scholarly journals Exploiting spatiotemporal degrees of freedom for far-field subwavelength focusing using time reversal in fractals

2016 ◽  
Vol 93 (18) ◽  
Author(s):  
Matthieu Dupré ◽  
Fabrice Lemoult ◽  
Mathias Fink ◽  
Geoffroy Lerosey
Keyword(s):  
Time Reversal ◽  
Degrees Of Freedom ◽  
Far Field

scholarly journals Multiorbital singlet pairing and d + d superconductivity

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Emilian M. Nica ◽  
Qimiao Si
Keyword(s):  
Time Reversal ◽  
Heavy Fermion ◽  
Degrees Of Freedom ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Matrix Structure ◽  
Spin Singlet ◽  
Low Energies ◽  
Triplet Pairing ◽  
Orbital Space

AbstractRecent experiments in multiband Fe-based and heavy-fermion superconductors have challenged the long-held dichotomy between simple s- and d-wave spin-singlet pairing states. Here, we advance several time-reversal-invariant irreducible pairings that go beyond the standard singlet functions through a matrix structure in the band/orbital space, and elucidate their naturalness in multiband systems. We consider the sτ3 multiorbital superconducting state for Fe-chalcogenide superconductors. This state, corresponding to a d + d intra- and inter-band pairing, is shown to contrast with the more familiar d + id state in a way analogous to how the B- triplet pairing phase of 3He superfluid differs from its A- phase counterpart. In addition, we construct an analog of the sτ3 pairing for the heavy-fermion superconductor CeCu2Si2, using degrees-of-freedom that incorporate spin-orbit coupling. Our results lead to the proposition that d-wave superconductors in correlated multiband systems will generically have a fully-gapped Fermi surface when they are examined at sufficiently low energies.

scholarly journals From Loschmidt daemons to time-reversed waves

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150156 ◽  
Author(s):  
Mathias Fink
Keyword(s):  
Wave Propagation ◽  
Time Reversal ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
Propagation Time ◽  
Reversal Invariance ◽  
Spatial Boundary ◽  
Dual Approaches ◽  
Spatio Temporal

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses ‘time-reversal mirrors’ with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that ‘instantaneous time mirrors’, mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.

Subwavelength Focussing in Metamaterials Using Far Field Time Reversal

2013 ◽  
pp. 141-168 ◽  
Author(s):  
Mathias Fink ◽  
Fabrice Lemoult ◽  
Julien de Rosny ◽  
Arnaud Tourin ◽  
Geoffroy Lerosey
Keyword(s):  
Time Reversal ◽  
Far Field

scholarly journals Increasing Utilization of Redundant Virtual Array for DOA Estimation Based on Coprime Array

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Chenghong Zhan ◽  
Guoping Hu ◽  
Zixin Zhang ◽  
Ziang Feng
Keyword(s):  
Parameter Estimation ◽  
High Precision ◽  
Degrees Of Freedom ◽  
Doa Estimation ◽  
Far Field ◽  
Virtual Array ◽  
Previous Algorithm ◽  
Array Structure ◽  
Simulation Results ◽  
Coprime Array

In this paper, we initiated a method to estimate the direction of arrival (DOA) of far-field, narrowband, and incoherent targets using coprime array. First, we proposed a coprime array structure and analysed the distribution of difference coarray (DCA). The degrees of freedom (DOF) of the proposed coprime array became clearer by referring to the DCA conception. However, previous algorithm only uses the continuous virtual array, which causes the virtual array elements in the repeated position being abandoned. Therefore, the paper analyses the distribution of virtual array based on DCA conception and averages the receiving signal on these redundant virtual array elements to increase the utilization of receiving data. As a result, the algorithm has high precision in parameter estimation. Simulation results have shown the superiority of the proposed algorithm.

scholarly journals Emergent Chiral Symmetry: Parity and Time Reversal Doubles

1997 ◽  
Vol 12 (29) ◽  
pp. 5325-5357 ◽  
Author(s):  
A. P. Balachandran ◽  
S. Vaidya
Keyword(s):  
Time Reversal ◽  
Particle Physics ◽  
Nuclear Physics ◽  
Degrees Of Freedom ◽  
High Energy ◽  
Approximate Symmetry ◽  
Opposite Parity ◽  
Doublet Structure ◽  
Low Energies ◽  
Oppenheimer Approximation

There are numerous examples of approximately degenerate states of opposite parity in molecular physics. Theory indicates that these doubles can occur in molecules that are reflection-asymmetric. Such parity doubles occur in nuclear physics as well, among nuclei with odd A ~ 219–229. We have also suggested elsewhere that such doubles occur in particle physics for baryons made up of cbu and cbd quarks. In this article, we discuss the theoretical foundations of these doubles in detail, demonstrating their emergence as a surprisingly subtle consequence of the Born–Oppenheimer approximation, and emphasizing their bundle-theoretic and topological underpinnings. Starting with certain "low energy" effective theories in which classical symmetries like parity and time reversal are anomalously broken on quantization, we show how these symmetries can be restored by judicious inclusion of "high-energy" degrees of freedom. This mechanism of restoring the symmetry naturally leads to the aforementioned doublet structure. A novel byproduct of this mechanism is the emergence of an approximate symmetry (corresponding to the approximate degeneracy of the doubles) at low energies which is not evident in the full Hamiltonian. We also discuss the implications of this mechanism for Skyrmion physics, monopoles, anomalies and quantum gravity.

scholarly journals Far Field Modeling of Electromagnetic Time Reversal and Application to Selective Focusing on Small Scatterers

2008 ◽  
Vol 69 (3) ◽  
pp. 830-844 ◽  
Author(s):  
X. Antoine ◽  
B. Pinçon ◽  
K. Ramdani ◽  
B. Thierry
Keyword(s):  
Time Reversal ◽  
Far Field ◽  
Field Modeling ◽  
Small Scatterers

scholarly journals A performance predictor of beamforming versus time-reversal based far-field wireless power transfer from linear array

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hong Soo Park ◽  
Sun K. Hong
Keyword(s):  
Time Reversal ◽  
Power Transmission ◽  
Linear Array ◽  
Wireless Power Transfer ◽  
Far Field ◽  
Power Transfer ◽  
Wireless Power ◽  
Dynamic Propagation ◽  
Received Power ◽  
Indoor Scenarios

AbstractFor far-field wireless power transfer (WPT) in a complex propagation environment, a time-reversal (TR) based WPT that can overcome the drawbacks of conventional beamforming (BF) by taking advantage of multipath has been recently proposed. However, due to the WPT performance of BF and TR depending on the complexity of the propagation environment, the performance prediction between BF versus TR would be required. We present a detailed and generalized analysis of the recently proposed performance metric referred to as the peak received power ratio (PRPR) for linear array-based WPT. Here, the effectiveness of PRPR is verified via measurement for free space and indoor scenarios. The results demonstrate that PRPR is directly related to the complexity of the propagation environment and the corresponding power transmission capability of BF and TR. That is, the higher the complexity, the greater the value of PRPR and TR outperforms BF with higher peak power given the same average transmit power and vice versa. The mode decision between BF and TR based on PRPR potentially promises efficient far-field WPT even in a dynamic propagation environment.

scholarly journals Far field model for time reversal and application to selective focusing on small dielectric inhomogeneities

2013 ◽  
Vol 7 (2) ◽  
pp. 445-470 ◽  
Author(s):  
Corinna Burkard ◽  
◽  
Aurelia Minut ◽  
Karim Ramdani ◽  
◽  
...  
Keyword(s):  
Time Reversal ◽  
Field Model ◽  
Far Field
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