Note on nonequilibrium stationary states and entropy

In transformations between nonequilibrium stationary states, entropy might be a not well defined concept. It might be analogous to the ``heat content'' in transformations in equilibrium which is not well defined either, if they are not isochoric ({\it i.e.} do involve mechanical work). Hence we conjecture that un a nonequilbrium stationary state the entropy is just a quantity that can be transferred or created, like heat in equilibrium, but has no physical meaning as ``entropy content'' as a property of the system.Comment: 4 page

Shear viscosity in magnetized neutron star crust

The electron shear viscosity due to Coulomb scattering of degenerate electrons by atomic nuclei throughout a magnetized neutron star crust is calculated. The theory is based on the shear viscosity coefficient calculated neglecting magnetic fields but taking into account gaseous, liquid and solid states of atomic nuclei, multiphonon scattering processes, and finite sizes of the nuclei albeit neglecting the effects of electron band structure. The effects of strong magnetic fields are included in the relaxation time approximation with the effective electron relaxation time taken from the field-free theory. The viscosity in a magnetized matter is described by five shear viscosity coefficients. They are calculated and their dependence on the magnetic field and other parameters of dense matter is analyzed. Possible applications and open problems are outlined.Comment: 6 pages, 3 figures, EPL, accepte

Network representation of electromagnetic fields and forces using generalized bond graphs

We show that it is possible to describe electromagnetic (E-M) fields with a generalized network representation (generalized bond graphs). E-M fields inmoving matter, forces due to E-M fields (Lorentz force, ets.) and field transformations are included in the network description. The relations of these E-M phenomena with respect to each other are clearly represented by the bond graph. We also show that it is not possible to describe E-M phenomena in moving matter with conventional bond graphs, but that a generalized bond graph concept is required.\ud \ud The description of simple E-M devices with conventional bond graphs is based on rather drastic assumptions, i.e. quasi-static conditions (E-M radiation neglected), homogeneous fields, isotropic linear material, etc. These assumptions are not made in this paper

Deep space FM system, a concept

Deep space frequency modulation system permits transmission of data where the signal deviation is greater than 1/2 the predetection bandwidth. It provides satisfactory performance at great distances or with low signal levels

Phase detector assembly Patent

Detector assembly for discriminating first signal with respect to presence or absence of second signal at time of occurrence of first signa

Nonlinear quantum optical computing via measurement

We show how the measurement induced model of quantum computation proposed by Raussendorf and Briegel [Phys. Rev. Letts. 86, 5188 (2001)] can be adapted to a nonlinear optical interaction. This optical implementation requires a Kerr nonlinearity, a single photon source, a single photon detector and fast feed forward. Although nondeterministic optical quantum information proposals such as that suggested by KLM [Nature 409, 46 (2001)] do not require a Kerr nonlinearity they do require complex reconfigurable optical networks. The proposal in this paper has the benefit of a single static optical layout with fixed device parameters, where the algorithm is defined by the final measurement procedure.Comment: 14 pages, 4 figures, 4 table

γ\gamma-ray spectra and enhancement factors for positron annihilation spectra with core-electrons

Many-body theory is developed to calculate the $\gamma$-spectra for positron annihilation with valence and core electrons in the noble gas atoms. A proper inclusion of correlation effects and core annihilation provides for an accurate description of the measured spectra [Iwata \textit{et al.}, Phys. Rev. Lett. {\bf 79}, 39 (1997)]. The theory enables us to calculate the enhancement factors $\gamma_{nl}$, which describe the effect of electron-positron correlations for annihilation on individual electron orbitals $nl$. We find that the enhancement factors scale with the orbital ionization energy $I_{nl}$ (in electron-volt), as $\gamma_{nl}=1+\sqrt{A/I_{nl}}+(B/I_{nl})^{\beta}$, where $A\approx 40$~eV, $B\approx 24$~eV and $\beta\approx 2.3$.Comment: 5 pages, 5 figure