# Christian Cherubini's research while affiliated with International Center for Relativistic Astrophysics and other places

## Publications (137)

Article
A profound difference has occurred in the analysis of Gamma Ray Bursts (GRBs) initially analyzed in the domain of gamma‐ray astronomy with the Compton Gamma Ray Observatory and the BATSE Detector with the extension to x‐ray astronomy and optical astronomy introduced by Beppo‐SAX and the KEK and VLT optical observatory, followed by the AGILE, Fermi...
Preprint
Full-text available
We address the physical origin of the ultrarelativistic prompt emission (UPE) phase of GRB 190114C observed in the interval 1.9-3.99 s, by the Fermi-GBM in 10 keV-10 MeV . Thanks to high S/N ratio of Fermi-GBM data, a time resolved spectral analysis has evidenced a sequence of similar blackbody plus cutoff power-law spectra, on ever decreasing time...
Article
We address the physical origin of the ultrarelativistic prompt emission (UPE) phase of GRB 190114C observed in the interval trf=1.9–3.99 s, by the Fermi-GBM in 10 keV–10 MeV energy band. Thanks to the high signal-to-noise ratio of Fermi-GBM data, a time-resolved spectral analysis has evidenced a sequence of similar blackbody plus cutoff power-law s...
Article
Alternans of cardiac action potential duration represent critical precursors for the development of life-threatening arrhythmias and sudden cardiac death. The system's thermal state affects these electrical disorders requiring additional theoretical and experimental efforts to improve a patient-specific clinical understanding. In such a scenario, w...
Article
We recall evidence that long gamma-ray bursts (GRBs) have binary progenitors and give new examples. Binary-driven hypernovae (BdHNe) consist of a carbon-oxygen core (COcore) and a neutron star (NS) companion. For binary periods ∼5 min, the COcore collapse originates the subclass BdHN I characterized by: 1) an energetic supernova (the “SN-rise”); 2)...
Preprint
Full-text available
We recall evidence that long gamma-ray bursts (GRBs) have binary progenitors and give new examples. Binary-driven hypernovae (BdHNe) consist of a carbon-oxygen core (CO$_{\rm core}$) and a neutron star (NS) companion. For binary periods $\sim 5$ min, the CO$_{\rm core}$ collapse originates the subclass BdHN I characterized by: 1) an energetic super...
Article
Calcium controls a large number of cellular processes at different scales. Decades of studies have pointed out the importance of calcium signaling in regulating differentiation, apoptosis, mitosis and functions such as secretion, muscle contraction and memory. The space-time structure of calcium signaling is central to this complex regulation. In p...
Article
Complex spatiotemporal patterns of action potential duration have been shown to occur in many mammalian hearts due to period-doubling bifurcations that develop with increasing frequency of stimulation. Here, through high-resolution optical mapping experiments and mathematical modeling, we introduce a characteristic spatial length of cardiac activit...
Preprint
Full-text available
Following Fermi and NOT observations, Ruffini et al. (2019b) soon identified GRB 190114C as BdHN I at z=0.424, it has been observed since, with unprecedented accuracy, [...] all the way to the successful optical observation of our predicted supernova (SN). This GRB is a twin of GRB 130427A. Here we take advantage of the GBM data and identify in it...
Preprint
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It has been shown recently that the "inner engine" of a type I BdHN is composed of a uniform magnetic field of $10^{14}$ G aligned with the rotation axis of a Kerr black hole both fulfilling the Wald solution. It is here shown using GRB 130427A as a prototype that this inner engine act in a sequence of "elementary impulses". The case of a single im...
Article
Full-text available
We numerically investigate the role of mechanical stress in modifying the conductivity properties of cardiac tissue, and also assess the impact of these effects in the solutions generated by computational models for cardiac electromechanics. We follow the recent theoretical framework from Cherubini et al. (2017), proposed in the context of general...
Preprint
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We motivate how the most recent progress in the understanding the nature of the GeV radiation in most energetic gamma-ray bursts (GRBs), the binary-driven hypernovae (BdHNe), has led to the solution of a forty years unsolved problem in relativistic astrophysics: how to extract the rotational energy from a Kerr black hole for powering synchrotron em...
Preprint
Full-text available
Complex spatiotemporal patterns of action potential duration have been shown to occur in many mammalian hearts due to a period-doubling bifurcation that develops with increasing frequency of stimulation. Here, through high-resolution optical mapping and numerical simulations, we quantify voltage length scales in canine ventricles via spatiotemporal...
Preprint
Full-text available
In this paper we introduce a new mathematical model for the active contraction of the cardiac muscle under different thermo-electric and nonlinear conductivity properties. The passive hyperelastic response of the tissue is described by an orthotropic exponential model, whereas the ionic activity dictates active contraction incorporated through the...
Preprint
Full-text available
We numerically investigate the role of mechanical stress in modifying the conductivity properties of the cardiac tissue and its impact in computational models for cardiac electromechanics. We follow a theoretical framework recently proposed in [Cherubini, Filippi, Gizzi, Ruiz-Baier, JTB 2017], in the context of general reaction-diffusion-mechanics...
Article
Plasma accreting processes on black holes represent a central problem for relativistic astrophysics. In this context, here we specifically revisit the classical Ruffini-Wilson work developed for analytically modeling via geodesic equations the accretion of perfect magnetized plasma on a rotating Kerr black hole. Introducing the horizon penetrating...
Article
Recent findings based on calcium fluorescence imaging of pancreatic islets, also combined with optogenetic techniques, showed that β-cells synchronization underlie a small-world and scale-free functional organization, where specified hubs are responsible of the emergent coordination in electrical activity. Despite these features were suggested to b...
Article
Full-text available
We have sub-classified short and long-duration gamma-ray bursts (GRBs) into seven families according to the binary nature of their progenitors. Short GRBs are produced in mergers of neutron-star binaries (NS-NS) or neutron star-black hole binaries (NS-BH). Long GRBs are produced via the induced gravitational collapse (IGC) scenario occurring in a t...
Chapter
Systems Biology represents nowadays a promising standard framework for natural and human sciences to attack complicated problems involving Life. Here a particular application of such a program is discussed in the case of Cancer, by using a basic toy model for solid tumor spread for framing together two apparently different conceptual leading paradi...
Chapter
The concepts of robustness and stability play a central role in many natural phenomena ranging from Astrophysics up to Life. In this contribution we discuss these concepts by specifically focusing on a biological paradigmatic mathematical model for the nonlinear electrophysiology of clusters of animal beta-cells.
Article
Full-text available
This paper describes the computationally informed design and experimental validation of a microfluidic chip device with multi-axial stretching capabilities. The device, based on PDMS soft-lithography, consisted of a thin porous membrane, mounted between two fluidic compartments, and tensioned via a set of vacuum-driven actuators. A finite element a...
Article
In this paper we analyze in detail the equilibrium configurations of classical polytropic stars with a multi-parametric differential rotation law of the literature using the standard numerical method introduced by Eriguchi and Mueller. Specifically we numerically investigate the parameters’ space associated with the velocity field characterizing bo...
Article
Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven families according to the binary nature of their progenitors. For short GRBs, mergers of neutron star binaries (NS–NS) or neutron star-black hole binaries (NS-BH) are proposed. For long GRBs, the induced gravitational collapse (IGC) paradigm proposes a tigh...
Article
A subject-specific three-dimensional viscoelastic finite element model of the human head-neck system is presented and investigated based on Computed Tomography and Magnetic Resonance biomedical images. Ad hoc imaging processing tools are developed for the reconstruction of the simulation domain geometry and the internal distribution of bone and sof...
Article
Full-text available
This work reports the results of the theoretical investigation of nonlinear dynamics and spiral wave breakup in a generalized two-variable model of cardiac action potential accounting for thermo-electric coupling and diffusion nonlinearities. As customary in excitable media, the common Q10 and Moore factors are used to describe thermo-electric feed...
Article
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We propose a new model to describe diffusion processes within active deformable media. Our general theoretical framework is based on physical and mathematical considerations, and it suggests to use diffusion tensors directly coupled to mechanical stress. A proof-of-concept experiment and the proposed generalised reaction-diffusion-mechanics model r...
Article
Objective: It has long been known that variations in temperature can facilitate the development of cardiac arrhythmias. Here, we aim to quantify the effects of temperature on cardiac alternans properties. Approach: in this work, we use optical mapping recordings of canine ventricular epicardial preparations to demonstrate that hypothermia can pr...
Article
We compute the binding energy and angular momentum of a test particle at the last stable circular orbit (LSO) on the equatorial plane around a general relativistic, rotating neutron star (NS). We present simple, analytic, but accurate formulas for these quantities that fit the numerical results and which can be used in several astrophysical applica...
Article
In a new classification of merging binary neutron stars (NSs) we separate short gamma-ray bursts (GRBs) in two sub-classes. The ones with $E_{\rm iso}\lesssim10^{52}$ erg coalesce to form a massive NS and are indicated as short gamma-ray flashes (S-GRFs). The hardest, with $E_{\rm iso}\gtrsim10^{52}$ erg, coalesce to form a black hole (BH) and are...
Article
The Von Mises quasi-linear second order wave equation, which completely describes an irrotational, compressible and barotropic classical perfect fluid, can be derived from a nontrivial least action principle for the velocity scalar potential only, in contrast to existing analog formulations which are expressed in terms of coupled density and veloci...
Conference Paper
Full-text available
We summarize the recent results on the physics and astrophysics of neutron stars presented in the Second ICRANet César Lattes Meeting in 2015.
Article
The activity of pancreatic β cells can be described by biological networks of coupled nonlinear oscillators that, via electrochemical synchronization, release insulin in response to augmented glucose levels. In this work, we analyze the emergent behavior of regular and percolated β-cells clusters through a stochastic mathematical model where "funct...
Article
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The identification of the basic mechanisms responsible for cardiovascular diseases stands as one of the most challenging problems in modern medical research including various mechanisms which encompass a broad spectrum of space and time scales. Major implications for clinical practice and pre-emptive medicine rely on the onset and development of in...
Article
We construct equilibrium configurations of uniformly rotating neutron stars for selected relativistic mean-field nuclear matter equations of state (EOS). We compute in particular the gravitational mass ($M$), equatorial ($R_{\rm eq}$) and polar ($R_{\rm pol}$) radii, eccentricity, angular momentum ($J$), moment of inertia ($I$) and quadrupole momen...
Article
Computational modeling plays an important role in biology and medicine to assess the effects of hemodynamic alterations in the onset and development of vascular pathologies. Synthetic analytic indices are of primary importance for a reliable and effective a priori identification of the risk. In this scenario, we propose a multiscale fluid-structure...
Article
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In his research activity, Emilio Del Giudice explored the possibility to move towards a unified view of some long-range dynamics in nature, ranging from quantum field theory in physics up to biology. Such a view is adopted in this contribution by discussing a mathematical model for synchronized electrical behavior of pancreatic beta cells. The stoc...
Article
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The gradient of the fluid stresses exerted on curved boundaries, conventionally computed in terms of directional derivatives of a tensor, is here analyzed by using the notion of intrinsic derivative which represents the geometrically appropriate tool for measuring tensor variations projected on curved surfaces. Relevant differences in the two appro...
Article
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We investigate the interaction of intracellular calcium spatio-temporal variations with the self-sustained contractions in cardiac myocytes. A 3D continuum mathematical model is presented based on a hyperelastic description of the passive mechanical properties of the cell, combined with an active-strain framework to describe the active shortening o...
Article
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We present a general theoretical framework for the formulation of the nonlinear electromechanics of polymeric and biological active media. The approach developed here is based on the additive decomposition of the Helmholtz free energy in elastic and inelastic parts and on the multiplicative decomposition of the deformation gradient in passive and a...
Article
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The motion of test particles along circular orbits in the vacuum $C$ metric is studied in the Frenet-Serret formalism. Special orbits and corresponding intrinsically defined geometrically relevant properties are selectively studied.
Article
Beta cells in pancreas represent an example of coupled biological oscillators which via communication pathways, are able to synchronize their electrical activity, giving rise to pulsatile insulin release. In this work we numerically analyze scale free self-similarity features of membrane voltage signal power density spectrum, through a stochastic d...
Conference Paper
Complex spatiotemporal alternans patterns of action potential duration have been recently observed in large mammalian hearts. Multiple routes between the occurrence of high-order rhythms (discordant alternans) and their transition to chaos (ventricular fibrillation) have also been reported. In this work we extend the analysis of voltage optical map...
Article
Full-text available
Hypothermia is well known to be pro-arrhythmic, yet it has beneficial effects as a resuscitation therapy and valuable during intracardiac surgeries. Therefore, we aim to study the mechanisms that induce fibrillation during hypothermia. A better understanding of the complex spatiotemporal dynamics of heart tissue as a function of temperature will be...
Article
The "analogue gravity formalism", an interdisciplinary theoretical scheme developed in the past for studying several non relativistic classical and quantum systems through effective relativistic curved space-times, is here applied to largely deformable elastic bodies described by the nonlinear theory of solid mechanics. Assuming the simplest nonlin...
Article
Full-text available
We investigate the interaction of intracellular calcium spatio-temporal variations with the self-sustained contractions in cardiac myocytes. A consistent mathematical model is presented considering a hyperelastic description of the passive mechanical properties of the cell, combined with an active-strain framework to explain the active shortening o...
Article
Full-text available
Thermal effects affecting spatiotemporal behavior of cardiac tissue are discussed by relating temperature variations to proarrhythmic dynamics in the heart. By introducing a thermoelectric coupling in a minimal model of cardiac tissue, we are able to reproduce experimentally measured dynamics obtained simultaneously from epicardial and endocardial...
Article
Thermal effects affecting spatiotemporal behavior of cardiac tissue are discussed by relating temperature variations to proarrhythmic dynamics in the heart. By introducing a thermoelectric coupling in a minimal model of cardiac tissue, we are able to reproduce experimentally measured dynamics obtained simultaneously from epicardial and endocardial...
Article
Background: The integrity of the interactions and the 3D architecture among beta cell populations in pancreatic islets is critical for proper biosynthesis, storage and release of insulin. The aim of this study was to evaluate the effect on electrophysiological signalling of beta cells that is produced by progressive lymphocytic islet cell infiltra...
Article
The Von Mises second-order quasi-linear partial differential equation describes the dynamics of an irrotational, compressible and barotropic classical perfect fluid through a scalar function only, i.e. the velocity potential. It is shown here how to derive it in the case of a polytropic equation of state starting from a least action principle. The...
Article
The open approach for rhinoplasty offers excellent exposure of the various components of the nose in situ. The biggest advantage of the external approach is the complete anatomic exposure, which allows the surgeon to inspect the osteo-cartilagineous framework, while the biggest disadvantage is represented by the transcolumellar scar. The goal of th...
Conference Paper
Implantable hearing devices coupling with head natural vibrations is an open problem in biomechanics and acoustics. Computer models and experimental impact tests usually investigate spatial wave patterns and frequencies in relation to bone conduction. Here we propose a simulation study of the viscoelastic response of both a simplified and realistic...
Article
Full-text available
Spiral waves in excitable biological media are associated with pathological situations. In the heart an action potential vortex pinned by an obstacle has to be removed through defibrillation protocols fine-tuned theoretically by using electrophysiological nonlinear mathematical models. Cardiac tissue, however, is an electroelastic medium whose elec...
Article
Von Mises’ nonlinear second-order wave equation for the velocity potential in the case of an irrotational, compressible and barotropic classical perfect fluid is connected to the analog gravity formalism. It is shown that while the standard acoustic metric, built on a certain background, remains central in the higher-order perturbative scheme, at f...
Article
The draining bathtub flow, a cornerstone in the theory of acoustic black holes, is here extended to the case of exact solutions for compressible nonviscous flows characterized by a polytropic equation of state. Investigating the analytical configurations obtained for selected values of the polytropic index, it is found that each of them becomes non...
Article
The ‘‘effective geometry” formalism is used to study the perturbations of a white dwarf described as a self-gravitating fermion gas with a completely degenerate relativistic equation of state of barotropic type. The quantum nature of the system causes an absence of homological properties, manifested instead by polytropic stars, and requires a param...
Article
Full-text available
Space-time patterns of wall shear stress (WSS) resulting from the numerical simulation of pulsating hemodynamic flows in semicoronal domains are analyzed, in the case of both regular semicoronal domains and semicoronal domains with bumpy insertions, mimicking aneurysm-like geometries. A new family of cardiovascular risk indicators, which we name th...
Article
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Cancer spread is a dynamical process occurring not only in time but also in space which, for solid tumors at least, can be modeled quantitatively by reaction and diffusion equations with a bistable behavior: tumor cell colonization happens in a portion of tissue and propagates, but in some cases the process is stopped. Such a cancer proliferation/e...
Article
Many biological systems which appear complex both in space and time and result still not understood, require new theoretical approaches for their nonlinear dynamics. In particular we focus here on the theoretical analysis of the underlying mechanisms of heart dynamics. This could clarify the (apparently) chaotic behavior of the normal heart-beat an...
Chapter
We present an electromechanical model of myocardium tissue, coupling finite elasticity, endowed with the capability of describing muscle contractions, with a FitzHugh–Nagumo type system, describing the electrical activity proper to excitable media. Here, we exploit a novel point of view which introduces the notion of active deformation as opposed t...
Article
Full-text available
Spiral waves appear in many different natural contexts: excitable biological tissues, fungi and amoebae colonies, chemical reactions, growing crystals, fluids and gas eddies as well as in galaxies. While the existing theories explain the presence of spirals in terms of nonlinear parabolic equations, it is explored here the fact that self-sustained...
Article
Full-text available
The \lq\lq effective geometry" formalism is used to study the perturbations of a perfect barotropic Newtonian self-gravitating rotating and compressible fluid coupled with gravitational backreaction. The case of a uniformly rotating polytrope with index $n=1$ is investigated, due to its analytical tractability. Special attention is devoted to the g...
Article
Analog curved spacetimes emerging from non-relativistic condensed matter systems can be very useful in understanding general relativistic effects. In this article, we analyze different boundary conditions for scattering processes from an acoustic black hole, focusing in particular on the acoustic "black hole bomb" phenomenon in the time domain. Mor...
Article
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Paralytic ileus is a temporary syndrome with impairment of peristalsis and no passage of food through the intestine. Although improvements in supportive measures have been achieved, no therapy useful to specifically reduce or eliminate the motility disorder underlying postoperative ileus has been developed yet. In this paper, we draw a plausible, p...
Article
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A free vortex in excitable media can be displaced and removed by a wave train. However, simple physical arguments suggest that vortices anchored to large inexcitable obstacles cannot be removed similarly. We show that unpinning of vortices attached to obstacles smaller than the core radius of the free vortex is possible through pacing. The wave-tra...
Article
An extension of the Hodgkin–Huxley mathematical model for the propagation of nerve signal which takes into account dynamical heat transfer in biological tissue is derived and fine tuned with existing experimental data. The medium is heated by Joule’s effect associated with action potential propagation, leading to characteristic thermal patterns in...
Article
Full-text available
An exact solution of Einstein's equations representing the static gravitational field of a quasi-spherical source endowed with both mass and mass quadrupole moment is considered. It belongs to the Weyl class of solutions and reduces to the Schwarzschild solution when the quadrupole moment vanishes. The geometric properties of timelike circular orbi...
Article
General relativity considers Dixon’s theory as the standard theory to deal with the motion of extended bodies in a given gravitational background. We discuss here the features of the “reaction” of an extended body to the passage of a weak gravitational wave. We find that the body acquires a dipolar moment induced by its quadrupole structure. Furthe...