environment [5]. This behaviour is of particular interest as it underscores the importance of constraining deviation from GR in the strong field regime.At the perturbative level spontaneous scalariza...