Ultra-nonlocality in density functional theory for photo-emission spectroscopy

We derive an exact expression for the photo-current of photo-emission spectroscopy using time-dependent current density functional theory (TDCDFT). This expression is given as an integral over the Kohn-Sham spectral function renormalized by effective potentials that depend on the exchange-correlation kernel of current density functional theory. We analyze in detail the physical content of this expression by making a connection between the density-functional expression and the diagrammatic expansion of the photo-current within many-body perturbation theory. We further demonstrate that the density functional expression does not provide us with information on the kinetic energy distribution of the photo-electrons. Such information can, in principle, be obtained from TDCDFT by exactly modeling the experiment in which the photo-current is split into energy contributions by means of an external electromagnetic field outside the sample, as is done in standard detectors. We find, however, that this procedure produces very nonlocal correlations between the exchange-correlation fields in the sample and the detector.Comment: 11 pages, 11 figure

Samenwerken aan integrale omgevingsvisies met water

In deze handreiking wordt (in navolging van de centrale doelen van de Omgevingswet) ingegaan op de leerervaringen in de bestudeerde pilots ten aanzien van de vier leerpijlers die centraal hebben gestaan, namelijk: participatie, integraliteit en samenhang, cultuurverandering en digitalisering. Daarbij wordt ook nadrukkelijk ingegaan op de rol die waterschappen hebben ingenomen in de pilots en mogelijk in kunnen nemen in toekomstige projecten

Global fixed point proof of time-dependent density-functional theory

We reformulate and generalize the uniqueness and existence proofs of time-dependent density-functional theory. The central idea is to restate the fundamental one-to-one correspondence between densities and potentials as a global fixed point question for potentials on a given time-interval. We show that the unique fixed point, i.e. the unique potential generating a given density, is reached as the limiting point of an iterative procedure. The one-to-one correspondence between densities and potentials is a straightforward result provided that the response function of the divergence of the internal forces is bounded. The existence, i.e. the v-representability of a density, can be proven as well provided that the operator norms of the response functions of the members of the iterative sequence of potentials have an upper bound. The densities under consideration have second time-derivatives that are required to satisfy a condition slightly weaker than being square-integrable. This approach avoids the usual restrictions of Taylor-expandability in time of the uniqueness theorem by Runge and Gross [Phys.Rev.Lett.52, 997 (1984)] and of the existence theorem by van Leeuwen [Phys.Rev.Lett. 82, 3863 (1999)]. Owing to its generality, the proof not only answers basic questions in density-functional theory but also has potential implications in other fields of physics.Comment: 4 pages, 1 figur

Nuclear collisions at the Future Circular Collider

The Future Circular Collider is a new proposed collider at CERN with centre-of-mass energies around 100 TeV in the pp mode. Ongoing studies aim at assessing its physics potential and technical feasibility. Here we focus on updates in physics opportunities accessible in pA and AA collisions not covered in previous Quark Matter contributions, including Quark-Gluon Plasma and gluon saturation studies, novel hard probes of QCD matter, and photon-induced collisions.Comment: 4 pages, 5 figures, proceedings of Quark Matter 201

Analysis of The Hipparcos Measurements of HD10697 - A Mass Determination of a Brown-Dwarf Secondary

HD10697 is a nearby main-sequence star around which a planet candidate has recently been discovered by means of radial-velocity measurements (Vogt et al. 1999, submitted to ApJ). The stellar orbit has a period of about three years, the secondary minimum mass is 6.35 Jupiter masses and the minimum semi-major axis is 0.36 milli-arc-sec (mas). Using the Hipparcos data of HD10697 together with the spectroscopic elements of Vogt et al. (1999) we found a semi-major axis of 2.1 +/- 0.7 mas, implying a mass of 38 +/- 13 Jupiter masses for the unseen companion. We therefore suggest that the secondary of HD10697 is probably a brown dwarf, orbiting around its parent star at a distance of 2 AU.Comment: 6 pages, 2 figures, LaTex, aastex, accepted for publication by ApJ Letter

Atom lithography without laser cooling

Using direct-write atom lithography, Fe nanolines are deposited with a pitch of 186 nm, a full width at half maximum (FWHM) of 50 nm, and a height of up to 6 nm. These values are achieved by relying on geometrical collimation of the atomic beam, thus without using laser collimation techniques. This opens the way for applying direct-write atom lithography to a wide variety of elements.Comment: 7 pages, 11 figure

A charged particle in a magnetic field - Jarzynski Equality

We describe some solvable models which illustrate the Jarzynski theorem and related fluctuation theorems. We consider a charged particle in the presence of magnetic field in a two dimensional harmonic well. In the first case the centre of the harmonic potential is translated with a uniform velocity, while in the other case the particle is subjected to an ac force. We show that Jarzynski identity complements Bohr-van Leeuwen theorem on the absence of diamagnetism in equilibrium classical system.Comment: 5 pages, minor corrections made and journal reference adde

Correlated errors in Hipparcos parallaxes towards the Pleiades and the Hyades

We show that the errors in the Hipparcos parallaxes towards the Pleiades and the Hyades open clusters are spatially correlated over angular scales of 2 to 3 deg, with an amplitude of up to 2 mas. This correlation is stronger than expected based on the analysis of the Hipparcos catalog. We predict the parallaxes of individual cluster members, pi_pm, from their Hipparcos proper motions, assuming that all cluster members have the same space velocity. We compare pi_pm with their Hipparcos parallaxes, pi_Hip, and find that there are significant spatial correlations in pi_Hip. We derive a distance modulus to the Pleiades of 5.58 +- 0.18 mag using the radial-velocity gradient method. This value, agrees very well with the distance modulus of 5.60 +- 0.04 mag determined using the main-sequence fitting technique, compared with the value of 5.33 +- 0.06 inferred from the average of the Hipparcos parallaxes of the Pleiades members. We show that the difference between the main-sequence fitting distance and the Hipparcos parallax distance can arise from spatially correlated errors in the Hipparcos parallaxes of individual Pleiades members. Although the Hipparcos parallax errors towards the Hyades are spatially correlated in a manner similar to those of the Pleiades, the center of the Hyades is located on a node of this spatial structure. Therefore, the parallax errors cancel out when the average distance is estimated, leading to a mean Hyades distance modulus that agrees with the pre-Hipparcos value. We speculate that these spatial correlations are also responsible for the discrepant distances that are inferred using the mean Hipparcos parallaxes to some open clusters. Finally, we note that our conclusions are based on a purely geometric method and do not rely on any models of stellar isochrones.Comment: 33 pages including 10 Figures, revised version accepted for publication in Ap

Violation of the `Zero-Force Theorem' in the time-dependent Krieger-Li-Iafrate approximation

We demonstrate that the time-dependent Krieger-Li-Iafrate approximation in combination with the exchange-only functional violates the `Zero-Force Theorem'. By analyzing the time-dependent dipole moment of Na5 and Na9+, we furthermore show that this can lead to an unphysical self-excitation of the system depending on the system properties and the excitation strength. Analytical aspects, especially the connection between the `Zero-Force Theorem' and the `Generalized-Translation Invariance' of the potential, are discussed.Comment: 5 pages, 4 figure

Conserving approximations in time-dependent quantum transport: Initial correlations and memory effects

We study time-dependent quantum transport in a correlated model system by means of time-propagation of the Kadanoff-Baym equations for the nonequilibrium many-body Green function. We consider an initially contacted equilibrium system of a correlated central region coupled to tight-binding leads. Subsequently a time-dependent bias is switched on after which we follow in detail the time-evolution of the system. Important features of the Kadanoff-Baym approach are 1) the possibility of studying the ultrafast dynamics of transients and other time-dependent regimes and 2) the inclusion of exchange and correlation effects in a conserving approximation scheme. We find that initial correlation and memory terms due to many-body interactions have a large effect on the transient currents. Furthermore the value of the steady state current is found to be strongly dependent on the approximation used to treat the electronic interactions.Comment: 5 pages, 2 figure