Time filter

Source Type

Khoa V.A.,Gran Sasso Science Institute
Comptes Rendus - Mecanique | Year: 2017

We derive in this Note a high-order corrector estimate for the homogenization of a microscopic semi-linear elliptic system posed in perforated domains. The major challenges are the presence of nonlinear volume and surface reaction rates. This type of correctors justifies mathematically the convergence rate of formal asymptotic expansions for the two-scale homogenization settings. As the main tool, we use energy-like estimates to investigate the error estimate between the micro and macro concentrations and between the corresponding micro- and macro-concentration gradients. This work aims at generalizing the results reported in © 2017 Académie des sciences.


Mazzon A.,Gran Sasso Science Institute | Pascucci A.,University of Bologna
Journal of Computational Finance | Year: 2017

We introduce an approximation of forward-start options in a multi-factor local-stochastic volatility model. We derive explicit expansion formulas for the so-called forward implied volatility, which can be useful to price complex path-dependent options as cliquets. The expansion involves only polynomials and can be computed without the need for numerical procedures or special functions. Recent results on the exploding behavior of the forward smile in the Heston model are confirmed and generalized to a wider class of local-stochastic volatility models. We illustrate the effectiveness of the technique through some numerical tests. © 2017 Incisive Risk Information (IP) Limited.


Palladino A.,Gran Sasso Science Institute | Pagliaroli G.,National Institute of Nuclear Physics, Italy | Villante F.L.,National Institute of Nuclear Physics, Italy | Villante F.L.,University of L'Aquila | And 2 more authors.
Physical Review Letters | Year: 2015

We analyze the high-energy neutrino events observed by IceCube, aiming to probe the initial flavor of cosmic neutrinos. We study the track-to-shower ratio of the subset with energy above 60 TeV, where the signal is expected to dominate, and show that different production mechanisms give rise to different predictions even accounting for the uncertainties due to neutrino oscillations. We include for the first time the passing muons observed by IceCube in the analysis. They corroborate the hypotheses that cosmic neutrinos have been seen and their flavor matches expectations derived from the neutrino oscillations. © 2015 American Physical Society.


Dell'Oro S.,Gran Sasso Science Institute | Marcocci S.,Gran Sasso Science Institute | Vissani F.,National Institute of Nuclear Physics, Italy
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The hypothesis that the Majorana mass of ordinary neutrinos dominates the rate of neutrinoless double beta decay is investigated. Predictions from neutrino oscillations are updated. Nuclear uncertainties are discussed, evaluating the impact of the quenching of the axial vector coupling constant in the nuclear medium, recently pointed out by Iachello et al. [Phys. Rev. C 87, 014315 (2013)]. Also, the sensitivity of present and future experiments is assessed, and possible implications of the knowledge on neutrino masses from cosmology are studied. The predictions from neutrino oscillations are compared with the results from cosmology and from neutrinoless double beta decay searches, emphasizing the important role of the measurement errors. The obstacles to an experimental determination of the Majorana phases are pointed out. © 2014 American Physical Society.


Bertolini S.,International School for Advanced Studies | Maiezza A.,University of Valencia | Nesti F.,Ruder Boskovic Institute | Nesti F.,Gran Sasso Science Institute
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We revisit the ΔF=2 transitions in the K and Bd,s neutral meson systems in the context of the minimal left-right symmetric model. We take into account, in addition to up-to-date phenomenological data, the contributions related to the renormalization of the flavor-changing neutral Higgs tree-level amplitude. These contributions were neglected in recent discussions, albeit formally needed in order to obtain a gauge-independent result. Their impact on the minimal LR model is crucial and twofold. First, the effects are relevant in B meson oscillations, for both CP conserving and CP violating observables, so that for the first time these imply constraints on the LR scenario which compete with those of the K sector (plagued by long-distance uncertainties). Second, they sizably contribute to the indirect kaon CP violation parameter . We discuss the bounds from B and K mesons in both cases of LR symmetry: generalized parity (P) and charge conjugation (C). In the case of P, the interplay between the CP-violation parameters and ′ leads us to rule out the regime of very hierarchical bidoublet vacuum expectation values v2/v1


Senjanovic G.,Gran Sasso Science Institute | Senjanovic G.,International Center for Theoretical Physics | Tello V.,Gran Sasso Science Institute
Physical Review Letters | Year: 2015

We give exact formulas for the right-handed analog of the Cabibbo-Kobayashi-Maskawa (CKM) matrix in the minimal left-right symmetric theory, for the case when the left-right symmetry is generalized parity as in the original version of the theory. We derive its explicit form and give a physical reason for the known and surprising fact that the right-handed mixing angles are close to the CKM ones, in spite of the left-right symmetry being badly broken in nature. We exemplify our results on the production of the right-handed charged gauge boson and the computation of KL-KS mass difference. © 2015 American Physical Society.


Nesti F.,Gran Sasso Science Institute | Salucci P.,International School for Advanced Studies
Journal of Cosmology and Astroparticle Physics | Year: 2013

We derive the mass model of the Milky Way (MW), crucial for Dark Matter (DM) direct and indirect detection, using recent data and a cored dark matter (DM) halo profile, which is favoured by studies of external galaxies. The method used consists in fitting a spherically symmetric model of the Galaxy with a Burkert DM halo profile to available data: MW terminal velocities in the region inside the solar circle, circular velocity as recently estimated from maser star forming regions at intermediate radii, and velocity dispersions of stellar halo tracers for the outermost Galactic region. The latter are reproduced by integrating the Jeans equation for every modeled mass distribution, and by allowing for different velocity anisotropies for different tracer populations. For comparison we also consider a Navarro-Frenk-White profile. We find that the cored profile is the preferred one, with a shallow central density of ρH ∼ 4 × 107M⊙/kpc 3 and a large core radius RH ∼ 10 kpc, as observed in external spirals and in agreement with the mass model underlying the Universal Rotation Curve of spirals. We describe also the derived model uncertainties, which are crucially driven by the poorly constrained velocity dispersion anisotropies of halo tracers. The emerging cored DM distribution has implications for the DM annihilation angular profile, which is much less boosted in the Galactic center direction with respect to the case of the standard ΛCDM, NFW profile. Using the derived uncertainties we discuss finally the limitations and prospects to discriminate between cored and cusped DM profile with a possible observed diffuse DM annihilation signal. The present mass model aims to characterize the present-day description of the distribution of matter in our Galaxy, which is needed to frame current crucial issues of Cosmology, Astrophysics and Elementary Particles. © 2013 IOP Publishing Ltd and Sissa Medialab srl.


Taylor A.M.,Dublin Institute for Advanced Studies | Gabici S.,University Paris Diderot | Aharonian F.,Dublin Institute for Advanced Studies | Aharonian F.,Max Planck Institute for Nuclear Physics | Aharonian F.,Gran Sasso Science Institute
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Recent IceCube results suggest that the first detection of very high energy astrophysical neutrinos have been accomplished. We consider these results at face value in a Galactic origin context. Emission scenarios from both the Fermi bubble and broader halo region are considered. We motivate that such an intensity of diffuse neutrino emission could be Galactic in origin if it is produced from an outflow into the halo region. This scenario requires cosmic ray transport within the outflow environment to be different to that inferred locally within the disk and that activity in the central part of the Galaxy accelerates cosmic rays to trans-"knee" energies before they escape into an outflow. The presence of a large reservoir of gas in a very extended halo around the Galaxy, recently inferred from x-ray observations, implies that the relatively modest acceleration power of 1039 erg s-1 in PeV energy cosmic rays may be sufficient to explain the observed neutrino flux. Such a luminosity is compatible with that required to explain the observed intensity of cosmic rays around the knee. © 2014 American Physical Society.


Bossa M.,Gran Sasso Science Institute
Journal of Instrumentation | Year: 2014

The existence of dark matter is inferred from gravitational effects, but its nature remains a deep mystery. One possibility, motivated by considerations in elementary particle physics, is that dark matter consists of elementary particles, such as the hypothesized Weakly Interacting Massive Particles (WIMPs), with mass ∼ 100 GeV and cross-section ∼ 10-47 cm2, that can be gravitationally trapped inside our galaxy and revealed by their scattering on nuclei. It should be possible to detect WIMPs directly, as the orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nucleus collisions of sufficient energy to be observable in the laboratory. The DarkSide-50 experiment is a direct WIMP search using a Liquid Argon Time Projection Chamber (LAr-TPC) with an active mass of 50 kg with a high sensitivity and an ultra-low background detector. © 2014 IOP Publishing Ltd and Sissa Medialab srl.


News Article | August 31, 2016
Site: www.nature.com

A devastating 6.2-magnitude earthquake in central Italy on 24 August that killed more than 290 people was the country’s largest since a magnitude-6.3 earthquake in 2009 that hit the town of L’Aquila, about 40 kilometres away. That event killed 308 people, destroyed tens of thousands of homes and a university. Controversially, it also caused six scientists to be put on trial for manslaughter. Central Italy’s complex geological and tectonic make-up creates a notorious quake risk. The Adria micro-plate dives beneath the Apennine mountain range from east to west, creating seismic strain. The mighty Eurasian and African plates also collide here, with the Eurasian plate moving northeast at 24 millimetres per year. The latest quake also injured hundreds and laid waste to historic villages in the Apennine mountains, including Amatrice (see ‘Epicentre of a quake’). It was a result of increased horizontal stress perpendicular to the mountain chain. Seismologists had expected a rupture to occur near the location at any time. Still, Giulio Selvaggi, a research director at the National Institute of Geophysics and Volcanology in Rome, and one of those initially convicted of manslaughter — all six were cleared on appeal — says he was shocked by the death and destruction wreaked by last week’s quake. The mountainous region around Amatrice is sparsely populated, but the final death toll may exceed that of more populated and urbanized L’Aquila. Selvaggi seconds a public outcry over the failure of authorities to prioritize making old buildings more earthquake-resistant and notes that his team supplies earthquake maps to them. “We scientists have made a beautiful, detailed seismic hazard map, showing clearly the areas in greatest need of preventive measures,” he says. “But public authorities don’t take enough action.” The court case over the L’Aquila earthquake came about because a local amateur researcher claimed to have evidence of an imminent, large quake. Six scientists and one government official who had publicly dismissed the amateur’s methods were accused of misinforming the public. Following an unprecedented trial, all seven were given six-year jail sentences for manslaughter, but the scientists were cleared on appeal in 2014. Computer scientist Paola Inverardi, who is rector of the university in L’Aquila, says the rebuilding of the university is nearly complete, and that research activities had resumed by 2012. Science in the region has also benefited from supporting initiatives following the quake, she says. One of these is the Gran Sasso Science Institute, an international graduate school founded in 2012 to inject young intellectual life into L’Aquila. It has been so successful that in June it was awarded university status. Unlike the earthquake in L’Aquila, which was preceded by frequent, mostly low-magnitude, tremors in the surrounding area, no seismic activity was recorded before the latest earthquake. “It came out of the blue, without the preceding tremors we experienced in ‘our’ earthquake,” says Inverardi. L’Aquila itself experienced virtually no damage, but, she says, “psychologically we were all pushed back”.

Loading Gran Sasso Science Institute collaborators
Loading Gran Sasso Science Institute collaborators