Showing papers in "Lecture Notes in Physics in 2006"

Astrophysical axion bounds

Abstract: Axion emission by hot and dense plasmas is a new energy-loss channel for stars. Observable consequences include a modification of the solar sound-speed profile, an increase of the solar neutrino flux, a reduction of the helium-burning lifetime of globular-cluster stars, accelerated white-dwarf cooling, and a reduction of the supernova SN 1987A neutrino burst duration. I review and update these arguments and summarize the resulting axion constraints.

Introduction to the Functional RG and Applications to Gauge Theories

Abstract: This lecture course is intended to fill the gap between graduate courses on quantum field theory and specialized reviews or forefront-research articles on functional renormalization group approaches to quantum field theory and gauge theories.

The Strong CP Problem and Axions

Abstract: I describe how the QCD vacuum structure, necessary to resolve the U(1)_A problem, predicts the presence of a PabbrevPparity transformation, TabbrevTtime reversal transformation, and CPabbrevCPcharge conjugation transformation followed by party transformation violating term proportional to the vacuum angle θ. To agree with experimental bounds, however, this parameter must be very small (θ < 10-9). After briefly discussing some other possible solutions to this, so-called, strong CP problem, I concentrate on the chiral solution proposed by Peccei and Quinn which has associated with it a light pseudoscalar particle, the axion. I discuss in detail the properties and dynamics of axions, focusing particularly on invisible axion models where axions are very light, very weakly coupled, and very long-lived. Astrophysical and cosmological bounds on invisible axions are also briefly touched upon.

CMOL: Devices, Circuits, and Architectures

Abstract: This chapter is a brief review of the recent work on various aspects of the prospective hybrid semiconductor/nanowire/molecular ("CMOL") integrated circuits. The basic idea of such circuits is to combine the advantages ofthe currently dominating CMOS technology (including its flexibility and high fabrication yield) with those of molecular devices with nanometer-scale footprint. Two-terminal molecular devices would be self-assembled on a pre-fabricated nanowire crossbar fabric, enabling very high function density at acceptable fabrication costs. Preliminary estimates show that the density of active devices in CMOL circuits may be as high as 10 1 2 cm - 2 and that they may provide an unparalleled information processing performance, up to 10 2 0 operations per cm 2 per second, at manageable power consumption. However, CMOL technology imposes substantial requirements (most importantly, that of high defect tolerance) on circuit architectures. In the view of these restrictions, the most straightforward application of CMOL circuits is terabitscale memories, in which powerful bad-bit-exclusion and error-correction techniques may be used to boost the defect tolerance. The implementation of Boolean logic circuits is more problematic, though our preliminary results for reconfigurable, uniform FPGA-like CMOL circuits look very encouraging. Finally, CMOL technology seems to be uniquely suitable for the implementation of the "CrossNet" family of neuromorphic networks for advanced information processing including, at least, pattern recognition and classification, and quite possibly much more intelligent tasks. We believe that these application prospects justify a large-scale research and development effort focused on the main challenge of the field, the high-yield self-assembly of molecular devices.

The Fueling and Evolution of AGN: Internal and External Triggers

Abstract: In this chapter, I review the fueling and evolution of active galactic nuclei (AGN) under the influence of internal and external triggers, namely intrinsic properties of host galaxies (morphological or Hubble type, color, presence of bars and other non-axisymmetric features, etc) and external factors such as environment and interactions. The most daunting challenge in fueling AGN is arguably the angular momentum problem as even matter located at a radius of a few hundred pc must lose more than 99.99 % of its specific angular momentum before it is fit for consumption by a BH. I review mass accretion rates, angular momentum requirements, the effectiveness of different fueling mechanisms, and the growth and mass density of black BHs at different epochs. I discuss connections between the nuclear and larger-scale properties of AGN, both locally and at intermediate redshifts, outlining some recent results from the GEMS and GOODS HST surveys.

Transition Path Theory

Abstract: An overview of the theory for analyzing the statistical properties of the reactive trajectories by which transitions occur between a set of initial and final states in a Markov model, and thereby obtain e.g. the highest flux pathways between these states.

Introduction to representations of the canonical commutation and anticommutation relations

Abstract: Lecture notes of a minicourse given at the Summer School on Large Coulomb Systems - QED in Nordfjordeid, 2003, devoted to representations of the CCR and CAR. Quasifree states, the Araki-Woods and Araki-Wyss representations, and the lattice of von Neumenn algebras in a bosonic/fermionic Fock space are discussed in detail.

Extensions of Fibre Bundle Models

Abstract: The fibre bundle model is one of the most important theoretical approaches to investigate the fracture and breakdown of disordered media extensively used both by the engineering and physics community. We present the basic construction of the model and provide a brief overview of recent results focusing mainly on the physics literature. We discuss the limitations of the model to describe the failure of composite materials and present recent extensions of the model which overcome these problems making the model more realistic: we gradually enhance the fibre bundle model by generalizing the failure law, constitutive behavior, deformation state and way of interaction of fibres. We show that beyond the understanding of the fracture of fibre reinforced composites, these extensions of the fibre bundle model also address interesting problems for the statistical physics of fracture.

Isotope Separation On Line and Post Acceleration

Abstract: In this Lecture the production of radioactive isotopes using the isotope separator on line (ISOL) method is discussed. General properties of the method, the different production and ionization mechanisms are presented and the way these are implemented in the target-ion source systems are highlighted. Mass separation and post acceleration together with an overview of the different facilities are included.

The Broad-Line Region in Active Galactic Nuclei

Abstract: We review the basic observed and inferred properties of the broad emission-line region in AGNs, as well as the basics of the reverberation-mapping technique that can be used to determine the size and structure of the region We argue that the current best evidence points to a multi-component line-emitting re- gion, with a disk-like structure, possibly an extension of the accretion disk itself, and a disk wind being strong candidates for the origin of the broad-line emission Some 40 years after the discovery of quasars and 60 years after the publication of CK Seyfert's initial observations of high central surface brightness galax- ies, we are finally quite certain that active galactic nuclei (AGNs) are powered by accretion onto supermassive collapsed objects While many important de- tails remain poorly understood, the black-hole/accretion-disk paradigm is now reasonably secure In contrast, however, we still have no self-consistent models of the nuclear regions that produce (a) the broad emission lines that are so prominent in the UV/optical spectra of AGNs and (b) the strong ab- sorption features seen in the X-ray/UV spectra Given the proximity of these regions to the central engine, it seems likely that these are some manifes- tation of the accretion process and related outflow; there is a good deal of empirical evidence that connects these spectral features to disk-related out- flows Unfortunately, solid information about the broad-line region (BLR) is hard to come by: the BLR is spatially unresolved in even the nearest AGNs and the information in line profiles, sampling only one of six dimensions in phase space, is highly ambiguous In this review, we will concentrate on a few things that we can infer about the nature of the BLR, and reverberation mapping, arguably the most promising technique for exploring the nature of the BLR The scope of this review is limited to a few basic topics and represents, of course, the author's own highly biased personal view

Hitchhiker's guide to multiplet calculations

Abstract: Core level spectra from localized magnetic systems, such as 3d transition metal compounds or rare earths, obtained with high resolution synchrotron radiation can be simulated theoretically by calculating the transitions from the ground state to the allowed final states, e.g. 3d" → 2p 5 3d n+1 . Presented here is the angular momentum coupling theory, Racah-Wigner algebra, point group theory and multipole moment expansion behind such calculations for the dichroic spectra of x-ray absorption, photoemission and x-ray resonant magnetic scattering. The first part of this chapter reviews the standard results of multiplet theory and surveys the Cowan-Butler-Thole approach. The last part presents some more advanced topics, such as the x-ray optical activity, which is induced by interference between different electric and magnetic multipole fields, and the method of statistical moment analysis, which relates the moment distribution of the dichroic spectra to effective operators.'

Poisson Statistics for the Largest Eigenvalues in Random Matrix Ensembles

Abstract: Author(s): Soshnikov, Alexander | Abstract: The paper studies the spectral properties of large Wigner, band and sample covariance random matrices with heavy tails of the marginal distributions of matrix entries

The Space of Null Geodesics (and a New Causal Boundary)

Abstract: The space of null geodesics, G, of a space-time, M, carries information on various aspects of the causal structure M. In this contribution, we will review the space of null geodesics, G, and some natural structures which it carries, and see how aspects of the causal structure of M are encoded there. If M is strongly causal, then G has a natural contact manifold structure, points are represented in G by smooth Legendrian S 2 s, and the relationships between these S 2 s reflect causal relationships between the points of M. One can also attempt to pass in the opposite direction with the intention of constructing a space-time from a family of S 2 si nG; this process suggests a means of attaching end-points to null geodesics of M, and thereby constructing a causal boundary. We close by summarizing some open questions in this general area.

Magnetism : a synchrotron radiation approach

Abstract: to Magnetism- X-ray and Electron Spectroscopies: An Introduction- Synchrotron Radiation- X-ray Magnetic Circular Dichroism: Historical Perspective and Recent Highlights- Spin-Polarized Photoemission- Band-Structure Theory of Dichroism- Hitchhiker's Guide to Multiplet Calculations- Resonant X-ray Scattering: A Theoretical Introduction- High Angle Magnetic X-ray Diffraction- Magnetic Imaging- Dynamic Aspects of Magnetism- Molecular Magnetism- Magnetism under Pressure with Synchrotron Radiation- X-ray Spectroscopy and Magnetism in Mineralogy- Materials for Spintronics

Mathematical Theory of the Wigner-Weisskopf Atom

Abstract: These notes provide an introduction to the spectral theory of the Friedrichs model. This model is used in quantum physics to describe the coupling of a discrete set of energy levels to a continuum of states. We restrict ourselves to the simplest possible case of a single energy level coupled to a continuum, the so-called Wigner-Weisskopf atom. We discuss both, perturbative and non-perturbative aspects. We also consider the fermionic second quantization of this model and discuss its nonequilibrium thermodynamics: steady states, steady currents and entropy production.

Multiwavelength Evidence of the Physical Processes in Radio Jets

Abstract: Over the last few years, high-quality X-ray imaging and spectroscopic data from Chandra and XMM-Newton have added greatly to the understanding of the physics of radio jets, Here we describe the current state of knowledge with an emphasis on the underlying physics used to interpret multiwavelength data in terms of physical parameters.

Ab-initio Non-Equilibrium Green’s Function Formalism for Calculating Electron Transport in Molecular Devices

Abstract: The purpose of this chapter is to give a general reader an introduction to the Non Equilibrium Greens Function (NEGF) method for first principles modeling of current-voltage characteristics of molecular electronics devices The molecular device is modeled on the atomic level, and we will use Density Functional Theory (DFT) to describe the electronic structure of the system We will give a detailed description of all the steps involved in order to calculate the electron current The steps involved are dividing the system into electrode and scattering region, determining the one-electron DFT Hamiltonian, setting up the NEGF, determining the charge density, and calculating the effective potential The procedure sets up a set of selfconsistent equations, which result in an effective one-electron Hamiltonian description of the electron motion From the one-electron Hamiltonian we can determine the electron current using the Landauer-Biittiker approach We present results obtained with the method for calculating the conductance of molecular resistors, and we will show that there are excellent agreement with recent experimental results The non-equilibrium current will induce an additional force on the atoms We investigate the origin of this force and present a simple model which relates the force to the charge rearrangement around the atoms in the scattering region

Synthesis Methods and Growth Mechanisms

Abstract: In this chapter, our purpose is to present how carbon nanotubes are synthesized and how their formation and growth can be studied, understood and modeled. We give an overview of the different synthesis methods, which can be classi fied into two main categories according to the synthesis temperature. We include a review of the CVD synthesis of carbon filaments, as an introduction to that of nanotubes.

X-ray Magnetic Circular Dichroism: Historical Perspective and Recent Highlights

Abstract: This chapter starts with a brief historical overview which shows how x- ray Magnetic Circular Dichroism (XMCD) has evolved from the very early days of x- ray physics to become a powerful spectroscopic technique with the derivation of the x-ray magneto-optical sum rules. We analyze the physical content of XMCD and its sum rules. It is the unique capability of XMCD to probe with elemental selectivity the magnetic properties of an electronic state of given symmetry which makes this method an outstanding tool to study magnetism. We decided to highlight two recent advances in XMCD: the first one deals with measurements of tiny magnetic moments induced either by a magnetic field in a Pauli paramagnet (Pd metal) or by hybridization with a transition metal; the second example concerns induced magnetism in ferromagnetic 3d/5d multilayers.

Transition Path Sampling Methods

Abstract: C. Dellago, P.G. Bolhuis, and P.L. Geissler 1 Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Wien, Austria Christoph.Dellago@univie.ac.at 2 van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands bolhuis@science.uva.nl 3 Department of Chemistry, University of California at Berkeley, 94720 Berkeley, CA, USA geissler@cchem.berkeley.edu

Dynamics of Disordered Elastic Systems

Abstract: In these notes we present a brief review of the dynamical properties of interfaces in a disordered environment. We focus in particular on the response of such systems to a very small external force, and the corresponding very slow motion it entails, so called creep. We discuss various general theoretical aspects of this problem and consider in detail the case of a one dimensional interface (domain wall).