9,856 research outputs found
A thirty-six element array antenna system
Thirty-six element square array, with mutual coupling between crossed slots for array elements, is used as an electronically scanned tracking antenna. The system does not require the movement of the antenna or the presence of an operator
Evaluation of data obtained from a 35 GHz propagation experiment Technical report no. 7
Effect of atmospheric humidity, pressure, and temperature on electromagnetic wave propagatio
Improved VHF direction finding system
Direction finding device operating at very high frequencies requires a loop antenna, mechanical rotation, and large structures. The system is applicable to an unmanned configuration. Direction information is extracted in the form of a direction cosine analog
Analysis and optimization of an omnidirectional direction-finding system
System determines the direction of arrival of an electromagnetic wave with the direction information in a readily usable form. It presents a relatively small physical structure and does not require mechanical positioning
Surveying the SO(10) Model Landscape: The Left-Right Symmetric Case
Grand Unified Theories (GUTs) are a very well motivated extensions of the
Standard Model (SM), but the landscape of models and possibilities is
overwhelming, and different patterns can lead to rather distinct
phenomenologies. In this work we present a way to automatise the model building
process, by considering a top to bottom approach that constructs viable and
sensible theories from a small and controllable set of inputs at the high
scale. By providing a GUT scale symmetry group and the field content, possible
symmetry breaking paths are generated and checked for consistency, ensuring
anomaly cancellation, SM embedding and gauge coupling unification. We emphasise
the usefulness of this approach for the particular case of a non-supersymmetric
SO(10) model with an intermediate left-right symmetry and we analyse how
low-energy observables such as proton decay and lepton flavour violation might
affect the generated model landscape.Comment: 36 pages, 6 figure
A study of antenna and radio frequency tracking system Final summary report, 1 Feb. 1963 - 30 Nov. 1965
Phase stability of very low frequency radio signal propagation, electronically scanned tracking antenna array, and inverted rf tracking syste
Transport and Dissipation in Quantum Pumps
This paper is about adiabatic transport in quantum pumps. The notion of
``energy shift'', a self-adjoint operator dual to the Wigner time delay, plays
a role in our approach: It determines the current, the dissipation, the noise
and the entropy currents in quantum pumps. We discuss the geometric and
topological content of adiabatic transport and show that the mechanism of
Thouless and Niu for quantized transport via Chern numbers cannot be realized
in quantum pumps where Chern numbers necessarily vanish.Comment: 31 pages, 10 figure
The Hawking-Penrose singularity theorem for -Lorentzian metrics
We show that the Hawking--Penrose singularity theorem, and the generalisation
of this theorem due to Galloway and Senovilla, continue to hold for Lorentzian
metrics that are of -regularity. We formulate appropriate weak
versions of the strong energy condition and genericity condition for
-metrics, and of -trapped submanifolds. By regularisation, we
show that, under these weak conditions, causal geodesics necessarily become
non-maximising. This requires a detailed analysis of the matrix Riccati
equation for the approximating metrics, which may be of independent interest.Comment: Minor amendments in v4: Removed non-equivalent condition from Def.
2.2 and adapted Lemma 3.5 and the proof of Lemma 3.
Parametric resonance and spin-charge separation in 1D fermionic systems
We show that the periodic modulation of the Hamiltonian parameters for 1D
correlated fermionic systems can be used to parametrically amplify their
bosonic collective modes. Treating the problem within the Luttinger liquid
picture, we show how charge and spin density waves with different momenta are
simultaneously amplified. We discuss the implementation of our predictions for
cold atoms in 1D modulated optical lattices, showing that the fermionic
momentum distribution directly provides a clear signature of spin-charge
separation.Comment: 6 pages, 3 figures, published versio
- …