8,345 research outputs found

### Conformal Field Theories, Representations and Lattice Constructions

An account is given of the structure and representations of chiral bosonic
meromorphic conformal field theories (CFT's), and, in particular, the
conditions under which such a CFT may be extended by a representation to form a
new theory. This general approach is illustrated by considering the untwisted
and $Z_2$-twisted theories, $H(\Lambda)$ and $\tilde H(\Lambda)$ respectively,
which may be constructed from a suitable even Euclidean lattice $\Lambda$.
Similarly, one may construct lattices $\Lambda_C$ and $\tilde\Lambda_C$ by
analogous constructions from a doubly-even binary code $C$. In the case when
$C$ is self-dual, the corresponding lattices are also. Similarly, $H(\Lambda)$
and $\tilde H(\Lambda)$ are self-dual if and only if $\Lambda$ is. We show that
$H(\Lambda_C)$ has a natural ``triality'' structure, which induces an
isomorphism $H(\tilde\Lambda_C)\equiv\tilde H(\Lambda_C)$ and also a triality
structure on $\tilde H(\tilde\Lambda_C)$. For $C$ the Golay code,
$\tilde\Lambda_C$ is the Leech lattice, and the triality on $\tilde
H(\tilde\Lambda_C)$ is the symmetry which extends the natural action of (an
extension of) Conway's group on this theory to the Monster, so setting triality
and Frenkel, Lepowsky and Meurman's construction of the natural Monster module
in a more general context. The results also serve to shed some light on the
classification of self-dual CFT's. We find that of the 48 theories $H(\Lambda)$
and $\tilde H(\Lambda)$ with central charge 24 that there are 39 distinct ones,
and further that all 9 coincidences are accounted for by the isomorphism
detailed above, induced by the existence of a doubly-even self-dual binary
code.Comment: 65 page

### Shapes and Dynamics from the Time-Dependent Mean Field

Explaining observed properties in terms of underlying shape degrees of
freedom is a well--established prism with which to understand atomic nuclei.
Self--consistent mean--field models provide one tool to understand nuclear
shapes, and their link to other nuclear properties and observables. We present
examples of how the time--dependent extension of the mean--field approach can
be used in particular to shed light on nuclear shape properties, particularly
looking at the giant resonances built on deformed nuclear ground states, and at
dynamics in highly-deformed fission isomers. Example calculations are shown of
$^{28}$Si in the first case, and $^{240}$Pu in the latter case.Comment: 9 pages, 5 figures, to appear in proceedings of International
Workshop "Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects"
(SDANCA-15), 8-10 October 2015, Sofia, Bulgari

### Cause of the charge radius isotope shift at the \emph{N}=126 shell gap

We discuss the mechanism causing the `kink' in the charge radius isotope
shift at the N=126 shell closure. The occupation of the 1$i_{11/2}$ neutron
orbital is the decisive factor for reproducing the experimentally observed
kink. We investigate whether this orbital is occupied or not by different
Skyrme effective interactions as neutrons are added above the shell closure.
Our results demonstrate that several factors can cause an appreciable
occupation of the 1$i_{11/2}$ neutron orbital, including the magnitude of the
spin-orbit field, and the isoscalar effective mass of the Skyrme interaction.
The symmetry energy of the effective interaction has little influence upon its
ability to reproduce the kink.Comment: 4 pages, 4 figures, to be submitted to proceedings of INPC 201

### Electromagnetic field application to underground power cable detection

Before commencing excavation or other work where power or other cables may be buried, it is important to determine the location of cables to ensure that they are not damaged. This paper describes a method of power-cable detection and location that uses measurements of the magnetic field produced by the currents in the cable, and presents the results of tests performed to evaluate the method. The cable detection and location program works by comparing the measured magnetic field signal with values predicted using a simple numerical model of the cable. Search coils are used as magnetic field sensors, and a measurement system is setup to measure the magnetic field of an underground power cable at a number of points above the ground so that it can detect the presence of an underground power cable and estimate its position. Experimental investigations were carried out using a model and under real site test conditions. The results show that the measurement system and cable location method give a reasonable prediction for the position of the target cable

### Detection and Location of Underground Power Cable using Magnetic Field Technologies

The location of buried underground electricity cables is becoming a major engineering and social issue worldwide. Records of utility locations are relatively scant, and even when records are available, they almost always refer to positions relative to ground-level physical features that may no longer exist or that may have been moved or altered. The lack of accurate positioning records of existing services can cause engineering and construction delays and safety hazards when new construction, repairs, or upgrades are necessary. Hitting unknown underground obstructions has the potential to cause property damage, injuries and, even deaths. Thus, before commencing excavation or other work where power or other cables may be buried, it is important to determine the location of the cables to ensure that they are not damaged during the work. This paper describes the use of an array of passive magnetic sensors (induction coils) together with signal processing techniques to detect and locate underground power cables. The array consists of seven identical coils mounted on a support frame; one of these coils was previously tested under laboratory conditions, and relevant results have been published in [1]. A measurement system was constructed that uses a battery powered data acquisition system with two NI 9239 modules connected to the coil array, and controlled by a laptop. The system is designed to measure the magnetic field of an underground power cable at a number of points above the ground. A 3 by 3 m test area was chosen in one of our campus car parks. This area was chosen because the universityâ€™s utility map shows an isolated power cable there. Measurements were taken with the array in 16 different test positions, and compared with the values predicted for a long straight horizontal cable at various positions. Finally, error maps were plotted for different Z-coordinate values, showing the minimum fitting error for each position in this plane. One such map is shown in Figure 1; the low error values of 4-5% give a high degree of confidence that most of the measured signal is due to a cable near to these positions. This view is supported by the fact that the universityâ€™s utility map shows the cable at X = 1.4 m, and by amplitude measurements taken with a hand-held magnetic field meter

### Non Abelian Sugawara Construction and the q-deformed N=2 Superconformal Algebra

The construction of a q-deformed N=2 superconformal algebra is proposed in
terms of level 1 currents of ${\cal{U}}_{q} ({\widehat{su}}(2))$ quantum affine
Lie algebra and a single real Fermi field. In particular, it suggests the
expression for the q-deformed Energy-Momentum tensor in the Sugawara form. Its
constituents generate two isomorphic quadratic algebraic structures. The
generalization to ${\cal{U}}_{q} ({\widehat{su}}(N+1))$ is also proposed.Comment: AMSLATEX, 21page

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