Chaotic Scattering in the Regime of Weakly Overlapping Resonances

We measure the transmission and reflection amplitudes of microwaves in a resonator coupled to two antennas at room temperature in the regime of weakly overlapping resonances and in a frequency range of 3 to 16 GHz. Below 10.1 GHz the resonator simulates a chaotic quantum system. The distribution of the elements of the scattering matrix S is not Gaussian. The Fourier coefficients of S are used for a best fit of the autocorrelation function if S to a theoretical expression based on random--matrix theory. We find very good agreement below but not above 10.1 GHz

Characterization of Fluctuations of Impedance and Scattering Matrices in Wave Chaotic Scattering

In wave chaotic scattering, statistical fluctuations of the scattering matrix $S$ and the impedance matrix $Z$ depend both on universal properties and on nonuniversal details of how the scatterer is coupled to external channels. This paper considers the impedance and scattering variance ratios, $VR_z$ and $VR_s$, where $VR_z=Var[Z_{ij}]/\{Var[Z_{ii}]Var[Z_{jj}] \}^{1/2}$, $VR_s=Var[S_{ij}]/\{Var[S_{ii}]Var[S_{jj}] \}^{1/2}$, and $Var[.]$ denotes variance. $VR_z$ is shown to be a universal function of distributed losses within the scatterer. That is, $VR_z$ is independent of nonuniversal coupling details. This contrasts with $VR_s$ for which universality applies only in the large loss limit. Explicit results are given for $VR_z$ for time reversal symmetric and broken time reversal symmetric systems. Experimental tests of the theory are presented using data taken from scattering measurements on a chaotic microwave cavity.Comment: 6 pages, 5 figures, updated with referees' comment

Measuring the Lyapunov exponent using quantum mechanics

We study the time evolution of two wave packets prepared at the same initial state, but evolving under slightly different Hamiltonians. For chaotic systems, we determine the circumstances that lead to an exponential decay with time of the wave packet overlap function. We show that for sufficiently weak perturbations, the exponential decay follows a Fermi golden rule, while by making the difference between the two Hamiltonians larger, the characteristic exponential decay time becomes the Lyapunov exponent of the classical system. We illustrate our theoretical findings by investigating numerically the overlap decay function of a two-dimensional dynamical system.Comment: 9 pages, 6 figure

Strain-induced partially flat band, helical snake states, and interface superconductivity in topological crystalline insulators

Topological crystalline insulators in IV-VI compounds host novel topological surface states consisting of multi-valley massless Dirac fermions at low energy. Here we show that strain generically acts as an effective gauge field on these Dirac fermions and creates pseudo-Landau orbitals without breaking time-reversal symmetry. We predict the realization of this phenomenon in IV-VI semiconductor heterostructures, due to a naturally occurring misfit dislocation array at the interface that produces a periodically varying strain field. Remarkably, the zero-energy Landau orbitals form a flat band in the vicinity of the Dirac point, and coexist with a network of snake states at higher energy. We propose that the high density of states of this flat band gives rise to interface superconductivity observed in IV-VI semiconductor multilayers at unusually high temperatures, with non-BCS behavior. Our work demonstrates a new route to altering macroscopic electronic properties to achieve a partially flat band, and paves the way for realizing novel correlated states of matter.Comment: Accepted by Nature Physic

Can we Rationally Learn to Coordinate?

In this paper we examine the issue whether individual rationality considerations are sufficient to guarantee that individuals will learn to coordinate. This question is central in any discussion of whether social phenomena (read: conventions) can be explained in terms of a purely individualistic approach. We argue that the positive answers to this general question that have been obtained in some recent work require assumptions which incorporate some convention. This conclusion may be seen as supporting the viewpoint of institutional individualism in contrast to psychological individualism

Studies on Fabrication of Ag/HgBaCaCuO/CdSe Heterostructures by Pulse-Electrodeposition Route

Metal/superconductor/semiconductor (Ag/HgBaCaCuO/CdSe) heterostructures have been successfully fabricated using pulse-electrodeposition technique. The electrochemical parameters are optimized and diffusion free growth of CdSe onto Ag/HgBaCaCuO was obtained by employing under-potential deposition and by studying nucleation and growth mechanism during deposition. The heterostructures are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM), scanning electron microscopy (SEM) studies and low temperature four probe electrical resistivity measurements. After the deposition of CdSe the critical transition temperature of HgBaCaCuO films was found be increased from 115 K with Jc = 1.7 x 103 A/cm2 to 117.2 K with Jc = 1.91 x 103 A/cm2. When the heterostructure was irradiated with red He-Ne laser (2 mW), the Tc was further enhanced to 120.3 K with Jc = 3.7 x 103 A/cm2. This increase in superconducting parameters of HgBaCaCuO in Ag/ HgBaCaCuO/CdSe heterostructure has been explained at length in this paper. Keywords. Electrodeposition; Hg-based cuprate; semiconductor; heterostructures; electrical properties. PACS Nos 81.15.Pq; 74.72.Gr; 78.40.Fy; 84.37; 73.40 *E-mail: [email protected], [email protected]: 22 Pages, 12 Figures. Submitted to Semiconductor Science and Technology. Submitted to Semiconductor Science and Technolog

Neutrophil Extracellular Traps in Breast Cancer and Beyond: Current Perspectives on NET Stimuli, Thrombosis and Metastasis, and Clinical Utility for Diagnosis and Treatment

Abstract The formation of neutrophil extracellular traps (NETs), known as NETosis, was first observed as a novel immune response to bacterial infection, but has since been found to occur abnormally in a variety of other inflammatory disease states including cancer. Breast cancer is the most commonly diagnosed malignancy in women. In breast cancer, NETosis has been linked to increased disease progression, metastasis, and complications such as venous thromboembolism. NET-targeted therapies have shown success in preclinical cancer models and may prove valuable clinical targets in slowing or halting tumor progression in breast cancer patients. We will briefly outline the mechanisms by which NETs may form in the tumor microenvironment and circulation, including the crosstalk between neutrophils, tumor cells, endothelial cells, and platelets as well as the role of cancer-associated extracellular vesicles in modulating neutrophil behavior and NET extrusion. The prognostic implications of cancer-associated NETosis will be explored in addition to development of novel therapeutics aimed at targeting NET interactions to improve outcomes in patients with breast cancer

For reflexivity as an epistemic criterion of ontological coherence and virtuous social theorizing

This article offers an approach that combines, on the one hand, the philosophical notion of reflexivity, which is related to the ideas of self-reference and paradox, and, on the other hand, the sociological discussion of epistemic reflexivity as a problem of coherence, which was mainly initiated by certain branches of ethnomethodology and social constructionism. This combinatory approach argues for reflexivity as an epistemic criterion of ontological coherence, which suggests that social ontologies should account for the possibility of self-reflective subjectivity – for otherwise they result in a paradoxical conclusion according to which a social scientist reflects on her or his ontological commitments even though these commitments deny her or him the capacity for self-reflection. This analysis presupposes that all human sciences are categorically premised on social ontologies; and it argues for an analytical distinction between self-reflection, which refers to the agential capacity for reflecting on one’s own commitments, and the epistemic criterion of reflexivity hereby proposed. These two analytically distinct though interdependent socio-theoretical concepts are frequently conflated in the literature; thus, this article also aims at a ‘clearing of the ground’ that can be of categorical use to the human sciences