Search results for "Gravity"
showing 10 items of 537 documents
On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology
2004
I discuss various ways in which CPT symmetry may be violated, and their phenomenology in current or immediate future experimental facilities, both terrestrial and astrophysical. Specifically, I discuss first violations of CPT symmetry due to the impossibility of defining a scattering matrix as a consequence of the existence of microscopic or macroscopic space-time boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological horizons due to the presence of a (positive) cosmological constant in the Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry, which may characterize certain approaches to quantum gravity, and third, I describe models of CPT non…
Matter, quantum gravity, and adiabatic phase
1990
Based on the observation that particle masses are much smaller than the Planck mass, a framework for the matter-gravity system in which matter follows gravitation adiabatically is examined in a path-integral approach. It is found that the equations that the resulting gravitational wave function satisfies involve, in addition to the expectation value of the matter stress tensor, an adiabatically induced gauge field which can lead to interesting topological structures in superspace. Such a non-trivial geometric contribution modifies the semiclassical quantization condition and can change the conserved quantities associated with the symmetries of the system. © 1990 The American Physical Societ…
Application of non-invasive seismic techniques for the characterisation of a gravity concrete dam
2020
The use of non-invasive investigation methods is becoming frequent as a support for the monitoring of water reservoirs and for the management of dam safety. In this context, geophysical techniques are much less invasive than geotechnical tests and allow to obtain two-dimensional or three-dimensional representations of the mechanical parameters of an engineering structure. A case of application of constrained inversion and joint interpretations of non-invasive seismic techniques is discussed, in order to monitor the Dirillo gravity concrete dam, in Sicily. To investigate the foundation soil, a stratigraphic borehole and a vertical seismic profile, carried out in the same hole, were used to c…
Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves
2016
AbstractVolcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencie…
The Argille Varicolori Unit of Lucania (Italy): a record offscraping and gravity sliding in the Mesozoic-Tertiary Lagonegro Basin, southern Apennines
2006
Detailed geological mapping and new stratigraphic and structural data collected in the Lucania area of the southern Apennines allowed us to assess the deformation history of 11 Monte-Corleto Perticara zone, in the High Agri Valley (Lucanian Apennines, southern Italy) where red and green shales (known as Argille Varicolori or Argille scagliose) crop out. Our observations suggest that: (1) 'chaotic' facies within the Argille Varicolori may be attributed to a broken formation generated by overthrusting of Apenninic Platform units onto already deformed Lagonegro basin strata; (2) gravity sliding phenomena at the thrust front enhanced the development of debris flow and the emplacement of olistos…
Adiabatic invariants drive rhythmic human motion in variable gravity.
2019
Voluntary human movements are stereotyped. When modeled in the framework of classical mechanics they are expected to minimize cost functions that may include energy, a natural candidate from a physiological point of view also. In time-changing environments, however, energy is no longer conserved---regardless of frictional energy dissipation---and it is therefore not the preferred candidate for any cost function able to describe the subsequent changes in motor strategies. Adiabatic invariants are known to be relevant observables in such systems, although they still need to be investigated in human motor control. We fill this gap and show that the theory of adiabatic invariants provides an ac…
The enhanced X-ray Timing and Polarimetry mission—eXTP
2019
In this paper we present the enhanced X-ray Timing and Polarimetry mission - eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to det…
Settling of dilute and semidilute fiber suspensions at finite Re
2007
The motion of tracer fibers settling in a suspension made optically transparent using an index-of refraction matching technique is studied as a function of concentration, aspect ratio, fluid viscosity, and fiber length distribution. At Re ∼ O (1), two different regimes of sedimentation are clearly identified. For small volume fractions we find that fibers settle with their long-axis preferentially in the horizontal state. With increasing volume fraction, fibers settle preferentially with their long-axis aligned in the direction of gravity. These findings are strikingly different than for those conducted with Re → 0 and qualitatively support the numerical simulations reported by Kuusela et a…
Relativistic simulations of rotational core collapse : II. Collapse dynamics and gravitational radiation
2002
We have performed hydrodynamic simulations of relativistic rotational supernova core collapse in axisymmetry and have computed the gravitational radiation emitted by such an event. Details of the methodology and of the numerical code have been given in an accompanying paper. We have simulated the evolution of 26 models in both Newtonian and relativistic gravity. Our simulations show that the three different types of rotational supernova core collapse and gravitational waveforms identified in previous Newtonian simulations (regular collapse, multiple bounce collapse, and rapid collapse) are also present in relativistic gravity. However, rotational core collapse with multiple bounces is only …
Lithosphere Structure, Heat Flow, Gravity, and Other Geoparameters in Central Europe
1991
To clarify structure and evolution of Central European lithosphere, an approach is taken which combines several methods: multivariate statistical data analysis and modelling of data sets, as geology, crustal structure, seismic travel times, heat flow, gravity, geoid heights, topography, vertical motions and unloading affects.