12,064 research outputs found
Composite Geometric Phase for Multipartite Entangled States
When an entangled state evolves under local unitaries, the entanglement in
the state remains fixed. Here we show the dynamical phase acquired by an
entangled state in such a scenario can always be understood as the sum of the
dynamical phases of its subsystems. In contrast, the equivalent statement for
the geometric phase is not generally true unless the state is separable. For an
entangled state an additional term is present, the mutual geometric phase, that
measures the change the additional correlations present in the entangled state
make to the geometry of the state space. For qubit states we find this
change can be explained solely by classical correlations for states with a
Schmidt decomposition and solely by quantum correlations for W states.Comment: 4 pages, 1 figure, improved presentation, results and conclusions
unchanged from v1. Accepted for publication in PR
Design and validation of a low cost indoor environment quality data logger
Theme: Fifty years later: Revisiting the role of architectural science in design and practiceThe appraisal of indoor environment quality in residential dwellings presents a range of technical challenges. Indoor environment quality (IEQ) is often described as having thermal, visual, aural and olfactory dimensions, each of which is assessed subjectively by the resident. While it is possible to objectively assess physical parameters relating to each aspect of IEQ, either directly or indirectly, resident satisfaction with the environment is determined subjectively so must be inferred. In the field study of thermal comfort (FSTC) approach, objective physical measurements are collected simultaneously with resident preference and sensation information, usually via a diary or written survey. This research paper explores a new approach to residential IEQ appraisal which extends the FSTC approach to the visual, aural and olfactory dimensions using a low cost data collection system based upon the Arduino microcontroller platform. The paper describes the design developed, presents early validation results and draws preliminary conclusions.Andrew Carre, Terence Williamson and Veronica Soebart
Phenomenology of B -> pi pi, pi K Decays at O(alpha^2 beta_0) in QCD Factorization
We study O(alpha^2 beta_0) perturbative corrections to matrix elements
entering two-body exclusive decays of the form B -> pi pi, pi K in the QCD
factorization formalism, including chirally enhanced power corrections, and
discuss the effect of these corrections on direct CP asymmetries, which receive
their first contribution at O(alpha). We find that the O(alpha^2 beta_0)
corrections are often as large as the O(alpha) corrections. We find large
uncertainties due to renormalization scale dependence as well as poor knowledge
of the non-perturbative parameters. We assess the effect of the perturbative
corrections on the direct CP violation parameters of B -> pi^+ pi^-.Comment: 27 pages, 5 figures. Updated input parameters and added citations;
expanded discussio
Optical spectroscopy of single quantum dots at tunable positive, neutral and negative charge states
We report on the observation of photoluminescence from positive, neutral and
negative charge states of single semiconductor quantum dots. For this purpose
we designed a structure enabling optical injection of a controlled unequal
number of negative electrons and positive holes into an isolated InGaAs quantum
dot embedded in a GaAs matrix. Thereby, we optically produced the charge states
-3, -2, -1, 0, +1 and +2. The injected carriers form confined collective
'artificial atoms and molecules' states in the quantum dot. We resolve
spectrally and temporally the photoluminescence from an optically excited
quantum dot and use it to identify collective states, which contain charge of
one type, coupled to few charges of the other type. These states can be viewed
as the artificial analog of charged atoms such as H, H, H,
and charged molecules such as H and H. Unlike higher
dimensionality systems, where negative or positive charging always results in
reduction of the emission energy due to electron-hole pair recombination, in
our dots, negative charging reduces the emission energy, relative to the
charge-neutral case, while positive charging increases it. Pseudopotential
model calculations reveal that the enhanced spatial localization of the
hole-wavefunction, relative to that of the electron in these dots, is the
reason for this effect.Comment: 5 figure
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Autonomous systems thermographic NDT of composite structures
Transient thermography is a method used successfully in the evaluation of composite materials and aerospace structures. It has the capacity to deliver both qualitative and quantitative results about hidden defects or features in a composite structure. Aircraft must undergo routine maintenance â inspection to check for any critical damage and thus to ensure its safety. This work aims to address the challenge of NDT automated inspection and improve the defectsâ detection by suggesting an autonomous thermographic imaging approach using a UAV (Unmanned Aerial Vehicle) active thermographic system. The concept of active thermography is discussed and presented in the inspection of aircraft CFRP panels along with the mission planning for aerial inspection using the UAV for real time inspection. Results indicate that the suggested approach could significantly reduce the inspection time, cost, and workload, whilst potentially increase the probability of detection of defects on aircraft composites
Improved methods for detecting gravitational waves associated with short gamma-ray bursts
In the era of second generation ground-based gravitational wave detectors,
short gamma-ray bursts (GRBs) will be among the most promising astrophysical
events for joint electromagnetic and gravitational wave observation. A targeted
search for gravitational wave compact binary merger signals in coincidence with
short GRBs was developed and used to analyze data from the first generation
LIGO and Virgo instruments. In this paper, we present improvements to this
search that enhance our ability to detect gravitational wave counterparts to
short GRBs. Specifically, we introduce an improved method for estimating the
gravitational wave background to obtain the event significance required to make
detections; implement a method of tiling extended sky regions, as required when
searching for signals associated to poorly localized GRBs from Fermi Gamma-ray
Burst Monitor or the InterPlanetary Network; and incorporate astrophysical
knowledge about the beaming of GRB emission to restrict the search parameter
space. We describe the implementation of these enhancements and demonstrate how
they improve the ability to observe binary merger gravitational wave signals
associated with short GRBs.Comment: 13 pages, 6 figure
Induction of HIV-1 Gag-specific memory T cells in Chacma baboons by MVA prime and VLP boost vaccine regimen
We previously reported induction of HIV-specific responses in Chacma baboons following immunization with SAAVI MVA-C (MVA) and HIV-1 Pr55 Gag virus-like particles (VLPs) in a prime-boost vaccination strategy. In the current study, we characterised the vaccine specific memory T cells by flow cytometry
Detection of X-ray galaxy clusters based on the Kolmogorov method
The detection of clusters of galaxies in large surveys plays an important
part in extragalactic astronomy, and particularly in cosmology, since cluster
counts can give strong constraints on cosmological parameters. X-ray imaging is
in particular a reliable means to discover new clusters, and large X-ray
surveys are now available. Considering XMM-Newton data for a sample of 40 Abell
clusters, we show that their analysis with a Kolmogorov distribution can
provide a distinctive signature for galaxy clusters. The Kolmogorov method is
sensitive to the correlations in the cluster X-ray properties and can therefore
be used for their identification, thus allowing to search reliably for clusters
in a simple way
Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure
The temperature and pressure dependence of the partial density of phonon
states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear
inelastic scattering (NIS). The high energy resolution allows for a detailed
observation of spectral properties. A sharpening of the optical phonon modes
and shift of all spectral features towards higher energies by ~4% with
decreasing temperature from 296 K to 10 K was found. However, no detectable
change at the tetragonal - orthorhombic phase transition around 100 K was
observed. Application of a pressure of 6.7 GPa, connected with an increase of
the superconducting temperature from 8 K to 34 K, results in an increase of the
optical phonon mode energies at 296 K by ~12%, and an even more pronounced
increase for the lowest-lying transversal acoustic mode. Despite these strong
pressure-induced modifications of the phonon-DOS we conclude that the
pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the
framework of classical electron-phonon coupling. This result suggests the
importance of spin fluctuations to the observed superconductivity
Extracting molecular Hamiltonian structure from time-dependent fluorescence intensity data
We propose a formalism for extracting molecular Hamiltonian structure from
inversion of time-dependent fluorescence intensity data. The proposed method
requires a minimum of \emph{a priori} knowledge about the system and allows for
extracting a complete set of information about the Hamiltonian for a pair of
molecular electronic surfaces.Comment: 7pages, no figures, LaTeX2
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