25 research outputs found
Entanglement Entropy and Mutual Information Production Rates in Acoustic Black Holes
A method to investigate acoustic Hawking radiation is proposed, where
entanglement entropy and mutual information are measured from the fluctuations
of the number of particles. The rate of entropy radiated per one-dimensional
(1D) channel is given by , where is the sound
acceleration on the sonic horizon. This entropy production is accompanied by a
corresponding formation of mutual information to ensure the overall
conservation of information. The predictions are confirmed using an \emph{ab
initio} analytical approach in transonic flows of 1D degenerate ideal Fermi
fluids.Comment: 4 pages, 1 figure. Supplemental Material (pdf) included in the source
of this manuscrip
Acoustic black holes in a two-dimensional "photon-fluid"
Optical field fluctuations in self-defocusing media can be described in terms
of sound waves in a 2D photon-fluid. It is shown that, while the background
fluid couples with the usual flat metric, sound-like waves experience an
effective curved spacetime determined by the physical properties of the flow.
In an optical cavity configuration, the background spacetime can be suitably
controlled by the driving beam allowing the formation of acoustic ergoregions
and event horizons. An experiment simulating the main features of the rotating
black hole geometry is proposed.Comment: revised versio
Back-reaction effects in acoustic black holes
Acoustic black holes are very interesting non-gravitational objects which can
be described by the geometrical formalism of General Relativity. These models
can be useful to experimentally test effects otherwise undetectable, as for
example the Hawking radiation. The back-reaction effects on the background
quantities induced by the analogue Hawking radiation could be the key to
indirectly observe it. We briefly show how this analogy works and derive the
backreaction equations for the linearized quantum fluctuations in the
background of an acoustic black hole. A first order in hbar solution is given
in the near horizon region. It indicates that acoustic black holes, unlike
Schwarzschild ones, get cooler as they radiate phonons. They show remarkable
analogies with near-extremal Reissner-Nordstrom black holes.Comment: 10 pages, 1 figure; Talk given at the conference ``Constrained
Dynamics and Quantum Gravity (QG05)", Cala Gonone (Italy), September 200
Towards an S-matrix Description of Gravitational Collapse
Extending our previous results on trans-Planckian () scattering
of light particles in quantum string-gravity we present a calculation of the
corresponding S-matrix from the region of large impact parameters () down to the regime where classical gravitational collapse
is expected to occur. By solving the semiclassical equations of a previously
introduced effective-action approximation, we find that the perturbative
expansion around the leading eikonal result diverges at a critical value , signalling the onset of a new (black-hole related?)
regime. We then discuss the main features of our explicitly unitary S-matrix --
and of the associated effective metric -- down to (and in the vicinity of) , and present some ideas and results on its extension all the way to the region. We find that for the physical field solutions are
complex-valued and the S-matrix shows additional absorption, related to a new
production mechanism. The field solutions themselves are, surprisingly,
everywhere regular, suggesting a quantum-tunneling -- rather than a
singular-geometry -- situation.Comment: 39 pages, 5 figures; added discussion sect. 7, added references,
acknowledgement
An urgent call to think globally and act locally on landfill disposable plastics under and after covid-19 pandemic: pollution prevention and technological (Bio) remediation solutions
Landfilling and illegal waste disposal have risen to deal with the COVID-19 potentially infectious waste, particularly in developing countries, which aggravates plastic pollution and inherent environmental threats to human and animal health. It is estimated that 3.5 million metric tonnes of masks (equivalent to 601 TIR containers) have been landfilled worldwide in the first year, with the potential to increase global plastic municipal solid waste by 3.5%, alter biogas composition, and release 2.3 × 1021 microplastics to leachates or adjacent environments, in the coming years. This paper reviews the challenges raised in the pandemic scenario on landfills and discusses the potential environmental and health implications that might drive us apart from the 2030 U.N. sustainable goals. Also, it highlights some innovative technologies to improve waste management (from collection to disposal, waste reduction, sterilization) and mitigates plastic leakage (emission control approaches, application of biotechnological and monitoring/computational tools) that can pave the way to environmental recovery. COVID-19 will eventually subside, but if no action is taken in the short-term towards effective plastic policies, replacement of plastics for sustainable alternatives (e.g., biobased plastics), improvement of waste management streams (prioritising flexible and decentralized approaches), and a greater awareness and responsibility of the general public, stakeholders, industries; we will soon reach a tipping-point in natural environments worldwide.publishe
Gender-specific anthropometric markers of adiposity, metabolic syndrome and visceral adiposity index (VAI) in patients with obstructive sleep apnea
Obstructive sleep apnea often coexists with visceral adiposity and metabolic syndrome. In this study, we analysed gender-related differences in anthropometrics according to sleep apnea severity and metabolic abnormalities. In addition, the visceral adiposity index, a recently introduced marker of cardiometabolic risk, was analysed. Consecutive subjects with suspected obstructive sleep apnea (n = 528, 423 males, mean age ± standard deviation: 51.3 ± 12.8 years, body mass index: 31.0 ± 6.2 kg m(-2) ) were studied by full polysomnography (apnea-hypopnea index 43.4 ± 27.6 h(-1) ). Variables of general and visceral adiposity were measured (body mass index, neck, waist and hip circumferences, waist-to-hip ratio). The visceral adiposity index was calculated, and metabolic syndrome was assessed (NCEP-ATP III criteria). The sample included controls (apnea-hypopnea index 30 h(-1) , n = 329). When anthropometric variables were entered in stepwise multiple regression, body mass index, waist circumference and diagnosis of metabolic syndrome were associated with the apnea-hypopnea index in men (adjusted R(2) = 0.308); by contrast, only hip circumference and height-normalized neck circumference were associated with sleep apnea severity in women (adjusted R(2) = 0.339). These results changed little in patients without metabolic syndrome; conversely, waist circumference was the only correlate of apnea-hypopnea index in men and women with metabolic syndrome. The visceral adiposity index increased with insulin resistance, but did not predict sleep apnea severity. These data suggest gender-related interactions between obstructive sleep apnea, obesity and metabolic abnormalities. The visceral adiposity index was a good marker of metabolic syndrome, but not of obstructive sleep apnea