Optimizing shortcut Brownian heat engine

Shortcut to isothermality provides a powerful method to realize quasistatic thermodynamic processes with finite-time manipulation. We implement the shortcut strategy to design and optimize Brownian heat engines, and formulate a rigorous geometric description of the energetics with the thermodynamic length. Along a given closed path in the control parameter space, the optimal control protocol is to manipulate the control parameters with a proper constant velocity to maximize the output power. We also propose the principle to find out the closed path with large maximum power. Our results generalize the previous optimization in the highly underdamped and the overdamped regimes to the general-damped situation, and are applicable for arbitrary finite-time cycles.Comment: 14 pages, 4 figure

Dark information of black hole radiation raised by dark energy

The "lost" information of black hole through the Hawking radiation was discovered being stored in the correlation among the non-thermally radiated particles [Phys. Rev. Lett 85, 5042 (2000), Phys. Lett. B 675, 1 (2009)]. This correlation information, which has not yet been proved locally observable in principle, is named by dark information. In this paper, we systematically study the influences of dark energy on black hole radiation, especially on the dark information. Calculating the radiation spectrum in the existence of dark energy by the approach of canonical typicality, which is reconfirmed by the quantum tunneling method, we find that the dark energy will effectively lower the Hawking temperature, and thus makes the black hole has longer life time. It is also discovered that the non-thermal effect of the black hole radiation is enhanced by dark energy so that the dark information of the radiation is increased. Our observation shows that, besides the mechanical effect (e.g., gravitational lensing effect), the dark energy rises the the stored dark information, which could be probed by a non-local coincidence measurement similar to the coincidence counting of the Hanbury-Brown -Twiss experiment in quantum optics.Comment: 21 pages, 3 figures, complete journal-info of Ref.[4] is added, comments are welcome ([email protected]

Optimal control theory for maximum power of Brownian heat engines

The pursuit of achieving the maximum power in microscopic thermal engines has gained increasing attention in recent studies of stochastic thermodynamics. We employ the optimal control theory to study the performance of Brownian heat engines and determine the optimal heat-engine cycles in generic damped situation, which were previously known only in the overdamped and the underdamped limits. These optimal cycles include two isothermal processes, two adiabatic processes, and an extra isochoric relaxation process at the upper stiffness constraint. Our results not only interpolate the optimal cycles between the overdamped and the underdamped limits, but also determine the appropriate friction coefficient of the Brownian heat engine to achieve the maximum power. These findings offer valuable insights for the development of high-performance Brownian heat engines in experimental setups.Comment: 6+16 pages, 3+4 figure

Giant mesoscopic spin Hall effect on surface of topological insulator

We study mesoscopic spin Hall effect on the surface of topological insulator with a step-function potential. The giant spin polarization induced by a transverse electric current is derived analytically by using McMillan method in the ballistic transport limit, which oscillates across the potential boundary with no confinement from the potential barrier due to the Klein paradox, and should be observable in spin resolved scanning tunneling microscope.Comment: 5 pages, 3 figure

The first Chinese student space shuttle getaway special program

The first Chinese Getaway Special program is described. Program organization, the student proposal evaluation procedure, and the objectives of some of the finalist's experiments are covered. The two experiments selected for eventual flight on the space shuttle are described in detail. These include: (1) the control of debris in the cabin of the space shuttle; and (2) the solidification of two immiscible liquids in space