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

Concentration-dependent mobility in organic field-effect transistors probed by infrared spectromicroscopy of the charge density profile

We show that infrared imaging of the charge density profile in organic field-effect transistors (FETs) can probe transport characteristics which are difficult to access by conventional contact-based measurements. Specifically, we carry out experiments and modeling of infrared spectromicroscopy of poly(3-hexylthiophene) (P3HT) FETs in which charge injection is affected by a relatively low resistance of the gate insulators. We conclude that the mobility of P3HT has a power-law density dependence, which is consistent with the activated transport in disorder-induced tails of the density of states.Comment: 3+ pages, 2 figure

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

Knight Shift Anomalies in Heavy Electron Materials

We calculate non-linear Knight Shift $K$ vs. susceptibility $\chi$ anomalies for Ce ions possessing local moments in metals. The ions are modeled with the Anderson Hamiltonian and studied within the non-crossing approximation (NCA). The $K-vs.- \chi$ non-linearity diminishes with decreasing Kondo temperature $T_0$ and nuclear spin- local moment separation. Treating the Ce ions as an incoherent array in CeSn$_3$, we find excellent agreement with the observed Sn $K(T)$ data.Comment: 4 pages, Revtex, 3 figures available upon request from [email protected]

Exact Thermodynamics of the Double sinh-Gordon Theory in 1+1-Dimensions

We study the classical thermodynamics of a 1+1-dimensional double-well sinh-Gordon theory. Remarkably, the Schrodinger-like equation resulting from the transfer integral method is quasi-exactly solvable at several temperatures. This allows exact calculation of the partition function and some correlation functions above and below the short-range order (``kink'') transition, in striking agreement with high resolution Langevin simulations. Interesting connections with the Landau-Ginzburg and double sine-Gordon models are also established.Comment: 4 pages, 3 figures (embedded using epsf), uses RevTeX plus macro (included). Minor revision to match journal version, Phys. Rev. Lett. (in press

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

Infrared conductivity of hole accumulation and depletion layers in (Ga,Mn)As- and (Ga,Be)As-based electric field-effect devices

We have fabricated electric double-layer field-effect devices to electrostatically dope our active materials, either $x$=0.015 Ga$_{1-x}$Mn$_x$As or $x$=3.2$\times10^{-4}$ Ga$_{1-x}$Be$_x$As. The devices are tailored for interrogation of electric field induced changes to the frequency dependent conductivity in the accumulation or depletions layers of the active material via infrared (IR) spectroscopy. The spectra of the (Ga,Be)As-based device reveal electric field induced changes to the IR conductivity consistent with an enhancement or reduction of the Drude response in the accumulation and depletion polarities, respectively. The spectroscopic features of this device are all indicative of metallic conduction within the GaAs host valence band (VB). For the (Ga,Mn)As-based device, the spectra show enhancement of the far-IR itinerant carrier response and broad mid-IR resonance upon hole accumulation, with a decrease of these features in the depletion polarity. These later spectral features demonstrate that conduction in ferromagnetic (FM) Ga$_{1-x}$Mn$_x$As is distinct from genuine metallic behavior due to extended states in the host VB. Furthermore, these data support the notion that a Mn-induced impurity band plays a vital role in the electron dynamics of FM Ga$_{1-x}$Mn$_x$As. We add, a sum-rule analysis of the spectra of our devices suggests that the Mn or Be doping does not lead to a substantial renormalization of the GaAs host VB

Distribution of spectral weight in a system with disordered stripes

The ``band-structure'' of a disordered stripe array is computed and compared, at a qualitative level, to angle resolved photoemission experiments on the cuprate high temperature superconductors. The low-energy states are found to be strongly localized transverse to the stripe direction, so the electron dynamics is strictly one-dimensional (along the stripe). Despite this, aspects of the two dimensional band-structure Fermi surface are still vividly apparent.Comment: 10 pages, 11 figure