The importance of precession in modelling the direction of the final spin from a black-hole merger

The prediction of the spin of the black hole resulting from the merger of a generic black-hole binary system is of great importance to study the cosmological evolution of supermassive black holes. Several attempts have been recently made to model the spin via simple expressions exploiting the results of numerical-relativity simulations. Here, I first review the derivation of a formula, proposed in Barausse & Rezzolla, Apj 704 L40, which accurately predicts the final spin magnitude and direction when applied to binaries with separations of hundred or thousands of gravitational radii. This makes my formula particularly suitable for cosmological merger-trees and N-body simulations, which provide the spins and angular momentum of the two black holes when their separation is of thousands of gravitational radii. More importantly, I investigate the physical reason behind the good agreement between my formula and numerical relativity simulations, and nail it down to the fact that my formula takes into account the post-Newtonian precession of the spins and angular momentum in a consistent manner.Comment: 6 pages, 2 figures. Panel added to fig 2, discussion extended to comply with referee's comments. Version accepted for publication as proceeding of the 8th Amaldi International Conference on Gravitational Waves, NYC, 21-26 June 200

Hamiltonian of a spinning test-particle in curved spacetime [Erratum: Phys. Rev. D 80, 104025 (2009)]

Using a Legendre transformation, we compute the unconstrained Hamiltonian of a spinning test-particle in a curved spacetime at linear order in the particle spin. The equations of motion of this unconstrained Hamiltonian coincide with the Mathisson-Papapetrou-Pirani equations. We then use the formalism of Dirac brackets to derive the constrained Hamiltonian and the corresponding phase-space algebra in the Newton-Wigner spin supplementary condition (SSC), suitably generalized to curved spacetime, and find that the phase-space algebra (q,p,S) is canonical at linear order in the particle spin. We provide explicit expressions for this Hamiltonian in a spherically symmetric spacetime, both in isotropic and spherical coordinates, and in the Kerr spacetime in Boyer-Lindquist coordinates. Furthermore, we find that our Hamiltonian, when expanded in Post-Newtonian (PN) orders, agrees with the Arnowitt-Deser-Misner (ADM) canonical Hamiltonian computed in PN theory in the test-particle limit. Notably, we recover the known spin-orbit couplings through 2.5PN order and the spin-spin couplings of type S_Kerr S (and S_Kerr^2) through 3PN order, S_Kerr being the spin of the Kerr spacetime. Our method allows one to compute the PN Hamiltonian at any order, in the test-particle limit and at linear order in the particle spin. As an application we compute it at 3.5PN order

Two phase galaxy formation: The Evolutionary Properties of Galaxies

We use our model for the formation and evolution of galaxies within a two-phase galaxy formation scenario, showing that the high-redshift domain typically supports the growth of spheroidal systems, whereas at low redshifts the predominant baryonic growth mechanism is quiescent and may therefore support the growth of a disc structure. Under this framework we investigate the evolving galaxy population by comparing key observations at both low and high-redshifts, finding generally good agreement. By analysing the evolutionary properties of this model, we are able to recreate several features of the evolving galaxy population with redshift, naturally reproducing number counts of massive star-forming galaxies at high redshifts, along with the galaxy scaling relations, star formation rate density and evolution of the stellar mass function. Building upon these encouraging agreements, we make model predictions that can be tested by future observations. In particular, we present the expected evolution to z=2 of the super-massive black hole mass function, and we show that the gas fraction in galaxies should decrease with increasing redshift in a mass, with more and more evolution going to higher and higher masses. Also, the characteristic transition mass from disc to bulge dominated system should decrease with increasing redshift.Comment: 15 pages, 11 figures. Version polished for publication in MNRA

AN INTEGRATED APPROACH TO PREVENT THE EROSION OF SALT MARSHES IN THE LAGOON OF VENICE

The loss of coastal habitats is a widespread problem in Europe. To protect the intertidal salt marshes of the lagoon of Venice from the erosion due to natural and human causes which is diffusely and intensely impacting them, the European Commission has funded the demonstrative project LIFE VIMINE. LIFE VIMINE aims to protect the most interior, hard-to-access salt marshes in the northern lagoon of Venice through an integrated approach, whose core is the prevention of erosion through numerous, small but spatially-diffuse soil-bioengineering protections works, mainly placed through semi-manual labour and with low impact on the environment and the landscape. The effectiveness of protection works in the long term is ensured through routine, temporally-continuous and spatially-diffuse actions of monitoring and maintenance. This method contrasts the common approach to managing hydraulic risk and erosion in Italy which is based on large, one-off and irreversible protection actions. The sustainability of the LIFE VIMINE approach is ensured by the participatory involvement of stakeholders and the recognition that protecting salt marshes means defending the benefits they provide to society through their ecological functions, as well as protecting the jobs linked to the existence or conservation of this habitat

Non-singular Universes a la Palatini

It has recently been shown that f(R) theories formulated in the Palatini variational formalism are able to avoid the big bang singularity yielding instead a bouncing solution. The mechanism responsible for this behavior is similar to that observed in the effective dynamics of loop quantum cosmology and an f(R) theory exactly reproducing that dynamics has been found. I will show here that considering more general actions, with quadratic contributions of the Ricci tensor, results in a much richer phenomenology that yields bouncing solutions even in anisotropic (Bianchi I) scenarios. Some implications of these results are discussed.Comment: 4 pages, no figures. Contribution to the Spanish Relativity Meeting (ERE2010), 6-10 Sept. Granada, Spai

Post-Newtonian expansion for Gauss-Bonnet Gravity

The Parametrized Post-Newtonian expansion of gravitational theories with a scalar field coupled to the Gauss-Bonnet invariant is performed and confrontation of such theories with Solar system experiments is discussed.Comment: 4 pages; typos corrected, published versio

Neutron star sensitivities in Ho\u159ava gravity after GW170817

Horava gravity breaks boost invariance in the gravitational sector by introducing a preferred time foliation. The dynamics of this preferred slicing is governed, in the low-energy limit suitable for most astrophysical applications, by three dimensionless parameters $alpha$, $eta$ and $lambda$. The first two of these parameters are tightly bound by solar system and gravitational wave propagation experiments, but $lambda$ remains relatively unconstrained ($0leqlambdalesssim 0.01-0.1$). We restrict here to the parameter space region defined by $alpha=eta=0$ (with $lambda$ kept generic), which in a previous paper we showed to be the only one where black hole solutions are non-pathological at the universal horizon, and we focus on possible violations of the strong equivalence principle in systems involving neutron stars. We compute neutron star 'sensitivities', which parametrize violations of the strong equivalence principle at the leading post-Newtonian order, and find that they vanish identically, like in the black hole case, for $alpha=eta=0$ and generic $lambda eq0$. This implies that no violations of the strong equivalence principle (neither in the conservative sector nor in gravitational wave fluxes) can occur at the leading post-Newtonian order in binaries of compact objects, and that data from binary pulsars and gravitational interferometers are unlikely to further constrain $lambda$

Extreme Mass-Ratio Inspirals in the Effective-One-Body Approach: Quasi-Circular, Equatorial Orbits around a Spinning Black Hole

We construct effective-one-body waveform models suitable for data analysis with LISA for extreme-mass ratio inspirals in quasi-circular, equatorial orbits about a spinning supermassive black hole. The accuracy of our model is established through comparisons against frequency-domain, Teukolsky-based waveforms in the radiative approximation. The calibration of eight high-order post-Newtonian parameters in the energy flux suffices to obtain a phase and fractional amplitude agreement of better than 1 radian and 1 % respectively over a period between 2 and 6 months depending on the system considered. This agreement translates into matches higher than 97 % over a period between 4 and 9 months, depending on the system. Better agreements can be obtained if a larger number of calibration parameters are included. Higher-order mass ratio terms in the effective-one-body Hamiltonian and radiation-reaction introduce phase corrections of at most 30 radians in a one year evolution. These corrections are usually one order of magnitude larger than those introduced by the spin of the small object in a one year evolution. These results suggest that the effective-one-body approach for extreme mass ratio inspirals is a good compromise between accuracy and computational price for LISA data analysis purposes.Comment: 21 pages, 8 figures, submitted to Phys. Rev.

A no-go theorem for slowly rotating black holes in Horava-Lifshitz gravity

We consider slowly rotating, stationary, axisymmetric black holes in the infrared limit of Horava-Lifshitz gravity. We show that such solutions do not exist, provided that they are regular everywhere apart from the central singularity. This has profound implications for the viability of the theory, considering the astrophysical evidence for the existence of black holes with non-zero spin. NOTE ADDED: A subtlety in the dynamical equivalence between Horava-Lifshitz gravity and Einstein-aether theory has been missed and this has seriously affected the conclusions of this paper. Please see arXiv:1212.1334 for a full discussionComment: 5 pages, 1 figure. Very minor changes to text (results unchanged) to match version accepted for publication in Phys. Rev. Let

Enucleation of a multilocular odontogenic keratocyst using sagittal osteotomy: A case report

Odontogenic keratocysts are significant cysts of the jaw that are characterized by aggressive behavior and a high tendency to recur. The treatments of choice may be radical or conservative, and in the literature a debate is still open about the gold standard in the treatment of OKCs.This report describes a wide multilocular OKC extended in the right mandibular ramus and illustrates atypical behavior of a cystic lobe after marsupialization, not found to our knowledge in the previous literature. Moreover, an orthognathic procedure, consisting of sagittal osteotomy was chosen for the excision of the cyst to preserve as much bone as possible and the integrity of the inferior alveolar nerve