598 research outputs found
The likelihood for supernova neutrino analyses
We derive the event-by-event likelihood that allows to extract the complete
information contained in the energy, time and direction of supernova neutrinos,
and specify it in the case of SN1987A data. We resolve discrepancies in the
previous literature, numerically relevant already in the concrete case of
SN1987A data.Comment: 7 pages, 2 figures. Accepted for publication in PR
Earthquake induced floor accelerations on a high-rise building: Scale model tests on a shaking table
The paper discusses results of shaking table tests on an in-scale high-rise building model. The purpose was to calibrate a dynamic numerical model for multi-hazard analyses to investigate the effects of floor acceleration. Accelerations, because of vibration of non-structural elements, affect both the comfort and safety of people. The research investigates the acceleration effects of both seismic and wind forces on an aeroelastic in-scale model of a multi-story building. The paper discusses the first phase of experiments and gives results of floor accelerations induced by several different base seismic impulses. Structural analyses were first performed on the full-scale prototype to take soil-structure interaction into account. Subsequently the scale model was designed through aeroelastic scale laws. Shaking table experiments were then carried out under different base accelerations. The response of the model and, in particular, amplification of effects from base to top are discussed
Formation of quark phases in compact stars and SN explosion
We describe possible scenarios of quark deconfinement in compact stars and we
analyze their astrophysical implications. The quark deconfinement process can
proceed rapidly, as a strong deflagration, releasing a huge amount of energy in
a short time and generating an extra neutrino burst. If energy is transferred
efficiently to the surface, like e.g. in the presence of convective
instabilities, this burst could contribute to revitalize a partially failed SN
explosion. We discuss how the neutrino observations from SN1987A would fit in
this scenario. Finally, we focus on the fate of massive and rapidly rotating
progenitors, discussing possible time separations between the moment of the
core collapse and the moment of quark deconfinement. This mechanism can be at
the basis of the interpretation of gamma ray bursts in which lines associated
with heavy elements are present in the spectrum.Comment: 9 pages, 3 figures, Proceedings "6th International Conference on
Perspectives in Hadronic Physics", May 2008, Triest
Evaluation of site effects by means of 3D numerical modeling of the Palatine Hill, Roman Forum, and Coliseum archaeological area
In this study we perform 3D nonlinear analyses of seismic site response of the
Central Archaeological Area of Rome, which includes the Palatine Hill, Roman Forum, Circus
Maximus, and Coliseum. The geological bedrock of the study area is constituted by a Pliocene
marine sandy-clayey unit (MonteVaticano Formation, MVA). At top of this unit a continental Quaternary succession is superimposed. Previous studies available for this area (Pagliaroli et al. 2014a; Mancini et al. 2014; Moscatelli et al. 2014) enabled to define a detailed three-dimensional reconstruction of the subsoil conditions, characterized by complex surficial and buried morphology, lateral heterogeneities and dynamic properties of involved material, natural as well as anthropogenic.
The area of Rome is affected by earthquakes from different seismogenic districts: i) the
central Apennine mountain chain (D = 90–130km and M = 6.7–7.0); ii) the Colli Albani volcanic
district (D = 20km and M=5.5); iii) Rome area itself, which is characterized by rare, shallow,
low-magnitude events (M < 5). Both natural and artificial signals have been considered to define the input motion for the numerical modeling of the site response of the whole archeological area.
This was accomplished by means of the finite differences code FLAC3D. To evaluate the seismic hazard and, consequently, to assess possible priorities for seismic retrofitting of the monuments, contour maps of Housner intensity amplification ratio FH (defined as the ratio between Housner intensity at the top of the model and the corresponding input at the bedrock outcrop), are carried out. To cover the entire range of natural periods pertaining to the monuments in the examined area, FH was evaluated over three ranges of period: 0.1–0.5s, 0.5–1.0s, and 1.0–2.0s. Numerical results shown that: 1) within the range of periods 0.1–0.5s, high values of FH = 2.2–2.6 occur both in
correspondence of narrow valleys filled with soft alluvial deposits and at top of Palatine Hill; 2)
within the range of periods 0.5–1.0s, high values of FH occur in correspondence of the deepest valleys; 3) within the range of periods 1.0–2.0s, low values of FH occur except in correspondence of the deepest valleys.Results show a good agreement with the previous 2D numerical modeling and with the microzonation maps (Pagliaroli et al 2014a, b), even if interesting differences show up highlighting the usefulness of 3D modeling in such complex settings. Such results are significantly relevant for the monumental and archaeological heritage of this area, as it is highly vulnerable due to its old age and state of conservation
Superluminal neutrinos in long baseline experiments and SN1987a
Precise tests of Lorentz invariance in neutrinos can be performed using long
baseline experiments such as MINOS and OPERA or neutrinos from astrophysical
sources. The MINOS collaboration reported a measurement of the muonic neutrino
velocities that hints to super-luminal propagation, very recently confirmed at
6 sigma by OPERA. We consider a general parametrisation which goes beyond the
usual linear or quadratic violation considered in quantum-gravitational models.
We also propose a toy model showing why Lorentz violation can be specific to
the neutrino sector and give rise to a generic energy behaviour E^alpha, where
alpha is not necessarily an integer number. Supernova bounds and the preferred
MINOS and OPERA regions show a tension, due to the absence of shape distortion
in the neutrino bunch in the far detector of MINOS. The energy independence of
the effect has also been pointed out by the OPERA results.Comment: 22 pages, 7 figures; comment on Cherenkov emission added, version
matching JHEP published pape
Physical stratigraphy and geotechnical properties controlling the local seismic response in explosive volcanic settings: the Stracciacappa maar (central Italy)
Nowadays, policies addressed to prevention and mitigation of seismic risk need a consolidated methodology finalised to the assessment of local seismic response in explosive volcanic settings. The quantitative reconstruction of the subsoil model provides a key instrument to understand how the geometry and the internal architecture of outcropping and buried geological units have influence on the propagation of seismic waves. On this regard, we present a multidisciplinary approach in the test area of the Stracciacappa maar (Sabatini Volcanic District, central Italy), with the aim to reconstruct its physical stratigraphy and to discuss how subsoil heterogeneities control the 1D and 2D local seismic response in such a volcanic setting. We first introduce a new multidisciplinary dataset, including geological (fieldwork and log from a 45-m-thick continuous coring borehole), geophysical (electrical resistivity tomographies, single station noise measurements, and 2D passive seismic arrays), and geotechnical (simple shear tests performed on undisturbed samples) approaches. Then, we reconstruct the subsoil model for the Stracciacappa maar in terms of vertical setting and distribution of its mechanical lithotypes, which we investigate for 1D and 2D finite element site response analyses through the application of two different seismic scenarios: a volcanic event and a tectonic event. The numerical modelling documents a significant ground motion amplification (in the 1–1.5 Hz range) revealed for both seismic scenarios, with a maximum within the centre of the maar. The ground motion amplification is related to both 1D and 2D phenomena including lithological heterogeneity within the upper part of the maar section and interaction of direct S-waves with Rayleigh waves generated at edges of the most superficial lithotypes. Finally, we use these insights to associate the expected distribution of ground motion amplification with the physical stratigraphy of an explosive volcanic setting, with insights for seismic microzonation studies and local seismic response assessment in populated environments
Is there a problem with low energy SN1987A neutrinos?
(abridged) We study the low energy events observed by Kamiokande-II. We focus
on the event 6 of 6.3 MeV and also on the other events that at 1 sigma fall
below the energy threshold: events 3,4,10,12. The volume distribution is not a
uniform distribution at 3 sigma, that suggests the presence of background
events close or at the border of the volume used for the analysis, including
the events 3,4,10. We checked the expected energy distribution assuming that
the signal is due to nubar(e)p-->e+n and that the average antineutrino energy
is 14 MeV. The agreement with the observations is not perfect but it is
acceptable at the 11 % confidence level if we include the peak of low energy
background events; otherwise, we face a 2.9 sigma problem. The expected energy
distribution implies that the evidence for supernova neutrinos is at 10 sigma
and that 1-3 background events are plausible. This conclusion does not change
strongly when we model the time distribution of the signal taking into account
the presence of an initial luminous phase of neutrino emission. This suggests
however that some of the early events are due to supernova neutrinos and not to
background. In summary, we formulate the hypothesis that some of the observed
low energy events are due to background and that some among them belong to a
peculiar phase of emission, that could be further characterized by low energy
neutrinos. Such an interpretation diminishes to a minimum the postulated number
of background events and thus improves the agreement between the a priori and
the a posteriori expectations on the number of background events. We argue on
these grounds that there is no significant disagreement between the average
energy of the supernova neutrinos seen in Kamiokande-II and the conventional
expectations.Comment: 28 pages, 4 figures. V3: relevance of the time distribution for the
interpretation of low energy events and improved analysis of backgroun
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