32,745 research outputs found
The Lagrangian cobordism group of
We compute the Lagrangian cobordism group of the standard symplectic 2-torus
and prove that it is isomorphic to the Grothendieck group of its derived Fukaya
category. The proofs use homological mirror symmetry for the 2-torus.Comment: 43 pages, 12 figures. V2: Result of computation of the cobordism
group reformulated; further minor changes and corrections. V3: Updated such
as to agree with accepted version. To appear in Selecta Mathematic
Light-emitting current of electrically driven single-photon sources
The time-dependent tunnelling current arising from the electron-hole
recombination of exciton state is theoretically studied using the
nonequilibrium Green's function technique and the Anderson model with two
energy levels. The charge conservation and gauge invariance are satisfied in
the tunnelling current. Apart from the classical capacitive charging and
discharging behavior, interesting oscillations superimpose on the tunnelling
current for the applied rectangular pulse voltage.Comment: 14 pages, 5 figure
Quasi maximum likelihood estimation and prediction in the compound Poisson ECOGARCH(1,1) model
This paper deals with the problem of estimation and prediction in a compound Poisson ECOGARCH(1,1) model. For this we construct a quasi maximum likelihood estimator under the assumption that all jumps of the log-price process are observable. Since these jumps occur at unequally spaced time points, it is clear that the estimator has to be computed for irregularly spaced data. Assuming normally distributed jumps and a recursion to estimate the volatility allows to define and compute a quasi-likelihood function, which is maximised numerically. The small sample behaviour of the estimator is analysed in a small simulation study. Based on the recursion for the volatility process a one-step ahead prediction of the volatility is defined as well as a prediction interval for the log-price process. Finally the model is fitted to tick-by-tick data of the New York Stock Exchange
Mixed effect model for absolute log returns of ultra high frequency data
The influence of covariates on absolute log returns of ultra high frequency data is analysed. Therefore we construct a mixed effect model for the absolute log returns. The parameters are estimated in a state space approach. To analyse the correlation in these irregularly spaced data empirically, the variogram, known mainly from spatial statistics, will be used. In a small simulation study the performance of the estimators will be analysed. In the end we apply the model to IBM trade data and analyse the influence of the covariates
Modulation of the dephasing time for a magnetoplasma in a quantum well
We investigate the femtosecond kinetics of optically excited 2D
magneto-plasma. We calculate the femtosecond dephasing and relaxation kinetics
of the laser pulse excited magneto-plasma due to bare Coulomb potential
scattering, because screening is under these conditions of minor importance. By
taking into account four Landau subbands in both the conduction band and the
valence band, we are now able to extend our earlier study [Phys. Rev. B {\bf
58}, 1998,in print (see also cond-mat/9808073] to lower magnetic fields. We can
also fix the magnetic field and change the detuning to further investigate the
carrier density-dependence of the dephasing time. For both cases, we predict
strong modulation in the dephasing time.Comment: RevTex, 3 figures, to be published in Solid. Stat. Commu
Triplet Production by Linearly Polarized Photons
The process of electron-positron pair production by linearly polarized
photons is used as a polarimeter to perform mobile measurement of linear photon
polarization. In the limit of high photon energies, omega, the distributions of
the recoil-electron momentum and azimuthal angle do not depend on the photon
energy in the laboratory frame. We calculate the power corrections of order
m/omega to the above distributions and estimate the deviation from the
asymptotic result for various values of omega.Comment: LaTeX2e, 13 pages, 5 figure files (eps), submitted to Phys. Rev.
Naturalistic Metaphysics at Sea
In this paper I return to the mid-20th-century debate between Quine and Carnap on the status of metaphysics questions with an eye toward advancing contemporary debates about whether naturalists can coherently undertake substantive metaphysical inquiry. Following Huw Price, I take the debate between Quine and Carnap to hinge, in part, on whether human inquiry is functionally unified. However, unlike Price, I suggest that this question is not best understood as a question about the function(s) of descriptive discourse. This goes along with rejecting a “linguistic conception” of the starting point of metaphysical inquiry, which, although shared by Quine and Carnap, Price gives us no good reason to think is mandatory for naturalists. I sketch two reasons naturalists have to reject a particular manifestation of this linguistic conception in Quine’s work—his criterion of ontological commitment. Finally, I show how these reasons can help us identify the grains of truth in some recent critiques of “mainstream metaphysics of mind.
Field testing of strategies for fire blight control in organic fruit growing
In organic fruit growing effective control strategies are needed to prevent blossom infections by the fire blight pathogen Erwinia amylovora. Many potential control agents are under discussion and have been tested in vitro and in vivo. 19 out of 27 tested preparations showed a high efficacy against E. amylovora in vitro. Nevertheless, on detached apple blossoms only 7 of them led to a symptom reduction by more than 50%. In six field trials conducted according to the EPPO guideline PP1/166(3) BlossomProtect (82%), Myco-sin (65%) and Funguran (58%) had the highest efficiency. In 2006 and 2007, strategies to integrate BlossomProtect in spray schedules of organic apple production have been tested. The use of sulphur or lime-sulphur before or after BlossomProtect did not influence the efficiency of BlossomProtect, which showed that fire blight control is possible without compromising apple scab control. The addition of Cutisan to BlossomProtect reduced fruit russet. An alternating use of BlossomProtect and Myco-sin was shown to be possible
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