Strong, fast pulses, called ‘‘bang–bang’’ controls can be used to eliminate the effects of system-environment interactions. This method for preventing errors in quantum information processors is treated here in a geometric setting which leads to an intuitive perspective. Using this geometric description, we clarify the notion of group symmetrization as an averaging technique, provide a geometri...

In this paper we use an optimal control approach to analyze time dependent enzyme concentrations that minimize the transition time of a metabolic pathway while respecting the natural constraints imposed by a limited biosynthetical capacity. Our main result states that, under appropriate assumptions, at each time instant all the available enzyme production capacity is allocated to a single react...

A principal technical result of this paper is that the onedimensional heat equation with boundary control is exactly null-controllable with control restricted to an arbitrary set E ⊂ [0, T ] of positive measure. A general abstract argument is presented to show that this implies the ‘bangbang’ property for time-optimal controls — i.e., such a control can take only extreme values of (the hull of)...

In this article, we propose a new paradigm of control, called a maximum-hands-off control. A hands-off control is defined as a control that has a much shorter support than the horizon length. The maximum-hands-off control is the minimum-support (or sparsest) control among all admissible controls. We first prove that a solution to an L-optimal control problem gives a maximum-handsoff control, an...

A teoria do Big Bang corresponde ao modelo explicativo início Universo a partir de um ponto (singularidade) elevada densidade e temperatura que começa expandir- se, criando-se o espaço-tempo. Sendo seguido pelo período inflação cósmica, dominado pela radiação outro matéria (principalmente escura) até momento atual, por uma energia escura, permite explicar história nosso observável. O é bem test...

Major characteristics Many autistic infants are different from birth. Two common characteristics they may exhibit include arching their back away from their caregiver to avoid physical contact and failing to anticipate being picked up (i.e., becoming limp). As infants, they are often described as either passive or overly agitated babies. A passive baby refers to one who is quiet most of the tim...

For a long time, there were two main theories related to how our universe would end. These were the Big Freeze and the Big Crunch. In short, the Big Crunch claimed that the universe would eventually stop expanding and collapse in on itself. This collapse would result in...well...a big crunch (for lack of a better term). Think “the Big Bang”, except just the opposite. That’s essentially what the...

The minimal grand uni ed supergravity model is discussed. Requiring radiative breaking of the electroweak gauge symmetry, the uni cation of b and Yukawa couplings, a su ciently stable nucleon, and not too large a relic density of neutralinos produced in the Big Bang constrains the parameter space signi cantly. In particular, the soft breaking parameter m1=2 has to be less than about 130 GeV, an...