Search for Sterile Neutrinos with a Radioactive Source at Daya Bay

The far site detector complex of the Daya Bay reactor experiment is proposed as a location to search for sterile neutrinos with > eV mass. Antineutrinos from a 500 kCi 144Ce-144Pr beta-decay source (DeltaQ=2.996 MeV) would be detected by four identical 20-ton antineutrino targets. The site layout allows flexible source placement; several specific source locations are discussed. In one year, the 3+1 sterile neutrino hypothesis can be tested at essentially the full suggested range of the parameters Delta m^2_{new} and sin^22theta_{new} (90% C.L.). The backgrounds from six nuclear reactors at >1.6 km distance are shown to be manageable. Advantages of performing the experiment at the Daya Bay far site are described

Stripe phases in high-temperature superconductors

Stripe phases are predicted and observed to occur in a class of strongly-correlated materials describable as doped antiferromagnets, of which the copper-oxide superconductors are the most prominent representative. The existence of stripe correlations necessitates the development of new principles for describing charge transport, and especially superconductivity, in these materials.Comment: 5 pp, 1 color eps fig., to appear as a Perspective in Proc. Natl. Acad. Sci. US

Scattering by flexural phonons in suspended graphene under back gate induced strain

We have studied electron scattering by out-of-plane (flexural) phonon modes in doped suspended graphene and its effect on charge transport. In the free-standing case (absence of strain) the flexural branch shows a quadratic dispersion relation, which becomes linear at long wavelength when the sample is under tension due to the rotation symmetry breaking. In the non-strained case, scattering by flexural phonons is the main limitation to electron mobility. This picture changes drastically when strains above $\bar{u}=10^{-4} n(10^{12}\,\text{cm}^{-2})$ are considered. Here we study in particular the case of back gate induced strain, and apply our theoretical findings to recent experiments in suspended graphene.Comment: 4 pages, 3 figures, published versio

Learning to Extract Motion from Videos in Convolutional Neural Networks

This paper shows how to extract dense optical flow from videos with a convolutional neural network (CNN). The proposed model constitutes a potential building block for deeper architectures to allow using motion without resorting to an external algorithm, \eg for recognition in videos. We derive our network architecture from signal processing principles to provide desired invariances to image contrast, phase and texture. We constrain weights within the network to enforce strict rotation invariance and substantially reduce the number of parameters to learn. We demonstrate end-to-end training on only 8 sequences of the Middlebury dataset, orders of magnitude less than competing CNN-based motion estimation methods, and obtain comparable performance to classical methods on the Middlebury benchmark. Importantly, our method outputs a distributed representation of motion that allows representing multiple, transparent motions, and dynamic textures. Our contributions on network design and rotation invariance offer insights nonspecific to motion estimation

Impurity relaxation mechanism for dynamic magnetization reversal in a single domain grain

The interaction of coherent magnetization rotation with a system of two-level impurities is studied. Two different, but not contradictory mechanisms, the `slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system of integro-differential equations for the magnetization. In the case that the impurity relaxation rate is much greater than the magnetization precession frequency, these equations can be written in the form of the Landau-Lifshitz equation with damping. Thus the damping parameter can be directly calculated from these microscopic impurity relaxation processes

Topological Excitations of One-Dimensional Correlated Electron Systems

Properties of low-energy excitations in one-dimensional superconductors and density-wave systems are examined by the bosonization technique. In addition to the usual spin and charge quantum numbers, a new, independently measurable attribute is introduced to describe elementary, low-energy excitations. It can be defined as a number w which determines, in multiple of $\pi$, how many times the phase of the order parameter winds as an excitation is transposed from far left to far right. The winding number is zero for electrons and holes with conventional quantum numbers, but it acquires a nontrivial value w=1 for neutral spin-1/2 excitations and for spinless excitations with a unit electron charge. It may even be irrational, if the charge is irrational. Thus, these excitations are topological, and they can be viewed as composite particles made of spin or charge degrees of freedom and dressed by kinks in the order parameter.Comment: 5 pages. And we are not only splitting point

Raman Scattering and Anomalous Current Algebra: Observation of Chiral Bound State in Mott Insulators

Recent experiments on inelastic light scattering in a number of insulating cuprates [1] revealed a new excitation appearing in the case of crossed polarizations just below the optical absorption threshold. This observation suggests that there exists a local exciton-like state with an odd parity with respect to a spatial reflection. We present the theory of high energy large shift Raman scattering in Mott insulators and interpret the experiment [1] as an evidence of a chiral bound state of a hole and a doubly occupied site with a topological magnetic excitation. A formation of these composites is a crucial feature of various topological mechanisms of superconductivity. We show that inelastic light scattering provides an instrument for direct measurements of a local chirality and anomalous terms in the electronic current algebra.Comment: 18 pages, TeX, C Version 3.

Topological Mechanism of Superconductivity

We outline the basic ideas of the topological mechanisms of superconductivity. A gauged model of correlated electronic system where a topological fluid is formed as a result of a strong interaction is discussed.Comment: 38 pages, latex, no figure

Response of deep-sea benthic foraminifera to a simulated sedimentation event

The response of deep-sea benthic foraminifera to a simulated sedimentation event was assessed in a shipboard microcosm by using transmission electron microscopy, organic carbon, adenosine nucleotide, ETS assays and live observations. A rapid activation of foraminiferal metabolism was detected with an increase in ETS activity and a distinct decrease in AMP to build up A TP. Based on this phy iological-awakening reaction, food was gathered by pseudopodia] activity and ingested in high quantities. Three days after feeding, high quality food was found in the digestion vacuoles leading to an increase of 89% in individual organic carbon contents. During the following six days, this food was converted into biomass as lipids and other reserve compounds were built up. After ten days, digestion vacuoles contained degraded matter onJy. The final shift in individual biomass was 16.9% in comparison to the initial population

Ground state properties of ferromagnetic metal/conjugated polymer interfaces

We theoretically investigate the ground state properties of ferromagnetic metal/conjugated polymer interfaces. The work is partially motivated by recent experiments in which injection of spin polarized electrons from ferromagnetic contacts into thin films of conjugated polymers was reported. We use a one-dimensional nondegenerate Su-Schrieffer-Heeger (SSH) Hamiltonian to describe the conjugated polymer and one-dimensional tight-binding models to describe the ferromagnetic metal. We consider both a model for a conventional ferromagnetic metal, in which there are no explicit structural degrees of freedom, and a model for a half-metallic ferromagnetic colossal magnetoresistance (CMR) oxide which has explicit structural degrees of freedom. The Fermi energy of the magnetic metallic contact is adjusted to control the degree of electron transfer into the polymer. We investigate electron charge and spin transfer from the ferromagnetic metal to the organic polymer, and structural relaxation near the interface. Bipolarons are the lowest energy charge state in the bulk polymer for the nondegenerate SSH model Hamiltonian. As a result electrons (or holes) transferred into the bulk of the polymer form spinless bipolarons. However, there can be spin density in the polymer localized near the interface.Comment: 7 figure