Physics

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New submissions for Mon, 24 Dec 07

[1]  arXiv:0712.3572 [pdf, other]

Title: A Quantitative Measure of Experimental Scientific Merit

Authors: Bruce Knuteson

Comments: 14 pages

Subjects: Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Physics and Society (physics.soc-ph)

Experimental program review in our field may benefit from a more quantitative framework within which to quantitatively discuss the scientific merit of a proposed program of research, and to assess the scientific merit of a particular experimental result. This article proposes explicitly such a quantitative framework. Examples of the use of this framework in assessing the scientific merit of particular avenues of research at the energy frontier in many cases provide results in stark contradiction to accepted wisdom. The experimental scientific figure of merit proposed here has the potential for informing future choices of research direction in our field, and in other subfields of the physical sciences.

[2]  arXiv:0712.3577 [ps, pdf, other]

Title: Extraction of the species dependent dipole moment from high-order harmonic spectra in rare gas atoms

Authors: Anh-Thu Le, Toru Morishita, C.D. Lin

Comments: 5 pages, 5 figures

Subjects: Atomic Physics (physics.atom-ph); Optics (physics.optics)

Based on high-order harmonic generation (HHG) spectra obtained from solving the time-dependent Schrodinger equation for atoms, we established quantitatively that the HHG yield can be expressed as the product of a returning electron wave packet and the photo-recombination cross sections, and the shape of the returning wave packet is shown to be largely independent of the species. By comparing the HHG spectra generated from different targets under identical laser pulses, accurate structural information, including the phase of the recombination amplitude, can be retrieved. This result opens up the possibility of studying the target structure of complex systems, including their time evolution, from the HHG spectra generated by short laser pulses.

[3]  arXiv:0712.3591 [ps, pdf, other]

Title: Droplet traffic in microfluidic networks: A simple model for understanding and designing

Authors: M. Schindler, A. Ajdari

Comments: accepted for publication in PRL

Subjects: Fluid Dynamics (physics.flu-dyn)

We propose a simple model to analyze the traffic of droplets in microfluidic ``dual networks''. Such functional networks which consist of two types of channels, namely those accessible or forbidden to droplets, often display a complex behavior characteristic of dynamical systems. By focusing on three recently proposed configurations, we offer an explanation for their remarkable behavior. Additionally, the model allows us to predict the behavior in different parameter regimes. A verification will clarify fundamental issues, such as the network symmetry, the role of the driving conditions, and of the occurrence of reversible behavior. The model lends itself to a fast numerical implementation, thus can help designing devices, identifying parameter windows where the behavior is sufficiently robust for a devices to be practically useful, and exploring new functionalities.

[4]  arXiv:0712.3592 [ps, pdf, other]

Title: Tunable-slip boundaries for coarse-grained simulations of fluid flow

Authors: Jens Smiatek, Mike P. Allen, Friederike Schmid

Comments: submitted to Eur. Phys. J. E

Subjects: Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn)

On the micro- and nanoscale, classical hydrodynamic boundary conditions such as the no-slip condition no longer apply. Instead, the flow profiles exhibit ``slip`` at the surface, which is characterized by a finite slip length (partial slip). We present a new, systematic way of implementing partial-slip boundary conditions with arbitrary slip length in coarse-grained computer simulations. The main idea is to represent the complex microscopic interface structure by a spatially varying effective viscous force. An analytical equation for the resulting slip length can be derived for planar and for curved surfaces. The comparison with computer simulations of a DPD (dissipative particle dynamics) fluid shows that this expression is valid from full-slip to no-slip.

[5]  arXiv:0712.3609 [ps, pdf, other]

Title: Postcorrection and mathematical model of life in Extended Everett's Concept

Authors: Michael B. Mensky

Comments: Comments: 24 pages, 1 figure, LATEX

Subjects: General Physics (physics.gen-ph)

Extended Everett's Concept (EEC) recently developed by the author to explain the phenomenon of consciousness is considered. A mathematical model is proposed for the principal feature of consciousness assumed in EEC, namely its ability (in the state of sleep, trance or meditation, when the explicit consciousness is disabled) to obtain information from all alternative classical realities (Everett's worlds) and select the favorable realities. To represent this ability, a mathematical operation called postcorrection is introduced, which corrects the present state to guarantee certain characteristics of the future state. Evolution of living matter is thus determined by goals (first of all by the goal of survival) as well as by causes. The resulting theory, in a way symmetrical in time direction, follows from a sort of antropic principle. Possible criteria for postcorrection and corresponding phenomena in the sphere of life are classified. Both individual and collective criteria of survival are considered as well as the criteria providing certain quality of life and those which are irrelevant to the life quality. The phenomena of free will and direct sighting of truth (e.g. scientific insight) are explained in these terms. The problem of artificial intellect and the role of brain look differently in the framework of this theory. Automats may perform intellectual operations, but not postcorrection, therefore artificial intellect but not an artificial life can be created. The brain serves as an interface between the body and consciousness, but the most profound level of consciousness is not a function of brain.

[6]  arXiv:0712.3611 [ps, pdf, other]

Title: Effects of diversification among assets in an agent-based market model

Authors: F. Ghoulmié, M. Bartolozzi, C.P. Mellen, T. Di Matteo

Comments: 12 pages, 5 figures, accepted for publication in the Proceedings of the Complex Systems II Conference at the Australian National University, 4-7 December 2007, Canberra, ACT Australia

Subjects: Data Analysis, Statistics and Probability (physics.data-an); Physics and Society (physics.soc-ph)

We extend to the multi-asset case the framework of a discrete time model of a single asset financial market developed in Ghoulmie et al (2005). In particular, we focus on adaptive agents with threshold behavior allocating their resources among two assets. We explore numerically the effect of this diversification as an additional source of complexity in the financial market and we discuss its destabilizing role. We also point out the relevance of these studies for financial decision making.

[7]  arXiv:0712.3621 [ps, pdf, other]

Title: Relativistic corrections to transition frequencies of Ag I, Dy I, Ho I, Yb II, Yb III, Au I and Hg II and search for variation of the fine structure constant

Authors: V. A. Dzuba, V. V. Flambaum

Comments: 6 pages, 5 tables

Subjects: Atomic Physics (physics.atom-ph)

Dependence of transition frequencies on the fine structure constant $\alpha=e^2/\hbar c$ is calculated for several many-electron systems which are used or planned to be used in the laboratory search for the time variation of the fine structure constant. In systems with a large number of electrons in open shells (from 11 to 15) the relative effects of the variation may be strongly enhanced. For the transitions which were considered before the results are in good agreement with previous calculations.

[8]  arXiv:0712.3636 [pdf]

Title: On the measurement by EDX of diffusion profiles of Ni/Cu assemblies

Authors: Olivier Arnould (LMT), François Hild (LMT)

Journal-ref: Microscopy and Analysis European Edition (2000) 13-15

Subjects: Classical Physics (physics.class-ph)

To characterise (inter)diffusion in materials, concentration profiles can be measured by EDX. It allows one to determine the chemical composition with a very good accuracy if measurement artefacts are accounted for. Standard phenomena (such as X-ray fluorescence) are usually corrected by commercial software. However, the effect of the pear-shaped volume of X-ray emission on the concentration profiles has to be considered. The paper describes the origin of this artefact, its consequences on measurements and will provide a practical solution (based on signal processing methods) to deconvolute the actual concentration profiles (or the diffusion coefficient) from the raw measurements.

[9]  arXiv:0712.3639 [ps, pdf, other]

Title: Excitation transfer and luminescence in porphyrin-carbon nanotube complexes

Authors: G. Magadur (LPQM, PPSM), Jean-Sébastien Lauret (LPQM), V. Alain-Rizzo (PPSM), C. Voisin (LPA), Ph. Roussignol (LPA), E. Deleporte (LPQM), J.A. Delaire (PPSM)

Subjects: Optics (physics.optics)

Functionalization of carbon nanotubes with hydrosoluble porphyrins (TPPS) is achieved by "$\pi$-stacking". The porphyrin/nanotube interaction is studied by means of optical absorption, photoluminescence and photoluminescence excitation spectroscopies. The main absorption line of the porphyrins adsorbed on nanotubes exhibits a 120 meV red shift, which we ascribe to a flattening of the molecule in order to optimize $\pi-\pi$ interactions. The porphyrin-nanotube complex shows a strong quenching of the TPPS emission while the photoluminescence intensity of the nanotubes is enhanced when the excitation laser is in resonance with the porphyrin absorption band. This reveals an efficient excitation transfer from the TPPS to the carbon nanotube.

[10]  arXiv:0712.3640 [ps, pdf, other]

Title: Zeeman effect of the hyperfine structure levels in lithiumlike ions

Authors: D.L. Moskovkin, V.M. Shabaev, W. Quint

Comments: 25 pages, 5 figures

Subjects: Atomic Physics (physics.atom-ph); Optics (physics.optics)

The fully relativistic theory of the Zeeman splitting of the $(1s)^2 2s$ hyperfine-structure levels in lithiumlike ions with $Z=6 - 32$ is considered for the magnetic field magnitude in the range from 1 to 10 T. The second-order corrections to the Breit -- Rabi formula are calculated and discussed including the one-electron contributions as well as the interelectronic-interaction effects of order 1/Z. The 1/Z corrections are evaluated within a rigorous QED approach. These corrections are combined with other interelectronic-interaction, QED, nuclear recoil, and nuclear size corrections to obtain high-precision theoretical values for the Zeeman splitting in Li-like ions with nonzero nuclear spin. The results can be used for a precise determination of nuclear magnetic moments from $g$-factor experiments.

[11]  arXiv:0712.3659 [ps, pdf, other]

Title: Quantum model for double ionization of atoms in strong laser fields

Authors: Jakub S. Prauzner-Bechcicki, Krzysztof Sacha, Bruno Eckhardt, Jakub Zakrzewski

Comments: 13 pages, 16 figures

Subjects: Atomic Physics (physics.atom-ph)

Double ionization of atoms in strong laser pulses is discussed by use of a simplified atomic model. Each electron is allowed to move along the lines indicated by the positions of the Stark saddles when the phase of the field changes. The effective two dimensional model resembles to a large extend the known 1+1 dimensional aligned electrons model, but enables correlated escape of electrons with equal momenta -- the phenomenon observed experimentally. The time-dependent solution of the Schrodinger equation allows us to discuss in detail the time dynamics of the ionization process, formation of electronic wavepackets and the development of the final momenta distribution. In particular, we are able to distinguish between sequential double ionization, where electrons escape during different half-cycles of the pulse, and non-sequential one, where they escape during the same half-cycle. We consider the dependence of the measurable quantities on the absolute phase of the light pulse.

[12]  arXiv:0712.3679 [ps, pdf, other]

Title: Negative refraction in (bi)-isotropic periodic arrangements of chiral SRRs

Authors: L.Jelinek, R.Marques, F.Mesa, J.D.Baena

Comments: Submmitted to Phys. Rev. Lett

Subjects: Optics (physics.optics)

Bi-isotropic and isotropic negative refractive index (NRI) 3D metamaterials made from periodic arrangements of chiral split ring resonators (SRRs) are proposed and demonstrated. An analytical theory for the characterization and design of these metamaterials is provided and validated by careful full-wave electromagnetic simulations. The reported results are expected to pave the way to the design of practical 3D bi-isotropic and isotropic NRI metamaterials made from a single kind of inclusions.

[13]  arXiv:0712.3710 [ps, pdf, other]

Title: Molecular Orbital Tomography using Short Laser Pulses

Authors: Elmar V. van der Zwan, Ciprian C. Chirilua, Manfred Lein

Comments: 5 pages, 2 figures

Subjects: Atomic Physics (physics.atom-ph)

Recently, a method to image molecular electronic wave functions using high harmonic generation (HHG) was introduced by Itatani \textit{et al.\} [Nature {\textbf{432}}, 876 (2004)]. We show that, while the tomographic reconstruction of general orbitals with arbitrary symmetry cannot be performed with long laser pulses, this becomes possible when extremely short pulses are used. An alternative reconstruction equation based on momentum matrix elements, rather than on dipole matrix elements, is proposed. We present simulations of the procedure for 2D model systems based on numerical solutions of the time-dependent Schr\"{o}dinger equation, and present results from further post-processing of the reconstructed orbitals.

[14]  arXiv:0712.3712 [pdf, other]

Title: Motion of Rydberg atoms induced by resonant dipole-dipole interactions

Authors: C. Ates, A. Eisfeld, J. M. Rost

Subjects: Atomic Physics (physics.atom-ph)

We show that nuclear motion of Rydberg atoms can be induced by resonant dipole-dipole interactions that trigger the energy transfer between two energetically close Rydberg states. How and if the atoms move depends on their initial arrangement as well as on the initial electronic excitation. Using a mixed quantum/classical propagation scheme we obtain the trajectories and kinetic energies of atoms, initially arranged in a regular chain and prepared in excitonic eigenstates. The influence of off-diagonal disorder on the motion of the atoms is examined and it is shown that irregularity in the arrangement of the atoms can lead to an acceleration of the nuclear dynamics.

[15]  arXiv:0712.3768 [ps, pdf, other]

Title: Emergence of Thermodynamics from Darwinian Dynamics

Authors: P Ao

Comments: latex, 8 pages

Subjects: General Physics (physics.gen-ph); Biological Physics (physics.bio-ph)

Darwinian dynamics is manifestly stochastic and nonconservative, but has a profound connection to conservative dynamics in physics. In the present paper the main ideas and logical steps leading to thermodynamics from Darwinian dynamics are discussed in a quantitative manner. A synthesis between nonequilibrum dynamics and conservative dynamics is outlined.

[16]  arXiv:0712.3776 [pdf]

Title: Controlling the Emission of Electromagnetic Sources by Coordinate transformation

Authors: Yu Luo, Jingjing Zhang, Lixin Ran, Hongsheng Chen, Jin Au Kong

Subjects: Optics (physics.optics); General Physics (physics.gen-ph)

The coordinate transformation on the space that contains electromagnetic sources is studied. We find that, not only the permittivity and permeability tensors of the media, but also the sources inside the media will take another form in order to behave equivalently as the original case. It is demonstrated that, a source of arbitrary shape and position in the free space can be replaced by an appropriately designed metamaterial coating with current distributed on the inner surface and would not be detected by outer observers, because the emission of the source can be controlled at will in this way. As examples, we show how to design conformal antennas by covering the sources with transformation media. The method proposed in this letter provides a completely new approach to develop novel active EM devices.

[17]  arXiv:0712.3793 [ps, pdf, other]

Title: On the Relationship between Thermodynamics and Special Relativity

Authors: C. A. Farías, P. S. Moya, V. A. Pinto

Comments: 7 pages, no figures

Subjects: Classical Physics (physics.class-ph)

Starting from a formulation for the $dS$ element that includes movement, and considering the variation of the entropy Lorentz invariant, we found the relativistic transformations for thermodynamic systems that satisfy the three laws of thermodynamics. Particularly, we found the temperature and pressure transformations, given by $T'=\gamma T$ and $p'=\gamma^2p$ respectively. Furthermore, we show that this transformations keeps the form of the state equation for an ideal gas in agreement with the relativity principle.

Cross-lists for Mon, 24 Dec 07

[18]  arXiv:0712.3310 (cross-list from cond-mat.other) [ps, pdf, other]

Title: Unidirectional rotary nanomotors powered by an electrochemical potential gradient

Authors: A. Yu. Smirnov, S. Savel'ev, L. G. Mourokh, Franco Nori

Subjects: Other (cond-mat.other); Biological Physics (physics.bio-ph); Subcellular Processes (q-bio.SC)

We examine the dynamics of biological nanomotors within a simple model of a rotor having three ion-binding sites. It is shown that in the presence of an external dc electric field in the plane of the rotor, the loading of the ion from the positive side of a membrane (rotor charging) provides a torque leading to the motor rotation. We derive equations for the proton populations of the sites and solve these equations numerically jointly with the Langevin-type equation for the rotor angle. Using parameters for biological systems, we demonstrate that the sequential loading and unloading of the sites lead to the unidirectional rotation of the motor. The previously unexplained phenomenon of fast direction-switching in the rotation of a bacterial flagellar motor can also be understood within our model.

[19]  arXiv:0712.3438 (cross-list from quant-ph) [ps, pdf, other]

Title: Consequences of Zeeman Degeneracy for van der Waals Blockade between Rydberg Atoms

Authors: Thad G. Walker, M. Saffman

Comments: 16 figures

Subjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)

We analyze the effects of Zeeman degeneracies on the long-range interactions between like Rydberg atoms, with particular emphasis on applications to quantum information processing using van der Waals blockade. We present a general analysis of how degeneracies affect the primary error sources in blockade experiments, emphasizing that blockade errors are sensitive primarily to the weakest possible atom-atom interactions between the degenerate states, not the mean interaction strength. We present explicit calculations of the van der Waals potentials in the limit where the fine-structure interaction is large compared to the atom-atom interactions. The results are presented for all potential angular momentum channels invoving s, p, and d states. For most channels there are one or more combinations of Zeeman levels that have extremely small dipole-dipole interactions and are therefore poor candidates for effective blockade experiments. Channels with promising properties are identified and discussed. We also present numerical calculations of Rb and Cs dipole matrix elements and relevant energy levels using quantum defect theory, allowing for convenient quantitative estimates of the van der Waals interactions to be made for principal quantum numbers up to 100. Finally, we combine the blockade and van der Waals results to quantitatively analyze the angular distribution of the blockade shift and its consequence for angular momentum channels and geometries of particular interest for blockade experiments with Rb.

[20]  arXiv:0712.3711 (cross-list from q-bio.MN) [ps, pdf, other]

Title: A computational systems biology study of the lambda-lac mutants

Authors: Maria Werner, Erik Aurell

Comments: 13 pages, 6 figures

Subjects: Molecular Networks (q-bio.MN); Biological Physics (physics.bio-ph)

We present a comprehensive computational study of some 900 possible "lambda-lac" mutants of the lysogeny maintenance switch in phage lambda, of which up to date 19 have been studied experimentally (Atsumi & Little, PNAS 103: 4558-4563, (2006)). We clarify that these mutants realise regulatory schemes quite different from wild-type lambda, and can therefore be expected to behave differently, within the conventional mechanistic setting in which this problem has often been framed. We verify that indeed, within this framework, across this wide selection of mutants the lambda-lac mutants for the most part either have no stable lytic states, or should only be inducible with difficulty. In particular, the computational results contradicts the experimental finding that four lambda-lac mutants both show stable lysogeny and are inducible. This work hence suggests either that the four out of 900 mutants are special, or that lambda lysogeny and inducibility are holistic effects involving other molecular players or other mechanisms, or both. The approach illustrates the power and versatility of computational systems biology to systematically and quickly test a wide variety of examples and alternative hypotheses for future closer experimental studies.

Replacements for Mon, 24 Dec 07

[21]  arXiv:math/0603155 (replaced) [ps, pdf, other]

Title: Vers une commande multivariable sans modèle

Authors: Michel Fliess (INRIA Futurs, LIX), Cédric Join (INRIA Futurs, CRAN), Mamadou Mboup (INRIA Futurs), Hebertt Sira-Ramirez

Journal-ref: Dans Conf\'erence internationale francophone d'automatique (CIFA 2006) (2006)

Subjects: Optimization and Control (math.OC); Computational Engineering, Finance, and Science (cs.CE); Robotics (cs.RO); Classical Physics (physics.class-ph)

[22]  arXiv:0709.2984 (replaced) [ps, pdf, other]

Title: Precise dipole moment and quadrupole coupling constants of benzonitrile

Authors: Kirstin Wohlfart, Melanie Schnell, Jens-Uwe Grabow, Jochen Küpper

Comments: 6 pages, 2 tables (elsart)

Journal-ref: J. Mol. Spec. 247(1), 119-121 (2008)

Subjects: Chemical Physics (physics.chem-ph)

[23]  arXiv:0712.3174 (replaced) [ps, pdf, other]

Title: Application of afxy-code for parameterization of ionization yield function Y in the atmosphere for primary cosmic ray protons

Authors: L. Alexandrov, A. Mishev

Comments: 14 pages, 9 figures

Subjects: Space Physics (physics.space-ph); Atmospheric and Oceanic Physics (physics.ao-ph)

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