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Quantum Hertz entropy increase in a quenched spin chain
The classical Hertz entropy is the logarithm of the volume of phase space
bounded by the constant energy surface; its quantum counterpart, the quantum
Hertz entropy, is , where the quantum operator specifies the number of states with energy below a given energy eigenstate.
It has been recently proved that, when an isolated quantum mechanical system is
driven out of equilibrium by an external driving, the change in the expectation
of its quantum Hertz entropy cannot be negative, and is null for adiabatic
driving. This is in full agreement with the Clausius principle. Here we test
the behavior of the expectation of the quantum Hertz entropy in the case when
two identical XY spin chains initially at different temperatures are quenched
into a single XY chain. We observed no quantum Hertz entropy decrease. This
finding further supports the statement that the quantum Hertz entropy is a
proper entropy for isolated quantum systems. We further quantify how far the
quenched chain is from thermal equilibrium and the temperature of the closest
equilibrium.Comment: 9 pages, 5 figure
A note on two notions of compliance
We establish a relation between two models of contracts: binary session
types, and a model based on event structures and game-theoretic notions. In
particular, we show that compliance in session types corresponds to the
existence of certain winning strategies in game-based contracts.Comment: In Proceedings ICE 2014, arXiv:1410.701
Symplectic geometry and Noether charges for Hopf algebra space-time symmetries
There has been a certain interest in some recent works in the derivation of
Noether charges for Hopf-algebra space-time symmetries. Such analyses relied
rather heavily on delicate manipulations of the fields of non-commuting
coordinates whose charges were under study. Here we derive the same charges in
a "coordinate-independent" symplectic-geometry type of approach and find
results that are consistent with the ones of hep-th/0607221.Comment: 12 pages, RevTex4; clarifying remarks added and incorrect statement
rectified; typos correcte
Aerodynamics of a rigid curved kite wing
A preliminary numerical study on the aerodynamics of a kite wing for high
altitude wind power generators is proposed. Tethered kites are a key element of
an innovative wind energy technology, which aims to capture energy from the
wind at higher altitudes than conventional wind towers. We present the results
obtained from three-dimensional finite volume numerical simulations of the
steady air flow past a three-dimensional curved rectangular kite wing (aspect
ratio equal to 3.2, Reynolds number equal to 3x10^6). Two angles of incidence
-- a standard incidence for the flight of a tethered airfoil (6{\deg}) and an
incidence close to the stall (18{\deg}) -- were considered. The simulations
were performed by solving the Reynolds Averaged Navier-Stokes flow model using
the industrial STAR-CCM+ code. The overall aerodynamic characteristics of the
kite wing were determined and compared to the aerodynamic characteristics of
the flat rectangular non twisted wing with an identical aspect ratio and
section (Clark Y profile). The boundary layer of both the curved and the flat
wings was considered to be turbulent throughout. It was observed that the
curvature induces only a mild deterioration of the aerodynamics properties.
Pressure distributions around different sections along the span are also
presented, together with isolines of the average pressure and kinetic energy
fields at a few sections across the wing and the wake. Our results indicate
that the curvature induces a slower spatial decay of the vorticity in the wake,
and in particular, inside the wing tip vortices.Comment: 13 pages, 13 figures. Submitted to "Renewable Energy
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