Asymptotically flat black holes sourced by a massless scalar field

We derive exact, asymptotically flat black hole solutions of Einstein-scalar gravity sourced by a non trivial scalar field with $1/r$ asymptotic behaviour. They are determined using an ansatz for the scalar field profile and working out, together with the metric functions, the corresponding form of the scalar self-interaction potential. Near to the singularity the black hole behaves as the Janis-Newmann-Winicour-Wyman solution. We also work out a consistent thermodynamical description of our black hole solutions. For large mass our hairy black holes have the same thermodynamical behaviour of the Schwarzschild black hole, whereas for small masses they differ substantially from the latter.Comment: 12 pages, no figures. Refs. [27-33] added. Some remarks about previous derivation and stability of solution (5.4) adde

Is the gravitational-wave ringdown a probe of the event horizon?

It is commonly believed that the ringdown signal from a binary coalescence provides a conclusive proof for the formation of an event horizon after the merger. This expectation is based on the assumption that the ringdown waveform at intermediate times is dominated by the quasinormal modes of the final object. We point out that this assumption should be taken with great care, and that very compact objects with a light ring will display a similar ringdown stage, even when their quasinormal-mode spectrum is completely different from that of a black hole. In other words, universal ringdown waveforms indicate the presence of light rings, rather than of horizons. Only precision observations of the late-time ringdown signal, where the differences in the quasinormal-mode spectrum eventually show up, can be used to rule out exotic alternatives to black holes and to test quantum effects at the horizon scale.Comment: 6 pages, 4 figures. Version published as Editors' Suggestion in Physical Review Letters. v4: includes Erratum correcting the caption of Fig.4. All conclusions remain unchange

Testing strong gravity with gravitational waves and Love numbers

The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects

Testing strong-field gravity with tidal Love numbers

The tidal Love numbers (TLNs) encode the deformability of a self-gravitating object immersed in a tidal environment and depend significantly both on the object's internal structure and on the dynamics of the gravitational field. An intriguing result in classical general relativity is the vanishing of the TLNs of black holes. We extend this result in three ways, aiming at testing the nature of compact objects: (i) we compute the TLNs of exotic compact objects, including different families of boson stars, gravastars, wormholes, and other toy models for quantum corrections at the horizon scale. In the black-hole limit, we find a universal logarithmic dependence of the TLNs on the location of the surface; (ii) we compute the TLNs of black holes beyond vacuum general relativity, including Einstein-Maxwell, Brans-Dicke and Chern-Simons gravity; (iii) We assess the ability of present and future gravitational-wave detectors to measure the TLNs of these objects, including the first analysis of TLNs with LISA. Both LIGO, ET and LISA can impose interesting constraints on boson stars, while LISA is able to probe even extremely compact objects. We argue that the TLNs provide a smoking gun of new physics at the horizon scale, and that future gravitational-wave measurements of the TLNs in a binary inspiral provide a novel way to test black holes and general relativity in the strong-field regime.Comment: 18 pages + appendices; 9 figures. v2: references updated and legend of Fig.7 corrected; v3: clarifications and improvements in the discussion; v4: minor changes to match the PRD version (selected as Editors' Suggestion

Regional Development and the Indicators for Mapping of Local Productive Arrangements of Rondônia (Brazil)

This is a documental research, whose main objective is to present indicators for a new mapping of Local Productive Arrangements (APLs) in Rondonia and, specifically, discuss the dynamics of reference data and its importance to the investment policies with a view to regional development. he data were calculated from tables of the Annual List of Social Informations (RAIS, 2012), presented by the Regional Secretariat of the Ministry of Labor and Employment (MTE) (BRAZIL, 2014), and by census of vegetal extraction, agriculture and sylviculture available on the IBGE website, relative to 2013. It was observed that most of the APLs identified in previous studies have not been confirmed by the data of the RAIS and of the IBGE. From these data, we identified more than 100 potential APLs in the State, while are currently presented only 18. The cattle breeding, for example, appears in the previous studies restricted to a microregion only, but it is significant in seven of the eight microregions of the State. Are also quite significant the production data of fruit and fish, among other products, confirming a diversified economy in the agricultural sector; in the secondary sector, however, there are few references, most notably in larger businesses involving wood, civil construction, and strictly in Porto Velho, electricity. It is suggested to be made larger investments for APLs studies in the State, including for full mapping not only per Microregion, but also by the city, in order to identify best opportunities, fill the gaps, offer support and strengthen the endeavors. There is much that can be allocated as resource in the Multi-Annual Plans of State

First steps to define murine amniotic fluid stem cell microenvironment

Stem cell niche refers to the microenvironment where stem cells reside in living organisms. Several elements define the niche and regulate stem cell characteristics, such as stromal support cells, gap junctions, soluble factors, extracellular matrix proteins, blood vessels and neural inputs. In the last years, different studies demonstrated the presence of cKit+ cells in human and murine amniotic fluid, which have been defined as amniotic fluid stem (AFS) cells. Firstly, we characterized the murine cKit+ cells present both in the amniotic fluid and in the amnion. Secondly, to analyze the AFS cell microenvironment, we injected murine YFP+ embryonic stem cells (ESC) into the amniotic fluid of E13.5 wild type embryos. Four days after transplantation we found that YFP+ sorted cells maintained the expression of pluripotency markers and that ESC adherent to the amnion were more similar to original ESC in respect to those isolated from the amniotic fluid. Moreover, cytokines evaluation and oxygen concentration analysis revealed in this microenvironment the presence of factors that are considered key regulators in stem cell niches. This is the first indication that AFS cells reside in a microenvironment that possess specific characteristics able to maintain stemness of resident and exogenous stem cells

Isolation and Expansion of Muscle Precursor Cells from Human Skeletal Muscle Biopsies

One of the major issues concerning human skeletal muscle progenitor cells is represented by the efficient isolation and in vitro expansion of cells retaining the ability to proliferate, migrate and differentiate once transplanted. Here we describe a method (1) effective in obtaining human muscle precursor cells both from fresh and frozen biopsies coming from different muscles, (2) selective to yield cells uniformly positive for CD56 and negative for CD34 without FACS sorting, (3) reliable in maintaining proliferative and in vitro differentiative capacity up to passage 10