Effects of electron-electron scattering in wide ballistic microcontacts

We consider effects of electron-electron scattering in wide ballistic microcontacts. Using a semiclassical Boltzmann equation, we obtain a positive correction to the Sharvin conductance that results from electron-electron collisions in the leads. The correction is linearly dependent on temperature at high temperatures T⪢eV and proportional to |V| at high voltages eV⪢T. Magnetic field leads to strong suppression of this positive correction that results in a positive magnetoresistance in weak fields. As electron-electron scattering affects the conductance, it also influences the noise. At low voltages the noise is defined by the Nyquist relation and at high voltages it is related with the inelastic correction to the current by the Shottky formula δS=2eδI.