Luttinger-liquid-like transport in long InSb nanowires

Long nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter is around 50 \AA, length 0.1 - 1 mm) were prepared. Electrical conduction of these nanowires is studied over a temperature range 1.5 - 350 K. It is found that a zero-field electrical conduction is a power function of the temperature $G\propto T^\alpha$ with the typical exponent $\alpha \approx 4$. Current-voltage characteristics of such nanowires are found to be nonlinear and at sufficiently low temperatures follows the power law $I\propto V^\beta$. It is shown that the electrical conduction of these nanowires cannot be accounted for in terms of ordinary single-electron theories and exhibits features expected for impure Luttinger liquid. For a simple approximation of impure LL as a pure one broken into drops by weak links, the estimated weak-link density is around $10^3-10^4$ per cm.Comment: 5 pages, 2 figure

Holomorphic symplectic geometry: a problem list

A list of open problems on holomorphic symplectic, contact and Poisson manifolds

Endomorphisms of abelian varieties, cyclotomic extensions and Lie algebras

We prove an analogue of the Tate conjecture on homomorphisms of abelian varieties over infinite cyclotomic extensions of finitely generated fields of characteristic zero.Comment: 9 page

Diffusion and Transport Coefficients in Synthetic Opals

Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the termal and electrical conductivity makes possible to estimate the transport coefficients of opal structures. We estimate this changes as function of the neck size and the mean-free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures.Comment: Submitted to PR

Metallic Xenon, Molecular Condensates, and Superconductivity

A possibility of explaining the light absorption observed to occur under pressure-induced xenon metallization as due to the transition to the superconducting state is analyzed. The mechanism of the van der Waals bonding is discussed.Comment: LaTeX 2.09 (RevTeX), 4 pages, 4 PostScript figures included in tex

Оптимальна фільтрація радіосигналів малої тривалості в частотно-часовому методі вимірювань несучої частоти

The possibility of optimal filteringradio signals of short duration in time-frequency method for measuring the carrier frequency.Displaying and concluded that the optimal filtering is possible only for constant radio optimumduration of which are confirmed by experimental research method. It is shown that inexcess of the duration of the response signal into a signal DLZ Fresnel since the frequencyspectrum of the input signal becomes less than optimal and leads to repeated DLZ samplefrequency of the signal spectrum. Moreover, the number of samples corresponds to the numberof samples for the duration of the radio frequencyРассмотрена возможность осуществления оптимальной фильтрации радиосигналов малой длительности в частотно-временном методе измерения несущих частот.Показано и сделан вывод о том, что оптимальная фильтрация возможна только длярадиосигналов постоянной оптимальной длительности, которые подтверждаютсяэкспериментальными исследованиями метода. Показано, что при превышении длительности радиосигнала отклик ДЛЗ превращается в сигнал Френеля поскольку частотный спектр входного радиосигнала становиться меньше оптимального и приводит в ДЛЗ к неоднократной выборке частоты из сигнала спектра. При этом числотаких выборок соответствует числу выборок частот за длительность радиосигнала.Розглянуто можливість здійснення оптимальної фільтрації радіосигналів малої тривалості в частотно-часовому методі вимірювання несучих частот. Показано і зроблений висновок про те, що оптимальна фільтрація можлива тільки для радіосигналів постійної оптимальної тривалості, які підтверджуються експериментальними дослідженнями методу. Показано, що при перевищенні тривалості радіосигналу відгук ДЛЗ перетворюється в сигнал Френеля оскільки частотний спектр вхідного сигналу ставати менше оптимального і приводить в ДЛЗ до неодноразової вибірці частоти з сигналу спектру. При цьому число таких вибірок відповідає числу вибірок частот за тривалість радіосигнал

Effect of pressure on the polarized infrared optical response of quasi-one-dimensional LaTiO3.41_{3.41}

The pressure-induced changes in the optical properties of the quasi-one-dimensional conductor LaTiO$_{3.41}$ were studied by polarization-dependent mid-infrared micro-spectroscopy at room temperature. For the polarization of the incident radiation parallel to the conducting direction, the optical conductivity spectrum shows a pronounced mid-infrared absorption band, exhibiting a shift to lower frequencies and an increase in oscillator strength with increasing pressure. On the basis of its pressure dependence, interpretations of the band in terms of electronic transitions and polaronic excitations are discussed. Discontinuous changes in the optical response near 15 GPa are in agreement with a recently reported pressure-induced structural phase transition and indicate the onset of a dimensional crossover in this highly anisotropic system.Comment: 7 pages, 7 figure

Antimatter research in Space

Two of the most compelling issues facing astrophysics and cosmology today are to understand the nature of the dark matter that pervades the universe and to understand the apparent absence of cosmological antimatter. For both issues, sensitive measurements of cosmic-ray antiprotons and positrons, in a wide energy range, are crucial. Many different mechanisms can contribute to antiprotons and positrons production, ranging from conventional reactions up to exotic processes like neutralino annihilation. The open problems are so fundamental (i.e.: is the universe symmetric in matter and antimatter ?) that experiments in this field will probably be of the greatest interest in the next years. Here we will summarize the present situation, showing the different hypothesis and models and the experimental measurements needed to lead to a more established scenario.Comment: 10 pages, 7 figures, Invited talk at the 18th European Cosmic Ray Symposium, Moscow, July 2002, submitted to Journal of Physics

Log Fano varieties over function fields of curves

Consider a smooth log Fano variety over the function field of a curve. Suppose that the boundary has positive normal bundle. Choose an integral model over the curve. Then integral points are Zariski dense, after removing an explicit finite set of points on the base curve.Comment: 18 page

Rationality of the moduli spaces of plane curves of sufficiently large degree

We prove that the moduli space of plane curves of degree d is rational for all sufficiently large d.Comment: 18 pages; 1 figure; Macaulay2 scripts used can be found at http://www.uni-math.gwdg.de/bothmer/rationality/ or at the end of the latex source fil