1,285 research outputs found
Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals
A time-resolved analysis of the amplitude and phase of THz pulses propagating
through three-dimensional photonic crystals is presented. Single-cycle pulses
of THz radiation allow measurements over a wide frequency range, spanning more
than an octave below, at and above the bandgap of strongly dispersive photonic
crystals. Transmission data provide evidence for slow group velocities at the
photonic band edges and for superluminal transmission at frequencies in the
gap. Our experimental results are in good agreement with
finite-difference-time-domain simulations.Comment: 7 pages, 11 figure
Effective gravity from a quantum gauge theory in Euclidean space-time
We consider a gauge theory in an Euclidean -dimensional
space-time, which is known to be renormalizable to all orders in perturbation
theory for . Then, with the help of a space-time representation of
the gauge group, the gauge theory is mapped into a curved space-time with
linear connection. Further, in that mapping the gauge field plays the role of
the linear connection of the curved space-time and an effective metric tensor
arises naturally from the mapping. The obtained action, being quadratic in the
Riemann-Christoffel tensor, at a first sight, spoils a gravity interpretation
of the model. Thus, we provide a sketch of a mechanism that breaks the
color invariance and generates the Einstein-Hilbert term, as well as a
cosmological constant term, allowing an interpretation of the model as a
modified gravity in the Palatini formalism. In that sense, gravity can be
visualized as an effective classical theory, originated from a well defined
quantum gauge theory. We also show that, in the four dimensional case, two
possibilities for particular solutions of the field equations are the de Sitter
and Anti de Sitter space-times.Comment: 20 pages; Final version accepted for publication in Class.Quant.Gra
Congenital Chagas’ disease transmission in the United States: Diagnosis in adulthood
Two brothers with congenitally-acquired Chagas’ disease (CD) diagnosed during adulthood are reported. The patients were born in the USA to a mother from Bolivia who on subsequent assessment was found to be serologically positive for Trypanosoma cruzi. Serologic screening of all pregnant women who migrated from countries with endemic CD is strongly recommended
Fractional oscillator process with two indices
We introduce a new fractional oscillator process which can be obtained as
solution of a stochastic differential equation with two fractional orders.
Basic properties such as fractal dimension and short range dependence of the
process are studied by considering the asymptotic properties of its covariance
function. The fluctuation--dissipation relation of the process is investigated.
The fractional oscillator process can be regarded as one-dimensional fractional
Euclidean Klein-Gordon field, which can be obtained by applying the Parisi-Wu
stochastic quantization method to a nonlocal Euclidean action. The Casimir
energy associated with the fractional field at positive temperature is
calculated by using the zeta function regularization technique.Comment: 32 page
Operational Dynamic Modeling Transcending Quantum and Classical Mechanics
We introduce a general and systematic theoretical framework for Operational
Dynamic Modeling (ODM) by combining a kinematic description of a model with the
evolution of the dynamical average values. The kinematics includes the algebra
of the observables and their defined averages. The evolution of the average
values is drawn in the form of Ehrenfest-like theorems. We show that ODM is
capable of encompassing wide ranging dynamics from classical non-relativistic
mechanics to quantum field theory. The generality of ODM should provide a basis
for formulating novel theories.Comment: 23 pages and 2 figures. Sec. VII B "Phase Space Representation in
Curvilinear Coordinates" was correcte
The Dynamical Behaviour of Test Particles in a Quasi-Spherical Spacetime and the Physical Meaning of Superenergy
We calculate the instantaneous proper radial acceleration of test particles
(as measured by a locally defined Lorentzian observer) in a Weyl spacetime,
close to the horizon. As expected from the Israel theorem, there appear some
bifurcations with respect to the spherically symmetric case (Schwarzschild),
which are explained in terms of the behaviour of the superenergy, bringing out
the physical relevance of this quantity in the study of general relativistic
systems.Comment: 14 pages, Latex. 4 figures. New references added. Typos corrected. To
appear in Int. J. Theor. Phy
Taxing the Informal Economy: The Current State of Knowledge and Agendas for Future Research
This paper reviews the literature on taxation of the informal economy, taking stock of key debates
and drawing attention to recent innovations. Conventionally, the debate on whether to tax has frequently focused
on the limited revenue potential, high cost of collection, and potentially adverse impact on small firms. Recent
arguments have increasingly emphasised the more indirect benefits of informal taxation in relation to economic
growth, broader tax compliance, and governance. More research is needed, we argue, into the relevant costs and
benefits for all, including quasi-voluntary compliance, political and administrative incentives for reform, and
citizen-state bargaining over taxation
Graphene-based Wireless Agile Interconnects for Massive Heterogeneous Multi-chip Processors
The main design principles in computer architecture have recently shifted from a monolithic scaling-driven approach to the development of heterogeneous architectures that tightly co-integrate multiple specialized processor and memory chiplets. In such data-hungry multi-chip architectures, current Networksin- Package (NiPs) may not be enough to cater to their heterogeneous and fast-changing communication demands. This position paper makes the case for wireless in-package networking as the enabler of efficient and versatile wired-wireless interconnect fabrics for massive heterogeneous processors. To that end, the use of graphene-based antennas and transceivers with unique frequency-beam reconfigurability in the terahertz band is proposed. The feasibility of such a wireless vision and the main research challenges towards its realization are analyzed from the technological, communications, and computer architecture perspectives
Using coding and non-coding rare variants to target candidate genes in patients with severe tinnitus
Tinnitus is the phantom percept of an internal non-verbal set of noises and tones. It is reported by 15% of the population and it is usually associated with hearing and/or brain disorders. The role of structural variants (SVs) in coding and non-coding regions has not been investigated in patients with severe tinnitus. In this study, we performed whole-genome sequencing in 97 unrelated Swedish individuals with chronic tinnitus (TIGER cohort). Rare single nucleotide variants (SNV), large structural variants (LSV), and copy number variations (CNV) were retrieved to perform a gene enrichment analysis in TIGER and in a subgroup of patients with severe tinnitus (SEVTIN, n = 34), according to the tinnitus handicap inventory (THI) scores. An independent exome sequencing dataset of 147 Swedish tinnitus patients was used as a replication cohort (JAGUAR cohort) and population-specific datasets from Sweden (SweGen) and Non-Finish Europeans (NFE) from gnomAD were used as control groups. SEVTIN patients showed a higher prevalence of hyperacusis, hearing loss, and anxiety when they were compared to individuals in the TIGER cohort. We found an enrichment of rare missense variants in 6 and 8 high-constraint genes in SEVTIN and TIGER cohorts, respectively. Of note, an enrichment of missense variants was found in the CACNA1E gene in both SEVTIN and TIGER. We replicated the burden of missense variants in 9 high-constrained genes in the JAGUAR cohort, including the gene NAV2, when data were compared with NFE. Moreover, LSVs in constrained regions overlapping CACNA1E, NAV2, and TMEM132D genes were observed in TIGER and SEVTIN.publishedVersio
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