Real Polarization Research Articles

Convergence of stochastic-extended Lagrangian molecular dynamics method for polarizable force field simulation

Extended Lagrangian molecular dynamics (XLMD) is a general method for performing molecular dynamics simulations using quantum and classical many-body potentials. Recently several new XLMD schemes have been proposed and tested on several classes of many-body polarization models such as induced dipoles or Drude charges, by creating an auxiliary set of these same degrees of freedom that are reversibly integrated through time. This gives rise to a singularly perturbed Hamiltonian system that provides a good approximation to the time evolution of the real mutual polarization field. To further improve upon the accuracy of the XLMD dynamics in the context of classical polarizable force field simulation, and to potentially extend it to other many-body potentials, we introduce a stochastic modification which leads to a set of singularly perturbed Langevin equations with degenerate noise. We prove that the resulting Stochastic-XLMD converges to the accurate dynamics, and the convergence rate is both sharp and is independent of the accuracy of the initial polarization field. We carefully study the scaling of the damping factor and numerical noise for efficient numerical simulation for Stochastic-XLMD, and we demonstrate the effectiveness of the method for water molecules described by a polarizable force field.

Edelstein effect in pseudospin Dirac systems

Edelstein effect of spin polarization means an electric field could induce a magnetization in nonmagnetic materials. This effect can be well understood by a Zeeman-like term due to an effective magnetic field in spin-orbit coupling systems. We propose a mechanism of current-induced spin polarization, where the real spin is not directly related to the effective magnetic field induced by an electric field. This effective field only results in the polarization of a general spin. Then the real spin polarization is generated through the coupling between the real spin and the general spin in pseudospin Dirac systems with low symmetry. The values of our spin polarization and the conventional one may have the same order of magnitude though ours involves two processes, which has been further verified by the numerical calculation in the $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}{\mathrm{WTe}}_{2}$ distorted monolayer. It will be helpful for the deeper understanding of the current-induced spin polarization in pseudospin Dirac materials.

Convergence of polarizations, toric degenerations, and Newton–Okounkov bodies

Let $X$ be a smooth irreducible complex algebraic variety of dimension $n$ and $L$ a very ample line bundle on $X$. Given a toric degeneration of $(X,L)$ satisfying some natural technical hypotheses, we construct a deformation $\{J_s\}$ of the complex structure on $X$ and bases $\mathcal{B}_s$ of $H^0(X,L, J_s)$ so that $J_0$ is the standard complex structure and, in the limit as $s \to \infty$, the basis elements approach dirac-delta distributions centered at Bohr-Sommerfeld fibers of a moment map associated to $X$ and its toric degeneration. The theory of Newton-Okounkov bodies and its associated toric degenerations shows that the technical hypotheses mentioned above hold in some generality. Our results significantly generalize previous results in geometric quantization which prove independence of polarization between Kahler quantizations and real polarizations. As an example, in the case of general flag varieties $X=G/B$ and for certain choices of $\lambda$, our result geometrically constructs a continuous degeneration of the (dual) canonical basis of $V_{\lambda}^*$ to a collection of dirac delta functions supported at the Bohr-Sommerfeld fibres corresponding exactly to the lattice points of a Littelmann-Berenstein-Zelevinsky string polytope $\Delta_{\underline{w}_0}(\lambda) \cap \mathbb{Z}^{\dim(G/B)}$.

The Vulnerable Data Subject: A Gendered Data Subject?

Vulnerability is an emerging topic in many different fields, but in data protection and privacy the discussion has rarely engaged with gender studies. This paper investigates the notion of the ‘vulnerable data subject’ from a gender perspective, to question whether gender should be regarded as factor of vulnerability at all, and, if yes, how. In addition, what do these reflections tell us about the (gendered or un-gendered) notion of ‘standard data subject’? In the EU data protection law (GDPR), even though the term ‘vulnerable data subject’ is only incidentally mentioned and referring explicitly just to children, several Data Protection Authorities (e.g., in Spain and Poland) have considered “being female” as a potential source of data subject’s vulnerability (e.g., in case of consumers victims of sex-related crimes). The US privacy tort - as originally conceived - was built off gendered notions of female modesty, suggesting women were vulnerable, and thus connecting women’s privacy claims to the ‘wrong kind of privacy’. Looking at the history and foundations of privacy and data protection law, surface questions such as whether the ‘average data subject’ in privacy and data protection legislation is, by default, a man, and, whether women might have to be regarded as vulnerable data subjects just because they are women. This article then look into law and economics analysis of consumers’ behaviour, but also political philosophy and, in particular, gender studies, where we can observe a real intellectual polarisation: on the one hand the vulnerability universalist approach, according to which every human is vulnerable, otherwise vulnerability would be a stigmatizing label; on the other hand the particularistic approach, according to which some subjects are more vulnerable than others (in particular, women are more vulnerable - i.e., subject to adverse effects - than men in many contexts: workplace, education, etc.). A third way might be the theory of Luna, based on a contextual and relational (even situational) nature of vulnerability. This solution is compatible with the layered risk-based approach in the GDPR, but also with the intersectional approach in gender studies. This “third way” might be also a cautious solution to the ambiguous and inconsistent focus on vulnerability both in the European Commission documents and proposed legislation (e.g., the EU Regulation AI) and in the EU data protection practice (considering, e.g., the ineffective protection of children).

A universal method to improve the consistency between simulated results of celestial distribution of polarized light from analytical models and measured data

The skylight polarization models can simulate the polarization state distribution of the skylight. These models are essential tools to extract the relation between the polarization distribution of skylight and the characteristic parameters of the atmosphere. Since the actual skylight polarization mode can be affected by various factors, the results obtained from the traditional analytical model are very different from those obtained from the field experiment. To improve the consistency between simulated results of analytical models and the real skylight polarization mode distribution, we introduce two modifications into analytical models: (1) the influence on light intensity under clear sky condition; (2) the flexibility of choosing different imaging models with accordance to experiment equipments. The experimental results demonstrate that the simulation results obtained from the Rayleigh model and singularity theory model under the proposed modifications are more consistent with measured skylight polarization mode data.

Combined phase offset channel estimation method for optical OFDM/OQAM

On the basis of coherent optical orthogonal frequency-division-multiplexing (CO-OFDM), CO-OFDM/ offset quadrature amplitude modulation (CO-OFDM/OQAM) improves the spectrum efficiency by utilizing specially designed filter banks to eliminate the cyclic prefix (CP) inserted between consecutive OFDM blocks and decreases the demanding of guard band between two channels, being a promising candidate for the next generation optical transmission link. Due to the relaxation of the orthogonal condition from the complex field to the real field, chromatic Dispersion (CD) and polarization mode dispersion (PMD) bring serious intrinsic imaginary interference (IMI) to an optical OFDM/OQAM system. Channel estimation schemes based on the interference approximation method (IAM) have been proved to be effective in suppressing the IMI with low complexity. For the IAMs, increasing the power of the pseudo pilot could decrease the effects of amplified spontaneous emission (ASE) noise and other frequency domain residual error on the channel estimation accuracy. In most of the previous reported IAM works, pilot blocks were designed according to the structure of the center pilot block loaded, while the two side pilots nulled for simplicity. However, the power of the pseudo pilot under this method did not reach the maximum, resulting in non-optimal channel estimation accuracy. In this paper, channel estimation method based on the combined phase offset (CMPO) is proposed and systematically discussed. For the proposed method, three consecutive full loaded blocks are treated as the pilot blocks and the optimal pilot structure have been obtained by utilizing the maximum likelihood algorithm. As validated by numerous Montel Carlo simulations results, system robustness against IMI, phase noised induced interference, and nonlinear effect have been improved significantly, thanks to CMPO.

P.648 Pre-weaning maternal rat antibiotic exposure leads to long-term neurobehavioral and neurochemical outcome in rat offspring

On the basis of coherent optical orthogonal frequency-division-multiplexing (CO-OFDM), CO-OFDM/ offset quadrature amplitude modulation (CO-OFDM/OQAM) improves the spectrum efficiency by utilizing specially designed filter banks to eliminate the cyclic prefix (CP) inserted between consecutive OFDM blocks and decreases the demanding of guard band between two channels, being a promising candidate for the next generation optical transmission link. Due to the relaxation of the orthogonal condition from the complex field to the real field, chromatic Dispersion (CD) and polarization mode dispersion (PMD) bring serious intrinsic imaginary interference (IMI) to an optical OFDM/OQAM system. Channel estimation schemes based on the interference approximation method (IAM) have been proved to be effective in suppressing the IMI with low complexity. For the IAMs, increasing the power of the pseudo pilot could decrease the effects of amplified spontaneous emission (ASE) noise and other frequency domain residual error on the channel estimation accuracy. In most of the previous reported IAM works, pilot blocks were designed according to the structure of the center pilot block loaded, while the two side pilots nulled for simplicity. However, the power of the pseudo pilot under this method did not reach the maximum, resulting in non-optimal channel estimation accuracy. In this paper, channel estimation method based on the combined phase offset (CMPO) is proposed and systematically discussed. For the proposed method, three consecutive full loaded blocks are treated as the pilot blocks and the optimal pilot structure have been obtained by utilizing the maximum likelihood algorithm. As validated by numerous Montel Carlo simulations results, system robustness against IMI, phase noised induced interference, and nonlinear effect have been improved significantly, thanks to CMPO.

Geometric Quantization of the 1 : 1 Oscillator

We study geometric quantization of the 1 : 1 in terms of a singular real polarization given by fibres of its energy momentum map.

Strict Deformation Quantization via Geometric Quantization in the Bieliavsky Plane

Using standard techniques from geometric quantization, we rederive the integral product of functions on ℝ2 (non-Euclidian) which was introduced by Pierre Bieliavsky as a contribution to the area of strict quantization. More specifically, by pairing the nontransverse real polarization on the pair groupoid ℝ2×ℝ¯2, we obtain the well-defined integral transform. Together with a convolution of functions, which is a natural deformation of the usual convolution of functions on the pair groupoid, this readily defines the Bieliavsky product on a subset of L2ℝ2.

Modelling competitive sorption and plasticization of glassy polymeric membranes used in biogas upgrading

A mathematical model of membrane performance is developed that incorporates fugacity-dependent permeabilities, competitive sorption, penetrant blocking and plasticization effects. The model also accounts for non-isothermal operation and includes real gas behavior and concentration polarization. Importantly, the model simultaneously considers plasticization caused by water vapor (H2O) and carbon dioxide (CO2). A simulation of biogas (composed of methane (CH4), CO2 and H2O) upgrading is performed using the new model and compared to models that use constant and pure gas permeability. Relative to these simplified models, the new model predicts differences up to 2% and 18% in CH4 recovery at low feed flowrates and the difference in CO2 removal can be as significant as 50%. Furthermore, simulations with and without water vapor in the feed give predictions that are 4.5%–34% different. The differences are attributed to the changes in fugacity-dependent permeabilities, particularly the sensitivity of these permeabilities to feed composition. An analysis indicates that the contributions of competitive sorption and penetrant blocking/plasticization to these differences is 19% and 32% in terms of CH4 recovery and CO2 removal, respectively. The remaining differences are due to real gas behavior, while concentration polarization has a negligible impact under the chosen conditions.

Direct observation of surface polarization at hybrid perovskite/Au interfaces by dark transient experiments

A distinctive feature of hybrid perovskite light-absorbing materials is the non-negligible ionic conductivity influencing photovoltaic performance and stability. Moving ions or vacancies can naturally accumulate at the outer interfaces (electrode polarization) upon biasing. Contrary to that approach, a modulation of conductive or recombination properties could manifest as an alteration in the low-frequency part of the impedance response, either producing inductive or large capacitive features. Under this last view, capacitances are not the response of polarized structures or charging mechanisms, but result from the modulation of currents. This work intends to provide pieces of evidence that assist us in distinguishing between these two dissimilar mechanisms, namely, real charge polarization and delayed current effects under bias in the dark. The analysis relays upon an experimental technique based on transient charging signals using the Sawyer-Tower circuit. Instead of applying an alternating small perturbation over a steady-state voltage (differential capacitance method), transient charging measures the resulting polarization upon a large bias step under the suppression of dc currents. Our findings reveal that real steady-state charge is indeed induced by the applied voltage in the dark, easily interpreted by means of charged real capacitors with values much larger than the geometrical capacitance of the film. The connection between that polarization and the charging of perovskite/contact interfaces is highlighted.

On the Positivity of Kirillov’s Character Formula

We give a direct proof for the positivity of Kirillov’s character on the convolution algebra of smooth, compactly supported functions on a connected, simply connected nilpotent Lie group G. Then we use this positivity result to construct a representation of G × G and establish a G × G-equivariant isometric isomorphism between our representation and the Hilbert–Schmidt operators on the underlying representation of G. In fact, we provide a framework in which we establish the positivity of Kirillov’s character for coadjoint orbits of groups such as $\text {SL}(2, \mathbb {R})$ under additional hypotheses that are automatically satisfied in the nilpotent case. These hypotheses include the existence of a real polarization and the Pukanzsky condition.

Electric field dependence of ferroelectric stability in BiFeO3 thin films co-doped with Er and Mn

Bi0.9Er0.1Fe1−xMnxO3 (BEFMxO, x = 0.00–0.03) films are synthesized by a sol–gel technique. The BEFO film exhibits a conduction mechanism based on electron tunneling. The high applied electric field causes dissociation of the defect complex, and the resulting oxygen vacancies contribute to fake polarization. Consequently, the BEFO film has poor polarization stability at high applied electric fields. Coexistence of two phases (with space groups R3c:H and R3m:R) and reduced concentrations of oxygen vacancies and Fe2+ in BEFMxO are achieved by co-doping with Er and Mn. The presence of bulk-based conduction in the BEFMxO films then leads to ferroelectric domain switching contributing to the real polarization and to excellent ferroelectric stability. In addition, the BEFM0.02O film shows a typical symmetrical butterfly curve, the highest remnant polarization of ~109 μC/cm2, and the highest switching current of ~1.66 mA. It also has the smallest oxygen vacancy concentration and thus the smallest amount of defect complex, which means that there are fewer pinning effects on ferroelectric domains and therefore excellent ferroelectric stability. This excellent ferroelectric stability makes the BEFMxO films obtain good stability and reliability in the application of ferroelectric memory devices.

Electrode performance of La2NiO4+δ cathodes in contact with La0.9Sr0.1ScO3−δ proton-conducting oxide

Ruddlesden-Popper-structured La2NiO4+δ oxide has been applied for the first time as the cathode for La0.9Sr0.1ScO3−δ proton-conducting oxide. The chemical compatibility of the electrode and electrolyte materials has been studied. Electrode performance has been investigated by means of impedance spectroscopy in dry and wet air conditions in the temperature range of 600–800 °C. Real polarization resistance values were calculated taking into account the shunt effect of electronic hole conductivity in the electrolyte.

Optical design of a simultaneous polarization and multispectral imaging system with a common aperture

ABSTRACTA polarization and multispectral imaging system enables the acquirement of spatial, polarization and multispectral information of a target simultaneously, thereby improving capability in the detection and identification of low-contrast targets-an increasingly important attribute in many applications. In this work, we propose a simultaneous polarization and multispectral imaging system with a common aperture working at visible, mid-wave infrared and long-wave infrared wavebands. Two dichroic mirrors are used to spectrally split the beams into these three bands. For the visible spectrum, a division-of-focal-plane polarimeter is employed to acquire polarization information. Division-of-aperture-plane polarimeters with a cooled and uncooled detector are exploited in the mid-wave infrared and long-wave infrared, respectively. The division-of-focal-plane and division-of-aperture-plane polarimeters enable our system to achieve real time polarization imaging, which is suitable for moving targets. Simulation results indicate that our proposed system can meet the diverse imaging requirements in each waveband.

Models of inhomogeneous polarization of ferroelectrics and their practical application

A three-dimensional mathematical model is proposed that describes the ferroelectric response of polycrystalline ferroelectrics to an electric field in the absence of mechanical stresses. It is based on the separation of the switching process into two related parts: the rotation of the spontaneous polarization vectors and the destruction of the domain wall fixing mechanisms. For each of the parts, the energy costs are calculated, which are the components of the energy balance in the real polarization process. The constitutive relations for the induced and residual components of the polarization vector of the representative volume are obtained. A number of numerical experiments were performed, which showed good agreement with the experimental data.

Bridging the Physics and Chemistry of Graphene(s): From Hückel's Aromaticity to Dirac's Cones and Topological Insulators.

By bridging graphene and benzene through a well-defined sequence of polycyclic aromatic hydrocarbons and their inherent shell structure, it is shown that graphene is actually a coherent arrangement of interwoven benzene molecules, coordinated by aromaticity, shell structure, and topology, all interrelated and microscopically realized through dynamical flipping of the atomic pz-orbitals, playing the role of pseudospins or "qubits". This renders graphene resonance structure, "resonating" between two complementary aromaticity patterns, involving 2k, k → ∞ Kekulé type of resonances, resulting in "robust electronic coherence", with a dual "molecular crystalline" nature, and two valence-conduction bands of opposite parity, driven by inversion symmetry competition, which is essentially a "molecule-versus-crystal" competition, in accordance with topological insulators and many-body theory. The "average picture" converges to the usual band structure with two aromatic π-electrons per ring, and with the fingerprints of inversion competition at the D3h-symmetric Dirac points, which for rectangular nanographene(s) appear as gapless topological edge states without real spin polarization, in contrast to opposite claims.

Geometric quantization of almost toric manifolds

Kostant gave a model for the real geometric quantization associated to polarizations via the cohomology associated to the sheaf of flat sections of a pre-quantum line bundle. This model is well-adapted for real polarizations given by integrable systems and toric manifolds. In the latter case, the cohomology can be computed counting integral points inside the associated Delzant polytope. In this article we extend Kostant's geometric quantization to semitoric integrable systems and almost toric manifolds. In these cases the dimension of the acting torus is smaller than half of the dimension of the manifold. In particular, we compute the cohomology groups associated to the geometric quantization if the real polarization is the one associated to an integrable system with focus-focus type singularities in dimension four. As application we determine models for the geometric quantization of K3 surfaces, a spin-spin system, the spherical pendulum, and a spin-oscillator system under this scheme.

The geometric quantizations and the measured Gromov–Hausdorff convergences

On a compact symplectic manifold $(X,\omega)$ with a prequantum line bundle $(L,\nabla,h)$, we consider the one-parameter family of $\omega$-compatible complex structures which converges to the real polarization coming from the Lagrangian torus fibration. There are several researches which show that the holomorphic sections of the line bundle localize at Bohr-Sommerfeld fibers. In this article we consider the one-parameter family of the Riemannian metrics on the frame bundle of $L$ determined by the complex structures and $\nabla,h$, and we can see that their diameters diverge. If we fix a base point in some fibers of the Lagrangian fibration we can show that they measured Gromov-Hausdorff converge to some pointed metric measure spaces with the isometric $S^1$-actions, which may depend on the choice of the base point. We observe that the properties of the $S^1$-actions on the limit spaces actually depend on whether the base point is in the Bohr-Sommerfeld fibers or not.

Directly extracting the authentic basis of cylindrical vector beams by a pump-probe technique in an atomic vapor

The projective measurement of light polarization is usually employed by using a combination of a quarter-waveplate, half-waveplate, and polarizing beam splitter. This configuration is also widely used for exploring quantum states. However, this kind of measurement destroys the real polarization state of the target. Here, an effective measurement configuration to extract the “authentic basis” of cylindrical vector beams with arbitrary polarization distribution in an atomic vapor is presented. An intense pump beam induces a distribution of atoms at different Zeeman sublevels, which allows for the extraction of the special polarization state of a counter propagated weak probe beam. The extracted part still maintains the original polarization and the vortex phase. Different orders of cylindrical vector beams are tested in this configuration, and the authentic basis of cylindrical vector beams is extracted as predicted. This work has potential applications in atomic physics and polarization optics. Furthermore, it provides a reference for the quantum projective measurement based on atom-optical devices.