11,853 research outputs found
Observation of Fast Evolution in Parity-Time-Symmetric System
To find and realize the optimal evolution between two states is significant
both in theory and application. In quantum mechanics, the minimal evolution is
bounded by the gap between the largest and smallest eigenvalue of the
Hamiltonian. In the parity-time-symmetric(PT-symmetric) Hamiltonian theory, it
was predicted that the optimized evolution time can be reduced drastically
comparing to the bound in the Hermitian case, and can become even zero. In this
Letter, we report the experimental observation of the fast evolution of a
PT-symmetric Hamiltonian in an nuclear magnetic resonance (NMR) quantum system.
The experimental results demonstrate that the PT-symmetric Hamiltonian can
indeed evolve much faster than that in a quantum system, and time it takes can
be arbitrary close to zero.Comment: 13 pages, 5 figure
Low-rank SIFT: An Affine Invariant Feature for Place Recognition
In this paper, we present a novel affine-invariant feature based on SIFT,
leveraging the regular appearance of man-made objects. The feature achieves
full affine invariance without needing to simulate over affine parameter space.
Low-rank SIFT, as we name the feature, is based on our observation that local
tilt, which are caused by changes of camera axis orientation, could be
normalized by converting local patches to standard low-rank forms. Rotation,
translation and scaling invariance could be achieved in ways similar to SIFT.
As an extension of SIFT, our method seeks to add prior to solve the ill-posed
affine parameter estimation problem and normalizes them directly, and is
applicable to objects with regular structures. Furthermore, owing to recent
breakthrough in convex optimization, such parameter could be computed
efficiently. We will demonstrate its effectiveness in place recognition as our
major application. As extra contributions, we also describe our pipeline of
constructing geotagged building database from the ground up, as well as an
efficient scheme for automatic feature selection
Relativistic Theory of Infinite Statistics Fields
Infinite statistics in which all representations of the symmetric group can
occur is known as a special case of quon theory. However, the validity of
relativistic quon theories is still in doubt. In this paper we prove that there
exists a relativistic quantum field theory which allows interactions involving
infinite statistics particles. We also give some consistency analysis of this
theory such as conservation of statistics and Feynman rules.Comment: 7 pages, 3 figure
Point estimate method for voltage unbalance evaluation in residential distribution networks with high penetration of small wind turbines
Voltage unbalance (VU) in residential distribution networks (RDNs) is mainly caused by load unbalance in three phases, resulting from network configuration and load-variations. The increasing penetration of distributed generation devices, such as small wind turbines (SWTs), and their uneven distribution over the three phases have introduced difficulties in evaluating possible VU. This paper aims to provide a three-phase probabilistic power flow method, point estimate method to evaluate the VU. This method, considering the randomness of load switching in customers’ homes and time-variation in wind speed, is shown to be capable of providing a global picture of a network’s VU degree so that it can be used for fast evaluation. Applying the 2m + 1 scheme of the proposed method to a generic UK distribution network shows that a balanced SWT penetration over three phases reduces the VU of a RDN. Greater unbalance in SWT penetration results in higher voltage unbalance factor (VUF), and cause VUF in excess of the UK statutory limit of 1.3%
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