413 research outputs found
Efficient Optimal Minimum Error Discrimination of Symmetric Quantum States
This paper deals with the quantum optimal discrimination among mixed quantum
states enjoying geometrical uniform symmetry with respect to a reference
density operator . It is well-known that the minimal error probability
is given by the positive operator-valued measure (POVM) obtained as a solution
of a convex optimization problem, namely a set of operators satisfying
geometrical symmetry, with respect to a reference operator , and
maximizing . In this paper, by resolving the dual
problem, we show that the same result is obtained by minimizing the trace of a
semidefinite positive operator commuting with the symmetry operator and
such that . The new formulation gives a deeper insight into the
optimization problem and allows to obtain closed-form analytical solutions, as
shown by a simple but not trivial explanatory example. Besides the theoretical
interest, the result leads to semidefinite programming solutions of reduced
complexity, allowing to extend the numerical performance evaluation to quantum
communication systems modeled in Hilbert spaces of large dimension.Comment: 5 pages, 1 Table, no figure
Axion minicluster streams in the solar neighbourhood
A consequence of QCD axion dark matter being born after inflation is the
emergence of ultra-small-scale substructures known as miniclusters. Although
miniclusters merge to form minihalos, this intrinsic granularity is expected to
remain imprinted on small scales in our galaxy, leading to potentially damning
consequences for the campaign to detect axions directly on Earth. This picture,
however, is modified when one takes into account the fact that encounters with
stars will tidally strip mass from the miniclusters, creating pc-long tidal
streams that act to refill the dark matter distribution. Here we ask whether or
not this stripping rescues experimental prospects from the worst-case scenario
in which the majority of axions remain bound up in unobservably small
miniclusters. We find that the density sampled by the Earth on mpc-scales will
be, on average, around 70-90% of the known local DM density, and at a typical
point in the solar neighbourhood, we expect most of the dark matter to be
comprised of debris from - overlapping streams. If
haloscopes can measure the axion signal with high-enough frequency resolution,
then these streams are revealed in the form of an intrinsically spiky
lineshape, in stark contrast with the standard assumption of a smooth,
featureless Maxwellian distribution -- a unique prediction that constitutes a
way for experiments to distinguish between pre and post-inflationary axion
cosmologies.Comment: 5 + 8 page
Mixed population of competing TASEPs with a shared reservoir of particles
We introduce a mean-field theoretical framework to describe multiple totally
asymmetric simple exclusion processes (TASEPs) with different lattice lengths,
entry and exit rates, competing for a finite reservoir of particles. We present
relations for the partitioning of particles between the reservoir and the
lattices: these relations allow us to show that competition for particles can
have non-trivial effects on the phase behavior of individual lattices. For a
system with non-identical lattices, we find that when a subset of lattices
undergoes a phase transition from low to high density, the entire set of
lattice currents becomes independent of total particle number. We generalize
our approach to systems with a continuous distribution of lattice parameters,
for which we demonstrate that measurements of the current carried by a single
lattice type can be used to extract the entire distribution of lattice
parameters. Our approach applies to populations of TASEPs with any distribution
of lattice parameters, and could easily be extended beyond the mean-field case.Comment: 12 pages, 8 figure
Concettualizzazione e contestualizzazione dei beni culturali archeologici
This report describes the observations made while developing a new methodology for historic surveys used for the re-contextualisation of archaeological finds. This particular methodology avails itself of both traditional historic surveys as well as the representation of knowledge through ontology. The methodology described here was developed in reference to specific cases of re-contextualisation of archaeological artefacts from Pompeii which are now in the National Archaeological Museum in Naples
Bottleneck-induced transitions in a minimal model for intracellular transport
We consider the influence of disorder on the non-equilibrium steady state of
a minimal model for intracellular transport. In this model particles move
unidirectionally according to the \emph{totally asymmetric exclusion process}
(TASEP) and are coupled to a bulk reservoir by \emph{Langmuir kinetics}. Our
discussion focuses on localized point defects acting as a bottleneck for the
particle transport. Combining analytic methods and numerical simulations, we
identify a rich phase behavior as a function of the defect strength. Our
analytical approach relies on an effective mean-field theory obtained by
splitting the lattice into two subsystems, which are effectively connected
exploiting the local current conservation. Introducing the key concept of a
carrying capacity, the maximal current which can flow through the bulk of the
system (including the defect), we discriminate between the cases where the
defect is irrelevant and those where it acts as a bottleneck and induces
various novel phases (called {\it bottleneck phases}). Contrary to the simple
TASEP in the presence of inhomogeneities, many scenarios emerge and translate
into rich underlying phase-diagrams, the topological properties of which are
discussed.Comment: 14 pages, 15 figures, 1 tabl
Simulations of axionlike particles in the postinflationary scenario
Axions and axionlike particles (ALPs) are some of the most popular candidates for dark matter, with several viable production scenarios that make different predictions. In the scenario in which the axion is born after inflation, its field develops significant inhomogeneity and evolves in a highly nonlinear fashion. Understanding the eventual abundance and distribution of axionic dark matter in this scenario therefore requires dedicated numerical simulations. So far the community has focused its efforts on simulations of the QCD axion, a model that predicts a specific temperature dependence for the axion mass. Here, we go beyond the QCD axion, and perform a suite of simulations on lattice sizes of 30723, over a range of possible temperature dependencies labeled by a power-law index n0, 6]. We study the complex dynamics of the axion field, including the scaling of cosmic strings and domain walls, the spectrum of nonrelativistic axions, the lifetime and internal structure of axitons, and the seeds of miniclusters. In particular, we quantify how much the string-wall network contributes to the dark matter abundance as a function of how quickly the axion mass grows. We find that a temperature-independent model produces 25% more dark matter than the standard misalignment calculation. In contrast to this generic ALP, QCD axion models are almost six times less efficient at producing dark matter. Given the flourishing experimental campaign to search for ALPs, these results have potentially wide implications for direct and indirect searches. © 2022 authors. Published by the American Physical Society
Axion minivoids and implications for direct detection
In the scenario in which QCD axion dark matter is produced after inflation, the Universe is populated by large inhomogeneities on very small scales. Eventually, these fluctuations will collapse gravitationally to form dense axion miniclusters that trap up to âŒ75% of the dark matter within asteroid-mass clumps. Axion miniclusters are physically tiny however, so haloscope experiments searching for axions directly on Earth are much more likely to be probing âminivoidsââthe space in between miniclusters. This scenario seems like it ought to spell doom for haloscopes, but while these minivoids might be underdense, they are not totally devoid of axions. Using Schrödinger-Poisson and N-body simulations to evolve from realistic initial field configurations, we quantify the extent to which the local ambient dark matter density is suppressed in the postinflationary scenario. We find that a typical experimental measurement will sample an axion density that is only around 10% of the expected galactic dark matter density. Our results are taken as conservative estimates and have implications for experimental campaigns lasting longer than a few years, as well as broadband haloscopes that have sensitivity to transient signatures. We show that for a OĂ°(year)-long integration times, the measured dark matter density should be expected to vary by 20%â30%
May car washing represent a risk for Legionella infection?
Background. Legionella is a ubiquitous Gram-negative bacterium naturally found in aquatic environments. It can pose a health problem when it grows and spreads in man-made water systems. Legionella pneumophila is the most common cause of Legionnaires\u2019 disease nowadays, a community-acquired pneumonia with pulmonary symptoms and chest radiography no different from any other form of infectious pneumonia. Legionella monitoring is important for public health reasons, including the identification of unusual environmental sources of Legionella.
Methods. We report two cases of Legionnaires\u2019 disease associated with two different car wash installations in the province of Vicenza, in the Veneto region, northeastern Italy. Patients were not employees of the car wash installations, but users of the service. In both cases, Legionella antigen was detected in urine using the Alere BinaxNOW\uae Legionella Urinary Antigen, and Legionella antibodies were detected in serum using SERION ELISA classic Legionella pneumophila 1-7 IgG and IgM. Water samples were also analyzed as part of the surveillance program for Legionella prevention and control in compliance with the Italian guidelines.
Results. Both patients had clinical symptoms and chest radiography compatible with pneumonia, and only one of them had diabetes as a risk factor. Legionella urinary antigen and serological test on serum samples were positive for Legionella in both patients, even if much slighter in the case A due to the retrospective serological investigation performed a year later the episode and after the second clinical case occurred in the same district. The environmental investigations highlighted two different car wash plants as potential source of infection. A certified company using shock hyperchlorination was asked to disinfect the two plants and, subsequently, control samples resulted negative for Legionella pneumophila.
Conclusions. Any water source producing aerosols should be considered at risk for the transmission of Legionella bacteria, including car wash installations frequently used by a large number of customers and where poor maintenance probably creates favorable conditions for Legionella overgrowth and spreading. Additional research is needed to ascertain optimal strategies for Legionella monitoring and control, but environmental surveillance, paying careful attention to possible unconventional sources, should remain an important component of any Legionnaires\u2019 disease prevention program. Additionally, all available diagnostic methods would be recommended for the confirmation of all cases even in the event of non-serogroup 1 Legionella pneumophila infection, probably underestimated at this time
Measurement of micro moulded parts by Computed Tomography and comparison to optical and tactile techniques
This paper focuses on dimensional verification of two micro-injection moulded components, selected from actual industrial productions, using CT metrological tools. In addition to CT scanning, also a tactile Coordinate Measuring Machine (CMM) with sub-micrometre uncertainty and an Optical Coordinate Measuring Machine (OCMM) allowing fast measurements suitable for in-line quality control were employed as validation instruments. The experimental work carried out and the analysis of the results provide valuable conclusions about the advantages and drawbacks of using CT metrology in comparison with CMM and OCMM when these techniques are employed for quality control of micro moulded parts
End-to-end Molecular Communication Channels in Cell Metabolism: an Information Theoretic Study
The opportunity to control and fine-tune the behavior of biological cells is a fascinating possibility for many diverse disciplines, ranging from medicine and ecology, to chemical industry and space exploration. While synthetic biology is providing novel tools to reprogram cell behavior from their genetic code, many challenges need to be solved before it can become a true engineering discipline, such as reliability, safety assurance, reproducibility and stability. This paper aims to understand the limits in the controllability of the behavior of a natural (non-engineered) biological cell. In particular, the focus is on cell metabolism, and its natural regulation mechanisms, and their ability to react and change according to the chemical characteristics of the external environment. To understand the aforementioned limits of this ability, molecular communication is used to abstract biological cells into a series of channels that propagate information on the chemical composition of the extracellular environment to the cellâs behavior in terms of uptake and consumption of chemical compounds, and growth rate. This provides an information-theoretic framework to analyze the upper bound limit to the capacity of these channels to propagate information, which is based on a well-known and computationally efficient metabolic simulation technique. A numerical study is performed on two human gut microbes, where the upper bound is estimated for different environmental compounds, showing there is a potential for future practical applications
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