Scientific activities of the various Research Units

Napoli unit

-The units is interested to study theories of gravity by considering the role of curvature, torsion and topological invariants, as well as non-local terms. Specifically, the generalization of Einstein’s theory is considered in view of addressing astrophysical and cosmological issues such as accelerated expansion, large scale structure and, in general, of reconstructing a reliable cosmic history. In particular, we study cosmological features like cosmography and Cosmic Microwave Background in order to test models.

-Gravitational field theories, such as f(R, ◻R), f(T), f(R,,G), f(G,T), f(T,B) etc. are studied, focusing in particular on exact solutions of Noether symmetries and constraining the free parameters of the models with Cosmic Microwave background data and Large Scale Structure measurements. Furthermore, the theoretical foundations of these alternative approaches are studied by comparing the role played by affine connections, tetrads and metric in the dynamics of the gravitational field.

-In order to investigate the origin of the accelerated expansion of the Universe we study interacting dark matter/dark energy models. In particular, we want to understand whether this coupling can be connected to some symmetry, and compare high redshift observations with theoretical predictions in extended theory of gravity. Weare interested to develop an extended approach to the cosmographic technique in order to probe the expansion of the Universe at high redshift with new distance indicators, as Gamma Ray Bursts and Quasars.

- We study perturbations induced by scalar fields in a given gravitational background, generalizing recent results obtained by constraining the scalar field evolution according to an Ermakov-Pinney-like prescription (e.g., divergence-free property of the corresponding current). We focus on associated gauge-invariant variables, as well as on possible transcription of results into other formalisms, like gravitational self-force.

-Over the last years, a first step was done in defining both quantum and classical state of the universe in terms of tomographic functions. The next step is to see how the classical limits of quantum tomograms fit with the classical tomogram obtained with cosmographic techniques. Moreover, research has been started about the influence of torsion on gravitational waves in extended theories.

-We use weak lensing from wide astronomical survey to study the correlated distribution of large scale structure around a large sample of massive galaxy clusters. This represents a novel test for the LCDM model, as LCDM predictions appear to be at odds with our recent observational findings (see Sereno, Nature Astronomy, 2018) based on a limited sample of clusters.

-In order to understand the origin of dark energy and due to the lack of a widely accepted quantum gravity theory, we consider a new line of research where the cosmological constant is depicted in terms of a semi-classical model. There, Planckian fluctuations are averaged on a fixed physical scale L in terms of the Buchert formalism, but adapted to microscopic scales. We study of the above mentioned semi-classical model in terms of a renormalization-group approach, where a non-trivial stable infrared fixed point denotes the crossover to classicality.

-We consider a non-unitary, classically stable version of higher derivative (HD) gravity and focus on its Newtonian limit, which is a non-Markovian model with several appealing features. These include a built-in mechanism for the evolution of macroscopic coherent superpositions of states into ensembles of pure states and the primacy of the density matrix in describing the physical reality. Within this framework, we study, via numerical simulations, gravity induced thermalization properties of a mesoscopic crystal. The aim is to show how thermodynamics could emerge even in a closed system, by virtue of the fundamental non-unitary nature of the model.

-We analyze the semi-classical study of selected mesoscopic quantum systems, like Dirac-Weyl nanomaterials, interacting with gravity. Search for novel, possibly observable effects at nanoscales might provide a further test of General Relativity, also helping to unveil the quantum face of gravitation.

Salerno unit

- We analyze the effects of adding non-local cubic terms in the scalar curvature to the Lagrangian of modified gravity and study the consequences on amplitudes and the renormalizability of the model. More specifically, the aim is to understand whether the cubic curvature term could allow to improve the UV behavior of nonlocal gravity theories and make them well defined at any energy scale. In such a case, it is expected that the cubic term can cancel the enhancement contribution in the vertex coming from the quadratic curvature action.

-The limits of GR have led to the emergence of the `dark universe' scenario. In the last years, in fact, there have been evidences that, if cosmology is described by Einstein's field equations, then there should be a substantial amount of `dark matter' in the Universe. More recently, `dark energy' has also been found to be required in order to explain the apparent accelerating expansion of the Universe. Modified cosmology (for example, f(R, ◻R) f(T), f(R,,G), where R, T and G refer to scalar curvature, torsion and Gauss-Bonnet invariant, respectively) may be at play during the evolution of the Universe, not only in the late era, but also in the very early. In particular, it is accepted that non-standard cosmology may not only describe the early-time inflation and late-time acceleration but also may propose the unified consistent description of the Universe evolution in different epochs, from inflation and radiation/matter dominance to dark energy. We focus on study these aspects in the framework of CMB physics, which from the upcoming experiments (PLANCK, BICEP, etc.) is the main source of data about the early universe. Particular interest is devoted to the study of primordial gravitational waves from Inflation.

- The detection of gravitational waves by Advanced LIGO and Advanced Virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations and laboratory tests. Using the new results from various tests of General Relativity performed using the binary black hole signals, we investigate the propagation of gravitational waves in the context of different model of modified gravity, and then impose constraints on the free parameters. Moreover, the advent of the recent study of QNM, the astrophysical scenarios provide a promising laboratory for constraining, and eventually ruling out, extended theories of gravity.

-Quantum effects in curved spacetimes in different frameworks: 1) Violation of the equivalence principle and tests of theories beyond GR. 2) The vacuum energy effects (vacuum condensate) that might play a relevant role in various contexts. 3) The Casimir-like systems. 4) Entanglement of particles in non-trivial backgrounds. 5) Non local QFT at finite temperature in curved spacetime. Moreover, our IS is also interested in studying the interaction of particles mediated by axion or dark particles.

- The Salerno unit is strongly involved in several gravitational lensing searches. It participates in the Microlensing Science Investigation Team of the WFIRST mission by NASA, to be launched in 2025. In particular, it is responsible for the development of the codes for the magnification calculation, the modeling and interpretation of microlensing events. The purpose of the project is to find thousands of extrasolar planets, measure the remnant mass function and the number of black holes in our Galaxy. The Salerno unit has also developed analytical and numerical methods for the study of gravitational lensing by black holes in the strong deflection limit. With the new data coming from the Event Horizon Telescope and from the gravitational waves detection, we have the possibility to test General Relativity in strong fields through gravitational lensing effects.

Trieste unit

- The nature of dark matter. Experiments and observations are modifying our knowledge on this mistery of the universe. Rather than from theoretical first principle it seems clear that our investigation must start from the distribution of dark matter in galaxies and its entanglement with that of the luminous matter. The nature of the dark particle will be worked out by its interaction with standard model particles very likely much more complex than that of the WIMP paradigm.

- Galaxy formation . Due to a large number of new astrophysical data available in this period ,the galaxy formation and the subsequent evolution could be traced from the beginning. Properties such as the stellar and the halo mass functions once determined and followed from high redshift to the present will indicate us the cosmological importance of galaxy merging ,of the angular momentum , of the baryonic feedback and of the downsizing with redshift of the stellar component.

-Galaxy simulations. Special hydroninamic simultations are performed on galaxies and clusters with the turbolence specially trated will be the gauge for the observational properties of galaxies.

- Merging BH. There is a complex theorethical investigation on the number of binary stellar BHs that merged and produced Gravitational waves in all galaxies over the whole history of the Universe. The comparison with actual GW detection will give crucial important result on Cosmology and the Physics of Gravitation in very compact objects,