Mycosphaerella podagrariae - a necrotrophic phytopathogen forming a special cellular interaction with its host Aegopodium podagraria

We present a new kind of cellular interaction found between Mycosphaerella podagrariae and Aegopodium podagraria, which is remarkably different to the interaction type of the obligate biotrophic fungus Cymadothea trifolii, another member of the Mycosphaerellaceae (Capnodiales, Dothideomycetes, Ascomycota) which we have described earlier. Observations are based on both conventional and cryofixed material and show that some features of this particular interaction are better discernable after chemical fixation. We were also able to generate sequences for nuclear ribosomal DNA (complete SSU, 5.8 S and flanking ITS-regions, D1–D3 region of the LSU) confirming the position of M. podagrariae within Mycosphaerellacea

Cymadothea trifolii, an obligate biotrophic leaf parasite of Trifolium, belongs to Mycosphaerellaceae as shown by nuclear ribosomal DNA analyses

The ascomycete Cymadothea trifolii, a member of the Dothideomycetes, is unique among obligate biotrophic fungi in its capability to only partially degrade the host cell wall and in forming an astonishingly intricate interaction apparatus (IA) in its own hyphae, while the attacked host plant cell is triggered to produce a membranous bubble opposite the IA. However, no sequence data are currently available for this species. Based on molecular phylogenetic results obtained from complete SSU and partial LSU data, we show that the genus Cymadothea belongs to the Mycosphaerellaceae (Capnodiales, Dothideomycetes). This is the first report of sequences obtained for an obligate biotrophic member of Mycosphaerellaceae

Pattern recognition on a quantum computer

By means of a simple example it is demonstrated that the task of finding and identifying certain patterns in an otherwise (macroscopically) unstructured picture (data set) can be accomplished efficiently by a quantum computer. Employing the powerful tool of the quantum Fourier transform the proposed quantum algorithm exhibits an exponential speed-up in comparison with its classical counterpart. The digital representation also results in a significantly higher accuracy than the method of optical filtering. PACS: 03.67.Lx, 03.67.-a, 42.30.Sy, 89.70.+c.Comment: 6 pages RevTeX, 1 figure, several correction

Ground State Energy of the One-Dimensional Discrete Random Schr\"{o}dinger Operator with Bernoulli Potential

In this paper, we show the that the ground state energy of the one dimensional Discrete Random Schroedinger Operator with Bernoulli Potential is controlled asymptotically as the system size N goes to infinity by the random variable \ell_N, the length the longest consecutive sequence of sites on the lattice with potential equal to zero. Specifically, we will show that for almost every realization of the potential the ground state energy behaves asymptotically as $\frac{\pi^2}{\ell_N+1)^2}$ in the sense that the ratio of the quantities goes to one

Effect of inelastic scattering on parametric pumping

Pumping of charge in phase-coherent mesoscopic systems due to the out-of-phase modulation of two parameters has recently found considerable interest. We investigate the effect of inelastic processes on the adiabatically pumped current through a two terminal mesoscopic sample. We find that the loss of coherence does not suppress the pumped charge but rather an additional physical mechanism for an incoherent pump effect comes into play. In a fully phase incoherent system the pump effect is similar to a rectification effect

Singularities in the Fermi liquid description of a partially filled Landau level and the energy gaps of fractional quantum Hall states

We consider a two dimensional electron system in an external magnetic field at and near an even denominator Landau level filling fraction. Using a fermionic Chern--Simons approach we study the description of the system's low energy excitations within an extension of Landau's Fermi liquid theory. We calculate perturbatively the effective mass and the quasi--particle interaction function characterizing this description. We find that at an even denominator filling fraction the fermion's effective mass diverges logarithmically at the Fermi level, and argue that this divergence allows for an {\it exact} calculation of the energy gaps of the fractional quantized Hall states asymptotically approaching these filling fractions. We find that the quasi--particle interaction function approaches a delta function. This singular behavior leads to a cancelation of the diverging effective mass from the long wavelength low frequency linear response functions at even denominator filling fractions.Comment: 46 pages, RevTeX, 5 figures included in a uuencoded postscript file. Minor revisions relative to the original version. The paper will be published in the Physical Review B, and can be retrieved from the World Wide Web, in http://cmtw.harvard.edu/~ster

Adiabatic spin pumping through a quantum dot with a single orbital level

We investigate an adiabatic spin pumping through a quantum dot with a single orbital energy level under the Zeeman effect. Electron pumping is produced by two periodic time dependent parameters, a magnetic field and a difference of the dot-lead coupling between the left and right barriers of the dot. The maximum charge transfer per cycle is found to be $e$, the unit charge in the absence of a localized moment in the dot. Pumped charge and spin are different, and spin pumping is possible without charge pumping in a certain situation. They are tunable by changing the minimum and maximum value of the magnetic field.Comment: RevTeX4, 5 pages, 3 figure

The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling

We investigate the effect that Rashba spin-orbit coupling has on the low energy behaviour of a two dimensional magnetic impurity system. It is shown that the Kondo effect, the screening of the magnetic impurity at temperatures T < T_K, is robust against such spin-orbit coupling, despite the fact that the spin of the conduction electrons is no longer a conserved quantity. A proposal is made for how the spin-orbit coupling may change the value of the Kondo temperature T_K in such systems and the prospects of measuring this change are discussed. We conclude that many of the assumptions made in our analysis invalidate our results as applied to recent experiments in semi-conductor quantum dots but may apply to measurements made with magnetic atoms placed on metallic surfaces.Comment: 22 pages, 1 figure; reference update

Holes in the t-J_z model: a thorough study

The t-J_z model is the strongly anisotropic limit of the t-J model which captures some general properties of the doped antiferromagnets (AF). The absence of spin fluctuations simplifies the analytical treatment of hole motion in an AF background and allows us to calculate the single- and two-hole spectra with high accuracy using regular diagram technique combined with real-space approach. At the same time, numerical studies of this model via exact diagonalization (ED) on small clusters show negligible finite size effects for a number of quantities, thus allowing a direct comparison between analytical and numerical results. Both approaches demonstrate that the holes have tendency to pair in the p- and d-wave channels at realistic values of t/J. The interactions leading to pairing and effects selecting p and d waves are thoroughly investigated. The role of transverse spin fluctuations is considered using perturbation theory. Based on the results of the present study, we discuss the pairing problem in the realistic t-J-like model. Possible implications for preformed pairs formation and phase separation are drawn.Comment: 21 pages, 15 figure

Interaction-free generation of entanglement

In this paper, we study how to generate entanglement by interaction-free measurement. Using Kwiat et al.'s interferometer, we construct a two-qubit quantum gate that changes a particle's trajectory according to the other particle's trajectory. We propose methods for generating the Bell state from an electron and a positron and from a pair of photons by this gate. We also show that using this gate, we can carry out the Bell measurement with the probability of 3/4 at the maximum and execute a controlled-NOT operation by the method proposed by Gottesman and Chuang with the probability of 9/16 at the maximum. We estimate the success probability for generating the Bell state by our procedure under imperfect interaction.Comment: 18 pages, Latex2e, 11 eps figures, v2: minor corrections and one reference added, v3: a minor correctio