Logarithmic temperature dependence of conductivity at half-integer filling factors: Evidence for interaction between composite fermions

We have studied the temperature dependence of diagonal conductivity in high-mobility two-dimensional samples at filling factors $\nu=1/2$ and 3/2 at low temperatures. We observe a logarithmic dependence on temperature, from our lowest temperature of 13 mK up to 400 mK. We attribute the logarithmic correction to the effects of interaction between composite fermions, analogous to the Altshuler-Aronov type correction for electrons at zero magnetic field. The paper is accepted for publication in Physical Review B, Rapid Communications.Comment: uses revtex macro

The Causal Phase in QED3QED_{3}

The operator ${\bf S}$ in Fock space which describes the scattering and particle production processes in an external time-dependent electromagnetic potential $A$ can be constructed from the one-particle S-matrix up to a physical phase $\lambda [A]$. In this work we determine this phase for $QED$ in (2+1) dimensions, by means of causality, and show that no ultraviolet divergences arise, in contrast to the usual formalism of $QED$.Comment: LaTex, 11 pages, no figure

Trapping of transuranium elements by the earth's magnetic field

The search for a transuranium element component of cosmic radiation has been carried out in high altitude balloon experiments. The trapping of high Z elements on orbits in the Earth's magnetic field may lead to a sufficient enhancement of the intensity of particle flux to make it possible to detect these elements by satellite experiments. Calculations are presented that predict the behavior of trapped particles as a function of the predicted flux and energy distribution of high Z elements incident on the Earth's magnetic field. Techniques are suggested for the detection of such particles. In addition, the possibility of production of transuranium elements in the recently discovered pulsars are discussed

Rugged pressed disk electrode has low contact potential

Pressed-disk electrode with low contact potential monitors physiological processes. It consists of silver and silver chloride combined with bentonitic clay. The clay affords a surface that permits use over extended periods without contact deterioration

Pentaquark decay is suppressed by chirality conservation

It is shown, that if the pentaquark $\Theta^+ = uudd\bar{s}$ baryon can be represented by the local quark current $\eta_{\Theta}$, its decay $\Theta^+ \to n K^+ (p K^0)$ is forbidden in the limit of chirality conservation. The $\Theta^+$decay width $\Gamma$ is proportional to $\alpha^2_s < 0 | \bar{q} q | 0 >^2$, where $$, $q = u,d,s$ is quark condensate, and, therefore, is strongly suppressed. Also the polarization operator of the pentaquark current with isospin 1 is calculated using the operator product expansion and estimation for it mass is obtained .Comment: 4 pages, 1 fig, typos correcte