Astrophysical constraints on extended gravity models

We investigate the propagation of gravitational waves in the context of fourth order gravity nonminimally coupled to a massive scalar field. Using the damping of the orbital period of coalescing stellar binary systems, we impose constraints on the free parameters of extended gravity models. In particular, we find that the variation of the orbital period is a function of three mass scales which depend on the free parameters of the model under consideration; we can constrain these mass scales from current observational data.Comment: 22 pages; minor changes to match published versio

Constraints on NonCommutative Spectral Action from Gravity Probe B and Torsion Balance Experiments

Noncommutative spectral geometry offers a purely geometric explanation for the standard model of strong and electroweak interactions, including a geometric explanation for the origin of the Higgs field. Within this framework, the gravitational, the electroweak and the strong forces are all described as purely gravitational forces on a unified noncommutative space-time. In this study, we infer a constraint on one of the three free parameters of the model, namely the one characterising the coupling constants at unification, by linearising the field equations in the limit of weak gravitational fields generated by a rotating gravitational source, and by making use of recent experimental data. In particular, using data obtained by Gravity Probe B, we set a lower bound on the Weyl term appearing in the noncommutative spectral action, namely $\beta \gtrsim 10^{-6}$m$^{-1}$. This constraint becomes stronger once we use results from torsion balance experiments, leading to $\beta \gtrsim 10^{4}$m$^{-1}$. The latter is much stronger than any constraint imposed so far to curvature squared terms.Comment: 12 page

Virial theorem in scalar tensor fourth order gravity

AbstractIn this paper, we study, in the Newtonian limit, the virial theorem in the context of a scalar tensor fourth order gravity. In particular, we show, that for a isolated galaxy in viral equilibrium, a specific class of scalar tensor fourth order gravity, i.e. $$f(R,\phi )+\omega (\phi )\,\phi _{;\alpha }\,\phi ^{;\alpha }$$ f ( R , ϕ ) + ω ( ϕ ) ϕ ; α ϕ ; α in not suitable to explain the large fraction of dark matter necessary to have the flatness of the galaxies rotation curves experimentally observed

Automatic Mode Switching in Atrial Fibrillation

Automatic mode switching (AMS) algorithms were designed to prevent tracking of atrial tachyarrhythmias (ATA) or other rapidly occurring signals sensed by atrial channels, thereby reducing the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. The inclusion of an AMS function in most dual chamber pacemaker now provides optimal management of atrial arrhythmias and allows the benefit of atrioventricular synchrony to be extended to a population with existing atrial fibrillation. Appropriate AMS depends on several parameters: a) the programmed parameters; b) the characteristics of the arrhythmia; c) the characteristics of the AMS algorithm. Three qualifying aspects constitute an AMS algorithm: onset, AMS response, and resynchronization. Since AMS programs also provide data on the time of onset and duration of AMS episodes, AMS data may be interpreted as a surrogate marker of ATAs recurrence. Recently, stored electrograms corresponding to episodes of ATAs have been introduced, thus clarifying the accuracy of AMS in detecting ATAs Clinically this information may be used to assess the efficacy of an antiarrhythmic intervention or the risk of thromboembolic events, and it may serve as a valuable research tool for evaluating the natural history and burden of ATAs

Photon frequency shift in curvature based Extended Theories of Gravity

We study the frequency shift of photons generated by rotating gravitational sources in the framework of curvature based Extended Theories of Gravity. The discussion is developed considering the weak-field approximation. Following a perturbative approach, we analyze the process of exchanging photons between Earth and a given satellite, and we find a general relation to constrain the free parameters of gravitational theories. Finally, we suggest the Moon as a possible laboratory to test theories of gravity by future experiments which can be, in principle, based also on other Solar System bodies.Comment: 10 page

Noncommutative spectral geometry, algebra doubling and the seeds of quantization

A physical interpretation of the two-sheeted space, the most fundamental ingredient of noncommutative spectral geometry proposed by Connes as an approach to unification, is presented. It is shown that the doubling of the algebra is related to dissipation and to the gauge structure of the theory, the gauge field acting as a reservoir for the matter field. In a regime of completely deterministic dynamics, dissipation appears to play a key role in the quantization of the theory, according to 't Hooft's conjecture. It is thus argued that the noncommutative spectral geometry classical construction carries implicit in its feature of the doubling of the algebra the seeds of quantization.Comment: 12 pages; amended version to match publication in PR

Constraining models of extended theories of gravity with terrestrial and astrophysical experiments

2013 - 2014In this Thesis we report a general review of Extended Theories of Gravity and the fundamental aspects of General Relativity. We show the technicality of development of field equation with respect to Newtonian, Post-Newtonian approach and the post-Minkowskian limit. We analyse also the problem of how conformally transformed models behave in the weak field limit approximation. This issue could be extremely relevant in order to select conformally invariant physical quantities. The photon deflection is considered in the framework of the Newtonian Limit of a general class of f (R, Rαβ Rαβ, RαβγδRαβγδ) - Gravity where f is an unspecific function of the Ricci scalar R, Ricci tensor squareRαβ Rαβ and Riemann tensor square RαβγδRαβγδ. Studying in the weak-field approximation - Newtonian and Post-Newtonian limit - the geodesic and Lense-Thirring processions by using the recent experimental results of the Gravity Probe B and LARES satellite and using the damping of the orbital period of coalescing stellar binary systems, we impose constraints on the free parameters of such models of Extended Theories of Gravity. [edited by author]XIII n.s

Automatic mode switching in atrial fibrillation

Automatic mode switching (AMS) algorithms were designed to prevent tracking of atrial tachyarrhythmias (ATA) or other rapidly occurring signals sensed by atrial channels, thereby reducing the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. The inclusion of an AMS function in most dual chamber pacemaker now provides optimal management of atrial arrhythmias and allows the benefit of atrioventricular synchrony to be extended to a population with existing atrial fibrillation. Appropriate AMS depends on several parameters: a) the programmed parameters; b) the characteristics of the arrhythmia; c) the characteristics of the AMS algorithm. Three qualifying aspects constitute an AMS algorithm: onset, AMS response, and resynchronization. Since AMS programs also provide data on the time of onset and duration of AMS episodes, AMS data may be interpreted as a surrogate marker of ATAs recurrence. Recently, stored electrograms corresponding to episodes of ATAs have been introduced, thus clarifying the accuracy of AMS in detecting ATAs Clinically this information may be used to assess the efficacy of an antiarrhythmic intervention or the risk of thromboembolic events, and it may serve as a valuable research tool for evaluating the natural history and burden of ATAs

Un percorso di trasformazione nel nuovo assetto detentivo/riabilitativo post OPG: esposizione di un caso

L’articolo illustra il lavoro psicologico-clinico effettuato all’interno della “Articolazione per la Tutela della Salute Mentale in Carcere”, nuovo contesto di cura ed assistenza nato alla luce dei radicali cambiamenti attivati dal processo di superamento degli Ospedali Psichiatrici Giudiziari (OPG) e che accoglie soggetti autori di reato affetti da patologia psichiatrica, garantendone un’osservazione costante ed interventi riabilitativi ad alta intensità terapeutica. Il caso presentato, attraverso la narrazione del percorso detentivo/riabilitativo di un soggetto, iniziato con la reclusione in regime ordinario, proseguito con l’assegnazione all’OPG e con il successivo approdo presso l’Articolazione SMC (Salute Mentale in Carcere), ed esitato nel trasferimento in un contesto comunitario, mira ad essere esemplificativo della valenza trasformativa di un approccio rivolto al paziente che, nella gestione della patologia psichiatrica, superi i limiti di un assetto prevalentemente custodialistico, spesso predominante nei pregressi contesti ad essa dedicati, e dia priorità alle finalità terapeutico-riabilitative