scholarly journals Connecting active and passive PT -symmetric Floquet modulation models

2020 ◽  
Author(s):  
Andrew K Harter ◽  
Yogesh N Joglekar
Keyword(s):  
Open Systems ◽  
Symmetric Case ◽  
Pt Symmetry ◽  
Time Dependent ◽  
Symmetric System ◽  
Complex Conjugate ◽  
Static Case ◽  
The Past ◽  
Gain Loss ◽  
Symmetric Phase

Abstract Open systems with gain, loss, or both, described by non-Hermitian Hamiltonians, have been a research frontier for the past decade. In particular, such Hamiltonians which possess parity-time (PT) symmetry feature dynamically stable regimes of unbroken symmetry with completely real eigenspectra that are rendered into complex conjugate pairs as the strength of the non-Hermiticity increases. By subjecting a PT-symmetric system to a periodic (Floquet) driving, the regime of dynamical stability can be dramatically affected, leading to a frequency-dependent threshold for the PT-symmetry breaking transition. We present a simple model of a time-dependent PT-symmetric Hamiltonian which smoothly connects the static case, a PT-symmetric Floquet case, and a neutral-PT-symmetric case. We analytically and numerically analyze the PT phase diagrams in each case, and show that slivers of PT-broken (PT-symmetric) phase extend deep into the nominally low (high) non-Hermiticity region.

scholarly journals Scattering Properties of PT-Symmetric Chiral Metamaterials

Photonics ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 43
Author(s):  
Ioannis Katsantonis ◽  
Sotiris Droulias ◽  
Costas M. Soukoulis ◽  
Eleftherios N. Economou ◽  
Maria Kafesaki
Keyword(s):  
Pt Symmetry ◽  
Optical Systems ◽  
Symmetric System ◽  
Angle Of Incidence ◽  
Asymmetric Transmission ◽  
Chiral Metamaterials ◽  
Polarization Control ◽  
Gain Loss ◽  
Incident Waves ◽  
At Will

The combination of gain and loss in optical systems that respect parity–time (PT)-symmetry has pointed recently to a variety of novel optical phenomena and possibilities. Many of them can be realized by combining the PT-symmetry concepts with metamaterials. Here we investigate the case of chiral metamaterials, showing that combination of chiral metamaterials with PT-symmetric gain–loss enables a very rich variety of phenomena and functionalities. Examining a simple one-dimensional chiral PT-symmetric system, we show that, with normally incident waves, the PT-symmetric and the chirality-related characteristics can be tuned independently and superimposed almost at will. On the other hand, under oblique incidence, chirality affects all the PT-related characteristics, leading also to novel and uncommon wave propagation features, such as asymmetric transmission and asymmetric optical activity and ellipticity. All these features are highly controllable both by chirality and by the angle of incidence, making PT-symmetric chiral metamaterials valuable in a large range of polarization-control-targeting applications.

scholarly journals Realization of complex conjugate media using non-PT-symmetric photonic crystals

Nanophotonics ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 195-203
Author(s):  
Xiaohan Cui ◽  
Kun Ding ◽  
Jian-Wen Dong ◽  
C.T. Chan
Keyword(s):  
Refractive Index ◽  
Photonic Crystals ◽  
Pt Symmetry ◽  
Symmetric System ◽  
Necessary Condition ◽  
Complex Conjugate ◽  
Real Spectrum ◽  
The Real ◽  
Permittivity And Permeability ◽  
Symmetric Loss

AbstractAlthough parity-time (PT)-symmetric systems can exhibit real spectra in the exact PT-symmetry regime, PT-symmetry is actually not a necessary condition for the real spectra. Here, we show that non-PT-symmetric photonic crystals (PCs) carrying Dirac-like cone dispersions can always exhibit real spectra as long as the average non-Hermiticity strength within the unit cell for the eigenstates is zero. By building a non-Hermitian Hamiltonian model, we find that the real spectra of the non-PT-symmetric system can be explained using the concept of pseudo-Hermiticity. We demonstrate using effective medium theories that, in the long-wavelength limit, such non-PT-symmetric PCs behave like the so-called complex conjugate medium (CCM) whose refractive index is real but whose permittivity and permeability are complex numbers. The real refractive index for this effective CCM is guaranteed by the real spectrum of the PCs, and the complex permittivity and permeability come from non-PT-symmetric loss-gain distributions. We show some interesting phenomena associated with CCM, such as the lasing effect.

scholarly journals Chiral Separation of rac-Propylene Oxide on Penicillamine Coated Gold NPs

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1716
Author(s):  
Nisha Shukla ◽  
Zachary Blonder ◽  
Andrew J. Gellman
Keyword(s):  
Propylene Oxide ◽  
Room Temperature ◽  
Adsorption Properties ◽  
Time Dependent ◽  
Prior Work ◽  
Au Nps ◽  
The Past ◽  
Racemic Mixtures ◽  
Enantioselective Adsorption ◽  
Gold Nps

The surfaces of chemically synthesized spherical gold NPs (Au-NPs) have been modified using chiral L- or D-penicillamine (Pen) in order to impart enantioselective adsorption properties. These chiral Au-NPs have been used to demonstrate enantioselective adsorption of racemic propylene oxide (PO) from aqueous solution. In the past we have studied enantioselective adsorption of racemic PO on L- or D-cysteine (Cys)-coated Au-NPs. This prior work suggested that adsorption of PO on Cys-coated Au-NPs equilibrates within an hour. In this work, we have studied the effect of time on the enantioselective adsorption of racemic PO from solution onto chiral Pen/Au-NPs. Enantioselective adsorption of PO on chiral Pen/Au-NPs is time-dependent but reaches a steady state after ~18 h at room temperature. More importantly, L- or D-Pen/Au-NPs are shown to adsorb R- or S-PO enantiospecifically and to separate the two PO enantiomers from racemic mixtures of RS-PO.

scholarly journals Time‐dependent warming amplification over the Tibetan Plateau during the past few decades

2020 ◽  
Vol 21 (10) ◽  
Author(s):  
Jianping Duan ◽  
Lun Li ◽  
Liang Chen ◽  
Haoxin Zhang
Keyword(s):  
Tibetan Plateau ◽  
Time Dependent ◽  
The Tibetan Plateau ◽  
The Past

scholarly journals A Variational Formulation of Nonequilibrium Thermodynamics for Discrete Open Systems with Mass and Heat Transfer

Entropy ◽  
2018 ◽  
Vol 20 (3) ◽  
pp. 163 ◽  
Author(s):  
François Gay-Balmaz ◽  
Hiroaki Yoshimura
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Variational Formulation ◽  
Evolution Equations ◽  
Nonequilibrium Thermodynamics ◽  
Open Systems ◽  
Internal Heat ◽  
Nonholonomic Constraints ◽  
Time Dependent ◽  
Nonlinear Constraint

We propose a variational formulation for the nonequilibrium thermodynamics of discrete open systems, i.e., discrete systems which can exchange mass and heat with the exterior. Our approach is based on a general variational formulation for systems with time-dependent nonlinear nonholonomic constraints and time-dependent Lagrangian. For discrete open systems, the time-dependent nonlinear constraint is associated with the rate of internal entropy production of the system. We show that this constraint on the solution curve systematically yields a constraint on the variations to be used in the action functional. The proposed variational formulation is intrinsic and provides the same structure for a wide class of discrete open systems. We illustrate our theory by presenting examples of open systems experiencing mechanical interactions, as well as internal diffusion, internal heat transfer, and their cross-effects. Our approach yields a systematic way to derive the complete evolution equations for the open systems, including the expression of the internal entropy production of the system, independently on its complexity. It might be especially useful for the study of the nonequilibrium thermodynamics of biophysical systems.

Load Control–Strain Control Isochronous Stress–Strain Curves for High Temperature Nonlinear Analysis

1995 ◽  
Vol 117 (2) ◽  
pp. 364-370 ◽  
Author(s):  
G. S. Bechtel ◽  
T. S. Cook
Keyword(s):  
Rupture Life ◽  
Nonlinear Behavior ◽  
General Purpose ◽  
Operating Conditions ◽  
Time Dependent ◽  
Load Control ◽  
New Techniques ◽  
Time Stepping ◽  
The Past ◽  
Computer Resources

Aircraft gas turbine components are subjected to severe operating conditions. High temperatures, large thermal strains, and mechanical loads combine to cause the material to undergo significant nonlinear behavior. In order to assure safe, durable components, it is necessary that analysis methods be available to predict the nonlinear deformation. General purpose finite element codes are available to perform elastic and viscoplastic analyses, but the analyses are expensive. Both large plastic and creep strain analyses can require significant computer resources, but typically a plastic solution is more economical to run than a time-stepping creep or viscoplastic model solution. For those applications where the deformation is principally time dependent, it is advantageous to include time-dependent creep effects in a “constant time” or “isochronous” analysis. Although this approach has been used in the past to estimate rupture life, this paper will present several significant new techniques for doing an isochronous analysis to analyze time-dependent deformation.

Dynamics of vortex–antivortex creation and annihilation in current-driven mesoscopic superconducting squares

2015 ◽  
Vol 29 (35n36) ◽  
pp. 1550247
Author(s):  
Xiao-Meng Liang ◽  
Guo-Qiao Zha
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Landau Theory ◽  
Symmetric Case ◽  
Time Dependent ◽  
Dynamical Process ◽  
Applied Bias ◽  
Ginzburg Landau ◽  
Dc Drive ◽  
Vortex Velocity

In this paper, based on the time-dependent Ginzburg–Landau theory, we study the dynamics of vortex–antivortex (V–Av) pairs in a mesoscopic superconducting square with a small hole under applied bias currents. For the sample with a centered hole, a V–Av pair can nucleate at the hole edges and moves in opposite directions perpendicular to applied constant DC drive. The influence of the external magnetic field on the (anti)vortex velocity and the lifetime of V–Av pairs is mainly investigated. Different modes in the dynamical process of the V–Av collision and annihilation are identified. Moreover, in the case when the hole is displaced from the center of the square, the V–Av dynamics behaves quite differently from the symmetric case due to the shift of the V–Av creation point.

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