Cosmic Friction: A Query

Effects of friction on cosmic strings.

We study the evolution of cosmic strings taking into account the frictional force due to the surrounding radiation. We consider small perturbations on straight strings, oscillation of circular loops and small perturbations on circular loops. For straight strings, friction exponentially suppresses perturbations whose co-moving scale crosses the horizon before cosmological time t∗ ∼ μ−2 (in Planc...

Time Delays in Cosmic Ray Propagation

Cosmic Rays (CR) travel at speeds essentially indistinguishable from the speed of light. However whilst travelling through magnetic fields, both regular and turbulent, they are delayed behind the light since they are usually charged particles and their paths are not linear. Those delays can be so long that they are an impediment to correctly identifying sources which may be variable in time. Fu...

Friction Models and Friction Compensation

Friction occurs in all mechanical systems,e.g. bearings, transmissions, hydraulic and pneumatic cylinders, valves, brakes and wheels. Friction appears at the physical interface between two surfaces in contact. Lubricants such as grease or oil are often used but the there may also be a dry contact between the surfaces. Friction is strongly influenced by contaminations. There is a wide range of p...

Eliminating friction with friction: 2D Janssen effect in a friction-driven system.

The Janssen effect is a unique property of confined granular materials experiencing gravitational compaction in which the pressure at the bottom saturates with an increasing filling height due to frictional interactions with side walls. In this Letter, we replace gravitational compaction with frictional compaction. We study friction-compacted 2D granular materials confined within fixed boundari...

A study of friction models and friction compensation