4,608 research outputs found
Helical damping and anomalous critical non-Hermitian skin effect
Non-Hermitian skin effect and critical skin effect are unique features of
non-Hermitian systems. In this Letter, we study an open system with its
dynamics of single-particle correlation function effectively dominated by a
non-Hermitian damping matrix, which exhibits skin effect, and
uncover the existence of a novel phenomenon of helical damping. When adding
perturbations that break anomalous time reversal symmetry to the system, the
critical skin effect occurs, which causes the disappearance of the helical
damping in the thermodynamic limit although it can exist in small size systems.
We also demonstrate the existence of anomalous critical skin effect when we
couple two identical systems with skin effect. With the help of
non-Bloch band theory, we unveil that the change of generalized Brillouin zone
equation is the necessary condition of critical skin effect.Comment: 7+5 pages, 4+5 figure
A Chronology of International Business Cycles Through Non-parametric Decoding
This paper introduces a new empirical strategy for the characterization of business cycles. It combines non-parametric decoding methods that classify a series into expansions and recessions but does not require specification of the underlying stochastic process generating the data. It then uses network analysis to combine the signals obtained from different economic indicators to generate a unique chronology. These methods generate a record of peak and trough dates comparable, and in one sense superior, to the NBER’s own chronology. The methods are then applied to 22 OECD countries to obtain a global business cycle chronology.decoding, hierarchical factor segmentation, network analysis, business cycles
A chronology of international business cycles through non-parametric decoding
This paper introduces a new empirical strategy for the characterization of business cycles. It combines non-parametric decoding methods that classify a series into expansions and recessions but does not require specification of the underlying stochastic process generating the data. It then uses network analysis to combine the signals obtained from different economic indicators to generate a unique chronology. These methods generate a record of peak and trough dates comparable, and in one sense superior, to the NBER's own chronology. The methods are then applied to 22 OECD countries to obtain a global business cycle chronology.
On fixed effects estimation in spline-based semiparametric regression for spatial data
Spline surfaces are often used to capture spatial variability sources in linear mixed-effects models, without imposing a parametric covariance structure on the random effects. However, including a spline component in a semiparametric model may change the estimated regression coefficients, a problem analogous to spatial confounding in spatially correlated random effects. Our research aims to investigate such effects in spline-based semiparametric regression for spatial data. We discuss estimators\u27 behavior under the traditional spatial linear regression, how the estimates change in spatial confounding-like situations, and how selecting a proper tuning parameter for the spline can help reduce bias
Optically-Nonactive Assorted Helices Array with Interchangeable Magnetic/Electric Resonance
We report here the designing of optically-nonactive metamaterial by
assembling metallic helices with different chirality. With linearly polarized
incident light, pure electric or magnetic resonance can be selectively
realized, which leads to negative permittivity or negative permeability
accordingly. Further, we show that pure electric or magnetic resonance can be
interchanged at the same frequency band by merely changing the polarization of
incident light for 90 degrees. This design demonstrates a unique approach to
construct metamaterial.Comment: 15 pages, 4 figure
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