4,662 research outputs found
Warped Convolutions, Rieffel Deformations and the Construction of Quantum Field Theories
Warped convolutions of operators were recently introduced in the algebraic
framework of quantum physics as a new constructive tool. It is shown here that
these convolutions provide isometric representations of Rieffel's strict
deformations of C*-dynamical systems with automorphic actions of R^n, whenever
the latter are presented in a covariant representation. Moreover, the device
can be used for the deformation of relativistic quantum field theories by
adjusting the convolutions to the geometry of Minkowski space. The resulting
deformed theories still comply with pertinent physical principles and their
Tomita-Takesaki modular data coincide with those of the undeformed theory; but
they are in general inequivalent to the undeformed theory and exhibit different
physical interpretations.Comment: 34 page
An operator expansion for integrable quantum field theories
A large class of quantum field theories on 1+1 dimensional Minkowski space,
namely, certain integrable models, has recently been constructed rigorously by
Lechner. However, the construction is very abstract and the concrete form of
local observables in these models remains largely unknown. Aiming for more
insight into their structure, we establish a series expansion for observables,
similar but not identical to the well-known form factor expansion. This
expansion will be the basis for a characterization and explicit construction of
local observables, to be discussed elsewhere. Here, we establish the expansion
independent of the localization aspect, and analyze its behavior under
space-time symmetries. We also clarify relations with deformation methods in
quantum field theory, specifically, with the warped convolution in the sense of
Buchholz and Summers.Comment: minor corrections and clarifications, as published in J. Phys A; 24
page
Deformations of Fermionic Quantum Field Theories and Integrable Models
Considering the model of a scalar massive Fermion, it is shown that by means
of deformation techniques it is possible to obtain all integrable quantum field
theoretic models on two-dimensional Minkowski space which have factorizing
S-matrices corresponding to two-particle scattering functions S_2 satisfying
S_2(0) = -1. Among these models there is for example the Sinh-Gordon model. Our
analysis provides a complement to recent developments regarding deformations of
quantum field theories. The deformed model is investigated also in higher
dimensions. In particular, locality and covariance properties are analyzed.Comment: 20 page
Drought severity–duration–frequency curves: a foundation for risk assessment and planning tool for ecosystem establishment in post-mining landscapes
Eastern Australia has considerable mineral and energy resources, with areas of high biodiversity value co-occurring over a broad range of agro-climatic environments. Lack of water is the primary abiotic stressor for (agro)ecosystems in many parts of eastern Australia. In the context of mined land rehabilitation quantifying the severity–duration–frequency (SDF) of droughts is crucial for successful ecosystem rehabilitation to overcome challenges of early vegetation establishment and long-term ecosystem resilience.
The objective of this study was to quantify the SDF of short-term and long-term drought events of 11 selected locations across a broad range of agro-climatic environments in eastern Australia by using three drought indices at different timescales: the Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), and the Standardized Precipitation-Evapotranspiration Index (SPEI). Based on the indices we derived bivariate distribution functions of drought severity and duration, and estimated the recurrence intervals of drought events at different timescales. The correlation between the simple SPI and the more complex SPEI or RDI was stronger for the tropical and temperate locations than for the arid locations, indicating that SPEI or RDI can be replaced by SPI if evaporation plays a minor role for plant available water (tropics). Both short-term and long-term droughts were most severe and prolonged, and recurred most frequently in arid regions, but were relatively rare in tropical and temperate regions.
Our approach is similar to intensity–duration–frequency (IDF) analyses of rainfall, which are crucial for the design of hydraulic infrastructure. In this regard, we propose to apply SDF analyses of droughts to design ecosystem components in post-mining landscapes. Together with design rainfalls, design droughts should be used to assess rehabilitation strategies and ecological management using drought recurrence intervals, thereby minimising the risk of failure of initial ecosystem establishment due to ignorance of fundamental abiotic and site-specific environmental barriers, such as flood and drought events
Wedge-Local Quantum Fields and Noncommutative Minkowski Space
Within the setting of a recently proposed model of quantum fields on
noncommutative Minkowski spacetime, the consequences of the consistent
application of the proper, untwisted Poincare group as the symmetry group are
investigated. The emergent model contains an infinite family of fields which
are labelled by different noncommutativity parameters, and related to each
other by Lorentz transformations. The relative localization properties of these
fields are investigated, and it is shown that to each field one can assign a
wedge-shaped localization region of Minkowski space. This assignment is
consistent with the principles of covariance and locality, i.e. fields
localized in spacelike separated wedges commute.
Regarding the model as a non-local, but wedge-local, quantum field theory on
ordinary (commutative) Minkowski spacetime, it is possible to determine
two-particle S-matrix elements, which turn out to be non-trivial. Some partial
negative results concerning the existence of observables with sharper
localization properties are also obtained.Comment: Version to appear in JHEP, 27 page
Deformations of quantum field theories on de Sitter spacetime
Quantum field theories on de Sitter spacetime with global U(1) gauge symmetry
are deformed using the joint action of the internal symmetry group and a
one-parameter group of boosts. The resulting theory turns out to be wedge-local
and non-isomorphic to the initial one for a class of theories, including the
free charged Dirac field. The properties of deformed models coming from
inclusions of CAR-algebras are studied in detail.Comment: 26 pages, no figure
Gate-controlled superconductivity in diffusive multiwalled carbon nanotube
We have investigated electrical transport in a diffusive multiwalled carbon
nanotube contacted using superconducting leads made of Al/Ti sandwich
structure. We find proximity-induced superconductivity with measured critical
currents up to I_cm = 1.3 nA, tunable by gate voltage down to 10 pA. The
supercurrent branch displays a finite zero bias resistance which varies as R_0
proportional to I_cm^-alpha with alpha=0.74. Using IV-characteristics of
junctions with phase diffusion, a good agreement is obtained with Josephson
coupling energy in the long, diffusive junction model of A.D Zaikin and G.F.
Zharkov (Sov. J. Low Temp. Phys. 7, 184 (1981)).Comment: 5 pages, 4 figure
Telemedicine and Telementoring in Rhinology, Otology, and Laryngology: A Scoping Review
Objective: Telemedicine and telementoring have had a significant boost across all medical and surgical specialties over the last decade and especially during the COVID-19 pandemic. The aim of this scoping review is to synthesize the current use of telemedicine and telementoring in otorhinolaryngology and head and neck surgery. Data Sources: PubMed and Cochrane Library. Review Methods: A scoping review search was conducted, which identified 469 articles. Following full-text screening by 2 researchers, 173 articles were eligible for inclusion and further categorized via relevant subdomains. Conclusions: Virtual encounters and telementoring are the 2 main applications of telemedicine in otolaryngology. These applications can be classified into 7 subdomains. Different ear, nose, and throat subspecialties utilized certain telemedicine applications more than others; for example, almost all articles on patient engagement tools are rhinology based. Overall, telemedicine is feasible, showing similar concordance when compared with traditional methods; it is also cost-effective, with high patient and provider satisfaction. Implications for Practice: Telemedicine in otorhinolaryngology has been widely employed during the COVID-19 pandemic and has a huge potential, especially with regard to its distributing quality care to rural areas. However, it is important to note that with current exponential use, it is equally crucial to ensure security and privacy and integrate HIPAA-compliant systems (Health Insurance Portability and Accountability Act) in the big data era. It is expected that many more applications developed during the pandemic are here to stay and will be refined in years to come
A sharpened nuclearity condition for massless fields
A recently proposed phase space condition which comprises information about
the vacuum structure and timelike asymptotic behavior of physical states is
verified in massless free field theory. There follow interesting conclusions
about the momentum transfer of local operators in this model.Comment: 13 pages, LaTeX. As appeared in Letters in Mathematical Physic
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