The KdV in Cosmology: a useful tool or a distraction?

The letter is a response to the recent article by J. Lidsey. We demonstrate that the Schwarzian derivative technique developed therein is but a consequence of linearizabiliy of the original cosmological equations. Furthermore, we show the required linearized equation to be nothing else but a Schr\"odinger equation.Comment: 6 pages. Acknowledgment is adde

Magnetoresistance in organic spintronic devices: the role of nonlinear effects

We derive kinetic equations describing injection and transport of spin polarized carriers in organic semiconductors with hopping conductivity via an impurity level. The model predicts a strongly voltage dependent magnetoresistance, defined as resistance variation between devices with parallel and antiparallel electrode magnetizations (spin valve effect). The voltage dependence of the magnetoresistance splits into three distinct regimes. The first regime matches well known inorganic spintronic regimes, corresponding to barrier controlled spin injection or the well known conductivity mismatch case. The second regime at intermediate voltages corresponds to strongly suppressed magnetoresistance. The third regime develops at higher voltages and accounts for a novel paradigm. It is promoted by the strong non-linearity in the charge transport which strength is characterized by the dimensionless parameter $eU/k_BT$. This nonlinearity, depending on device conditions, can lead to both significant enhancement or to exponential suppression of the spin valve effect in organic devices. We believe that these predictions are valid beyond the case of organic semiconductors and should be considered for any material characterized by strongly non-linear charge transport.Comment: 7 pages, 5 figure

Radiative decays of basic scalar, vector and tensor mesons and the determination of the P-wave q\bar q multiplet

We perform simultaneous calculations of the radiative decays of scalar mesons f_0(980)-> \gamma\gamma, a_0(980)-> \gamma\gamma, vector meson \phi(1020)-> \gamma f_0(980), \gamma a_0(980), \gamma \pi^0, \gamma \eta, \gamma \eta' and tensor mesons a_2(1320)-> \gamma\gamma, f_2(1270)-> \gamma\gamma, f_2(1525)-> \gamma\gamma assuming all these states to be dominantly the q\bar q ones. A good description of the considered radiative decays is reached by using almost the same radial wave functions for scalar and tensor mesons that supports the idea for the f_0(980), a_0(980) and a_2(1320), f_2(1270), f_2(1525) to belong to the same P -wave q\bar q multiplet.Comment: 28 pages, LaTeX, 9 PostScript figures, epsfig.st

Observation of the Little-Parks Oscillations in a System of Asymmetric Superconducting Rings

Little-Parks oscillations are observed in a system of 110 series-connected aluminum rings 2000 nm in diameter with the use of measuring currents from 10 nA to 1000 nA. The measurements show that the amplitude and character of the oscillations are independent of the relation between the measuring current and the amplitude of the persistent current. By using asymmetric rings, it is demonstrated that the persistent current has clockwise or contra-clockwise direction. This means that the total current in one of the semi-rings may be directed against the electric field at measurement of the Little-Parks oscillations. The measurements at zero and low measuring current have revealed that the persistent current, like the conventional circulating current, causes a potential difference on the semi-rings with different cross sections in spite of the absence of the Faraday's voltage.Comment: 5 pages, 6 figure

Birational automorphisms of a three-dimensional double quadric with an elementary singularity

It is proved that the group of birational automorphisms of a three-dimensional double quadric with a singular point arising from a double point on the branch divisor is a semidirect product of the free group generated by birational involutions of a special form and the group of regular automorphisms. The proof is based on the method of `untwisting' maximal singularities of linear systems.Comment: 18 page

Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin--momentum operator expansion method

Partial wave scattering amplitudes in baryon-baryon and baryon-antibaryon collisions and amplitudes for the production and decay of baryon resonances are constructed in the framework of the spin-momentum operator expansion method. The approach is relativistically invariant and it allows us to perform combined analyses of different reactions imposing analyticity and unitarity directly. The role of final state interactions (triangle and box diagrams) is discussed.Comment: 23 pages, 10 figure