GEOLOGY: Very Slow Growth

Eigentimes and Very Slow Processes

We investigate the importance of the time and length scales at play in our descriptions of Nature. What can we observe at the atomic scale, at the laboratory (human) scale, and at the galactic scale? Which variables make sense? For every scale we wish to understand we need a set of variables which are linked through closed equations, i.e., everything can meaningfully be described in terms of th...

Growth-inhibiting conditions slow growth plate senescence.

The mammalian growth plate undergoes programmed senescence during juvenile life, causing skeletal growth to slow with age. We previously found that hypothyroidism in rats slowed both growth plate chondrocyte proliferation and growth plate senescence, suggesting that senescence is not dependent on age per se but rather on chondrocyte proliferation. However, one alternative explanation is that th...

Does slow growth increase inequality?

Slow decorrelations in KPZ growth

For stochastic growth models in the Kardar-Parisi-Zhang (KPZ) class in 1 + 1 dimensions, fluctuations grow as t1/3 during time t and the correlation length at a fixed time scales as t2/3. In this note we discuss the scale of time correlations. It turns out that the spacetime is non-trivially fibred, having slow directions with decorrelation exponent equal to 1 instead of the usual 2/3. These di...

Source Seeking With Very Slow or Drifting Sensors

Slow sensors arise in many applications, including sensing chemical concentrations in tracking of contaminant plumes. Slow sensors are often the cause of poor performance and a potential cause of instability. In this paper, we design a modified extremum seeking scheme to account and exploit slow sensor dynamics. We also consider the worst case, which is sensor dynamics governed by a pure integr...