Hydrodynamical simulations of the tidal stripping of binary stars by massive black holes

In a galactic nucleus, a star on a low angular momentum orbit around the central massive black hole can be fully or partially disrupted by the black hole tidal field, lighting up the compact object via gas accretion. This phenomenon can repeat if the star, not fully disrupted, is on a closed orbit. Because of the multiplicity of stars in binary systems, also binary stars may experience in pairs such a fate, immediately after being tidally separated. The consumption of both the binary components by the black hole is expected to power a double-peaked flare. In this paper, we perform for the first time, with GADGET2, a suite of smoothed particle hydrodynamics simulations of binary stars around a galactic central black hole in the Newtonian regime. We show that accretion luminosity light curves from double tidal disruptions reveal a more prominent knee, rather than a double peak, when decreasing the impact parameter of the encounter and when elevating the difference between the mass of the star which leaves the system after binary separation and the mass of the companion. The detection of a knee can anticipate the onset of periodic accretion luminosity flares if one of the stars, only partially disrupted, remains bound to the black hole after binary separation. Thus knees could be precursors of periodic flares, which can then be predicted, followed up and better modelled. Analytical estimates in the black hole mass range $10^5-10^8 \rm M_{\rm \odot}$ show that the knee signature is enhanced in the case of black holes of mass $10^6-10^7 \rm M_{\rm \odot}$.Comment: 14 pages, 6 figures, 8 tables. Accepted by MNRA

SERIOUS GAMES TO COPE WITH THE GENETIC TEST REVOLUTION

Il progresso tecnologico e l'abbassamento del costo di sequenziamento del DNA, hanno reso i test genetici sempre pi\uf9 accessibili al pubblico. Questo sviluppo per\uf2 non procede di pari passo con la scarsa conoscenza che la gente comune risulta avere in ambito genetico. Oggi giorno \ue8 possibile sottoporsi ad un test genetico autonomamente senza il consulto medico, ma la diffusa carenza di consapevolezza e informazione in questo ambito pu\uf2 portare ad un fraintendimento dei risultati genetici ottenuti e quindi a possibili conseguenze negative per quanto concerne le decisioni relative alla propria salute. Per cercare di porre rimedio a questa lacuna sono state sviluppate diverse policy. Tra queste, la necessit\ue0 di educare la gente sui concetti di genetica assume un rilievo di particolare importanza. Si vuole infatti cercare di potenziare la consapevolezza della cittadinanza, favorendo prese di decisione in ambito medico pi\uf9 responsabili. Per ottenere questo risultato l'impiego di Serious Games (SG) sembra uno tra gli approcci pi\uf9 promettenti. I SG hanno infatti mostrato ottimi risultati se impiegati in ambiti quali l'educazione, l'addestramento, la promozione della salute e la socializzazione; ecco dunque perch\ue8 sembrano essere un valido strumento per divulgare concetti di genetica tra la gente comune. Lo scopo di questa ricerca \ue8 studiare la possibilit\ue0 di utilizzare i SG come media fortemente interattivo per incoraggiare un apprendimento esperienziale, aumentare la conoscenza e promuovere il processo cognitivo dell'autoefficacia nel contesto dei processi decisionali in ambito genetico. Per ottenere questo risultato esploriamo lo stato dell'arte dei SG legati alla genetica e discutiamo sulla possibilit\ue0 di farli utilizzare dalla gente comune. Successivamente progettiamo, sviluppiamo e testiamo una suite di SG su misura per educare la gente sui concetti di genetica e di test genetico. Lo sviluppo e la validazione di videogiochi arcade custom per illustrare concetti di genetica di base e l'utilizzo del genere ``Adventure Game'' per mettere in relazione il rischio genetico individuale ai fattori dello stile di vita, risulta essere, sulla base delle nostre ricerche, completamete nuovo in questo ambito. Concludiamo infine presentando i risultati della ricerca condotta testando i videogiochi sviluppati per quanto riguarda la loro usabilit\ue0, la capacit\ue0 di trasferire conoscenza e migliorare il processo cognitivo nell'ambito dei processi decisionali in ambito medico e analizzando i dati collezionati durante le sessioni di gioco.Technological progress and the lowering of DNA sequencing costs have made genetic testing increasingly accessible to the general public. However, this progress does not reflect an increased genetics literacy in lay people that at present remains poor. Thus almost everyone has the possibility to undergo genetic testing independently, but the diffuse lack of knowledge may lead to misinterpretation of genetic information and result in negative consequences for personal health decisions. Several policies have been developed to try to address this issue. The most appropriate one is to educate people about genetic concepts and genetic test interpretation, to empower them in order to make responsible health-related decisions. To reach this goal the Serious Games (SG) approach seems very promising as it has been shown to be very powerful in education, training, health promotion, and socialization. This is why SG appear an attractive means to communicate genetic concepts to the general public. The aim of this research is to study the feasibility of using SG as a highly interactive medium to encourage experiential learning, increase literacy and promote self-efficacy in the genetic-related decision-making process. For this purpose, we explore state-of-the-art of Serious Games related to genetics, discussing whether these games are an adequate instrument to increase literacy and self-efficacy in the general public. Based on this analysis we design, develop and test a suite of SG specifically tailored to educate people about genetic concepts and genetic testing. To maximize the efficacy and mass appeal, the level of complexity of genetic information was balanced with the intent of making comprehensible and usable games. We believe that our approach --development and validation, using an evidence-based approach, of customized arcade games to convey basic genetics concepts together with the use of the ``Adventure Game'' genre to relate the individual genetic risk with lifestyle factors-- is completely new in this field. We conclude by discussing results about usability/playability, knowledge transfer and self-efficacy promotion in the field of health-related decision making, analysing data collected during monitored playing sessions

Multiplicative spectrum of ultrametric Banach algebras of continuous functions

International audienceLet $K$ be an ultrametric complete field and let $E$ be an ultrametric space. Let $A$ be the Banach $K$-algebra of bounded continuous functions from $E$ to $K$ and let $B$ be the Banach $K$-algebra of bounded uniformly continuous functions from $E$ to $K$. Maximal ideals and continuous multiplicative semi-norms on $A$ (resp. on $B$) are studied by defining relations of stickness and contiguousness on ultrafilters that are equivalence relations. So, the maximal spectrum of $A$ (resp. of $B$) is in bijection with the set of equivalence classes with respect to stickness (resp. to contiguousness). Every prime ideal of $A$ or $B$ is included in a unique maximal ideal and every prime closed ideal of $A$ (resp. of $B$) is a maximal ideal, hence every continuous multiplicative semi-norms on $A$ (resp. on $B$) has a kernel that is a maximal ideal. If $K$ is locally compact, every maximal ideal of $A$, (resp. of $B$) is of codimension $1$. Every maximal ideal of $A$ or $B$ is the kernel of a unique continuous multiplicative semi-norm and every continuous multiplicative semi-norm is defined as the limit along an ultrafilter on $E$. Consequently, on $A$ as on $B$ the set of continuous multiplicative semi-norms defined by points of $E$ is dense in the whole set of all continuous multiplicative semi-norms. Ultrafilters show bijections between the set of continuous multiplicative semi-norms of $A , \ Max(A)$ and the Banaschewski compactification of $E$ which is homeomorphic to the topological space of continuous multiplicative semi-norms. The Shilov boundary of $A$ (resp. $B$) is equal to the whole set of continuous multiplicative semi-norms

The ultrametric corona problem

International audienceLet $K$ be a complete ultrametric algebraically closed field and let $A$ be the $K$-Banach algebra of bounded analytic functions in the disk $D:\ |x|<1$. Let $Mult(A,\Vert \ . \ \Vert)$ be the set of continuous multiplicative semi-norms of $A$, let $Mult_m(A,\Vert \ . \ \Vert)$ be the subset of the $\phi \in Mult(A,\Vert \ . \ \Vert)$ whose kernel is a maximal ideal and let $Mult_a(A,\Vert \ . \ \Vert)$ be the subset of the $\phi \in Mult_m(A,\Vert \ . \ \Vert)$ whose kernel is of the form $(x-a)A, \ a\in D$ ( if $\phi \in Mult_m(A,\Vert \ . \ \Vert)\setminus Mult_a(A,\Vert \ . \ \Vert)$, the kernel of $\phi$ is then of infinite codimension). The main problem we examine is whether $Mult_a(A,\Vert \ . \ \Vert)$ is dense inside $Mult_m(A,\Vert \ . \ \Vert)$ with respect to the topology of simple convergence. This a first step to the conjecture of density of $Mult_a(A,\Vert \ . \ \Vert)$ in the whole set $Mult(A,\Vert \ . \ \Vert)$: this is the corresponding problem to the well-known complex corona problem. We notice that if $\phi \in Mult_m(A,\Vert \ . \ \Vert)$ is defined by an ultrafilter on $D$, $\phi$ lies in the closure of $Mult_a(A,\Vert \ . \ \Vert)$. Particularly, we shaw that this is case when a maximal ideal is the kernel of a unique $\phi \in Mult_m(A,\Vert \ . \ \Vert)$. Thus, if every maximal ideal is the kernel of a unique $\phi \in Mult_m(A,\Vert \ . \ \Vert)$, $Mult_a(A,\Vert \ . \ \Vert)$ is dense in $Mult_m(A,\Vert \ . \ \Vert)$. And particularly, this is the case when $K$ is strongly valued. In the general context, we find a subset of $Mult_m(A,\Vert \ . \ \Vert)\setminus Mult_a(A,\Vert \ . \ \Vert)$ which is included in the closure of $Mult_a(A,\Vert \ . \ \Vert)$. More generally, we show that if $\psi \in Mult(A,\Vert \ . \ \Vert)$ does not define the Gauss norm on polynomials $(\Vert \ . \ \Vert)$, then it is characterized by a circular filter, like on rational functions and analytic elements. As a consequence, if $\psi$ does not lie in the closure of $Mult_a(A,\Vert \ . \ \Vert)$, then its restriction to polynomials is the Gauss norm

The role of technology in improving the Customer Experience in the banking sector: a systematic mapping study

Information Technology (IT) has revolutionized the way we manage our money. The adoption of innovative technologies in banking scenarios allows to access old and new financial services but in a faster and more secure, comfortable, rewarding and engaging way. The number, the performances and the seamless integration of these innovations is a driver for banks to retain their customers and avoid costly change of hearts. The literature is rich in works reporting on the use of technology with direct or indirect impact on the experience of banking customers. Some mapping studies about the adoption of technologies in the field exist, but they are specific to particular technologies (e.g., only Artificial Intelligence), or vice versa too generic (e.g., reviewing the adoption of technologies to support any kind of banking process). So a specific research effort on the crossed domain of technology and Customer Experience (CX) is missing. This paper aims to overcome the following gaps: the lack of a comprehensive map of the research made in the field in the past decade; a discussion on the current research trends of top publications and journals is missing; the next research challenges are yet to be identified. To face these limitations, we designed and submitted 7 different queries to pull papers out of 4 popular scientific databases. From an initial set of 6,756 results, we identified a set of 89 primary studies that we thoroughly analyzed. A selection of the top 20% works allowed us to seek the most performant technologies as well as other promising ones that have not been experimented yet in the field. Main results prove that the combined study of technology and CX in the banking sector is not approached systematically and thus the development of a new specific research line is needed

"Spoon-feeding" an AGN

Tidal disruption events (TDEs) occur when a star, passing too close to a massive black hole, is ripped apart by tidal forces. A less dramatic event occurs if the star orbits just outside the tidal radius, resulting in a mild stripping of mass. Thus, if a star orbits a central black hole on one of these bound eccentric orbits, weaker outbursts will occur recurring every orbital period. Thanks to five Swift observations, we observed a recent flare from the close by (92 Mpc) galaxy IC 3599, where a possible TDE was already observed in December 1990 during the Rosat All-Sky Survey. By light curve modeling and spectral fitting, we account for all these events as the non-disruptive tidal stripping of a single star into a 9.5 yr highly eccentric bound orbit. This is the first example of periodic partial tidal disruptions, possibly spoon-feeding the central black hole.Comment: 7 pages, 3 figures, to appear in "Swift:10 years of discovery", Proceedings of Scienc

Geometric Identities in Lattice Theory

AbstractAn Arguesian identity is an identity in Grassmann–Cayley algebras with certain multi-linear properties of expressions in joins and meets of vectors and covectors. Many classical theorems of projective geometry and their generalizations to higher dimensions can be expressed as simple and elegant Arguesian identities. In a previous work we showed that an Arguesian identity can be unfolded with respect to a vector variable to obtain a lattice inequality, which holds in various lattices. In this paper, we extend this technique to an arbitrary variable. We prove that for any variable v of an Arguesian identity I, a lattice inequality can be obtained by unfolding I with respect to the variable v. This inequality and its dual are valid in the class of linear lattices if the identity is of order 2, and in the congruence variety of Abelian groups if the identity is of a higher order. Consequently, we obtain a family of lattice identities which are self-dual over the class of linear lattices. In particular, all the inequalities obtained by this method are valid in the lattice of subspaces of a vector space, which are characteristic-free and independent of dimensions

WoX+: A Meta-Model-Driven Approach to Mine User Habits and Provide Continuous Authentication in the Smart City

The literature is rich in techniques and methods to perform Continuous Authentication (CA) using biometric data, both physiological and behavioral. As a recent trend, less invasive methods such as the ones based on context-aware recognition allows the continuous identification of the user by retrieving device and app usage patterns. However, a still uncovered research topic is to extend the concepts of behavioral and context-aware biometric to take into account all the sensing data provided by the Internet of Things (IoT) and the smart city, in the shape of user habits. In this paper, we propose a meta-model-driven approach to mine user habits, by means of a combination of IoT data incoming from several sources such as smart mobility, smart metering, smart home, wearables and so on. Then, we use those habits to seamlessly authenticate users in real time all along the smart city when the same behavior occurs in different context and with different sensing technologies. Our model, which we called WoX+, allows the automatic extraction of user habits using a novel Artificial Intelligence (AI) technique focused on high-level concepts. The aim is to continuously authenticate the users using their habits as behavioral biometric, independently from the involved sensing hardware. To prove the effectiveness of WoX+ we organized a quantitative and qualitative evaluation in which 10 participants told us a spending habit they have involving the use of IoT. We chose the financial domain because it is ubiquitous, it is inherently multi-device, it is rich in time patterns, and most of all it requires a secure authentication. With the aim of extracting the requirement of such a system, we also asked the cohort how they expect WoX+ will use such habits to securely automatize payments and identify them in the smart city. We discovered that WoX+ satisfies most of the expected requirements, particularly in terms of unobtrusiveness of the solution, in contrast with the limitations observed in the existing studies. Finally, we used the responses given by the cohorts to generate synthetic data and train our novel AI block. Results show that the error in reconstructing the habits is acceptable: Mean Squared Error Percentage (MSEP) 0.04%