Evidence of Skyrmion excitations about ν=1\nu =1 in n-Modulation Doped Single Quantum Wells by Inter-band Optical Transmission

We observe a dramatic reduction in the degree of spin-polarization of a two-dimensional electron gas in a magnetic field when the Fermi energy moves off the mid-point of the spin-gap of the lowest Landau level, $\nu=1$. This rapid decay of spin alignment to an unpolarized state occurs over small changes to both higher and lower magnetic field. The degree of electron spin polarization as a function of $\nu$ is measured through the magneto-absorption spectra which distinguish the occupancy of the two electron spin states. The data provide experimental evidence for the presence of Skyrmion excitations where exchange energy dominates Zeeman energy in the integer quantum Hall regime at $\nu=1$

Effects of seawater and deionized water at 0 to 80 deg C on the flexural properties of a glass/epoxy composite

The effect on the flexural properties of a glass/epoxy composite of immersion in deionized water or seawater at 0, 25, and 80 C for 451 hr was examined. The percent weight gain at 0 and 25 C was low (0.06 to 0.17 percent) and there was no significant change in the flexural properties for these environmental conditions. At 80 C there was a decrease in the flexural strength of 17 and 20 percent in seawater and deionized water, respectively. This is a comparison to control samples exposed to 80 C heat alone. These decreases were found to be nearly reversible once the samples were dried. Optical microscopy did not reveal cracking of the matrix. The flexural modulus was essentially unaffected by exposure to deionized water and seawater at 80 C

Mesonephric-like adenocarcinoma of the ovary with co-existent endometriosis: A case report and review of the literature

© 2020 The Authors Introduction: Mesonephric-like adenocarcinoma (MLA) is a rare malignant gynecologic neoplasm occurring in the uterine corpus and ovary. The morphological and immunohistochemical characteristics of MLA closely resemble that of cervical mesonephric adenocarcinomas, but whether they share a common histogenesis remains unclear. Two main theories for histogenesis of MLAs include the origination of these neoplasms from mesonephric remnants, as is the case for cervical mesonephric adenocarcinoma, versus the differentiation along a mesonephric pathway from Mullerian lesions. Case: A 67-year-old presented after a right salpingo-oophorectomy for a complex ovarian mass revealed a mesonephric-like adenocarcinoma of the ovary and endometriosis. She underwent a total abdominal hysterectomy, pelvic lymphadenectomy, and infra-colic omentectomy, and diagnosed with Stage IA mesonephric-like adenocarcinoma of the ovary. At 18 months post-operatively, the patient developed flank and abdominal pain and was found to have multiple sites of recurrent disease. She was referred to medical oncology for chemotherapy as she was not a candidate for surgical cytoreduction. Discussion: This case demonstrates the aggressive nature of ovarian MLA and the need for a multidisciplinary approach when determining the treatment. In addition, this case provides further evidence to support the theory that at least a subset of MLAs arises from a Mullerian lesion which then differentiates down a mesonephric pathway

How to find the holonomy algebra of a Lorentzian manifold

Manifolds with exceptional holonomy play an important role in string theory, supergravity and M-theory. It is explained how one can find the holonomy algebra of an arbitrary Riemannian or Lorentzian manifold. Using the de~Rham and Wu decompositions, this problem is reduced to the case of locally indecomposable manifolds. In the case of locally indecomposable Riemannian manifolds, it is known that the holonomy algebra can be found from the analysis of special geometric structures on the manifold. If the holonomy algebra $\mathfrak{g}\subset\mathfrak{so}(1,n-1)$ of a locally indecomposable Lorentzian manifold $(M,g)$ of dimension $n$ is different from $\mathfrak{so}(1,n-1)$, then it is contained in the similitude algebra $\mathfrak{sim}(n-2)$. There are 4 types of such holonomy algebras. Criterion how to find the type of $\mathfrak{g}$ are given, and special geometric structures corresponding to each type are described. To each $\mathfrak{g}$ there is a canonically associated subalgebra $\mathfrak{h}\subset\mathfrak{so}(n-2)$. An algorithm how to find $\mathfrak{h}$ is provided.Comment: 15 pages; the final versio

Predictions for the Cosmogenic Neutrino Flux in Light of New Data from the Pierre Auger Observatory

The Pierre Auger Observatory (PAO) has measured the spectrum and composition of the ultrahigh energy cosmic rays with unprecedented precision. We use these measurements to constrain their spectrum and composition as injected from their sources and, in turn, use these results to estimate the spectrum of cosmogenic neutrinos generated in their propagation through intergalactic space. We find that the PAO measurements can be well fit if the injected cosmic rays consist entirely of nuclei with masses in the intermediate (C, N, O) to heavy (Fe, Si) range. A mixture of protons and heavier species is also acceptable but (on the basis of existing hadronic interaction models) injection of pure light nuclei (p, He) results in unacceptable fits to the new elongation rate data. The expected spectrum of cosmogenic neutrinos can vary considerably, depending on the precise spectrum and chemical composition injected from the cosmic ray sources. In the models where heavy nuclei dominate the cosmic ray spectrum and few dissociated protons exceed GZK energies, the cosmogenic neutrino flux can be suppressed by up to two orders of magnitude relative to the all-proton prediction, making its detection beyond the reach of current and planned neutrino telescopes. Other models consistent with the data, however, are proton-dominated with only a small (1-10%) admixture of heavy nuclei and predict an associated cosmogenic flux within the reach of upcoming experiments. Thus a detection or non-detection of cosmogenic neutrinos can assist in discriminating between these possibilities.Comment: 10 pages, 7 figure

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2

We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum, and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain, and to find the shift rates and Gr\"uneisen parameters of two Raman modes in monolayer MoS2. Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron sized areas, and report evidence for the strain tuning of higher level optical transitions.Comment: Nano Lett., Article ASA

Non-Perturbative Production of Multi-Boson States and Quantum Bubbles

The amplitude of production of $n$ on-mass-shell scalar bosons by a highly virtual field $\phi$ is considered in a $\lambda \phi^4$ theory with weak coupling $\lambda$ and spontaneously broken symmetry. The amplitude of this process is known to have an $n!$ growth when the produced bosons are exactly at rest. Here it is shown that for $n \gg 1/\lambda$ the process goes through `quantum bubbles', i.e. quantized droplets of a different vacuum phase, which are non-perturbative resonant states of the field $\phi$. The bubbles provide a form factor for the production amplitude, which rapidly decreases above the threshold. As a result the probability of the process may be heavily suppressed and may decrease with energy $E$ as $\exp (-const \cdot E^a)$, where the power $a$ depends on the number of space dimensions. Also discussed are the quantized states of bubbles and the amplitudes of their formation and decay.Comment: 20 pages in LaTeX + 3 figures (fugures not included, hardcopy available on request), TPI-MINN-93/20-

On the Number of Iterations for Dantzig-Wolfe Optimization and Packing-Covering Approximation Algorithms

We give a lower bound on the iteration complexity of a natural class of Lagrangean-relaxation algorithms for approximately solving packing/covering linear programs. We show that, given an input with $m$ random 0/1-constraints on $n$ variables, with high probability, any such algorithm requires $\Omega(\rho \log(m)/\epsilon^2)$ iterations to compute a $(1+\epsilon)$-approximate solution, where $\rho$ is the width of the input. The bound is tight for a range of the parameters $(m,n,\rho,\epsilon)$. The algorithms in the class include Dantzig-Wolfe decomposition, Benders' decomposition, Lagrangean relaxation as developed by Held and Karp [1971] for lower-bounding TSP, and many others (e.g. by Plotkin, Shmoys, and Tardos [1988] and Grigoriadis and Khachiyan [1996]). To prove the bound, we use a discrepancy argument to show an analogous lower bound on the support size of $(1+\epsilon)$-approximate mixed strategies for random two-player zero-sum 0/1-matrix games

The kernel of the edth operators on higher-genus spacelike two-surfaces

The dimension of the kernels of the edth and edth-prime operators on closed, orientable spacelike 2-surfaces with arbitrary genus is calculated, and some of its mathematical and physical consequences are discussed.Comment: 12 page

Sensitivity of quantum chaotic wavefunction intensities to changes in external perturbations

We examine the sensitivity of wavefunction intensities in chaotic quantum systems to small changes in an arbitrary external perturbation. A universal scaling is proposed for all three Dyson ensembles and a novel theoretical approach is used to determine exact expressions for systems which violate T-invariance. Analytical results are compared with numerical simulations of tight-binding Anderson Hamiltonians.Comment: 7 pages, RevTeX 3.0, 3 Postscript figure