367 research outputs found
Complementarity Endures: No Firewall for an Infalling Observer
We argue that the complementarity picture, as interpreted as a reference
frame change represented in quantum gravitational Hilbert space, does not
suffer from the "firewall paradox" recently discussed by Almheiri, Marolf,
Polchinski, and Sully. A quantum state described by a distant observer evolves
unitarily, with the evolution law well approximated by semi-classical field
equations in the region away from the (stretched) horizon. And yet, a classical
infalling observer does not see a violation of the equivalence principle, and
thus a firewall, at the horizon. The resolution of the paradox lies in careful
considerations on how a (semi-)classical world arises in unitary quantum
mechanics describing the whole universe/multiverse.Comment: 11 pages, 1 figure; clarifications and minor revisions; v3: a small
calculation added for clarification; v4: some corrections, conclusion
unchange
Mobile phones as fomites for pathogenic microbes: A cross-sectional survey of perceptions and sanitization habits of health care workers in Dubai, United Arab Emirates
Backgrounds
In 2022, smartphone use continues to expand with the number of smartphone subscriptions surpassing 6 billion and forecasted to grow to 7.5 billion by 2026. The necessity of these ‘high touch’ devices as essential tools in professional healthcare settings carries great risks of cross-contamination between mobile phones and hands. Current research emphasises mobile phones as fomites enhancing the risk of nosocomial disease dissemination as phone sanitisation is often overlooked. To assess and report via a large-scale E-survey the handling practices and the use of phones by healthcare workers.
Methods
A total of 377 healthcare workers (HCWs) participated in this study to fill in an E-survey online consisting of 14 questions (including categorical, ordinal, and numerical data). Analysis of categorical data used non-parametric techniques such as Pearson's chi-squared test.
Results
During an 8-h shift, 92.8% (n/N = 350/377) use their phone at work with 84.6% (n/N = 319/377) considering mobile phones as an essential tool for their job. Almost all HCWs who participated in this survey believe their mobile phones could potentially harbour microorganisms (97.1%; n/N = 366/377). Fifty-seven respondents (15.1%) indicated that they use their phones while wearing gloves and 10.3% (n/N = 39/377) have never cleaned their phones. The majority of respondents (89.3%; n/N = 337/377) agreed that contaminated mobile phones could contribute to dissemination of SARS-CoV-2.
Conclusion
Mobile phone use is now almost universal and indispensable in healthcare. Medical staff believe mobile phones can act as fomites with a potential risk for dissemination of microbes including SARS-COV-2. There is an urgent call for the incorporation of mobile phone sanitisation in infection prevention protocol. Studies on the use of ultraviolet-C based phone sanitation devices in health care settings are needed
Limits of JT gravity
We construct various limits of JT gravity, including Newton-Cartan and
Carrollian versions of dilaton gravity in two dimensions as well as a theory on
the three-dimensional light cone. In the BF formulation our boundary conditions
relate boundary connection with boundary scalar, yielding as boundary action
the particle action on a group manifold or some Hamiltonian reduction thereof.
After recovering in our formulation the Schwarzian for JT, we show that
AdS-Carroll gravity yields a twisted warped boundary action. We comment on
numerous applications and generalizations.Comment: 41 pages, 3 figures, 1 table; v2: Matches published version +
Footnote 11; v3: Corrected typo in Carrollian/Galilean generalized dilaton
potentia
Comments on black holes I: The possibility of complementarity
We comment on a recent paper of Almheiri, Marolf, Polchinski and Sully who
argue against black hole complementarity based on the claim that an infalling
observer 'burns' as he approaches the horizon. We show that in fact
measurements made by an infalling observer outside the horizon are
statistically identical for the cases of vacuum at the horizon and radiation
emerging from a stretched horizon. This forces us to follow the dynamics all
the way to the horizon, where we need to know the details of Planck scale
physics. We note that in string theory the fuzzball structure of microstates
does not give any place to 'continue through' this Planck regime. AMPS argue
that interactions near the horizon preclude traditional complementarity. But
the conjecture of 'fuzzball complementarity' works in the opposite way: the
infalling quantum is absorbed by the fuzzball surface, and it is the resulting
dynamics that is conjectured to admit a complementary description.Comment: 34 pages, 6 figures, v3: clarifications & references adde
Thermal duality and gravitational collapse
Thermal duality is a relationship between the behaviour of het-erotic string models of the E(8)xE(8) or SO(32) types at inversely related temperatures, a variant of T duality in the Euclidean regime. This duality would have consequences for the nature of the Hagedorn transition in these string models. We propose that the vacuum admits a family of deformations in situations where there are closed surfaces of constant area but high radial acceleration (a string regularized ver-sion of a Penrose trapped surface), such as would be formed in situ-ations of extreme gravitational collapse. This would allow a radical resolution of the firewall paradox by allowing quantum effects to sig-nificantly modify the spacetime geometry around a collapsed object. A string bremsstrahlung process would convert the kinetic energy of infalling matter in extreme gravitational collapse to form a region of the deformed vacuum, which would be equivalent to forming a high temperature string phase. A heuristic criterion for the conversion pro-cess is presented, relating Newtonian gravity to the string tension, suggesting an upper limit to the strength of the gravitational interac-tion. This conversion process might have observable consequences for charged particles falling into a rotating collapsed object by producing high energy particles via a variant of the Penrose process
Higher dimensional generalisations of the SYK model
We discuss a 1+1 dimensional generalization of the Sachdev-Ye-Kitaev model.
The model contains Majorana fermions at each lattice site with a
nearest-neighbour hopping term. The SYK random interaction is restricted to low
momentum fermions of definite chirality within each lattice site. This gives
rise to an ordinary 1+1 field theory above some energy scale and a low energy
SYK-like behavior. We exhibit a class of low-pass filters which give rise to a
rich variety of hyperscaling behaviour in the IR. We also discuss another set
of generalizations which describes probing an SYK system with an external
fermion, together with the new scaling behavior they exhibit in the IR.Comment: 23 pages, 3 figures. Minor change
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