ICRANet Scientific Report 2020 |

## ICRANet## The 2020 Scientific Report## Presented to## The Scientific Committee## by## Remo Ruffini## Director of ICRANet
In
1985 George Coyne, Francis Everitt, Fang Li-Zhi, Riccardo Giacconi (Nobel laureate 2002),
Remo Ruffini, Abdus Salam (Nobel laureate 1979), promoted the establishment of the International Centre for Relativistic Astrophysics (ICRA), asking the Rector of the University of Rome “La Sapienza” Antonio Ruberti to host the Centre at the Physics Department. ICRA became legal entity in 1991. A successful story of research followed for 30 years. ICRA was further extended to other Institutions, as it is clear from the
current Statute
At
the dawn of the new millennium it
was approached
the need to extend this activity, based on Italian national laws, to
the International scenario. Thanks to the support and advise of the
Italian Minister of Foreign Affairs, a Statute was drafted for
creating a truly international organization to develop the field of
relativistic astrophysics worldwide. ICRANet
has been indeed
created
by a law of the Italian Government, ratified unanimously by the
Italian Parliament and signed by the President of the Republic of
Italy on February 10
Extensive
Scientific reports have been presented every year to the Scientific
Committee by the Director of ICRANet (see
http://www.icranet.org/AnnualReports).
The aim of this 2020 report is to review the traditional fields
of research, upgrade the publication list and scientific results
obtained in the meantime in
the ICRANet Centers in Italy, Armenia, Brazil, France, report
on the status of the requests of adhesion to ICRANet by
Belarus and China
I
would like now
to remind some Scientific Meetings organized by ICRANet in 2020
We are completing the proceedings of:
We have also organized the following meetings:
Particularly intense have been the confirmation and extension of the existent agreements with the Universities and research centres. These collaborations are crucial in order to give ICRANet scientists the possibility to give courses and lectures in the Universities and, viceversa, to provide to the Faculty of such Universities the opportunity to spend research periods in ICRANet institutions.
One of the strong tools of success of the activity of ICRANet has been
the International Ph.D. Program in Relativistic Astrophysics (IRAP-PhD) promoted by ICRANet One of the major success of ICRANet has been to participate in the International competition of the Erasmus Mundus Ph.D. program and the starting of this program from the 2010. The participating institutions are: AEI – Albert Einstein Institute – Potsdam (Germany) ASI – Agenzia Spaziale Italiana (Italy) Bremen University (Germany) Bucaramanga University (Colombia) Carl von Ossietzky University of Oldenburg (Germany) CBPF – Brazilian Centre for Physics Research (Brazil) CNR – Consiglio Nazionale delle Ricerche (Italy) Ferrara University (Italy) ICRA (Italy) INAF – Istituto Nazionale di Astrofisica (Italy) Indian centre for space physics (India) Institut Hautes Etudes Scientifiques – IHES (France) Inst. of High Energy Physics of the Chinese Academy of Science – IHEP-CAS, China INPE (Instituto Nacional de Pesquisas Espaciais, Brasil) Max-Planck-Institut für Radioastronomie – MPIfR (Germany) National Academy of Science (Armenia) Observatory of the Côte d'Azur (France) Rome University – “Sapienza” (Italy) Savoie-Mont-Blanc University (France) Shanghai Astronomical Observatory (China) Stockholm University (Sweden) Tartu Observatory (Estonia) UAM – Universidad Autónoma Metropolitana (Mexico) Université Côte d'Azur (France)
The IRAP PHD program intends to create conditions for high level education in Astrophysics mainly in Europe to create a new generation of leading scientists in the region. No single university in Europe today has the expertise required to attain this ambitious goal by itself. For this reason we have identified universities which offers a very large complementarity expertise. The students admitted and currently following courses and doing research in such a program are given in the following:
We can now turn to the review of the scientific topics covered in the volumes 2 and 3.
Particularly important is this report, which summarizes the activities traditionally carried on by the ICRANet Armenian Scientists in the MAGIC and HESS collaborations, which acquire a particular relevance in view of the ICRANet Seat at the National Academy of Science in Armenia. This topic was motivated by Prof. Felix Aharonian joining ICRANet as representative of Armenia in the Scientific Committee and by his appointment as Adjunct Professor of ICRANet on the Benjamin Jegischewitsch Markarjan Chair. Many of the observational work done by Prof. Aharonian are crucial for the theoretical understanding of the ultra high energy sources. Prof. Aharonian started also his collaboration with the IRAP PhD program where he is following the thesis of graduate students as thesis advisor. The evolution and future prospects on the analysis of the high-energy gamma-ray emission are presented in this report by Prof. Aharonian and Dr. Sahakyan. The main new contribution in this very successful traditional field of research has been the nomination of Prof. Narek Sahakyan as Director of Yerevan ICRANet Centre. The support of the State Science Committee of Armenia has allowed to create in that Seat a remarkable number of IRAP-PhD students, and of Master and undergraduate students, with administrative and technical support.
ICRANet-Minsk center was established in 2017 following the agreement between ICRANet and the National Academy of Sciences of Republic of Belarus. It operates in areas of Relativistic Astrophysics and Cosmology, in the theoretical and observational fields, in line with ICRANet activities. Specifically its research focuses on radiation transfer in relativistic plasma, kinetics of relativistic plasma, and effects of gravity in light nteraction with quantum systems. Due to requirement of heavy parallel computing, special hardware is developed, in particular the workstation of ICRANet-Minsk which is based on GPU modules allowing peak power of 14 TFLOPS.
The BSDC has been one of the leading projects of ICRANet Brazil which has been more significantly affected by the absence of support from Brazil. No matter these economical difficulties, the BSDC Centre has been fully operative and is now producing the first ICRANet catalog of Active Galactic Nuclei and of Gamma-Ray Bursts.
This field has been pioneered by Prof. Belinski, in collaboration with Prof. Thibault Damour in Paris, Prof. Mark Henneaux at the University of Bruxelles, Prof. Hermann Nicolai in Berlin. A Lectio Magistralis by Prof. Belinski on the physics of fundamental interaction and unification field theory which is available on the ICRANet channel on YouTube (https://www.youtube.com/watch?v=omyR2hcgFic). The application of the Inverse Scattering Method (ISM), based on the Lax representation, to the integration of the vacuum Einstein equations was developed in 1978 by V.A.Belinski and V.E.Zakharov (BZ in the sequel). By this method they discovered the gravitational solitons, that is the solitonic excitations of the gravitational field in empty spacetime. In particular, there was shown that the Schwarzschild and Kerr black holes are solitons in the exact mathematical sense. Before 1987 only two cases of non-vacuum extension of this techniques were known. These are the case of perfect liquid with stiff matter equation of state (V.A.Belinski, 1979) and the case of electromagnetic field (G.A.Alekseev, 1980). In the framework of the last extention it was shown that the Reissner-Nordstrom and Kerr-Newman black holes also are solitons in the exact mathematical sense. Quite new non-vacuum extension of the ISM have been found in supergravity when two-dimensional spacetime is filled by the scalar fields and their fermionic superpartners. This outstanding integrable model have been created in 1987 by H.Nicolai. However, in spite of the big principal success this model had two technical shortcomings: (i) the integrability conditions of the Nicolai Lax pair does not contains the Dirac-like equations for the fermionic fields. Instead this linear spectral problem gives only a system of equations for some bosonic quadratic combinations made from fermions, (ii) the Nicolai Lax-pair has the poles of the second order in the complex plane of the spectral parameter while the pure gravity Lax representation has the poles of the first order only. The question aroused whether the Nicolai model can be covered by appropriately extended BZ approach because the last one is simpler and contains the fully developed technics for construction the exact solitonic solutions. This question was answered in affirmative and the foregoing two technical nuisances was removed during 2015-2016 in collaboration between ICRANet and Albert Einstein Institute at Golm. To cover the Nicolai model by the BZ approach it is necessary to extend the last one to the multidimensional superspace (including the anticommuting coordinates). In such a framework it was found the reformulation of the Nicolai linear spectral problem in the form containing only simple poles with respect the spectral parameter and leading (apart of equations for scalar fields) also to the Dirac-like equations for the fermionic superpartners of these scalars. Alongside with application to the Nicolai supergravity the constructed generalization of the BZ approach in superspace contains a possibility to generate the equations of motion for the much bigger array of the interacting bosonic and fermionic fields. However, the physical meaning of these new integrable systems remains to be clarified.
This has been one the most important field of research at the ICRANet Centre in Pescara. Following the new GRB classification into seven different families introduced by ICRANet in 2016, we published the first catalog of all the observed Binary Driven Hypernovae (BdHNe), the GRB family which corresponds to the most energetic “long GRBs”, with more than 300 analyzed sources.
Moreover,
in
2016
we
started a complete rewrite of the numerical codes used to simulate
the evolution of the electron-positron plasma producing a GRB and its
interaction with the surrounding medium. This was meant to upgrade
from the simplified semi-analytical approach, which had been used
until then, to a full numerical integration of the complete system of
partial differential equations describing the system. This upgrade of
the numerical codes is still ongoing.
The
first results of these new codes have
been applied successfully to
the study of early X-Ray Flares observed
in BdHNe.
This
led to the first comprehensive theory of the phenomenon and to the
definition of the space-time diagram of BdHNe,
which clearly show the markedly different regimes between the GRB
Ultrarelativistic
Prompt
Emission
(UPE),
with Lorentz gamma factors on the order of 10
Astroparticle physics is a new field of research emerging at the intersection of particle physics, astrophysics and cosmology. We focused on several topics with three major directions of research: a) electron-positron plasma, b) thermal emission from relativistic plasma and GRBs, c) Relativistic kinetic theory and its applications; and d) ultra high energy particles.
We also obtained new results on
propagation of
The unsolved problem of a physical solution in general relativity of an astrophysical object which must be characterized necessarily by four parameters, mass, charge, angular momentum and quadrupole moment, has also been debated for years and it is yet not satisfactorily solved. The presence in ICRANet of Prof. Quevedo as an Adjunct Professor has shown an important result published by Bini, Geralico, Longo, Quevedo [Class. Quant. Grav., 26 (2009), 225006]. This result has been obtained for the special case of a Mashhoon-Quevedo solution characterized only by mass, angular momentum and quadrupole moment. It has been shown that indeed such a Mashhoon-Quevedo solution can be matched to an internal solution solved in the post-Newtonian approximation by Hartle and Thorne for a rotating star. The most important metrics in general relativity is the Kerr-Newman solution which describes the gravitational and electromagnetic fields of a rotating charged mass, characterized by its mass M, charge Q and angular momentum L in geometrical units. This solution characterizes the field of a black hole. For astrophysical purposes, however, it is necessary to take into account the effects due to the moment of inertia of the object. To attack this problem, an exact solution of the Einstein-Maxwell equations have been proposed by Mashhoon and Quevedo which posses an infinite set of gravitational and electromagnetic multipole moments. It is not clear, however, how this external solution to an astrophysical object can be matched to a physical internal solution corresponding to a physically acceptable rotating mass.
Prof. Einasto has been
collaborating in the previous years intensively within ICRANet about
the large scale structure of the Universe and its possible fractal
structure. With Prof. Einasto there is also the collaboration of
Prof. G. Hutsi. Prof. Einasto is an Adjunct Professor of ICRANet and
an active member of the Faculty of the IRAP PhD. Prof. Einasto has
completed a book reviewing the status of the dark matter and the
large scale structure of the universe published by World Scientific
as Volume 14
This report refers to the activity of Prof. Brian Punsly, who is actively participating within ICRANet with the publication of his internationally recognized book on “Black hole gravitohydromagnetics”, the first and second edition (2010) being published with Springer. In addition, Prof. Punsly have been interested in observational properties of quasars such as broad line emission excess in radio loud quasars accentuated for polar line of sight and excess narrow line widths of broad emission lines in broad absorption line quasars, showing that this is best explained by polar lines of sight.
This problem
The
^{4}
τ
(R. Ruffini, L. Vitagliano, S.-S. Xue, Phys. Lett. B 559, (2003) 12).
As soon as the thermalization has occurred, the hydrodynamic
expansion of this electrically neutral plasma starts (R. Ruffini, J.
Salmonson, J. Wilson, S.-S. Xue, A&A Vol. 335 (1999) 334; Vol.
359 (2000) 855). While the temporal evolution of the _{C}e^{+}e
gravitationally collapsing core moves inwards, giving rise to a
further amplified supercritical field, which in turn generates a
larger amount of ^{−}e^{+}e
pairs leading to a yet higher temperature in the newly formed ^{−}e^{+}eγ
plasma. As a consequence, an enormous amount of pairs is left behind
the collapsing core and a Dyadosphere (G. Preparata, R. Ruffini,
S.-S. Xue, A&A Vol. 338 (1998) L87) is formed. see also B. Han,
R. Ruffini, S.-S. Xue, Physics Review D86, 084004 (2012), R. Ruffini,
and S-S. Xue, Physics Letters A377 (2013) 2450.
^{−}The Schwinger pair-production and nonlinear QED effects in a curved space time are also studied. Taking into account the Euler-Heisenberg effective Lagrangian of one-loop nonperturbative QED contributions, we formulate the Einstein-Euler-Heisenberg theory and study the solutions of nonrotating black holes with electric and magnetic charges in spherical geometry (R. Ruffini, Y.-B. Wu and S.-S. Xue, Physics Review D88, 085004 (2013)). In addition, the Schwinger pair-production and back reaction are recently studied in de Sitter space time in order to understand their roles in early Universe, some results are published (C. Stahl, E. Strobel, and S.-S. Xue, Phys. Rev. D 93, 025004 (2016); C. Stahl and S.-S. Xue, Phys. Lett B 760, 288-292 (2016); E. Bavarsad, C. Stahl and S.-S. Xue, Phys. Rev. D 94, 104011 (2016)). An interesting aspect of effective field theories in the strong-field or strong coupling limit has recently been emphasized. We study that pair-production in super-position of static and plane wave fields, and in the strong fields expansion, the leading order behavior of the Euler-Heisenberg effective Lagrangian is logarithmic, and can be formulated as a power law (H. Kleinert, E. Strobel and S-S. Xue, Phys. Rev. D88, 025049 (2013), Annals of Physics Vol. 333 (2013) 104). We have also investigated the fundamental processes relevant to the issues of intense laser physics, pair-production (E. Strobel and S-S. Xue , Nucl. Phys B 886, (2014) 1153); two laser beams colliding with a high-energy photon (Y.-B. Wu and S-S. Xue, Phys. Rev. D 90, 013009 (2014))，as well as pair-oscillation leading to electromagnetic and gravitational radiation (W.-B. Han and S.-S. Xue, Phys. Rev. D89 (2014) 024008). We study the photon circular-polarization produced by two-laser beams collision (R. Mohammadi, I. Motie, and S.-S. Xue, Phys. Rev. A 89, 062111 (2014)), and by laser and neutrino beams collisions (Phys. Lett. B 731 (2014) 272; Phys. Rev. D 90, 091301(R) (2014)).
In
order to account for future observations of GRBs photon
polarizations, the possible microscopic origins and preliminary
values of GRBs photon polarizations are theoretically calculated (S.
Batebi, R. Mohammadi, R. Ruffini, S. Tizchang, and S.-S. Xue, Phys.
Rev. D 94, 065033 (2016)). Similarly, by considering possible
microscopic interactions and processes, we study the polarization of
CMB in cosmology, compared with recent observations (
The study of compact objects such as white dwarfs, neutron stars and black holes requires the interplay between nuclear and atomic physics together with relativistic field theories, e.g., general relativity, quantum electrodynamics, quantum chromodynamics, as well as particle physics. In addition to the theoretical physics aspects, the study of astrophysical scenarios characterized by the presence of a compact object has also started to be focus of extensive research within our group. The research which has been done and is currently being developed within our group can be divided into the following topics: nuclear and atomic astrophysics, compact stars (white dwarfs and neutron stars) physics and astrophysics including radiation mechanisms, exact solutions of the Einstein and Einstein-Maxwell equations applied to astrophysical systems and critical fields and non-linear electrodynamics effects in astrophysics. Also this year we have made progress in all the above fields of research. It is worth to mention that in the recent years it has been established a strong collaboration between the research on the observational and theoretical aspects of GRBs and the one on the physics and astrophysics aspects of white dwarfs and neutron stars. In particular, this collaboration has focused on the problem of establishing the possible progenitors of both short and long GRBs, together with the further development of the model for the explanation of the experimental data of GRBs from the radio all the way to the gamma-rays. In this line I would like to recall the work by Becerra et al. “On the induced gravitational collapse scenario of gamma-ray bursts associated with supernovae”, ApJ 833, 107 (2016), in which we have, following our induced gravitational collapse (IGC) paradigm of long GRBs, presented numerical simulations of the explosion of a carbon-oxygen core in a binary system with a neutron-star companion. In this work we have presented simulations that follow the hypercritical accretion process triggered onto the neutron star by the supernova explosion, the associated copious neutrino emission near the NS accreting surface, as well as all relevant hydrodynamic aspects within the accretion flow including the trapping of photons. We have shown that indeed the NS can reach the critical mass and collapse to a black hole producing a GRB. Interesting new lines of research has been opened thanks to this work: we have shown that the presence of the neutron star companion near the carbon-oxygen core causes strong asymmetries in the supernova ejecta and that the GRB emission can also interact with the supernova ejecta. Both phenomena cause specific observable signatures which we are currently examining and probing in GRB data. We have also gone further in probing neutron star binaries as progenitors of short GRBs. Especial mention has to be given in this line to the work of R. Ruffini et al., “GRB 090510: a genuine short-GRB from a binary neutron star coalescing into a Kerr-Newman black hole”, ApJ 831, 178 (2016). We are starting a new era in which, from GRB data, we can extract information on the neutron star parameters leading to black hole formation after the binary coalescence. This kind of research is also of paramount importance to put constraints on the matter content and equation of state at supranuclear densities in neutron stars. It is also important to mention that we are performing new research on the gravitational wave emission from compact object binaries leading to GRBs, which not only is important by itself but it is relevant to establish the capabilities of current second generation gravitational wave detectors such as Advanded LIGO to detect the gravitational waves associated with GRB events. We have to mention here the work by R. Ruffini et al., “On the classification of GRBs and their occurrence rates”, ApJ 832, 136 (2016), in which we have established a novel classification of short and long GRBs, their binary progenitors, as well as their occurence rate, being the latter necessary to predict a detection rate of the gravitational wave emission from GRBs. We have also made progress in the understanding of soft gamma ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The most used model for the explanation of SGRs/AXPs is based on “magnetars”, ultramagnetized neutron stars. Since there is so far no experimental evidence of such extreme, B > 100 TG, surface magnetic fields in neutron stars, we have focus our effort in analyzing the data of SGRs and AXPs and check whether these objects could be explained by canonical, well tested and experimentally confirmed stars. This was the main idea of a pioneering work of Malheiro, Rueda and Ruffini, “Soft-Gamma-Ray Repeaters (SGRs) and Anomalous X-Ray Pulsars (AXPs) as rotation powered white dwarfs”, PASJ 64, 56 (2012). It was there shown that, indeed, massive (masses of 1 solar mass), fast rotating (rotation periods 1-10 second), highly magnetized (magnetic fields of 1 giga gauss) white dwarfs could explain the observational properties of SGRs/AXPs. In addition, it was there shown that some sources (at the time four) could actually be ordinary, rotation-powered neutron stars. That work opened a new field of research which led in the recent years to several ICRANet publications on the properties of such magnetized white dwarfs, including their radiation emission which has been compared and contrasted with observations. It is particularly important to recall that this area of research has been very active and prolific thanks to an intense collaboration with Brazilian colleagues, including professors and postdoc former students at ICRANet. In the 2016 we have made two important contributions within this collaboration. First, in the work by D. L. Cáceres, et al., “Thermal X-ray emission from massive, fast rotating, highly magnetized white dwarfs”, MNRAS 465, 4434 (2016), it has been shown that suchwhite dwarfs can behave in a similar way as the well-known pulsars, with a specific emission in the X-rays which can explain the soft X-ray emission observed in SGRs and AXPs. Second, in the work by J. G. Coelho et al., “On the nature of some SGRs and AXPs as rotation-powered neutron stars”, A&A 599, A87 (2017), it has been shown that up to 11 out of the total 23 SGRs/AXPs known to date, could be described as rotation-powered neutron stars.
In 2020 major results have been obtained in the field of dark matter, which therefore became a main line of research independent from “Theoretical Astroparticle Physics”. We have given strong evidence on the nature of the massive compact source at the center of our Galaxy to be a concentration of dark matter made of fermions instead of a supermassive black hole. It is worth to say a few words on this important issue. The closest stars to the Galactic center have been extensively and continuously monitored over decades, leading to high-quality data of their positions and velocities. The explanation of these data, especially the S2 star motion, requires the presence of a compact source, Sagittarius A* (Sgr~A*), and its mass must be of the order of 4 million solar masses. This result has been protagonist of the awarded Nobel Prize in Physics 2020 to Reinhard Genzel and Andrea Ghez “for the discovery of a supermassive compact object at the centre of our galaxy”. Traditionally, the Sgr A* compact source has been assumed to be a supermassive black hole. However, a proof of its existence is still absent. A further challenge to this scenario has come from the G2 cloud motion data whose post-peripassage velocity is much lower than the prediction of the supermasive black hole scenario. An attempt to overcome this difficulty has introduced a friction force produced by an accretion flow, however, such a flow is also observationally unconfirmed. In a series of articles, published from 2015 to 2019, we have introduced the Ruffini-Argüelles-Rueda (RAR) model of dark matter. The RAR model proposed dark matter is made of massive fermions, herafter “darkinos”, and their distribution in galaxies is calculated assuming they are at finite temperatures, in thermodynamic equilibrium, and using general relativity. It was already clear from those works that the darkinos form a core-halo density profile, and that the dense core could produce effects on orbiting matter similar to the ones of a supermassive black hole of similar mass. In the year 2020, we moved forward by performing a detailed observational test of the theoretically predicted existence of the dense core of dark matter the Galactic center using the RAR model. Namely, we test whether the dark matter dense core could work as an alternative to the central black hole scenario for SgrA*. The outstanding result has been that the solely dark matter gravitational potential of darkinos of 56 kiloelectronvolt rest mass-energy (about one ninth of the electron mass), can explain all existing data of the motion of the star S2 as well as of the cloud G2, without the presence of a central black hole, and even with better accuracy. Our result that the center of our Galaxy could harbor a concentration of DM instead of a supermassive black hole has attracted worldwide attention. A Press Release of this result has been published in the Astronomy & Astrophysics journal: https://www.aanda.org/2020-press-releases/1880. It is also worth to mention the award Premio Estímulo en Astronomía “Dr. Jorge Sahade” received by Dr. Carlos R. Argüelles in Argentina, delivered by the National Academy of Physical and Natural Sciences, recognizing the relevance of these works as an advance in the field of dark matter: https://laplata.conicet.gov.ar/la-academia-nacional-de-ciencias-exactas-fisicas-y-naturales-distingue-a-un-investigador-del-conicet-la-plata/. The not-scientific audience has been also attracted by these novelties; indeed the major newspaper in Colombia, “El Tiempo”, dedicated a special article on September 9, 2020, to our results: https://www.eltiempo.com/vida/ciencia/que-hay-en-el-centro-de-la-galaxia-investigadores-aseguran-que-podria-ser-materia-oscura-536640. Our group is currently working on an extension of this work by analyzing all the existing observational data of the S-cluster stars, namely the orbit and velocity data of 17 stars. We expect to publish these results in a new article and will be presented in the Scientific Report of the year 2021. Our group has published three additional papers devoted to fermionic dark matter within the RAR model theoretical framework. We have performed a new analysis of NuSTAR mission X-ray data of the center of our Galaxy to constraint possible self-interactions of the darkinos, assuming they could be the sterile neutrinos of the minimal extension of the standard model of particles, and that they can radiatively decay emitting X-rays. We obtained new bounds on the self-interaction strength complementary to previous bounds we have presented in 2016 using the Milky Way rotation curves. Two additional articles focus on cosmological consequences of fermions of keV mass-energy as predicted in our research. The first paves the way to the possibility of performing numerical simulations on the formation of dark matter halos of these darkinos in cosmological evolution and structure formation models. Boltzmann hierarchies (time-evolution equations of a Boltzmann gas) including particle self-interactions are there obtained. The second work obtained a major result on the cosmological stability of these core-halo configurations, demonstrating they could naturally arise in the cosmological evolution being the ones that maximize the entropy and being stable over timescales of the order of the Hubble time. This gives certainly a great cosmological support to the fermionic dark matter hypothesis proposed by our group.
GRBs
have broaden the existing problematic of the study of Supernovae.
In some models, e.g. the “collapsar” one, all GRBs are assumed to
originate from supernovae. Within our approach, we assume that
core-collapse supernovae can only lead to neutron stars, and we also
assume that GRBs are exclusively generated in the collapse to a black
hole. Within this framework, supernovae and GRBs do necessarily
originate in a binary system composed by an evolved main sequence
star and a neutron star. The concept of
We have studied (Bini, Esposito, Geralico) cosmological models, involving non-ideal fluids as sources of the gravitational field, with equation of state typical for fluids undergoing phase transitions as a possible mechanism to generate the content of dark matter in the present Universe. We have continued our works on perturbations of black hole spacetimes (Bini, Damour, Geralico), with transcription of the associated results into the effective-one-body model, i.e. the model which encompasses all other approximation techniques for the description of a two-body system. In particular, we have studied the backreaction due to particles moving on eccentric orbits in Schwarzschild and Kerr spacetimes. Moreover, we have started the inclusion of second order perturbation effects into the effective-one-body model and considered gravitational self-force effects (Bini, Carvalho, Geralico) on a scalar charge orbiting a Reissner-Nordstrom spacetime. We have continued our studies (Bini, Geralico) on drag and friction forces around black hole spacetimes, motivated by the necessity of a deeper understanding of effects like the well known Poynting-Robertson effect. We have considered (Bini, Jantzen, Geralico) gyroscope precession effects along eccentric orbits (either bound or elliptic-like and unbound or hyperbolic-like) around a Kerr spacetime. Finally (Bini, Mashhoon) we have studied tidal forces around a Kerr black hole, with applications in gravitational gradiometry as well as some novel applications of nonlocal gravity to conformally flat spacetimes.
The work on classical rotating self-gravitating configurations characterized by a multi-parametric rotation law, written in collaboration with Dr F. Cipolletta, Dr J. Rueda and Prof. R. Ruffini, has been published. In the manuscript a detailed and elegant graphical analysis regarding the stability of the configurations (in particular against mass shedding) in the velocity field’s parameters’s space has been presented. In the general relativistic context, an article regarding the last stable orbit around neutron stars has been published. An interesting comparison between numerical simulations and analytical estimates in this case led the authors to find simple, accurate and especially analytical formulas of great interest for astrophysical applications. The study has been performed by using three different equations of state (EOS) based on nuclear relativistic mean field theory models but it is expected that the formulas found will be still valid also for other equations of state. Finally a “compare and contrast” procedure of these results with Kerr metric quantities has been performed too.
These researches have been focused in fluid-structure problems in hemodynamics in arbitrary Lagrangian-Eulerian formulation, a mathematically involved theory which describes systems of partial differential equations with free boundary conditions. Specifically the nonlinear equations’ set which describes the fluid and the elastic wall within which the fluid flows have been numerically integrated and the previously introduced TDB risk indicator has been applied to this more involved case in order to perform a risk assessment. On the other hand, a numerical analysis of the same mathematical problem, but focused on the case of different biomedical prostheses applied to real patients’ geometries has been carried out in order to perform a quantitative comparison of the mechanical behavior of the different scenarios, having in mind as ultimate target the best outcomes for patients’ health.
We
turn now
I would like to express, also on behalf of all Members of ICRANet, our gratitude to the Ministers of Foreign Affairs and to the Ministers of Economy and Finance of Italy, of Armenia, including also the State Committee of Science of Armenia, and Brazil for their support. I would also express the gratitude to the Vatican Secretary of State, to the Presidents of the Universities of Tucson and Stanford as well as to the President of ICRA for their support to the ICRANet activities. Particular recognition goes to Italian Foreign Minister for having supported ongoing ICRANet activities in Belarus, Iran, and Kazakhstan which, coordinated by Armenia, are opening new opportunities of Research in Central Asia. Equally important the support by local organizations to the traditional activities in China (Mainland) and China (Taiwan) and in Korea. I like as well to recall the further extensions of activities within Mexico, Colombia and Argentina, whose Universities and Research organizations have generously contributed trough the financial support of students and postdocs to the further expansion of ICRANet activities. For all this, a particular gratitude goes to Min. Fabrizio Nicoletti, to Cons. Enrico Padula and to Prof. Immacolata Pannone, of the Italian Ministry of Foreign Affairs and International Cooperation for their attention and constant support and advice. A special recognition goes to the activities of the many Ambassadors and Consuls who have greatly helped in the intense series of activities carried out by ICRANet in Belarus, Brazil, China, Colombia, Italy, Mexico. I also express the plaudit for the support of ongoing activities of the IRAP-PhD to the President of Université Côte d'Azur Prof. Jeanick Brisswalter, as well as to the Director of the Observatoire de la Côte D’Azur Prof. Thierry Lanz. We are grateful to the Mayor of Pescara, Carlo Masci, to the Mayor of Nice Christian Estrosi, to the President of PACA, Renaud Muselier, to the Cons. Agnès Rampal of PACA, to the President of the National Academy of Science of Armenia, Prof. Radik Martirosyan, and to the Director of CBPF in Rio de Janeiro, Prof. Ronald Shellard, for their generous support in granting to ICRANet the logistics of the Centers in their respective townships. Clearly, a special mention of satisfaction goes to all the Scientific Institutions and Research Centers which have signed with ICRANet a collaboration agreement. The complete list can be found at http://www.icranet.org/ScientificAgreements. ICRANet, as sponsor of the IRAP-PhD program, expresses its gratitude to AEI – Albert Einstein Institute – Potsdam (Germany), ASI – Agenzia Spaziale Italiana (Italy), Bremen University (Germany), Bucaramanga University (Colombia), Carl von Ossietzky University of Oldenburg (Germany), CBPF – Brazilian Centre for Physics Research (Brazil), CNR – Consiglio Nazionale delle Ricerche (Italy), Ferrara University (Italy), ICRA (Italy), INAF – Istituto Nazionale di Astrofisica (Italy), Indian centre for space physics (India), Institut Hautes Etudes Scientifiques – IHES (France), Inst. of High Energy Physics of the Chinese Academy of Science – IHEP-CAS, China, INPE (Instituto Nacional de Pesquisas Espaciais, Brasil), Max-Planck-Institut für Radioastronomie – MPIfR (Germany), National Academy of Science (Armenia), Observatory of the Côte d'Azur (France), Rome University – “Sapienza” (Italy), Savoie-Mont-Blanc University (France), Shanghai Astronomical Observatory (China), Stockholm University (Sweden), Tartu Observatory (Estonia), UAM – Universidad Autónoma Metropolitana (Mexico), Université Côte d'Azur (France) for their joint effort in creating and activating this first European Ph.D. program in Relativistic Astrophysics which has obtained the official recognition of the Erasmus Mundus program of the European Community. All these activities were achieved thanks to the dedicated work of Prof. Pascal Chardonnet. ICRANet looks forward to expand this past success and is ready to generalize it with the adhesion of the University of Science and Technology of China (USTC), member of ICRA. A special mention of gratitude, of course, goes to the Administrative, Secretarial and Technical staff of ICRANet and ICRA for their essential and efficient daily support and to all Faculty for their dedication to fostering, opening and teaching new scientific horizons in our knowledge of the Universe. |